Semi-Supervised Learning of Lift Optimization of Multi-Element Three-Segment Variable Camber Airfoil

NASA Technical Reports Server (NTRS)

Kaul, Upender K.; Nguyen, Nhan T.

2017-01-01

This chapter describes a new intelligent platform for learning optimal designs of morphing wings based on Variable Camber Continuous Trailing Edge Flaps (VCCTEF) in conjunction with a leading edge flap called the Variable Camber Krueger (VCK). The new platform consists of a Computational Fluid Dynamics (CFD) methodology coupled with a semi-supervised learning methodology. The CFD component of the intelligent platform comprises of a full Navier-Stokes solution capability (NASA OVERFLOW solver with Spalart-Allmaras turbulence model) that computes flow over a tri-element inboard NASA Generic Transport Model (GTM) wing section. Various VCCTEF/VCK settings and configurations were considered to explore optimal design for high-lift flight during take-off and landing. To determine globally optimal design of such a system, an extremely large set of CFD simulations is needed. This is not feasible to achieve in practice. To alleviate this problem, a recourse was taken to a semi-supervised learning (SSL) methodology, which is based on manifold regularization techniques. A reasonable space of CFD solutions was populated and then the SSL methodology was used to fit this manifold in its entirety, including the gaps in the manifold where there were no CFD solutions available. The SSL methodology in conjunction with an elastodynamic solver (FiDDLE) was demonstrated in an earlier study involving structural health monitoring. These CFD-SSL methodologies define the new intelligent platform that forms the basis for our search for optimal design of wings. Although the present platform can be used in various other design and operational problems in engineering, this chapter focuses on the high-lift study of the VCK-VCCTEF system. Top few candidate design configurations were identified by solving the CFD problem in a small subset of the design space. The SSL component was trained on the design space, and was then used in a predictive mode to populate a selected set of test points outside of the given design space. The new design test space thus populated was evaluated by using the CFD component by determining the error between the SSL predictions and the true (CFD) solutions, which was found to be small. This demonstrates the proposed CFD-SSL methodologies for isolating the best design of the VCK-VCCTEF system, and it holds promise for quantitatively identifying best designs of flight systems, in general.

Overview of hypersonic CFD code calibration studies

NASA Technical Reports Server (NTRS)

Miller, Charles G.

1987-01-01

The topics are presented in viewgraph form and include the following: definitions of computational fluid dynamics (CFD) code validation; climate in hypersonics and LaRC when first 'designed' CFD code calibration studied was initiated; methodology from the experimentalist's perspective; hypersonic facilities; measurement techniques; and CFD code calibration studies.

Review of computational fluid dynamics (CFD) researches on nano fluid flow through micro channel

NASA Astrophysics Data System (ADS)

Dewangan, Satish Kumar

2018-05-01

Nanofluid is becoming a promising heat transfer fluids due to its improved thermo-physical properties and heat transfer performance. Micro channel heat transfer has potential application in the cooling high power density microchips in CPU system, micro power systems and many such miniature thermal systems which need advanced cooling capacity. Use of nanofluids enhances the effectiveness of t=scu systems. Computational Fluid Dynamics (CFD) is a very powerful tool in computational analysis of the various physical processes. It application to the situations of flow and heat transfer analysis of the nano fluids is catching up very fast. Present research paper gives a brief account of the methodology of the CFD and also summarizes its application on nano fluid and heat transfer for microchannel cases.

A 3D-CFD code for accurate prediction of fluid flows and fluid forces in seals

NASA Technical Reports Server (NTRS)

Athavale, M. M.; Przekwas, A. J.; Hendricks, R. C.

1994-01-01

Current and future turbomachinery requires advanced seal configurations to control leakage, inhibit mixing of incompatible fluids and to control the rotodynamic response. In recognition of a deficiency in the existing predictive methodology for seals, a seven year effort was established in 1990 by NASA's Office of Aeronautics Exploration and Technology, under the Earth-to-Orbit Propulsion program, to develop validated Computational Fluid Dynamics (CFD) concepts, codes and analyses for seals. The effort will provide NASA and the U.S. Aerospace Industry with advanced CFD scientific codes and industrial codes for analyzing and designing turbomachinery seals. An advanced 3D CFD cylindrical seal code has been developed, incorporating state-of-the-art computational methodology for flow analysis in straight, tapered and stepped seals. Relevant computational features of the code include: stationary/rotating coordinates, cylindrical and general Body Fitted Coordinates (BFC) systems, high order differencing schemes, colocated variable arrangement, advanced turbulence models, incompressible/compressible flows, and moving grids. This paper presents the current status of code development, code demonstration for predicting rotordynamic coefficients, numerical parametric study of entrance loss coefficients for generic annular seals, and plans for code extensions to labyrinth, damping, and other seal configurations.

Reduced order model based on principal component analysis for process simulation and optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lang, Y.; Malacina, A.; Biegler, L.

2009-01-01

It is well-known that distributed parameter computational fluid dynamics (CFD) models provide more accurate results than conventional, lumped-parameter unit operation models used in process simulation. Consequently, the use of CFD models in process/equipment co-simulation offers the potential to optimize overall plant performance with respect to complex thermal and fluid flow phenomena. Because solving CFD models is time-consuming compared to the overall process simulation, we consider the development of fast reduced order models (ROMs) based on CFD results to closely approximate the high-fidelity equipment models in the co-simulation. By considering process equipment items with complicated geometries and detailed thermodynamic property models,more » this study proposes a strategy to develop ROMs based on principal component analysis (PCA). Taking advantage of commercial process simulation and CFD software (for example, Aspen Plus and FLUENT), we are able to develop systematic CFD-based ROMs for equipment models in an efficient manner. In particular, we show that the validity of the ROM is more robust within well-sampled input domain and the CPU time is significantly reduced. Typically, it takes at most several CPU seconds to evaluate the ROM compared to several CPU hours or more to solve the CFD model. Two case studies, involving two power plant equipment examples, are described and demonstrate the benefits of using our proposed ROM methodology for process simulation and optimization.« less

Observations on computational methodologies for use in large-scale, gradient-based, multidisciplinary design incorporating advanced CFD codes

NASA Technical Reports Server (NTRS)

Newman, P. A.; Hou, G. J.-W.; Jones, H. E.; Taylor, A. C., III; Korivi, V. M.

1992-01-01

How a combination of various computational methodologies could reduce the enormous computational costs envisioned in using advanced CFD codes in gradient based optimized multidisciplinary design (MdD) procedures is briefly outlined. Implications of these MdD requirements upon advanced CFD codes are somewhat different than those imposed by a single discipline design. A means for satisfying these MdD requirements for gradient information is presented which appear to permit: (1) some leeway in the CFD solution algorithms which can be used; (2) an extension to 3-D problems; and (3) straightforward use of other computational methodologies. Many of these observations have previously been discussed as possibilities for doing parts of the problem more efficiently; the contribution here is observing how they fit together in a mutually beneficial way.

CFD Analysis of the SBXC Glider Airframe

DTIC Science & Technology

2016-06-01

mathematically on finite element methods. To validate and verify the methodology developed, a mathematical comparison was made with the previous research data...greater than 15 m/s. 14. SUBJECT TERMS finite element method, computational fluid dynamics, Y Plus, mesh element quality, aerodynamic data, fluid...based mathematically on finite element methods. To validate and verify the methodology developed, a mathematical comparison was made with the

Rocket-Based Combined Cycle Engine Technology Development: Inlet CFD Validation and Application

NASA Technical Reports Server (NTRS)

DeBonis, J. R.; Yungster, S.

1996-01-01

A CFD methodology has been developed for inlet analyses of Rocket-Based Combined Cycle (RBCC) Engines. A full Navier-Stokes analysis code, NPARC, was used in conjunction with pre- and post-processing tools to obtain a complete description of the flow field and integrated inlet performance. This methodology was developed and validated using results from a subscale test of the inlet to a RBCC 'Strut-Jet' engine performed in the NASA Lewis 1 x 1 ft. supersonic wind tunnel. Results obtained from this study include analyses at flight Mach numbers of 5 and 6 for super-critical operating conditions. These results showed excellent agreement with experimental data. The analysis tools were also used to obtain pre-test performance and operability predictions for the RBCC demonstrator engine planned for testing in the NASA Lewis Hypersonic Test Facility. This analysis calculated the baseline fuel-off internal force of the engine which is needed to determine the net thrust with fuel on.

Computational Fluid Dynamics (CFD) Analysis for the Reduction of Impeller Discharge Flow Distortion

NASA Technical Reports Server (NTRS)

Garcia, R.; McConnaughey, P. K.; Eastland, A.

1993-01-01

The use of Computational Fluid Dynamics (CFD) in the design and analysis of high performance rocket engine pumps has increased in recent years. This increase has been aided by the activities of the Marshall Space Flight Center (MSFC) Pump Stage Technology Team (PSTT). The team's goals include assessing the accuracy and efficiency of several methodologies and then applying the appropriate methodology(s) to understand and improve the flow inside a pump. The PSTT's objectives, team membership, and past activities are discussed in Garcia1 and Garcia2. The PSTT is one of three teams that form the NASA/MSFC CFD Consortium for Applications in Propulsion Technology (McConnaughey3). The PSTT first applied CFD in the design of the baseline consortium impeller. This impeller was designed for the Space Transportation Main Engine's (STME) fuel turbopump. The STME fuel pump was designed with three impeller stages because a two-stage design was deemed to pose a high developmental risk. The PSTT used CFD to design an impeller whose performance allowed for a two-stage STME fuel pump design. The availability of this design would have lead to a reduction in parts, weight, and cost had the STME reached production. One sample of the baseline consortium impeller was manufactured and tested in a water rig. The test data showed that the impeller performance was as predicted and that a two-stage design for the STME fuel pump was possible with minimal risk. The test data also verified another CFD predicted characteristic of the design that was not desirable. The classical 'jet-wake' pattern at the impeller discharge was strengthened by two aspects of the design: by the high head coefficient necessary for the required pressure rise and by the relatively few impeller exit blades, 12, necessary to reduce manufacturing cost. This 'jet-wake pattern produces an unsteady loading on the diffuser vanes and has, in past rocket engine programs, lead to diffuser structural failure. In industrial applications, this problem is typically avoided by increasing the space between the impeller and the diffuser to allow the dissipation of this pattern and, hence, the reduction of diffuser vane unsteady loading. This approach leads to small performance losses and, more importantly in rocket engine applications, to significant increases in the pump's size and weight. This latter consideration typically makes this approach unacceptable in high performance rocket engines.

Application of CFD in Indonesian Research: A review

NASA Astrophysics Data System (ADS)

Ambarita, H.; Siregar, M. R.; Kishinami, K.; Daimaruya, M.; Kawai, H.

2018-04-01

Computational Fluid Dynamics (CFD) is a numerical method that solves fluid flow and related governing equations using a computational tool. The studies on CFD, its methodology and its application as a research tool, are increasing. In this study, application of CFD by Indonesian researcher is briefly reviewed. The main objective is to explore the characteristics of CFD applications in Indonesian researchers. Considering the size and reputation, this study uses Scopus publications indexed data base. All of the documents in Scopus related to CFD which is affiliated by at least one of Indonesian researcher are collected to be reviewed. Research topics, CFD method, and simulation results are reviewed in brief. The results show that there are 260 documents found in literature indexed by Scopus. These documents divided into research articles 125 titles, conference paper 135 titles, book 1 title and review 1 title. In the research articles, only limited researchers focused on the development of CFD methodology. Almost all of the articles focus on using CFD in a particular application, as a research tool, such as aircraft application, wind power and heat exchanger. The topics of the 125 research articles can be divided into 12 specific applications and 1 miscellaneous application. The most popular application is Heating Ventilating and Air Conditioning and followed by Reactor, Transportation and Heat Exchanger applications. The most popular commercial CFD code used is ANSYS Fluent and only several researchers use CFX.

Integrated detoxification methodology of hazardous phenolic wastewaters in environmentally based trickle-bed reactors: Experimental investigation and CFD simulation.

PubMed

Lopes, Rodrigo J G; Almeida, Teresa S A; Quinta-Ferreira, Rosa M

2011-05-15

Centralized environmental regulations require the use of efficient detoxification technologies for the secure disposal of hazardous wastewaters. Guided by federal directives, existing plants need reengineering activities and careful analysis to improve their overall effectiveness and to become environmentally friendly. Here, we illustrate the application of an integrated methodology which encompasses the experimental investigation of catalytic wet air oxidation and CFD simulation of trickle-bed reactors. As long as trickle-bed reactors are determined by the flow environment coupled with chemical kinetics, first, on the optimization of prominent numerical solution parameters, the CFD model was validated with experimental data taken from a trickle bed pilot plant specifically designed for the catalytic wet oxidation of phenolic wastewaters. Second, several experimental and computational runs were carried out under unsteady-state operation to evaluate the dynamic performance addressing the TOC concentration and temperature profiles. CFD computations of total organic carbon conversion were found to agree better with experimental data at lower temperatures. Finally, the comparison of test data with simulation results demonstrated that this integrated framework was able to describe the mineralization of organic matter in trickle beds and the validated consequence model can be exploited to promote cleaner remediation technologies of contaminated waters. Copyright © 2011 Elsevier B.V. All rights reserved.

A supportive architecture for CFD-based design optimisation

NASA Astrophysics Data System (ADS)

Li, Ni; Su, Zeya; Bi, Zhuming; Tian, Chao; Ren, Zhiming; Gong, Guanghong

2014-03-01

Multi-disciplinary design optimisation (MDO) is one of critical methodologies to the implementation of enterprise systems (ES). MDO requiring the analysis of fluid dynamics raises a special challenge due to its extremely intensive computation. The rapid development of computational fluid dynamic (CFD) technique has caused a rise of its applications in various fields. Especially for the exterior designs of vehicles, CFD has become one of the three main design tools comparable to analytical approaches and wind tunnel experiments. CFD-based design optimisation is an effective way to achieve the desired performance under the given constraints. However, due to the complexity of CFD, integrating with CFD analysis in an intelligent optimisation algorithm is not straightforward. It is a challenge to solve a CFD-based design problem, which is usually with high dimensions, and multiple objectives and constraints. It is desirable to have an integrated architecture for CFD-based design optimisation. However, our review on existing works has found that very few researchers have studied on the assistive tools to facilitate CFD-based design optimisation. In the paper, a multi-layer architecture and a general procedure are proposed to integrate different CFD toolsets with intelligent optimisation algorithms, parallel computing technique and other techniques for efficient computation. In the proposed architecture, the integration is performed either at the code level or data level to fully utilise the capabilities of different assistive tools. Two intelligent algorithms are developed and embedded with parallel computing. These algorithms, together with the supportive architecture, lay a solid foundation for various applications of CFD-based design optimisation. To illustrate the effectiveness of the proposed architecture and algorithms, the case studies on aerodynamic shape design of a hypersonic cruising vehicle are provided, and the result has shown that the proposed architecture and developed algorithms have performed successfully and efficiently in dealing with the design optimisation with over 200 design variables.

Evaluation of CFD Methods for Simulation of Two-Phase Boiling Flow Phenomena in a Helical Coil Steam Generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pointer, William David; Shaver, Dillon; Liu, Yang

The U.S. Department of Energy, Office of Nuclear Energy charges participants in the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program with the development of advanced modeling and simulation capabilities that can be used to address design, performance and safety challenges in the development and deployment of advanced reactor technology. The NEAMS has established a high impact problem (HIP) team to demonstrate the applicability of these tools to identification and mitigation of sources of steam generator flow induced vibration (SGFIV). The SGFIV HIP team is working to evaluate vibration sources in an advanced helical coil steam generator using computational fluidmore » dynamics (CFD) simulations of the turbulent primary coolant flow over the outside of the tubes and CFD simulations of the turbulent multiphase boiling secondary coolant flow inside the tubes integrated with high resolution finite element method assessments of the tubes and their associated structural supports. This report summarizes the demonstration of a methodology for the multiphase boiling flow analysis inside the helical coil steam generator tube. A helical coil steam generator configuration has been defined based on the experiments completed by Polytecnico di Milano in the SIET helical coil steam generator tube facility. Simulations of the defined problem have been completed using the Eulerian-Eulerian multi-fluid modeling capabilities of the commercial CFD code STAR-CCM+. Simulations suggest that the two phases will quickly stratify in the slightly inclined pipe of the helical coil steam generator. These results have been successfully benchmarked against both empirical correlations for pressure drop and simulations using an alternate CFD methodology, the dispersed phase mixture modeling capabilities of the open source CFD code Nek5000.« less

Aerothermal Ground Testing of Flexible Thermal Protection Systems for Hypersonic Inflatable Aerodynamic Decelerators

NASA Technical Reports Server (NTRS)

Bruce, Walter E., III; Mesick, Nathaniel J.; Ferlemann, Paul G.; Siemers, Paul M., III; DelCorso, Joseph A.; Hughes, Stephen J.; Tobin, Steven A.; Kardell, Matthew P.

2012-01-01

Flexible TPS development involves ground testing and analysis necessary to characterize performance of the FTPS candidates prior to flight testing. This paper provides an overview of the analysis and ground testing efforts performed over the last year at the NASA Langley Research Center and in the Boeing Large-Core Arc Tunnel (LCAT). In the LCAT test series, material layups were subjected to aerothermal loads commensurate with peak re-entry conditions enveloping a range of HIAD mission trajectories. The FTPS layups were tested over a heat flux range from 20 to 50 W/cm with associated surface pressures of 3 to 8 kPa. To support the testing effort a significant redesign of the existing shear (wedge) model holder from previous testing efforts was undertaken to develop a new test technique for supporting and evaluating the FTPS in the high-temperature, arc jet flow. Since the FTPS test samples typically experience a geometry change during testing, computational fluid dynamic (CFD) models of the arc jet flow field and test model were developed to support the testing effort. The CFD results were used to help determine the test conditions experienced by the test samples as the surface geometry changes. This paper includes an overview of the Boeing LCAT facility, the general approach for testing FTPS, CFD analysis methodology and results, model holder design and test methodology, and selected thermal results of several FTPS layups.

CFD applications: The Lockheed perspective

NASA Technical Reports Server (NTRS)

Miranda, Luis R.

1987-01-01

The Numerical Aerodynamic Simulator (NAS) epitomizes the coming of age of supercomputing and opens exciting horizons in the world of numerical simulation. An overview of supercomputing at Lockheed Corporation in the area of Computational Fluid Dynamics (CFD) is presented. This overview will focus on developments and applications of CFD as an aircraft design tool and will attempt to present an assessment, withing this context, of the state-of-the-art in CFD methodology.

Verification of transport equations in a general purpose commercial CFD code.

NASA Astrophysics Data System (ADS)

Melot, Matthieu; Nennemann, Bernd; Deschênes, Claire

2016-11-01

In this paper, the Verification and Validation methodology is presented. This method aims to increase the reliability and the trust that can be placed into complex CFD simulations. The first step of this methodology, the code verification is presented in greater details. The CFD transport equations in steady state, transient and Arbitrary Eulerian Lagrangian (ALE, used for transient moving mesh) formulations in Ansys CFX are verified. It is shown that the expected spatial and temporal order of convergence are achieved for the steady state and the transient formulations. Unfortunately this is not completely the case for the ALE formulation. As for a lot of other commercial and in-house CFD codes, the temporal convergence of the velocity is limited to a first order where a second order would have been expected.

Advanced Methodology for Simulation of Complex Flows Using Structured Grid Systems

NASA Technical Reports Server (NTRS)

Steinthorsson, Erlendur; Modiano, David

1995-01-01

Detailed simulations of viscous flows in complicated geometries pose a significant challenge to current capabilities of Computational Fluid Dynamics (CFD). To enable routine application of CFD to this class of problems, advanced methodologies are required that employ (a) automated grid generation, (b) adaptivity, (c) accurate discretizations and efficient solvers, and (d) advanced software techniques. Each of these ingredients contributes to increased accuracy, efficiency (in terms of human effort and computer time), and/or reliability of CFD software. In the long run, methodologies employing structured grid systems will remain a viable choice for routine simulation of flows in complex geometries only if genuinely automatic grid generation techniques for structured grids can be developed and if adaptivity is employed more routinely. More research in both these areas is urgently needed.

Assessment of CFD-based Response Surface Model for Ares I Supersonic Ascent Aerodynamics

NASA Technical Reports Server (NTRS)

Hanke, Jeremy L.

2011-01-01

The Ascent Force and Moment Aerodynamic (AFMA) Databases (DBs) for the Ares I Crew Launch Vehicle (CLV) were typically based on wind tunnel (WT) data, with increments provided by computational fluid dynamics (CFD) simulations for aspects of the vehicle that could not be tested in the WT tests. During the Design Analysis Cycle 3 analysis for the outer mold line (OML) geometry designated A106, a major tunnel mishap delayed the WT test for supersonic Mach numbers (M) greater than 1.6 in the Unitary Plan Wind Tunnel at NASA Langley Research Center, and the test delay pushed the final delivery of the A106 AFMA DB back by several months. The aero team developed an interim database based entirely on the already completed CFD simulations to mitigate the impact of the delay. This CFD-based database used a response surface methodology based on radial basis functions to predict the aerodynamic coefficients for M > 1.6 based on only the CFD data from both WT and flight Reynolds number conditions. The aero team used extensive knowledge of the previous AFMA DB for the A103 OML to guide the development of the CFD-based A106 AFMA DB. This report details the development of the CFD-based A106 Supersonic AFMA DB, constructs a prediction of the database uncertainty using data available at the time of development, and assesses the overall quality of the CFD-based DB both qualitatively and quantitatively. This assessment confirms that a reasonable aerodynamic database can be constructed for launch vehicles at supersonic conditions using only CFD data if sufficient knowledge of the physics and expected behavior is available. This report also demonstrates the applicability of non-parametric response surface modeling using radial basis functions for development of aerodynamic databases that exhibit both linear and non-linear behavior throughout a large data space.

Introduction to Computational Methods for Stability and Control (COMSAC)

NASA Technical Reports Server (NTRS)

Hall, Robert M.; Fremaux, C. Michael; Chambers, Joseph R.

2004-01-01

This Symposium is intended to bring together the often distinct cultures of the Stability and Control (S&C) community and the Computational Fluid Dynamics (CFD) community. The COMSAC program is itself a new effort by NASA Langley to accelerate the application of high end CFD methodologies to the demanding job of predicting stability and control characteristics of aircraft. This talk is intended to set the stage for needing a program like COMSAC. It is not intended to give details of the program itself. The topics include: 1) S&C Challenges; 2) Aero prediction methodology; 3) CFD applications; 4) NASA COMSAC planning; 5) Objectives of symposium; and 6) Closing remarks.

Shape optimization of an autonomous underwater vehicle with a ducted propeller using computational fluid dynamics analysis

NASA Astrophysics Data System (ADS)

Joung, Tae-Hwan; Sammut, Karl; He, Fangpo; Lee, Seung-Keon

2012-03-01

Autonomous Underwater Vehicles (AUVs) provide a useful means of collecting detailed oceano-graphic information. The hull resistance of an AUV is an important factor in determining the power requirements and range of the vehicle. This paper describes a procedure using Computational Fluid Dynamics (CFD) for determining the hull resistance of an AUV under development, for a given propeller rotation speed and within a given range of AUV velocities. The CFD analysis results reveal the distribution of the hydrodynamic values (velocity, pressure, etc.) around the AUV hull and its ducted propeller. The paper then proceeds to present a methodology for optimizing the AUV profile in order to reduce the total resistance. This paper demonstrates that shape optimization of conceptual designs is possible using the commercial CFD package contained in Ansys™. The optimum design to minimize the drag force of the AUV was identified for a given object function and a set of constrained design parameters

CFD Aided Design and Production of Hydraulic Turbines

NASA Astrophysics Data System (ADS)

Kaplan, Alper; Cetinturk, Huseyin; Demirel, Gizem; Ayli, Ece; Celebioglu, Kutay; Aradag, Selin; ETU Hydro Research Center Team

2014-11-01

Hydraulic turbines are turbo machines which produce electricity from hydraulic energy. Francis type turbines are the most common one in use today. The design of these turbines requires high engineering effort since each turbine is tailor made due to different head and discharge. Therefore each component of the turbine is designed specifically. During the last decades, Computational Fluid Dynamics (CFD) has become very useful tool to predict hydraulic machinery performance and save time and money for designers. This paper describes a design methodology to optimize a Francis turbine by integrating theoretical and experimental fundamentals of hydraulic machines and commercial CFD codes. Specific turbines are designed and manufactured with the help of a collaborative CFD/CAD/CAM methodology based on computational fluid dynamics and five-axis machining for hydraulic electric power plants. The details are presented in this study. This study is financially supported by Turkish Ministry of Development.

CFD-based design load analysis of 5MW offshore wind turbine

NASA Astrophysics Data System (ADS)

Tran, T. T.; Ryu, G. J.; Kim, Y. H.; Kim, D. H.

2012-11-01

The structure and aerodynamic loads acting on NREL 5MW reference wind turbine blade are calculated and analyzed based on advanced Computational Fluid Dynamics (CFD) and unsteady Blade Element Momentum (BEM). A detailed examination of the six force components has been carried out (three force components and three moment components). Structure load (gravity and inertia load) and aerodynamic load have been obtained by additional structural calculations (CFD or BEM, respectively,). In CFD method, the Reynolds Average Navier-Stokes approach was applied to solve the continuity equation of mass conservation and momentum balance so that the complex flow around wind turbines was modeled. Written in C programming language, a User Defined Function (UDF) code which defines transient velocity profile according to the Extreme Operating Gust condition was compiled into commercial FLUENT package. Furthermore, the unsteady BEM with 3D stall model has also adopted to investigate load components on wind turbine rotor. The present study introduces a comparison between advanced CFD and unsteady BEM for determining load on wind turbine rotor. Results indicate that there are good agreements between both present methods. It is importantly shown that six load components on wind turbine rotor is significant effect under Extreme Operating Gust (EOG) condition. Using advanced CFD and additional structural calculations, this study has succeeded to construct accuracy numerical methodology to estimate total load of wind turbine that compose of aerodynamic load and structure load.

A Method for Generating Reduced-Order Linear Models of Multidimensional Supersonic Inlets

NASA Technical Reports Server (NTRS)

Chicatelli, Amy; Hartley, Tom T.

1998-01-01

Simulation of high speed propulsion systems may be divided into two categories, nonlinear and linear. The nonlinear simulations are usually based on multidimensional computational fluid dynamics (CFD) methodologies and tend to provide high resolution results that show the fine detail of the flow. Consequently, these simulations are large, numerically intensive, and run much slower than real-time. ne linear simulations are usually based on large lumping techniques that are linearized about a steady-state operating condition. These simplistic models often run at or near real-time but do not always capture the detailed dynamics of the plant. Under a grant sponsored by the NASA Lewis Research Center, Cleveland, Ohio, a new method has been developed that can be used to generate improved linear models for control design from multidimensional steady-state CFD results. This CFD-based linear modeling technique provides a small perturbation model that can be used for control applications and real-time simulations. It is important to note the utility of the modeling procedure; all that is needed to obtain a linear model of the propulsion system is the geometry and steady-state operating conditions from a multidimensional CFD simulation or experiment. This research represents a beginning step in establishing a bridge between the controls discipline and the CFD discipline so that the control engineer is able to effectively use multidimensional CFD results in control system design and analysis.

Direct CFD Predictions of Low Frequency Sounds Generated by Helicopter Main Rotors

NASA Technical Reports Server (NTRS)

Sim, Ben W.; Potsdam, Mark; Conner, Dave; Watts, Michael E.

2010-01-01

This proposed paper will highlight the application of a CSD/CFD methodology currently inuse by the US Army Aerfolightdynamics Directorate (AFDD) to assess the feasibility and fidelity of directly predicting low frequency sounds of helicopter rotors.

Modeling Subgrid Scale Droplet Deposition in Multiphase-CFD

NASA Astrophysics Data System (ADS)

Agostinelli, Giulia; Baglietto, Emilio

2017-11-01

The development of first-principle-based constitutive equations for the Eulerian-Eulerian CFD modeling of annular flow is a major priority to extend the applicability of multiphase CFD (M-CFD) across all two-phase flow regimes. Two key mechanisms need to be incorporated in the M-CFD framework, the entrainment of droplets from the liquid film, and their deposition. Here we focus first on the aspect of deposition leveraging a separate effects approach. Current two-field methods in M-CFD do not include appropriate local closures to describe the deposition of droplets in annular flow conditions. As many integral correlations for deposition have been proposed for lumped parameters methods applications, few attempts exist in literature to extend their applicability to CFD simulations. The integral nature of the approach limits its applicability to fully developed flow conditions, without geometrical or flow variations, therefore negating the scope of CFD application. A new approach is proposed here that leverages local quantities to predict the subgrid-scale deposition rate. The methodology is first tested into a three-field approach CFD model.

Numerical analysis of the hot-gas-side and coolant-side heat transfer in liquid rocket engine combustors

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Van, Luong

1992-01-01

The objective of this paper are to develop a multidisciplinary computational methodology to predict the hot-gas-side and coolant-side heat transfer and to use it in parametric studies to recommend optimized design of the coolant channels for a regeneratively cooled liquid rocket engine combustor. An integrated numerical model which incorporates CFD for the hot-gas thermal environment, and thermal analysis for the liner and coolant channels, was developed. This integrated CFD/thermal model was validated by comparing predicted heat fluxes with those of hot-firing test and industrial design methods for a 40 k calorimeter thrust chamber and the Space Shuttle Main Engine Main Combustion Chamber. Parametric studies were performed for the Advanced Main Combustion Chamber to find a strategy for a proposed combustion chamber coolant channel design.

Patient-specific CFD simulation of intraventricular haemodynamics based on 3D ultrasound imaging.

PubMed

Bavo, A M; Pouch, A M; Degroote, J; Vierendeels, J; Gorman, J H; Gorman, R C; Segers, P

2016-09-09

The goal of this paper is to present a computational fluid dynamic (CFD) model with moving boundaries to study the intraventricular flows in a patient-specific framework. Starting from the segmentation of real-time transesophageal echocardiographic images, a CFD model including the complete left ventricle and the moving 3D mitral valve was realized. Their motion, known as a function of time from the segmented ultrasound images, was imposed as a boundary condition in an Arbitrary Lagrangian-Eulerian framework. The model allowed for a realistic description of the displacement of the structures of interest and for an effective analysis of the intraventricular flows throughout the cardiac cycle. The model provides detailed intraventricular flow features, and highlights the importance of the 3D valve apparatus for the vortex dynamics and apical flow. The proposed method could describe the haemodynamics of the left ventricle during the cardiac cycle. The methodology might therefore be of particular importance in patient treatment planning to assess the impact of mitral valve treatment on intraventricular flow dynamics.

CFD Validation Experiment of a Mach 2.5 Axisymmetric Shock-Wave/Boundary-Layer Interaction

NASA Technical Reports Server (NTRS)

Davis, David O.

2015-01-01

Experimental investigations of specific flow phenomena, e.g., Shock Wave Boundary-Layer Interactions (SWBLI), provide great insight to the flow behavior but often lack the necessary details to be useful as CFD validation experiments. Reasons include: 1.Undefined boundary conditions Inconsistent results 2.Undocumented 3D effects (CL only measurements) 3.Lack of uncertainty analysis While there are a number of good subsonic experimental investigations that are sufficiently documented to be considered test cases for CFD and turbulence model validation, the number of supersonic and hypersonic cases is much less. This was highlighted by Settles and Dodsons [1] comprehensive review of available supersonic and hypersonic experimental studies. In all, several hundred studies were considered for their database.Of these, over a hundred were subjected to rigorous acceptance criteria. Based on their criteria, only 19 (12 supersonic, 7 hypersonic) were considered of sufficient quality to be used for validation purposes. Aeschliman and Oberkampf [2] recognized the need to develop a specific methodology for experimental studies intended specifically for validation purposes.

Calcul des coefficients aerodynamiques d'un avion complet par la methode rans

NASA Astrophysics Data System (ADS)

Lux, Quentin

The evaluation of stability derivatives within the entire flight domain through the use of Computational Fluids Dynamics is one of the next challenges of numerical external aerodynamics. To remain competitive, aircraft manufacturers are increasingly turning to CFD to provide aerodynamic data in an effort to increase the quality of their products while reducing the development turnaround time and costs. However, the numerical analysis need to evolve to insure a higher fidelity and meets the need of the aircraft manufacturers and decrease wind-tunnel experiments. The present study aims to estimate the potential of a high-fidelity 3D CFD analysis in the determination of the aerodynamic behavior of an airplane in incidence and yaw. The complete methodology to obtain the static stability coefficients will be developed and the results compared with the experimental data. All the phases of the methodology will be presented including: the treatment of the geometry, the meshing process and the flow solving by a commercial CFD software. Important points to obtain a high-fidelity will also be developed as well as the verification and validation phase. The results will be presented as raw as well as with an error metric in order to estimate the accuracy of the current method. First, it will be applied on a validation case from the literature: the Drag Prediction Workshop II with the study of the DLR-F6. The test cases including a study at fixed CL as well as an incidence sweeping will be recreated. Then, the methodology will be applied to a Bombardier Research Aircraft. The various associations of components on the fuselage including the wing, the nacelle and the tail will be studied in incidence and yaw sweepings. The study concludes on the potential of such study with regard to its development costs in the cases presented here.

Development of Tripropellant CFD Design Code

NASA Technical Reports Server (NTRS)

Farmer, Richard C.; Cheng, Gary C.; Anderson, Peter G.

1998-01-01

A tripropellant, such as GO2/H2/RP-1, CFD design code has been developed to predict the local mixing of multiple propellant streams as they are injected into a rocket motor. The code utilizes real fluid properties to account for the mixing and finite-rate combustion processes which occur near an injector faceplate, thus the analysis serves as a multi-phase homogeneous spray combustion model. Proper accounting of the combustion allows accurate gas-side temperature predictions which are essential for accurate wall heating analyses. The complex secondary flows which are predicted to occur near a faceplate cannot be quantitatively predicted by less accurate methodology. Test cases have been simulated to describe an axisymmetric tripropellant coaxial injector and a 3-dimensional RP-1/LO2 impinger injector system. The analysis has been shown to realistically describe such injector combustion flowfields. The code is also valuable to design meaningful future experiments by determining the critical location and type of measurements needed.

A CFD study of complex missile and store configurations in relative motion

NASA Technical Reports Server (NTRS)

Baysal, Oktay

1995-01-01

An investigation was conducted from May 16, 1990 to August 31, 1994 on the development of computational fluid dynamics (CFD) methodologies for complex missiles and the store separation problem. These flowfields involved multiple-component configurations, where at least one of the objects was engaged in relative motion. The two most important issues that had to be addressed were: (1) the unsteadiness of the flowfields (time-accurate and efficient CFD algorithms for the unsteady equations), and (2) the generation of grid systems which would permit multiple and moving bodies in the computational domain (dynamic domain decomposition). The study produced two competing and promising methodologies, and their proof-of-concept cases, which have been reported in the open literature: (1) Unsteady solutions on dynamic, overlapped grids, which may also be perceived as moving, locally-structured grids, and (2) Unsteady solutions on dynamic, unstructured grids.

Observations Regarding Use of Advanced CFD Analysis, Sensitivity Analysis, and Design Codes in MDO

NASA Technical Reports Server (NTRS)

Newman, Perry A.; Hou, Gene J. W.; Taylor, Arthur C., III

1996-01-01

Observations regarding the use of advanced computational fluid dynamics (CFD) analysis, sensitivity analysis (SA), and design codes in gradient-based multidisciplinary design optimization (MDO) reflect our perception of the interactions required of CFD and our experience in recent aerodynamic design optimization studies using CFD. Sample results from these latter studies are summarized for conventional optimization (analysis - SA codes) and simultaneous analysis and design optimization (design code) using both Euler and Navier-Stokes flow approximations. The amount of computational resources required for aerodynamic design using CFD via analysis - SA codes is greater than that required for design codes. Thus, an MDO formulation that utilizes the more efficient design codes where possible is desired. However, in the aerovehicle MDO problem, the various disciplines that are involved have different design points in the flight envelope; therefore, CFD analysis - SA codes are required at the aerodynamic 'off design' points. The suggested MDO formulation is a hybrid multilevel optimization procedure that consists of both multipoint CFD analysis - SA codes and multipoint CFD design codes that perform suboptimizations.

Adjoint-Based Methodology for Time-Dependent Optimal Control (AMTOC)

NASA Technical Reports Server (NTRS)

Yamaleev, Nail; Diskin, boris; Nishikawa, Hiroaki

2012-01-01

During the five years of this project, the AMTOC team developed an adjoint-based methodology for design and optimization of complex time-dependent flows, implemented AMTOC in a testbed environment, directly assisted in implementation of this methodology in the state-of-the-art NASA's unstructured CFD code FUN3D, and successfully demonstrated applications of this methodology to large-scale optimization of several supersonic and other aerodynamic systems, such as fighter jet, subsonic aircraft, rotorcraft, high-lift, wind-turbine, and flapping-wing configurations. In the course of this project, the AMTOC team has published 13 refereed journal articles, 21 refereed conference papers, and 2 NIA reports. The AMTOC team presented the results of this research at 36 international and national conferences, meeting and seminars, including International Conference on CFD, and numerous AIAA conferences and meetings. Selected publications that include the major results of the AMTOC project are enclosed in this report.

Computational Fluid Dynamics Analysis Success Stories of X-Plane Design to Flight Test

NASA Technical Reports Server (NTRS)

Cosentino, Gary B.

2008-01-01

Examples of the design and flight test of three true X-planes are described, particularly X-plane design techniques that relied heavily on computational fluid dynamics(CFD) analysis. Three examples are presented: the X-36 Tailless Fighter Agility Research Aircraft, the X-45A Unmanned Combat Air Vehicle, and the X-48B Blended Wing Body Demonstrator Aircraft. An overview is presented of the uses of CFD analysis, comparison and contrast with wind tunnel testing, and information derived from CFD analysis that directly related to successful flight test. Lessons learned on the proper and improper application of CFD analysis are presented. Highlights of the flight-test results of the three example X-planes are presented. This report discusses developing an aircraft shape from early concept and three-dimensional modeling through CFD analysis, wind tunnel testing, further refined CFD analysis, and, finally, flight. An overview of the areas in which CFD analysis does and does not perform well during this process is presented. How wind tunnel testing complements, calibrates, and verifies CFD analysis is discussed. Lessons learned revealing circumstances under which CFD analysis results can be misleading are given. Strengths and weaknesses of the various flow solvers, including panel methods, Euler, and Navier-Stokes techniques, are discussed.

A multi-fidelity framework for physics based rotor blade simulation and optimization

NASA Astrophysics Data System (ADS)

Collins, Kyle Brian

New helicopter rotor designs are desired that offer increased efficiency, reduced vibration, and reduced noise. Rotor Designers in industry need methods that allow them to use the most accurate simulation tools available to search for these optimal designs. Computer based rotor analysis and optimization have been advanced by the development of industry standard codes known as "comprehensive" rotorcraft analysis tools. These tools typically use table look-up aerodynamics, simplified inflow models and perform aeroelastic analysis using Computational Structural Dynamics (CSD). Due to the simplified aerodynamics, most design studies are performed varying structural related design variables like sectional mass and stiffness. The optimization of shape related variables in forward flight using these tools is complicated and results are viewed with skepticism because rotor blade loads are not accurately predicted. The most accurate methods of rotor simulation utilize Computational Fluid Dynamics (CFD) but have historically been considered too computationally intensive to be used in computer based optimization, where numerous simulations are required. An approach is needed where high fidelity CFD rotor analysis can be utilized in a shape variable optimization problem with multiple objectives. Any approach should be capable of working in forward flight in addition to hover. An alternative is proposed and founded on the idea that efficient hybrid CFD methods of rotor analysis are ready to be used in preliminary design. In addition, the proposed approach recognizes the usefulness of lower fidelity physics based analysis and surrogate modeling. Together, they are used with high fidelity analysis in an intelligent process of surrogate model building of parameters in the high fidelity domain. Closing the loop between high and low fidelity analysis is a key aspect of the proposed approach. This is done by using information from higher fidelity analysis to improve predictions made with lower fidelity models. This thesis documents the development of automated low and high fidelity physics based rotor simulation frameworks. The low fidelity framework uses a comprehensive code with simplified aerodynamics. The high fidelity model uses a parallel processor capable CFD/CSD methodology. Both low and high fidelity frameworks include an aeroacoustic simulation for prediction of noise. A synergistic process is developed that uses both the low and high fidelity frameworks together to build approximate models of important high fidelity metrics as functions of certain design variables. To test the process, a 4-bladed hingeless rotor model is used as a baseline. The design variables investigated include tip geometry and spanwise twist distribution. Approximation models are built for metrics related to rotor efficiency and vibration using the results from 60+ high fidelity (CFD/CSD) experiments and 400+ low fidelity experiments. Optimization using the approximation models found the Pareto Frontier anchor points, or the design having maximum rotor efficiency and the design having minimum vibration. Various Pareto generation methods are used to find designs on the frontier between these two anchor designs. When tested in the high fidelity framework, the Pareto anchor designs are shown to be very good designs when compared with other designs from the high fidelity database. This provides evidence that the process proposed has merit. Ultimately, this process can be utilized by industry rotor designers with their existing tools to bring high fidelity analysis into the preliminary design stage of rotors. In conclusion, the methods developed and documented in this thesis have made several novel contributions. First, an automated high fidelity CFD based forward flight simulation framework has been built for use in preliminary design optimization. The framework was built around an integrated, parallel processor capable CFD/CSD/AA process. Second, a novel method of building approximate models of high fidelity parameters has been developed. The method uses a combination of low and high fidelity results and combines Design of Experiments, statistical effects analysis, and aspects of approximation model management. And third, the determination of rotor blade shape variables through optimization using CFD based analysis in forward flight has been performed. This was done using the high fidelity CFD/CSD/AA framework and method mentioned above. While the low and high fidelity predictions methods used in the work still have inaccuracies that can affect the absolute levels of the results, a framework has been successfully developed and demonstrated that allows for an efficient process to improve rotor blade designs in terms of a selected choice of objective function(s). Using engineering judgment, this methodology could be applied today to investigate opportunities to improve existing designs. With improvements in the low and high fidelity prediction components that will certainly occur, this framework could become a powerful tool for future rotorcraft design work. (Abstract shortened by UMI.)

A User's Guide to CGNS. 1.0

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L.; Poirier, Diane M. A.; Bush, Robert H.; Towne, Charles E.

2001-01-01

The CFD General Notation System (CGNS) was developed to be a self-descriptive, machine-independent standard for storing CFD aerodynamic data. This guide aids users in the implementation of CGNS. It is intended as a tutorial on the usage of the CGNS mid-level library routines for reading and writing grid and flow solution datasets for both structured and unstructured methodologies.

4D Subject-Specific Inverse Modeling of the Chick Embryonic Heart Outflow Tract Hemodynamics

PubMed Central

Goenezen, Sevan; Chivukula, Venkat Keshav; Midgett, Madeline; Phan, Ly; Rugonyi, Sandra

2015-01-01

Blood flow plays a critical role in regulating embryonic cardiac growth and development, with altered flow leading to congenital heart disease. Progress in the field, however, is hindered by a lack of quantification of hemodynamic conditions in the developing heart. In this study, we present a methodology to quantify blood flow dynamics in the embryonic heart using subject-specific computational fluid dynamics (CFD) models. While the methodology is general, we focused on a model of the chick embryonic heart outflow tract (OFT), which distally connects the heart to the arterial system, and is the region of origin of many congenital cardiac defects. Using structural and Doppler velocity data collected from optical coherence tomography (OCT), we generated 4D (3D + time) embryo-specific CFD models of the heart OFT. To replicate the blood flow dynamics over time during the cardiac cycle, we developed an iterative inverse-method optimization algorithm, which determines the CFD model boundary conditions such that differences between computed velocities and measured velocities at one point within the OFT lumen are minimized. Results from our developed CFD model agree with previously measured hemodynamics in the OFT. Further, computed velocities and measured velocities differ by less than 15% at locations that were not used in the optimization, validating the model. The presented methodology can be used in quantifications of embryonic cardiac hemodynamics under normal and altered blood flow conditions, enabling an in depth quantitative study of how blood flow influences cardiac development. PMID:26361767

Probabilistic evaluation of uncertainties and risks in aerospace components

NASA Technical Reports Server (NTRS)

Shah, A. R.; Shiao, M. C.; Nagpal, V. K.; Chamis, C. C.

1992-01-01

A methodology is presented for the computational simulation of primitive variable uncertainties, and attention is given to the simulation of specific aerospace components. Specific examples treated encompass a probabilistic material behavior model, as well as static, dynamic, and fatigue/damage analyses of a turbine blade in a mistuned bladed rotor in the SSME turbopumps. An account is given of the use of the NESSES probabilistic FEM analysis CFD code.

Numerical characterization of landing gear aeroacoustics using advanced simulation and analysis techniques

NASA Astrophysics Data System (ADS)

Redonnet, S.; Ben Khelil, S.; Bulté, J.; Cunha, G.

2017-09-01

With the objective of aircraft noise mitigation, we here address the numerical characterization of the aeroacoustics by a simplified nose landing gear (NLG), through the use of advanced simulation and signal processing techniques. To this end, the NLG noise physics is first simulated through an advanced hybrid approach, which relies on Computational Fluid Dynamics (CFD) and Computational AeroAcoustics (CAA) calculations. Compared to more traditional hybrid methods (e.g. those relying on the use of an Acoustic Analogy), and although it is used here with some approximations made (e.g. design of the CFD-CAA interface), the present approach does not rely on restrictive assumptions (e.g. equivalent noise source, homogeneous propagation medium), which allows to incorporate more realism into the prediction. In a second step, the outputs coming from such CFD-CAA hybrid calculations are processed through both traditional and advanced post-processing techniques, thus offering to further investigate the NLG's noise source mechanisms. Among other things, this work highlights how advanced computational methodologies are now mature enough to not only simulate realistic problems of airframe noise emission, but also to investigate their underlying physics.

CAD-Based Modeling of Advanced Rotary Wing Structures for Integrated 3-D Aeromechanics Analysis

NASA Astrophysics Data System (ADS)

Staruk, William

This dissertation describes the first comprehensive use of integrated 3-D aeromechanics modeling, defined as the coupling of 3-D solid finite element method (FEM) structural dynamics with 3-D computational fluid dynamics (CFD), for the analysis of a real helicopter rotor. The development of this new methodology (a departure from how rotor aeroelastic analysis has been performed for 40 years), its execution on a real rotor, and the fundamental understanding of aeromechanics gained from it, are the key contributions of this dissertation. This work also presents the first CFD/CSD analysis of a tiltrotor in edgewise flight, revealing many of its unique loading mechanisms. The use of 3-D FEM, integrated with a trim solver and aerodynamics modeling, has the potential to enhance the design of advanced rotors by overcoming fundamental limitations of current generation beam-based analysis tools and offering integrated internal dynamic stress and strain predictions for design. Two primary goals drove this research effort: 1) developing a methodology to create 3-D CAD-based brick finite element models of rotors including multibody joints, controls, and aerodynamic interfaces, and 2) refining X3D, the US Army's next generation rotor structural dynamics solver featuring 3-D FEM within a multibody formulation with integrated aerodynamics, to model a tiltrotor in the edgewise conversion flight regime, which drives critical proprotor structural loads. Prior tiltrotor analysis has primarily focused on hover aerodynamics with rigid blades or forward flight whirl-flutter stability with simplified aerodynamics. The first goal was met with the development of a detailed methodology for generating multibody 3-D structural models, starting from CAD geometry, continuing to higher-order hexahedral finite element meshing, to final assembly of the multibody model by creating joints, assigning material properties, and defining the aerodynamic interface. Several levels of verification and validation were carried out systematically, covering formulation, model accuracy, and accuracy of the physics of the problem and the many complex coupled aeromechanical phenomena that characterize the behavior of a tiltrotor in the conversion corridor. Compatibility of the new structural analysis models with X3D is demonstrated using analytical test cases, including 90° twisted beams and thick composite plates, and a notional bearingless rotor. Prediction of deformations and stresses in composite beams and plates is validated and verified against experimental measurements, theory, and state-of-the-art beam models. The second goal was met through integrated analysis of the Tilt Rotor Aeroacoustic Model (TRAM) proprotor using X3D coupled to Helios--the US Army's next generation CFD framework featuring a high fidelity Reynolds-average Navier-Stokes (RANS) structured/unstructured overset solver--as well as low order aerodynamic models. Although development of CFD was not part of this work, coupling X3D with Helios was, including establishing consistent interface definitions for blade deformations (for CFD mesh motion), aerodynamic interfaces (for loads transfer), and rotor control angles (for trim). It is expected that this method and solver will henceforth be an integral part of the Helios framework, providing an equal fidelity of representation for fluids and structures in the development of future advanced rotor systems. Structural dynamics analysis of the TRAM model show accurate prediction of the lower natural frequencies, demonstrating the ability to model advanced rotors from first principles using 3-D structural dynamics, and a study of how joint properties affect these frequencies reveals how X3D can be used as a detailed design tool. The CFD/CSD analysis reveals accurate prediction of rotor performance and airloads in edgewise flight when compared to wind tunnel test data. Structural blade loads trends are well predicted at low thrust, but a 3/rev component of flap and lag bending moment appearing in test data at high thrust remains a mystery. Efficiently simulating a gimbaled rotor is not trivial; a time-domain method with only a single blade model is proposed and tested. The internal stress in the blade, particularly at its root where the gimbal action has major influence, is carefully examined, revealing complex localized loading patterns.

Aeroacoustic Prediction Codes

NASA Technical Reports Server (NTRS)

Gliebe, P; Mani, R.; Shin, H.; Mitchell, B.; Ashford, G.; Salamah, S.; Connell, S.; Huff, Dennis (Technical Monitor)

2000-01-01

This report describes work performed on Contract NAS3-27720AoI 13 as part of the NASA Advanced Subsonic Transport (AST) Noise Reduction Technology effort. Computer codes were developed to provide quantitative prediction, design, and analysis capability for several aircraft engine noise sources. The objective was to provide improved, physics-based tools for exploration of noise-reduction concepts and understanding of experimental results. Methods and codes focused on fan broadband and 'buzz saw' noise and on low-emissions combustor noise and compliment work done by other contractors under the NASA AST program to develop methods and codes for fan harmonic tone noise and jet noise. The methods and codes developed and reported herein employ a wide range of approaches, from the strictly empirical to the completely computational, with some being semiempirical analytical, and/or analytical/computational. Emphasis was on capturing the essential physics while still considering method or code utility as a practical design and analysis tool for everyday engineering use. Codes and prediction models were developed for: (1) an improved empirical correlation model for fan rotor exit flow mean and turbulence properties, for use in predicting broadband noise generated by rotor exit flow turbulence interaction with downstream stator vanes: (2) fan broadband noise models for rotor and stator/turbulence interaction sources including 3D effects, noncompact-source effects. directivity modeling, and extensions to the rotor supersonic tip-speed regime; (3) fan multiple-pure-tone in-duct sound pressure prediction methodology based on computational fluid dynamics (CFD) analysis; and (4) low-emissions combustor prediction methodology and computer code based on CFD and actuator disk theory. In addition. the relative importance of dipole and quadrupole source mechanisms was studied using direct CFD source computation for a simple cascadeigust interaction problem, and an empirical combustor-noise correlation model was developed from engine acoustic test results. This work provided several insights on potential approaches to reducing aircraft engine noise. Code development is described in this report, and those insights are discussed.

Development of Detonation Modeling Capabilities for Rocket Test Facilities: Hydrogen-Oxygen-Nitrogen Mixtures

NASA Technical Reports Server (NTRS)

Allgood, Daniel C.

2016-01-01

The objective of the presented work was to develop validated computational fluid dynamics (CFD) based methodologies for predicting propellant detonations and their associated blast environments. Applications of interest were scenarios relevant to rocket propulsion test and launch facilities. All model development was conducted within the framework of the Loci/CHEM CFD tool due to its reliability and robustness in predicting high-speed combusting flow-fields associated with rocket engines and plumes. During the course of the project, verification and validation studies were completed for hydrogen-fueled detonation phenomena such as shock-induced combustion, confined detonation waves, vapor cloud explosions, and deflagration-to-detonation transition (DDT) processes. The DDT validation cases included predicting flame acceleration mechanisms associated with turbulent flame-jets and flow-obstacles. Excellent comparison between test data and model predictions were observed. The proposed CFD methodology was then successfully applied to model a detonation event that occurred during liquid oxygen/gaseous hydrogen rocket diffuser testing at NASA Stennis Space Center.

Comparison of a 3-D CFD-DSMC Solution Methodology With a Wind Tunnel Experiment

NASA Technical Reports Server (NTRS)

Glass, Christopher E.; Horvath, Thomas J.

2002-01-01

A solution method for problems that contain both continuum and rarefied flow regions is presented. The methodology is applied to flow about the 3-D Mars Sample Return Orbiter (MSRO) that has a highly compressed forebody flow, a shear layer where the flow separates from a forebody lip, and a low density wake. Because blunt body flow fields contain such disparate regions, employing a single numerical technique to solve the entire 3-D flow field is often impractical, or the technique does not apply. Direct simulation Monte Carlo (DSMC) could be employed to solve the entire flow field; however, the technique requires inordinate computational resources for continuum and near-continuum regions, and is best suited for the wake region. Computational fluid dynamics (CFD) will solve the high-density forebody flow, but continuum assumptions do not apply in the rarefied wake region. The CFD-DSMC approach presented herein may be a suitable way to obtain a higher fidelity solution.

OFF-Stagnation point testing in plasma facility

NASA Astrophysics Data System (ADS)

Viladegut, A.; Chazot, O.

2015-06-01

Reentry space vehicles face extreme conditions of heat flux when interacting with the atmosphere at hypersonic velocities. Stagnation point heat flux is normally used as a reference for Thermal Protection Material (TPS) design; however, many critical phenomena also occur at off-stagnation point. This paper adresses the implementation of an offstagnation point methodology able to duplicate in ground facility the hypersonic boundary layer over a flat plate model. The first analysis using two-dimensional (2D) computational fluid dynamics (CFD) simulations is carried out to understand the limitations of this methodology when applying it in plasma wind tunnel. The results from the testing campaign at VKI Plasmatron are also presented.

An Analysis of Performance Enhancement Techniques for Overset Grid Applications

NASA Technical Reports Server (NTRS)

Djomehri, J. J.; Biswas, R.; Potsdam, M.; Strawn, R. C.; Biegel, Bryan (Technical Monitor)

2002-01-01

The overset grid methodology has significantly reduced time-to-solution of high-fidelity computational fluid dynamics (CFD) simulations about complex aerospace configurations. The solution process resolves the geometrical complexity of the problem domain by using separately generated but overlapping structured discretization grids that periodically exchange information through interpolation. However, high performance computations of such large-scale realistic applications must be handled efficiently on state-of-the-art parallel supercomputers. This paper analyzes the effects of various performance enhancement techniques on the parallel efficiency of an overset grid Navier-Stokes CFD application running on an SGI Origin2000 machine. Specifically, the role of asynchronous communication, grid splitting, and grid grouping strategies are presented and discussed. Results indicate that performance depends critically on the level of latency hiding and the quality of load balancing across the processors.

Non-Newtonian Liquid Flow through Small Diameter Piping Components: CFD Analysis

NASA Astrophysics Data System (ADS)

Bandyopadhyay, Tarun Kanti; Das, Sudip Kumar

2016-10-01

Computational Fluid Dynamics (CFD) analysis have been carried out to evaluate the frictional pressure drop across the horizontal pipeline and different piping components, like elbows, orifices, gate and globe valves for non-Newtonian liquid through 0.0127 m pipe line. The mesh generation is done using GAMBIT 6.3 and FLUENT 6.3 is used for CFD analysis. The CFD results are verified with our earlier published experimental data. The CFD results show the very good agreement with the experimental values.

CFD analysis on gas distribution for different scrubber redirection configurations in sump cut.

PubMed

Zheng, Y; Organiscak, J A; Zhou, L; Beck, T W; Rider, J P

2015-01-01

The National Institute for Occupational Safety and Health's Office of Mine Safety and Health Research recently developed a series of models using computational fluid dynamics (CFD) to study the gas distribution around a continuous mining machine with various fan-powered flooded bed scrubber discharge configurations. CFD models using Species Transport Model without reactions in FLUENT were constructed to evaluate the redirection of scrubber discharge toward the mining face rather than behind the return curtain. The following scenarios are considered in this study: 100 percent of the discharge redirected back toward the face on the off-curtain side of the continuous miner; 100 percent of the discharge redirected back toward the face, but divided equally to both sides of the machine; and 15 percent of the discharge redirected toward the face on the off-curtain side of the machine, with 85 percent directed into the return. These models were compared against a model with a conventional scrubber discharge, where air is directed away from the face into the return. The CFD models were calibrated and validated based on experimental data and accurately predicted sulfur hexafluoride (SF 6 ) gas levels at four gas monitoring locations. One additional prediction model was simulated to consider a different scrubber discharge angle for the 100 percent redirected, equally divided case. These models identified relatively high gassy areas around the continuous miner, which may not warrant their use in coal mines with medium to high methane liberation rates. This paper describes the methodology used to develop the CFD models, and the validation of the models based on experimental data.

Towards an Aero-Propulso-Servo-Elasticity Analysis of a Commercial Supersonic Transport

NASA Technical Reports Server (NTRS)

Connolly, Joseph W.; Kopasakis, George; Chwalowski, Pawel; Sanetrik, Mark D.; Carlson, Jan-Renee; Silva, Walt A.; McNamara, Jack

2016-01-01

This paper covers the development of an aero-propulso-servo-elastic (APSE) model using computational fluid dynamics (CFD) and linear structural deformations. The APSE model provides the integration of the following two previously developed nonlinear dynamic simulations: a variable cycle turbofan engine and an elastic supersonic commercial transport vehicle. The primary focus of this study is to provide a means to include relevant dynamics of a turbomachinery propulsion system into the aeroelastic studies conducted during a vehicle design, which have historically neglected propulsion effects. A high fidelity CFD tool is used here for the integration platform. The elastic vehicle neglecting the propulsion system serves as a comparison of traditional approaches to the APSE results. An overview of the methodology is presented for integrating the propulsion system and elastic vehicle. Static aeroelastic analysis comparisons between the traditional and developed APSE models for a wing tip detection indicate that the propulsion system impact on the vehicle elastic response could increase the detection by approximately ten percent.

Using CFD as Rocket Injector Design Tool: Recent Progress at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Tucker, Kevin; West, Jeff; Williams, Robert; Lin, Jeff; Rocker, Marvin; Canabal, Francisco; Robles, Bryan; Garcia, Robert; Chenoweth, James

2003-01-01

The choice of tools used for injector design is in a transitional phase between exclusive reliance on the empirically based correlations and extensive use of computational fluid dynamics (CFD). The Next Generation Launch Technology (NGLT) Program goals emphasizing lower costs and increased reliability have produced a need to enable CFD as an injector design tool in a shorter time frame. This is the primary objective of the Staged Combustor Injector Technology Task currently under way at Marshall Space Flight Center (MSFC). The documentation of this effort begins with a very brief status of current injector design tools. MSFC's vision for use of CFD as a tool for combustion devices design is stated and discussed with emphasis on the injector. The concept of the Simulation Readiness Level (SRL), comprised of solution fidelity, robustness and accuracy, is introduced and discussed. This quantitative measurement is used to establish the gap between the current state of demonstrated capability and that necessary for regular use in the design process. MSFC's view of the validation process is presented and issues associated with obtaining the necessary data are noted and discussed. Three current experimental efforts aimed at generating validation data are presented. The importance of uncertainty analysis to understand the data quality is also demonstrated. First, a brief status of current injector design tools is provided as context for the current effort. Next, the MSFC vision for using CFD as an injector design tool is stated. A generic CFD-based injector design methodology is also outlined and briefly discussed. Three areas where MSFC is using injector CFD analyses for program support will be discussed. These include the Integrated Powerhead Development (IPD) engine which uses hydrogen and oxygen propellants in a full flow staged combustion (FFSC) cycle and the TR-107 and the RS84 engine both of which use RP-1 and oxygen in an ORSC cycle. Finally, an attempt is made to objectively summarize what progress has been made at MSFC in enabling CFD as an injector design tool.

Juncture flow improvement for wing/pylon configurations by using CFD methodology

NASA Technical Reports Server (NTRS)

Gea, Lie-Mine; Chyu, Wei J.; Stortz, Michael W.; Chow, Chuen-Yen

1993-01-01

Transonic flow field around a fighter wing/pylon configuration was simulated by using an implicit upwinding Navier-Stokes flow solver (F3D) and overset grid technology (Chimera). Flow separation and local shocks near the wing/pylon junction were observed in flight and predicted by numerical calculations. A new pylon/fairing shape was proposed to improve the flow quality. Based on numerical results, the size of separation area is significantly reduced and the onset of separation is delayed farther downstream. A smoother pressure gradient is also obtained near the junction area. This paper demonstrates that computational fluid dynamics (CFD) methodology can be used as a practical tool for aircraft design.

iCFD: Interpreted Computational Fluid Dynamics - Degeneration of CFD to one-dimensional advection-dispersion models using statistical experimental design - The secondary clarifier.

PubMed

Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat; Plósz, Benedek Gy

2015-10-15

The present study aims at using statistically designed computational fluid dynamics (CFD) simulations as numerical experiments for the identification of one-dimensional (1-D) advection-dispersion models - computationally light tools, used e.g., as sub-models in systems analysis. The objective is to develop a new 1-D framework, referred to as interpreted CFD (iCFD) models, in which statistical meta-models are used to calculate the pseudo-dispersion coefficient (D) as a function of design and flow boundary conditions. The method - presented in a straightforward and transparent way - is illustrated using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor screening study and system understanding, 50 different sets of design and flow conditions are selected using Latin Hypercube Sampling (LHS). The boundary condition sets are imposed on a 2-D axi-symmetrical CFD simulation model of the SST. In the framework, to degenerate the 2-D model structure, CFD model outputs are approximated by the 1-D model through the calibration of three different model structures for D. Correlation equations for the D parameter then are identified as a function of the selected design and flow boundary conditions (meta-models), and their accuracy is evaluated against D values estimated in each numerical experiment. The evaluation and validation of the iCFD model structure is carried out using scenario simulation results obtained with parameters sampled from the corners of the LHS experimental region. For the studied SST, additional iCFD model development was carried out in terms of (i) assessing different density current sub-models; (ii) implementation of a combined flocculation, hindered, transient and compression settling velocity function; and (iii) assessment of modelling the onset of transient and compression settling. Furthermore, the optimal level of model discretization both in 2-D and 1-D was undertaken. Results suggest that the iCFD model developed for the SST through the proposed methodology is able to predict solid distribution with high accuracy - taking a reasonable computational effort - when compared to multi-dimensional numerical experiments, under a wide range of flow and design conditions. iCFD tools could play a crucial role in reliably predicting systems' performance under normal and shock events. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evaluation of flow mixing in an ARID-HV algal raceway using statistics of temporal and spatial distribution of fluid particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Ben; Li, Peiwen; Waller, Peter

2015-02-27

This paper analyzes and evaluates the flow mixing in an open channel algal raceway for biofuel production. The flow mixing governs the frequency of how algae cells are exposed to sunlight, due to the fluid movement between the surface and the bottom of the algal raceway, thereby affecting algal growth rate. In this work, we investigated the flow mixing performance in a table-sized model of the High Velocity Algae Raceway Integrated Design (ARID-HV). Various geometries of the raceway channels and dams were considered in both the CFD analysis and experimental flowvisualization. In the CFD simulation, the pathlines of fluid particlesweremore » analyzed to obtain the distribution of the number of times that particles passed across a critical water depth, Dc, defined as a cycle count. In addition, the distribution of the time period fraction that the fluid particles stayed in the zones above and below Dc was recorded. Such information was used to evaluate the flow mixing in the raceway. The CFD evaluation of the flow mixing was validated using experimental flow visualization, which showed a good qualitative agreement with the numerical results. In conclusion, this CFD-based evaluation methodology is recommended for flow field optimization for open channel algal raceways, as well as for other engineering applications in which flow mixing is an important concern.« less

Quantifying Instability Sources in Liquid Rocket Engines

NASA Technical Reports Server (NTRS)

Farmer, Richard C.; Cheng, Gary C.

2000-01-01

Computational fluid dynamics methodology to predict the effects of combusting flows on acoustic pressure oscillations in liquid rocket engines (LREs) is under development. 'Me intent of the investigation is to develop the causal physics of combustion driven acoustic resonances in LREs. The crux of the analysis is the accurate simulation of pressure/density/sound speed in a combustor which when used by the FDNS-RFV CFD code will produce realistic flow phenomena. An analysis of a gas generator considered for the Fastrac engine will be used as a test validation case.

Multi-objective parametric optimization of Inertance type pulse tube refrigerator using response surface methodology and non-dominated sorting genetic algorithm

NASA Astrophysics Data System (ADS)

Rout, Sachindra K.; Choudhury, Balaji K.; Sahoo, Ranjit K.; Sarangi, Sunil K.

2014-07-01

The modeling and optimization of a Pulse Tube Refrigerator is a complicated task, due to its complexity of geometry and nature. The aim of the present work is to optimize the dimensions of pulse tube and regenerator for an Inertance-Type Pulse Tube Refrigerator (ITPTR) by using Response Surface Methodology (RSM) and Non-Sorted Genetic Algorithm II (NSGA II). The Box-Behnken design of the response surface methodology is used in an experimental matrix, with four factors and two levels. The diameter and length of the pulse tube and regenerator are chosen as the design variables where the rest of the dimensions and operating conditions of the ITPTR are constant. The required output responses are the cold head temperature (Tcold) and compressor input power (Wcomp). Computational fluid dynamics (CFD) have been used to model and solve the ITPTR. The CFD results agreed well with those of the previously published paper. Also using the results from the 1-D simulation, RSM is conducted to analyse the effect of the independent variables on the responses. To check the accuracy of the model, the analysis of variance (ANOVA) method has been used. Based on the proposed mathematical RSM models a multi-objective optimization study, using the Non-sorted genetic algorithm II (NSGA-II) has been performed to optimize the responses.

Towards an Airframe Noise Prediction Methodology: Survey of Current Approaches

NASA Technical Reports Server (NTRS)

Farassat, Fereidoun; Casper, Jay H.

2006-01-01

In this paper, we present a critical survey of the current airframe noise (AFN) prediction methodologies. Four methodologies are recognized. These are the fully analytic method, CFD combined with the acoustic analogy, the semi-empirical method and fully numerical method. It is argued that for the immediate need of the aircraft industry, the semi-empirical method based on recent high quality acoustic database is the best available method. The method based on CFD and the Ffowcs William- Hawkings (FW-H) equation with penetrable data surface (FW-Hpds ) has advanced considerably and much experience has been gained in its use. However, more research is needed in the near future particularly in the area of turbulence simulation. The fully numerical method will take longer to reach maturity. Based on the current trends, it is predicted that this method will eventually develop into the method of choice. Both the turbulence simulation and propagation methods need to develop more for this method to become useful. Nonetheless, the authors propose that the method based on a combination of numerical and analytical techniques, e.g., CFD combined with FW-H equation, should also be worked on. In this effort, the current symbolic algebra software will allow more analytical approaches to be incorporated into AFN prediction methods.

Computational Analyses in Support of Sub-scale Diffuser Testing for the A-3 Facility. Part 3; Aero-Acoustic Analyses and Experimental Validation

NASA Technical Reports Server (NTRS)

Allgood, Daniel C.; Graham, Jason S.; McVay, Greg P.; Langford, Lester L.

2008-01-01

A unique assessment of acoustic similarity scaling laws and acoustic analogy methodologies in predicting the far-field acoustic signature from a sub-scale altitude rocket test facility at the NASA Stennis Space Center was performed. A directional, point-source similarity analysis was implemented for predicting the acoustic far-field. In this approach, experimental acoustic data obtained from "similar" rocket engine tests were appropriately scaled using key geometric and dynamic parameters. The accuracy of this engineering-level method is discussed by comparing the predictions with acoustic far-field measurements obtained. In addition, a CFD solver was coupled with a Lilley's acoustic analogy formulation to determine the improvement of using a physics-based methodology over an experimental correlation approach. In the current work, steady-state Reynolds-averaged Navier-Stokes calculations were used to model the internal flow of the rocket engine and altitude diffuser. These internal flow simulations provided the necessary realistic input conditions for external plume simulations. The CFD plume simulations were then used to provide the spatial turbulent noise source distributions in the acoustic analogy calculations. Preliminary findings of these studies will be discussed.

SFO-Project: The New Generation of Sharable, Editable and Open-Access CFD Tutorials

NASA Astrophysics Data System (ADS)

Javaherchi, Teymour; Javaherchi, Ardeshir; Aliseda, Alberto

2016-11-01

One of the most common approaches to develop a Computational Fluid Dynamic (CFD) simulation for a new case study of interest is to search for the most similar, previously developed and validated CFD simulation among other works. A simple search would result into a pool of written/visual tutorials. However, users should spend significant amount of time and effort to find the most correct, compatible and valid tutorial in this pool and further modify it toward their simulation of interest. SFO is an open-source project with the core idea of saving the above-mentioned time and effort. This is done via documenting/sharing scientific and methodological approaches to develop CFD simulations for a wide spectrum of fundamental and industrial case studies in three different CFD solvers; STAR-CCM +, FLUENT and Open FOAM (SFO). All of the steps and required files of these tutorials are accessible and editable under the common roof of Github (a web-based Git repository hosting service). In this presentation we will present the current library of 20 + developed CFD tutorials, discuss the idea and benefit of using them, their educational values and explain how the next generation of open-access and live resource of CFD tutorials can be built further hand-in-hand within our community.

Deep Throttle Turbopump Technology Design Concepts

NASA Technical Reports Server (NTRS)

Guinzburg, Adiel; Williams, Morgan; Ferguson, Tom; Garcia, Roberto (Technical Monitor)

2002-01-01

The objective of this project is to increase the throttling range of turbopumps from 30 to 120% of the design value, while maintaining high performance levels. Details are given on wide flow range issues, H-Q characteristics, stall characteristics, energy levels, pressure fluctuations at impeller exit, WFR impeller characteristics, commercial diffuser pumps, slotted or tandem vanes, leading edge characteristics, leading edge models, throat models, diffusion passage models, computational fluid dynamics (CFD) methodologies, and CFD flow cases.

Radiation from advanced solid rocket motor plumes

NASA Technical Reports Server (NTRS)

Farmer, Richard C.; Smith, Sheldon D.; Myruski, Brian L.

1994-01-01

The overall objective of this study was to develop an understanding of solid rocket motor (SRM) plumes in sufficient detail to accurately explain the majority of plume radiation test data. Improved flowfield and radiation analysis codes were developed to accurately and efficiently account for all the factors which effect radiation heating from rocket plumes. These codes were verified by comparing predicted plume behavior with measured NASA/MSFC ASRM test data. Upon conducting a thorough review of the current state-of-the-art of SRM plume flowfield and radiation prediction methodology and the pertinent data base, the following analyses were developed for future design use. The NOZZRAD code was developed for preliminary base heating design and Al2O3 particle optical property data evaluation using a generalized two-flux solution to the radiative transfer equation. The IDARAD code was developed for rapid evaluation of plume radiation effects using the spherical harmonics method of differential approximation to the radiative transfer equation. The FDNS CFD code with fully coupled Euler-Lagrange particle tracking was validated by comparison to predictions made with the industry standard RAMP code for SRM nozzle flowfield analysis. The FDNS code provides the ability to analyze not only rocket nozzle flow, but also axisymmetric and three-dimensional plume flowfields with state-of-the-art CFD methodology. Procedures for conducting meaningful thermo-vision camera studies were developed.

Zero side force volute development

NASA Technical Reports Server (NTRS)

Anderson, P. G.; Franz, R. J.; Farmer, R. C.; Chen, Y. S.

1995-01-01

Collector scrolls on high performance centrifugal pumps are currently designed with methods which are based on very approximate flowfield models. Such design practices result in some volute configurations causing excessive side loads even at design flowrates. The purpose of this study was to develop and verify computational design tools which may be used to optimize volute configurations with respect to avoiding excessive loads on the bearings. The new design methodology consisted of a volute grid generation module and a computational fluid dynamics (CFD) module to describe the volute geometry and predict the radial forces for a given flow condition, respectively. Initially, the CFD module was used to predict the impeller and the volute flowfields simultaneously; however, the required computation time was found to be excessive for parametric design studies. A second computational procedure was developed which utilized an analytical impeller flowfield model and an ordinary differential equation to describe the impeller/volute coupling obtained from the literature, Adkins & Brennen (1988). The second procedure resulted in 20 to 30 fold increase in computational speed for an analysis. The volute design analysis was validated by postulating a volute geometry, constructing a volute to this configuration, and measuring the steady radial forces over a range of flow coefficients. Excellent agreement between model predictions and observed pump operation prove the computational impeller/volute pump model to be a valuable design tool. Further applications are recommended to fully establish the benefits of this new methodology.

Advanced applications of numerical modelling techniques for clay extruder design

NASA Astrophysics Data System (ADS)

Kandasamy, Saravanakumar

Ceramic materials play a vital role in our day to day life. Recent advances in research, manufacture and processing techniques and production methodologies have broadened the scope of ceramic products such as bricks, pipes and tiles, especially in the construction industry. These are mainly manufactured using an extrusion process in auger extruders. During their long history of application in the ceramic industry, most of the design developments of extruder systems have resulted from expensive laboratory-based experimental work and field-based trial and error runs. In spite of these design developments, the auger extruders continue to be energy intensive devices with high operating costs. Limited understanding of the physical process involved in the process and the cost and time requirements of lab-based experiments were found to be the major obstacles in the further development of auger extruders.An attempt has been made herein to use Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) based numerical modelling techniques to reduce the costs and time associated with research into design improvement by experimental trials. These two techniques, although used widely in other engineering applications, have rarely been applied for auger extruder development. This had been due to a number of reasons including technical limitations of CFD tools previously available. Modern CFD and FEA software packages have much enhanced capabilities and allow the modelling of the flow of complex fluids such as clay.This research work presents a methodology in using Herschel-Bulkley's fluid flow based CFD model to simulate and assess the flow of clay-water mixture through the extruder and the die of a vacuum de-airing type clay extrusion unit used in ceramic extrusion. The extruder design and the operating parameters were varied to study their influence on the power consumption and the extrusion pressure. The model results were then validated using results from experimental trials on a scaled extruder which seemed to be in reasonable agreement with the former. The modelling methodology was then extended to full-scale industrial extruders. The technical and commercialsuitability of using light weight materials to manufacture extruder components was also investigated. The stress and deformation induced on the components, due to extrusion pressure, was analysed using FEA and suitable alternative materials were identified. A cost comparison was then made for different extruder materials. The results show potential of significant technical and commercial benefits to the ceramic industry.

Experimental Evaluation of the Thermal Performance of a Water Shield for a Surface Power Reactor

NASA Technical Reports Server (NTRS)

Pearson, J. Boise; Stewart, Eric T.; Reid, Robert S.

2007-01-01

A water based shielding system is being investigated for use on initial lunar surface power systems. The use of water may lower overall cost (as compared to development cost for other materials) and simplify operations in the setup and handling. The thermal hydraulic performance of the shield is of significant interest. The mechanism for transferring heat through the shield is natural convection. Natural convection in a representative lunar surface reactor shield design is evaluated at various power levels in the Water Shield Testbed (WST) at the NASA Marshall Space Flight Center. The experimental data from the WST is used to anchor a CFD model. Performance of a water shield on the lunar surface is then predicted by CFD models anchored to test data. The accompanying viewgraph presentation includes the following topics: 1) Testbed Configuration; 2) Core Heater Placement and Instrumentation; 3) Thermocouple Placement; 4) Core Thermocouple Placement; 5) Outer Tank Thermocouple Placement; 6) Integrated Testbed; 7) Methodology; 8) Experimental Results: Core Temperatures; 9) Experimental Results; Outer Tank Temperatures; 10) CFD Modeling; 11) CFD Model: Anchored to Experimental Results (1-g); 12) CFD MOdel: Prediction for 1/6-g; and 13) CFD Model: Comparison of 1-g to 1/6-g.

Numerical methods for engine-airframe integration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murthy, S.N.B.; Paynter, G.C.

1986-01-01

Various papers on numerical methods for engine-airframe integration are presented. The individual topics considered include: scientific computing environment for the 1980s, overview of prediction of complex turbulent flows, numerical solutions of the compressible Navier-Stokes equations, elements of computational engine/airframe integrations, computational requirements for efficient engine installation, application of CAE and CFD techniques to complete tactical missile design, CFD applications to engine/airframe integration, and application of a second-generation low-order panel methods to powerplant installation studies. Also addressed are: three-dimensional flow analysis of turboprop inlet and nacelle configurations, application of computational methods to the design of large turbofan engine nacelles, comparison ofmore » full potential and Euler solution algorithms for aeropropulsive flow field computations, subsonic/transonic, supersonic nozzle flows and nozzle integration, subsonic/transonic prediction capabilities for nozzle/afterbody configurations, three-dimensional viscous design methodology of supersonic inlet systems for advanced technology aircraft, and a user's technology assessment.« less

Aerodynamic Design and Computational Analysis of a Spacecraft Cabin Ventilation Fan

NASA Technical Reports Server (NTRS)

Tweedt, Daniel L.

2010-01-01

Quieter working environments for astronauts are needed if future long-duration space exploration missions are to be safe and productive. Ventilation and payload cooling fans are known to be dominant sources of noise, with the International Space Station being a good case in point. To address this issue in a cost-effective way, early attention to fan design, selection, and installation has been recommended. Toward that end, NASA has begun to investigate the potential for small-fan noise reduction through improvements in fan aerodynamic design. Using tools and methodologies similar to those employed by the aircraft engine industry, most notably computational fluid dynamics (CFD) codes, the aerodynamic design of a new cabin ventilation fan has been developed, and its aerodynamic performance has been predicted and analyzed. The design, intended to serve as a baseline for future work, is discussed along with selected CFD results

Comprehensive Forced Response Analysis of J2X Turbine Bladed-Discs with 36- Degree Variation in CFD Loading

NASA Technical Reports Server (NTRS)

Elrod, David; Christensen, Eric; Brown, Andrew

2011-01-01

At NASA/MSFC, Structural Dynamics personnel continue to perform advanced analysis for the turbomachinery in the J2X Rocket Engine, which is under consideration for the new Space Launch System. One of the most challenging analyses in the program is predicting turbine blade structural capability. Resonance was predicted by modal analysis, so comprehensive forced response analyses using high fidelity cyclic symmetric finite element models were initiated as required. Analysis methodologies up to this point have assumed the flow field could be fully described by a sector, so the loading on every blade would be identical as it travelled through it. However, in the J2X the CFD flow field varied over the 360 deg of a revolution because of the flow speeds and tortuous axial path. MSFC therefore developed a complex procedure using Nastran Dmap's and Matlab scripts to apply this circumferentially varying loading onto the cyclically symmetric structural models to produce accurate dynamic stresses for every blade on the disk. This procedure is coupled with static, spin, and thermal loading to produce high cycle fatigue safety factors resulting in much more accurate analytical assessments of the blades.

LES, DNS, and RANS for the Analysis of High-Speed Turbulent Reacting Flows

NASA Technical Reports Server (NTRS)

Colucci, P. J.; Jaberi, F. A.; Givi, P.

1996-01-01

A filtered density function (FDF) method suitable for chemically reactive flows is developed in the context of large eddy simulation. The advantage of the FDF methodology is its inherent ability to resolve subgrid scales (SGS) scalar correlations that otherwise have to be modeled. Because of the lack of robust models to accurately predict these correlations in turbulent reactive flows, simulations involving turbulent combustion are often met with a degree of skepticism. The FDF methodology avoids the closure problem associated with these terms and treats the reaction in an exact manner. The scalar FDF approach is particularly attractive since it can be coupled with existing hydrodynamic computational fluid dynamics (CFD) codes.

Propellant Chemistry for CFD Applications

NASA Technical Reports Server (NTRS)

Farmer, R. C.; Anderson, P. G.; Cheng, Gary C.

1996-01-01

Current concepts for reusable launch vehicle design have created renewed interest in the use of RP-1 fuels for high pressure and tri-propellant propulsion systems. Such designs require the use of an analytical technology that accurately accounts for the effects of real fluid properties, combustion of large hydrocarbon fuel modules, and the possibility of soot formation. These effects are inadequately treated in current computational fluid dynamic (CFD) codes used for propulsion system analyses. The objective of this investigation is to provide an accurate analytical description of hydrocarbon combustion thermodynamics and kinetics that is sufficiently computationally efficient to be a practical design tool when used with CFD codes such as the FDNS code. A rigorous description of real fluid properties for RP-1 and its combustion products will be derived from the literature and from experiments conducted in this investigation. Upon the establishment of such a description, the fluid description will be simplified by using the minimum of empiricism necessary to maintain accurate combustion analyses and including such empirical models into an appropriate CFD code. An additional benefit of this approach is that the real fluid properties analysis simplifies the introduction of the effects of droplet sprays into the combustion model. Typical species compositions of RP-1 have been identified, surrogate fuels have been established for analyses, and combustion and sooting reaction kinetics models have been developed. Methods for predicting the necessary real fluid properties have been developed and essential experiments have been designed. Verification studies are in progress, and preliminary results from these studies will be presented. The approach has been determined to be feasible, and upon its completion the required methodology for accurate performance and heat transfer CFD analyses for high pressure, tri-propellant propulsion systems will be available.

Automated Tetrahedral Mesh Generation for CFD Analysis of Aircraft in Conceptual Design

NASA Technical Reports Server (NTRS)

Ordaz, Irian; Li, Wu; Campbell, Richard L.

2014-01-01

The paper introduces an automation process of generating a tetrahedral mesh for computational fluid dynamics (CFD) analysis of aircraft configurations in early conceptual design. The method was developed for CFD-based sonic boom analysis of supersonic configurations, but can be applied to aerodynamic analysis of aircraft configurations in any flight regime.

Application of Reduced Order Transonic Aerodynamic Influence Coefficient Matrix for Design Optimization

NASA Technical Reports Server (NTRS)

Pak, Chan-gi; Li, Wesley W.

2009-01-01

Supporting the Aeronautics Research Mission Directorate guidelines, the National Aeronautics and Space Administration [NASA] Dryden Flight Research Center is developing a multidisciplinary design, analysis, and optimization [MDAO] tool. This tool will leverage existing tools and practices, and allow the easy integration and adoption of new state-of-the-art software. Today s modern aircraft designs in transonic speed are a challenging task due to the computation time required for the unsteady aeroelastic analysis using a Computational Fluid Dynamics [CFD] code. Design approaches in this speed regime are mainly based on the manual trial and error. Because of the time required for unsteady CFD computations in time-domain, this will considerably slow down the whole design process. These analyses are usually performed repeatedly to optimize the final design. As a result, there is considerable motivation to be able to perform aeroelastic calculations more quickly and inexpensively. This paper will describe the development of unsteady transonic aeroelastic design methodology for design optimization using reduced modeling method and unsteady aerodynamic approximation. The method requires the unsteady transonic aerodynamics be represented in the frequency or Laplace domain. Dynamically linear assumption is used for creating Aerodynamic Influence Coefficient [AIC] matrices in transonic speed regime. Unsteady CFD computations are needed for the important columns of an AIC matrix which corresponded to the primary modes for the flutter. Order reduction techniques, such as Guyan reduction and improved reduction system, are used to reduce the size of problem transonic flutter can be found by the classic methods, such as Rational function approximation, p-k, p, root-locus etc. Such a methodology could be incorporated into MDAO tool for design optimization at a reasonable computational cost. The proposed technique is verified using the Aerostructures Test Wing 2 actually designed, built, and tested at NASA Dryden Flight Research Center. The results from the full order model and the approximate reduced order model are analyzed and compared.

Integration of Engine, Plume, and CFD Analyses in Conceptual Design of Low-Boom Supersonic Aircraft

NASA Technical Reports Server (NTRS)

Li, Wu; Campbell, Richard; Geiselhart, Karl; Shields, Elwood; Nayani, Sudheer; Shenoy, Rajiv

2009-01-01

This paper documents an integration of engine, plume, and computational fluid dynamics (CFD) analyses in the conceptual design of low-boom supersonic aircraft, using a variable fidelity approach. In particular, the Numerical Propulsion Simulation System (NPSS) is used for propulsion system cycle analysis and nacelle outer mold line definition, and a low-fidelity plume model is developed for plume shape prediction based on NPSS engine data and nacelle geometry. This model provides a capability for the conceptual design of low-boom supersonic aircraft that accounts for plume effects. Then a newly developed process for automated CFD analysis is presented for CFD-based plume and boom analyses of the conceptual geometry. Five test cases are used to demonstrate the integrated engine, plume, and CFD analysis process based on a variable fidelity approach, as well as the feasibility of the automated CFD plume and boom analysis capability.

F-16XL-2 Supersonic Laminar Flow Control Flight Test Experiment

NASA Technical Reports Server (NTRS)

Anders, Scott G.; Fischer, Michael C.

1999-01-01

The F-16XL-2 Supersonic Laminar Flow Control Flight Test Experiment was part of the NASA High-Speed Research Program. The goal of the experiment was to demonstrate extensive laminar flow, to validate computational fluid dynamics (CFD) codes and design methodology, and to establish laminar flow control design criteria. Topics include the flight test hardware and design, airplane modification, the pressure and suction distributions achieved, the laminar flow achieved, and the data analysis and code correlation.

Computational System For Rapid CFD Analysis In Engineering

NASA Technical Reports Server (NTRS)

Barson, Steven L.; Ascoli, Edward P.; Decroix, Michelle E.; Sindir, Munir M.

1995-01-01

Computational system comprising modular hardware and software sub-systems developed to accelerate and facilitate use of techniques of computational fluid dynamics (CFD) in engineering environment. Addresses integration of all aspects of CFD analysis process, including definition of hardware surfaces, generation of computational grids, CFD flow solution, and postprocessing. Incorporates interfaces for integration of all hardware and software tools needed to perform complete CFD analysis. Includes tools for efficient definition of flow geometry, generation of computational grids, computation of flows on grids, and postprocessing of flow data. System accepts geometric input from any of three basic sources: computer-aided design (CAD), computer-aided engineering (CAE), or definition by user.

Enhancement of CFD validation exercise along the roof profile of a low-rise building

NASA Astrophysics Data System (ADS)

Deraman, S. N. C.; Majid, T. A.; Zaini, S. S.; Yahya, W. N. W.; Abdullah, J.; Ismail, M. A.

2018-04-01

The aim of this study is to enhance the validation of CFD exercise along the roof profile of a low-rise building. An isolated gabled-roof house having 26.6° roof pitch was simulated to obtain the pressure coefficient around the house. Validation of CFD analysis with experimental data requires many input parameters. This study performed CFD simulation based on the data from a previous study. Where the input parameters were not clearly stated, new input parameters were established from the open literatures. The numerical simulations were performed in FLUENT 14.0 by applying the Computational Fluid Dynamics (CFD) approach based on steady RANS equation together with RNG k-ɛ model. Hence, the result from CFD was analysed by using quantitative test (statistical analysis) and compared with CFD results from the previous study. The statistical analysis results from ANOVA test and error measure showed that the CFD results from the current study produced good agreement and exhibited the closest error compared to the previous study. All the input data used in this study can be extended to other types of CFD simulation involving wind flow over an isolated single storey house.

Rapid Airplane Parametric Input Design (RAPID)

NASA Technical Reports Server (NTRS)

Smith, Robert E.

1995-01-01

RAPID is a methodology and software system to define a class of airplane configurations and directly evaluate surface grids, volume grids, and grid sensitivity on and about the configurations. A distinguishing characteristic which separates RAPID from other airplane surface modellers is that the output grids and grid sensitivity are directly applicable in CFD analysis. A small set of design parameters and grid control parameters govern the process which is incorporated into interactive software for 'real time' visual analysis and into batch software for the application of optimization technology. The computed surface grids and volume grids are suitable for a wide range of Computational Fluid Dynamics (CFD) simulation. The general airplane configuration has wing, fuselage, horizontal tail, and vertical tail components. The double-delta wing and tail components are manifested by solving a fourth order partial differential equation (PDE) subject to Dirichlet and Neumann boundary conditions. The design parameters are incorporated into the boundary conditions and therefore govern the shapes of the surfaces. The PDE solution yields a smooth transition between boundaries. Surface grids suitable for CFD calculation are created by establishing an H-type topology about the configuration and incorporating grid spacing functions in the PDE equation for the lifting components and the fuselage definition equations. User specified grid parameters govern the location and degree of grid concentration. A two-block volume grid about a configuration is calculated using the Control Point Form (CPF) technique. The interactive software, which runs on Silicon Graphics IRIS workstations, allows design parameters to be continuously varied and the resulting surface grid to be observed in real time. The batch software computes both the surface and volume grids and also computes the sensitivity of the output grid with respect to the input design parameters by applying the precompiler tool ADIFOR to the grid generation program. The output of ADIFOR is a new source code containing the old code plus expressions for derivatives of specified dependent variables (grid coordinates) with respect to specified independent variables (design parameters). The RAPID methodology and software provide a means of rapidly defining numerical prototypes, grids, and grid sensitivity of a class of airplane configurations. This technology and software is highly useful for CFD research for preliminary design and optimization processes.

Three-dimensional aerodynamic shape optimization of supersonic delta wings

NASA Technical Reports Server (NTRS)

Burgreen, Greg W.; Baysal, Oktay

1994-01-01

A recently developed three-dimensional aerodynamic shape optimization procedure AeSOP(sub 3D) is described. This procedure incorporates some of the most promising concepts from the area of computational aerodynamic analysis and design, specifically, discrete sensitivity analysis, a fully implicit 3D Computational Fluid Dynamics (CFD) methodology, and 3D Bezier-Bernstein surface parameterizations. The new procedure is demonstrated in the preliminary design of supersonic delta wings. Starting from a symmetric clipped delta wing geometry, a Mach 1.62 asymmetric delta wing and two Mach 1. 5 cranked delta wings were designed subject to various aerodynamic and geometric constraints.

Wall jet analysis for circulation control aerodynamics. Part 1: Fundamental CFD and turbulence modeling concepts

NASA Technical Reports Server (NTRS)

Dash, S. M.; York, B. J.; Sinha, N.; Dvorak, F. A.

1987-01-01

An overview of parabolic and PNS (Parabolized Navier-Stokes) methodology developed to treat highly curved sub and supersonic wall jets is presented. The fundamental data base to which these models were applied is discussed in detail. The analysis of strong curvature effects was found to require a semi-elliptic extension of the parabolic modeling to account for turbulent contributions to the normal pressure variations, as well as an extension to the turbulence models utilized, to account for the highly enhanced mixing rates observed in situations with large convex curvature. A noniterative, pressure split procedure is shown to extend parabolic models to account for such normal pressure variations in an efficient manner, requiring minimal additional run time over a standard parabolic approach. A new PNS methodology is presented to solve this problem which extends parabolic methodology via the addition of a characteristic base wave solver. Applications of this approach to analyze the interaction of wave and turbulence processes in wall jets is presented.

Patient specific CFD models of nasal airflow: overview of methods and challenges.

PubMed

Kim, Sung Kyun; Na, Yang; Kim, Jee-In; Chung, Seung-Kyu

2013-01-18

Respiratory physiology and pathology are strongly dependent on the airflow inside the nasal cavity. However, the nasal anatomy, which is characterized by complex airway channels and significant individual differences, is difficult to analyze. Thus, commonly adopted diagnostic tools have yielded limited success. Nevertheless, with the rapid advances in computer resources, there have been more elaborate attempts to correlate airflow characteristics in human nasal airways with the symptoms and functions of the nose by computational fluid dynamics study. Furthermore, the computed nasal geometry can be virtually modified to reflect predicted results of the proposed surgical technique. In this article, several computational fluid mechanics (CFD) issues on patient-specific three dimensional (3D) modeling of nasal cavity and clinical applications were reviewed in relation to the cases of deviated nasal septum (decision for surgery), turbinectomy, and maxillary sinus ventilation (simulated- and post-surgery). Clinical relevance of fluid mechanical parameters, such as nasal resistance, flow allocation, wall shear stress, heat/humidity/NO gas distributions, to the symptoms and surgical outcome were discussed. Absolute values of such parameters reported by many research groups were different each other due to individual difference of nasal anatomy, the methodology for 3D modeling and numerical grid, laminar/turbulent flow model in CFD code. But, the correlation of these parameters to symptoms and surgery outcome seems to be obvious in each research group with subject-specific models and its variations (virtual- and post-surgery models). For the more reliable, patient-specific, and objective tools for diagnosis and outcomes of nasal surgery by using CFD, the future challenges will be the standardizations on the methodology for creating 3D airway models and the CFD procedures. Copyright © 2012 Elsevier Ltd. All rights reserved.

Comprehensive Approach to Verification and Validation of CFD Simulations Applied to Backward Facing Step-Application of CFD Uncertainty Analysis

NASA Technical Reports Server (NTRS)

Groves, Curtis E.; LLie, Marcel; Shallhorn, Paul A.

2012-01-01

There are inherent uncertainties and errors associated with using Computational Fluid Dynamics (CFD) to predict the flow field and there is no standard method for evaluating uncertainty in the CFD community. This paper describes an approach to -validate the . uncertainty in using CFD. The method will use the state of the art uncertainty analysis applying different turbulence niodels and draw conclusions on which models provide the least uncertainty and which models most accurately predict the flow of a backward facing step.

CFD to Flight: Some Recent Success Stories of X-Plane Design to Flight Test at the NASA Dryden Flight Research Center

NASA Technical Reports Server (NTRS)

Cosentino, Gary B.

2007-01-01

Several examples from the past decade of success stories involving the design and flight test of three true X-planes will be described: in particular, X-plane design techniques that relied heavily upon computational fluid dynamics (CFD). Three specific examples chosen from the author s personal experience are presented: the X-36 Tailless Fighter Agility Research Aircraft, the X-45A Unmanned Combat Air Vehicle, and, most recently, the X-48B Blended Wing Body Demonstrator Aircraft. An overview will be presented of the uses of CFD analysis, comparisons and contrasts with wind tunnel testing, and information derived from the CFD analysis that directly related to successful flight test. Some lessons learned on the proper application, and misapplication, of CFD are illustrated. Finally, some highlights of the flight-test results of the three example X-planes will be presented. This overview paper will discuss some of the author s experience with taking an aircraft shape from early concept and three-dimensional modeling through CFD analysis, wind tunnel testing, further refined CFD analysis, and, finally, flight. An overview of the key roles in which CFD plays well during this process, and some other roles in which it does not, are discussed. How wind tunnel testing complements, calibrates, and verifies CFD analysis is also covered. Lessons learned on where CFD results can be misleading are also given. Strengths and weaknesses of the various types of flow solvers, including panel methods, Euler, and Navier-Stokes techniques, are discussed. The paper concludes with the three specific examples, including some flight test video footage of the X-36, the X-45A, and the X-48B.

CFD to Flight: Some Recent Success Stories of X-plane Design to Flight Test at the NASA Dryden Flight Research Center

NASA Technical Reports Server (NTRS)

Cosentino, Gary B.

2007-01-01

Several examples from the past decade of success stories involving the design and ight test of three true X-planes will be described: in particular, X-plane design techniques that relied heavily upon computational fluid dynamics (CFD). Three specific examples chosen from the authors personal experience are presented: the X-36 Tailless Fighter Agility Research Aircraft, the X-45A Unmanned Combat Air Vehicle, and, most recently, the X-48B Blended Wing Body Demonstrator Aircraft. An overview will be presented of the uses of CFD analysis, comparisons and contrasts with wind tunnel testing, and information derived from the CFD analysis that directly related to successful flight test. Some lessons learned on the proper application, and misapplication, of CFD are illustrated. Finally, some highlights of the flight-test results of the three example X-planes will be presented. This overview paper will discuss some of the authors experience with taking an aircraft shape from early concept and three-dimensional modeling through CFD analysis, wind tunnel testing, further re ned CFD analysis, and, finally, flight. An overview of the key roles in which CFD plays well during this process, and some other roles in which it does not, are discussed. How wind tunnel testing complements, calibrates, and verifies CFD analysis is also covered. Lessons learned on where CFD results can be misleading are also given. Strengths and weaknesses of the various types of ow solvers, including panel methods, Euler, and Navier-Stokes techniques, are discussed. The paper concludes with the three specific examples, including some flight test video footage of the X-36, the X-45A, and the X-48B.

An integrated CFD/experimental analysis of aerodynamic forces and moments

NASA Technical Reports Server (NTRS)

Melton, John E.; Robertson, David D.; Moyer, Seth A.

1989-01-01

Aerodynamic analysis using computational fluid dynamics (CFD) is most fruitful when it is combined with a thorough program of wind tunnel testing. The understanding of aerodynamic phenomena is enhanced by the synergistic use of both analysis methods. A technique is described for an integrated approach to determining the forces and moments acting on a wind tunnel model by using a combination of experimentally measured pressures and CFD predictions. The CFD code used was FLO57 (an Euler solver) and the wind tunnel model was a heavily instrumented delta wing with 62.5 deg of leading-edge sweep. A thorough comparison of the CFD results and the experimental data is presented for surface pressure distributions and longitudinal forces and moments. The experimental pressures were also integrated over the surface of the model and the resulting forces and moments are compared to the CFD and wind tunnel results. The accurate determination of various drag increments via the combined use of the CFD and experimental pressures is presented in detail.

Development of a Aerothermoelastic-Acoustics Simulation Capability of Flight Vehicles

NASA Technical Reports Server (NTRS)

Gupta, K. K.; Choi, S. B.; Ibrahim, A.

2010-01-01

A novel numerical, finite element based analysis methodology is presented in this paper suitable for accurate and efficient simulation of practical, complex flight vehicles. An associated computer code, developed in this connection, is also described in some detail. Thermal effects of high speed flow obtained from a heat conduction analysis are incorporated in the modal analysis which in turn affects the unsteady flow arising out of interaction of elastic structures with the air. Numerical examples pertaining to representative problems are given in much detail testifying to the efficacy of the advocated techniques. This is a unique implementation of temperature effects in a finite element CFD based multidisciplinary simulation analysis capability involving large scale computations.

CFD methodology and validation for turbomachinery flows

NASA Astrophysics Data System (ADS)

Hirsch, Ch.

1994-05-01

The essential problem today, in the application of 3D Navier-Stokes simulations to the design and analysis of turbomachinery components, is the validation of the numerical approximation and of the physical models, in particular the turbulence modelling. Although most of the complex 3D flow phenomena occurring in turbomachinery bladings can be captured with relatively coarse meshes, many detailed flow features are dependent on mesh size, on the turbulence and transition models. A brief review of the present state of the art of CFD methodology is given with emphasis on quality and accuracy of numerical approximations related to viscous flow computations. Considerations related to the mesh influence on solution accuracy are stressed. The basic problems of turbulence and transition modelling are discussed next, with a short summary of the main turbulence models and their applications to representative turbomachinery flows. Validations of present turbulence models indicate that none of the available turbulence models is able to predict all the detailed flow behavior in complex flow interactions. In order to identify the phenomena that can be captured on coarser meshes a detailed understanding of the complex 3D flow in compressor and turbines is necessary. Examples of global validations for different flow configurations, representative of compressor and turbine aerodynamics are presented, including secondary and tip clearance flows.

Towards Rocket Engine Components with Increased Strength and Robust Operating Characteristics

NASA Technical Reports Server (NTRS)

Marcu, Bogdan; Hadid, Ali; Lin, Pei; Balcazar, Daniel; Rai, Man Mohan; Dorney, Daniel J.

2005-01-01

High-energy rotating machines, powering liquid propellant rocket engines, are subject to various sources of high and low cycle fatigue generated by unsteady flow phenomena. Given the tremendous need for reliability in a sustainable space exploration program, a fundamental change in the design methodology for engine components is required for both launch and space based systems. A design optimization system based on neural-networks has been applied and demonstrated in the redesign of the Space Shuttle Main Engine (SSME) Low Pressure Oxidizer Turbo Pump (LPOTP) turbine nozzle. One objective of the redesign effort was to increase airfoil thickness and thus increase its strength while at the same time detuning the vane natural frequency modes from the vortex shedding frequency. The second objective was to reduce the vortex shedding amplitude. The third objective was to maintain this low shedding amplitude even in the presence of large manufacturing tolerances. All of these objectives were achieved without generating any detrimental effects on the downstream flow through the turbine, and without introducing any penalty in performance. The airfoil redesign and preliminary assessment was performed in the Exploration Technology Directorate at NASA ARC. Boeing/Rocketdyne and NASA MSFC independently performed final CFD assessments of the design. Four different CFD codes were used in this process. They include WIL DCA T/CORSAIR (NASA), FLUENT (commercial), TIDAL (Boeing Rocketdyne) and, a new family (AardvarWPhantom) of CFD analysis codes developed at NASA MSFC employing LOX fluid properties and a Generalized Equation Set formulation. Extensive aerodynamic performance analysis and stress analysis carried out at Boeing Rocketdyne and NASA MSFC indicate that the redesign objectives have been fully met. The paper presents the results of the assessment analysis and discusses the future potential of robust optimal design for rocket engine components.

An Approach to Improved Credibility of CFD Simulations for Rocket Injector Design

NASA Technical Reports Server (NTRS)

Tucker, Paul K.; Menon, Suresh; Merkle, Charles L.; Oefelein, Joseph C.; Yang, Vigor

2007-01-01

Computational fluid dynamics (CFD) has the potential to improve the historical rocket injector design process by simulating the sensitivity of performance and injector-driven thermal environments to. the details of the injector geometry and key operational parameters. Methodical verification and validation efforts on a range of coaxial injector elements have shown the current production CFD capability must be improved in order to quantitatively impact the injector design process.. This paper documents the status of an effort to understand and compare the predictive capabilities and resource requirements of a range of CFD methodologies on a set of model problem injectors. Preliminary results from a steady Reynolds-Average Navier-Stokes (RANS), an unsteady Reynolds-Average Navier Stokes (URANS) and three different Large Eddy Simulation (LES) techniques used to model a single element coaxial injector using gaseous oxygen and gaseous hydrogen propellants are presented. Initial observations are made comparing instantaneous results, corresponding time-averaged and steady-state solutions in the near -injector flow field. Significant differences in the flow fields exist, as expected, and are discussed. An important preliminary result is the identification of a fundamental mixing mechanism, accounted for by URANS and LES, but missing in the steady BANS methodology. Since propellant mixing is the core injector function, this mixing process may prove to have a profound effect on the ability to more correctly simulate injector performance and resulting thermal environments. Issues important to unifying the basis for future comparison such as solution initialization, required run time and grid resolution are addressed.

A CFD study on the effectiveness of trees to disperse road traffic emissions at a city scale

NASA Astrophysics Data System (ADS)

Jeanjean, A. P. R.; Hinchliffe, G.; McMullan, W. A.; Monks, P. S.; Leigh, R. J.

2015-11-01

This paper focuses on the effectiveness of trees at dispersing road traffic emissions on a city scale. CFD simulations of air-pollutant concentrations were performed using the OpenFOAM software platform using the k-ε model. Results were validated against the CODASC wind tunnel database before being applied to a LIDAR database of buildings and trees representing the City of Leicester (UK). Most other CFD models in the literature typically use idealised buildings to model wind flow and pollution dispersion. However, the methodology used in this study uses real buildings and trees data from LIDAR to reconstruct a 3D representation of Leicester City Centre. It focuses on a 2 × 2 km area which is on a scale larger than those usually used in other CFD studies. Furthermore, the primary focus of this study is on the interaction of trees with wind flow dynamics. It was found that in effect, trees have a regionally beneficial impact on road traffic emissions by increasing turbulence and reducing ambient concentrations of road traffic emissions by 7% at pedestrian height on average. This was an important result given that previous studies generally concluded that trees trapped pollution by obstructing wind flow in street canyons. Therefore, this study is novel both in its methodology and subsequent results, highlighting the importance of combining local and regional scale models for assessing the impact of trees in urban planning.

Highly Efficient Design-of-Experiments Methods for Combining CFD Analysis and Experimental Data

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Haller, Harold S.

2009-01-01

It is the purpose of this study to examine the impact of "highly efficient" Design-of-Experiments (DOE) methods for combining sets of CFD generated analysis data with smaller sets of Experimental test data in order to accurately predict performance results where experimental test data were not obtained. The study examines the impact of micro-ramp flow control on the shock wave boundary layer (SWBL) interaction where a complete paired set of data exist from both CFD analysis and Experimental measurements By combining the complete set of CFD analysis data composed of fifteen (15) cases with a smaller subset of experimental test data containing four/five (4/5) cases, compound data sets (CFD/EXP) were generated which allows the prediction of the complete set of Experimental results No statistical difference were found to exist between the combined (CFD/EXP) generated data sets and the complete Experimental data set composed of fifteen (15) cases. The same optimal micro-ramp configuration was obtained using the (CFD/EXP) generated data as obtained with the complete set of Experimental data, and the DOE response surfaces generated by the two data sets were also not statistically different.

CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff

2015-01-01

Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

Computer Aided Grid Interface: An Interactive CFD Pre-Processor

NASA Technical Reports Server (NTRS)

Soni, Bharat K.

1997-01-01

NASA maintains an applications oriented computational fluid dynamics (CFD) efforts complementary to and in support of the aerodynamic-propulsion design and test activities. This is especially true at NASA/MSFC where the goal is to advance and optimize present and future liquid-fueled rocket engines. Numerical grid generation plays a significant role in the fluid flow simulations utilizing CFD. An overall goal of the current project was to develop a geometry-grid generation tool that will help engineers, scientists and CFD practitioners to analyze design problems involving complex geometries in a timely fashion. This goal is accomplished by developing the CAGI: Computer Aided Grid Interface system. The CAGI system is developed by integrating CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) geometric system output and/or Initial Graphics Exchange Specification (IGES) files (including all the NASA-IGES entities), geometry manipulations and generations associated with grid constructions, and robust grid generation methodologies. This report describes the development process of the CAGI system.

Computer Aided Grid Interface: An Interactive CFD Pre-Processor

NASA Technical Reports Server (NTRS)

Soni, Bharat K.

1996-01-01

NASA maintains an applications oriented computational fluid dynamics (CFD) efforts complementary to and in support of the aerodynamic-propulsion design and test activities. This is especially true at NASA/MSFC where the goal is to advance and optimize present and future liquid-fueled rocket engines. Numerical grid generation plays a significant role in the fluid flow simulations utilizing CFD. An overall goal of the current project was to develop a geometry-grid generation tool that will help engineers, scientists and CFD practitioners to analyze design problems involving complex geometries in a timely fashion. This goal is accomplished by developing the Computer Aided Grid Interface system (CAGI). The CAGI system is developed by integrating CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) geometric system output and / or Initial Graphics Exchange Specification (IGES) files (including all the NASA-IGES entities), geometry manipulations and generations associated with grid constructions, and robust grid generation methodologies. This report describes the development process of the CAGI system.

Modelling NOX concentrations through CFD-RANS in an urban hot-spot using high resolution traffic emissions and meteorology from a mesoscale model

NASA Astrophysics Data System (ADS)

Sanchez, Beatriz; Santiago, Jose Luis; Martilli, Alberto; Martin, Fernando; Borge, Rafael; Quaassdorff, Christina; de la Paz, David

2017-08-01

Air quality management requires more detailed studies about air pollution at urban and local scale over long periods of time. This work focuses on obtaining the spatial distribution of NOx concentration averaged over several days in a heavily trafficked urban area in Madrid (Spain) using a computational fluid dynamics (CFD) model. A methodology based on weighted average of CFD simulations is applied computing the time evolution of NOx dispersion as a sequence of steady-state scenarios taking into account the actual atmospheric conditions. The inputs of emissions are estimated from the traffic emission model and the meteorological information used is derived from a mesoscale model. Finally, the computed concentration map correlates well with 72 passive samplers deployed in the research area. This work reveals the potential of using urban mesoscale simulations together with detailed traffic emissions so as to provide accurate maps of pollutant concentration at microscale using CFD simulations.

Computational fluid dynamics research at the United Technologies Research Center requiring supercomputers

NASA Astrophysics Data System (ADS)

Landgrebe, Anton J.

1987-03-01

An overview of research activities at the United Technologies Research Center (UTRC) in the area of Computational Fluid Dynamics (CFD) is presented. The requirement and use of various levels of computers, including supercomputers, for the CFD activities is described. Examples of CFD directed toward applications to helicopters, turbomachinery, heat exchangers, and the National Aerospace Plane are included. Helicopter rotor codes for the prediction of rotor and fuselage flow fields and airloads were developed with emphasis on rotor wake modeling. Airflow and airload predictions and comparisons with experimental data are presented. Examples are presented of recent parabolized Navier-Stokes and full Navier-Stokes solutions for hypersonic shock-wave/boundary layer interaction, and hydrogen/air supersonic combustion. In addition, other examples of CFD efforts in turbomachinery Navier-Stokes methodology and separated flow modeling are presented. A brief discussion of the 3-tier scientific computing environment is also presented, in which the researcher has access to workstations, mid-size computers, and supercomputers.

Computational fluid dynamics research at the United Technologies Research Center requiring supercomputers

NASA Technical Reports Server (NTRS)

Landgrebe, Anton J.

1987-01-01

An overview of research activities at the United Technologies Research Center (UTRC) in the area of Computational Fluid Dynamics (CFD) is presented. The requirement and use of various levels of computers, including supercomputers, for the CFD activities is described. Examples of CFD directed toward applications to helicopters, turbomachinery, heat exchangers, and the National Aerospace Plane are included. Helicopter rotor codes for the prediction of rotor and fuselage flow fields and airloads were developed with emphasis on rotor wake modeling. Airflow and airload predictions and comparisons with experimental data are presented. Examples are presented of recent parabolized Navier-Stokes and full Navier-Stokes solutions for hypersonic shock-wave/boundary layer interaction, and hydrogen/air supersonic combustion. In addition, other examples of CFD efforts in turbomachinery Navier-Stokes methodology and separated flow modeling are presented. A brief discussion of the 3-tier scientific computing environment is also presented, in which the researcher has access to workstations, mid-size computers, and supercomputers.

Estimation of pressure gradients at renal artery stenoses

NASA Astrophysics Data System (ADS)

Yim, Peter J.; Cebral, Juan R.; Weaver, Ashley; Lutz, Robert J.; Vasbinder, G. Boudewijn C.

2003-05-01

Atherosclerotic disease of the renal artery can reduce the blood flow leading to renovascular hypertension and ischemic nephopathy. The kidney responds to a decrease in blood flow by activation of the renin-angiotensin system that increases blood pressure and can result in severe hypertension. Percutaneous translumenal angioplasty (PTA) may be indicated for treatment of renovascular hypertension (RVH). However, direct measurement of renal artery caliber and degree of stenosis has only moderate specificity for detection of RVH. A confounding factor in assessment of the proximal renal artery is that diffuse atherosclerotic disease of the distal branches of the renal artery can produce the same effect on blood-flow as atherosclerotic disease of the proximal renal artery. A methodology is proposed for estimation of pressure gradients at renal artery stenoses from magnetic resonance imaging that could improve the evaluation of renal artery disease. In the proposed methodology, pressure gradients are estimated using computational fluid dynamics (CFD) modeling. Realistic CFD models are constructed from images of vessel shape and measurements of blood-flow rates which are available from magnetic resonance angiography (MRA) and phase-contrast magnetic resonance (MR) imaging respectively. CFD measurement of renal artery pressure gradients has been validated in a physical flow-through model.

Complement Factor D in Age-Related Macular Degeneration

PubMed Central

Stanton, Chloe M.; Yates, John R.W.; den Hollander, Anneke I.; Seddon, Johanna M.; Swaroop, Anand; Stambolian, Dwight; Fauser, Sascha; Hoyng, Carel; Yu, Yi; Atsuhiro, Kanda; Branham, Kari; Othman, Mohammad; Chen, Wei; Kortvely, Elod; Chalmers, Kevin; Hayward, Caroline; Moore, Anthony T.; Dhillon, Baljean; Ueffing, Marius

2011-01-01

Purpose. To examine the role of complement factor D (CFD) in age-related macular degeneration (AMD) by analysis of genetic association, copy number variation, and plasma CFD concentrations. Methods. Single nucleotide polymorphisms (SNPs) in the CFD gene were genotyped and the results analyzed by binary logistic regression. CFD gene copy number was analyzed by gene copy number assay. Plasma CFD was measured by an enzyme-linked immunosorbent assay. Results. Genetic association was found between CFD gene SNP rs3826945 and AMD (odds ratio 1.44; P = 0.028) in a small discovery case-control series (462 cases and 325 controls) and replicated in a combined cohorts meta-analysis of 4765 cases and 2693 controls, with an odds ratio of 1.11 (P = 0.032), with the association almost confined to females. Copy number variation in the CFD gene was identified in 13 out of 640 samples examined but there was no difference in frequency between AMD cases (1.3%) and controls (2.7%). Plasma CFD concentration was measured in 751 AMD cases and 474 controls and found to be elevated in AMD cases (P = 0.00025). The odds ratio for those in the highest versus lowest quartile for plasma CFD was 1.81. The difference in plasma CFD was again almost confined to females. Conclusions. CFD regulates activation of the alternative complement pathway, which is implicated in AMD pathogenesis. The authors found evidence for genetic association between a CFD gene SNP and AMD and a significant increase in plasma CFD concentration in AMD cases compared with controls, consistent with a role for CFD in AMD pathogenesis. PMID:22003108

Computational Fluid Dynamics (CFD) Analysis Of Optical Payload For Lasercomm Science (OPALS) sealed enclosure module

NASA Technical Reports Server (NTRS)

Anderson, Kevin R.; Zayas, Daniel; Turner, Daniel

2012-01-01

Computational Fluid Dynamics (CFD) using the commercial CFD package CFDesign has been performed at NASA Jet Propulsion Laboratory (JPL) California Institute of Technology (Caltech) in support of the Phaeton Early Career Hire Program's Optical Payload for Lasercomm Science (OPALS) mission. The OPALS project is one which involves an International Space Station payload that will be using forced convection cooling in a hermetically sealed enclosure at 1 atm of air to cool "off-the-shelf" vendor electronics. The CFD analysis was used to characterize the thermal and fluid flow environment within a complicated labyrinth of electronics boards, fans, instrumentation, harnessing, ductwork and heat exchanger fins. The paradigm of iteratively using CAD/CAE tools and CFD was followed in order to determine the optimum flow geometry and heat sink configuration to yield operational convective film coefficients and temperature survivability limits for the electronics payload. Results from this current CFD analysis and correlation of the CFD model against thermal test data will be presented. Lessons learned and coupled thermal / flow modeling strategies will be shared in this paper.

CFD simulation of a 2 bladed multi megawatt wind turbine with flexible rotor connection

NASA Astrophysics Data System (ADS)

Klein, L.; Luhmann, B.; Rösch, K.-N.; Lutz, T.; Cheng, P.-W.; Krämer, E.

2016-09-01

An innovative passive load reduction concept for a two bladed 3.4 MW wind turbine is investigated by a conjoint CFD and MBS - BEM methodology. The concept consists of a flexible hub mount which allows a tumbling motion of the rotor. First, the system is simulated with a MBS tool coupled to a BEM code. Then, the resulting motion of the rotor is extracted from the simulation and applied on the CFD simulation as prescribed motion. The aerodynamic results show a significant load reduction on the support structure. Hub pitching and yawing moment amplitudes are reduced by more than 50% in a vertically sheared inflow. Furthermore, the suitability of the MBS - BEM approach for the simulation of the load reduction system is shown.

Propulsion integration of hypersonic air-breathing vehicles utilizing a top-down design methodology

NASA Astrophysics Data System (ADS)

Kirkpatrick, Brad Kenneth

In recent years, a focus of aerospace engineering design has been the development of advanced design methodologies and frameworks to account for increasingly complex and integrated vehicles. Techniques such as parametric modeling, global vehicle analyses, and interdisciplinary data sharing have been employed in an attempt to improve the design process. The purpose of this study is to introduce a new approach to integrated vehicle design known as the top-down design methodology. In the top-down design methodology, the main idea is to relate design changes on the vehicle system and sub-system level to a set of over-arching performance and customer requirements. Rather than focusing on the performance of an individual system, the system is analyzed in terms of the net effect it has on the overall vehicle and other vehicle systems. This detailed level of analysis can only be accomplished through the use of high fidelity computational tools such as Computational Fluid Dynamics (CFD) or Finite Element Analysis (FEA). The utility of the top-down design methodology is investigated through its application to the conceptual and preliminary design of a long-range hypersonic air-breathing vehicle for a hypothetical next generation hypersonic vehicle (NHRV) program. System-level design is demonstrated through the development of the nozzle section of the propulsion system. From this demonstration of the methodology, conclusions are made about the benefits, drawbacks, and cost of using the methodology.

Transonic propulsion system integration analysis at McDonnell Aircraft Company

NASA Technical Reports Server (NTRS)

Cosner, Raymond R.

1989-01-01

The technology of Computational Fluid Dynamics (CFD) is becoming an important tool in the development of aircraft propulsion systems. Two of the most valuable features of CFD are: (1) quick acquisition of flow field data; and (2) complete description of flow fields, allowing detailed investigation of interactions. Current analysis methods complement wind tunnel testing in several ways. Herein, the discussion is focused on CFD methods. However, aircraft design studies need data from both CFD and wind tunnel testing. Each approach complements the other.

Study of water based nanofluid flows in annular tubes using numerical simulation and sensitivity analysis

NASA Astrophysics Data System (ADS)

Siadaty, Moein; Kazazi, Mohsen

2018-04-01

Convective heat transfer, entropy generation and pressure drop of two water based nanofluids (Cu-water and Al2O3-water) in horizontal annular tubes are scrutinized by means of computational fluids dynamics, response surface methodology and sensitivity analysis. First, central composite design is used to perform a series of experiments with diameter ratio, length to diameter ratio, Reynolds number and solid volume fraction. Then, CFD is used to calculate the Nusselt Number, Euler number and entropy generation. After that, RSM is applied to fit second order polynomials on responses. Finally, sensitivity analysis is conducted to manage the above mentioned parameters inside tube. Totally, 62 different cases are examined. CFD results show that Cu-water and Al2O3-water have the highest and lowest heat transfer rate, respectively. In addition, analysis of variances indicates that increase in solid volume fraction increases dimensionless pressure drop for Al2O3-water. Moreover, it has a significant negative and insignificant effects on Cu-water Nusselt and Euler numbers, respectively. Analysis of Bejan number indicates that frictional and thermal entropy generations are the dominant irreversibility in Al2O3-water and Cu-water flows, respectively. Sensitivity analysis indicates dimensionless pressure drop sensitivity to tube length for Cu-water is independent of its diameter ratio at different Reynolds numbers.

Performance Assessment of the Commercial CFD Software for the Prediction of the Reactor Internal Flow

NASA Astrophysics Data System (ADS)

Lee, Gong Hee; Bang, Young Seok; Woo, Sweng Woong; Kim, Do Hyeong; Kang, Min Ku

2014-06-01

As the computer hardware technology develops the license applicants for nuclear power plant use the commercial CFD software with the aim of reducing the excessive conservatism associated with using simplified and conservative analysis tools. Even if some of CFD software developer and its user think that a state of the art CFD software can be used to solve reasonably at least the single-phase nuclear reactor problems, there is still limitation and uncertainty in the calculation result. From a regulatory perspective, Korea Institute of Nuclear Safety (KINS) is presently conducting the performance assessment of the commercial CFD software for nuclear reactor problems. In this study, in order to examine the validity of the results of 1/5 scaled APR+ (Advanced Power Reactor Plus) flow distribution tests and the applicability of CFD in the analysis of reactor internal flow, the simulation was conducted with the two commercial CFD software (ANSYS CFX V.14 and FLUENT V.14) among the numerous commercial CFD software and was compared with the measurement. In addition, what needs to be improved in CFD for the accurate simulation of reactor core inlet flow was discussed.

Computational Fluid Dynamics Uncertainty Analysis Applied to Heat Transfer over a Flat Plate

NASA Technical Reports Server (NTRS)

Groves, Curtis Edward; Ilie, Marcel; Schallhorn, Paul A.

2013-01-01

There have been few discussions on using Computational Fluid Dynamics (CFD) without experimental validation. Pairing experimental data, uncertainty analysis, and analytical predictions provides a comprehensive approach to verification and is the current state of the art. With pressed budgets, collecting experimental data is rare or non-existent. This paper investigates and proposes a method to perform CFD uncertainty analysis only from computational data. The method uses current CFD uncertainty techniques coupled with the Student-T distribution to predict the heat transfer coefficient over a at plate. The inputs to the CFD model are varied from a specified tolerance or bias error and the difference in the results are used to estimate the uncertainty. The variation in each input is ranked from least to greatest to determine the order of importance. The results are compared to heat transfer correlations and conclusions drawn about the feasibility of using CFD without experimental data. The results provide a tactic to analytically estimate the uncertainty in a CFD model when experimental data is unavailable

Generic Hypersonic Inlet Module Analysis

NASA Technical Reports Server (NTRS)

Cockrell, Chares E., Jr.; Huebner, Lawrence D.

2004-01-01

A computational study associated with an internal inlet drag analysis was performed for a generic hypersonic inlet module. The purpose of this study was to determine the feasibility of computing the internal drag force for a generic scramjet engine module using computational methods. The computational study consisted of obtaining two-dimensional (2D) and three-dimensional (3D) computational fluid dynamics (CFD) solutions using the Euler and parabolized Navier-Stokes (PNS) equations. The solution accuracy was assessed by comparisons with experimental pitot pressure data. The CFD analysis indicates that the 3D PNS solutions show the best agreement with experimental pitot pressure data. The internal inlet drag analysis consisted of obtaining drag force predictions based on experimental data and 3D CFD solutions. A comparative assessment of each of the drag prediction methods is made and the sensitivity of CFD drag values to computational procedures is documented. The analysis indicates that the CFD drag predictions are highly sensitive to the computational procedure used.

Numerical Uncertainty Analysis for Computational Fluid Dynamics using Student T Distribution -- Application of CFD Uncertainty Analysis Compared to Exact Analytical Solution

NASA Technical Reports Server (NTRS)

Groves, Curtis E.; Ilie, marcel; Shallhorn, Paul A.

2014-01-01

Computational Fluid Dynamics (CFD) is the standard numerical tool used by Fluid Dynamists to estimate solutions to many problems in academia, government, and industry. CFD is known to have errors and uncertainties and there is no universally adopted method to estimate such quantities. This paper describes an approach to estimate CFD uncertainties strictly numerically using inputs and the Student-T distribution. The approach is compared to an exact analytical solution of fully developed, laminar flow between infinite, stationary plates. It is shown that treating all CFD input parameters as oscillatory uncertainty terms coupled with the Student-T distribution can encompass the exact solution.

Development and Validation of a Hypersonic Vehicle Design Tool Based On Waverider Design Technique

NASA Astrophysics Data System (ADS)

Dasque, Nastassja

Methodologies for a tool capable of assisting design initiatives for practical waverider based hypersonic vehicles were developed and validated. The design space for vehicle surfaces was formed using an algorithm that coupled directional derivatives with the conservation laws to determine a flow field defined by a set of post-shock streamlines. The design space is used to construct an ideal waverider with a sharp leading edge. A blunting method was developed to modify the ideal shapes to a more practical geometry for real-world application. Empirical and analytical relations were then systematically applied to the resulting geometries to determine local pressure, skin-friction and heat flux. For the ideal portion of the geometry, flat plate relations for compressible flow were applied. For the blunted portion of the geometry modified Newtonian theory, Fay-Riddell theory and Modified Reynolds analogy were applied. The design and analysis methods were validated using analytical solutions as well as empirical and numerical data. The streamline solution for the flow field generation technique was compared with a Taylor-Maccoll solution and showed very good agreement. The relationship between the local Stanton number and skin friction coefficient with local Reynolds number along the ideal portion of the body showed good agreement with experimental data. In addition, an automated grid generation routine was formulated to construct a structured mesh around resulting geometries in preparation for Computational Fluid Dynamics analysis. The overall analysis of the waverider body using the tool was then compared to CFD studies. The CFD flow field showed very good agreement with the design space. However, the distribution of the surface properties was near CFD results but did not have great agreement.

Development of an Integrated Nozzle for a Symmetric, RBCC Launch Vehicle Configuration

NASA Technical Reports Server (NTRS)

Smith, Timothy D.; Canabal, Francisco, III; Rice, Tharen; Blaha, Bernard

2000-01-01

The development of rocket based combined cycle (RBCC) engines is highly dependent upon integrating several different modes of operation into a single system. One of the key components to develop acceptable performance levels through each mode of operation is the nozzle. It must be highly integrated to serve the expansion processes of both rocket and air-breathing modes without undue weight, drag, or complexity. The NASA GTX configuration requires a fixed geometry, altitude-compensating nozzle configuration. The initial configuration, used mainly to estimate weight and cooling requirements was a 1 So half-angle cone, which cuts a concave surface from a point within the flowpath to the vehicle trailing edge. Results of 3-D CFD calculations on this geometry are presented. To address the critical issues associated with integrated, fixed geometry, multimode nozzle development, the GTX team has initiated a series of tasks to evolve the nozzle design, and validate performance levels. An overview of these tasks is given. The first element is a design activity to develop tools for integration of efficient expansion surfaces With the existing flowpath and vehicle aft-body, and to develop a second-generation nozzle design. A preliminary result using a "streamline-tracing" technique is presented. As the nozzle design evolves, a combination of 3-D CFD analysis and experimental evaluation will be used to validate the design procedure and determine the installed performance for propulsion cycle modeling. The initial experimental effort will consist of cold-flow experiments designed to validate the general trends of the streamline-tracing methodology and anchor the CFD analysis. Experiments will also be conducted to simulate nozzle performance during each mode of operation. As the design matures, hot-fire tests will be conducted to refine performance estimates and anchor more sophisticated reacting-flow analysis.

Computational Investigations on the Aerodynamics of a Generic Car Model in Proximity to a Side Wall

NASA Astrophysics Data System (ADS)

Mallapragada, Srivatsa

A moving road vehicle is subjected to many fluid interferences caused by a number of external agents apart from the vehicle itself. Vehicles moving in proximity to a side wall is an interesting aspect that has been little investigated in the literature. This is of great interest in motorsports, more specifically in NASCAR racing. The aim of this thesis is to develop a Computational Fluid Dynamics (CFD) model that can simulate the motion of a race car moving close to a side wall with an objective of understanding the influence of this side barrier on the overall aerodynamic characteristics of the vehicle, like the force and moment coefficients. Additionally, flow visualization tools are used to gain insights into the flow field and to explain the causes of the observed aerodynamic characteristics of the vehicle. This is accomplished by using a generic car model, a 25-degree slant angle Ahmed Body, in proximity to a side wall in a virtual wind tunnel where the vehicle body is allowed to move at constant velocity. This methodology is different from the traditional CFD approach where the air is blown over a stationary vehicle. The simulation process used in this thesis requires the use of a recently developed meshing methodology called the Overset mesh. All simulations were run using a commercial finite volume CFD code called StarCCM+ where the Unsteady Reynolds Averaged Navier-Stokes URANS fluid flow solver was used to model turbulence. However, the existing literature suggests that no URANS model can correctly predict the flow field around a 25-degree slant Ahmed body model; all models under-predict turbulence in the initial separated shear layer and over-predict the separation region. Subsequently, the first phase of this thesis involved the determination of a modeling methodology that can accurately predict the flow-field over a 25-degree Ahmed body. Two two-equation eddy-viscosity turbulence models, the AKN and SST preferred by many researchers for CFD simulations of massively separated flows, were tested. It turned out that only the latter with modified model coefficients was capable of reproducing the experimental results with a reasonable accuracy. Compared to the eddy viscosity CFD simulations of an isolated 25-degree slant angle Ahmed body seen in existing literature, the results presented in this thesis show significantly better correlations with experiments. The wall proximity studies show a strong influence of the presence of the wall on the overall aerodynamic characteristics of the vehicle body. When compared with the experimental studies, although both show similar trends, however, there exists a significant difference between the experimental and CFD predicted results which tend to worsen as one approaches the wall. These differences can be attributed to fact that the CFD emulation of the flow around the side-wall is more realistic compared to the experimental implementation.

Computational fluid dynamics modelling in cardiovascular medicine

PubMed Central

Morris, Paul D; Narracott, Andrew; von Tengg-Kobligk, Hendrik; Silva Soto, Daniel Alejandro; Hsiao, Sarah; Lungu, Angela; Evans, Paul; Bressloff, Neil W; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P

2016-01-01

This paper reviews the methods, benefits and challenges associated with the adoption and translation of computational fluid dynamics (CFD) modelling within cardiovascular medicine. CFD, a specialist area of mathematics and a branch of fluid mechanics, is used routinely in a diverse range of safety-critical engineering systems, which increasingly is being applied to the cardiovascular system. By facilitating rapid, economical, low-risk prototyping, CFD modelling has already revolutionised research and development of devices such as stents, valve prostheses, and ventricular assist devices. Combined with cardiovascular imaging, CFD simulation enables detailed characterisation of complex physiological pressure and flow fields and the computation of metrics which cannot be directly measured, for example, wall shear stress. CFD models are now being translated into clinical tools for physicians to use across the spectrum of coronary, valvular, congenital, myocardial and peripheral vascular diseases. CFD modelling is apposite for minimally-invasive patient assessment. Patient-specific (incorporating data unique to the individual) and multi-scale (combining models of different length- and time-scales) modelling enables individualised risk prediction and virtual treatment planning. This represents a significant departure from traditional dependence upon registry-based, population-averaged data. Model integration is progressively moving towards ‘digital patient’ or ‘virtual physiological human’ representations. When combined with population-scale numerical models, these models have the potential to reduce the cost, time and risk associated with clinical trials. The adoption of CFD modelling signals a new era in cardiovascular medicine. While potentially highly beneficial, a number of academic and commercial groups are addressing the associated methodological, regulatory, education- and service-related challenges. PMID:26512019

Cadaveric validation study of computational fluid dynamics model of sinus irrigations before and after sinus surgery

PubMed Central

Craig, John R; Zhao, Kai; Doan, Ngoc; Khalili, Sammy; Lee, John YK; Adappa, Nithin D; Palmer, James N

2016-01-01

Background Investigations into the distribution of sinus irrigations have been limited by labor-intensive methodologies that do not capture the full dynamics of irrigation flow. The purpose of this study was to validate the accuracy of a computational fluid dynamics (CFD) model for sinonasal irrigations through a cadaveric experiment. Methods Endoscopic sinus surgery was performed on two fresh cadavers to open all eight sinuses, including a Draf III procedure for cadaver 1, and Draf IIb frontal sinusotomies for cadaver 2. Computed tomography maxillofacial scans were obtained preoperatively and postoperatively, from which CFD models were created. Blue-dyed saline in a 240 mL squeeze bottle was used to irrigate cadaver sinuses at 60 mL/s (120 mL per side, over 2 seconds). These parameters were replicated in CFD simulations. Endoscopes were placed through trephinations drilled through the anterior walls of the maxillary and frontal sinuses, and sphenoid roofs. Irrigation flow into the maxillary, frontal, and sphenoid sinuses was graded both ipsilateral and contralateral to the side of nasal irrigation, and then compared with the CFD simulations. Results In both cadavers, preoperative and postoperative irrigation flow into maxillary, frontal, and sphenoid sinuses matched extremely well when comparing the CFD models and cadaver endoscopic videos. For cadaver 1, there was 100% concordance between the CFD model and cadaver videos, and 83% concordance for cadaver 2. Conclusions This cadaveric experiment provided potential validation of the CFD model for simulating saline irrigation flow into the maxillary, frontal, and sphenoid sinuses before and after sinus surgery. PMID:26880742

Focused Assessment of State-of-the-Art CFD Capabilities for Prediction of Subsonic Fixed Wing Aircraft Aerodynamics

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L.; Wahls, Richard A.

2008-01-01

Several recent workshops and studies are used to make an assessment of the current status of CFD for subsonic fixed wing aerodynamics. Uncertainty quantification plays a significant role in the assessment, so terms associated with verification and validation are given and some methodology and research areas are highlighted. For high-subsonic-speed cruise through buffet onset, the series of drag prediction workshops and NASA/Boeing buffet onset studies are described. For low-speed flow control for high lift, a circulation control workshop and a synthetic jet flow control workshop are described. Along with a few specific recommendations, gaps and needs identified through the workshops and studies are used to develop a list of broad recommendations to improve CFD capabilities and processes for this discipline in the future.

CFD Analysis of Experimental Wing and Winglet for FalconLAUNCH 8 and the ExFIT Program

DTIC Science & Technology

2010-03-01

CFD Analysis of Experimental Wing and Winglet for FalconLAUNCH 8 and the ExFIT Program THESIS Benjamin P. Switzer, Second Lieutenant, USAF AFIT/GAE...to copyright protection in the United States. AFIT/GAE/ENY/10-M25 CFD Analysis of Experimental Wing and Winglet for FalconLAUNCH 8 and the ExFIT...this analysis focused on the effects caused by shock waves forming on the winglet and their impact on the lifting characteristics and temperature

A guided tour of current research in synovial joints with reference to wavelet methodology

NASA Astrophysics Data System (ADS)

Agarwal, Ruchi; Salimath, C. S.; Alam, Khursheed

2017-10-01

Main aim of this article is to provide a comprehensive overview of biomechanical aspects of synovial joints of human body. This can be considered as a part of continued research work carried out by various authors over a period of time. Almost every person once in life time has suffered from joint disease; this has triggered intensive investigation into various biomechanical aspects of synovial joints. This has also resulted into an increase of arthroplasty with introduction to various clinical trials. From last few decades new improvements and ideas for new technologies have been introduced to decrease the incidence of joint problem. In this paper a literature survey of recent advances, developments and recognition of wear and tear of human joint is presented. Wavelet method in Computational fluid dynamics (CFD) is relatively a new research field. This review aims to provide a glimpse of wavelet methodology in CFD. Wavelets methodology has played a vital role in the solution of governing equation of synovial fluid flow in the synovial joints represented by Reynolds equation and its modified version.

Pressure Distribution and Performance Impacts of Aerospike Nozzles on Rotating Detonation Engines

DTIC Science & Technology

2017-06-01

design methodology at both on- and off-design conditions anticipated throughout the combustion cycle. Steady-state, non -reacting computational fluid...operation. Therefore, the nozzle contour was designed using a traditional, steady-state design methodology at both on- and off-design conditions...anticipated throughout the combustion cycle. Steady-state, non -reacting computational fluid dynamics (CFD) simulations were performed on various nozzle

Selection of stationary phase particle geometry using X-ray computed tomography and computational fluid dynamics simulations.

PubMed

Schmidt, Irma; Minceva, Mirjana; Arlt, Wolfgang

2012-02-17

The X-ray computed tomography (CT) is used to determine local parameters related to the column packing homogeneity and hydrodynamics in columns packed with spherically and irregularly shaped particles of same size. The results showed that the variation of porosity and axial dispersion coefficient along the column axis is insignificant, compared to their radial distribution. The methodology of using the data attained by CT measurements to perform a CFD simulation of a batch separation of model binary mixtures, with different concentration and separation factors is demonstrated. The results of the CFD simulation study show that columns packed with spherically shaped particles provide higher yield in comparison to columns packed with irregularly shaped particles only below a certain value of the separation factor. The presented methodology can be used for selecting a suited packing material for a particular separation task. Copyright © 2012 Elsevier B.V. All rights reserved.

Assessment of the Unstructured Grid Software TetrUSS for Drag Prediction of the DLR-F4 Configuration

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar Z.; Frink, Neal T.

2002-01-01

An application of the NASA unstructured grid software system TetrUSS is presented for the prediction of aerodynamic drag on a transport configuration. The paper briefly describes the underlying methodology and summarizes the results obtained on the DLR-F4 transport configuration recently presented in the first AIAA computational fluid dynamics (CFD) Drag Prediction Workshop. TetrUSS is a suite of loosely coupled unstructured grid CFD codes developed at the NASA Langley Research Center. The meshing approach is based on the advancing-front and the advancing-layers procedures. The flow solver employs a cell-centered, finite volume scheme for solving the Reynolds Averaged Navier-Stokes equations on tetrahedral grids. For the present computations, flow in the viscous sublayer has been modeled with an analytical wall function. The emphasis of the paper is placed on the practicality of the methodology for accurately predicting aerodynamic drag data.

Duct flow nonuniformities for Space Shuttle Main Engine (SSME)

NASA Technical Reports Server (NTRS)

1987-01-01

A three-duct Space Shuttle Main Engine (SSME) Hot Gas Manifold geometry code was developed for use. The methodology of the program is described, recommendations on its implementation made, and an input guide, input deck listing, and a source code listing provided. The code listing is strewn with an abundance of comments to assist the user in following its development and logic. A working source deck will be provided. A thorough analysis was made of the proper boundary conditions and chemistry kinetics necessary for an accurate computational analysis of the flow environment in the SSME fuel side preburner chamber during the initial startup transient. Pertinent results were presented to facilitate incorporation of these findings into an appropriate CFD code. The computation must be a turbulent computation, since the flow field turbulent mixing will have a profound effect on the chemistry. Because of the additional equations demanded by the chemistry model it is recommended that for expediency a simple algebraic mixing length model be adopted. Performing this computation for all or selected time intervals of the startup time will require an abundance of computer CPU time regardless of the specific CFD code selected.

A Coupled Fluid-Structure Interaction Analysis of Solid Rocket Motor with Flexible Inhibitors

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff

2014-01-01

A capability to couple NASA production CFD code, Loci/CHEM, with CFDRC's structural finite element code, CoBi, has been developed. This paper summarizes the efforts in applying the installed coupling software to demonstrate/investigate fluid-structure interaction (FSI) between pressure wave and flexible inhibitor inside reusable solid rocket motor (RSRM). First a unified governing equation for both fluid and structure is presented, then an Eulerian-Lagrangian framework is described to satisfy the interfacial continuity requirements. The features of fluid solver, Loci/CHEM and structural solver, CoBi, are discussed before the coupling methodology of the solvers is described. The simulation uses production level CFD LES turbulence model with a grid resolution of 80 million cells. The flexible inhibitor is modeled with full 3D shell elements. Verifications against analytical solutions of structural model under steady uniform pressure condition and under dynamic condition of modal analysis show excellent agreements in terms of displacement distribution and eigen modal frequencies. The preliminary coupled result shows that due to acoustic coupling, the dynamics of one of the more flexible inhibitors shift from its first modal frequency to the first acoustic frequency of the solid rocket motor.

CFD analysis of turbopump volutes

NASA Technical Reports Server (NTRS)

Ascoli, Edward P.; Chan, Daniel C.; Darian, Armen; Hsu, Wayne W.; Tran, Ken

1993-01-01

An effort is underway to develop a procedure for the regular use of CFD analysis in the design of turbopump volutes. Airflow data to be taken at NASA Marshall will be used to validate the CFD code and overall procedure. Initial focus has been on preprocessing (geometry creation, translation, and grid generation). Volute geometries have been acquired electronically and imported into the CATIA CAD system and RAGGS (Rockwell Automated Grid Generation System) via the IGES standard. An initial grid topology has been identified and grids have been constructed for turbine inlet and discharge volutes. For CFD analysis of volutes to be used regularly, a procedure must be defined to meet engineering design needs in a timely manner. Thus, a compromise must be established between making geometric approximations, the selection of grid topologies, and possible CFD code enhancements. While the initial grid developed approximated the volute tongue with a zero thickness, final computations should more accurately account for the geometry in this region. Additionally, grid topologies will be explored to minimize skewness and high aspect ratio cells that can affect solution accuracy and slow code convergence. Finally, as appropriate, code modifications will be made to allow for new grid topologies in an effort to expedite the overall CFD analysis process.

A Semiautomated Method for Measuring the 3-Dimensional Fabric to Renal Artery Distances to Determine Endograft Position After Endovascular Aneurysm Repair.

PubMed

Schuurmann, Richte C L; Overeem, Simon P; Ouriel, Kenneth; Slump, Cornelis H; Jordan, William D; Muhs, Bart E; de Vries, Jean-Paul P M

2017-10-01

To report a methodology for 3-dimensional (3D) assessment of the stent-graft deployment accuracy after endovascular aneurysm repair (EVAR). A methodology was developed and validated to calculate the 3D distances between the endograft fabric and the renal arteries over the curve of the aorta. The shortest distance between one of the renal arteries and the fabric (SFD) and the distance from the contralateral renal artery to the fabric (CFD) were determined on the first postoperative computed tomography (CT) scan of 81 elective EVAR patients. The SFDs were subdivided into a target position (0-3 mm distal to the renal artery), high position (partially covering the renal artery), and low position (>3 mm distal to the renal artery). Data are reported as the median (interquartile range, IQR). Intra- and interobserver agreements for automatic and manual calculation of the SFD and CFD were excellent (ICC >0.892, p<0.001). The median SFD was 1.4 mm (IQR -0.9, 3.0) and the median CFD was 8.0 mm (IQR 3.9, 14.2). The target position was achieved in 44%, high position in 30%, and low position in 26% of the patients. The median slope of the endograft toward the higher renal artery was 2.5° (IQR -5.5°, 13.9°). The novel methodology using 3D CT reconstructions enables accurate evaluation of endograft position and slope within the proximal aortic neck. In this series, only 44% of endografts were placed within the target position with regard to the lowermost renal artery.

CFD Simulations in Support of Shuttle Orbiter Contingency Abort Aerodynamic Database Enhancement

NASA Technical Reports Server (NTRS)

Papadopoulos, Periklis E.; Prabhu, Dinesh; Wright, Michael; Davies, Carol; McDaniel, Ryan; Venkatapathy, E.; Wercinski, Paul; Gomez, R. J.

2001-01-01

Modern Computational Fluid Dynamics (CFD) techniques were used to compute aerodynamic forces and moments of the Space Shuttle Orbiter in specific portions of contingency abort trajectory space. The trajectory space covers a Mach number range of 3.5-15, an angle-of-attack range of 20deg-60deg, an altitude range of 100-190 kft, and several different settings of the control surfaces (elevons, body flap, and speed brake). Presented here are details of the methodology and comparisons of computed aerodynamic coefficients against the values in the current Orbiter Operational Aerodynamic Data Book (OADB). While approximately 40 cases have been computed, only a sampling of the results is provided here. The computed results, in general, are in good agreement with the OADB data (i.e., within the uncertainty bands) for almost all the cases. However, in a limited number of high angle-of-attack cases (at Mach 15), there are significant differences between the computed results, especially the vehicle pitching moment, and the OADB data. A preliminary analysis of the data from the CFD simulations at Mach 15 shows that these differences can be attributed to real-gas/Mach number effects. The aerodynamic coefficients and detailed surface pressure distributions of the present simulations are being used by the Shuttle Program in the evaluation of the capabilities of the Orbiter in contingency abort scenarios.

CFD Simulation of Liquid Rocket Engine Injectors

NASA Technical Reports Server (NTRS)

Farmer, Richard; Cheng, Gary; Chen, Yen-Sen; Garcia, Roberto (Technical Monitor)

2001-01-01

Detailed design issues associated with liquid rocket engine injectors and combustion chamber operation require CFD methodology which simulates highly three-dimensional, turbulent, vaporizing, and combusting flows. The primary utility of such simulations involves predicting multi-dimensional effects caused by specific injector configurations. SECA, Inc. and Engineering Sciences, Inc. have been developing appropriate computational methodology for NASA/MSFC for the past decade. CFD tools and computers have improved dramatically during this time period; however, the physical submodels used in these analyses must still remain relatively simple in order to produce useful results. Simulations of clustered coaxial and impinger injector elements for hydrogen and hydrocarbon fuels, which account for real fluid properties, is the immediate goal of this research. The spray combustion codes are based on the FDNS CFD code' and are structured to represent homogeneous and heterogeneous spray combustion. The homogeneous spray model treats the flow as a continuum of multi-phase, multicomponent fluids which move without thermal or velocity lags between the phases. Two heterogeneous models were developed: (1) a volume-of-fluid (VOF) model which represents the liquid core of coaxial or impinger jets and their atomization and vaporization, and (2) a Blob model which represents the injected streams as a cloud of droplets the size of the injector orifice which subsequently exhibit particle interaction, vaporization, and combustion. All of these spray models are computationally intensive, but this is unavoidable to accurately account for the complex physics and combustion which is to be predicted, Work is currently in progress to parallelize these codes to improve their computational efficiency. These spray combustion codes were used to simulate the three test cases which are the subject of the 2nd International Workshop on-Rocket Combustion Modeling. Such test cases are considered by these investigators to be very valuable for code validation because combustion kinetics, turbulence models and atomization models based on low pressure experiments of hydrogen air combustion do not adequately verify analytical or CFD submodels which are necessary to simulate rocket engine combustion. We wish to emphasize that the simulations which we prepared for this meeting are meant to test the accuracy of the approximations used in our general purpose spray combustion models, rather than represent a definitive analysis of each of the experiments which were conducted. Our goal is to accurately predict local temperatures and mixture ratios in rocket engines; hence predicting individual experiments is used only for code validation. To replace the conventional JANNAF standard axisymmetric finite-rate (TDK) computer code 2 for performance prediction with CFD cases, such codes must posses two features. Firstly, they must be as easy to use and of comparable run times for conventional performance predictions. Secondly, they must provide more detailed predictions of the flowfields near the injector face. Specifically, they must accurately predict the convective mixing of injected liquid propellants in terms of the injector element configurations.

Study of Laminar Flame 2-D Scalar Values at Various Fuel to Air Ratios Using an Imaging Fourier-Transform Spectrometer and 2-D CFD Analysis

DTIC Science & Technology

2013-03-01

NASA- Glenn’s Chemical Equilibrium with Applications (CEA) program. UNICORN CFD predictions were in excellent agreement with CEA calculations at...49 Appendix A – UNICORN CFD Inputs and Instruction .....................................................50 Appendix B – NASA-Glenn...17 Figure 7: Schematic of UNICORN CFD card setup. ........................................................ 18 Figure 8: Averaged flame

Computational fluid dynamics modelling in cardiovascular medicine.

PubMed

Morris, Paul D; Narracott, Andrew; von Tengg-Kobligk, Hendrik; Silva Soto, Daniel Alejandro; Hsiao, Sarah; Lungu, Angela; Evans, Paul; Bressloff, Neil W; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P

2016-01-01

This paper reviews the methods, benefits and challenges associated with the adoption and translation of computational fluid dynamics (CFD) modelling within cardiovascular medicine. CFD, a specialist area of mathematics and a branch of fluid mechanics, is used routinely in a diverse range of safety-critical engineering systems, which increasingly is being applied to the cardiovascular system. By facilitating rapid, economical, low-risk prototyping, CFD modelling has already revolutionised research and development of devices such as stents, valve prostheses, and ventricular assist devices. Combined with cardiovascular imaging, CFD simulation enables detailed characterisation of complex physiological pressure and flow fields and the computation of metrics which cannot be directly measured, for example, wall shear stress. CFD models are now being translated into clinical tools for physicians to use across the spectrum of coronary, valvular, congenital, myocardial and peripheral vascular diseases. CFD modelling is apposite for minimally-invasive patient assessment. Patient-specific (incorporating data unique to the individual) and multi-scale (combining models of different length- and time-scales) modelling enables individualised risk prediction and virtual treatment planning. This represents a significant departure from traditional dependence upon registry-based, population-averaged data. Model integration is progressively moving towards 'digital patient' or 'virtual physiological human' representations. When combined with population-scale numerical models, these models have the potential to reduce the cost, time and risk associated with clinical trials. The adoption of CFD modelling signals a new era in cardiovascular medicine. While potentially highly beneficial, a number of academic and commercial groups are addressing the associated methodological, regulatory, education- and service-related challenges. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Validation of computational fluid dynamics-based analysis to evaluate hemodynamic significance of access stenosis.

PubMed

Hoganson, David M; Hinkel, Cameron J; Chen, Xiaomin; Agarwal, Ramesh K; Shenoy, Surendra

2014-01-01

Stenosis in a vascular access circuit is the predominant cause of access dysfunction. Hemodynamic significance of a stenosis identified by angiography in an access circuit is uncertain. This study utilizes computational fluid dynamics (CFD) to model flow through arteriovenous fistula to predict the functional significance of stenosis in vascular access circuits. Three-dimensional models of fistulas were created with a range of clinically relevant stenoses using SolidWorks. Stenoses diameters ranged from 1.0 to 3.0 mm and lengths from 5 to 60 mm within a fistula diameter of 7 mm. CFD analyses were performed using a blood model over a range of blood pressures. Eight patient-specific stenoses were also modeled and analyzed with CFD and the resulting blood flow calculations were validated by comparison with brachial artery flow measured by duplex ultrasound. Predicted flow rates were derived from CFD analysis of a range of stenoses. These stenoses were modeled by CFD and correlated with the ultrasound measured flow rate through the fistula of eight patients. The calculated flow rate using CFD correlated within 20% of ultrasound measured flow for five of eight patients. The mean difference was 17.2% (ranged from 1.3% to 30.1%). CFD analysis-generated flow rate tables provide valuable information to assess the functional significance of stenosis detected during imaging studies. The CFD study can help in determining the clinical relevance of a stenosis in access dysfunction and guide the need for intervention.

Performance Enhancement Strategies for Multi-Block Overset Grid CFD Applications

NASA Technical Reports Server (NTRS)

Djomehri, M. Jahed; Biswas, Rupak

2003-01-01

The overset grid methodology has significantly reduced time-to-solution of highfidelity computational fluid dynamics (CFD) simulations about complex aerospace configurations. The solution process resolves the geometrical complexity of the problem domain by using separately generated but overlapping structured discretization grids that periodically exchange information through interpolation. However, high performance computations of such large-scale realistic applications must be handled efficiently on state-of-the-art parallel supercomputers. This paper analyzes the effects of various performance enhancement strategies on the parallel efficiency of an overset grid Navier-Stokes CFD application running on an SGI Origin2000 machinc. Specifically, the role of asynchronous communication, grid splitting, and grid grouping strategies are presented and discussed. Details of a sophisticated graph partitioning technique for grid grouping are also provided. Results indicate that performance depends critically on the level of latency hiding and the quality of load balancing across the processors.

Proceedings of the 2004 Workshop on CFD Validation of Synthetic Jets and Turbulent Separation Control

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L. (Compiler)

2007-01-01

The papers presented here are from the Langley Research Center Workshop on Computational Fluid Dynamics (CFD) Validation of Synthetic Jets and Turbulent Separation Control (nicknamed "CFDVAL2004"), held March 2004 in Williamsburg, Virginia. The goal of the workshop was to bring together an international group of CFD practitioners to assess the current capabilities of different classes of turbulent flow solution methodologies to predict flow fields induced by synthetic jets and separation control geometries. The workshop consisted of three flow-control test cases of varying complexity, and participants could contribute to any number of the cases. Along with their workshop submissions, each participant included a short write-up describing their method for computing the particular case(s). These write-ups are presented as received from the authors with no editing. Descriptions of each of the test cases and experiments are also included.

A CFD study of Screw Compressor Motor Cooling Analysis

NASA Astrophysics Data System (ADS)

Branch, S.

2017-08-01

Screw compressors use electric motors to drive the male screw rotor. They are cooled by the suction refrigerant vapor that flows around the motor. The thermal conditions of the motor can dramatically influence the performance and reliability of the compressor. The more optimized this flow path is, the better the motor performance. For that reason it is important to understand the flow characteristics around the motor and the motor temperatures. Computational fluid dynamics (CFD) can be used to provide a detailed analysis of the refrigerant’s flow behavior and motor temperatures to identify the undesirable hot spots in the motor. CFD analysis can be used further to optimize the flow path and determine the reduction of hot spots and cooling effect. This study compares the CFD solutions of a motor cooling model to a motor installed with thermocouples measured in the lab. The compressor considered for this study is an R134a screw compressor. The CFD simulation of the motor consists of a detailed breakdown of the stator and rotor components. Orthotropic thermal conductivity material properties are used to represent the simplified motor geometry. In addition, the analysis includes the motor casings of the compressor to draw heat away from the motor by conduction. The study will look at different operating conditions and motor speeds. Finally, the CFD study will investigate the predicted motor temperature change by varying the vapor mass flow rates and motor speed. Recommendations for CFD modeling of such intricate heat transfer phenomenon have thus been proposed.

Overview of the LaNCETS Flight Experiment and CFD Analysis. Supplemental Movies

NASA Technical Reports Server (NTRS)

Cliatt, Larry J., II; Haering, Edward A., Jr.; Bui, Trong

2008-01-01

This presentation focuses on nearfield airborne pressure signatures from the Lift and Nozzle Change Effect on Tail Shocks (LaNCETS) flight test experiment. The primary motivation for nearfield probing in the supersonic regime is to measure the shock structure of aircraft in an ongoing effort to overcome the overland sonic boom barrier for commercial supersonic transportation. LaNCETS provides the opportunity to investigate lift distribution and engine plume effects. During Phase 1 flight testing an F-15B was used to probe the F-15 LaNCETS aircraft in order to validate CFD and pre-flight prediction tools. A total of 29 probings were taken at 40,000 ft. altitude at Machs 1.2, 1.4 and 1.6. LaNCETS Phase 1 flight data are presented as a detailed pressure signature superimposed over a picture of the LaNCETS aircraft. The attenuation of the Inlet-Canard shocks with distance as well as its forward propagation and the coalescence of the noseboom shock are illustrated. A detailed CFD study on a simplified LaNCETS aircraft jet nozzle was performed providing the ability to more accurately capture the shocks from the propulsion system and emphasizing how under- and over-expanding the nozzle affects the existence of shock trains inside the jet plume. With Phase 1 being a success preparations are being made to move forward to Phase 2. Phase 2 will fly similar flight conditions, but this time changing the aircraft's lift distribution by biasing the canard positions, and changing the plume shape by under- and over-expanding the nozzle. Nearfield probing will again be completed in the same manner as in Phase 1. An additional presentation focuses on LaNCETS CFD solution methodology. Discussions highlight grid preprocessing, grid shearing and stretching, flow solving and contour plots. Efforts are underway to better capture the flow features via grid modification and flow solution methodology, which will help to achieve better agreement with flight data. An included CD-ROM provides animations of the nearfield probing procedure and of real data from one of the probings integrated with GPS positional and velocity data. An additional in-flight video from the rear seat of the probing aircraft is also provided.

Removing Grit During Wastewater Treatment: CFD Analysis of HDVS Performance.

PubMed

Meroney, Robert N; Sheker, Robert E

2016-05-01

Computational Fluid Dynamics (CFD) was used to simulate the grit and sand separation effectiveness of a typical hydrodynamic vortex separator (HDVS) system. The analysis examined the influences on the separator efficiency of: flow rate, fluid viscosities, total suspended solids (TSS), and particle size and distribution. It was found that separator efficiency for a wide range of these independent variables could be consolidated into a few curves based on the particle fall velocity to separator inflow velocity ratio, Ws/Vin. Based on CFD analysis it was also determined that systems of different sizes with length scale ratios ranging from 1 to 10 performed similarly when Ws/Vin and TSS were held constant. The CFD results have also been compared to a limited range of experimental data.

Three-Dimensional Computational Fluid Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haworth, D.C.; O'Rourke, P.J.; Ranganathan, R.

1998-09-01

Computational fluid dynamics (CFD) is one discipline falling under the broad heading of computer-aided engineering (CAE). CAE, together with computer-aided design (CAD) and computer-aided manufacturing (CAM), comprise a mathematical-based approach to engineering product and process design, analysis and fabrication. In this overview of CFD for the design engineer, our purposes are three-fold: (1) to define the scope of CFD and motivate its utility for engineering, (2) to provide a basic technical foundation for CFD, and (3) to convey how CFD is incorporated into engineering product and process design.

Application of CFD in aeronautics at NASA Ames Research Center

NASA Astrophysics Data System (ADS)

Maksymiuk, Catherine M.; Enomoto, Francis Y.; Vandalsem, William R.

1995-03-01

The role of Computational Fluid Dynamics (CFD) at Ames Research Center has expanded to address a broad range of aeronautical problems, including wind tunnel support, flight test support, design, and analysis. Balancing the requirements of each new problem against the available resources - software, hardware, time, and expertise - is critical to the effective use of CFD. Several case studies of recent applications highlight the depth of CFD capability at Ames, the tradeoffs involved in various approaches, and lessons learned in the use of CFD as an engineering tool.

CFD Process Pre- and Post-processing Automation in Support of Space Propulsion

NASA Technical Reports Server (NTRS)

Dorney, Suzanne M.

2003-01-01

The use of Computational Fluid Dynamics or CFD has become standard practice in the design and analysis of the major components used for space propulsion. In an attempt to standardize and improve the CFD process a series of automated tools have been developed. Through the use of these automated tools the application of CFD to the design cycle has been improved and streamlined. This paper presents a series of applications in which deficiencies were identified in the CFD process and corrected through the development of automated tools.

Computational Methods for HSCT-Inlet Controls/CFD Interdisciplinary Research

NASA Technical Reports Server (NTRS)

Cole, Gary L.; Melcher, Kevin J.; Chicatelli, Amy K.; Hartley, Tom T.; Chung, Joongkee

1994-01-01

A program aimed at facilitating the use of computational fluid dynamics (CFD) simulations by the controls discipline is presented. The objective is to reduce the development time and cost for propulsion system controls by using CFD simulations to obtain high-fidelity system models for control design and as numerical test beds for control system testing and validation. An interdisciplinary team has been formed to develop analytical and computational tools in three discipline areas: controls, CFD, and computational technology. The controls effort has focused on specifying requirements for an interface between the controls specialist and CFD simulations and a new method for extracting linear, reduced-order control models from CFD simulations. Existing CFD codes are being modified to permit time accurate execution and provide realistic boundary conditions for controls studies. Parallel processing and distributed computing techniques, along with existing system integration software, are being used to reduce CFD execution times and to support the development of an integrated analysis/design system. This paper describes: the initial application for the technology being developed, the high speed civil transport (HSCT) inlet control problem; activities being pursued in each discipline area; and a prototype analysis/design system in place for interactive operation and visualization of a time-accurate HSCT-inlet simulation.

Mechanism of failure of the Cabrol procedure: A computational fluid dynamic analysis.

PubMed

Poullis, M; Pullan, M

2015-12-01

Sudden failure of the Cabrol graft is common and frequently fatal. We utilised the technique of computational fluid dynamic (CFD) analysis to evaluate the mechanism of failure and potentially improve on the design of the Cabrol procedure. CFD analysis of the classic Cabrol procedure and a number of its variants was performed. Results from this analysis was utilised to generate further improved geometric options for the Cabrol procedure. These were also subjected to CFD analysis. All current Cabrol and variations of the Cabrol procedure are predicated by CFD analysis to be prone to graft thrombosis, secondary to stasis around the right coronary artery button. The right coronary artery flow characteristics were found to be the dominant reason for Cabrol graft failure. A simple modification of the Cabrol geometry is predicated to virtually eliminate any areas of blood stasis, and graft failure. Modification of the Cabrol graft geometry, due to CFD analysis may help reduce the incidence of graft thrombosis. A C shaped Cabrol graft with the right coronary button anastomosed to its side along its course from the aorta to the left coronary button is predicted to have the least thrombotic tendency. Clinical correlation is needed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Trajectory Reconstruction and Uncertainty Analysis Using Mars Science Laboratory Pre-Flight Scale Model Aeroballistic Testing

NASA Technical Reports Server (NTRS)

Lugo, Rafael A.; Tolson, Robert H.; Schoenenberger, Mark

2013-01-01

As part of the Mars Science Laboratory (MSL) trajectory reconstruction effort at NASA Langley Research Center, free-flight aeroballistic experiments of instrumented MSL scale models was conducted at Aberdeen Proving Ground in Maryland. The models carried an inertial measurement unit (IMU) and a flush air data system (FADS) similar to the MSL Entry Atmospheric Data System (MEADS) that provided data types similar to those from the MSL entry. Multiple sources of redundant data were available, including tracking radar and on-board magnetometers. These experimental data enabled the testing and validation of the various tools and methodologies that will be used for MSL trajectory reconstruction. The aerodynamic parameters Mach number, angle of attack, and sideslip angle were estimated using minimum variance with a priori to combine the pressure data and pre-flight computational fluid dynamics (CFD) data. Both linear and non-linear pressure model terms were also estimated for each pressure transducer as a measure of the errors introduced by CFD and transducer calibration. Parameter uncertainties were estimated using a "consider parameters" approach.

On the Comparison of the Long Penetration Mode (LPM) Supersonic Counterflowing Jet to the Supersonic Screech Jet

NASA Technical Reports Server (NTRS)

Farr, Rebecca A.; Chang, Chau-Lyan.; Jones, Jess H.; Dougherty, N. Sam

2015-01-01

The authors provide a brief overview of the classic tonal screech noise problem created by underexpanded supersonic jets, briefly describing the fluid dynamic-acoustics feedback mechanism that has been long established as the basis for this well-known aeroacoustics problem. This is followed by a description of the Long Penetration Mode (LPM) supersonic underexpanded counterflowing jet phenomenon which has been demonstrated in several wind tunnel tests and modeled in several computational fluid dynamics (CFD) simulations. The authors provide evidence from test and CFD analysis of LPM that indicates that acoustics feedback and fluid interaction seen in LPM are analogous to the aeroacoustics interactions seen in screech jets. Finally, the authors propose applying certain methodologies to LPM which have been developed and successfully demonstrated in the study of screech jets and mechanically induced excitation in fluid oscillators for decades. The authors conclude that the large body of work done on jet screech, other aeroacoustic phenomena, and fluid oscillators can have direct application to the study and applications of LPM counterflowing supersonic cold flow jets.

SSME 3-D Turnaround Duct flow analysis - CFD predictions

NASA Technical Reports Server (NTRS)

Brankovic, Andreja; Stowers, Steven T.; Mcconnaughey, Paul

1988-01-01

CFD analysis is presently employed to obtain an improved flowfield for an individual flowpath in the case of the Space Shuttle Main Engine's High Pressure Fuel Turbopump Turn-Around Duct (TAD), which conducts the flow exiting from the gas turbines into the fuel bowl. It is demonstrated that the application of CFD to TAD flow analysis, giving attention to the duct's configuration and to the number, shape, and alignment of the diffuser struts, can enhance understanding of flow physics and result in improved duct design and performance.

CFD-RANS prediction of individual exposure from continuous release of hazardous airborne materials in complex urban environments

NASA Astrophysics Data System (ADS)

Efthimiou, G. C.; Andronopoulos, S.; Bartzis, J. G.; Berbekar, E.; Harms, F.; Leitl, B.

2017-02-01

One of the key issues of recent research on the dispersion inside complex urban environments is the ability to predict individual exposure (maximum dosages) of an airborne material which is released continuously from a point source. The present work addresses the question whether the computational fluid dynamics (CFD)-Reynolds-averaged Navier-Stokes (RANS) methodology can be used to predict individual exposure for various exposure times. This is feasible by providing the two RANS concentration moments (mean and variance) and a turbulent time scale to a deterministic model. The whole effort is focused on the prediction of individual exposure inside a complex real urban area. The capabilities of the proposed methodology are validated against wind-tunnel data (CUTE experiment). The present simulations were performed 'blindly', i.e. the modeller had limited information for the inlet boundary conditions and the results were kept unknown until the end of the COST Action ES1006. Thus, a high uncertainty of the results was expected. The general performance of the methodology due to this 'blind' strategy is good. The validation metrics fulfil the acceptance criteria. The effect of the grid and the turbulence model on the model performance is examined.

Efficacy of assessing circulating cell-free DNA using a simple fluorescence assay in patients with triple-negative breast cancer receiving neoadjuvant chemotherapy: a prospective observational study

PubMed Central

Park, Kwonoh; Woo, Miyoung; Kim, Jeong Eun; Ahn, Jin-Hee; Jung, Kyung Hae; Roh, Jin; Gong, Gyungyub; Kim, Sung-Bae

2018-01-01

This study aims to assess cell-free DNA (CFD) by a fluorescence assay as a biomarker for early prediction of a pathologic complete response (pCR) and relapse in patients with triple-negative breast cancer (TNBC) undergoing neoadjuvant chemotherapy. Patients with clinical stage II or III TNBC scheduled for neoadjuvant chemotherapy were prospectively enrolled. All patients underwent four cycles of Adriamycin plus cyclophosphamide (AC), followed by four cycles of cisplatin or docetaxel chemotherapy and surgery. Blood samples were obtained before the initial chemotherapy (baseline-CFD) and after four AC neoadjuvant chemotherapy cycles (AC-CFD) to evaluate CFD levels. In total, 72 patients who met the inclusion criteria were enrolled. The mean baseline-CFD and AC-CFD levels were 239 ± 68 and 210 ± 66 ng/mL, respectively, with a significant decline in the CFD levels after AC neoadjuvant chemotherapy (P = 0.001). In the 33.6-month median follow-up, 18 cases of relapse were reported. A ROC curve analysis of baseline-CFD was performed to determine the predictive value for relapse, and an area under the curve of 0.62 (95% CI, 0.46–0.78) at 264 ng/mL was obtained. Patients with baseline-CFD >264 ng/mL were at a higher risk of relapse than those with baseline-CFD ≤264 ng/mL (HR, 2.84; 95% CI, 1.11–7.24; P = 0.029). Multivariate analysis established baseline-CFD as an independent predicting factor for relapse (HR, 3.74; 95% CI, 1.32–10.53; P = 0.013). In conclusion, baseline-CFD measured by a fluorescence assay might be a potential biomarker to predict relapse, which could be useful for risk stratification of TNBC. PMID:29423090

Pilot-in-the-Loop CFD Method Development

DTIC Science & Technology

2014-06-16

CFD analysis. Coupled simulations will be run at PSU on the COCOA -4 cluster, a high performance computing cluster. The CRUNCH CFD software has...been installed on the COCOA -4 servers and initial software tests are being conducted. Initial efforts will use the Generic Frigate Shape SFS-2 to

CFD Approach To Investigate The Flow Characteristics In Bi-Directional Ventilated Disc Brake

NASA Astrophysics Data System (ADS)

Munisamy, Kannan M.; Yusoff, Mohd. Zamri; Shuaib, Norshah Hafeez; Thangaraju, Savithry K.

2010-06-01

This paper presents experimental and Computational Fluids Dynamics (CFD) investigations of the flow in ventilated brake discs. Development of an experiment rig with basic measuring devices are detailed out and following a validation study, the possible improvement in the brake cooling can be further analyzed using CFD analysis. The mass flow rate is determined from basic flow measurement technique following that the conventional bi-directional passenger car is simulated using commercial CFD software FLUENT™. The CFD simulation is used to investigate the flow characteristics in between blade flow of the bi-directional ventilated disc brake.

Data Driven Smart Proxy for CFD Application of Big Data Analytics & Machine Learning in Computational Fluid Dynamics, Report Two: Model Building at the Cell Level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ansari, A.; Mohaghegh, S.; Shahnam, M.

To ensure the usefulness of simulation technologies in practice, their credibility needs to be established with Uncertainty Quantification (UQ) methods. In this project, smart proxy is introduced to significantly reduce the computational cost of conducting large number of multiphase CFD simulations, which is typically required for non-intrusive UQ analysis. Smart proxy for CFD models are developed using pattern recognition capabilities of Artificial Intelligence (AI) and Data Mining (DM) technologies. Several CFD simulation runs with different inlet air velocities for a rectangular fluidized bed are used to create a smart CFD proxy that is capable of replicating the CFD results formore » the entire geometry and inlet velocity range. The smart CFD proxy is validated with blind CFD runs (CFD runs that have not played any role during the development of the smart CFD proxy). The developed and validated smart CFD proxy generates its results in seconds with reasonable error (less than 10%). Upon completion of this project, UQ studies that rely on hundreds or thousands of smart CFD proxy runs can be accomplished in minutes. Following figure demonstrates a validation example (blind CFD run) showing the results from the MFiX simulation and the smart CFD proxy for pressure distribution across a fluidized bed at a given time-step (the layer number corresponds to the vertical location in the bed).« less

An implementation of an aeroacoustic prediction model for broadband noise from a vertical axis wind turbine using a CFD informed methodology

NASA Astrophysics Data System (ADS)

Botha, J. D. M.; Shahroki, A.; Rice, H.

2017-12-01

This paper presents an enhanced method for predicting aerodynamically generated broadband noise produced by a Vertical Axis Wind Turbine (VAWT). The method improves on existing work for VAWT noise prediction and incorporates recently developed airfoil noise prediction models. Inflow-turbulence and airfoil self-noise mechanisms are both considered. Airfoil noise predictions are dependent on aerodynamic input data and time dependent Computational Fluid Dynamics (CFD) calculations are carried out to solve for the aerodynamic solution. Analytical flow methods are also benchmarked against the CFD informed noise prediction results to quantify errors in the former approach. Comparisons to experimental noise measurements for an existing turbine are encouraging. A parameter study is performed and shows the sensitivity of overall noise levels to changes in inflow velocity and inflow turbulence. Noise sources are characterised and the location and mechanism of the primary sources is determined, inflow-turbulence noise is seen to be the dominant source. The use of CFD calculations is seen to improve the accuracy of noise predictions when compared to the analytic flow solution as well as showing that, for inflow-turbulence noise sources, blade generated turbulence dominates the atmospheric inflow turbulence.

High Speed Civil Transport (HSCT) Isolated Nacelle Transonic Boattail Drag Study and Results Using Computational Fluid Dynamics (CFD)

NASA Technical Reports Server (NTRS)

Midea, Anthony C.; Austin, Thomas; Pao, S. Paul; DeBonis, James R.; Mani, Mori

2005-01-01

Nozzle boattail drag is significant for the High Speed Civil Transport (HSCT) and can be as high as 25 percent of the overall propulsion system thrust at transonic conditions. Thus, nozzle boattail drag has the potential to create a thrust drag pinch and can reduce HSCT aircraft aerodynamic efficiencies at transonic operating conditions. In order to accurately predict HSCT performance, it is imperative that nozzle boattail drag be accurately predicted. Previous methods to predict HSCT nozzle boattail drag were suspect in the transonic regime. In addition, previous prediction methods were unable to account for complex nozzle geometry and were not flexible enough for engine cycle trade studies. A computational fluid dynamics (CFD) effort was conducted by NASA and McDonnell Douglas to evaluate the magnitude and characteristics of HSCT nozzle boattail drag at transonic conditions. A team of engineers used various CFD codes and provided consistent, accurate boattail drag coefficient predictions for a family of HSCT nozzle configurations. The CFD results were incorporated into a nozzle drag database that encompassed the entire HSCT flight regime and provided the basis for an accurate and flexible prediction methodology.

High Speed Civil Transport (HSCT) Isolated Nacelle Transonic Boattail Drag Study and Results Using Computational Fluid Dynamics (CFD)

NASA Technical Reports Server (NTRS)

Midea, Anthony C.; Austin, Thomas; Pao, S. Paul; DeBonis, James R.; Mani, Mori

1999-01-01

Nozzle boattail drag is significant for the High Speed Civil Transport (HSCT) and can be as high as 25% of the overall propulsion system thrust at transonic conditions. Thus, nozzle boattail drag has the potential to create a thrust-drag pinch and can reduce HSCT aircraft aerodynamic efficiencies at transonic operating conditions. In order to accurately predict HSCT performance, it is imperative that nozzle boattail drag be accurately predicted. Previous methods to predict HSCT nozzle boattail drag were suspect in the transonic regime. In addition, previous prediction methods were unable to account for complex nozzle geometry and were not flexible enough for engine cycle trade studies. A computational fluid dynamics (CFD) effort was conducted by NASA and McDonnell Douglas to evaluate the magnitude and characteristics of HSCT nozzle boattail drag at transonic conditions. A team of engineers used various CFD codes and provided consistent, accurate boattail drag coefficient predictions for a family of HSCT nozzle configurations. The CFD results were incorporated into a nozzle drag database that encompassed the entire HSCT flight regime and provided the basis for an accurate and flexible prediction methodology.

Methodology for extracting local constants from petroleum cracking flows

DOEpatents

Chang, Shen-Lin; Lottes, Steven A.; Zhou, Chenn Q.

2000-01-01

A methodology provides for the extraction of local chemical kinetic model constants for use in a reacting flow computational fluid dynamics (CFD) computer code with chemical kinetic computations to optimize the operating conditions or design of the system, including retrofit design improvements to existing systems. The coupled CFD and kinetic computer code are used in combination with data obtained from a matrix of experimental tests to extract the kinetic constants. Local fluid dynamic effects are implicitly included in the extracted local kinetic constants for each particular application system to which the methodology is applied. The extracted local kinetic model constants work well over a fairly broad range of operating conditions for specific and complex reaction sets in specific and complex reactor systems. While disclosed in terms of use in a Fluid Catalytic Cracking (FCC) riser, the inventive methodology has application in virtually any reaction set to extract constants for any particular application and reaction set formulation. The methodology includes the step of: (1) selecting the test data sets for various conditions; (2) establishing the general trend of the parametric effect on the measured product yields; (3) calculating product yields for the selected test conditions using coupled computational fluid dynamics and chemical kinetics; (4) adjusting the local kinetic constants to match calculated product yields with experimental data; and (5) validating the determined set of local kinetic constants by comparing the calculated results with experimental data from additional test runs at different operating conditions.

Grid generation methodology and CFD simulations in sliding vane compressors and expanders

NASA Astrophysics Data System (ADS)

Bianchi, Giuseppe; Rane, Sham; Kovacevic, Ahmed; Cipollone, Roberto; Murgia, Stefano; Contaldi, Giulio

2017-08-01

The limiting factor for the employment of advanced 3D CFD tools in the analysis and design of rotary vane machines is the unavailability of methods for generation of computational grids suitable for fast and reliable numerical analysis. The paper addresses this challenge presenting the development of an analytical grid generation for vane machines that is based on the user defined nodal displacement. In particular, mesh boundaries are defined as parametric curves generated using trigonometrical modelling of the axial cross section of the machine while the distribution of computational nodes is performed using algebraic algorithms with transfinite interpolation, post orthogonalisation and smoothing. Algebraic control functions are introduced for distribution of nodes on the rotor and casing boundaries in order to achieve good grid quality in terms of cell size and expansion. In this way, the moving and deforming fluid domain of the sliding vane machine is discretized and the conservation of intrinsic quantities in ensured by maintaining the cell connectivity and structure. For validation of generated grids, a mid-size air compressor and a small-scale expander for Organic Rankine Cycle applications have been investigated in this paper. Remarks on implementation of the mesh motion algorithm, stability and robustness experienced with the ANSYS CFX solver as well as the obtained flow results are presented.

An incremental strategy for calculating consistent discrete CFD sensitivity derivatives

NASA Technical Reports Server (NTRS)

Korivi, Vamshi Mohan; Taylor, Arthur C., III; Newman, Perry A.; Hou, Gene W.; Jones, Henry E.

1992-01-01

In this preliminary study involving advanced computational fluid dynamic (CFD) codes, an incremental formulation, also known as the 'delta' or 'correction' form, is presented for solving the very large sparse systems of linear equations which are associated with aerodynamic sensitivity analysis. For typical problems in 2D, a direct solution method can be applied to these linear equations which are associated with aerodynamic sensitivity analysis. For typical problems in 2D, a direct solution method can be applied to these linear equations in either the standard or the incremental form, in which case the two are equivalent. Iterative methods appear to be needed for future 3D applications; however, because direct solver methods require much more computer memory than is currently available. Iterative methods for solving these equations in the standard form result in certain difficulties, such as ill-conditioning of the coefficient matrix, which can be overcome when these equations are cast in the incremental form; these and other benefits are discussed. The methodology is successfully implemented and tested in 2D using an upwind, cell-centered, finite volume formulation applied to the thin-layer Navier-Stokes equations. Results are presented for two laminar sample problems: (1) transonic flow through a double-throat nozzle; and (2) flow over an isolated airfoil.

Development of an aeroelastic methodology for surface morphing rotors

NASA Astrophysics Data System (ADS)

Cook, James R.

Helicopter performance capabilities are limited by maximum lift characteristics and vibratory loading. In high speed forward flight, dynamic stall and transonic flow greatly increase the amplitude of vibratory loads. Experiments and computational simulations alike have indicated that a variety of active rotor control devices are capable of reducing vibratory loads. For example, periodic blade twist and flap excitation have been optimized to reduce vibratory loads in various rotors. Airfoil geometry can also be modified in order to increase lift coefficient, delay stall, or weaken transonic effects. To explore the potential benefits of active controls, computational methods are being developed for aeroelastic rotor evaluation, including coupling between computational fluid dynamics (CFD) and computational structural dynamics (CSD) solvers. In many contemporary CFD/CSD coupling methods it is assumed that the airfoil is rigid to reduce the interface by single dimension. Some methods retain the conventional one-dimensional beam model while prescribing an airfoil shape to simulate active chord deformation. However, to simulate the actual response of a compliant airfoil it is necessary to include deformations that originate not only from control devices (such as piezoelectric actuators), but also inertial forces, elastic stresses, and aerodynamic pressures. An accurate representation of the physics requires an interaction with a more complete representation of loads and geometry. A CFD/CSD coupling methodology capable of communicating three-dimensional structural deformations and a distribution of aerodynamic forces over the wetted blade surface has not yet been developed. In this research an interface is created within the Fully Unstructured Navier-Stokes (FUN3D) solver that communicates aerodynamic forces on the blade surface to University of Michigan's Nonlinear Active Beam Solver (UM/NLABS -- referred to as NLABS in this thesis). Interface routines are developed for transmission of force and deflection information to achieve an aeroelastic coupling updated at each time step. The method is validated first by comparing the integrated aerodynamic work at CFD and CSD nodes to verify work conservation across the interface. Second, the method is verified by comparing the sectional blade loads and deflections of a rotor in hover and in forward flight with experimental data. Finally, stability analyses for pitch/plunge flutter and camber flutter are performed with comprehensive CSD/low-order-aerodynamics and tightly coupled CFD/CSD simulations and compared to analytical solutions of Peters' thin airfoil theory to verify proper aeroelastic behavior. The effects of simple harmonic camber actuation are examined and compared to the response predicted by Peters' finite-state (F-S) theory. In anticipation of active rotor experiments inside enclosed facilities, computational simulations are performed to evaluate the capability of CFD for accurately simulating flow inside enclosed volumes. A computational methodology for accurately simulating a rotor inside a test chamber is developed to determine the influence of test facility components and turbulence modeling and performance predictions. A number of factors that influence the physical accuracy of the simulation, such as temporal resolution, grid resolution, and aeroelasticity are also evaluated.

Aeroservoelastic and Flight Dynamics Analysis Using Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Arena, Andrew S., Jr.

1999-01-01

This document in large part is based on the Masters Thesis of Cole Stephens. The document encompasses a variety of technical and practical issues involved when using the STARS codes for Aeroservoelastic analysis of vehicles. The document covers in great detail a number of technical issues and step-by-step details involved in the simulation of a system where aerodynamics, structures and controls are tightly coupled. Comparisons are made to a benchmark experimental program conducted at NASA Langley. One of the significant advantages of the methodology detailed is that as a result of the technique used to accelerate the CFD-based simulation, a systems model is produced which is very useful for developing the control law strategy, and subsequent high-speed simulations.

Convergence Acceleration and Documentation of CFD Codes for Turbomachinery Applications

NASA Technical Reports Server (NTRS)

Marquart, Jed E.

2005-01-01

The development and analysis of turbomachinery components for industrial and aerospace applications has been greatly enhanced in recent years through the advent of computational fluid dynamics (CFD) codes and techniques. Although the use of this technology has greatly reduced the time required to perform analysis and design, there still remains much room for improvement in the process. In particular, there is a steep learning curve associated with most turbomachinery CFD codes, and the computation times need to be reduced in order to facilitate their integration into standard work processes. Two turbomachinery codes have recently been developed by Dr. Daniel Dorney (MSFC) and Dr. Douglas Sondak (Boston University). These codes are entitled Aardvark (for 2-D and quasi 3-D simulations) and Phantom (for 3-D simulations). The codes utilize the General Equation Set (GES), structured grid methodology, and overset O- and H-grids. The codes have been used with success by Drs. Dorney and Sondak, as well as others within the turbomachinery community, to analyze engine components and other geometries. One of the primary objectives of this study was to establish a set of parametric input values which will enhance convergence rates for steady state simulations, as well as reduce the runtime required for unsteady cases. The goal is to reduce the turnaround time for CFD simulations, thus permitting more design parametrics to be run within a given time period. In addition, other code enhancements to reduce runtimes were investigated and implemented. The other primary goal of the study was to develop enhanced users manuals for Aardvark and Phantom. These manuals are intended to answer most questions for new users, as well as provide valuable detailed information for the experienced user. The existence of detailed user s manuals will enable new users to become proficient with the codes, as well as reducing the dependency of new users on the code authors. In order to achieve the objectives listed, the following tasks were accomplished: 1) Parametric Study Of Preconditioning Parameters And Other Code Inputs; 2) Code Modifications To Reduce Runtimes; 3) Investigation Of Compiler Options To Reduce Code Runtime; and 4) Development/Enhancement of Users Manuals for Aardvark and Phantom

An Inducer CFD Solution and Effects Associated with Cavitation

NASA Technical Reports Server (NTRS)

Pervaiz, Mehtab M.; Garrett, J.; Kuryla, J.

1993-01-01

This presentation describes a CFD analysis for an Alternate Turbopump Development (ATD) configuration. The analysis consists of a coupled configuration of the inducer and impeller. The work presented here is a joint collaboration of J. Garrett, J. Kuryla and myself.

Prediction of dosage-based parameters from the puff dispersion of airborne materials in urban environments using the CFD-RANS methodology

NASA Astrophysics Data System (ADS)

Efthimiou, G. C.; Andronopoulos, S.; Bartzis, J. G.

2018-02-01

One of the key issues of recent research on the dispersion inside complex urban environments is the ability to predict dosage-based parameters from the puff release of an airborne material from a point source in the atmospheric boundary layer inside the built-up area. The present work addresses the question of whether the computational fluid dynamics (CFD)-Reynolds-averaged Navier-Stokes (RANS) methodology can be used to predict ensemble-average dosage-based parameters that are related with the puff dispersion. RANS simulations with the ADREA-HF code were, therefore, performed, where a single puff was released in each case. The present method is validated against the data sets from two wind-tunnel experiments. In each experiment, more than 200 puffs were released from which ensemble-averaged dosage-based parameters were calculated and compared to the model's predictions. The performance of the model was evaluated using scatter plots and three validation metrics: fractional bias, normalized mean square error, and factor of two. The model presented a better performance for the temporal parameters (i.e., ensemble-average times of puff arrival, peak, leaving, duration, ascent, and descent) than for the ensemble-average dosage and peak concentration. The majority of the obtained values of validation metrics were inside established acceptance limits. Based on the obtained model performance indices, the CFD-RANS methodology as implemented in the code ADREA-HF is able to predict the ensemble-average temporal quantities related to transient emissions of airborne material in urban areas within the range of the model performance acceptance criteria established in the literature. The CFD-RANS methodology as implemented in the code ADREA-HF is also able to predict the ensemble-average dosage, but the dosage results should be treated with some caution; as in one case, the observed ensemble-average dosage was under-estimated slightly more than the acceptance criteria. Ensemble-average peak concentration was systematically underpredicted by the model to a degree higher than the allowable by the acceptance criteria, in 1 of the 2 wind-tunnel experiments. The model performance depended on the positions of the examined sensors in relation to the emission source and the buildings configuration. The work presented in this paper was carried out (partly) within the scope of COST Action ES1006 "Evaluation, improvement, and guidance for the use of local-scale emergency prediction and response tools for airborne hazards in built environments".

Design of Experiments for Both Experimental and Analytical Study of Exhaust Plume Effects on Sonic Boom

NASA Technical Reports Server (NTRS)

Castner, Raymond S.

2009-01-01

Computational fluid dynamics (CFD) analysis has been performed to study the plume effects on sonic boom signature for isolated nozzle configurations. The objectives of these analyses were to provide comparison to past work using modern CFD analysis tools, to investigate the differences of high aspect ratio nozzles to circular (axisymmetric) nozzles, and to report the effects of under expanded nozzle operation on boom signature. CFD analysis was used to address the plume effects on sonic boom signature from a baseline exhaust nozzle. Nearfield pressure signatures were collected for nozzle pressure ratios (NPRs) between 6 and 10. A computer code was used to extrapolate these signatures to a ground-observed sonic boom N-wave. Trends show that there is a reduction in sonic boom N-wave signature as NPR is increased from 6 to 10. As low boom designs are developed and improved, there will be a need for understanding the interaction between the aircraft boat tail shocks and the exhaust nozzle plume. These CFD analyses will provide a baseline study for future analysis efforts. For further study, a design of experiments has been conducted to develop a hybrid method where both CFD and small scale wind tunnel testing will validate the observed trends. The CFD and testing will be used to screen a number of factors which are important to low boom propulsion integration, including boat tail angle, nozzle geometry, and the effect of spacing and stagger on nozzle pairs. To design the wind tunnel experiment, CFD was instrumental in developing a model which would provide adequate space to observe the nozzle and boat tail shock structure without interference from the wind tunnel walls.

Data resulting from the CFD analysis of ten window frames according to the UNI EN ISO 10077-2.

PubMed

Baglivo, Cristina; Malvoni, Maria; Congedo, Paolo Maria

2016-09-01

Data are related to the numerical simulation performed in the study entitled "CFD modeling to evaluate the thermal performances of window frames in accordance with the ISO 10077" (Malvoni et al., 2016) [1]. The paper focuses on the results from a two-dimensional numerical analysis for ten frame sections suggested by the ISO 10077-2 and performed using GAMBIT 2.2 and ANSYS FLUENT 14.5 CFD code. The dataset specifically includes information about the CFD setup and boundary conditions considered as the input values of the simulations. The trend of the isotherms points out the different impacts on the thermal behaviour of all sections with air solid material or ideal gas into the cavities.

Development and Implementation of CFD-Informed Models for the Advanced Subchannel Code CTF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blyth, Taylor S.; Avramova, Maria

The research described in this PhD thesis contributes to the development of efficient methods for utilization of high-fidelity models and codes to inform low-fidelity models and codes in the area of nuclear reactor core thermal-hydraulics. The objective is to increase the accuracy of predictions of quantities of interests using high-fidelity CFD models while preserving the efficiency of low-fidelity subchannel core calculations. An original methodology named Physics- based Approach for High-to-Low Model Information has been further developed and tested. The overall physical phenomena and corresponding localized effects, which are introduced by the presence of spacer grids in light water reactor (LWR)more » cores, are dissected in corresponding four building basic processes, and corresponding models are informed using high-fidelity CFD codes. These models are a spacer grid-directed cross-flow model, a grid-enhanced turbulent mixing model, a heat transfer enhancement model, and a spacer grid pressure loss model. The localized CFD-models are developed and tested using the CFD code STAR-CCM+, and the corresponding global model development and testing in sub-channel formulation is performed in the thermal- hydraulic subchannel code CTF. The improved CTF simulations utilize data-files derived from CFD STAR-CCM+ simulation results covering the spacer grid design desired for inclusion in the CTF calculation. The current implementation of these models is examined and possibilities for improvement and further development are suggested. The validation experimental database is extended by including the OECD/NRC PSBT benchmark data. The outcome is an enhanced accuracy of CTF predictions while preserving the computational efficiency of a low-fidelity subchannel code.« less

Development and Implementation of CFD-Informed Models for the Advanced Subchannel Code CTF

NASA Astrophysics Data System (ADS)

Blyth, Taylor S.

The research described in this PhD thesis contributes to the development of efficient methods for utilization of high-fidelity models and codes to inform low-fidelity models and codes in the area of nuclear reactor core thermal-hydraulics. The objective is to increase the accuracy of predictions of quantities of interests using high-fidelity CFD models while preserving the efficiency of low-fidelity subchannel core calculations. An original methodology named Physics-based Approach for High-to-Low Model Information has been further developed and tested. The overall physical phenomena and corresponding localized effects, which are introduced by the presence of spacer grids in light water reactor (LWR) cores, are dissected in corresponding four building basic processes, and corresponding models are informed using high-fidelity CFD codes. These models are a spacer grid-directed cross-flow model, a grid-enhanced turbulent mixing model, a heat transfer enhancement model, and a spacer grid pressure loss model. The localized CFD-models are developed and tested using the CFD code STAR-CCM+, and the corresponding global model development and testing in sub-channel formulation is performed in the thermal-hydraulic subchannel code CTF. The improved CTF simulations utilize data-files derived from CFD STAR-CCM+ simulation results covering the spacer grid design desired for inclusion in the CTF calculation. The current implementation of these models is examined and possibilities for improvement and further development are suggested. The validation experimental database is extended by including the OECD/NRC PSBT benchmark data. The outcome is an enhanced accuracy of CTF predictions while preserving the computational efficiency of a low-fidelity subchannel code.

Three dimensional, numerical analysis of an elasto hydrodynamic lubrication using fluid structure interaction (FSI) approach

NASA Astrophysics Data System (ADS)

Hanoca, P.; Ramakrishna, H. V.

2018-03-01

This work is related to develop a methodology to model and simulate the TEHD using the sequential application of CFD and CSD. The FSI analyses are carried out using ANSYS Workbench. In this analysis steady state, 3D Navier-Stoke equations along with energy equation are solved. Liquid properties are introduced where the viscosity and density are the function of pressure and temperature. The cavitation phenomenon is adopted in the analysis. Numerical analysis has been carried at different speeds and surfaces temperatures. During the analysis, it was found that as speed increases, hydrodynamic pressures will also increases. The pressure profile obtained from the Roelands equation is more sensitive to the temperature as compared to the Barus equation. The stress distributions specify the significant positions in the bearing structure. The developed method is capable of giving latest approaching into the physics of elasto hydrodynamic lubrication.

Comparison of 4D Phase-Contrast MRI Flow Measurements to Computational Fluid Dynamics Simulations of Cerebrospinal Fluid Motion in the Cervical Spine

PubMed Central

Yiallourou, Theresia I.; Kröger, Jan Robert; Stergiopulos, Nikolaos; Maintz, David

2012-01-01

Cerebrospinal fluid (CSF) dynamics in the cervical spinal subarachnoid space (SSS) have been thought to be important to help diagnose and assess craniospinal disorders such as Chiari I malformation (CM). In this study we obtained time-resolved three directional velocity encoded phase-contrast MRI (4D PC MRI) in three healthy volunteers and four CM patients and compared the 4D PC MRI measurements to subject-specific 3D computational fluid dynamics (CFD) simulations. The CFD simulations considered the geometry to be rigid-walled and did not include small anatomical structures such as nerve roots, denticulate ligaments and arachnoid trabeculae. Results were compared at nine axial planes along the cervical SSS in terms of peak CSF velocities in both the cranial and caudal direction and visual interpretation of thru-plane velocity profiles. 4D PC MRI peak CSF velocities were consistently greater than the CFD peak velocities and these differences were more pronounced in CM patients than in healthy subjects. In the upper cervical SSS of CM patients the 4D PC MRI quantified stronger fluid jets than the CFD. Visual interpretation of the 4D PC MRI thru-plane velocity profiles showed greater pulsatile movement of CSF in the anterior SSS in comparison to the posterior and reduction in local CSF velocities near nerve roots. CFD velocity profiles were relatively uniform around the spinal cord for all subjects. This study represents the first comparison of 4D PC MRI measurements to CFD of CSF flow in the cervical SSS. The results highlight the utility of 4D PC MRI for evaluation of complex CSF dynamics and the need for improvement of CFD methodology. Future studies are needed to investigate whether integration of fine anatomical structures and gross motion of the brain and/or spinal cord into the computational model will lead to a better agreement between the two techniques. PMID:23284970

Methodology for sensitivity analysis, approximate analysis, and design optimization in CFD for multidisciplinary applications. [computational fluid dynamics

NASA Technical Reports Server (NTRS)

Taylor, Arthur C., III; Hou, Gene W.

1992-01-01

Fundamental equations of aerodynamic sensitivity analysis and approximate analysis for the two dimensional thin layer Navier-Stokes equations are reviewed, and special boundary condition considerations necessary to apply these equations to isolated lifting airfoils on 'C' and 'O' meshes are discussed in detail. An efficient strategy which is based on the finite element method and an elastic membrane representation of the computational domain is successfully tested, which circumvents the costly 'brute force' method of obtaining grid sensitivity derivatives, and is also useful in mesh regeneration. The issue of turbulence modeling is addressed in a preliminary study. Aerodynamic shape sensitivity derivatives are efficiently calculated, and their accuracy is validated on two viscous test problems, including: (1) internal flow through a double throat nozzle, and (2) external flow over a NACA 4-digit airfoil. An automated aerodynamic design optimization strategy is outlined which includes the use of a design optimization program, an aerodynamic flow analysis code, an aerodynamic sensitivity and approximate analysis code, and a mesh regeneration and grid sensitivity analysis code. Application of the optimization methodology to the two test problems in each case resulted in a new design having a significantly improved performance in the aerodynamic response of interest.

CFD and ventilation research.

PubMed

Li, Y; Nielsen, P V

2011-12-01

There has been a rapid growth of scientific literature on the application of computational fluid dynamics (CFD) in the research of ventilation and indoor air science. With a 1000-10,000 times increase in computer hardware capability in the past 20 years, CFD has become an integral part of scientific research and engineering development of complex air distribution and ventilation systems in buildings. This review discusses the major and specific challenges of CFD in terms of turbulence modelling, numerical approximation, and boundary conditions relevant to building ventilation. We emphasize the growing need for CFD verification and validation, suggest ongoing needs for analytical and experimental methods to support the numerical solutions, and discuss the growing capacity of CFD in opening up new research areas. We suggest that CFD has not become a replacement for experiment and theoretical analysis in ventilation research, rather it has become an increasingly important partner. We believe that an effective scientific approach for ventilation studies is still to combine experiments, theory, and CFD. We argue that CFD verification and validation are becoming more crucial than ever as more complex ventilation problems are solved. It is anticipated that ventilation problems at the city scale will be tackled by CFD in the next 10 years. © 2011 John Wiley & Sons A/S.

CFD in the context of IHPTET: The Integrated High Performance Turbine Technology Program

NASA Technical Reports Server (NTRS)

Simoneau, Robert J.; Hudson, Dale A.

1989-01-01

The Integrated High Performance Turbine Engine Technology (IHPTET) Program is an integrated DOD/NASA technology program designed to double the performance capability of today's most advanced military turbine engines as we enter the twenty-first century. Computational Fluid Dynamics (CFD) is expected to play an important role in the design/analysis of specific configurations within this complex machine. In order to do this, a plan is being developed to ensure the timely impact of CFD on IHPTET. The developing philosphy of CFD in the context of IHPTET is discussed. The key elements in the developing plan and specific examples of state-of-the-art CFD efforts which are IHPTET turbine engine relevant are discussed.

Assessment of Computational Fluid Dynamics (CFD) Models for Shock Boundary-Layer Interaction

NASA Technical Reports Server (NTRS)

DeBonis, James R.; Oberkampf, William L.; Wolf, Richard T.; Orkwis, Paul D.; Turner, Mark G.; Babinsky, Holger

2011-01-01

A workshop on the computational fluid dynamics (CFD) prediction of shock boundary-layer interactions (SBLIs) was held at the 48th AIAA Aerospace Sciences Meeting. As part of the workshop numerous CFD analysts submitted solutions to four experimentally measured SBLIs. This paper describes the assessment of the CFD predictions. The assessment includes an uncertainty analysis of the experimental data, the definition of an error metric and the application of that metric to the CFD solutions. The CFD solutions provided very similar levels of error and in general it was difficult to discern clear trends in the data. For the Reynolds Averaged Navier-Stokes methods the choice of turbulence model appeared to be the largest factor in solution accuracy. Large-eddy simulation methods produced error levels similar to RANS methods but provided superior predictions of normal stresses.

Analysis of Low-Speed Stall Aerodynamics of a Business Jets Wing Using STAR-CCM+

NASA Technical Reports Server (NTRS)

Bui, Trong

2016-01-01

Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted: to study the low-speed stall aerodynamics of a GIII aircrafts swept wing modified with (1) a laminar-flow wing glove, or (2) a seamless flap. The stall aerodynamics of these two different wing configurations were analyzed and compared with the unmodified baseline wing for low-speed flight. The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First AIAA CFD High-Lift Prediction Workshop.

Space shuttle main engine numerical modeling code modifications and analysis

NASA Technical Reports Server (NTRS)

Ziebarth, John P.

1988-01-01

The user of computational fluid dynamics (CFD) codes must be concerned with the accuracy and efficiency of the codes if they are to be used for timely design and analysis of complicated three-dimensional fluid flow configurations. A brief discussion of how accuracy and efficiency effect the CFD solution process is given. A more detailed discussion of how efficiency can be enhanced by using a few Cray Research Inc. utilities to address vectorization is presented and these utilities are applied to a three-dimensional Navier-Stokes CFD code (INS3D).

Analytic Corrections to CFD Heating Predictions Accounting for Changes in Surface Catalysis. Part II

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Inger, George R.

1996-01-01

A new approach for combining the insight afforded by integral boundary-layer analysis with comprehensive (but time intensive) computational fluid dynamic (CFD) flowfield solutions of the thin-layer Navier-Stokes equations is described. The approach extracts CFD derived quantities at the wall and at the boundary layer edge for inclusion in a post-processing boundary-layer analysis. It allows a designer at a work-station to address two questions, given a single CFD solution. (1) How much does the heating change for a thermal protection system (TPS) with different catalytic properties than was used in the original CFD solution? (2) How does the heating change at the interface of two different TPS materials with an abrupt change in catalytic efficiency? The answer to the second question is particularly important, because abrupt changes from low to high catalytic efficiency can lead to localized increase in heating which exceeds the usually conservative estimate provided by a fully catalytic wall assumption. Capabilities of this approach for application to Reusable Launch Vehicle (RLV) design are demonstrated. If the definition of surface catalysis is uncertain early in the design process, results show that fully catalytic wall boundary conditions provide the best baseline for CFD design points.

Simulations of SSLV Ascent and Debris Transport

NASA Technical Reports Server (NTRS)

Rogers, Stuart; Aftosmis, Michael; Murman, Scott; Chan, William; Gomez, Ray; Gomez, Ray; Vicker, Darby; Stuart, Phil

2006-01-01

A viewgraph presentation on Computational Fluid Dynamic (CFD) Simulation of Space Shuttle Launch Vehicle (SSLV) ascent and debris transport analysis is shown. The topics include: 1) CFD simulations of the Space Shuttle Launch Vehicle ascent; 2) Debris transport analysis; 3) Debris aerodynamic modeling; and 4) Other applications.

MHK Hydrofoils Design, Wind Tunnel Optimization and CFD Analysis Report for the Aquantis 2.5MW Ocean Current Generation Device

DOE Data Explorer

Shiu, Henry; Swales, Henry; Van Damn, Case

2015-06-03

Dataset contains MHK Hydrofoils Design and Optimization and CFD Analysis Report for the Aquantis 2.5 MW Ocean Current Generation Device, as well as MHK Hydrofoils Wind Tunnel Test Plan and Checkout Test Report.

Numerical Simulation of Non-Rotating and Rotating Coolant Channel Flow Fields. Part 1

NASA Technical Reports Server (NTRS)

Rigby, David L.

2000-01-01

Future generations of ultra high bypass-ratio jet engines will require far higher pressure ratios and operating temperatures than those of current engines. For the foreseeable future, engine materials will not be able to withstand the high temperatures without some form of cooling. In particular the turbine blades, which are under high thermal as well as mechanical loads, must be cooled. Cooling of turbine blades is achieved by bleeding air from the compressor stage of the engine through complicated internal passages in the turbine blades (internal cooling, including jet-impingement cooling) and by bleeding small amounts of air into the boundary layer of the external flow through small discrete holes on the surface of the blade (film cooling and transpiration cooling). The cooling must be done using a minimum amount of air or any increases in efficiency gained through higher operating temperature will be lost due to added load on the compressor stage. Turbine cooling schemes have traditionally been based on extensive empirical data bases, quasi-one-dimensional computational fluid dynamics (CFD) analysis, and trial and error. With improved capabilities of CFD, these traditional methods can be augmented by full three-dimensional simulations of the coolant flow to predict in detail the heat transfer and metal temperatures. Several aspects of turbine coolant flows make such application of CFD difficult, thus a highly effective CFD methodology must be used. First, high resolution of the flow field is required to attain the needed accuracy for heat transfer predictions, making highly efficient flow solvers essential for such computations. Second, the geometries of the flow passages are complicated but must be modeled accurately in order to capture all important details of the flow. This makes grid generation and grid quality important issues. Finally, since coolant flows are turbulent and separated the effects of turbulence must be modeled with a low Reynolds number turbulence model to accurately predict details of heat transfer.

A Mixed-Fidelity Approach for Design of Low-Boom Supersonic Aircraft

NASA Technical Reports Server (NTRS)

Li, Wu; Shields, Elwood; Geiselhart, Karl A.

2010-01-01

This paper documents a mixed-fidelity approach for the design of low-boom supersonic aircraft as a viable approach for designing a practical low-boom supersonic configuration. A low-boom configuration that is based on low-fidelity analysis is used as the baseline. Tail lift is included to help tailor the aft portion of the ground signature. A comparison of low- and high-fidelity analysis results demonstrates the necessity of using computational fluid dynamics (CFD) analysis in a low-boom supersonic configuration design process. The fuselage shape is modified iteratively to obtain a configuration with a CFD equivalent-area distribution that matches a predetermined low-boom target distribution. The mixed-fidelity approach can easily refine the low-fidelity low-boom baseline into a low-boom configuration with the use of CFD equivalent-area analysis. The ground signature of the final configuration is calculated by using a state-of-the-art CFD-based boom analysis method that generates accurate midfield pressure distributions for propagation to the ground with ray tracing. The ground signature that is propagated from a midfield pressure distribution has a shaped ramp front, which is similar to the ground signature that is propagated from the CFD equivalent-area distribution. This result confirms the validity of the low-boom supersonic configuration design by matching a low-boom equivalent-area target, which is easier to accomplish than matching a low-boom midfield pressure target.

Problems Related to Parallelization of CFD Algorithms on GPU, Multi-GPU and Hybrid Architectures

NASA Astrophysics Data System (ADS)

Biazewicz, Marek; Kurowski, Krzysztof; Ludwiczak, Bogdan; Napieraia, Krystyna

2010-09-01

Computational Fluid Dynamics (CFD) is one of the branches of fluid mechanics, which uses numerical methods and algorithms to solve and analyze fluid flows. CFD is used in various domains, such as oil and gas reservoir uncertainty analysis, aerodynamic body shapes optimization (e.g. planes, cars, ships, sport helmets, skis), natural phenomena analysis, numerical simulation for weather forecasting or realistic visualizations. CFD problem is very complex and needs a lot of computational power to obtain the results in a reasonable time. We have implemented a parallel application for two-dimensional CFD simulation with a free surface approximation (MAC method) using new hardware architectures, in particular multi-GPU and hybrid computing environments. For this purpose we decided to use NVIDIA graphic cards with CUDA environment due to its simplicity of programming and good computations performance. We used finite difference discretization of Navier-Stokes equations, where fluid is propagated over an Eulerian Grid. In this model, the behavior of the fluid inside the cell depends only on the properties of local, surrounding cells, therefore it is well suited for the GPU-based architecture. In this paper we demonstrate how to use efficiently the computing power of GPUs for CFD. Additionally, we present some best practices to help users analyze and improve the performance of CFD applications executed on GPU. Finally, we discuss various challenges around the multi-GPU implementation on the example of matrix multiplication.

CFD analysis of a diaphragm free-piston Stirling cryocooler

NASA Astrophysics Data System (ADS)

Caughley, Alan; Sellier, Mathieu; Gschwendtner, Michael; Tucker, Alan

2016-10-01

This paper presents a Computational Fluid Dynamics (CFD) analysis of a novel free-piston Stirling cryocooler that uses a pair of metal diaphragms to seal and suspend the displacer. The diaphragms allow the displacer to move without rubbing or moving seals. When coupled to a metal diaphragm pressure wave generator, the system produces a complete Stirling cryocooler with no rubbing parts in the working gas space. Initial modelling of this concept using the Sage modelling tool indicated the potential for a useful cryocooler. A proof-of-concept prototype was constructed and achieved cryogenic temperatures. A second prototype was designed and constructed using the experience gained from the first. The prototype produced 29 W of cooling at 77 K and reached a no-load temperature of 56 K. The diaphragm's large diameter and short stroke produces a significant radial component to the oscillating flow fields inside the cryocooler which were not modelled in the one-dimensional analysis tool Sage that was used to design the prototypes. Compared with standard pistons, the diaphragm geometry increases the gas-to-wall heat transfer due to the higher velocities and smaller hydraulic diameters. A Computational Fluid Dynamics (CFD) model of the cryocooler was constructed to understand the underlying fluid-dynamics and heat transfer mechanisms with the aim of further improving performance. The CFD modelling of the heat transfer in the radial flow fields created by the diaphragms shows the possibility of utilizing the flat geometry for heat transfer, reducing the need for, and the size of, expensive heat exchangers. This paper presents details of a CFD analysis used to model the flow and gas-to-wall heat transfer inside the second prototype cryocooler, including experimental validation of the CFD to produce a robust analysis.

Haemodynamic imaging of thoracic stent-grafts by computational fluid dynamics (CFD): presentation of a patient-specific method combining magnetic resonance imaging and numerical simulations.

PubMed

Midulla, Marco; Moreno, Ramiro; Baali, Adil; Chau, Ming; Negre-Salvayre, Anne; Nicoud, Franck; Pruvo, Jean-Pierre; Haulon, Stephan; Rousseau, Hervé

2012-10-01

In the last decade, there was been increasing interest in finding imaging techniques able to provide a functional vascular imaging of the thoracic aorta. The purpose of this paper is to present an imaging method combining magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) to obtain a patient-specific haemodynamic analysis of patients treated by thoracic endovascular aortic repair (TEVAR). MRI was used to obtain boundary conditions. MR angiography (MRA) was followed by cardiac-gated cine sequences which covered the whole thoracic aorta. Phase contrast imaging provided the inlet and outlet profiles. A CFD mesh generator was used to model the arterial morphology, and wall movements were imposed according to the cine imaging. CFD runs were processed using the finite volume (FV) method assuming blood as a homogeneous Newtonian fluid. Twenty patients (14 men; mean age 62.2 years) with different aortic lesions were evaluated. Four-dimensional mapping of velocity and wall shear stress were obtained, depicting different patterns of flow (laminar, turbulent, stenosis-like) and local alterations of parietal stress in-stent and along the native aorta. A computational method using a combined approach with MRI appears feasible and seems promising to provide detailed functional analysis of thoracic aorta after stent-graft implantation. • Functional vascular imaging of the thoracic aorta offers new diagnostic opportunities • CFD can model vascular haemodynamics for clinical aortic problems • Combining CFD with MRI offers patient specific method of aortic analysis • Haemodynamic analysis of stent-grafts could improve clinical management and follow-up.

Patient-specific surgical planning and hemodynamic computational fluid dynamics optimization through free-form haptic anatomy editing tool (SURGEM).

PubMed

Pekkan, Kerem; Whited, Brian; Kanter, Kirk; Sharma, Shiva; de Zelicourt, Diane; Sundareswaran, Kartik; Frakes, David; Rossignac, Jarek; Yoganathan, Ajit P

2008-11-01

The first version of an anatomy editing/surgical planning tool (SURGEM) targeting anatomical complexity and patient-specific computational fluid dynamics (CFD) analysis is presented. Novel three-dimensional (3D) shape editing concepts and human-shape interaction technologies have been integrated to facilitate interactive surgical morphology alterations, grid generation and CFD analysis. In order to implement "manual hemodynamic optimization" at the surgery planning phase for patients with congenital heart defects, these tools are applied to design and evaluate possible modifications of patient-specific anatomies. In this context, anatomies involve complex geometric topologies and tortuous 3D blood flow pathways with multiple inlets and outlets. These tools make it possible to freely deform the lumen surface and to bend and position baffles through real-time, direct manipulation of the 3D models with both hands, thus eliminating the tedious and time-consuming phase of entering the desired geometry using traditional computer-aided design (CAD) systems. The 3D models of the modified anatomies are seamlessly exported and meshed for patient-specific CFD analysis. Free-formed anatomical modifications are quantified using an in-house skeletization based cross-sectional geometry analysis tool. Hemodynamic performance of the systematically modified anatomies is compared with the original anatomy using CFD. CFD results showed the relative importance of the various surgically created features such as pouch size, vena cave to pulmonary artery (PA) flare and PA stenosis. An interactive surgical-patch size estimator is also introduced. The combined design/analysis cycle time is used for comparing and optimizing surgical plans and improvements are tabulated. The reduced cost of patient-specific shape design and analysis process, made it possible to envision large clinical studies to assess the validity of predictive patient-specific CFD simulations. In this paper, model anatomical design studies are performed on a total of eight different complex patient specific anatomies. Using SURGEM, more than 30 new anatomical designs (or candidate configurations) are created, and the corresponding user times presented. CFD performances for eight of these candidate configurations are also presented.

Development and Validation of High Performance Unshrouded Centrifugal Impeller

NASA Technical Reports Server (NTRS)

Chen, Wei-Chung; Williams, M.; Paris, John K.; Prueger, G. H.; Williams, Robert; Turner, James E. (Technical Monitor)

2001-01-01

The feasibility of using a two-stage unshrouded impeller turbopump to replace the current three-stage reusable launch vehicle engine shrouded impeller hydrogen pump has been evaluated from the standpoint of turbopump weight reduction and overall payload improvement. These advantages are a by-product of the higher tip speeds that an unshrouded impeller can sustain. The issues associated with the effect of unshrouded impeller tip clearance on pump efficiency and head have been evaluated with one-dimensional tools and full three-dimensional rotordynamic fluid reaction forces and coefficients have been established through time dependent computational fluid dynamics (CFD) simulation of the whole 360 degree impeller with different rotor eccentricities and whirling ratios. Unlike the shrouded impeller, the unshrouded impeller forces are evaluated as the sum of the pressure forces on the blade and the pressure forces on the hub using the CFD results. The turbopump axial thrust control has been optimized by adjusting the first stage impeller backend wear ring seal diameter and diverting the second stage backend balance piston flow to the proper location. The structural integrity associated with the high tip speed has been checked by analyzing a 3D-Finite Element Model at maximum design conditions (6% higher than the design speed). This impeller was fabricated and tested in the NASA Marshall Space Flight Center water-test rig. The experimental data will be compared with the analytical predictions and presented in another paper. The experimental data provides validation data for the numerical design and analysis methodology. The validated numerical methodology can be used to help design different unshrouded impeller configurations.

Hi-alpha forebody design. Part 1: Methodology base and initial parametrics

NASA Technical Reports Server (NTRS)

Mason, William H.; Ravi, R.

1992-01-01

The use of Computational Fluid Dynamics (CFD) has been investigated for the analysis and design of aircraft forebodies at high angle of attack combined with sideslip. The results of the investigation show that CFD has reached a level of development where computational methods can be used for high angle of attack aerodynamic design. The classic wind tunnel experiment for the F-5A forebody directional stability has been reproduced computationally over an angle of attack range from 10 degrees to 45 degrees, and good agreement with experimental data was obtained. Computations have also been made at combined angle of attack and sideslip over a chine forebody, demonstrating the qualitative features of the flow, although not producing good agreement with measured experimental pressure distributions. The computations were performed using the code known as cfl3D for both the Euler equations and the Reynolds equations using a form of the Baldwin-Lomax turbulence model. To study the relation between forebody shape and directional stability characteristics, a generic parametric forebody model has been defined which provides a simple analytic math model with flexibility to capture the key shape characteristics of the entire range of forebodies of interest, including chines.

High-speed aerodynamic design of space vehicle and required hypersonic wind tunnel facilities

NASA Astrophysics Data System (ADS)

Sakakibara, Seizou; Hozumi, Kouichi; Soga, Kunio; Nomura, Shigeaki

Problems associated with the aerodynamic design of space vehicles with emphasis of the role of hypersonic wind tunnel facilities in the development of the vehicle are considered. At first, to identify wind tunnel and computational fluid dynamics (CFD) requirements, operational environments are postulated for hypervelocity vehicles. Typical flight corridors are shown with the associated flow density: real gas effects, low density flow, and non-equilibrium flow. Based on an evaluation of these flight regimes and consideration of the operational requirements, the wind tunnel testing requirements for the aerodynamic design are examined. Then, the aerodynamic design logic and optimization techniques to develop and refine the configurations in a traditional phased approach based on the programmatic design of space vehicle are considered. Current design methodology for the determination of aerodynamic characteristics for designing the space vehicle, i.e., (1) ground test data, (2) numerical flow field solutions and (3) flight test data, are also discussed. Based on these considerations and by identifying capabilities and limits of experimental and computational methods, the role of a large conventional hypersonic wind tunnel and the high enthalpy tunnel and the interrelationship of the wind tunnels and CFD methods in actual aerodynamic design and analysis are discussed.

The development and application of CFD technology in mechanical engineering

NASA Astrophysics Data System (ADS)

Wei, Yufeng

2017-12-01

Computational Fluid Dynamics (CFD) is an analysis of the physical phenomena involved in fluid flow and heat conduction by computer numerical calculation and graphical display. The numerical method simulates the complexity of the physical problem and the precision of the numerical solution, which is directly related to the hardware speed of the computer and the hardware such as memory. With the continuous improvement of computer performance and CFD technology, it has been widely applied to the field of water conservancy engineering, environmental engineering and industrial engineering. This paper summarizes the development process of CFD, the theoretical basis, the governing equations of fluid mechanics, and introduces the various methods of numerical calculation and the related development of CFD technology. Finally, CFD technology in the mechanical engineering related applications are summarized. It is hoped that this review will help researchers in the field of mechanical engineering.

CFD in the context of IHPTET - The Integrated High Performance Turbine Engine Technology Program

NASA Technical Reports Server (NTRS)

Simoneau, Robert J.; Hudson, Dale A.

1989-01-01

The Integrated High Performance Turbine Engine Technology (IHPTET) Program is an integrated DOD/NASA technology program designed to double the performance capability of today's most advanced military turbine engines as we enter the twenty-first century. Computational Fluid Dynamics (CFD) is expected to play an important role in the design/analysis of specific configurations within this complex machine. In order to do this, a plan is being developed to ensure the timely impact of CFD on IHPTET. The developing philosophy of CFD in the context of IHPTET is discussed. The key elements in the developing plan and specific examples of state-of-the-art CFD efforts which are IHPTET turbine engine relevant are discussed.

Methodology for Sensitivity Analysis, Approximate Analysis, and Design Optimization in CFD for Multidisciplinary Applications

NASA Technical Reports Server (NTRS)

Taylor, Arthur C., III; Hou, Gene W.

1996-01-01

An incremental iterative formulation together with the well-known spatially split approximate-factorization algorithm, is presented for solving the large, sparse systems of linear equations that are associated with aerodynamic sensitivity analysis. This formulation is also known as the 'delta' or 'correction' form. For the smaller two dimensional problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. However, iterative methods are needed for larger two-dimensional and three dimensional applications because direct methods require more computer memory than is currently available. Iterative methods for solving these equations in the standard form are generally unsatisfactory due to an ill-conditioned coefficient matrix; this problem is overcome when these equations are cast in the incremental form. The methodology is successfully implemented and tested using an upwind cell-centered finite-volume formulation applied in two dimensions to the thin-layer Navier-Stokes equations for external flow over an airfoil. In three dimensions this methodology is demonstrated with a marching-solution algorithm for the Euler equations to calculate supersonic flow over the High-Speed Civil Transport configuration (HSCT 24E). The sensitivity derivatives obtained with the incremental iterative method from a marching Euler code are used in a design-improvement study of the HSCT configuration that involves thickness. camber, and planform design variables.

Gradient-Based Aerodynamic Shape Optimization Using ADI Method for Large-Scale Problems

NASA Technical Reports Server (NTRS)

Pandya, Mohagna J.; Baysal, Oktay

1997-01-01

A gradient-based shape optimization methodology, that is intended for practical three-dimensional aerodynamic applications, has been developed. It is based on the quasi-analytical sensitivities. The flow analysis is rendered by a fully implicit, finite volume formulation of the Euler equations.The aerodynamic sensitivity equation is solved using the alternating-direction-implicit (ADI) algorithm for memory efficiency. A flexible wing geometry model, that is based on surface parameterization and platform schedules, is utilized. The present methodology and its components have been tested via several comparisons. Initially, the flow analysis for for a wing is compared with those obtained using an unfactored, preconditioned conjugate gradient approach (PCG), and an extensively validated CFD code. Then, the sensitivities computed with the present method have been compared with those obtained using the finite-difference and the PCG approaches. Effects of grid refinement and convergence tolerance on the analysis and shape optimization have been explored. Finally the new procedure has been demonstrated in the design of a cranked arrow wing at Mach 2.4. Despite the expected increase in the computational time, the results indicate that shape optimization, which require large numbers of grid points can be resolved with a gradient-based approach.

Methodology for sensitivity analysis, approximate analysis, and design optimization in CFD for multidisciplinary applications

NASA Technical Reports Server (NTRS)

Taylor, Arthur C., III; Hou, Gene W.

1993-01-01

In this study involving advanced fluid flow codes, an incremental iterative formulation (also known as the delta or correction form) together with the well-known spatially-split approximate factorization algorithm, is presented for solving the very large sparse systems of linear equations which are associated with aerodynamic sensitivity analysis. For smaller 2D problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. Iterative methods are needed for larger 2D and future 3D applications, however, because direct methods require much more computer memory than is currently available. Iterative methods for solving these equations in the standard form are generally unsatisfactory due to an ill-conditioning of the coefficient matrix; this problem can be overcome when these equations are cast in the incremental form. These and other benefits are discussed. The methodology is successfully implemented and tested in 2D using an upwind, cell-centered, finite volume formulation applied to the thin-layer Navier-Stokes equations. Results are presented for two sample airfoil problems: (1) subsonic low Reynolds number laminar flow; and (2) transonic high Reynolds number turbulent flow.

Multiscale integral analysis of a HT leakage in a fusion nuclear power plant

NASA Astrophysics Data System (ADS)

Velarde, M.; Fradera, J.; Perlado, J. M.; Zamora, I.; Martínez-Saban, E.; Colomer, C.; Briani, P.

2016-05-01

The present work presents an example of the application of an integral methodology based on a multiscale analysis that covers the whole tritium cycle within a nuclear fusion power plant, from a micro scale, analyzing key components where tritium is leaked through permeation, to a macro scale, considering its atmospheric transport. A leakage from the Nuclear Power Plants, (NPP) primary to the secondary side of a heat exchanger (HEX) is considered for the present example. Both primary and secondary loop coolants are assumed to be He. Leakage is placed inside the HEX, leaking tritium in elementary tritium (HT) form to the secondary loop where it permeates through the piping structural material to the exterior. The Heating Ventilation and Air Conditioning (HVAC) system removes the leaked tritium towards the NPP exhaust. The HEX is modelled with system codes and coupled to Computational Fluid Dynamic (CFD) to account for tritium dispersion inside the nuclear power plants buildings and in site environment. Finally, tritium dispersion is calculated with an atmospheric transport code and a dosimetry analysis is carried out. Results show how the implemented methodology is capable of assessing the impact of tritium from the microscale to the atmospheric scale including the dosimetric aspect.

3-D CFD Simulation and Validation of Oxygen-Rich Hydrocarbon Combustion in a Gas-Centered Swirl Coaxial Injector using a Flamelet-Based Approach

NASA Technical Reports Server (NTRS)

Richardson, Brian; Kenny, Jeremy

2015-01-01

Injector design is a critical part of the development of a rocket Thrust Chamber Assembly (TCA). Proper detailed injector design can maximize propulsion efficiency while minimizing the potential for failures in the combustion chamber. Traditional design and analysis methods for hydrocarbon-fuel injector elements are based heavily on empirical data and models developed from heritage hardware tests. Using this limited set of data produces challenges when trying to design a new propulsion system where the operating conditions may greatly differ from heritage applications. Time-accurate, Three-Dimensional (3-D) Computational Fluid Dynamics (CFD) modeling of combusting flows inside of injectors has long been a goal of the fluid analysis group at Marshall Space Flight Center (MSFC) and the larger CFD modeling community. CFD simulation can provide insight into the design and function of an injector that cannot be obtained easily through testing or empirical comparisons to existing hardware. However, the traditional finite-rate chemistry modeling approach utilized to simulate combusting flows for complex fuels, such as Rocket Propellant-2 (RP-2), is prohibitively expensive and time consuming even with a large amount of computational resources. MSFC has been working, in partnership with Streamline Numerics, Inc., to develop a computationally efficient, flamelet-based approach for modeling complex combusting flow applications. In this work, a flamelet modeling approach is used to simulate time-accurate, 3-D, combusting flow inside a single Gas Centered Swirl Coaxial (GCSC) injector using the flow solver, Loci-STREAM. CFD simulations were performed for several different injector geometries. Results of the CFD analysis helped guide the design of the injector from an initial concept to a tested prototype. The results of the CFD analysis are compared to data gathered from several hot-fire, single element injector tests performed in the Air Force Research Lab EC-1 test facility located at Edwards Air Force Base.

Analysis of Coupled Seals, Secondary and Powerstream Flow Fields in Aircraft and Aerospace Turbomachines

NASA Technical Reports Server (NTRS)

Athavale, M. M.; Ho, Y. H.; Prezekwas, A. J.

2005-01-01

Higher power, high efficiency gas turbine engines require optimization of the seals and secondary flow systems as well as their impact on the powerstream. This work focuses on two aspects: 1. To apply the present day CFD tools (SCISEAL) to different real-life secondary flow applications from different original equipment manufacturers (OEM s) to provide feedback data and 2. Develop a computational methodology for coupled time-accurate simulation of the powerstream and secondary flow with emphasis on the interaction between the disk-cavity and rim seals flows with the powerstream (SCISEAL-MS-TURBO). One OEM simulation was of the Allison Engine Company T-56 turbine drum cavities including conjugate heat transfer with good agreement with data and provided design feedback information. Another was the GE aspirating seal where the 3-D CFD simulations played a major role in analysis and modification of that seal configuration. The second major objective, development of a coupled flow simulation capability was achieved by using two codes MS-TURBO for the powerstream and SCISEAL for the secondary flows with an interface coupling algorithm. The coupled code was tested against data from three differed configurations: 1. bladeless-rotor-stator-cavity turbine test rig, 2. UTRC high pressure turbine test rig, and, 3. the NASA Low-Speed-Air Compressor rig (LSAC) with results and limitations discussed herein.

CFD - Mature Technology?

NASA Technical Reports Server (NTRS)

Kwak, Dochan

2005-01-01

Over the past 30 years, numerical methods and simulation tools for fluid dynamic problems have advanced as a new discipline, namely, computational fluid dynamics (CFD). Although a wide spectrum of flow regimes are encountered in many areas of science and engineering, simulation of compressible flow has been the major driver for developing computational algorithms and tools. This is probably due to a large demand for predicting the aerodynamic performance characteristics of flight vehicles, such as commercial, military, and space vehicles. As flow analysis is required to be more accurate and computationally efficient for both commercial and mission-oriented applications (such as those encountered in meteorology, aerospace vehicle development, general fluid engineering and biofluid analysis) CFD tools for engineering become increasingly important for predicting safety, performance and cost. This paper presents the author's perspective on the maturity of CFD, especially from an aerospace engineering point of view.

CFD Analysis in Advance of the NASA Juncture Flow Experiment

NASA Technical Reports Server (NTRS)

Lee, H. C.; Pulliam, T. H.; Neuhart, D. H.; Kegerise, M. A.

2017-01-01

NASA through its Transformational Tools and Technologies Project (TTT) under the Advanced Air Vehicle Program, is supporting a substantial effort to investigate the formation and origin of separation bubbles found on wing-body juncture zones. The flow behavior in these regions is highly complex, difficult to measure experimentally, and challenging to model numerically. Multiple wing configurations were designed and evaluated using Computational Fluid Dynamics (CFD), and a series of wind tunnel risk reduction tests were performed to further down-select the candidates for the final experiment. This paper documents the CFD analysis done in conjunction with the 6 percent scale risk reduction experiment performed in NASA Langley's 14- by 22-Foot Subsonic Tunnel. The combined CFD and wind tunnel results ultimately helped the Juncture Flow committee select the wing configurations for the final experiment.

CFD Analysis of the Aerodynamics of a Business-Jet Airfoil with Leading-Edge Ice Accretion

NASA Technical Reports Server (NTRS)

Chi, X.; Zhu, B.; Shih, T. I.-P.; Addy, H. E.; Choo, Y. K.

2004-01-01

For rime ice - where the ice buildup has only rough and jagged surfaces but no protruding horns - this study shows two dimensional CFD analysis based on the one-equation Spalart-Almaras (S-A) turbulence model to predict accurately the lift, drag, and pressure coefficients up to near the stall angle. For glaze ice - where the ice buildup has two or more protruding horns near the airfoil's leading edge - CFD predictions were much less satisfactory because of the large separated region produced by the horns even at zero angle of attack. This CFD study, based on the WIND and the Fluent codes, assesses the following turbulence models by comparing predictions with available experimental data: S-A, standard k-epsilon, shear-stress transport, v(exp 2)-f, and differential Reynolds stress.

Hemodynamic analysis of intracranial aneurysms using phase-contrast magnetic resonance imaging and computational fluid dynamics

NASA Astrophysics Data System (ADS)

Zhao, Xuemei; Li, Rui; Chen, Yu; Sia, Sheau Fung; Li, Donghai; Zhang, Yu; Liu, Aihua

2017-04-01

Additional hemodynamic parameters are highly desirable in the clinical management of intracranial aneurysm rupture as static medical images cannot demonstrate the blood flow within aneurysms. There are two ways of obtaining the hemodynamic information—by phase-contrast magnetic resonance imaging (PCMRI) and computational fluid dynamics (CFD). In this paper, we compared PCMRI and CFD in the analysis of a stable patient's specific aneurysm. The results showed that PCMRI and CFD are in good agreement with each other. An additional CFD study of two stable and two ruptured aneurysms revealed that ruptured aneurysms have a higher statistical average blood velocity, wall shear stress, and oscillatory shear index (OSI) within the aneurysm sac compared to those of stable aneurysms. Furthermore, for ruptured aneurysms, the OSI divides the positive and negative wall shear stress divergence at the aneurysm sac.

Analysis of Computational Fluid Dynamics and Particle Image Velocimetry Models of Distal-End Side-to-Side and End-to-Side Anastomoses for Coronary Artery Bypass Grafting in a Pulsatile Flow.

PubMed

Shintani, Yoshiko; Iino, Kenji; Yamamoto, Yoshitaka; Kato, Hiroki; Takemura, Hirofumi; Kiwata, Takahiro

2017-12-25

Intimal hyperplasia (IH) is a major cause of graft failure. Hemodynamic factors such as stagnation and disturbed blood flow are involved in IH formation. The aim of this study is to perform a comparative analysis of distal-end side-to-side (deSTS) and end-to-side (ETS) anastomoses using computational fluid dynamics (CFD) after validating the results via particle image velocimetry (PIV).Methods and Results:We investigated the characteristics of our target flow fields using CFD under steady and pulsatile flows. CFD via PIV under steady flow in a 10-times-actual-size model was validated. The CFD analysis revealed a recirculation zone in the heel region in the deSTS and ETS anastomoses and at the distal end of the graft, and just distal to the toe of the host artery in the deSTS anastomoses. The recirculation zone sizes changed with the phase shift. We found regions of low wall shear stress and high oscillating shear index in the same areas. The PIV and CFD results were similar. It was demonstrated that the hemodynamic characteristics of CFD and PIV is the difference between the deSTS and ETS anastomoses; that is, the deSTS flow peripheral to the distal end of the graft, at the distal end and just distal to the toe of the host artery is involved in the IH formation.

Rocket Ejector Studies for Application to RBCC Engines: An Integrated Experimental/CFD Approach

NASA Technical Reports Server (NTRS)

Pal, S.; Merkle, C. L.; Anderson, W. E.; Santoro, R. J.

1997-01-01

Recent interest in low cost, reliable access to space has generated increased interest in advanced technology approaches to space transportation systems. A key to the success of such programs lies in the development of advanced propulsion systems capable of achieving the performance and operations goals required for the next generation of space vehicles. One extremely promising approach involves the combination of rocket and air- breathing engines into a rocket-based combined-cycle engine (RBCC). A key element of that engine is the rocket ejector which is utilized in the zero to Mach two operating regime. Studies of RBCC engine concepts are not new and studies dating back thirty years are well documented in the literature. However, studies focused on the rocket ejector mode of the RBCC cycle are lacking. The present investigation utilizes an integrated experimental and computation fluid dynamics (CFD) approach to examine critical rocket ejector performance issues. In particular, the development of a predictive methodology capable of performance prediction is a key objective in order to analyze thermal choking and its control, primary/secondary pressure matching considerations, and effects of nozzle expansion ratio. To achieve this objective, the present study emphasizes obtaining new data using advanced optical diagnostics such as Raman spectroscopy and CFD techniques to investigate mixing in the rocket ejector mode. A new research facility for the study of the rocket ejector mode is described along with the diagnostic approaches to be used. The CFD modeling approach is also described along with preliminary CFD predictions obtained to date.

Simulating Effects of High Angle of Attack on Turbofan Engine Performance

NASA Technical Reports Server (NTRS)

Liu, Yuan; Claus, Russell W.; Litt, Jonathan S.; Guo, Ten-Huei

2013-01-01

A method of investigating the effects of high angle of attack (AOA) flight on turbofan engine performance is presented. The methodology involves combining a suite of diverse simulation tools. Three-dimensional, steady-state computational fluid dynamics (CFD) software is used to model the change in performance of a commercial aircraft-type inlet and fan geometry due to various levels of AOA. Parallel compressor theory is then applied to assimilate the CFD data with a zero-dimensional, nonlinear, dynamic turbofan engine model. The combined model shows that high AOA operation degrades fan performance and, thus, negatively impacts compressor stability margins and engine thrust. In addition, the engine response to high AOA conditions is shown to be highly dependent upon the type of control system employed.

Load Balancing Strategies for Multi-Block Overset Grid Applications

NASA Technical Reports Server (NTRS)

Djomehri, M. Jahed; Biswas, Rupak; Lopez-Benitez, Noe; Biegel, Bryan (Technical Monitor)

2002-01-01

The multi-block overset grid method is a powerful technique for high-fidelity computational fluid dynamics (CFD) simulations about complex aerospace configurations. The solution process uses a grid system that discretizes the problem domain by using separately generated but overlapping structured grids that periodically update and exchange boundary information through interpolation. For efficient high performance computations of large-scale realistic applications using this methodology, the individual grids must be properly partitioned among the parallel processors. Overall performance, therefore, largely depends on the quality of load balancing. In this paper, we present three different load balancing strategies far overset grids and analyze their effects on the parallel efficiency of a Navier-Stokes CFD application running on an SGI Origin2000 machine.

Fluid Structure Interaction in a Cold Flow Test and Transient CFD Analysis of Out-of-Round Nozzles

NASA Technical Reports Server (NTRS)

Ruf, Joseph; Brown, Andrew; McDaniels, David; Wang, Ten-See

2010-01-01

This viewgraph presentation describes two nozzle fluid flow interactions. They include: 1) Cold flow nozzle tests with fluid-structure interaction at nozzle separated flow; and 2) CFD analysis for nozzle flow and side loads of nozzle extensions with various out-of-round cases.

Pneumafil casing blower through moving reference frame (MRF) - A CFD simulation

NASA Astrophysics Data System (ADS)

Manivel, R.; Vijayanandh, R.; Babin, T.; Sriram, G.

2018-05-01

In this analysis work, the ring frame of Pneumafil casing blower of the textile mills with a power rating of 5 kW have been simulated using Computational Fluid Dynamics (CFD) code. The CFD analysis of the blower is carried out in Ansys Workbench 16.2 with Fluent using MRF solver settings. The simulation settings and boundary conditions are based on literature study and field data acquired. The main objective of this work is to reduce the energy consumption of the blower. The flow analysis indicated that the power consumption is influenced by the deflector plate orientation and deflector plate strip situated at the outlet casing of the blower. The energy losses occurred in the blower is due to the recirculation zones formed around the deflector plate strip. The deflector plate orientation is changed and optimized to reduce the energy consumption. The proposed optimized model is based on the simulation results which had relatively lesser power consumption than the existing and other cases. The energy losses in the Pneumafil casing blower are reduced through CFD analysis.

Scalable High-order Methods for Multi-Scale Problems: Analysis, Algorithms and Application

DTIC Science & Technology

2016-02-26

Karniadakis, “Resilient algorithms for reconstructing and simulating gappy flow fields in CFD ”, Fluid Dynamic Research, vol. 47, 051402, 2015. 2. Y. Yu, H...simulation, domain decomposition, CFD , gappy data, estimation theory, and gap-tooth algorithm. 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...objective of this project was to develop a general CFD framework for multifidelity simula- tions to target multiscale problems but also resilience in

Analysis of Low-Speed Stall Aerodynamics of a Swept Wing with Laminar-Flow Glove

NASA Technical Reports Server (NTRS)

Bui, Trong T.

2014-01-01

Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted to study the low-speed stall aerodynamics of a GIII aircraft's swept wing modified with a laminar-flow wing glove. The stall aerodynamics of the gloved wing were analyzed and compared with the unmodified wing for the flight speed of 120 knots and altitude of 2300 ft above mean sea level (MSL). The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First American Institute of Aeronautics and Astronautics (AIAA) CFD High-Lift Prediction Workshop. It was found that the Star-CCM+ CFD code can produce results that are within the scattering of other CFD codes considered at the workshop. In particular, the Star-CCM+ CFD code was able to predict wing stall for the AIAA wing-body geometry to within 1 degree of angle of attack as compared to benchmark wind-tunnel test data. Current results show that the addition of the laminar-flow wing glove causes the gloved wing to stall much earlier than the unmodified wing. Furthermore, the gloved wing has a different stall characteristic than the clean wing, with no sharp lift drop-off at stall for the gloved wing.

Analysis of Low Speed Stall Aerodynamics of a Swept Wing with Laminar Flow Glove

NASA Technical Reports Server (NTRS)

Bui, Trong T.

2014-01-01

Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted to study the low-speed stall aerodynamics of a GIII aircraft's swept wing modified with a laminar-flow wing glove. The stall aerodynamics of the gloved wing were analyzed and compared with the unmodified wing for the flight speed of 120 knots and altitude of 2300 ft above mean sea level (MSL). The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First American Institute of Aeronautics and Astronautics (AIAA) CFD High-Lift Prediction Workshop. It was found that the Star-CCM+ CFD code can produce results that are within the scattering of other CFD codes considered at the workshop. In particular, the Star-CCM+ CFD code was able to predict wing stall for the AIAA wing-body geometry to within 1 degree of angle of attack as compared to benchmark wind-tunnel test data. Current results show that the addition of the laminar-flow wing glove causes the gloved wing to stall much earlier than the unmodified wing. Furthermore, the gloved wing has a different stall characteristic than the clean wing, with no sharp lift drop-off at stall for the gloved wing.

Analytic corrections to CFD heating predictions accounting for changes in surface catalysis

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Inger, George R.

1996-01-01

Integral boundary-layer solution techniques applicable to the problem of determining aerodynamic heating rates of hypersonic vehicles in the vicinity of stagnation points and windward centerlines are briefly summarized. A new approach for combining the insight afforded by integral boundary-layer analysis with comprehensive (but time intensive) computational fluid dynamic (CFD) flowfield solutions of the thin-layer Navier-Stokes equations is described. The approach extracts CFD derived quantities at the wall and at the boundary layer edge for inclusion in a post-processing boundary-layer analysis. It allows a designer at a workstation to address two questions, given a single CFD solution. (1) How much does the heating change for a thermal protection system with different catalytic properties than was used in the original CFD solution? (2) How does the heating change at the interface of two different TPS materials with an abrupt change in catalytic efficiency? The answer to the second question is particularly important, because abrupt changes from low to high catalytic efficiency can lead to localized increase in heating which exceeds the usually conservative estimate provided by a fully catalytic wall assumption.

Visual Computing Environment Workshop

NASA Technical Reports Server (NTRS)

Lawrence, Charles (Compiler)

1998-01-01

The Visual Computing Environment (VCE) is a framework for intercomponent and multidisciplinary computational simulations. Many current engineering analysis codes simulate various aspects of aircraft engine operation. For example, existing computational fluid dynamics (CFD) codes can model the airflow through individual engine components such as the inlet, compressor, combustor, turbine, or nozzle. Currently, these codes are run in isolation, making intercomponent and complete system simulations very difficult to perform. In addition, management and utilization of these engineering codes for coupled component simulations is a complex, laborious task, requiring substantial experience and effort. To facilitate multicomponent aircraft engine analysis, the CFD Research Corporation (CFDRC) is developing the VCE system. This system, which is part of NASA's Numerical Propulsion Simulation System (NPSS) program, can couple various engineering disciplines, such as CFD, structural analysis, and thermal analysis.

Thin Film Heat Flux Sensors: Design and Methodology

NASA Technical Reports Server (NTRS)

Fralick, Gustave C.; Wrbanek, John D.

2013-01-01

Thin Film Heat Flux Sensors: Design and Methodology: (1) Heat flux is one of a number of parameters, together with pressure, temperature, flow, etc. of interest to engine designers and fluid dynamists, (2) The measurement of heat flux is of interest in directly determining the cooling requirements of hot section blades and vanes, and (3)In addition, if the surface and gas temperatures are known, the measurement of heat flux provides a value for the convective heat transfer coefficient that can be compared with the value provided by CFD codes.

Application of FUN3D and CFL3D to the Third Workshop on CFD Uncertainty Analysis

NASA Technical Reports Server (NTRS)

Rumsey, C. L.; Thomas, J. L.

2008-01-01

Two Reynolds-averaged Navier-Stokes computer codes - one unstructured and one structured - are applied to two workshop cases (for the 3rd Workshop on CFD Uncertainty Analysis, held at Instituto Superior Tecnico, Lisbon, in October 2008) for the purpose of uncertainty analysis. The Spalart-Allmaras turbulence model is employed. The first case uses the method of manufactured solution and is intended as a verification case. In other words, the CFD solution is expected to approach the exact solution as the grid is refined. The second case is a validation case (comparison against experiment), for which modeling errors inherent in the turbulence model and errors/uncertainty in the experiment may prevent close agreement. The results from the two computer codes are also compared. This exercise verifies that the codes are consistent both with the exact manufactured solution and with each other. In terms of order property, both codes behave as expected for the manufactured solution. For the backward facing step, CFD uncertainty on the finest grid is computed and is generally very low for both codes (whose results are nearly identical). Agreement with experiment is good at some locations for particular variables, but there are also many areas where the CFD and experimental uncertainties do not overlap.

Cold Flow Plume Entrainment Test Final Report NTF Test Number 2456

NASA Technical Reports Server (NTRS)

Ruf, Joseph H.; McDaniels, David; Mishtawy, Jason; Ramachandran, Narayanan; Hammad, Khaled J.

2005-01-01

As part of the Space Shuttle Return to Flight (RTF) program, Marshall Space Flight Center (MSFC) performed computational fluid dynamics (CFD) analysis to define the velocity flowfields around the Shuttle stack at liftoff. These CFD predicted velocity flowfields were used in debris transport analysis (DTA). High speed flows such as plumes induce or 'entrain' mass from the surrounding environment. Previous work had shown that CFD analysis over-predicts plume induced flows. Therefore, the DTA would tend to 1) predict more debris impacts, and 2) the debris velocity (and kinetic energy) of those impacts would be too high. At a November, 2004 peer-review it was recommended that the Liftoff DTA team quantify the uncertainty in the DTA caused by the CFD's over prediction of plume induced flow. To do so, the Liftoff DTA team needed benchmark quality data for plume induced flow to quantify the CFD accuracy and its effect on the DTA. MSFC's Nozzle Test Facility (NTF) conducted the "Nozzle Induced Flows test, P#2456" to obtain experimental data for plume induced flows for nozzle flow exhausting into q quiescent freestream. Planning for the test began in December, 2004 and the experimental data was obtained in February and March of 2005. The funding for this test was provided by MSFC's Space Shuttle Propulsion Systems Integration and Engineering office.

Dust control by air-blocking shelves and dust collector-to-bailing airflow ratios for a surface mine drill shroud

PubMed Central

Zheng, Y.; Reed, W.R.; Potts, J.D.; Li, M.; Rider, J.P.

2018-01-01

The National Institute for Occupational Safety and Health (NIOSH) recently developed a series of validated models utilizing computational fluid dynamics (CFD) to study the effects of air-blocking shelves on airflows and respirable dust distribution associated with medium-sized surface blasthole drill shrouds as part of a dry dust collector system. Using validated CFD models, three different air-blocking shelves were included in the present study: a 15.2-cm (6-in.)-wide shelf; a 7.6-cm (3-in.)-wide shelf; and a 7.6-cm (3-in.)-wide shelf at four different shelf heights. In addition, the dust-collector-to-bailing airflow ratios of 1.75:1, 1.5:1, 1.25:1 and 1:1 were evaluated for the 15.2-cm (6-in.)-wide air-blocking shelf. This paper describes the methodology used to develop the CFD models. The effects of air-blocking shelves and dust collector-to-bailing airflow ratios were identified by the study, and problem regions were revealed under certain conditions.

Generalized Reduced Order Modeling of Aeroservoelastic Systems

NASA Astrophysics Data System (ADS)

Gariffo, James Michael

Transonic aeroelastic and aeroservoelastic (ASE) modeling presents a significant technical and computational challenge. Flow fields with a mixture of subsonic and supersonic flow, as well as moving shock waves, can only be captured through high-fidelity CFD analysis. With modern computing power, it is realtively straightforward to determine the flutter boundary for a single structural configuration at a single flight condition, but problems of larger scope remain quite costly. Some such problems include characterizing a vehicle's flutter boundary over its full flight envelope, optimizing its structural weight subject to aeroelastic constraints, and designing control laws for flutter suppression. For all of these applications, reduced-order models (ROMs) offer substantial computational savings. ROM techniques in general have existed for decades, and the methodology presented in this dissertation builds on successful previous techniques to create a powerful new scheme for modeling aeroelastic systems, and predicting and interpolating their transonic flutter boundaries. In this method, linear ASE state-space models are constructed from modal structural and actuator models coupled to state-space models of the linearized aerodynamic forces through feedback loops. Flutter predictions can be made from these models through simple eigenvalue analysis of their state-transition matrices for an appropriate set of dynamic pressures. Moreover, this analysis returns the frequency and damping trend of every aeroelastic branch. In contrast, determining the critical dynamic pressure by direct time-marching CFD requires a separate run for every dynamic pressure being analyzed simply to obtain the trend for the critical branch. The present ROM methodology also includes a new model interpolation technique that greatly enhances the benefits of these ROMs. This enables predictions of the dynamic behavior of the system for flight conditions where CFD analysis has not been explicitly performed, thus making it possible to characterize the overall flutter boundary with far fewer CFD runs. A major challenge of this research is that transonic flutter boundaries can involve multiple unstable modes of different types. Multiple ROM-based studies on the ONERA M6 wing are shown indicating that in addition to classic bending-torsion (BT) flutter modes. which become unstable above a threshold dynamic pressure after two natural modes become aerodynamically coupled, some natural modes are able to extract energy from the air and become unstable by themselves. These single-mode instabilities tend to be weaker than the BT instabilities, but have near-zero flutter boundaries (exactly zero in the absence of structural damping). Examples of hump modes, which behave like natural mode instabilities before stabilizing, are also shown, as are cases where multiple instabilities coexist at a single flight condition. The result of all these instabilities is a highly sensitive flutter boundary, where small changes in Mach number, structural stiffness, and structural damping can substantially alter not only the stability of individual aeroelastic branches, but also which branch is critical. Several studies are shown presenting how the flutter boundary varies with respect to all three of these parameters, as well as the number of structural modes used to construct the ROMs. Finally, an investigation of the effectiveness and limitations of the interpolation scheme is presented. It is found that in regions where the flutter boundary is relatively smooth, the interpolation method produces ROMs that predict the flutter characteristics of the corresponding directly computed models to a high degree of accuracy, even for relatively coarsely spaced data. On the other hand, in the transonic dip region, the interpolated ROMs show significant errors at points where the boundary changes rapidly; however, they still give a good qualitative estimate of where the largest jumps occur.

Interfacing comprehensive rotorcraft analysis with advanced aeromechanics and vortex wake models

NASA Astrophysics Data System (ADS)

Liu, Haiying

This dissertation describes three aspects of the comprehensive rotorcraft analysis. First, a physics-based methodology for the modeling of hydraulic devices within multibody-based comprehensive models of rotorcraft systems is developed. This newly proposed approach can predict the fully nonlinear behavior of hydraulic devices, and pressure levels in the hydraulic chambers are coupled with the dynamic response of the system. The proposed hydraulic device models are implemented in a multibody code and calibrated by comparing their predictions with test bench measurements for the UH-60 helicopter lead-lag damper. Predicted peak damping forces were found to be in good agreement with measurements, while the model did not predict the entire time history of damper force to the same level of accuracy. The proposed model evaluates relevant hydraulic quantities such as chamber pressures, orifice flow rates, and pressure relief valve displacements. This model could be used to design lead-lag dampers with desirable force and damping characteristics. The second part of this research is in the area of computational aeroelasticity, in which an interface between computational fluid dynamics (CFD) and computational structural dynamics (CSD) is established. This interface enables data exchange between CFD and CSD with the goal of achieving accurate airloads predictions. In this work, a loose coupling approach based on the delta-airloads method is developed in a finite-element method based multibody dynamics formulation, DYMORE. To validate this aerodynamic interface, a CFD code, OVERFLOW-2, is loosely coupled with a CSD program, DYMORE, to compute the airloads of different flight conditions for Sikorsky UH-60 aircraft. This loose coupling approach has good convergence characteristics. The predicted airloads are found to be in good agreement with the experimental data, although not for all flight conditions. In addition, the tight coupling interface between the CFD program, OVERFLOW-2, and the CSD program, DYMORE, is also established. The ability to accurately capture the wake structure around a helicopter rotor is crucial for rotorcraft performance analysis. In the third part of this thesis, a new representation of the wake vortex structure based on Non-Uniform Rational B-Spline (NURBS) curves and surfaces is proposed to develop an efficient model for prescribed and free wakes. NURBS curves and surfaces are able to represent complex shapes with remarkably little data. The proposed formulation has the potential to reduce the computational cost associated with the use of Helmholtz's law and the Biot-Savart law when calculating the induced flow field around the rotor. An efficient free-wake analysis will considerably decrease the computational cost of comprehensive rotorcraft analysis, making the approach more attractive to routine use in industrial settings.

Design and Analysis of Turbines for Space Applications

NASA Technical Reports Server (NTRS)

Griffin, Lisa W.; Dorney, Daniel J.; Huber, Frank W.

2003-01-01

In order to mitigate the risk of rocket propulsion development, efficient, accurate, detailed fluid dynamics analysis of the turbomachinery is necessary. This analysis is used for component development, design parametrics, performance prediction, and environment definition. To support this requirement, a task was developed at NASAh4arshall Space Flight Center (MSFC) to improve turbine aerodynamic performance through the application of advanced design and analysis tools. There are four major objectives of this task: 1) to develop, enhance, and integrate advanced turbine aerodynamic design and analysis tools; 2) to develop the methodology for application of the analytical techniques; 3) to demonstrate the benefits of the advanced turbine design procedure through its application to a relevant turbine design point; and 4) to verify the optimized design and analysis with testing. The turbine chosen on which to demonstrate the procedure was a supersonic design suitable for a reusable launch vehicle (RLV). The hot gas path and blading were redesigned to obtain an increased efficiency. The redesign of the turbine was conducted with a consideration of system requirements, realizing that a highly efficient turbine that, for example, significantly increases engine weight, is of limited benefit. Both preliminary and detailed designs were considered. To generate an improved design, one-dimensional (1D) design and analysis tools, computational fluid dynamics (CFD), response surface methodology (RSM), and neural nets (NN) were used.

Computational fluid dynamic modeling of a medium-sized surface mine blasthole drill shroud

PubMed Central

Zheng, Y.; Reed, W.R.; Zhou, L.; Rider, J.P.

2016-01-01

The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) recently developed a series of models using computational fluid dynamics (CFD) to study airflows and respirable dust distribution associated with a medium-sized surface blasthole drill shroud with a dry dust collector system. Previously run experiments conducted in NIOSH’s full-scale drill shroud laboratory were used to validate the models. The setup values in the CFD models were calculated from experimental data obtained from the drill shroud laboratory and measurements of test material particle size. Subsequent simulation results were compared with the experimental data for several test scenarios, including 0.14 m3/s (300 cfm) and 0.24 m3/s (500 cfm) bailing airflow with 2:1, 3:1 and 4:1 dust collector-to-bailing airflow ratios. For the 2:1 and 3:1 ratios, the calculated dust concentrations from the CFD models were within the 95 percent confidence intervals of the experimental data. This paper describes the methodology used to develop the CFD models, to calculate the model input and to validate the models based on the experimental data. Problem regions were identified and revealed by the study. The simulation results could be used for future development of dust control methods for a surface mine blasthole drill shroud. PMID:27932851

High Maneuverability Airframe: Investigation of Fin and Canard Sizing for Optimum Maneuverability

DTIC Science & Technology

2014-09-01

overset grids (unified- grid); 5) total variation diminishing discretization based on a new multidimensional interpolation framework; 6) Riemann solvers to...Aerodynamics .........................................................................................3 3.1.1 Solver ...describes the methodology used for the simulations. 3.1.1 Solver The double-precision solver of a commercially available code, CFD ++ v12.1.1, 9

A Method for Generating Reduced Order Linear Models of Supersonic Inlets

NASA Technical Reports Server (NTRS)

Chicatelli, Amy; Hartley, Tom T.

1997-01-01

For the modeling of high speed propulsion systems, there are at least two major categories of models. One is based on computational fluid dynamics (CFD), and the other is based on design and analysis of control systems. CFD is accurate and gives a complete view of the internal flow field, but it typically has many states and runs much slower dm real-time. Models based on control design typically run near real-time but do not always capture the fundamental dynamics. To provide improved control models, methods are needed that are based on CFD techniques but yield models that are small enough for control analysis and design.

Development of code evaluation criteria for assessing predictive capability and performance

NASA Technical Reports Server (NTRS)

Lin, Shyi-Jang; Barson, S. L.; Sindir, M. M.; Prueger, G. H.

1993-01-01

Computational Fluid Dynamics (CFD), because of its unique ability to predict complex three-dimensional flows, is being applied with increasing frequency in the aerospace industry. Currently, no consistent code validation procedure is applied within the industry. Such a procedure is needed to increase confidence in CFD and reduce risk in the use of these codes as a design and analysis tool. This final contract report defines classifications for three levels of code validation, directly relating the use of CFD codes to the engineering design cycle. Evaluation criteria by which codes are measured and classified are recommended and discussed. Criteria for selecting experimental data against which CFD results can be compared are outlined. A four phase CFD code validation procedure is described in detail. Finally, the code validation procedure is demonstrated through application of the REACT CFD code to a series of cases culminating in a code to data comparison on the Space Shuttle Main Engine High Pressure Fuel Turbopump Impeller.

The construction FACE database - Codifying the NIOSH FACE reports.

PubMed

Dong, Xiuwen Sue; Largay, Julie A; Wang, Xuanwen; Cain, Chris Trahan; Romano, Nancy

2017-09-01

The National Institute for Occupational Safety and Health (NIOSH) has published reports detailing the results of investigations on selected work-related fatalities through the Fatality Assessment and Control Evaluation (FACE) program since 1982. Information from construction-related FACE reports was coded into the Construction FACE Database (CFD). Use of the CFD was illustrated by analyzing major CFD variables. A total of 768 construction fatalities were included in the CFD. Information on decedents, safety training, use of PPE, and FACE recommendations were coded. Analysis shows that one in five decedents in the CFD died within the first two months on the job; 75% and 43% of reports recommended having safety training or installing protection equipment, respectively. Comprehensive research using FACE reports may improve understanding of work-related fatalities and provide much-needed information on injury prevention. The CFD allows researchers to analyze the FACE reports quantitatively and efficiently. Copyright © 2017 Elsevier Ltd and National Safety Council. All rights reserved.

Analysis of Flame Deflector Spray Nozzles in Rocket Engine Test Stands

NASA Technical Reports Server (NTRS)

Sachdev, Jai S.; Ahuja, Vineet; Hosangadi, Ashvin; Allgood, Daniel C.

2010-01-01

The development of a unified tightly coupled multi-phase computational framework is described for the analysis and design of cooling spray nozzle configurations on the flame deflector in rocket engine test stands. An Eulerian formulation is used to model the disperse phase and is coupled to the gas-phase equations through momentum and heat transfer as well as phase change. The phase change formulation is modeled according to a modified form of the Hertz-Knudsen equation. Various simple test cases are presented to verify the validity of the numerical framework. The ability of the methodology to accurately predict the temperature load on the flame deflector is demonstrated though application to an actual sub-scale test facility. The CFD simulation was able to reproduce the result of the test-firing, showing that the spray nozzle configuration provided insufficient amount of cooling.

Analysis of Nozzle Jet Plume Effects on Sonic Boom Signature

NASA Technical Reports Server (NTRS)

Bui, Trong

2010-01-01

An axisymmetric full Navier-Stokes computational fluid dynamics (CFD) study was conducted to examine nozzle exhaust jet plume effects on the sonic boom signature of a supersonic aircraft. A simplified axisymmetric nozzle geometry, representative of the nozzle on the NASA Dryden NF-15B Lift and Nozzle Change Effects on Tail Shock (LaNCETS) research airplane, was considered. The highly underexpanded nozzle flow is found to provide significantly more reduction in the tail shock strength in the sonic boom N-wave pressure signature than perfectly expanded and overexpanded nozzle flows. A tail shock train in the sonic boom signature, similar to what was observed in the LaNCETS flight data, is observed for the highly underexpanded nozzle flow. The CFD results provide a detailed description of the nozzle flow physics involved in the LaNCETS nozzle at different nozzle expansion conditions and help in interpreting LaNCETS flight data as well as in the eventual CFD analysis of a full LaNCETS aircraft. The current study also provided important information on proper modeling of the LaNCETS aircraft nozzle. The primary objective of the current CFD research effort was to support the LaNCETS flight research data analysis effort by studying the detailed nozzle exhaust jet plume s imperfect expansion effects on the sonic boom signature of a supersonic aircraft. Figure 1 illustrates the primary flow physics present in the interaction between the exhaust jet plume shock and the sonic boom coming off of an axisymmetric body in supersonic flight. The steeper tail shock from highly expanded jet plume reduces the dip of the sonic boom N-wave signature. A structured finite-volume compressible full Navier-Stokes CFD code was used in the current study. This approach is not limited by the simplifying assumptions inherent in previous sonic boom analysis efforts. Also, this study was the first known jet plume sonic boom CFD study in which the full viscous nozzle flow field was modeled, without coupling to a sonic boom propagation analysis code, from the stagnation chamber of the nozzle to the far field external flow, taking into account all nonisentropic effects in the shocks, boundary layers, and free shear layers, and their interactions at distances up to 30 times the nozzle exit diameter from the jet centerline. A CFD solution is shown in Figure 2. The flow field is very complicated and multi-dimensional, with shock-shock and shockplume interactions. At the time of this reporting, a full three-dimensional CFD study was being conducted to evaluate the effects of nozzle vectoring on the aircraft tail shock strength.

Measurements and Predictions for a Distributed Exhaust Nozzle

NASA Technical Reports Server (NTRS)

Kinzie, Kevin W.; Brown, Martha C.; Schein, David B.; Solomon, W. David, Jr.

2001-01-01

The acoustic and aerodynamic performance characteristics of a distributed exhaust nozzle (DEN) design concept were evaluated experimentally and analytically with the purpose of developing a design methodology for developing future DEN technology. Aerodynamic and acoustic measurements were made to evaluate the DEN performance and the CFD design tool. While the CFD approach did provide an excellent prediction of the flowfield and aerodynamic performance characteristics of the DEN and 2D reference nozzle, the measured acoustic suppression potential of this particular DEN was low. The measurements and predictions indicated that the mini-exhaust jets comprising the distributed exhaust coalesced back into a single stream jet very shortly after leaving the nozzles. Even so, the database provided here will be useful for future distributed exhaust designs with greater noise reduction and aerodynamic performance potential.

Automated Boundary Conditions for Wind Tunnel Simulations

NASA Technical Reports Server (NTRS)

Carlson, Jan-Renee

2018-01-01

Computational fluid dynamic (CFD) simulations of models tested in wind tunnels require a high level of fidelity and accuracy particularly for the purposes of CFD validation efforts. Considerable effort is required to ensure the proper characterization of both the physical geometry of the wind tunnel and recreating the correct flow conditions inside the wind tunnel. The typical trial-and-error effort used for determining the boundary condition values for a particular tunnel configuration are time and computer resource intensive. This paper describes a method for calculating and updating the back pressure boundary condition in wind tunnel simulations by using a proportional-integral-derivative controller. The controller methodology and equations are discussed, and simulations using the controller to set a tunnel Mach number in the NASA Langley 14- by 22-Foot Subsonic Tunnel are demonstrated.

Modeling of milk flow in mammary ducts in lactating human female breast.

PubMed

Mortazavi, S Negin; Geddes, Donna; Hassanipour, Fatemeh

2014-01-01

A transient laminar Newtonian three-dimensional CFD simulation has been studied for milk flow in a phantom model of the 6-generations human lactating breast branching system. Milk is extracted by the cyclic pattern of suction from the alveoli through the duct and to the nipple. The real negative (suction) pressure data are applied as an outlet boundary condition in nipple. In this study, the commercial CFD code (Fluent Inc., 2004) is employed for the numerical solution of the milk flow. The milk intake flow rate from simulation is compared to the real clinical data from published paper. The results are in good agreement. It is believed that the methodology of the lactating human breast branching modeling proposed here can provide potential guidelines for further clinical and research application.

CFD analysis of a full-scale ceramic kiln module under actual operating conditions

NASA Astrophysics Data System (ADS)

Milani, Massimo; Montorsi, Luca; Stefani, Matteo; Venturelli, Matteo

2017-11-01

The paper focuses on the CFD analysis of a full-scale module of an industrial ceramic kiln under actual operating conditions. The multi-dimensional analysis includes the real geometry of a ceramic kiln module employed in the preheating and firing sections and investigates the heat transfer between the tiles and the burners' flame as well as the many components that comprise the module. Particular attention is devoted to the simulation of the convective flow field in the upper and lower chambers and to the effects of radiation on the different materials is addressed. The assessment of the radiation contribution to the tiles temperature is paramount to the improvement of the performance of the kiln in terms of energy efficiency and fuel consumption. The CFD analysis is combined to a lumped and distributed parameter model of the entire kiln in order to simulate the module behaviour at the boundaries under actual operating conditions. Finally, the CFD simulation is employed to address the effects of the module operating conditions on the tiles' temperature distribution in order to improve the temperature uniformity as well as to enhance the energy efficiency of the system and thus to reduce the fuel consumption.

Force Balance Determination of a Film Riding Seal Using CFD

NASA Technical Reports Server (NTRS)

Justak, John

2007-01-01

CFD analysis provides a means of discerning H-seal functionality. H-Seal geometry can be modified to provide smaller or larger operational gap. H-Seal can be installed with large cold clearance and maintain a small operational effective clearance.

Reduction and Analysis of Phosphor Thermography Data With the IHEAT Software Package

NASA Technical Reports Server (NTRS)

Merski, N. Ronald

1998-01-01

Detailed aeroheating information is critical to the successful design of a thermal protection system (TPS) for an aerospace vehicle. This report describes NASA Langley Research Center's (LaRC) two-color relative-intensity phosphor thermography method and the IHEAT software package which is used for the efficient data reduction and analysis of the phosphor image data. Development of theory is provided for a new weighted two-color relative-intensity fluorescence theory for quantitatively determining surface temperatures on hypersonic wind tunnel models; an improved application of the one-dimensional conduction theory for use in determining global heating mappings; and extrapolation of wind tunnel data to flight surface temperatures. The phosphor methodology at LaRC is presented including descriptions of phosphor model fabrication, test facilities and phosphor video acquisition systems. A discussion of the calibration procedures, data reduction and data analysis is given. Estimates of the total uncertainties (with a 95% confidence level) associated with the phosphor technique are shown to be approximately 8 to 10 percent in the Langley's 31-Inch Mach 10 Tunnel and 7 to 10 percent in the 20-Inch Mach 6 Tunnel. A comparison with thin-film measurements using two-inch radius hemispheres shows the phosphor data to be within 7 percent of thin-film measurements and to agree even better with predictions via a LATCH computational fluid dynamics solution (CFD). Good agreement between phosphor data and LAURA CFD computations on the forebody of a vertical takeoff/vertical lander configuration at four angles of attack is also shown. In addition, a comparison is given between Mach 6 phosphor data and laminar and turbulent solutions generated using the LAURA, GASP and LATCH CFD codes. Finally, the extrapolation method developed in this report is applied to the X-34 configuration with good agreement between the phosphor extrapolation and LAURA flight surface temperature predictions. The phosphor process outlined in the paper is believed to provide the aerothermodynamic community with a valuable capability for rapidly obtaining (4 to 5 weeks) detailed heating information needed in TPS design.

Collaborative simulations and experiments for a novel yield model of coal devolatilization in oxy-coal combustion conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iavarone, Salvatore; Smith, Sean T.; Smith, Philip J.

Oxy-coal combustion is an emerging low-cost “clean coal” technology for emissions reduction and Carbon Capture and Sequestration (CCS). The use of Computational Fluid Dynamics (CFD) tools is crucial for the development of cost-effective oxy-fuel technologies and the minimization of environmental concerns at industrial scale. The coupling of detailed chemistry models and CFD simulations is still challenging, especially for large-scale plants, because of the high computational efforts required. The development of scale-bridging models is therefore necessary, to find a good compromise between computational efforts and the physical-chemical modeling precision. This paper presents a procedure for scale-bridging modeling of coal devolatilization, inmore » the presence of experimental error, that puts emphasis on the thermodynamic aspect of devolatilization, namely the final volatile yield of coal, rather than kinetics. The procedure consists of an engineering approach based on dataset consistency and Bayesian methodology including Gaussian-Process Regression (GPR). Experimental data from devolatilization tests carried out in an oxy-coal entrained flow reactor were considered and CFD simulations of the reactor were performed. Jointly evaluating experiments and simulations, a novel yield model was validated against the data via consistency analysis. In parallel, a Gaussian-Process Regression was performed, to improve the understanding of the uncertainty associated to the devolatilization, based on the experimental measurements. Potential model forms that could predict yield during devolatilization were obtained. The set of model forms obtained via GPR includes the yield model that was proven to be consistent with the data. Finally, the overall procedure has resulted in a novel yield model for coal devolatilization and in a valuable evaluation of uncertainty in the data, in the model form, and in the model parameters.« less

Collaborative simulations and experiments for a novel yield model of coal devolatilization in oxy-coal combustion conditions

DOE PAGES

Iavarone, Salvatore; Smith, Sean T.; Smith, Philip J.; ...

2017-06-03

Oxy-coal combustion is an emerging low-cost “clean coal” technology for emissions reduction and Carbon Capture and Sequestration (CCS). The use of Computational Fluid Dynamics (CFD) tools is crucial for the development of cost-effective oxy-fuel technologies and the minimization of environmental concerns at industrial scale. The coupling of detailed chemistry models and CFD simulations is still challenging, especially for large-scale plants, because of the high computational efforts required. The development of scale-bridging models is therefore necessary, to find a good compromise between computational efforts and the physical-chemical modeling precision. This paper presents a procedure for scale-bridging modeling of coal devolatilization, inmore » the presence of experimental error, that puts emphasis on the thermodynamic aspect of devolatilization, namely the final volatile yield of coal, rather than kinetics. The procedure consists of an engineering approach based on dataset consistency and Bayesian methodology including Gaussian-Process Regression (GPR). Experimental data from devolatilization tests carried out in an oxy-coal entrained flow reactor were considered and CFD simulations of the reactor were performed. Jointly evaluating experiments and simulations, a novel yield model was validated against the data via consistency analysis. In parallel, a Gaussian-Process Regression was performed, to improve the understanding of the uncertainty associated to the devolatilization, based on the experimental measurements. Potential model forms that could predict yield during devolatilization were obtained. The set of model forms obtained via GPR includes the yield model that was proven to be consistent with the data. Finally, the overall procedure has resulted in a novel yield model for coal devolatilization and in a valuable evaluation of uncertainty in the data, in the model form, and in the model parameters.« less

Comparison of Experimental Data and Computations Fluid Dynamics Analysis for a Three Dimensional Linear Plug Nozzle

NASA Technical Reports Server (NTRS)

Ruf, J. H.; Hagemann, G.; Immich, H.

2003-01-01

A three dimensional linear plug nozzle of area ratio 12.79 was designed by EADS Space Transportation (former Astrium Space Infrastructure). The nozzle was tested within the German National Technology Program 'LION' in a cold air wind tunnel by TU Dresden. The experimental hardware and test conditions are described. Experimental data was obtained for the nozzle without plug side wall fences at a nozzle pressure ratio of 116 and then with plug side wall fences at NPR 110. Schlieren images were recorded and axial profiles of plug wall static pressures were measured at several spanwise locations and on the plug base. Detailed CFD analysis was performed for these nozzle configurations at NPR 116 by NASA MSFC. The CFD exhibits good agreement with the experimental data. A detailed comparison of the CFD results and the experimental plug wall pressure data are given. Comparisons are made for both the without and with plug side wall fence configurations. Numerical results for density gradient are compared to experimental Schlieren images. Experimental nozzle thrust efficiencies are calculated based on the CFD results. The CFD results are used to illustrate the plug nozzle fluid dynamics. The effect of the plug side wall is emphasized.

Optimization of a Centrifugal Impeller Design Through CFD Analysis

NASA Technical Reports Server (NTRS)

Chen, W. C.; Eastland, A. H.; Chan, D. C.; Garcia, Roberto

1993-01-01

This paper discusses the procedure, approach and Rocketdyne CFD results for the optimization of the NASA consortium impeller design. Two different approaches have been investigated. The first one is to use a tandem blade arrangement, the main impeller blade is split into two separate rows with the second blade row offset circumferentially with respect to the first row. The second approach is to control the high losses related to secondary flows within the impeller passage. Many key parameters have been identified and each consortium team member involved will optimize a specific parameter using 3-D CFD analysis. Rocketdyne has provided a series of CFD grids for the consortium team members. SECA will complete the tandem blade study, SRA will study the effect of the splitter blade solidity change, NASA LeRC will evaluate the effect of circumferential position of the splitter blade, VPI will work on the hub to shroud blade loading distribution, NASA Ames will examine the impeller discharge leakage flow impacts and Rocketdyne will continue to work on the meridional contour and the blade leading to trailing edge work distribution. This paper will also present Rocketdyne results from the tandem blade study and from the blade loading distribution study. It is the ultimate goal of this consortium team to integrate the available CFD analysis to design an advanced technology impeller that is suitable for use in the NASA Space Transportation Main Engine (STME) fuel turbopump.

Probabilistic safety analysis for urgent situations following the accidental release of a pollutant in the atmosphere

NASA Astrophysics Data System (ADS)

Armand, P.; Brocheton, F.; Poulet, D.; Vendel, F.; Dubourg, V.; Yalamas, T.

2014-10-01

This paper is an original contribution to uncertainty quantification in atmospheric transport & dispersion (AT&D) at the local scale (1-10 km). It is proposed to account for the imprecise knowledge of the meteorological and release conditions in the case of an accidental hazardous atmospheric emission. The aim is to produce probabilistic risk maps instead of a deterministic toxic load map in order to help the stakeholders making their decisions. Due to the urge attached to such situations, the proposed methodology is able to produce such maps in a limited amount of time. It resorts to a Lagrangian particle dispersion model (LPDM) using wind fields interpolated from a pre-established database that collects the results from a computational fluid dynamics (CFD) model. This enables a decoupling of the CFD simulations from the dispersion analysis, thus a considerable saving of computational time. In order to make the Monte-Carlo-sampling-based estimation of the probability field even faster, it is also proposed to recourse to the use of a vector Gaussian process surrogate model together with high performance computing (HPC) resources. The Gaussian process (GP) surrogate modelling technique is coupled with a probabilistic principal component analysis (PCA) for reducing the number of GP predictors to fit, store and predict. The design of experiments (DOE) from which the surrogate model is built, is run over a cluster of PCs for making the total production time as short as possible. The use of GP predictors is validated by comparing the results produced by this technique with those obtained by crude Monte Carlo sampling.

NASA and CFD - Making investments for the future

NASA Technical Reports Server (NTRS)

Hessenius, Kristin A.; Richardson, P. F.

1992-01-01

From a NASA perspective, CFD is a new tool for fluid flow simulation and prediction with virtually none of the inherent limitations of other ground-based simulation techniques. A primary goal of NASA's CFD research program is to develop efficient and accurate computational techniques for utilization in the design and analysis of aerospace vehicles. The program in algorithm development has systematically progressed through the hierarchy of engineering simplifications of the Navier-Stokes equations, starting with the inviscid formulations such as transonic small disturbance, full potential, and Euler.

Integrated Design Engineering Analysis (IDEA) Environment Automated Generation of Structured CFD Grids using Topology Methods

NASA Technical Reports Server (NTRS)

Kamhawi, Hilmi N.

2012-01-01

This report documents the work performed from March 2010 to March 2012. The Integrated Design and Engineering Analysis (IDEA) environment is a collaborative environment based on an object-oriented, multidisciplinary, distributed framework using the Adaptive Modeling Language (AML) as a framework and supporting the configuration design and parametric CFD grid generation. This report will focus on describing the work in the area of parametric CFD grid generation using novel concepts for defining the interaction between the mesh topology and the geometry in such a way as to separate the mesh topology from the geometric topology while maintaining the link between the mesh topology and the actual geometry.

Improvement of Flow Quality in NAL Chofu Mach 10 Nozzle

NASA Technical Reports Server (NTRS)

Lacey, John; Inoue, Yasutoshi; Higashida, Akio; Inoue, Manabu; Ishizaka, Kouichi; Korte, John J.

2002-01-01

As a result of CFD analysis and remachining of the nozzle, the flow quality of the Mach 10 Hypersonic Wind Tunnel at NAL Chofu, Japan was improved. The subsequent test results validated the CFD analytical predictions by NASA and MHL.

A FRAMEWORK FOR FINE-SCALE COMPUTATIONAL FLUID DYNAMICS AIR QUALITY MODELING AND ANALYSIS

EPA Science Inventory

Fine-scale Computational Fluid Dynamics (CFD) simulation of pollutant concentrations within roadway and building microenvironments is feasible using high performance computing. Unlike currently used regulatory air quality models, fine-scale CFD simulations are able to account rig...

CFD simulation of airflow inside tree canopies discharged from air-assisted sprayers

USDA-ARS?s Scientific Manuscript database

Effective pesticide application is not only essential for specialty crop industries but also very important for addressing increasing concerns about environmental contamination caused by pesticide spray drift. Numerical analysis using computational fluid dynamics (CFD) can contribute to better under...

Multi-physics CFD simulations in engineering

NASA Astrophysics Data System (ADS)

Yamamoto, Makoto

2013-08-01

Nowadays Computational Fluid Dynamics (CFD) software is adopted as a design and analysis tool in a great number of engineering fields. We can say that single-physics CFD has been sufficiently matured in the practical point of view. The main target of existing CFD software is single-phase flows such as water and air. However, many multi-physics problems exist in engineering. Most of them consist of flow and other physics, and the interactions between different physics are very important. Obviously, multi-physics phenomena are critical in developing machines and processes. A multi-physics phenomenon seems to be very complex, and it is so difficult to be predicted by adding other physics to flow phenomenon. Therefore, multi-physics CFD techniques are still under research and development. This would be caused from the facts that processing speed of current computers is not fast enough for conducting a multi-physics simulation, and furthermore physical models except for flow physics have not been suitably established. Therefore, in near future, we have to develop various physical models and efficient CFD techniques, in order to success multi-physics simulations in engineering. In the present paper, I will describe the present states of multi-physics CFD simulations, and then show some numerical results such as ice accretion and electro-chemical machining process of a three-dimensional compressor blade which were obtained in my laboratory. Multi-physics CFD simulations would be a key technology in near future.

Development of Switchable Polarity Solvent Draw Solutes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Aaron D.

Results of a computational fluid dynamic (CFD) study of flow and heat transfer in a printed circuit heat exchanger (PCHE) geometry are presented. CFD results obtained from a two-plate model are compared to corresponding experimental results for the validation. This process provides the basis for further application of the CFD code to PCHE design and performance analysis in a variety of internal flow geometries. As a part of the code verification and validation (V&V) process, CFD simulation of a single semicircular straight channel under laminar isothermal conditions was also performed and compared to theoretical results. This comparison yielded excellent agreementmore » with the theoretical values. The two-plate CFD model based on the experimental PCHE design overestimated the effectiveness and underestimated the pressure drop. However, it is found that the discrepancy between the CFD result and experimental data was mainly caused by the uncertainty in the geometry of heat exchanger during the fabrication. The CFD results obtained using a slightly smaller channel diameter yielded good agreement with the experimental data. A separate investigation revealed that the average channel diameter of the OSU PCHE after the diffusion-bonding was 1.93 mm on the cold fluid side and 1.90 mm on the hot fluid side which are both smaller than the nominal design value. Consequently, the CFD code was shown to have sufficient capability to evaluate the heat exchanger thermal-hydraulic performance.« less

An engineering closure for heavily under-resolved coarse-grid CFD in large applications

NASA Astrophysics Data System (ADS)

Class, Andreas G.; Yu, Fujiang; Jordan, Thomas

2016-11-01

Even though high performance computation allows very detailed description of a wide range of scales in scientific computations, engineering simulations used for design studies commonly merely resolve the large scales thus speeding up simulation time. The coarse-grid CFD (CGCFD) methodology is developed for flows with repeated flow patterns as often observed in heat exchangers or porous structures. It is proposed to use inviscid Euler equations on a very coarse numerical mesh. This coarse mesh needs not to conform to the geometry in all details. To reinstall physics on all smaller scales cheap subgrid models are employed. Subgrid models are systematically constructed by analyzing well-resolved generic representative simulations. By varying the flow conditions in these simulations correlations are obtained. These comprehend for each individual coarse mesh cell a volume force vector and volume porosity. Moreover, for all vertices, surface porosities are derived. CGCFD is related to the immersed boundary method as both exploit volume forces and non-body conformal meshes. Yet, CGCFD differs with respect to the coarser mesh and the use of Euler equations. We will describe the methodology based on a simple test case and the application of the method to a 127 pin wire-wrap fuel bundle.

Application of transient CFD-procedures for S-shape computation in pump-turbines with and without FSI

NASA Astrophysics Data System (ADS)

Casartelli, E.; Mangani, L.; Ryan, O.; Schmid, A.

2016-11-01

CFD has entered the product development process in hydraulic machines since more than three decades. Beside the actual design process, in which the most appropriate geometry for a certain task is iteratively sought, several steady-state simulations and related analyses are performed with the help of CFD. Basic transient CFD-analysis is becoming more and more routine for rotor-stator interaction assessment, but in general unsteady CFD is still not standard due to the large computational effort. Especially for FSI simulations, where mesh motion is involved, a considerable amount of computational time is necessary for the mesh handling and deformation as well as the related unsteady flow field resolution. Therefore this kind of CFD computations are still unusual and mostly performed during trouble-shooting analysis rather than in the standard development process, i.e. in order to understand what went wrong instead of preventing failure or even better to increase the available knowledge. In this paper the application of an efficient and particularly robust algorithm for fast computations with moving mesh is presented for the analysis of transient effects encountered during highly dynamic procedures in the operation of a pump-turbine, like runaway at fixed GV position and load-rejection with GV motion imposed as one-way FSI. In both cases the computations extend through the S-shape of the machine in the turbine-brake and reverse pump domain, showing that such exotic computations can be perform on a more regular base, even if quite time consuming. Beside the presentation of the procedure and global results, some highlights in the encountered flow-physics are also given.

Nonlinear Dynamic Modeling of a Supersonic Commercial Transport Turbo-Machinery Propulsion System for Aero-Propulso-Servo-Elasticity Research

NASA Technical Reports Server (NTRS)

Connolly, Joseph W.; Kopasakis, George; Carlson, Jan-Renee; Woolwine, Kyle

2015-01-01

This paper covers the development of an integrated nonlinear dynamic model for a variable cycle turbofan engine, supersonic inlet, and convergent-divergent nozzle that can be integrated with an aeroelastic vehicle model to create an overall Aero-Propulso-Servo-Elastic (APSE) modeling tool. The primary focus of this study is to provide a means to capture relevant thrust dynamics of a full supersonic propulsion system by using relatively simple quasi-one dimensional computational fluid dynamics (CFD) methods that will allow for accurate control algorithm development and capture the key aspects of the thrust to feed into an APSE model. Previously, propulsion system component models have been developed and are used for this study of the fully integrated propulsion system. An overview of the methodology is presented for the modeling of each propulsion component, with a focus on its associated coupling for the overall model. To conduct APSE studies the de- scribed dynamic propulsion system model is integrated into a high fidelity CFD model of the full vehicle capable of conducting aero-elastic studies. Dynamic thrust analysis for the quasi-one dimensional dynamic propulsion system model is presented along with an initial three dimensional flow field model of the engine integrated into a supersonic commercial transport.

Characterization of cardiac flow in heart disease patients by computational fluid dynamics and 4D flow MRI

NASA Astrophysics Data System (ADS)

Lantz, Jonas; Gupta, Vikas; Henriksson, Lilian; Karlsson, Matts; Persson, Ander; Carhall, Carljohan; Ebbers, Tino

2017-11-01

In this study, cardiac blood flow was simulated using Computational Fluid Dynamics and compared to in vivo flow measurements by 4D Flow MRI. In total, nine patients with various heart diseases were studied. Geometry and heart wall motion for the simulations were obtained from clinical CT measurements, with 0.3x0.3x0.3 mm spatial resolution and 20 time frames covering one heartbeat. The CFD simulations included pulmonary veins, left atrium and ventricle, mitral and aortic valve, and ascending aorta. Mesh sizes were on the order of 6-16 million cells, depending on the size of the heart, in order to resolve both papillary muscles and trabeculae. The computed flow field agreed visually very well with 4D Flow MRI, with characteristic vortices and flow structures seen in both techniques. Regression analysis showed that peak flow rate as well as stroke volume had an excellent agreement for the two techniques. We demonstrated the feasibility, and more importantly, fidelity of cardiac flow simulations by comparing CFD results to in vivo measurements. Both qualitative and quantitative results agreed well with the 4D Flow MRI measurements. Also, the developed simulation methodology enables ``what if'' scenarios, such as optimization of valve replacement and other surgical procedures. Funded by the Wallenberg Foundation.

Investigation of Patient-Specific Cerebral Aneurysm using Volumetric PIV, CFD, and In Vitro PC-MRI

NASA Astrophysics Data System (ADS)

Brindise, Melissa; Dickerhoff, Ben; Saloner, David; Rayz, Vitaliy; Vlachos, Pavlos

2017-11-01

4D PC-MRI is a modality capable of providing time-resolved velocity fields in cerebral aneurysms in vivo. The MRI-measured velocities and subsequent hemodynamic parameters such as wall shear stress, and oscillatory shear index, can help neurosurgeons decide a course of treatment for a patient, e.g. whether to treat or monitor the aneurysm. However, low spatiotemporal resolution, limited velocity dynamic range, and inherent noise of PC-MRI velocity fields can have a notable effect on subsequent calculations, and should be investigated. In this work, we compare velocity fields obtained with 4D PC-MRI, computational fluid dynamics (CFD) and volumetric particle image velocimetry (PIV), using a patient-specific model of a basilar tip aneurysm. The same in vitro model is used for all three modalities and flow input parameters are controlled. In vivo, PC-MRI data was also acquired for this patient and used for comparison. Specifically, we investigate differences in the resulting velocity fields and biases in subsequent calculations. Further, we explore the effect these errors may have on assessment of the aneurysm progression and seek to develop corrective algorithms and other methodologies that can be used to improve the accuracy of hemodynamic analysis in clinical setting.

Nonlinear Dynamic Modeling of a Supersonic Commercial Transport Turbo-Machinery Propulsion System for Aero-Propulso-Servo-Elasticity Research

NASA Technical Reports Server (NTRS)

Connolly, Joe; Carlson, Jan-Renee; Kopasakis, George; Woolwine, Kyle

2015-01-01

This paper covers the development of an integrated nonlinear dynamic model for a variable cycle turbofan engine, supersonic inlet, and convergent-divergent nozzle that can be integrated with an aeroelastic vehicle model to create an overall Aero-Propulso-Servo-Elastic (APSE) modeling tool. The primary focus of this study is to provide a means to capture relevant thrust dynamics of a full supersonic propulsion system by using relatively simple quasi-one dimensional computational fluid dynamics (CFD) methods that will allow for accurate control algorithm development and capture the key aspects of the thrust to feed into an APSE model. Previously, propulsion system component models have been developed and are used for this study of the fully integrated propulsion system. An overview of the methodology is presented for the modeling of each propulsion component, with a focus on its associated coupling for the overall model. To conduct APSE studies the described dynamic propulsion system model is integrated into a high fidelity CFD model of the full vehicle capable of conducting aero-elastic studies. Dynamic thrust analysis for the quasi-one dimensional dynamic propulsion system model is presented along with an initial three dimensional flow field model of the engine integrated into a supersonic commercial transport.

Aerodynamic design and analysis of small horizontal axis wind turbine blades

NASA Astrophysics Data System (ADS)

Tang, Xinzi

This work investigates the aerodynamic design and analysis of small horizontal axis wind turbine blades via the blade element momentum (BEM) based approach and the computational fluid dynamics (CFD) based approach. From this research, it is possible to draw a series of detailed guidelines on small wind turbine blade design and analysis. The research also provides a platform for further comprehensive study using these two approaches. The wake induction corrections and stall corrections of the BEM method were examined through a case study of the NREL/NASA Phase VI wind turbine. A hybrid stall correction model was proposed to analyse wind turbine power performance. The proposed model shows improvement in power prediction for the validation case, compared with the existing stall correction models. The effects of the key rotor parameters of a small wind turbine as well as the blade chord and twist angle distributions on power performance were investigated through two typical wind turbines, i.e. a fixed-pitch variable-speed (FPVS) wind turbine and a fixed-pitch fixed-speed (FPFS) wind turbine. An engineering blade design and analysis code was developed in MATLAB to accommodate aerodynamic design and analysis of the blades.. The linearisation for radial profiles of blade chord and twist angle for the FPFS wind turbine blade design was discussed. Results show that, the proposed linearisation approach leads to reduced manufacturing cost and higher annual energy production (AEP), with minimal effects on the low wind speed performance. Comparative studies of mesh and turbulence models in 2D and 3D CFD modelling were conducted. The CFD predicted lift and drag coefficients of the airfoil S809 were compared with wind tunnel test data and the 3D CFD modelling method of the NREL/NASA Phase VI wind turbine were validated against measurements. Airfoil aerodynamic characterisation and wind turbine power performance as well as 3D flow details were studied. The detailed flow characteristics from the CFD modelling are quantitatively comparable to the measurements, such as blade surface pressure distribution and integrated forces and moments. It is confirmed that the CFD approach is able to provide a more detailed qualitative and quantitative analysis for wind turbine airfoils and rotors..

Planar Inlet Design and Analysis Process (PINDAP)

NASA Technical Reports Server (NTRS)

Slater, John W.; Gruber, Christopher R.

2005-01-01

The Planar Inlet Design and Analysis Process (PINDAP) is a collection of software tools that allow the efficient aerodynamic design and analysis of planar (two-dimensional and axisymmetric) inlets. The aerodynamic analysis is performed using the Wind-US computational fluid dynamics (CFD) program. A major element in PINDAP is a Fortran 90 code named PINDAP that can establish the parametric design of the inlet and efficiently model the geometry and generate the grid for CFD analysis with design changes to those parameters. The use of PINDAP is demonstrated for subsonic, supersonic, and hypersonic inlets.

The Hydrodynamic Study of the Swimming Gliding: a Two-Dimensional Computational Fluid Dynamics (CFD) Analysis.

PubMed

Marinho, Daniel A; Barbosa, Tiago M; Rouboa, Abel I; Silva, António J

2011-09-01

Nowadays the underwater gliding after the starts and the turns plays a major role in the overall swimming performance. Hence, minimizing hydrodynamic drag during the underwater phases should be a main aim during swimming. Indeed, there are several postures that swimmers can assume during the underwater gliding, although experimental results were not conclusive concerning the best body position to accomplish this aim. Therefore, the purpose of this study was to analyse the effect in hydrodynamic drag forces of using different body positions during gliding through computational fluid dynamics (CFD) methodology. For this purpose, two-dimensional models of the human body in steady flow conditions were studied. Two-dimensional virtual models had been created: (i) a prone position with the arms extended at the front of the body; (ii) a prone position with the arms placed alongside the trunk; (iii) a lateral position with the arms extended at the front and; (iv) a dorsal position with the arms extended at the front. The drag forces were computed between speeds of 1.6 m/s and 2 m/s in a two-dimensional Fluent(®) analysis. The positions with the arms extended at the front presented lower drag values than the position with the arms aside the trunk. The lateral position was the one in which the drag was lower and seems to be the one that should be adopted during the gliding after starts and turns.

Recent Enhancements to the Development of CFD-Based Aeroelastic Reduced-Order Models

NASA Technical Reports Server (NTRS)

Silva, Walter A.

2007-01-01

Recent enhancements to the development of CFD-based unsteady aerodynamic and aeroelastic reduced-order models (ROMs) are presented. These enhancements include the simultaneous application of structural modes as CFD input, static aeroelastic analysis using a ROM, and matched-point solutions using a ROM. The simultaneous application of structural modes as CFD input enables the computation of the unsteady aerodynamic state-space matrices with a single CFD execution, independent of the number of structural modes. The responses obtained from a simultaneous excitation of the CFD-based unsteady aerodynamic system are processed using system identification techniques in order to generate an unsteady aerodynamic state-space ROM. Once the unsteady aerodynamic state-space ROM is generated, a method for computing the static aeroelastic response using this unsteady aerodynamic ROM and a state-space model of the structure, is presented. Finally, a method is presented that enables the computation of matchedpoint solutions using a single ROM that is applicable over a range of dynamic pressures and velocities for a given Mach number. These enhancements represent a significant advancement of unsteady aerodynamic and aeroelastic ROM technology.

CFD application to subsonic inlet airframe integration. [computational fluid dynamics (CFD)

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.

1988-01-01

The fluid dynamics of curved diffuser duct flows of military aircraft is discussed. Three-dimensional parabolized Navier-Stokes analysis, and experiment techniques are reviewed. Flow measurements and pressure distributions are shown. Velocity vectors, and the effects of vortex generators are considered.

Analysis of hydrodynamic force acting on commercialized rowing blades using computational fluid dynamics

NASA Astrophysics Data System (ADS)

Aziz, A. M. Y.; Harun, M. N.; Syahrom, Ardiyansyah; Omar, A. H.

2017-04-01

This paper presents a study of the hydrodynamics of several rowing blade designs. The study was done using Computational Fluid Dynamics (CFD) which enabled the investigation to be done similar to the experimental study, but with additional hydrodynamic visualization for further analysis and understanding. The CFD method was validated using quasi-static experimental data from Caplan (2007). Besides that, the proposed CFD analyses have improved the precious CFD results with the percentage of error of 6.58 percent of lift and 0.69 percent of drag force compared to 33.65 and 18.75 percent obtained by Coppel (2010). Consequent to the successful validation, the study then proceeded with the real size of Macon, Big balde and Fat blade. It was found that the hydrodynamic performance of the Fat blade was the highest due to the area, aspect ratio and the shape of the blade. Besides that, distribution of pressure for all models were also investigated which deepened the understanding of the blade fluid mechanics of rowing.

Analysis of Aerodynamic Load of LSU-03 (LAPAN Surveillance UAV-03) Propeller

NASA Astrophysics Data System (ADS)

Rahmadi Nuranto, Awang; Jamaludin Fitroh, Ahmad; Syamsudin, Hendri

2018-04-01

The existing propeller of the LSU-03 aircraft is made of wood. To improve structural strength and obtain better mechanical properties, the propeller will be redesigned usingcomposite materials. It is necessary to simulate and analyze the design load. This research paper explainsthe simulation and analysis of aerodynamic load prior to structural design phase of composite propeller. Aerodynamic load calculations are performed using both the Blade Element Theory(BET) and the Computational Fluid Dynamic (CFD)simulation. The result of both methods show a close agreement, the different thrust forces is only 1.2 and 4.1% for two type mesh. Thus the distribution of aerodynamic loads along the surface of the propeller blades of the 3-D CFD simulation results are considered valid and ready to design the composite structure. TheCFD results is directly imported to the structure model using the Direct Import CFD / One-Way Fluid Structure Interaction (FSI) method. Design load of propeller is chosen at the flight condition at speed of 20 km/h at 7000 rpm.

Application of Exactly Linearized Error Transport Equations to AIAA CFD Prediction Workshops

NASA Technical Reports Server (NTRS)

Derlaga, Joseph M.; Park, Michael A.; Rallabhandi, Sriram

2017-01-01

The computational fluid dynamics (CFD) prediction workshops sponsored by the AIAA have created invaluable opportunities in which to discuss the predictive capabilities of CFD in areas in which it has struggled, e.g., cruise drag, high-lift, and sonic boom pre diction. While there are many factors that contribute to disagreement between simulated and experimental results, such as modeling or discretization error, quantifying the errors contained in a simulation is important for those who make decisions based on the computational results. The linearized error transport equations (ETE) combined with a truncation error estimate is a method to quantify one source of errors. The ETE are implemented with a complex-step method to provide an exact linearization with minimal source code modifications to CFD and multidisciplinary analysis methods. The equivalency of adjoint and linearized ETE functional error correction is demonstrated. Uniformly refined grids from a series of AIAA prediction workshops demonstrate the utility of ETE for multidisciplinary analysis with a connection between estimated discretization error and (resolved or under-resolved) flow features.

Assessment of CFD Hypersonic Turbulent Heating Rates for Space Shuttle Orbiter

NASA Technical Reports Server (NTRS)

Wood, William A.; Oliver, A. Brandon

2011-01-01

Turbulent CFD codes are assessed for the prediction of convective heat transfer rates at turbulent, hypersonic conditions. Algebraic turbulence models are used within the DPLR and LAURA CFD codes. The benchmark heat transfer rates are derived from thermocouple measurements of the Space Shuttle orbiter Discovery windward tiles during the STS-119 and STS-128 entries. The thermocouples were located underneath the reaction-cured glass coating on the thermal protection tiles. Boundary layer transition flight experiments conducted during both of those entries promoted turbulent flow at unusually high Mach numbers, with the present analysis considering Mach 10{15. Similar prior comparisons of CFD predictions directly to the flight temperature measurements were unsatisfactory, showing diverging trends between prediction and measurement for Mach numbers greater than 11. In the prior work, surface temperatures and convective heat transfer rates had been assumed to be in radiative equilibrium. The present work employs a one-dimensional time-accurate conduction analysis to relate measured temperatures to surface heat transfer rates, removing heat soak lag from the flight data, in order to better assess the predictive accuracy of the numerical models. The turbulent CFD shows good agreement for turbulent fuselage flow up to Mach 13. But on the wing in the wake of the boundary layer trip, the inclusion of tile conduction effects does not explain the prior observed discrepancy in trends between simulation and experiment; the flight heat transfer measurements are roughly constant over Mach 11-15, versus an increasing trend with Mach number from the CFD.

Computational fluid dynamics modeling of laboratory flames and an industrial flare.

PubMed

Singh, Kanwar Devesh; Gangadharan, Preeti; Chen, Daniel H; Lou, Helen H; Li, Xianchang; Richmond, Peyton

2014-11-01

A computational fluid dynamics (CFD) methodology for simulating the combustion process has been validated with experimental results. Three different types of experimental setups were used to validate the CFD model. These setups include an industrial-scale flare setups and two lab-scale flames. The CFD study also involved three different fuels: C3H6/CH/Air/N2, C2H4/O2/Ar and CH4/Air. In the first setup, flare efficiency data from the Texas Commission on Environmental Quality (TCEQ) 2010 field tests were used to validate the CFD model. In the second setup, a McKenna burner with flat flames was simulated. Temperature and mass fractions of important species were compared with the experimental data. Finally, results of an experimental study done at Sandia National Laboratories to generate a lifted jet flame were used for the purpose of validation. The reduced 50 species mechanism, LU 1.1, the realizable k-epsilon turbulence model, and the EDC turbulence-chemistry interaction model were usedfor this work. Flare efficiency, axial profiles of temperature, and mass fractions of various intermediate species obtained in the simulation were compared with experimental data and a good agreement between the profiles was clearly observed. In particular the simulation match with the TCEQ 2010 flare tests has been significantly improved (within 5% of the data) compared to the results reported by Singh et al. in 2012. Validation of the speciated flat flame data supports the view that flares can be a primary source offormaldehyde emission.

CFD analysis of a twin scroll radial turbine

NASA Astrophysics Data System (ADS)

Fürst, Jiří; Žák, Zdenĕk

2018-06-01

The contribution deals with the application of coupled implicit solver for compressible flows to CFD analysis of a twin scroll radial turbine. The solver is based on the finite volume method, convective terms are approximated using AUSM+up scheme, viscous terms use central approximation and the time evolution is achieved with lower-upper symmetric Gauss-Seidel (LU-SGS) method. The solver allows steady simulation with the so called frozen rotor approach as well as the fully unsteady solution. Both approaches are at first validated for the case of ERCOFTAC pump [1]. Then the CFD analysis of the flow through a twin scroll radial turbine and the predictions of the efficiency and turbine power is performed and the results are compared to experimental data obtained in the framework of Josef Božek - Competence Centre for Automotive Industry.

Statistical Analysis of CFD Solutions from the 6th AIAA CFD Drag Prediction Workshop

NASA Technical Reports Server (NTRS)

Derlaga, Joseph M.; Morrison, Joseph H.

2017-01-01

A graphical framework is used for statistical analysis of the results from an extensive N- version test of a collection of Reynolds-averaged Navier-Stokes computational uid dynam- ics codes. The solutions were obtained by code developers and users from North America, Europe, Asia, and South America using both common and custom grid sequencees as well as multiple turbulence models for the June 2016 6th AIAA CFD Drag Prediction Workshop sponsored by the AIAA Applied Aerodynamics Technical Committee. The aerodynamic con guration for this workshop was the Common Research Model subsonic transport wing- body previously used for both the 4th and 5th Drag Prediction Workshops. This work continues the statistical analysis begun in the earlier workshops and compares the results from the grid convergence study of the most recent workshop with previous workshops.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Thomas M.; Berndt, Markus; Baglietto, Emilio

The purpose of this report is to document a multi-year plan for enhancing turbulence modeling in Hydra-TH for the Consortium for Advanced Simulation of Light Water Reactors (CASL) program. Hydra-TH is being developed to the meet the high- fidelity, high-Reynolds number CFD based thermal hydraulic simulation needs of the program. This work is being conducted within the thermal hydraulics methods (THM) focus area. This report is an extension of THM CASL milestone L3:THM.CFD.P10.02 [33] (March, 2015) and picks up where it left off. It will also serve to meet the requirements of CASL THM level three milestone, L3:THM.CFD.P11.04, scheduled formore » completion September 30, 2015. The objectives of this plan will be met by: maturation of recently added turbulence models, strategic design/development of new models and systematic and rigorous testing of existing and new models and model extensions. While multi-phase turbulent flow simulations are important to the program, only single-phase modeling will be considered in this report. Large Eddy Simulation (LES) is also an important modeling methodology. However, at least in the first year, the focus is on steady-state Reynolds Averaged Navier-Stokes (RANS) turbulence modeling.« less

Computational fluid dynamics (CFD) assisted performance evaluation of the Twincer™ disposable high-dose dry powder inhaler.

PubMed

de Boer, Anne H; Hagedoorn, Paul; Woolhouse, Robert; Wynn, Ed

2012-09-01

To use computational fluid dynamics (CFD) for evaluating and understanding the performance of the high-dose disposable Twincer™ dry powder inhaler, as well as to learn the effect of design modifications on dose entrainment, powder dispersion and retention behaviour. Comparison of predicted flow and particle behaviour from CFD computations with experimental data obtained with cascade impactor and laser diffraction analysis. Inhaler resistance, flow split, particle trajectories and particle residence times can well be predicted with CFD for a multiple classifier based inhaler like the Twincer™. CFD computations showed that the flow split of the Twincer™ is independent of the pressure drop across the inhaler and that the total flow rate can be decreased without affecting the dispersion efficacy or retention behaviour. They also showed that classifier symmetry can be improved by reducing the resistance of one of the classifier bypass channels, which for the current concept does not contribute to the swirl in the classifier chamber. CFD is a highly valuable tool for development and optimisation of dry powder inhalers. CFD can assist adapting the inhaler design to specific physico-chemical properties of the drug formulation with respect to dispersion and retention behaviour. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Application of CFD codes to the design and development of propulsion systems

NASA Technical Reports Server (NTRS)

Lord, W. K.; Pickett, G. F.; Sturgess, G. J.; Weingold, H. D.

1987-01-01

The internal flows of aerospace propulsion engines have certain common features that are amenable to analysis through Computational Fluid Dynamics (CFD) computer codes. Although the application of CFD to engineering problems in engines was delayed by the complexities associated with internal flows, many codes with different capabilities are now being used as routine design tools. This is illustrated by examples taken from the aircraft gas turbine engine of flows calculated with potential flow, Euler flow, parabolized Navier-Stokes, and Navier-Stokes codes. Likely future directions of CFD applied to engine flows are described, and current barriers to continued progress are highlighted. The potential importance of the Numerical Aerodynamic Simulator (NAS) to resolution of these difficulties is suggested.

Accumulation and transport of microbial-size particles in a pressure protected model burn unit: CFD simulations and experimental evidence

PubMed Central

2011-01-01

Background Controlling airborne contamination is of major importance in burn units because of the high susceptibility of burned patients to infections and the unique environmental conditions that can accentuate the infection risk. In particular the required elevated temperatures in the patient room can create thermal convection flows which can transport airborne contaminates throughout the unit. In order to estimate this risk and optimize the design of an intensive care room intended to host severely burned patients, we have relied on a computational fluid dynamic methodology (CFD). Methods The study was carried out in 4 steps: i) patient room design, ii) CFD simulations of patient room design to model air flows throughout the patient room, adjacent anterooms and the corridor, iii) construction of a prototype room and subsequent experimental studies to characterize its performance iv) qualitative comparison of the tendencies between CFD prediction and experimental results. The Electricité De France (EDF) open-source software Code_Saturne® (http://www.code-saturne.org) was used and CFD simulations were conducted with an hexahedral mesh containing about 300 000 computational cells. The computational domain included the treatment room and two anterooms including equipment, staff and patient. Experiments with inert aerosol particles followed by time-resolved particle counting were conducted in the prototype room for comparison with the CFD observations. Results We found that thermal convection can create contaminated zones near the ceiling of the room, which can subsequently lead to contaminate transfer in adjacent rooms. Experimental confirmation of these phenomena agreed well with CFD predictions and showed that particles greater than one micron (i.e. bacterial or fungal spore sizes) can be influenced by these thermally induced flows. When the temperature difference between rooms was 7°C, a significant contamination transfer was observed to enter into the positive pressure room when the access door was opened, while 2°C had little effect. Based on these findings the constructed burn unit was outfitted with supplemental air exhaust ducts over the doors to compensate for the thermal convective flows. Conclusions CFD simulations proved to be a particularly useful tool for the design and optimization of a burn unit treatment room. Our results, which have been confirmed qualitatively by experimental investigation, stressed that airborne transfer of microbial size particles via thermal convection flows are able to bypass the protective overpressure in the patient room, which can represent a potential risk of cross contamination between rooms in protected environments. PMID:21371304

Accumulation and transport of microbial-size particles in a pressure protected model burn unit: CFD simulations and experimental evidence.

PubMed

Beauchêne, Christian; Laudinet, Nicolas; Choukri, Firas; Rousset, Jean-Luc; Benhamadouche, Sofiane; Larbre, Juliette; Chaouat, Marc; Benbunan, Marc; Mimoun, Maurice; Lajonchère, Jean-Patrick; Bergeron, Vance; Derouin, Francis

2011-03-03

Controlling airborne contamination is of major importance in burn units because of the high susceptibility of burned patients to infections and the unique environmental conditions that can accentuate the infection risk. In particular the required elevated temperatures in the patient room can create thermal convection flows which can transport airborne contaminates throughout the unit. In order to estimate this risk and optimize the design of an intensive care room intended to host severely burned patients, we have relied on a computational fluid dynamic methodology (CFD). The study was carried out in 4 steps: i) patient room design, ii) CFD simulations of patient room design to model air flows throughout the patient room, adjacent anterooms and the corridor, iii) construction of a prototype room and subsequent experimental studies to characterize its performance iv) qualitative comparison of the tendencies between CFD prediction and experimental results. The Electricité De France (EDF) open-source software Code_Saturne® (http://www.code-saturne.org) was used and CFD simulations were conducted with an hexahedral mesh containing about 300 000 computational cells. The computational domain included the treatment room and two anterooms including equipment, staff and patient. Experiments with inert aerosol particles followed by time-resolved particle counting were conducted in the prototype room for comparison with the CFD observations. We found that thermal convection can create contaminated zones near the ceiling of the room, which can subsequently lead to contaminate transfer in adjacent rooms. Experimental confirmation of these phenomena agreed well with CFD predictions and showed that particles greater than one micron (i.e. bacterial or fungal spore sizes) can be influenced by these thermally induced flows. When the temperature difference between rooms was 7°C, a significant contamination transfer was observed to enter into the positive pressure room when the access door was opened, while 2°C had little effect. Based on these findings the constructed burn unit was outfitted with supplemental air exhaust ducts over the doors to compensate for the thermal convective flows. CFD simulations proved to be a particularly useful tool for the design and optimization of a burn unit treatment room. Our results, which have been confirmed qualitatively by experimental investigation, stressed that airborne transfer of microbial size particles via thermal convection flows are able to bypass the protective overpressure in the patient room, which can represent a potential risk of cross contamination between rooms in protected environments.

Computational analysis of Variable Thrust Engine (VTE) performance

NASA Technical Reports Server (NTRS)

Giridharan, M. G.; Krishnan, A.; Przekwas, A. J.

1993-01-01

The Variable Thrust Engine (VTE) of the Orbital Maneuvering Vehicle (OMV) uses a hypergolic propellant combination of Monomethyl Hydrazine (MMH) and Nitrogen Tetroxide (NTO) as fuel and oxidizer, respectively. The performance of the VTE depends on a number of complex interacting phenomena such as atomization, spray dynamics, vaporization, turbulent mixing, convective/radiative heat transfer, and hypergolic combustion. This study involved the development of a comprehensive numerical methodology to facilitate detailed analysis of the VTE. An existing Computational Fluid Dynamics (CFD) code was extensively modified to include the following models: a two-liquid, two-phase Eulerian-Lagrangian spray model; a chemical equilibrium model; and a discrete ordinate radiation heat transfer model. The modified code was used to conduct a series of simulations to assess the effects of various physical phenomena and boundary conditions on the VTE performance. The details of the models and the results of the simulations are presented.

Wind tunnel data of the analysis of heat pipe and wind catcher technology for the built environment

PubMed Central

Calautit, John Kaiser; Chaudhry, Hassam Nasarullah; Hughes, Ben Richard

2015-01-01

The data presented in this article were the basis for the study reported in the research articles entitled ‘Climate responsive behaviour heat pipe technology for enhanced passive airside cooling’ by Chaudhry and Hughes [10] which presents the passive airside cooling capability of heat pipes in response to gradually varying external temperatures and related to the research article “CFD and wind tunnel study of the performance of a uni-directional wind catcher with heat transfer devices” by Calautit and Hughes [1] which compares the ventilation performance of a standard roof mounted wind catcher and wind catcher incorporating the heat pipe technology. Here, we detail the wind tunnel test set-up and inflow conditions and the methodologies for the transient heat pipe experiment and analysis of the integration of heat pipes within the control domain of a wind catcher design. PMID:26958604

Wind tunnel data of the analysis of heat pipe and wind catcher technology for the built environment.

PubMed

Calautit, John Kaiser; Chaudhry, Hassam Nasarullah; Hughes, Ben Richard

2015-12-01

The data presented in this article were the basis for the study reported in the research articles entitled 'Climate responsive behaviour heat pipe technology for enhanced passive airside cooling' by Chaudhry and Hughes [10] which presents the passive airside cooling capability of heat pipes in response to gradually varying external temperatures and related to the research article "CFD and wind tunnel study of the performance of a uni-directional wind catcher with heat transfer devices" by Calautit and Hughes [1] which compares the ventilation performance of a standard roof mounted wind catcher and wind catcher incorporating the heat pipe technology. Here, we detail the wind tunnel test set-up and inflow conditions and the methodologies for the transient heat pipe experiment and analysis of the integration of heat pipes within the control domain of a wind catcher design.

Investigation of Low-Reynolds-Number Rocket Nozzle Design Using PNS-Based Optimization Procedure

NASA Technical Reports Server (NTRS)

Hussaini, M. Moin; Korte, John J.

1996-01-01

An optimization approach to rocket nozzle design, based on computational fluid dynamics (CFD) methodology, is investigated for low-Reynolds-number cases. This study is undertaken to determine the benefits of this approach over those of classical design processes such as Rao's method. A CFD-based optimization procedure, using the parabolized Navier-Stokes (PNS) equations, is used to design conical and contoured axisymmetric nozzles. The advantage of this procedure is that it accounts for viscosity during the design process; other processes make an approximated boundary-layer correction after an inviscid design is created. Results showed significant improvement in the nozzle thrust coefficient over that of the baseline case; however, the unusual nozzle design necessitates further investigation of the accuracy of the PNS equations for modeling expanding flows with thick laminar boundary layers.

Missile Flight Control Using micro-Actuated Flow Effectors - Review of Fiscal Year 2005/2006 Progress

DTIC Science & Technology

2006-08-01

be developed. A common analysis model covering the aerodynamic-flow effector interaction, the compliant mechanism-SMA dynamics and the control...additional CFD analysis for the finless DRDC-B1AC2R between 15 deg. to 20 deg. to determine where the peak side force is situated. Compare pressure...Carry out CFD study on DRDC-B1AC2R with fins. Decide on analysis matrix. Coordinate with wind tunnel test matrix. Action: DRDC-nh Y0405-7. Decide

Computational Fluid Dynamic Investigation of Loss Mechanisms in a Pulse-Tube Refrigerator

NASA Astrophysics Data System (ADS)

Martin, K.; Esguerra, J.; Dodson, C.; Razani, A.

2015-12-01

In predicting Pulse-Tube Cryocooler (PTC) performance, One-Dimensional (1-D) PTR design and analysis tools such as Gedeon Associates SAGE® typically include models for performance degradation due to thermodynamically irreversible processes. SAGE®, in particular, accounts for convective loss, turbulent conductive loss and numerical diffusion “loss” via correlation functions based on analysis and empirical testing. In this study, we compare CFD and SAGE® estimates of PTR refrigeration performance for four distinct pulse-tube lengths. Performance predictions from PTR CFD models are compared to SAGE® predictions for all four cases. Then, to further demonstrate the benefits of higher-fidelity and multidimensional CFD simulation, the PTR loss mechanisms are characterized in terms of their spatial and temporal locations.

Algorithmic trends in computational fluid dynamics; The Institute for Computer Applications in Science and Engineering (ICASE)/LaRC Workshop, NASA Langley Research Center, Hampton, VA, US, Sep. 15-17, 1991

NASA Technical Reports Server (NTRS)

Hussaini, M. Y. (Editor); Kumar, A. (Editor); Salas, M. D. (Editor)

1993-01-01

The purpose here is to assess the state of the art in the areas of numerical analysis that are particularly relevant to computational fluid dynamics (CFD), to identify promising new developments in various areas of numerical analysis that will impact CFD, and to establish a long-term perspective focusing on opportunities and needs. Overviews are given of discretization schemes, computational fluid dynamics, algorithmic trends in CFD for aerospace flow field calculations, simulation of compressible viscous flow, and massively parallel computation. Also discussed are accerelation methods, spectral and high-order methods, multi-resolution and subcell resolution schemes, and inherently multidimensional schemes.

Computational fluid dynamics analysis of a maglev centrifugal left ventricular assist device.

PubMed

Burgreen, Greg W; Loree, Howard M; Bourque, Kevin; Dague, Charles; Poirier, Victor L; Farrar, David; Hampton, Edward; Wu, Z Jon; Gempp, Thomas M; Schöb, Reto

2004-10-01

The fluid dynamics of the Thoratec HeartMate III (Thoratec Corp., Pleasanton, CA, U.S.A.) left ventricular assist device are analyzed over a range of physiological operating conditions. The HeartMate III is a centrifugal flow pump with a magnetically suspended rotor. The complete pump was analyzed using computational fluid dynamics (CFD) analysis and experimental particle imaging flow visualization (PIFV). A comparison of CFD predictions to experimental imaging shows good agreement. Both CFD and experimental PIFV confirmed well-behaved flow fields in the main components of the HeartMate III pump: inlet, volute, and outlet. The HeartMate III is shown to exhibit clean flow features and good surface washing across its entire operating range.

Preliminary design of mesoscale turbocompressor and rotordynamics tests of rotor bearing system

NASA Astrophysics Data System (ADS)

Hossain, Md Saddam

2011-12-01

A mesoscale turbocompressor spinning above 500,000 RPM is evolutionary technology for micro turbochargers, turbo blowers, turbo compressors, micro-gas turbines, auxiliary power units, etc for automotive, aerospace, and fuel cell industries. Objectives of this work are: (1) to evaluate different air foil bearings designed for the intended applications, and (2) to design & perform CFD analysis of a micro-compressor. CFD analysis of shrouded 3-D micro compressor was conducted using Ansys Bladegen as blade generation tool, ICEM CFD as mesh generation tool, and CFX as main solver for different design and off design cases and also for different number of blades. Comprehensive experimental facilities for testing the turbocompressor system have been also designed and proposed for future work.

CFD Simulation on the J-2X Engine Exhaust in the Center-Body Diffuser and Spray Chamber at the B-2 Facility

NASA Technical Reports Server (NTRS)

Wang, Xiao-Yen; Wey, Thomas; Buehrle, Robert

2009-01-01

A computational fluid dynamic (CFD) code is used to simulate the J-2X engine exhaust in the center-body diffuser and spray chamber at the Spacecraft Propulsion Facility (B-2). The CFD code is named as the space-time conservation element and solution element (CESE) Euler solver and is very robust at shock capturing. The CESE results are compared with independent analysis results obtained by using the National Combustion Code (NCC) and show excellent agreement.

Analysis and Design of a Double-Divert Spiral Groove Seal

NASA Technical Reports Server (NTRS)

Zheng, Xiaoqing; Berard, Gerald

2007-01-01

This viewgraph presentation describes the design and analysis of a double spiral groove seal. The contents include: 1) Double Spiral Design Features; 2) Double Spiral Operational Features; 3) Mating Ring/Rotor Assembly; 4) Seal Ring Assembly; 5) Insert Segment Joints; 6) Rotor Assembly Completed Prototype Parts; 7) Seal Assembly Completed Prototype Parts; 8) Finite Element Analysis; 9) Computational Fluid Dynamics (CFD) Analysis; 10) Restrictive Orifice Design; 11) Orifice CFD Model; 12) Orifice Results; 13) Restrictive Orifice; 14) Seal Face Coning; 15) Permanent Magnet Analysis; 16) Magnetic Repulsive Force; 17) Magnetic Repulsive Test Results; 18) Spin Testing; and 19) Testing and Validation.

Alu–based cell-free DNA: a novel biomarker for screening of gastric cancer

PubMed Central

Zhao, Jianmei; Shen, Xianjuan; Jing, Rongrong; Yu, Juan; Li, Li; Shi, Yingjuan; Zhang, Lurong; Wang, Zhiwei; Cong, Hui

2017-01-01

Gastric cancer (GC) is the fourth most common cancer and the second major cause of cancer-related deaths worldwide. In our previous study, a novel and sensitive method for quantifying cell-free DNA (CFD) in human blood was established and tested for its ability to predict patients with tumor. We want to investigate CFD expression in the sera of GC patients in an attempt to explore the clinical significance of CFD in improving the early screening of GC and monitoring GC progression by the branched DNA (bDNA)-based Alu assay. The concentration of CFD was quantitated by bDNA-based Alu assay. CEA, CA19-9, C72-4 and CA50 concentrations were determined by ABBOTT ARCHITECT I2000 SR. We found the CFD concentrations have significant differences between GC patients, benign gastric disease (BGD) patients and healthy controls (P < 0.05). CFD were weakly correlated with CEA (r = −0.197, P < 0.05) or CA50 (r = 0.206, P < 0.05), and no correlation with CA19-9 (r = −0.061, P > 0.05) or CA72-4 (r = 0.011, P > 0.05). In addition, CFD concentrations were significantly higher in stage I GC patients than BGD patients and healthy controls (P < 0.05), but there was no significant difference in CEA, CA19-9 and CA50 among the three traditional tumor markers (P > 0.05). Our analysis showed that CFD was more sensitive than CEA, CA19-9, CA72-4 or CA50 in early screening of GC. Compared with CEA, CA19-9, CA72-4 and CA50, CFD may prove to be a better biomarker for the screening of GC, thus providing a sensitive biomarker for screening and monitoring progression of GC. PMID:28903321

Computational Flow Modeling of Human Upper Airway Breathing

NASA Astrophysics Data System (ADS)

Mylavarapu, Goutham

Computational modeling of biological systems have gained a lot of interest in biomedical research, in the recent past. This thesis focuses on the application of computational simulations to study airflow dynamics in human upper respiratory tract. With advancements in medical imaging, patient specific geometries of anatomically accurate respiratory tracts can now be reconstructed from Magnetic Resonance Images (MRI) or Computed Tomography (CT) scans, with better and accurate details than traditional cadaver cast models. Computational studies using these individualized geometrical models have advantages of non-invasiveness, ease, minimum patient interaction, improved accuracy over experimental and clinical studies. Numerical simulations can provide detailed flow fields including velocities, flow rates, airway wall pressure, shear stresses, turbulence in an airway. Interpretation of these physical quantities will enable to develop efficient treatment procedures, medical devices, targeted drug delivery etc. The hypothesis for this research is that computational modeling can predict the outcomes of a surgical intervention or a treatment plan prior to its application and will guide the physician in providing better treatment to the patients. In the current work, three different computational approaches Computational Fluid Dynamics (CFD), Flow-Structure Interaction (FSI) and Particle Flow simulations were used to investigate flow in airway geometries. CFD approach assumes airway wall as rigid, and relatively easy to simulate, compared to the more challenging FSI approach, where interactions of airway wall deformations with flow are also accounted. The CFD methodology using different turbulence models is validated against experimental measurements in an airway phantom. Two case-studies using CFD, to quantify a pre and post-operative airway and another, to perform virtual surgery to determine the best possible surgery in a constricted airway is demonstrated. The unsteady Large Eddy simulations (LES) and a steady Reynolds Averaged Navier Stokes (RANS) approaches in CFD modeling are discussed. The more challenging FSI approach is modeled first in simple two-dimensional anatomical geometry and then extended to simplified three dimensional geometry and finally in three dimensionally accurate geometries. The concepts of virtual surgery and the differences to CFD are discussed. Finally, the influence of various drug delivery parameters on particle deposition efficiency in airway anatomy are investigated through particle-flow simulations in a nasal airway model.

Indirect contact freeze water desalination for an ice maker machine - CFD simulation

NASA Astrophysics Data System (ADS)

Jayakody, Harith; Al-Dadah, Raya; Mahmoud, Saad

2017-11-01

To offer for potable water shortages, sea water desalination is a potential solution for the global rising demand for fresh water. The latent heat of fusion is about one-seventh the latent heat of vaporisation, thus indicating the benefit of lower energy consumption for the freeze desalination process. Limited literature is reported on computational fluid dynamics (CFD) on freeze desalination. Therefore, analysing and investigating thermodynamic processes are easily conducted by the powerful tool of CFD. A single unit of ice formation in an ice maker machine was modelled using ANSYS Fluent software three-dimensionally. Energy, species transport and solidification/melting modules were used in building the CFD model. Parametric analysis was conducted using the established CFD model to predict the effects of freezing temperature and the geometry of the ice maker machine; on ice production and the freezing time. Lower freezing temperatures allowed more ice production and faster freezing. Increasing the diameter and the length of the freezing tube enabled more ice to be produced.

Comparison of Computed and Measured Vortex Evolution for a UH-60A Rotor in Forward Flight

NASA Technical Reports Server (NTRS)

Ahmad, Jasim Uddin; Yamauchi, Gloria K.; Kao, David L.

2013-01-01

A Computational Fluid Dynamics (CFD) simulation using the Navier-Stokes equations was performed to determine the evolutionary and dynamical characteristics of the vortex flowfield for a highly flexible aeroelastic UH-60A rotor in forward flight. The experimental wake data were acquired using Particle Image Velocimetry (PIV) during a test of the fullscale UH-60A rotor in the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel. The PIV measurements were made in a stationary cross-flow plane at 90 deg rotor azimuth. The CFD simulation was performed using the OVERFLOW CFD solver loosely coupled with the rotorcraft comprehensive code CAMRAD II. Characteristics of vortices captured in the PIV plane from different blades are compared with CFD calculations. The blade airloads were calculated using two different turbulence models. A limited spatial, temporal, and CFD/comprehensive-code coupling sensitivity analysis was performed in order to verify the unsteady helicopter simulations with a moving rotor grid system.

Simulation studies on the standing and traveling wave thermoacoustic prime movers

NASA Astrophysics Data System (ADS)

Skaria, Mathew; Rasheed, K. K. Abdul; Shafi, K. A.; Kasthurirengan, S.; Behera, Upendra

2014-01-01

Thermoacoustic systems have been a focus of recent research due to its structural simplicity, high reliability due to absence of moving parts, and can be driven by low grade energy such as fuel, gas, solar energy, waste heat etc. There has been extensive research on both standing wave and traveling wave systems. Towards the development of such systems, simulations can be carried out by several methods such as (a) solving the energy equation, (b) enthalpy flow model, (c) DeltaEC, a free software available from LANL, USA (d) Computational Fluid Dynamics (CFD) etc. We present here the simulation studies of standing wave and traveling wave thermoacoustic prime movers using CFD and DeltaEC. The CFD analysis is carried out using Fluent 6.3.26, incorporating the necessary boundary conditions with different working fluids at different operating pressures. The results obtained by CFD are compared with those obtained using DeltaEC. Also, the CFD simulation of the thermoacoustically driven refrigerator is presented.

Simulation studies on the standing and traveling wave thermoacoustic prime movers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skaria, Mathew; Rasheed, K. K. Abdul; Shafi, K. A.

Thermoacoustic systems have been a focus of recent research due to its structural simplicity, high reliability due to absence of moving parts, and can be driven by low grade energy such as fuel, gas, solar energy, waste heat etc. There has been extensive research on both standing wave and traveling wave systems. Towards the development of such systems, simulations can be carried out by several methods such as (a) solving the energy equation, (b) enthalpy flow model, (c) DeltaEC, a free software available from LANL, USA (d) Computational Fluid Dynamics (CFD) etc. We present here the simulation studies of standingmore » wave and traveling wave thermoacoustic prime movers using CFD and DeltaEC. The CFD analysis is carried out using Fluent 6.3.26, incorporating the necessary boundary conditions with different working fluids at different operating pressures. The results obtained by CFD are compared with those obtained using DeltaEC. Also, the CFD simulation of the thermoacoustically driven refrigerator is presented.« less

SRM Internal Flow Tests and Computational Fluid Dynamic Analysis. Volume 2; CFD RSRM Full-Scale Analyses

NASA Technical Reports Server (NTRS)

2001-01-01

This document presents the full-scale analyses of the CFD RSRM. The RSRM model was developed with a 20 second burn time. The following are presented as part of the full-scale analyses: (1) RSRM embedded inclusion analysis; (2) RSRM igniter nozzle design analysis; (3) Nozzle Joint 4 erosion anomaly; (4) RSRM full motor port slag accumulation analysis; (5) RSRM motor analysis of two-phase flow in the aft segment/submerged nozzle region; (6) Completion of 3-D Analysis of the hot air nozzle manifold; (7) Bates Motor distributed combustion test case; and (8) Three Dimensional Polysulfide Bump Analysis.

Thermodynamic Cycle and CFD Analyses for Hydrogen Fueled Air-breathing Pulse Detonation Engines

NASA Technical Reports Server (NTRS)

Povinelli, Louis A.; Yungster, Shaye

2002-01-01

This paper presents the results of a thermodynamic cycle analysis of a pulse detonation engine (PDE) using a hydrogen-air mixture at static conditions. The cycle performance results, namely the specific thrust, fuel consumption and impulse are compared to a single cycle CFD analysis for a detonation tube which considers finite rate chemistry. The differences in the impulse values were indicative of the additional performance potential attainable in a PDE.

An Application of Overset Grids to Payload/Fairing Three-Dimensional Internal Flow CFD Analysis

NASA Technical Reports Server (NTRS)

Kandula, Max; Nallasamy, R.; Schallhorn, P.; Duncil, L.

2007-01-01

The application of overset grids to the computational fluid dynamics analysis of three-dimensional internal flow in the payload/fairing of an expendable launch vehicle is described. In conjunction with the overset grid system, the flowfield in the payload/fairing configuration is obtained with the aid of OVERFLOW Navier-Stokes code. The solution exhibits a highly three dimensional complex flowfield with swirl, separation, and vortices. Some of the computed flow features are compared with the measured Laser-Doppler Velocimetry (LDV) data on a 1/5th scale model of the payload/fairing configuration. The counter-rotating vortex structures and the location of the saddle point predicted by the CFD analysis are in general agreement with the LDV data. Comparisons of the computed (CFD) velocity profiles on horizontal and vertical lines in the LDV measurement plane in the faring nose region show reasonable agreement with the LDV data.

Numerical analysis of eccentric orifice plate using ANSYS Fluent software

NASA Astrophysics Data System (ADS)

Zahariea, D.

2016-11-01

In this paper the eccentric orifice plate is qualitative analysed as compared with the classical concentric orifice plate from the point of view of sedimentation tendency of solid particles in the fluid whose flow rate is measured. For this purpose, the numerical streamlines pattern will be compared for both orifice plates. The numerical analysis has been performed using ANSYS Fluent software. The methodology of CFD analysis is presented: creating the 3D solid model, fluid domain extraction, meshing, boundary condition, turbulence model, solving algorithm, convergence criterion, results and validation. Analysing the numerical streamlines, for the concentric orifice plate can be clearly observed two circumferential regions of separated flows, upstream and downstream of the orifice plate. The bottom part of these regions are the place where the solid particles could sediment. On the other hand, for the eccentric orifice plate, the streamlines pattern suggest that no sedimentation will occur because at the bottom area of the pipe there are no separated flows.

Energy saving by using asymmetric aftbodies for merchant ships-design methodology, numerical simulation and validation

NASA Astrophysics Data System (ADS)

Dang, Jie; Chen, Hao

2016-12-01

The methodology and procedures are discussed on designing merchant ships to achieve fully-integrated and optimized hull-propulsion systems by using asymmetric aftbodies. Computational fluid dynamics (CFD) has been used to evaluate the powering performance through massive calculations with automatic deformation algorisms for the hull forms and the propeller blades. Comparative model tests of the designs to the optimized symmetric hull forms have been carried out to verify the efficiency gain. More than 6% improvement on the propulsive efficiency of an oil tanker has been measured during the model tests. Dedicated sea-trials show good agreement with the predicted performance from the test results.

Multiphysics Simulation of Welding-Arc and Nozzle-Arc System: Mathematical-Model, Solution-Methodology and Validation

NASA Astrophysics Data System (ADS)

Pawar, Sumedh; Sharma, Atul

2018-01-01

This work presents mathematical model and solution methodology for a multiphysics engineering problem on arc formation during welding and inside a nozzle. A general-purpose commercial CFD solver ANSYS FLUENT 13.0.0 is used in this work. Arc formation involves strongly coupled gas dynamics and electro-dynamics, simulated by solution of coupled Navier-Stoke equations, Maxwell's equations and radiation heat-transfer equation. Validation of the present numerical methodology is demonstrated with an excellent agreement with the published results. The developed mathematical model and the user defined functions (UDFs) are independent of the geometry and are applicable to any system that involves arc-formation, in 2D axisymmetric coordinates system. The high-pressure flow of SF6 gas in the nozzle-arc system resembles arc chamber of SF6 gas circuit breaker; thus, this methodology can be extended to simulate arcing phenomenon during current interruption.

Predictive Evaluations of Oxygen-Rich Hydrocarbon Combustion Gas-Centered Swirl Coaxial Injectors using a Flamelet-Based 3-D CFD Simulation Approach

NASA Technical Reports Server (NTRS)

Richardson, Brian R.; Braman, Kalem; West, Jeff

2016-01-01

NASA Marshall Space Flight Center (MSFC) has embarked upon a joint project with the Air Force to improve the state-of-the-art of space application combustion device design and operational understanding. One goal of the project is to design, build and hot-fire test a 40,000 pound-thrust Oxygen/Rocket Propellant-2 (RP-2) Oxygen-Rich staged engine at MSFC. The overall project goals afford the opportunity to test multiple different injector designs and experimentally evaluate the any effect on the engine performance and combustion dynamics. To maximize the available test resources and benefits, pre-test, combusting flow, Computational Fluid Dynamics (CFD) analysis was performed on the individual injectors to guide the design. The results of the CFD analysis were used to design the injectors for specific, targeted fluid dynamic features and the analysis results also provided some predictive input for acoustic and thermal analysis of the main Thrust Chamber Assembly (TCA). MSFC has developed and demonstrated the ability to utilize a computationally efficient, flamelet-based combustion model to guide the pre-test design of single-element Gas Centered Swirl Coaxial (GCSC) injectors. Previous, Oxygen/RP-2 simulation models utilizing the Loci-STREAM flow solver, were validated using single injector test data from the EC-1 Air Force test facility. The simulation effort herein is an extension of the validated, CFD driven, single-injector design approach applied to single injectors which will be part of a larger engine array. Time-accurate, Three-Dimensional, CFD simulations were performed for five different classes of injector geometries. Simulations were performed to guide the design of the injector to achieve a variety of intended performance goals. For example, two GCSC injectors were designed to achieve stable hydrodynamic behavior of the propellant circuits while providing the largest thermal margin possible within the design envelope. While another injector was designed to purposefully create a hydrodynamic instability in the fuel supply circuit as predicted by the CFD analysis. Future multi-injector analysis and testing will indicate what if any changes occur in the predicted behavior for the single-element injector when the same injector geometry is placed in a multi-element array.

Computational Fluid Dynamics Modeling of the Human Pulmonary Arteries with Experimental Validation.

PubMed

Bordones, Alifer D; Leroux, Matthew; Kheyfets, Vitaly O; Wu, Yu-An; Chen, Chia-Yuan; Finol, Ender A

2018-05-21

Pulmonary hypertension (PH) is a chronic progressive disease characterized by elevated pulmonary arterial pressure, caused by an increase in pulmonary arterial impedance. Computational fluid dynamics (CFD) can be used to identify metrics representative of the stage of PH disease. However, experimental validation of CFD models is often not pursued due to the geometric complexity of the model or uncertainties in the reproduction of the required flow conditions. The goal of this work is to validate experimentally a CFD model of a pulmonary artery phantom using a particle image velocimetry (PIV) technique. Rapid prototyping was used for the construction of the patient-specific pulmonary geometry, derived from chest computed tomography angiography images. CFD simulations were performed with the pulmonary model with a Reynolds number matching those of the experiments. Flow rates, the velocity field, and shear stress distributions obtained with the CFD simulations were compared to their counterparts from the PIV flow visualization experiments. Computationally predicted flow rates were within 1% of the experimental measurements for three of the four branches of the CFD model. The mean velocities in four transversal planes of study were within 5.9 to 13.1% of the experimental mean velocities. Shear stresses were qualitatively similar between the two methods with some discrepancies in the regions of high velocity gradients. The fluid flow differences between the CFD model and the PIV phantom are attributed to experimental inaccuracies and the relative compliance of the phantom. This comparative analysis yielded valuable information on the accuracy of CFD predicted hemodynamics in pulmonary circulation models.

Model Reduction of Computational Aerothermodynamics for Multi-Discipline Analysis in High Speed Flows

NASA Astrophysics Data System (ADS)

Crowell, Andrew Rippetoe

This dissertation describes model reduction techniques for the computation of aerodynamic heat flux and pressure loads for multi-disciplinary analysis of hypersonic vehicles. NASA and the Department of Defense have expressed renewed interest in the development of responsive, reusable hypersonic cruise vehicles capable of sustained high-speed flight and access to space. However, an extensive set of technical challenges have obstructed the development of such vehicles. These technical challenges are partially due to both the inability to accurately test scaled vehicles in wind tunnels and to the time intensive nature of high-fidelity computational modeling, particularly for the fluid using Computational Fluid Dynamics (CFD). The aim of this dissertation is to develop efficient and accurate models for the aerodynamic heat flux and pressure loads to replace the need for computationally expensive, high-fidelity CFD during coupled analysis. Furthermore, aerodynamic heating and pressure loads are systematically evaluated for a number of different operating conditions, including: simple two-dimensional flow over flat surfaces up to three-dimensional flows over deformed surfaces with shock-shock interaction and shock-boundary layer interaction. An additional focus of this dissertation is on the implementation and computation of results using the developed aerodynamic heating and pressure models in complex fluid-thermal-structural simulations. Model reduction is achieved using a two-pronged approach. One prong focuses on developing analytical corrections to isothermal, steady-state CFD flow solutions in order to capture flow effects associated with transient spatially-varying surface temperatures and surface pressures (e.g., surface deformation, surface vibration, shock impingements, etc.). The second prong is focused on minimizing the computational expense of computing the steady-state CFD solutions by developing an efficient surrogate CFD model. The developed two-pronged approach is found to exhibit balanced performance in terms of accuracy and computational expense, relative to several existing approaches. This approach enables CFD-based loads to be implemented into long duration fluid-thermal-structural simulations.

Numerical Simulation of Flow in a Whirling Annular Seal and Comparison with Experiments

NASA Technical Reports Server (NTRS)

Athavale, M. M.; Hendricks, R. C.; Steinetz, B. M.

1995-01-01

The turbulent flow field in a simulated annular seal with a large clearance/radius ratio (0.015) and a whirling rotor was simulated using an advanced 3D CFD code SCISEAL. A circular whirl orbit with synchronous whirl was imposed on the rotor center. The flow field was rendered quasi-steady by making a transformation to a totaling frame. Standard k-epsilon model with wall functions was used to treat the turbulence. Experimentally measured values of flow parameters were used to specify the seal inlet and exit boundary conditions. The computed flow-field in terms of the velocity and pressure is compared with the experimental measurements inside the seal. The agreement between the numerical results and experimental data with correction is fair to good. The capability of current advanced CFD methodology to analyze this complex flow field is demonstrated. The methodology can also be extended to other whirl frequencies. Half- (or sub-) synchronous (fluid film unstable motion) and synchronous (rotor centrifugal force unbalance) whirls are the most unstable whirl modes in turbomachinery seals, and the flow code capability of simulating the flows in steady as well as whirling seals will prove to be extremely useful in the design, analyses, and performance predictions of annular as well as other types of seals.

V&V Of CFD Modeling Of The Argonne Bubble Experiment: FY15 Summary Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoyt, Nathaniel C.; Wardle, Kent E.; Bailey, James L.

2015-09-30

In support of the development of accelerator-driven production of the fission product Mo 99, computational fluid dynamics (CFD) simulations of an electron-beam irradiated, experimental-scale bubble chamber have been conducted in order to aid in interpretation of existing experimental results, provide additional insights into the physical phenomena, and develop predictive thermal hydraulic capabilities that can be applied to full-scale target solution vessels. Toward that end, a custom hybrid Eulerian-Eulerian-Lagrangian multiphase solver was developed, and simulations have been performed on high-resolution meshes. Good agreement between experiments and simulations has been achieved, especially with respect to the prediction of the maximum temperature ofmore » the uranyl sulfate solution in the experimental vessel. These positive results suggest that the simulation methodology that has been developed will prove to be suitable to assist in the development of full-scale production hardware.« less

Validation and evaluation of the advanced aeronautical CFD system SAUNA: A method developer's view

NASA Astrophysics Data System (ADS)

Shaw, J. A.; Peace, A. J.; Georgala, J. M.; Childs, P. N.

1993-09-01

This paper is concerned with a detailed validation and evaluation of the SAUNA CFD system for complex aircraft configurations. The methodology of the complete system is described in brief, including its unique use of differing grid generation strategies (structured, unstructured or both) depending on the geometric complexity of the configuration. A wide range of configurations and flow conditions are chosen in the validation and evaluation exercise to demonstrate the scope of SAUNA. A detailed description of the results from the method is preceded by a discussion on the philosophy behind the strategy followed in the exercise, in terms of equality assessment and the differing roles of the code developer and the code user. It is considered that SAUNA has grown into a highly usable tool for the aircraft designer, in combining flexibility and accuracy in an efficient manner.

Validation of High-Fidelity CFD Simulations for Rocket Injector Design

NASA Technical Reports Server (NTRS)

Tucker, P. Kevin; Menon, Suresh; Merkle, Charles L.; Oefelein, Joseph C.; Yang, Vigor

2008-01-01

Computational fluid dynamics (CFD) has the potential to improve the historical rocket injector design process by evaluating the sensitivity of performance and injector-driven thermal environments to the details of the injector geometry and key operational parameters. Methodical verification and validation efforts on a range of coaxial injector elements have shown the current production CFD capability must be improved in order to quantitatively impact the injector design process. This paper documents the status of a focused effort to compare and understand the predictive capabilities and computational requirements of a range of CFD methodologies on a set of single element injector model problems. The steady Reynolds-Average Navier-Stokes (RANS), unsteady Reynolds-Average Navier-Stokes (URANS) and three different approaches using the Large Eddy Simulation (LES) technique were used to simulate the initial model problem, a single element coaxial injector using gaseous oxygen and gaseous hydrogen propellants. While one high-fidelity LES result matches the experimental combustion chamber wall heat flux very well, there is no monotonic convergence to the data with increasing computational tool fidelity. Systematic evaluation of key flow field regions such as the flame zone, the head end recirculation zone and the downstream near wall zone has shed significant, though as of yet incomplete, light on the complex, underlying causes for the performance level of each technique. 1 Aerospace Engineer and Combustion CFD Team Leader, MS ER42, NASA MSFC, AL 35812, Senior Member, AIAA. 2 Professor and Director, Computational Combustion Laboratory, School of Aerospace Engineering, 270 Ferst Dr., Atlanta, GA 30332, Associate Fellow, AIAA. 3 Reilly Professor of Engineering, School of Mechanical Engineering, 585 Purdue Mall, West Lafayette, IN 47907, Fellow, AIAA. 4 Principal Member of Technical Staff, Combustion Research Facility, 7011 East Avenue, MS9051, Livermore, CA 94550, Associate Fellow, AIAA. 5 J. L. and G. H. McCain Endowed Chair, Mechanical Engineering, 104 Research Building East, University Park, PA 16802, Fellow, AIAA. American Institute of Aeronautics and Astronautics 1

A Novel Multi-Scale Domain Overlapping CFD/STH Coupling Methodology for Multi-Dimensional Flows Relevant to Nuclear Applications

NASA Astrophysics Data System (ADS)

Grunloh, Timothy P.

The objective of this dissertation is to develop a 3-D domain-overlapping coupling method that leverages the superior flow field resolution of the Computational Fluid Dynamics (CFD) code STAR-CCM+ and the fast execution of the System Thermal Hydraulic (STH) code TRACE to efficiently and accurately model thermal hydraulic transport properties in nuclear power plants under complex conditions of regulatory and economic importance. The primary contribution is the novel Stabilized Inertial Domain Overlapping (SIDO) coupling method, which allows for on-the-fly correction of TRACE solutions for local pressures and velocity profiles inside multi-dimensional regions based on the results of the CFD simulation. The method is found to outperform the more frequently-used domain decomposition coupling methods. An STH code such as TRACE is designed to simulate large, diverse component networks, requiring simplifications to the fluid flow equations for reasonable execution times. Empirical correlations are therefore required for many sub-grid processes. The coarse grids used by TRACE diminish sensitivity to small scale geometric details such as Reactor Pressure Vessel (RPV) internals. A CFD code such as STAR-CCM+ uses much finer computational meshes that are sensitive to the geometric details of reactor internals. In turbulent flows, it is infeasible to fully resolve the flow solution, but the correlations used to model turbulence are at a low level. The CFD code can therefore resolve smaller scale flow processes. The development of a 3-D coupling method was carried out with the intention of improving predictive capabilities of transport properties in the downcomer and lower plenum regions of an RPV in reactor safety calculations. These regions are responsible for the multi-dimensional mixing effects that determine the distribution at the core inlet of quantities with reactivity implications, such as fluid temperature and dissolved neutron absorber concentration.

Development of a Robust and Efficient Parallel Solver for Unsteady Turbomachinery Flows

NASA Technical Reports Server (NTRS)

West, Jeff; Wright, Jeffrey; Thakur, Siddharth; Luke, Ed; Grinstead, Nathan

2012-01-01

The traditional design and analysis practice for advanced propulsion systems relies heavily on expensive full-scale prototype development and testing. Over the past decade, use of high-fidelity analysis and design tools such as CFD early in the product development cycle has been identified as one way to alleviate testing costs and to develop these devices better, faster and cheaper. In the design of advanced propulsion systems, CFD plays a major role in defining the required performance over the entire flight regime, as well as in testing the sensitivity of the design to the different modes of operation. Increased emphasis is being placed on developing and applying CFD models to simulate the flow field environments and performance of advanced propulsion systems. This necessitates the development of next generation computational tools which can be used effectively and reliably in a design environment. The turbomachinery simulation capability presented here is being developed in a computational tool called Loci-STREAM [1]. It integrates proven numerical methods for generalized grids and state-of-the-art physical models in a novel rule-based programming framework called Loci [2] which allows: (a) seamless integration of multidisciplinary physics in a unified manner, and (b) automatic handling of massively parallel computing. The objective is to be able to routinely simulate problems involving complex geometries requiring large unstructured grids and complex multidisciplinary physics. An immediate application of interest is simulation of unsteady flows in rocket turbopumps, particularly in cryogenic liquid rocket engines. The key components of the overall methodology presented in this paper are the following: (a) high fidelity unsteady simulation capability based on Detached Eddy Simulation (DES) in conjunction with second-order temporal discretization, (b) compliance with Geometric Conservation Law (GCL) in order to maintain conservative property on moving meshes for second-order time-stepping scheme, (c) a novel cloud-of-points interpolation method (based on a fast parallel kd-tree search algorithm) for interfaces between turbomachinery components in relative motion which is demonstrated to be highly scalable, and (d) demonstrated accuracy and parallel scalability on large grids (approx 250 million cells) in full turbomachinery geometries.

CFD analysis of linear compressors considering load conditions

NASA Astrophysics Data System (ADS)

Bae, Sanghyun; Oh, Wonsik

2017-08-01

This paper is a study on computational fluid dynamics (CFD) analysis of linear compressor considering load conditions. In the conventional CFD analysis of the linear compressor, the load condition was not considered in the behaviour of the piston. In some papers, behaviour of piston is assumed as sinusoidal motion provided by user defined function (UDF). In the reciprocating type compressor, the stroke of the piston is restrained by the rod, while the stroke of the linear compressor is not restrained, and the stroke changes depending on the load condition. The greater the pressure difference between the discharge refrigerant and the suction refrigerant, the more the centre point of the stroke is pushed backward. And the behaviour of the piston is not a complete sine wave. For this reason, when the load condition changes in the CFD analysis of the linear compressor, it may happen that the ANSYS code is changed or unfortunately the modelling is changed. In addition, a separate analysis or calculation is required to find a stroke that meets the load condition, which may contain errors. In this study, the coupled mechanical equations and electrical equations are solved using the UDF, and the behaviour of the piston is solved considering the pressure difference across the piston. Using the above method, the stroke of the piston with respect to the motor specification of the analytical model can be calculated according to the input voltage, and the piston behaviour can be realized considering the thrust amount due to the pressure difference.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Q.; Kraus, A.; Hu, R.

CFD analysis has been focused on important component-level phenomena using STARCCM+ to supplement the system analysis of integral system behavior. A notable area of interest was the cavity region. This area is of particular interest for CFD analysis due to the multi-dimensional flow and complex heat transfer (thermal radiation heat transfer and natural convection), which are not simulated directly by RELAP5. CFD simulations allow for the estimation of the boundary heat flux distribution along the riser tubes, which is needed in the RELAP5 simulations. The CFD results can also provide additional data to help establish what level of modeling detailmore » is necessary in RELAP5. It was found that the flow profiles in the cavity region are simpler for the water-based concept than for the air-cooled concept. The local heat flux noticeably increases axially, and is higher in the fins than in the riser tubes. These results were utilized in RELAP5 simulations as boundary conditions, to provide better temperature predictions in the system level analyses. It was also determined that temperatures were higher in the fins than the riser tubes, but within design limits for thermal stresses. Higher temperature predictions were identified in the edge fins, in part due to additional thermal radiation from the side cavity walls.« less

Controls/CFD Interdisciplinary Research Software Generates Low-Order Linear Models for Control Design From Steady-State CFD Results

NASA Technical Reports Server (NTRS)

Melcher, Kevin J.

1997-01-01

The NASA Lewis Research Center is developing analytical methods and software tools to create a bridge between the controls and computational fluid dynamics (CFD) disciplines. Traditionally, control design engineers have used coarse nonlinear simulations to generate information for the design of new propulsion system controls. However, such traditional methods are not adequate for modeling the propulsion systems of complex, high-speed vehicles like the High Speed Civil Transport. To properly model the relevant flow physics of high-speed propulsion systems, one must use simulations based on CFD methods. Such CFD simulations have become useful tools for engineers that are designing propulsion system components. The analysis techniques and software being developed as part of this effort are an attempt to evolve CFD into a useful tool for control design as well. One major aspect of this research is the generation of linear models from steady-state CFD results. CFD simulations, often used during the design of high-speed inlets, yield high resolution operating point data. Under a NASA grant, the University of Akron has developed analytical techniques and software tools that use these data to generate linear models for control design. The resulting linear models have the same number of states as the original CFD simulation, so they are still very large and computationally cumbersome. Model reduction techniques have been successfully applied to reduce these large linear models by several orders of magnitude without significantly changing the dynamic response. The result is an accurate, easy to use, low-order linear model that takes less time to generate than those generated by traditional means. The development of methods for generating low-order linear models from steady-state CFD is most complete at the one-dimensional level, where software is available to generate models with different kinds of input and output variables. One-dimensional methods have been extended somewhat so that linear models can also be generated from two- and three-dimensional steady-state results. Standard techniques are adequate for reducing the order of one-dimensional CFD-based linear models. However, reduction of linear models based on two- and three-dimensional CFD results is complicated by very sparse, ill-conditioned matrices. Some novel approaches are being investigated to solve this problem.

Coarse Grid CFD for underresolved simulation

NASA Astrophysics Data System (ADS)

Class, Andreas G.; Viellieber, Mathias O.; Himmel, Steffen R.

2010-11-01

CFD simulation of the complete reactor core of a nuclear power plant requires exceedingly huge computational resources so that this crude power approach has not been pursued yet. The traditional approach is 1D subchannel analysis employing calibrated transport models. Coarse grid CFD is an attractive alternative technique based on strongly under-resolved CFD and the inviscid Euler equations. Obviously, using inviscid equations and coarse grids does not resolve all the physics requiring additional volumetric source terms modelling viscosity and other sub-grid effects. The source terms are implemented via correlations derived from fully resolved representative simulations which can be tabulated or computed on the fly. The technique is demonstrated for a Carnot diffusor and a wire-wrap fuel assembly [1]. [4pt] [1] Himmel, S.R. phd thesis, Stuttgart University, Germany 2009, http://bibliothek.fzk.de/zb/berichte/FZKA7468.pdf

Capturing Pressure Oscillations in Numerical Simulations of Internal Combustion Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubba, Sreenivasa Rao; Jupudi, Ravichandra S.; Pasunurthi, Shyam Sundar

In an earlier publication, the authors compared numerical predictions of the mean cylinder pressure of diesel and dual-fuel combustion, to that of measured pressure data from a medium-speed, large-bore engine. In these earlier comparisons, measured data from a flush-mounted in-cylinder pressure transducer showed notable and repeatable pressure oscillations which were not evident in the mean cylinder pressure predictions from computational fluid dynamics (CFD). In this paper, the authors present a methodology for predicting and reporting the local cylinder pressure consistent with that of a measurement location. Such predictions for large-bore, medium-speed engine operation demonstrate pressure oscillations in accordance with thosemore » measured. The temporal occurrences of notable pressure oscillations were during the start of combustion and around the time of maximum cylinder pressure. With appropriate resolutions in time steps and mesh sizes, the local cell static pressure predicted for the transducer location showed oscillations in both diesel and dual-fuel combustion modes which agreed with those observed in the experimental data. Fast Fourier transform (FFT) analysis on both experimental and calculated pressure traces revealed that the CFD predictions successfully captured both the amplitude and frequency range of the oscillations. Furthermore, resolving propagating pressure waves with the smaller time steps and grid sizes necessary to achieve these results required a significant increase in computer resources.« less

Capturing Pressure Oscillations in Numerical Simulations of Internal Combustion Engines

DOE PAGES

Gubba, Sreenivasa Rao; Jupudi, Ravichandra S.; Pasunurthi, Shyam Sundar; ...

2018-04-09

In an earlier publication, the authors compared numerical predictions of the mean cylinder pressure of diesel and dual-fuel combustion, to that of measured pressure data from a medium-speed, large-bore engine. In these earlier comparisons, measured data from a flush-mounted in-cylinder pressure transducer showed notable and repeatable pressure oscillations which were not evident in the mean cylinder pressure predictions from computational fluid dynamics (CFD). In this paper, the authors present a methodology for predicting and reporting the local cylinder pressure consistent with that of a measurement location. Such predictions for large-bore, medium-speed engine operation demonstrate pressure oscillations in accordance with thosemore » measured. The temporal occurrences of notable pressure oscillations were during the start of combustion and around the time of maximum cylinder pressure. With appropriate resolutions in time steps and mesh sizes, the local cell static pressure predicted for the transducer location showed oscillations in both diesel and dual-fuel combustion modes which agreed with those observed in the experimental data. Fast Fourier transform (FFT) analysis on both experimental and calculated pressure traces revealed that the CFD predictions successfully captured both the amplitude and frequency range of the oscillations. Furthermore, resolving propagating pressure waves with the smaller time steps and grid sizes necessary to achieve these results required a significant increase in computer resources.« less

Towards high fidelity numerical wave tanks for modelling coastal and ocean engineering processes

NASA Astrophysics Data System (ADS)

Cozzuto, G.; Dimakopoulos, A.; de Lataillade, T.; Kees, C. E.

2017-12-01

With the increasing availability of computational resources, the engineering and research community is gradually moving towards using high fidelity Comutational Fluid Mechanics (CFD) models to perform numerical tests for improving the understanding of physical processes pertaining to wave propapagation and interaction with the coastal environment and morphology, either physical or man-made. It is therefore important to be able to reproduce in these models the conditions that drive these processes. So far, in CFD models the norm is to use regular (linear or nonlinear) waves for performing numerical tests, however, only random waves exist in nature. In this work, we will initially present the verification and validation of numerical wave tanks based on Proteus, an open-soruce computational toolkit based on finite element analysis, with respect to the generation, propagation and absorption of random sea states comprising of long non-repeating wave sequences. Statistical and spectral processing of results demonstrate that the methodologies employed (including relaxation zone methods and moving wave paddles) are capable of producing results of similar quality to the wave tanks used in laboratories (Figure 1). Subsequently cases studies of modelling complex process relevant to coastal defences and floating structures such as sliding and overturning of composite breakwaters, heave and roll response of floating caissons are presented. Figure 1: Wave spectra in the numerical wave tank (coloured symbols), compared against the JONSWAP distribution

Effectiveness of two conventional methods for seismic retrofit of steel and RC moment resisting frames based on damage control criteria

NASA Astrophysics Data System (ADS)

Beheshti Aval, Seyed Bahram; Kouhestani, Hamed Sadegh; Mottaghi, Lida

2017-07-01

This study investigates the efficiency of two types of rehabilitation methods based on economic justification that can lead to logical decision making between the retrofitting schemes. Among various rehabilitation methods, concentric chevron bracing (CCB) and cylindrical friction damper (CFD) were selected. The performance assessment procedure of the frames is divided into two distinct phases. First, the limit state probabilities of the structures before and after rehabilitation are investigated. In the second phase, the seismic risk of structures in terms of life safety and financial losses (decision variables) using the recently published FEMA P58 methodology is evaluated. The results show that the proposed retrofitting methods improve the serviceability and life safety performance levels of steel and RC structures at different rates when subjected to earthquake loads. Moreover, these procedures reveal that financial losses are greatly decreased, and were more tangible by the application of CFD rather than using CCB. Although using both retrofitting methods reduced damage state probabilities, incorporation of a site-specific seismic hazard curve to evaluate mean annual occurrence frequency at the collapse prevention limit state caused unexpected results to be obtained. Contrary to CFD, the collapse probability of the structures retrofitted with CCB increased when compared with the primary structures.

Recent developments of axial flow compressors under transonic flow conditions

NASA Astrophysics Data System (ADS)

Srinivas, G.; Raghunandana, K.; Satish Shenoy, B.

2017-05-01

The objective of this paper is to give a holistic view of the most advanced technology and procedures that are practiced in the field of turbomachinery design. Compressor flow solver is the turbulence model used in the CFD to solve viscous problems. The popular techniques like Jameson’s rotated difference scheme was used to solve potential flow equation in transonic condition for two dimensional aero foils and later three dimensional wings. The gradient base method is also a popular method especially for compressor blade shape optimization. Various other types of optimization techniques available are Evolutionary algorithms (EAs) and Response surface methodology (RSM). It is observed that in order to improve compressor flow solver and to get agreeable results careful attention need to be paid towards viscous relations, grid resolution, turbulent modeling and artificial viscosity, in CFD. The advanced techniques like Jameson’s rotated difference had most substantial impact on wing design and aero foil. For compressor blade shape optimization, Evolutionary algorithm is quite simple than gradient based technique because it can solve the parameters simultaneously by searching from multiple points in the given design space. Response surface methodology (RSM) is a method basically used to design empirical models of the response that were observed and to study systematically the experimental data. This methodology analyses the correct relationship between expected responses (output) and design variables (input). RSM solves the function systematically in a series of mathematical and statistical processes. For turbomachinery blade optimization recently RSM has been implemented successfully. The well-designed high performance axial flow compressors finds its application in any air-breathing jet engines.

CFD Analysis of the Anti-Surge Effects by Water Hammering

NASA Astrophysics Data System (ADS)

Kim, Tae-oh; Jeong, Hyo-min; Chung, Han-shik; Lee, Sin-il; Lee, Kwang-sung

2015-09-01

Water hammering occurs due to the surge effect that comes from operating the pump, sudden stop during the operating due to a blackout and rapid open and close of the valve. By the water hammering of the pipeline and the pump, the valve are damaged. In this paper, transient analysis is conducted by CFD (Computational Fluid Dynamics). The purpose of this paper is to provide the research data about the change of the pressure and flow in the pipe that caused by the water hammering.

CFD Vision 2030 Study: A Path to Revolutionary Computational Aerosciences

NASA Technical Reports Server (NTRS)

Slotnick, Jeffrey; Khodadoust, Abdollah; Alonso, Juan; Darmofal, David; Gropp, William; Lurie, Elizabeth; Mavriplis, Dimitri

2014-01-01

This report documents the results of a study to address the long range, strategic planning required by NASA's Revolutionary Computational Aerosciences (RCA) program in the area of computational fluid dynamics (CFD), including future software and hardware requirements for High Performance Computing (HPC). Specifically, the "Vision 2030" CFD study is to provide a knowledge-based forecast of the future computational capabilities required for turbulent, transitional, and reacting flow simulations across a broad Mach number regime, and to lay the foundation for the development of a future framework and/or environment where physics-based, accurate predictions of complex turbulent flows, including flow separation, can be accomplished routinely and efficiently in cooperation with other physics-based simulations to enable multi-physics analysis and design. Specific technical requirements from the aerospace industrial and scientific communities were obtained to determine critical capability gaps, anticipated technical challenges, and impediments to achieving the target CFD capability in 2030. A preliminary development plan and roadmap were created to help focus investments in technology development to help achieve the CFD vision in 2030.

Reducing numerical costs for core wide nuclear reactor CFD simulations by the Coarse-Grid-CFD

NASA Astrophysics Data System (ADS)

Viellieber, Mathias; Class, Andreas G.

2013-11-01

Traditionally complete nuclear reactor core simulations are performed with subchannel analysis codes, that rely on experimental and empirical input. The Coarse-Grid-CFD (CGCFD) intends to replace the experimental or empirical input with CFD data. The reactor core consists of repetitive flow patterns, allowing the general approach of creating a parametrized model for one segment and composing many of those to obtain the entire reactor simulation. The method is based on a detailed and well-resolved CFD simulation of one representative segment. From this simulation we extract so-called parametrized volumetric forces which close, an otherwise strongly under resolved, coarsely-meshed model of a complete reactor setup. While the formulation so far accounts for forces created internally in the fluid others e.g. obstruction and flow deviation through spacers and wire wraps, still need to be accounted for if the geometric details are not represented in the coarse mesh. These are modelled with an Anisotropic Porosity Formulation (APF). This work focuses on the application of the CGCFD to a complete reactor core setup and the accomplishment of the parametrization of the volumetric forces.

CFD Variability for a Civil Transport Aircraft Near Buffet-Onset Conditions

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L.; Morrison, Joseph H.; Biedron, Robert T.

2003-01-01

A CFD sensitivity analysis is conducted for an aircraft at several conditions, including flow with substantial separation (buffet onset). The sensitivity is studied using two different Navier-Stokes computer codes, three different turbulence models, and two different grid treatments of the wing trailing edge. This effort is a follow-on to an earlier study of CFD variation over a different aircraft in buffet onset conditions. Similar to the earlier study, the turbulence model is found to have the largest effect, with a variation of 3.8% in lift at the buffet onset angle of attack. Drag and moment variation are 2.9% and 23.6%, respectively. The variations due to code and trailing edge cap grid are smaller than that due to turbulence model. Overall, the combined approximate error band in CFD due to code, turbulence model, and trailing edge treatment at the buffet onset angle of attack are: 4% in lift, 3% in drag, and 31% in moment. The CFD results show similar trends to flight test data, but also exhibit a lift curve break not seen in the data.

Grid Resolution Study over Operability Space for a Mach 1.7 Low Boom External Compression Inlet

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.

2014-01-01

This paper presents a statistical methodology whereby the probability limits associated with CFD grid resolution of inlet flow analysis can be determined which provide quantitative information on the distribution of that error over the specified operability range. The objectives of this investigation is to quantify the effects of both random (accuracy) and systemic (biasing) errors associated with grid resolution in the analysis of the Lockheed Martin Company (LMCO) N+2 Low Boom external compression supersonic inlet. The study covers the entire operability space as defined previously by the High Speed Civil Transport (HSCT) High Speed Research (HSR) program goals. The probability limits in terms of a 95.0% confidence interval on the analysis data were evaluated for four ARP1420 inlet metrics, namely (1) total pressure recovery (PFAIP), (2) radial hub distortion (DPH/P), (3) ) radial tip distortion (DPT/P), and (4) ) circumferential distortion (DPC/P). In general, the resulting +/-0.95 delta Y interval was unacceptably large in comparison to the stated goals of the HSCT program. Therefore, the conclusion was reached that the "standard grid" size was insufficient for this type of analysis. However, in examining the statistical data, it was determined that the CFD analysis results at the outer fringes of the operability space were the determining factor in the measure of statistical uncertainty. Adequate grids are grids that are free of biasing (systemic) errors and exhibit low random (precision) errors in comparison to their operability goals. In order to be 100% certain that the operability goals have indeed been achieved for each of the inlet metrics, the Y+/-0.95 delta Y limit must fall inside the stated operability goals. For example, if the operability goal for DPC/P circumferential distortion is =0.06, then the forecast Y for DPC/P plus the 95% confidence interval on DPC/P, i.e. +/-0.95 delta Y, must all be less than or equal to 0.06.

CFD simulation and experimental validation of a GM type double inlet pulse tube refrigerator

NASA Astrophysics Data System (ADS)

Banjare, Y. P.; Sahoo, R. K.; Sarangi, S. K.

2010-04-01

Pulse tube refrigerator has the advantages of long life and low vibration over the conventional cryocoolers, such as GM and stirling coolers because of the absence of moving parts in low temperature. This paper performs a three-dimensional computational fluid dynamic (CFD) simulation of a GM type double inlet pulse tube refrigerator (DIPTR) vertically aligned, operating under a variety of thermal boundary conditions. A commercial computational fluid dynamics (CFD) software package, Fluent 6.1 is used to model the oscillating flow inside a pulse tube refrigerator. The simulation represents fully coupled systems operating in steady-periodic mode. The externally imposed boundary conditions are sinusoidal pressure inlet by user defined function at one end of the tube and constant temperature or heat flux boundaries at the external walls of the cold-end heat exchangers. The experimental method to evaluate the optimum parameters of DIPTR is difficult. On the other hand, developing a computer code for CFD analysis is equally complex. The objectives of the present investigations are to ascertain the suitability of CFD based commercial package, Fluent for study of energy and fluid flow in DIPTR and to validate the CFD simulation results with available experimental data. The general results, such as the cool down behaviours of the system, phase relation between mass flow rate and pressure at cold end, the temperature profile along the wall of the cooler and refrigeration load are presented for different boundary conditions of the system. The results confirm that CFD based Fluent simulations are capable of elucidating complex periodic processes in DIPTR. The results also show that there is an excellent agreement between CFD simulation results and experimental results.

Development and Validation of Methodology to Model Flow in Ventilation Systems Commonly Found in Nuclear Facilities. Phase I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strons, Philip; Bailey, James L.; Davis, John

2016-03-01

In this work, we apply the CFD in modeling airflow and particulate transport. This modeling is then compared to field validation studies to both inform and validate the modeling assumptions. Based on the results of field tests, modeling assumptions and boundary conditions are refined and the process is repeated until the results are found to be reliable with a high level of confidence.

CFD Modeling and Simulation of Aeorodynamic Cooling of Automotive Brake Rotor

NASA Astrophysics Data System (ADS)

Belhocien, Ali; Omar, Wan Zaidi Wan

Braking system is one of the important control systems of an automotive. For many years, the disc brakes have been used in automobiles for the safe retarding of the vehicles. During the braking enormous amount of heat will be generated and for effective braking sufficient heat dissipation is essential. The thermal performance of disc brake depends upon the characteristics of the airflow around the brake rotor and hence the aerodynamics is an important in the region of brake components. A CFD analysis is carried out on the braking system as a case study to make out the behavior of airflow distribution around the disc brake components using ANSYS CFX software. We are interested in the determination of the heat transfer coefficient (HTC) on each surface of a ventilated disc rotor varying with time in a transient state using CFD analysis, and then imported the surface film condition data into a corresponding FEM model for disc temperature analysis.

Analysis of a hypersonic waverider research vehicle with a hydrocarbon scramjet engine

NASA Technical Reports Server (NTRS)

Molvik, Gregory A.; Bowles, Jeffrey V.; Huynh, Loc C.

1993-01-01

The results of a feasibility study of a hypersonic waverider research vehicle with a hydrocarbon scramjet engine are presented. The integrated waverider/scramjet geometry is first optimized with a vehicle synthesis code to produce a maximum product of the lift-to-drag ratio and the cycle specific impulse, hence cruise range. Computational fluid dynamics (CFD) is then employed to provide a nose-to-tail analysis of the system at the on-design conditions. Some differences are noted between the results of the two analysis techniques. A comparison of experimental, engineering analysis and CFD results on a waverider forebody are also included for validation.

An Experimental and CFD Study of a Supersonic Coaxial Jet

NASA Technical Reports Server (NTRS)

Cutler, A. D.; White, J. A.

2001-01-01

A supersonic coaxial jet facility is designed and experimental data are acquired suitable for the validation of CFD codes employed in the analysis of high-speed air-breathing engines. The center jet is of a light gas, the coflow jet is of air, and the mixing layer between them is compressible. The jet flow field is characterized using schlieren imaging, surveys with pitot, total temperature and gas sampling probes, and RELIEF velocimetry. VULCAN, a structured grid CFD code, is used to solve for the nozzle and jet flow, and the results are compared to the experiment for several variations of the kappa - omega turbulence model

An introduction to chaos theory in CFD

NASA Technical Reports Server (NTRS)

Pulliam, Thomas H.

1990-01-01

The popular subject 'chaos theory' has captured the imagination of a wide variety of scientists and engineers. CFD has always been faced with nonlinear systems and it is natural to assume that nonlinear dynamics will play a role at sometime in such work. This paper will attempt to introduce some of the concepts and analysis procedures associated with nonlinear dynamics theory. In particular, results from computations of an airfoil at high angle of attack which exhibits a sequence of bifurcations for single frequency unsteady shedding through period doublings cascading into low dimensional chaos are used to present and demonstrate various aspects of nonlinear dynamics in CFD.

FDNS CFD Code Benchmark for RBCC Ejector Mode Operation

NASA Technical Reports Server (NTRS)

Holt, James B.; Ruf, Joe

1999-01-01

Computational Fluid Dynamics (CFD) analysis results are compared with benchmark quality test data from the Propulsion Engineering Research Center's (PERC) Rocket Based Combined Cycle (RBCC) experiments to verify fluid dynamic code and application procedures. RBCC engine flowpath development will rely on CFD applications to capture the multi-dimensional fluid dynamic interactions and to quantify their effect on the RBCC system performance. Therefore, the accuracy of these CFD codes must be determined through detailed comparisons with test data. The PERC experiments build upon the well-known 1968 rocket-ejector experiments of Odegaard and Stroup by employing advanced optical and laser based diagnostics to evaluate mixing and secondary combustion. The Finite Difference Navier Stokes (FDNS) code was used to model the fluid dynamics of the PERC RBCC ejector mode configuration. Analyses were performed for both Diffusion and Afterburning (DAB) and Simultaneous Mixing and Combustion (SMC) test conditions. Results from both the 2D and the 3D models are presented.

The Phoretic Motion Experiment (PME) definition phase

NASA Technical Reports Server (NTRS)

Eaton, L. R.; Neste, S. L. (Editor)

1982-01-01

The aerosol generator and the charge flow devices (CFD) chamber which were designed for zero-gravity operation was analyzed. Characteristics of the CFD chamber and aerosol generator which would be useful for cloud physics experimentation in a one-g as well as a zero-g environment are documented. The Collision type of aerosol generator is addressed. Relationships among the various input and output parameters are derived and subsequently used to determine the requirements on the controls of the input parameters to assure a given error budget of an output parameter. The CFD chamber operation in a zero-g environment is assessed utilizing a computer simulation program. Low nuclei critical supersaturation and high experiment accuracies are emphasized which lead to droplet growth times extending into hundreds of seconds. The analysis was extended to assess the performance constraints of the CFD chamber in a one-g environment operating in the horizontal mode.

CFD Analysis of Evaporation-Condensation Phenomenon In an Evaporation Chamber of Natural Vacuum Solar Desalination

NASA Astrophysics Data System (ADS)

Ambarita, H.; Ronowikarto, A. D.; Siregar, R. E. T.; Setyawan, E. Y.

2018-01-01

Desalination technologies is one of solutions for water scarcity. With using renewable energy, like solar energy, wind energy, and geothermal energy, expected will reduce the energy demand. This required study on the modeling and transport parameters determination of natural vacuum solar desalination by using computational fluid dynamics (CFD) method to simulate the model. A three-dimensional case, two-phase model was developed for evaporation-condensation phenomenon in natural vacuum solar desalination. The CFD simulation results were compared with the avalaible experimental data. The simulation results shows inthat there is a phenomenon of evaporation-condensation in an evaporation chamber. From the simulation, the fresh water productivity is 2.21 litre, and from the experimental is 2.1 litre. This study shows there’s an error of magnitude 0.4%. The CFD results also show that, vacuum pressure will degrade the saturation temperature of sea water.

Comparative and Combinative Study of Urban Heat island in Wuhan City with Remote Sensing and CFD Simulation

PubMed Central

Li, Kun; Yu, Zhuang

2008-01-01

Urban heat islands are one of the most critical urban environment heat problems. Landsat ETM+ satellite data were used to investigate the land surface temperature and underlying surface indices such as NDVI and NDBI. A comparative study of the urban heat environment at different scales, times and locations was done to verify the heat island characteristics. Since remote sensing technology has limitations for dynamic flow analysis in the study of urban spaces, a CFD simulation was used to validate the improvement of the heat environment in a city by means of wind. CFD technology has its own shortcomings in parameter setting and verification, while RS technology is helpful to remedy this. The city of Wuhan and its climatological condition of being hot in summer and cold in winter were chosen to verify the comparative and combinative application of RS with CFD in studying the urban heat island. PMID:27873893

CFD Analysis for Assessing the Effect of Wind on the Thermal Control of the Mars Science Laboratory Curiosity Rover

NASA Technical Reports Server (NTRS)

Bhandari, Pradeep; Anderson, Kevin

2013-01-01

The challenging range of landing sites for which the Mars Science Laboratory Rover was designed, requires a rover thermal management system that is capable of keeping temperatures controlled across a wide variety of environmental conditions. On the Martian surface where temperatures can be as cold as -123 C and as warm as 38 C, the rover relies upon a Mechanically Pumped Fluid Loop (MPFL) Rover Heat Rejection System (RHRS) and external radiators to maintain the temperature of sensitive electronics and science instruments within a -40 C to 50 C range. The RHRS harnesses some of the waste heat generated from the rover power source, known as the Multi Mission Radioisotope Thermoelectric Generator (MMRTG), for use as survival heat for the rover during cold conditions. The MMRTG produces 110 W of electrical power while generating waste heat equivalent to approximately 2000 W. Heat exchanger plates (hot plates) positioned close to the MMRTG pick up this survival heat from it by radiative heat transfer. Winds on Mars can be as fast as 15 m/s for extended periods. They can lead to significant heat loss from the MMRTG and the hot plates due to convective heat pick up from these surfaces. Estimation of this convective heat loss cannot be accurately and adequately achieved by simple textbook based calculations because of the very complicated flow fields around these surfaces, which are a function of wind direction and speed. Accurate calculations necessitated the employment of sophisticated Computational Fluid Dynamics (CFD) computer codes. This paper describes the methodology and results of these CFD calculations. Additionally, these results are compared to simple textbook based calculations that served as benchmarks and sanity checks for them. And finally, the overall RHRS system performance predictions will be shared to show how these results affected the overall rover thermal performance.

Methodologies for extracting kinetic constants for multiphase reacting flow simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, S.L.; Lottes, S.A.; Golchert, B.

1997-03-01

Flows in industrial reactors often involve complex reactions of many species. A computational fluid dynamics (CFD) computer code, ICRKFLO, was developed to simulate multiphase, multi-species reacting flows. The ICRKFLO uses a hybrid technique to calculate species concentration and reaction for a large number of species in a reacting flow. This technique includes a hydrodynamic and reacting flow simulation with a small but sufficient number of lumped reactions to compute flow field properties followed by a calculation of local reaction kinetics and transport of many subspecies (order of 10 to 100). Kinetic rate constants of the numerous subspecies chemical reactions aremore » difficult to determine. A methodology has been developed to extract kinetic constants from experimental data efficiently. A flow simulation of a fluid catalytic cracking (FCC) riser was successfully used to demonstrate this methodology.« less

Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

NASA Technical Reports Server (NTRS)

Groves, Curtis; Ilie, Marcel; Schallhorn, Paul

2014-01-01

Spacecraft components may be damaged due to airflow produced by Environmental Control Systems (ECS). There are uncertainties and errors associated with using Computational Fluid Dynamics (CFD) to predict the flow field around a spacecraft from the ECS System. This paper describes an approach to estimate the uncertainty in using CFD to predict the airflow speeds around an encapsulated spacecraft.

Developing an Accurate CFD Based Gust Model for the Truss Braced Wing Aircraft

NASA Technical Reports Server (NTRS)

Bartels, Robert E.

2013-01-01

The increased flexibility of long endurance aircraft having high aspect ratio wings necessitates attention to gust response and perhaps the incorporation of gust load alleviation. The design of civil transport aircraft with a strut or truss-braced high aspect ratio wing furthermore requires gust response analysis in the transonic cruise range. This requirement motivates the use of high fidelity nonlinear computational fluid dynamics (CFD) for gust response analysis. This paper presents the development of a CFD based gust model for the truss braced wing aircraft. A sharp-edged gust provides the gust system identification. The result of the system identification is several thousand time steps of instantaneous pressure coefficients over the entire vehicle. This data is filtered and downsampled to provide the snapshot data set from which a reduced order model is developed. A stochastic singular value decomposition algorithm is used to obtain a proper orthogonal decomposition (POD). The POD model is combined with a convolution integral to predict the time varying pressure coefficient distribution due to a novel gust profile. Finally the unsteady surface pressure response of the truss braced wing vehicle to a one-minus-cosine gust, simulated using the reduced order model, is compared with the full CFD.

A Parametric Study of Unsteady Rotor-Stator Interaction in a Simplified Francis Turbine

NASA Astrophysics Data System (ADS)

Wouden, Alex; Cimbala, John; Lewis, Bryan

2011-11-01

CFD analysis is becoming a critical stage in the design of hydroturbines. However, its capability to represent unsteady flow interactions between the rotor and stator (which requires a 360-degree, mesh-refined model of the turbine passage) is hindered. For CFD to become a more effective tool in predicting the performance of a hydroturbine, the key interactions between the rotor and stator need to be understood using current numerical methods. As a first step towards evaluating this unsteady behavior without the burden of a computationally expensive domain, the stator and Francis-type rotor blades are reduced to flat plates. Local and global variables are compared using periodic, semi-periodic, and 360-degree geometric models and various turbulence models (k-omega, k-epsilon, and Spalart-Allmaras). The computations take place within the OpenFOAM® environment and utilize a general grid interface (GGI) between the rotor and stator computational domains. The rotor computational domain is capable of dynamic rotation. The results demonstrate some of the strengths and limitations of utilizing CFD for hydroturbine analysis. These case studies will also serve as tutorials to help others learn how to use CFD for turbomachinery. This research is funded by a grant from the DOE.

Unsteady flow simulations around complex geometries using stationary or rotating unstructured grids

NASA Astrophysics Data System (ADS)

Sezer-Uzol, Nilay

In this research, the computational analysis of three-dimensional, unsteady, separated, vortical flows around complex geometries is studied by using stationary or moving unstructured grids. Two main engineering problems are investigated. The first problem is the unsteady simulation of a ship airwake, where helicopter operations become even more challenging, by using stationary unstructured grids. The second problem is the unsteady simulation of wind turbine rotor flow fields by using moving unstructured grids which are rotating with the whole three-dimensional rigid rotor geometry. The three dimensional, unsteady, parallel, unstructured, finite volume flow solver, PUMA2, is used for the computational fluid dynamics (CFD) simulations considered in this research. The code is modified to have a moving grid capability to perform three-dimensional, time-dependent rotor simulations. An instantaneous log-law wall model for Large Eddy Simulations is also implemented in PUMA2 to investigate the very large Reynolds number flow fields of rotating blades. To verify the code modifications, several sample test cases are also considered. In addition, interdisciplinary studies, which are aiming to provide new tools and insights to the aerospace and wind energy scientific communities, are done during this research by focusing on the coupling of ship airwake CFD simulations with the helicopter flight dynamics and control analysis, the coupling of wind turbine rotor CFD simulations with the aeroacoustic analysis, and the analysis of these time-dependent and large-scale CFD simulations with the help of a computational monitoring, steering and visualization tool, POSSE.

Application of Adjoint Methodology to Supersonic Aircraft Design Using Reversed Equivalent Areas

NASA Technical Reports Server (NTRS)

Rallabhandi, Sriram K.

2013-01-01

This paper presents an approach to shape an aircraft to equivalent area based objectives using the discrete adjoint approach. Equivalent areas can be obtained either using reversed augmented Burgers equation or direct conversion of off-body pressures into equivalent area. Formal coupling with CFD allows computation of sensitivities of equivalent area objectives with respect to aircraft shape parameters. The exactness of the adjoint sensitivities is verified against derivatives obtained using the complex step approach. This methodology has the benefit of using designer-friendly equivalent areas in the shape design of low-boom aircraft. Shape optimization results with equivalent area cost functionals are discussed and further refined using ground loudness based objectives.

Computational analysis of a multistage axial compressor

NASA Astrophysics Data System (ADS)

Mamidoju, Chaithanya

Turbomachines are used extensively in Aerospace, Power Generation, and Oil & Gas Industries. Efficiency of these machines is often an important factor and has led to the continuous effort to improve the design to achieve better efficiency. The axial flow compressor is a major component in a gas turbine with the turbine's overall performance depending strongly on compressor performance. Traditional analysis of axial compressors involves throughflow calculations, isolated blade passage analysis, Quasi-3D blade-to-blade analysis, single-stage (rotor-stator) analysis, and multi-stage analysis involving larger design cycles. In the current study, the detailed flow through a 15 stage axial compressor is analyzed using a 3-D Navier Stokes CFD solver in a parallel computing environment. Methodology is described for steady state (frozen rotor stator) analysis of one blade passage per component. Various effects such as mesh type and density, boundary conditions, tip clearance and numerical issues such as turbulence model choice, advection model choice, and parallel processing performance are analyzed. A high sensitivity of the predictions to the above was found. Physical explanation to the flow features observed in the computational study are given. The total pressure rise verses mass flow rate was computed.

First NASA/Industry High-Speed Research Configuration Aerodynamics Workshop

NASA Technical Reports Server (NTRS)

Wood, Richard M. (Editor)

1999-01-01

This publication is a compilation of documents presented at the First NASA/Industry High Speed Research Configuration Aerodynamics Workshop held on February 27-29, 1996 at NASA Langley Research Center. The purpose of the workshop was to bring together the broad spectrum of aerodynamicists, engineers, and scientists working within the Configuration Aerodynamics element of the HSR Program to collectively evaluate the technology status and to define the needs within Computational Fluid Dynamics (CFD) Analysis Methodology, Aerodynamic Shape Design, Propulsion/Airframe Integration (PAI), Aerodynamic Performance, and Stability and Control (S&C) to support the development of an economically viable High Speed Civil Transport (HSCT) aircraft. To meet these objectives, papers were presented by representative from NASA Langley, Ames, and Lewis Research Centers; Boeing, McDonnell Douglas, Northrop-Grumman, Lockheed-Martin, Vigyan, Analytical Services, Dynacs, and RIACS.

First NASA/Industry High-Speed Research Configuration Aerodynamics Workshop. Pt. 2

NASA Technical Reports Server (NTRS)

Wood, Richard M. (Editor)

1999-01-01

This publication is a compilation of documents presented at the First NASA Industry High Speed Research Configuration Aerodynamics Workshop held on February 27-29, 1996 at NASA Langley Research Center. The purpose of the workshop was to bring together the broad spectrum of aerodynamicists, engineers, and scientists working within the Configuration Aerodynamics element of the HSR Program to collectively evaluate the technology status and to define the needs within Computational Fluid Dynamics (CFD) Analysis Methodology, Aerodynamic Shape Design, Propulsion/Airframe Integration (PAI), Aerodynamic Performance, and Stability and Control (S&C) to support the development of an economically viable High Speed Civil Transport (HSCT) aircraft. To meet these objectives, papers were presented by representatives from NASA Langley, Ames, and Lewis Research Centers; Boeing, McDonnell Douglas, Northrop-Grumman, Lockheed-Martin, Vigyan, Analytical Services, Dynacs, and RIACS.

First NASA/Industry High-Speed Research Configuration Aerodynamics Workshop. Part 1

NASA Technical Reports Server (NTRS)

Wood, Richard M. (Editor)

1999-01-01

This publication is a compilation of documents presented at the First NASA/Industry High Speed Research Configuration Aerodynamics Workshop held on February 27-29, 1996 at NASA Langley Research Center. The purpose of the workshop was to bring together the broad spectrum of aerodynamicists, engineers, and scientists working within the Configuration Aerodynamics element of the HSR Program to collectively evaluate the technology status and to define the needs within Computational Fluid Dynamics (CFD) Analysis Methodology, Aerodynamic Shape Design, Propulsion/Airframe Integration (PAI), Aerodynamic Performance, and Stability and Control (S&C) to support the development of an economically viable High Speed Civil Transport (HSCT) aircraft. To meet these objectives, papers were presented by representative from NASA Langley, Ames, and Lewis Research Centers; Boeing, McDonnell Douglas, Northrop-Grumman, Lockheed-Martin, Vigyan, Analytical Services, Dynacs, and RIACS.

The Use of Fluid Mechanics to Predict Regions of Microscopic Thrombus Formation in Pulsatile VADs.

PubMed

Topper, Stephen R; Navitsky, Michael A; Medvitz, Richard B; Paterson, Eric G; Siedlecki, Christopher A; Slattery, Margaret J; Deutsch, Steven; Rosenberg, Gerson; Manning, Keefe B

2014-03-01

We compare the velocity and shear obtained from particle image velocimetry (PIV) and computational fluid dynamics (CFD) in a pulsatile ventricular assist device (VAD) to further test our thrombus predictive methodology using microscopy data from an explanted VAD. To mimic physiological conditions in vitro , a mock circulatory loop is used with a blood analog that matched blood's viscoelastic behavior at 40% hematocrit. Under normal physiologic pressures and for a heart rate of 75 bpm, PIV data is acquired and wall shear maps are produced. The resolution of the PIV shear rate calculations are tested using the CFD and found to be in the same range. A bovine study, using a model of the 50 cc Penn State V-2 VAD, for 30 days at a constant beat rate of 75 beats per minute (bpm) provides the microscopic data whereby after the 30 days, the device is explanted and the sac surface analyzed using scanning electron microscopy (SEM) and, after immunofluorescent labeling for platelets and fibrin, confocal microscopy. Areas are examined based on PIV measurements and CFD, with special attention to low shear regions where platelet and fibrin deposition are most likely to occur. Data collected within the outlet port in a direction normal to the front wall of the VAD shows that some regions experience wall shear rates less than 500 s -1 , which increases the likelihood of platelet and fibrin deposition. Despite only one animal study, correlations between PIV, CFD, and in vivo data show promise. Deposition probability is quantified by the thrombus susceptibility potential, a calculation to correlate low shear and time of shear with deposition.

PIV Uncertainty Methodologies for CFD Code Validation at the MIR Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabharwall, Piyush; Skifton, Richard; Stoots, Carl

2013-12-01

Currently, computational fluid dynamics (CFD) is widely used in the nuclear thermal hydraulics field for design and safety analyses. To validate CFD codes, high quality multi dimensional flow field data are essential. The Matched Index of Refraction (MIR) Flow Facility at Idaho National Laboratory has a unique capability to contribute to the development of validated CFD codes through the use of Particle Image Velocimetry (PIV). The significance of the MIR facility is that it permits non intrusive velocity measurement techniques, such as PIV, through complex models without requiring probes and other instrumentation that disturb the flow. At the heart ofmore » any PIV calculation is the cross-correlation, which is used to estimate the displacement of particles in some small part of the image over the time span between two images. This image displacement is indicated by the location of the largest peak. In the MIR facility, uncertainty quantification is a challenging task due to the use of optical measurement techniques. Currently, this study is developing a reliable method to analyze uncertainty and sensitivity of the measured data and develop a computer code to automatically analyze the uncertainty/sensitivity of the measured data. The main objective of this study is to develop a well established uncertainty quantification method for the MIR Flow Facility, which consists of many complicated uncertainty factors. In this study, the uncertainty sources are resolved in depth by categorizing them into uncertainties from the MIR flow loop and PIV system (including particle motion, image distortion, and data processing). Then, each uncertainty source is mathematically modeled or adequately defined. Finally, this study will provide a method and procedure to quantify the experimental uncertainty in the MIR Flow Facility with sample test results.« less

A thermal NO(x) prediction model - Scalar computation module for CFD codes with fluid and kinetic effects

NASA Technical Reports Server (NTRS)

Mcbeath, Giorgio; Ghorashi, Bahman; Chun, Kue

1993-01-01

A thermal NO(x) prediction model is developed to interface with a CFD, k-epsilon based code. A converged solution from the CFD code is the input to the postprocessing model for prediction of thermal NO(x). The model uses a decoupled analysis to estimate the equilibrium level of (NO(x))e which is the constant rate limit. This value is used to estimate the flame (NO(x)) and in turn predict the rate of formation at each node using a two-step Zeldovich mechanism. The rate is fixed on the NO(x) production rate plot by estimating the time to reach equilibrium by a differential analysis based on the reaction: O + N2 = NO + N. The rate is integrated in the nonequilibrium time space based on the residence time at each node in the computational domain. The sum of all nodal predictions yields the total NO(x) level.

Three-Dimensional Thermal Boundary Layer Corrections for Circular Heat Flux Gauges Mounted in a Flat Plate with a Surface Temperature Discontinuity

NASA Technical Reports Server (NTRS)

Kandula, M.; Haddad, G. F.; Chen, R.-H.

2006-01-01

Three-dimensional Navier-Stokes computational fluid dynamics (CFD) analysis has been performed in an effort to determine thermal boundary layer correction factors for circular convective heat flux gauges (such as Schmidt-Boelter and plug type)mounted flush in a flat plate subjected to a stepwise surface temperature discontinuity. Turbulent flow solutions with temperature-dependent properties are obtained for a free stream Reynolds number of 1E6, and freestream Mach numbers of 2 and 4. The effect of gauge diameter and the plate surface temperature have been investigated. The 3-D CFD results for the heat flux correction factors are compared to quasi-21) results deduced from constant property integral solutions and also 2-D CFD analysis with both constant and variable properties. The role of three-dimensionality and of property variations on the heat flux correction factors has been demonstrated.

Characterization of the Space Shuttle Ascent Debris using CFD Methods

NASA Technical Reports Server (NTRS)

Murman, Scott M.; Aftosmis, Michael J.; Rogers, Stuart E.

2005-01-01

After video analysis of space shuttle flight STS-107's ascent showed that an object shed from the bipod-ramp region impacted the left wing, a transport analysis was initiated to determine a credible flight path and impact velocity for the piece of debris. This debris transport analysis was performed both during orbit, and after the subsequent re-entry accident. The analysis provided an accurate prediction of the velocity a large piece of foam bipod ramp would have as it impacted the wing leading edge. This prediction was corroborated by video analysis and fully-coupled CFD/six degree of freedom (DOF) simulations. While the prediction of impact velocity was accurate enough to predict critical damage in this case, one of the recommendations of the Columbia Accident Investigation Board (CAIB) for return-to-flight (RTF) was to analyze the complete debris environment experienced by the shuttle stack on ascent. This includes categorizing all possible debris sources, their probable geometric and aerodynamic characteristics, and their potential for damage. This paper is chiefly concerned with predicting the aerodynamic characteristics of a variety of potential debris sources (insulating foam and cork, nose-cone ablator, ice, ...) for the shuttle ascent configuration using CFD methods. These aerodynamic characteristics are used in the debris transport analysis to predict flight path, impact velocity and angle, and provide statistical variation to perform risk analyses where appropriate. The debris aerodynamic characteristics are difficult to determine using traditional methods, such as static or dynamic test data, due to the scaling requirements of simulating a typical debris event. The use of CFD methods has been a critical element for building confidence in the accuracy of the debris transport code by bridging the gap between existing aerodynamic data and the dynamics of full-scale, in-flight events.

CFD Simulations of Supersonic Highly Swirling Flow Exiting a Turbine Vane Row Compared with Experimental Observations

NASA Technical Reports Server (NTRS)

West, Jeff S.; Richardson, Brian R.; Schmauch, Preston; Kenny, Robert J.

2011-01-01

Marshall Space Flight Center (MSFC) has been heavily involved in developing the J2-X engine. The Center has been testing a Work Horse Gas Generator (WHGG) to supply gas products to J2-X turbine components at realistic flight-like operating conditions. Three-dimensional time accurate CFD simulations and analytical fluid analysis have been performed to support WHGG tests at MSFC. The general purpose CFD program LOCI/Chem was utilized to simulate flow of products from the WHGG through a turbine manifold, a stationary row of turbine vanes, into a Can and orifice assembly used to control the back pressure at the turbine vane row and finally through an aspirator plate and flame bucket. Simulations showed that supersonic swirling flow downstream of the turbine imparted a much higher pressure on the Can wall than expected for a non-swirling flow. This result was verified by developing an analytical model that predicts wall pressure due to swirling flow. The CFD simulations predicted that the higher downstream pressure would cause the pressure drop across the nozzle row to be approximately half the value of the test objective. With CFD support, a redesign of the Can orifice and aspirator plate was performed. WHGG experimental results and observations compared well with pre-test and post-test CFD simulations. CFD simulations for both quasi-static and transient test conditions correctly predicted the pressure environment downstream of the turbine row and the behavior of the gas generator product plume as it exited the WHGG test article, impacted the flame bucket and interacted with the external environment.

Computational fluid dynamics endpoints to characterize obstructive sleep apnea syndrome in children

PubMed Central

Luo, Haiyan; Persak, Steven C.; Sin, Sanghun; McDonough, Joseph M.; Isasi, Carmen R.; Arens, Raanan

2013-01-01

Computational fluid dynamics (CFD) analysis may quantify the severity of anatomical airway restriction in obstructive sleep apnea syndrome (OSAS) better than anatomical measurements alone. However, optimal CFD model endpoints to characterize or assess OSAS have not been determined. To model upper airway fluid dynamics using CFD and investigate the strength of correlation between various CFD endpoints, anatomical endpoints, and OSAS severity, in obese children with OSAS and controls. CFD models derived from magnetic resonance images were solved at subject-specific peak tidal inspiratory flow; pressure at the choanae was set by nasal resistance. Model endpoints included airway wall minimum pressure (Pmin), flow resistance in the pharynx (Rpharynx), and pressure drop from choanae to a minimum cross section where tonsils and adenoids constrict the pharynx (dPTAmax). Significance of endpoints was analyzed using paired comparisons (t-test or Wilcoxon signed rank test) and Spearman correlation. Fifteen subject pairs were analyzed. Rpharynx and dPTAmax were higher in OSAS than control and most significantly correlated to obstructive apnea-hypopnea index (oAHI), r = 0.48 and r = 0.49, respectively (P < 0.01). Airway minimum cross-sectional correlation to oAHI was weaker (r = −0.39); Pmin was not significantly correlated. CFD model endpoints based on pressure drops in the pharynx were more closely associated with the presence and severity of OSAS than pressures including nasal resistance, or anatomical endpoints. This study supports the usefulness of CFD to characterize anatomical restriction of the pharynx and as an additional tool to evaluate subjects with OSAS. PMID:24265282

Aerodynamic study of different cyclist positions: CFD analysis and full-scale wind-tunnel tests.

PubMed

Defraeye, Thijs; Blocken, Bert; Koninckx, Erwin; Hespel, Peter; Carmeliet, Jan

2010-05-07

Three different cyclist positions were evaluated with Computational Fluid Dynamics (CFD) and wind-tunnel experiments were used to provide reliable data to evaluate the accuracy of the CFD simulations. Specific features of this study are: (1) both steady Reynolds-averaged Navier-Stokes (RANS) and unsteady flow modelling, with more advanced turbulence modelling techniques (Large-Eddy Simulation - LES), were evaluated; (2) the boundary layer on the cyclist's surface was resolved entirely with low-Reynolds number modelling, instead of modelling it with wall functions; (3) apart from drag measurements, also surface pressure measurements on the cyclist's body were performed in the wind-tunnel experiment, which provided the basis for a more detailed evaluation of the predicted flow field by CFD. The results show that the simulated and measured drag areas differed about 11% (RANS) and 7% (LES), which is considered to be a close agreement in CFD studies. A fair agreement with wind-tunnel data was obtained for the predicted surface pressures, especially with LES. Despite the higher accuracy of LES, its much higher computational cost could make RANS more attractive for practical use in some situations. CFD is found to be a valuable tool to evaluate the drag of different cyclist positions and to investigate the influence of small adjustments in the cyclist's position. A strong advantage of CFD is that detailed flow field information is obtained, which cannot easily be obtained from wind-tunnel tests. This detailed information allows more insight in the causes of the drag force and provides better guidance for position improvements. Copyright 2010 Elsevier Ltd. All rights reserved.

Decoupled 1D/3D analysis of a hydraulic valve

NASA Astrophysics Data System (ADS)

Mehring, Carsten; Zopeya, Ashok; Latham, Matt; Ihde, Thomas; Massie, Dan

2014-10-01

Analysis approaches during product development of fluid valves and other aircraft fluid delivery components vary greatly depending on the development stage. Traditionally, empirical or simplistic one-dimensional tools are being deployed during preliminary design, whereas detailed analysis such as CFD (Computational Fluid Dynamics) tools are used to refine a selected design during the detailed design stage. In recent years, combined 1D/3D co-simulation has been deployed specifically for system level simulations requiring an increased level of analysis detail for one or more components. The present paper presents a decoupled 1D/3D analysis approach where 3D CFD analysis results are utilized to enhance the fidelity of a dynamic 1D modelin context of an aircraft fuel valve.

The art of spacecraft design: A multidisciplinary challenge

NASA Technical Reports Server (NTRS)

Abdi, F.; Ide, H.; Levine, M.; Austel, L.

1989-01-01

Actual design turn-around time has become shorter due to the use of optimization techniques which have been introduced into the design process. It seems that what, how and when to use these optimization techniques may be the key factor for future aircraft engineering operations. Another important aspect of this technique is that complex physical phenomena can be modeled by a simple mathematical equation. The new powerful multilevel methodology reduces time-consuming analysis significantly while maintaining the coupling effects. This simultaneous analysis method stems from the implicit function theorem and system sensitivity derivatives of input variables. Use of the Taylor's series expansion and finite differencing technique for sensitivity derivatives in each discipline makes this approach unique for screening dominant variables from nondominant variables. In this study, the current Computational Fluid Dynamics (CFD) aerodynamic and sensitivity derivative/optimization techniques are applied for a simple cone-type forebody of a high-speed vehicle configuration to understand basic aerodynamic/structure interaction in a hypersonic flight condition.

Transition Documentation on a Three-Element High-Lift Configuration at High Reynolds Numbers: Analysis

NASA Technical Reports Server (NTRS)

Bertelrud, Arild; Anders, J. B. (Technical Monitor)

2002-01-01

A 2-D high-lift system experiment was conducted in August of 1996 in the Low Turbulence Pressure Tunnel at NASA Langley Research Center, Hampton, VA. The purpose of the experiment was to obtain transition measurements on a three element high-lift system for CFD code validation studies. A transition database has been created using the data from this experiment. The present report contains the analysis of the surface hot film data in terms of the transition locations on the three elements. It also includes relevant information regarding the pressure loads and distributions and the wakes behind the model to aid in the interpretation of the transition data. For some of the configurations the current pressure data has been compared with previous wind tunnel entries of the same model. The methodology used to determine the regions of transitional flow is outlined and each configuration tested has been analyzed. A discussion of interference effects, repeatability, and three-dimensional effects on the data is included.

Boom Minimization Framework for Supersonic Aircraft Using CFD Analysis

NASA Technical Reports Server (NTRS)

Ordaz, Irian; Rallabhandi, Sriram K.

2010-01-01

A new framework is presented for shape optimization using analytical shape functions and high-fidelity computational fluid dynamics (CFD) via Cart3D. The focus of the paper is the system-level integration of several key enabling analysis tools and automation methods to perform shape optimization and reduce sonic boom footprint. A boom mitigation case study subject to performance, stability and geometrical requirements is presented to demonstrate a subset of the capabilities of the framework. Lastly, a design space exploration is carried out to assess the key parameters and constraints driving the design.

CFD Analysis of Flexible Thermal Protection System Shear Configuration Testing in the LCAT Facility

NASA Technical Reports Server (NTRS)

Ferlemann, Paul G.

2014-01-01

This paper documents results of computational analysis performed after flexible thermal protection system shear configuration testing in the LCAT facility. The primary objectives were to predict the shear force on the sample and the sensitivity of all surface properties to the shape of the sample. Bumps of 0.05, 0.10,and 0.15 inches were created to approximate the shape of some fabric samples during testing. A large amount of information was extracted from the CFD solutions for comparison between runs and also current or future flight simulations.

Premixed Supersonic Combustion (Rev)

DTIC Science & Technology

2015-02-20

the effects of equivalence ratio and inflow gas temperature on flame ignition, propagation, and flameout. This study was performed in collaboration...6 combustor. CFD analysis indicates this feature promotes flame holding in the combustor. The cavity spans the width of the duct and has an...Fig. 1). Figure 2 shows results from a RANS CFD study of several potential strategies based on fuel injection at the upstream end of the isolator

Pre-Test CFD for the Design and Execution of the Enhanced Injection and Mixing Project at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Drozda, Tomasz G.; Axdahl, Erik L.; Cabell, Karen F.

2014-01-01

With the increasing costs of physics experiments and simultaneous increase in availability and maturity of computational tools it is not surprising that computational fluid dynamics (CFD) is playing an increasingly important role, not only in post-test investigations, but also in the early stages of experimental planning. This paper describes a CFD-based effort executed in close collaboration between computational fluid dynamicists and experimentalists to develop a virtual experiment during the early planning stages of the Enhanced Injection and Mixing project at NASA Langley Research Center. This projects aims to investigate supersonic combustion ramjet (scramjet) fuel injection and mixing physics, improve the understanding of underlying physical processes, and develop enhancement strategies and functional relationships relevant to flight Mach numbers greater than 8. The purpose of the virtual experiment was to provide flow field data to aid in the design of the experimental apparatus and the in-stream rake probes, to verify the nonintrusive measurements based on NO-PLIF, and to perform pre-test analysis of quantities obtainable from the experiment and CFD. The approach also allowed for the joint team to develop common data processing and analysis tools, and to test research ideas. The virtual experiment consisted of a series of Reynolds-averaged simulations (RAS). These simulations included the facility nozzle, the experimental apparatus with a baseline strut injector, and the test cabin. Pure helium and helium-air mixtures were used to determine the efficacy of different inert gases to model hydrogen injection. The results of the simulations were analyzed by computing mixing efficiency, total pressure recovery, and stream thrust potential. As the experimental effort progresses, the simulation results will be compared with the experimental data to calibrate the modeling constants present in the CFD and validate simulation fidelity. CFD will also be used to investigate different injector concepts, improve understanding of the flow structure and flow physics, and develop functional relationships. Both RAS and large eddy simulations (LES) are planned for post-test analysis of the experimental data.

Parallel Visualization Co-Processing of Overnight CFD Propulsion Applications

NASA Technical Reports Server (NTRS)

Edwards, David E.; Haimes, Robert

1999-01-01

An interactive visualization system pV3 is being developed for the investigation of advanced computational methodologies employing visualization and parallel processing for the extraction of information contained in large-scale transient engineering simulations. Visual techniques for extracting information from the data in terms of cutting planes, iso-surfaces, particle tracing and vector fields are included in this system. This paper discusses improvements to the pV3 system developed under NASA's Affordable High Performance Computing project.

Study of the filtration performance of a plain wave fabric filter using response surface methodology.

PubMed

Qian, Fuping; Wang, Haigang

2010-04-15

The gas-solid two-phase flows in the plain wave fabric filter were simulated by computational fluid dynamics (CFD) technology, and the warps and wefts of the fabric filter were made of filaments with different dimensions. The numerical solutions were carried out using commercial computational fluid dynamics (CFD) code Fluent 6.1. The filtration performances of the plain wave fabric filter with different geometry parameters and operating condition, including the horizontal distance, the vertical distance and the face velocity were calculated. The effects of geometry parameters and operating condition on filtration efficiency and pressure drop were studied using response surface methodology (RSM) by means of the statistical software (Minitab V14), and two second-order polynomial models were obtained with regard to the effect of the three factors as stated above. Moreover, the models were modified by dismissing the insignificant terms. The results show that the horizontal distance, vertical distance and the face velocity all play an important role in influencing the filtration efficiency and pressure drop of the plane wave fabric filters. The horizontal distance of 3.8 times the fiber diameter, the vertical distance of 4.0 times the fiber diameter and Reynolds number of 0.98 are found to be the optimal conditions to achieve the highest filtration efficiency at the same face velocity, while maintaining an acceptable pressure drop. 2009 Elsevier B.V. All rights reserved.

CFD study of ejector flow behavior in a blast furnace gas galvanizing plant

NASA Astrophysics Data System (ADS)

Besagni, Giorgio; Mereu, Riccardo; Inzoli, Fabio

2015-02-01

In recent years, there has been a growing interest toward Blast Furnace Gas (BFG) as a low-grade energy source for industrial furnaces. This paper considers the revamping of a galvanic plant furnace converted to BFG from natural gas. In the design of the new system, the ejector on the exhaust line is a critical component. This paper studies the flow behavior of the ejector using a Computational Fluid Dynamics (CFD) analysis. The CFD model is based on a 3D representation of the ejector, using air and exhaust gases as working fluids. This paper is divided in three parts. In the first part, the galvanic plant used as case study is presented and discussed, in the second part the CFD approach is outlined, and in the third part the CFD approach is validated using experimental data and the numerical results are presented and discussed. Different Reynolds-Averaged Navier-Stokes (RANS) turbulence models ( k-ω SST and k-ɛ Realizable) are evaluated in terms of convergence capability and accuracy in predicting the pressure drop along the ejector. Suggestions for future optimization of the system are also provided.

CFD Design and Analysis of a Passively Suspended Tesla Pump Left Ventricular Assist Device

PubMed Central

Medvitz, Richard B.; Boger, David A.; Izraelev, Valentin; Rosenberg, Gerson; Paterson, Eric G.

2012-01-01

This paper summarizes the use of computational fluid dynamics (CFD) to design a novelly suspended Tesla LVAD. Several design variants were analyzed to study the parameters affecting device performance. CFD was performed at pump speeds of 6500, 6750 and 7000 RPM and at flow rates varying from 3 to 7 liter-per-minute (LPM). The CFD showed that shortening the plates nearest the pump inlet reduced the separations formed beneath the upper plate leading edges and provided a more uniform flow distribution through the rotor gaps, both of which positively affected the device hydrodynamic performance. The final pump design was found to produce a head rise of 77 mmHg with a hydraulic efficiency of 16% at the design conditions of 6 LPM throughflow and a 6750 RPM rotation rate. To assess the device hemodynamics the strain rate fields were evaluated. The wall shear stresses demonstrated that the pump wall shear stresses were likely adequate to inhibit thrombus deposition. Finally, an integrated field hemolysis model was applied to the CFD results to assess the effects of design variation and operating conditions on the device hemolytic performance. PMID:21595722

Development of Multi-physics (Multiphase CFD + MCNP) simulation for generic solution vessel power calculation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Seung Jun; Buechler, Cynthia Eileen

The current study aims to predict the steady state power of a generic solution vessel and to develop a corresponding heat transfer coefficient correlation for a Moly99 production facility by conducting a fully coupled multi-physics simulation. A prediction of steady state power for the current application is inherently interconnected between thermal hydraulic characteristics (i.e. Multiphase computational fluid dynamics solved by ANSYS-Fluent 17.2) and the corresponding neutronic behavior (i.e. particle transport solved by MCNP6.2) in the solution vessel. Thus, the development of a coupling methodology is vital to understand the system behavior at a variety of system design and postulated operatingmore » scenarios. In this study, we report on the k-effective (keff) calculation for the baseline solution vessel configuration with a selected solution concentration using MCNP K-code modeling. The associated correlation of thermal properties (e.g. density, viscosity, thermal conductivity, specific heat) at the selected solution concentration are developed based on existing experimental measurements in the open literature. The numerical coupling methodology between multiphase CFD and MCNP is successfully demonstrated, and the detailed coupling procedure is documented. In addition, improved coupling methods capturing realistic physics in the solution vessel thermal-neutronic dynamics are proposed and tested further (i.e. dynamic height adjustment, mull-cell approach). As a key outcome of the current study, a multi-physics coupling methodology between MCFD and MCNP is demonstrated and tested for four different operating conditions. Those different operating conditions are determined based on the neutron source strength at a fixed geometry condition. The steady state powers for the generic solution vessel at various operating conditions are reported, and a generalized correlation of the heat transfer coefficient for the current application is discussed. The assessment of multi-physics methodology and preliminary results from various coupled calculations (power prediction and heat transfer coefficient) can be further utilized for the system code validation and generic solution vessel design improvement.« less

Automated Extraction of Secondary Flow Features

NASA Technical Reports Server (NTRS)

Dorney, Suzanne M.; Haimes, Robert

2005-01-01

The use of Computational Fluid Dynamics (CFD) has become standard practice in the design and development of the major components used for air and space propulsion. To aid in the post-processing and analysis phase of CFD many researchers now use automated feature extraction utilities. These tools can be used to detect the existence of such features as shocks, vortex cores and separation and re-attachment lines. The existence of secondary flow is another feature of significant importance to CFD engineers. Although the concept of secondary flow is relatively understood there is no commonly accepted mathematical definition for secondary flow. This paper will present a definition for secondary flow and one approach for automatically detecting and visualizing secondary flow.

Transonic Blunt Body Aerodynamic Coefficients Computation

NASA Astrophysics Data System (ADS)

Sancho, Jorge; Vargas, M.; Gonzalez, Ezequiel; Rodriguez, Manuel

2011-05-01

In the framework of EXPERT (European Experimental Re-entry Test-bed) accurate transonic aerodynamic coefficients are of paramount importance for the correct trajectory assessment and parachute deployment. A combined CFD (Computational Fluid Dynamics) modelling and experimental campaign strategy was selected to obtain accurate coefficients. A preliminary set of coefficients were obtained by CFD Euler inviscid computation. Then experimental campaign was performed at DNW facilities at NLR. A profound review of the CFD modelling was done lighten up by WTT results, aimed to obtain reliable values of the coefficients in the future (specially the pitching moment). Study includes different turbulence modelling and mesh sensitivity analysis. Comparison with the WTT results is explored, and lessons learnt are collected.

A Quasi-Steady Flexible Launch Vehicle Stability Analysis Using Steady CFD with Unsteady Aerodynamic Enhancement

NASA Technical Reports Server (NTRS)

Bartels, Robert E.

2011-01-01

Launch vehicles frequently experience a reduced stability margin through the transonic Mach number range. This reduced stability margin is caused by an undamping of the aerodynamics in one of the lower frequency flexible or rigid body modes. Analysis of the behavior of a flexible vehicle is routinely performed with quasi-steady aerodynamic lineloads derived from steady rigid computational fluid dynamics (CFD). However, a quasi-steady aeroelastic stability analysis can be unconservative at the critical Mach numbers where experiment or unsteady computational aeroelastic (CAE) analysis show a reduced or even negative aerodynamic damping. This paper will present a method of enhancing the quasi-steady aeroelastic stability analysis of a launch vehicle with unsteady aerodynamics. The enhanced formulation uses unsteady CFD to compute the response of selected lower frequency modes. The response is contained in a time history of the vehicle lineloads. A proper orthogonal decomposition of the unsteady aerodynamic lineload response is used to reduce the scale of data volume and system identification is used to derive the aerodynamic stiffness, damping and mass matrices. The results of the enhanced quasi-static aeroelastic stability analysis are compared with the damping and frequency computed from unsteady CAE analysis and from a quasi-steady analysis. The results show that incorporating unsteady aerodynamics in this way brings the enhanced quasi-steady aeroelastic stability analysis into close agreement with the unsteady CAE analysis.

Analysis of subsonic wind tunnel with variation shape rectangular and octagonal on test section

NASA Astrophysics Data System (ADS)

Rhakasywi, D.; Ismail; Suwandi, A.; Fadhli, A.

2018-02-01

The need for good design in the aerodynamics field required a wind tunnel design. The wind tunnel design required in this case is capable of generating laminar flow. In this research searched for wind tunnel models with rectangular and octagonal variations with objectives to generate laminar flow in the test section. The research method used numerical approach of CFD (Computational Fluid Dynamics) and manual analysis to analyze internal flow in test section. By CFD simulation results and manual analysis to generate laminar flow in the test section is a design that has an octagonal shape without filled for optimal design.

Emissions Prediction and Measurement for Liquid-Fueled TVC Combustor with and without Water Injection

NASA Technical Reports Server (NTRS)

Brankovic, A.; Ryder, R. C., Jr.; Hendricks, R. C.; Liu, N.-S.; Shouse, D. T.; Roquemore, W. M.

2005-01-01

An investigation is performed to evaluate the performance of a computational fluid dynamics (CFD) tool for the prediction of the reacting flow in a liquid-fueled combustor that uses water injection for control of pollutant emissions. The experiment consists of a multisector, liquid-fueled combustor rig operated at different inlet pressures and temperatures, and over a range of fuel/air and water/fuel ratios. Fuel can be injected directly into the main combustion airstream and into the cavities. Test rig performance is characterized by combustor exit quantities such as temperature and emissions measurements using rakes and overall pressure drop from upstream plenum to combustor exit. Visualization of the flame is performed using gray scale and color still photographs and high-frame-rate videos. CFD simulations are performed utilizing a methodology that includes computer-aided design (CAD) solid modeling of the geometry, parallel processing over networked computers, and graphical and quantitative post-processing. Physical models include liquid fuel droplet dynamics and evaporation, with combustion modeled using a hybrid finite-rate chemistry model developed for Jet-A fuel. CFD and experimental results are compared for cases with cavity-only fueling, while numerical studies of cavity and main fueling was also performed. Predicted and measured trends in combustor exit temperature, CO and NOx are in general agreement at the different water/fuel loading rates, although quantitative differences exist between the predictions and measurements.

Current Status of Post-combustor Trace Chemistry Modeling and Simulation at NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Wey, Thomas; Liu, Nan-Suey

2003-01-01

The overall objective of the current effort at NASA GRC is to evaluate, develop, and apply methodologies suitable for modeling intra-engine trace chemical changes over post combustor flow path relevant to the pollutant emissions from aircraft engines. At the present time, the focus is the high pressure turbine environment. At first, the trace chemistry model of CNEWT were implemented into GLENN-HT as well as NCC. Then, CNEWT, CGLENN-HT, and NCC were applied to the trace species evolution in a cascade of Cambridge University's No. 2 rotor and in a turbine vane passage. In general, the results from these different codes provide similar features. However, the details of some of the quantities of interest can be sensitive to the differences of these codes. This report summaries the implementation effort and presents the comparison of the No. 2 rotor results obtained from these different codes. The comparison of the turbine vane passage results is reported elsewhere. In addition to the implementation of trace chemistry model into existing CFD codes, several pre/post-processing tools that can handle the manipulations of the geometry, the unstructured and structured grids as well as the CFD solutions also have been enhanced and seamlessly tied with NCC, CGLENN-HT, and CNEWT. Thus, a complete CFD package consisting of pre/post-processing tools and flow solvers suitable for post-combustor intra-engine trace chemistry study is assembled.

Inverse Design of Low-Boom Supersonic Concepts Using Reversed Equivalent-Area Targets

NASA Technical Reports Server (NTRS)

Li, Wu; Rallabhand, Sriam

2011-01-01

A promising path for developing a low-boom configuration is a multifidelity approach that (1) starts from a low-fidelity low-boom design, (2) refines the low-fidelity design with computational fluid dynamics (CFD) equivalent-area (Ae) analysis, and (3) improves the design with sonic-boom analysis by using CFD off-body pressure distributions. The focus of this paper is on the third step of this approach, in which the design is improved with sonic-boom analysis through the use of CFD calculations. A new inverse design process for off-body pressure tailoring is formulated and demonstrated with a low-boom supersonic configuration that was developed by using the mixed-fidelity design method with CFD Ae analysis. The new inverse design process uses the reverse propagation of the pressure distribution (dp/p) from a mid-field location to a near-field location, converts the near-field dp/p into an equivalent-area distribution, generates a low-boom target for the reversed equivalent area (Ae,r) of the configuration, and modifies the configuration to minimize the differences between the configuration s Ae,r and the low-boom target. The new inverse design process is used to modify a supersonic demonstrator concept for a cruise Mach number of 1.6 and a cruise weight of 30,000 lb. The modified configuration has a fully shaped ground signature that has a perceived loudness (PLdB) value of 78.5, while the original configuration has a partially shaped aft signature with a PLdB of 82.3.

Combustion Devices CFD Team Analyses Review

NASA Technical Reports Server (NTRS)

Rocker, Marvin

2008-01-01

A variety of CFD simulations performed by the Combustion Devices CFD Team at Marshall Space Flight Center will be presented. These analyses were performed to support Space Shuttle operations and Ares-1 Crew Launch Vehicle design. Results from the analyses will be shown along with pertinent information on the CFD codes and computational resources used to obtain the results. Six analyses will be presented - two related to the Space Shuttle and four related to the Ares I-1 launch vehicle now under development at NASA. First, a CFD analysis of the flow fields around the Space Shuttle during the first six seconds of flight and potential debris trajectories within those flow fields will be discussed. Second, the combusting flows within the Space Shuttle Main Engine's main combustion chamber will be shown. For the Ares I-1, an analysis of the performance of the roll control thrusters during flight will be described. Several studies are discussed related to the J2-X engine to be used on the upper stage of the Ares I-1 vehicle. A parametric study of the propellant flow sequences and mixture ratios within the GOX/GH2 spark igniters on the J2-X is discussed. Transient simulations will be described that predict the asymmetric pressure loads that occur on the rocket nozzle during the engine start as the nozzle fills with combusting gases. Simulations of issues that affect temperature uniformity within the gas generator used to drive the J-2X turbines will described as well, both upstream of the chamber in the injector manifolds and within the combustion chamber itself.

Software Performs Complex Design Analysis

NASA Technical Reports Server (NTRS)

2008-01-01

Designers use computational fluid dynamics (CFD) to gain greater understanding of the fluid flow phenomena involved in components being designed. They also use finite element analysis (FEA) as a tool to help gain greater understanding of the structural response of components to loads, stresses and strains, and the prediction of failure modes. Automated CFD and FEA engineering design has centered on shape optimization, which has been hindered by two major problems: 1) inadequate shape parameterization algorithms, and 2) inadequate algorithms for CFD and FEA grid modification. Working with software engineers at Stennis Space Center, a NASA commercial partner, Optimal Solutions Software LLC, was able to utilize its revolutionary, one-of-a-kind arbitrary shape deformation (ASD) capability-a major advancement in solving these two aforementioned problems-to optimize the shapes of complex pipe components that transport highly sensitive fluids. The ASD technology solves the problem of inadequate shape parameterization algorithms by allowing the CFD designers to freely create their own shape parameters, therefore eliminating the restriction of only being able to use the computer-aided design (CAD) parameters. The problem of inadequate algorithms for CFD grid modification is solved by the fact that the new software performs a smooth volumetric deformation. This eliminates the extremely costly process of having to remesh the grid for every shape change desired. The program can perform a design change in a markedly reduced amount of time, a process that would traditionally involve the designer returning to the CAD model to reshape and then remesh the shapes, something that has been known to take hours, days-even weeks or months-depending upon the size of the model.

Evaluation of an urban vegetative canopy scheme and impact on plume dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Matthew A; Williams, Michael D; Zajic, Dragan

2009-01-01

The Quick Urban and Industrial Complex (QUIC) atmospheric dispersion modeling system attempts to fill an important gap between the fast, but nonbuilding-aware Gaussian plume models and the building-aware but slow computational fluid dynamics (CFD) models. While Gaussian models have the ability to give answers quickly to emergency responders, they are unlikely to be able to adequately account for the effects of the building-induced complex flow patterns on the near-source dispersion of contaminants. QUIC uses a diagnostic massconsistent empirical wind model called QUIC-URB that is based on the methodology of Rockle (1990), (see also Kaplan and Dinar 1996). In this approach,more » the recirculation zones that form around and between buildings are inserted into the flow using empirical parameterizations and then the wind field is forced to be mass consistent. Although not as accurate as CFD codes, this approach is several orders of magnitude faster and accounts for the bulk effects of buildings.« less

A hybrid anchored-ANOVA - POD/Kriging method for uncertainty quantification in unsteady high-fidelity CFD simulations

NASA Astrophysics Data System (ADS)

Margheri, Luca; Sagaut, Pierre

2016-11-01

To significantly increase the contribution of numerical computational fluid dynamics (CFD) simulation for risk assessment and decision making, it is important to quantitatively measure the impact of uncertainties to assess the reliability and robustness of the results. As unsteady high-fidelity CFD simulations are becoming the standard for industrial applications, reducing the number of required samples to perform sensitivity (SA) and uncertainty quantification (UQ) analysis is an actual engineering challenge. The novel approach presented in this paper is based on an efficient hybridization between the anchored-ANOVA and the POD/Kriging methods, which have already been used in CFD-UQ realistic applications, and the definition of best practices to achieve global accuracy. The anchored-ANOVA method is used to efficiently reduce the UQ dimension space, while the POD/Kriging is used to smooth and interpolate each anchored-ANOVA term. The main advantages of the proposed method are illustrated through four applications with increasing complexity, most of them based on Large-Eddy Simulation as a high-fidelity CFD tool: the turbulent channel flow, the flow around an isolated bluff-body, a pedestrian wind comfort study in a full scale urban area and an application to toxic gas dispersion in a full scale city area. The proposed c-APK method (anchored-ANOVA-POD/Kriging) inherits the advantages of each key element: interpolation through POD/Kriging precludes the use of quadrature schemes therefore allowing for a more flexible sampling strategy while the ANOVA decomposition allows for a better domain exploration. A comparison of the three methods is given for each application. In addition, the importance of adding flexibility to the control parameters and the choice of the quantity of interest (QoI) are discussed. As a result, global accuracy can be achieved with a reasonable number of samples allowing computationally expensive CFD-UQ analysis.

SCISEAL: A CFD Code for Analysis of Fluid Dynamic Forces in Seals

NASA Technical Reports Server (NTRS)

Althavale, Mahesh M.; Ho, Yin-Hsing; Przekwas, Andre J.

1996-01-01

A 3D CFD code, SCISEAL, has been developed and validated. Its capabilities include cylindrical seals, and it is employed on labyrinth seals, rim seals, and disc cavities. State-of-the-art numerical methods include colocated grids, high-order differencing, and turbulence models which account for wall roughness. SCISEAL computes efficient solutions for complicated flow geometries and seal-specific capabilities (rotor loads, torques, etc.).

Visualization Techniques Applied to 155-mm Projectile Analysis

DTIC Science & Technology

2014-11-01

semi-infinite Riemann problems are used in CFD++ to provide upwind flux information to the underlying transport scheme. Approximate Riemann solvers ...characteristics-based inflow/outflow boundary condition, which is based on solving a Riemann problem at the boundary. 2.3 Numerics Rolling/spinning is the...the solution files generated by the computational fluid dynamics (CFD) solver for the time-accurate rolling simulations at each timestep for the Mach

Integration of plume and puff diffusion models/application of CFD

NASA Astrophysics Data System (ADS)

Mori, Akira

The clinical symptoms of patients and other evidences of a gas poisoning accident inside an industrial building strongly suggested an abrupt influx of engine exhaust from a construction vehicle which was operating outside in the open air. But the obviously high level of gas concentration could not be well explained by any conventional steady-state gas diffusion models. The author used an unsteady-state continuous Puff Model to simulate the time-wise changes in air stream with the pollutant gas being continuously emitted, and successfully reproduced the observed phenomena. The author demonstrates that this diffusion formula can be solved analytically by the use of error function as long as the change in wind velocity is stepwise, and clarifies the accurate differences between the unsteady- and steady-states and their convergence profiles. Also, the relationship between the Puff and Plume Models is discussed. The case study included a computational fluid dynamics (CFD) analysis to estimate the steady-state air stream and the gas concentration pattern in the affected area. It is well known that clear definition of the boundary conditions is key to successful CFD analysis. The author describes a two-step use of CFD: the first step to define the boundary conditions and the second to determine the steady-state air stream and the gas concentration pattern.

CFD Sensitivity Analysis of a Modern Civil Transport Near Buffet-Onset Conditions

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L.; Allison, Dennis O.; Biedron, Robert T.; Buning, Pieter G.; Gainer, Thomas G.; Morrison, Joseph H.; Rivers, S. Melissa; Mysko, Stephen J.; Witkowski, David P.

2001-01-01

A computational fluid dynamics (CFD) sensitivity analysis is conducted for a modern civil transport at several conditions ranging from mostly attached flow to flow with substantial separation. Two different Navier-Stokes computer codes and four different turbulence models are utilized, and results are compared both to wind tunnel data at flight Reynolds number and flight data. In-depth CFD sensitivities to grid, code, spatial differencing method, aeroelastic shape, and turbulence model are described for conditions near buffet onset (a condition at which significant separation exists). In summary, given a grid of sufficient density for a given aeroelastic wing shape, the combined approximate error band in CFD at conditions near buffet onset due to code, spatial differencing method, and turbulence model is: 6% in lift, 7% in drag, and 16% in moment. The biggest two contributers to this uncertainty are turbulence model and code. Computed results agree well with wind tunnel surface pressure measurements both for an overspeed 'cruise' case as well as a case with small trailing edge separation. At and beyond buffet onset, computed results agree well over the inner half of the wing, but shock location is predicted too far aft at some of the outboard stations. Lift, drag, and moment curves are predicted in good agreement with experimental results from the wind tunnel.

Open Rotor Computational Aeroacoustic Analysis with an Immersed Boundary Method

NASA Technical Reports Server (NTRS)

Brehm, Christoph; Barad, Michael F.; Kiris, Cetin C.

2016-01-01

Reliable noise prediction capabilities are essential to enable novel fuel efficient open rotor designs that can meet the community and cabin noise standards. Toward this end, immersed boundary methods have reached a level of maturity where more and more complex flow problems can be tackled with this approach. This paper demonstrates that our higher-order immersed boundary method provides the ability for aeroacoustic analysis of wake-dominated flow fields generated by a contra-rotating open rotor. This is the first of a kind aeroacoustic simulation of an open rotor propulsion system employing an immersed boundary method. In addition to discussing the methodologies of how to apply the immersed boundary method to this moving boundary problem, we will provide a detailed validation of the aeroacoustic analysis approach employing the Launch Ascent and Vehicle Aerodynamics (LAVA) solver. Two free-stream Mach numbers with M=0.2 and M=0.78 are considered in this analysis that are based on the nominally take-off and cruise flow conditions. The simulation data is compared to available experimental data and other computational results employing more conventional CFD methods. Spectral analysis is used to determine the dominant wave propagation pattern in the acoustic near-field.

Analysing the effects of air flow on a formula prototype vehicle to optimize its performance

NASA Astrophysics Data System (ADS)

Rastogi, Nisha; Shetty, Siddhanth; Ashok, B.

2017-11-01

FSAE (Formula Society of Automotive Engineers) is an_engineering design competition which challenges students to design and build their own Formula Style race-car. The race-car is being judged on basis of various criteria namely, design, cost, business and performance. For the race-car to participate in the dynamic events and traverse through different sorts of challenging tracks in the least time possible, the tyres must generate appropriate amount of lateral and longitudinal force. The car must not topple even at high speeds and needs to manoeuvre quickly. To achieve the above-mentioned criterion, there is a need of implementing aerodynamics in the car. The optimum amount of downforce necessary to execute a smooth and rapid active behaviour of our car with maximum achievable performance is to be measured keeping vehicle dynamics into consideration. In this paper, vehicle dynamics and aerodynamics are related to an extent where all the above criterion can be achieved successfully, thereby bringing about a trade-off without any sort of compromises in either of them. The co-ordination between aerodynamics and vehicle dynamics has been depicted with a detailed methodology, accompanied by Computational Fluid Dynamics (CFD) simulations of the wings and the full body of the car using STAR CCM+. Further the results has been discussed properly in the later sections of this paper. With a systematic approach, thoroughly done with several iterations on MATLAB followed by CFD simulations and analysis, the desired performance was accomplished.

Arbitrary Shape Deformation in CFD Design

NASA Technical Reports Server (NTRS)

Landon, Mark; Perry, Ernest

2014-01-01

Sculptor(R) is a commercially available software tool, based on an Arbitrary Shape Design (ASD), which allows the user to perform shape optimization for computational fluid dynamics (CFD) design. The developed software tool provides important advances in the state-of-the-art of automatic CFD shape deformations and optimization software. CFD is an analysis tool that is used by engineering designers to help gain a greater understanding of the fluid flow phenomena involved in the components being designed. The next step in the engineering design process is to then modify, the design to improve the components' performance. This step has traditionally been performed manually via trial and error. Two major problems that have, in the past, hindered the development of an automated CFD shape optimization are (1) inadequate shape parameterization algorithms, and (2) inadequate algorithms for CFD grid modification. The ASD that has been developed as part of the Sculptor(R) software tool is a major advancement in solving these two issues. First, the ASD allows the CFD designer to freely create his own shape parameters, thereby eliminating the restriction of only being able to use the CAD model parameters. Then, the software performs a smooth volumetric deformation, which eliminates the extremely costly process of having to remesh the grid for every shape change (which is how this process had previously been achieved). Sculptor(R) can be used to optimize shapes for aerodynamic and structural design of spacecraft, aircraft, watercraft, ducts, and other objects that affect and are affected by flows of fluids and heat. Sculptor(R) makes it possible to perform, in real time, a design change that would manually take hours or days if remeshing were needed.

Development, Verification and Validation of Parallel, Scalable Volume of Fluid CFD Program for Propulsion Applications

NASA Technical Reports Server (NTRS)

West, Jeff; Yang, H. Q.

2014-01-01

There are many instances involving liquid/gas interfaces and their dynamics in the design of liquid engine powered rockets such as the Space Launch System (SLS). Some examples of these applications are: Propellant tank draining and slosh, subcritical condition injector analysis for gas generators, preburners and thrust chambers, water deluge mitigation for launch induced environments and even solid rocket motor liquid slag dynamics. Commercially available CFD programs simulating gas/liquid interfaces using the Volume of Fluid approach are currently limited in their parallel scalability. In 2010 for instance, an internal NASA/MSFC review of three commercial tools revealed that parallel scalability was seriously compromised at 8 cpus and no additional speedup was possible after 32 cpus. Other non-interface CFD applications at the time were demonstrating useful parallel scalability up to 4,096 processors or more. Based on this review, NASA/MSFC initiated an effort to implement a Volume of Fluid implementation within the unstructured mesh, pressure-based algorithm CFD program, Loci-STREAM. After verification was achieved by comparing results to the commercial CFD program CFD-Ace+, and validation by direct comparison with data, Loci-STREAM-VoF is now the production CFD tool for propellant slosh force and slosh damping rate simulations at NASA/MSFC. On these applications, good parallel scalability has been demonstrated for problems sizes of tens of millions of cells and thousands of cpu cores. Ongoing efforts are focused on the application of Loci-STREAM-VoF to predict the transient flow patterns of water on the SLS Mobile Launch Platform in order to support the phasing of water for launch environment mitigation so that vehicle determinantal effects are not realized.

Patient-specific analysis of post-operative aortic hemodynamics: a focus on thoracic endovascular repair (TEVAR)

NASA Astrophysics Data System (ADS)

Auricchio, F.; Conti, M.; Lefieux, A.; Morganti, S.; Reali, A.; Sardanelli, F.; Secchi, F.; Trimarchi, S.; Veneziani, A.

2014-10-01

The purpose of this study is to quantitatively evaluate the impact of endovascular repair on aortic hemodynamics. The study addresses the assessment of post-operative hemodynamic conditions of a real clinical case through patient-specific analysis, combining accurate medical image analysis and advanced computational fluid-dynamics (CFD). Although the main clinical concern was firstly directed to the endoluminal protrusion of the prosthesis, the CFD simulations have demonstrated that there are two other important areas where the local hemodynamics is impaired and a disturbed blood flow is present: the first one is the ostium of the subclavian artery, which is partially closed by the graft; the second one is the stenosis of the distal thoracic aorta. Besides the clinical relevance of these specific findings, this study highlights how CFD analyses allow to observe important flow effects resulting from the specific features of patient vessel geometries. Consequently, our results demonstrate the potential impact of computational biomechanics not only on the basic knowledge of physiopathology, but also on the clinical practice, thanks to a quantitative extraction of knowledge made possible by merging medical data and mathematical models.

Optimization of operating parameters in polysilicon chemical vapor deposition reactor with response surface methodology

NASA Astrophysics Data System (ADS)

An, Li-sha; Liu, Chun-jiao; Liu, Ying-wen

2018-05-01

In the polysilicon chemical vapor deposition reactor, the operating parameters are complex to affect the polysilicon's output. Therefore, it is very important to address the coupling problem of multiple parameters and solve the optimization in a computationally efficient manner. Here, we adopted Response Surface Methodology (RSM) to analyze the complex coupling effects of different operating parameters on silicon deposition rate (R) and further achieve effective optimization of the silicon CVD system. Based on finite numerical experiments, an accurate RSM regression model is obtained and applied to predict the R with different operating parameters, including temperature (T), pressure (P), inlet velocity (V), and inlet mole fraction of H2 (M). The analysis of variance is conducted to describe the rationality of regression model and examine the statistical significance of each factor. Consequently, the optimum combination of operating parameters for the silicon CVD reactor is: T = 1400 K, P = 3.82 atm, V = 3.41 m/s, M = 0.91. The validation tests and optimum solution show that the results are in good agreement with those from CFD model and the deviations of the predicted values are less than 4.19%. This work provides a theoretical guidance to operate the polysilicon CVD process.

Shuttle Return-to-Flight IH-108 Aerothermal Test at CUBRC - Flow Field Calibration and CFD

NASA Technical Reports Server (NTRS)

Lau, Kei Y.; Holden, M. S.

2011-01-01

This paper discusses one specific aspect of the Shuttle Retrun-To-Flight IH-108 Aerothermal Test at Calspan-University of Buffalo Research Center (CUBRC), the test flow field calibration. It showed the versatility of the CUBRC Large Energy National Shock Tunnel (LENS) II wind tunnel for an aerothermal test with unique and demanding requirements. CFD analyses were used effectively to extend the test range at the low end of the Mach range. It demonstrated how ground test facility and CFD synergy can be utilitzed iteratively to enhance the confidence in the fedility of both tools. It addressed the lingering concerns of the aerothermal community on use of inpulse facility and CFD analysis. At the conclusion of the test program, members from the NASA Marshall (MSFC), CUBRC and USA (United Space Alliance) Consultants (The Grey Beards) were asked to independently verify the flight scaling data generated by Boeing for flight certification of the re-designed external tank (ET) components. The blind test comparison showed very good results.

FDNS CFD Code Benchmark for RBCC Ejector Mode Operation: Continuing Toward Dual Rocket Effects

NASA Technical Reports Server (NTRS)

West, Jeff; Ruf, Joseph H.; Turner, James E. (Technical Monitor)

2000-01-01

Computational Fluid Dynamics (CFD) analysis results are compared with benchmark quality test data from the Propulsion Engineering Research Center's (PERC) Rocket Based Combined Cycle (RBCC) experiments to verify fluid dynamic code and application procedures. RBCC engine flowpath development will rely on CFD applications to capture the multi -dimensional fluid dynamic interactions and to quantify their effect on the RBCC system performance. Therefore, the accuracy of these CFD codes must be determined through detailed comparisons with test data. The PERC experiments build upon the well-known 1968 rocket-ejector experiments of Odegaard and Stroup by employing advanced optical and laser based diagnostics to evaluate mixing and secondary combustion. The Finite Difference Navier Stokes (FDNS) code [2] was used to model the fluid dynamics of the PERC RBCC ejector mode configuration. Analyses were performed for the Diffusion and Afterburning (DAB) test conditions at the 200-psia thruster operation point, Results with and without downstream fuel injection are presented.

Aerodynamic study of time-trial helmets in cycling racing using CFD analysis.

PubMed

Beaumont, F; Taiar, R; Polidori, G; Trenchard, H; Grappe, F

2018-01-23

The aerodynamic drag of three different time-trial cycling helmets was analyzed numerically for two different cyclist head positions. Computational Fluid Dynamics (CFD) methods were used to investigate the detailed airflow patterns around the cyclist for a constant velocity of 15 m/s without wind. The CFD simulations have focused on the aerodynamic drag effects in terms of wall shear stress maps and pressure coefficient distributions on the cyclist/helmet system. For a given head position, the helmet shape, by itself, obtained a weak effect on a cyclist's aerodynamic performance (<1.5%). However, by varying head position, a cyclist significantly influences aerodynamic performance; the maximum difference between both positions being about 6.4%. CFD results have also shown that both helmet shape and head position significantly influence drag forces, pressure and wall shear stress distributions on the whole cyclist's body due to the change in the near-wake behavior and in location of corresponding separation and attachment areas around the cyclist. Copyright © 2017 Elsevier Ltd. All rights reserved.

Aerodynamic Synthesis of a Centrifugal Impeller Using CFD and Measurements

NASA Technical Reports Server (NTRS)

Larosiliere, L. M.; Skoch, G. J.; Prahst, P. S.

1997-01-01

The performance and flow structure in an unshrouded impeller of approximately 4:1 pressure ratio is synthesized on the basis of a detailed analysis of 3D viscous CFD results and aerodynamic measurements. A good data match was obtained between CFD and measurements using laser anemometry and pneumatic probes. This solidified the role of the CFD model as a reliable representation of the impeller internal flow structure and integrated performance. Results are presented showing the loss production and secondary flow structure in the impeller. The results indicate that while the overall impeller efficiency is high, the impeller shroud static pressure recovery potential is underdeveloped leading to a performance degradation in the downstream diffusing element. Thus, a case is made for a follow-on impeller parametric design study to improve the flow quality. A strategy for aerodynamic performance enhancement is outlined and an estimate of the gain in overall impeller efficiency that might be realized through improvements to the relative diffusion process is provided.

Integrating Multibody Simulation and CFD: toward Complex Multidisciplinary Design Optimization

NASA Astrophysics Data System (ADS)

Pieri, Stefano; Poloni, Carlo; Mühlmeier, Martin

This paper describes the use of integrated multidisciplinary analysis and optimization of a race car model on a predefined circuit. The objective is the definition of the most efficient geometric configuration that can guarantee the lowest lap time. In order to carry out this study it has been necessary to interface the design optimization software modeFRONTIER with the following softwares: CATIA v5, a three dimensional CAD software, used for the definition of the parametric geometry; A.D.A.M.S./Motorsport, a multi-body dynamic simulation software; IcemCFD, a mesh generator, for the automatic generation of the CFD grid; CFX, a Navier-Stokes code, for the fluid-dynamic forces prediction. The process integration gives the possibility to compute, for each geometrical configuration, a set of aerodynamic coefficients that are then used in the multiboby simulation for the computation of the lap time. Finally an automatic optimization procedure is started and the lap-time minimized. The whole process is executed on a Linux cluster running CFD simulations in parallel.

Numerical Prediction of the Influence of Thrust Reverser on Aeroengine's Aerodynamic Stability

NASA Astrophysics Data System (ADS)

Zhiqiang, Wang; Xigang, Shen; Jun, Hu; Xiang, Gao; Liping, Liu

2017-11-01

A numerical method was developed to predict the aerodynamic stability of a high bypass ratio turbofan engine, at the landing stage of a large transport aircraft, when the thrust reverser was deployed. 3D CFD simulation and 2D aeroengine aerodynamic stability analysis code were performed in this work, the former is to achieve distortion coefficient for the analysis of engine stability. The 3D CFD simulation was divided into two steps, the single engine calculation and the integrated aircraft and engine calculation. Results of the CFD simulation show that with the decreasing of relative wind Mach number, the engine inlet will suffer more severe flow distortion. The total pressure and total temperature distortion coefficients at the inlet of the engines were obtained from the results of the numerical simulation. Then an aeroengine aerodynamic stability analysis program was used to quantitatively analyze the aerodynamic stability of the high bypass ratio turbofan engine. The results of the stability analysis show that the engine can work stably, when the reverser flow is re-ingested. But the anti-distortion ability of the booster is weaker than that of the fan and high pressure compressor. It is a weak link of engine stability.

CFD Analysis of an Installation Used to Measure the Skin-Friction Penalty of Acoustic Treatments

NASA Technical Reports Server (NTRS)

Spalart, Philippe R.; Garbaruk, Andrey; Howerton, Brian M.

2017-01-01

There is a drive to devise acoustic treatments with reduced skin-friction and therefore fuel-burn penalty for engine nacelles on commercial airplanes. The studies have been experimental, and the effects on skin-friction are deduced from measurements of the pressure drop along a duct. We conduct a detailed CFD analysis of the installation, for two purposes. The first is to predict the effects of the finite size of the rig, including its near-square cross-section and the moderate length of the treated patch; this introduces transient and blockage effects, which have not been included so far in the analysis. In addition, the flow is compressible, so that even with homogeneous surface conditions, it is not homogeneous in the streamwise direction. The second purpose is to extract an effective sand-grain roughness size for a particular liner, which in turn can be used in a CFD analysis of the aircraft, leading to actual predictions of the effect of acoustic treatments on fuel burn in service. The study is entirely based on classical turbulence models, with an appropriate modification for effective roughness effects, rather than directly modeling the liners.

Marshall Space Flight Center CFD overview

NASA Technical Reports Server (NTRS)

Schutzenhofer, Luke A.

1989-01-01

Computational Fluid Dynamics (CFD) activities at Marshall Space Flight Center (MSFC) have been focused on hardware specific and research applications with strong emphasis upon benchmark validation. The purpose here is to provide insight into the MSFC CFD related goals, objectives, current hardware related CFD activities, propulsion CFD research efforts and validation program, future near-term CFD hardware related programs, and CFD expectations. The current hardware programs where CFD has been successfully applied are the Space Shuttle Main Engines (SSME), Alternate Turbopump Development (ATD), and Aeroassist Flight Experiment (AFE). For the future near-term CFD hardware related activities, plans are being developed that address the implementation of CFD into the early design stages of the Space Transportation Main Engine (STME), Space Transportation Booster Engine (STBE), and the Environmental Control and Life Support System (ECLSS) for the Space Station. Finally, CFD expectations in the design environment will be delineated.

Characterization of Deficiencies in the Frequency Domain Forced Response Analysis Technique for Turbine Bladed Disks

NASA Technical Reports Server (NTRS)

Brown, Andrew M.; Schmauch, Preston

2012-01-01

Turbine blades in rocket and jet engine turbomachinery experience enormous harmonic loading conditions. These loads result from the integer number of upstream and downstream stator vanes as well as the other turbine stages. The standard technique for forced response analysis to assess structural integrity is to decompose a CFD generated flow field into its harmonic components, and to then perform a frequency response analysis at the problematic natural frequencies. Recent CFD analysis and water-flow testing at NASA/MSFC, though, indicates that this technique may miss substantial harmonic and non-harmonic excitation sources that become present in complex flows. These complications suggest the question of whether frequency domain analysis is capable of capturing the excitation content sufficiently. Two studies comparing frequency response analysis with transient response analysis, therefore, have been performed. The first is of a bladed disk with each blade modeled by simple beam elements. It was hypothesized that the randomness and other variation from the standard harmonic excitation would reduce the blade structural response, but the results showed little reduction. The second study was of a realistic model of a bladed-disk excited by the same CFD used in the J2X engine program. The results showed that the transient analysis results were up to 10% higher for "clean" nodal diameter excitations and six times larger for "messy" excitations, where substantial Fourier content around the main harmonic exists.

Combining ray tracing and CFD in the thermal analysis of a parabolic dish tubular cavity receiver

NASA Astrophysics Data System (ADS)

Craig, Ken J.; Marsberg, Justin; Meyer, Josua P.

2016-05-01

This paper describes the numerical evaluation of a tubular receiver used in a dish Brayton cycle. In previous work considering the use of Computational Fluid Dynamics (CFD) to perform the calculation of the absorbed radiation from the parabolic dish into the cavity as well as the resulting conjugate heat transfer, it was shown that an axi-symmetric model of the dish and receiver absorbing surfaces was useful in reducing the computational cost required for a full 3-D discrete ordinates solution, but concerns remained about its accuracy. To increase the accuracy, the Monte Carlo ray tracer SolTrace is used to perform the calculation of the absorbed radiation profile to be used in the conjugate heat transfer CFD simulation. The paper describes an approach for incorporating a complex geometry like a tubular receiver generated using CFD software into SolTrace. The results illustrate the variation of CFD mesh density that translates into the number of elements in SolTrace as well as the number of rays used in the Monte Carlo approach and their effect on obtaining a resolution-independent solution. The conjugate heat transfer CFD simulation illustrates the effect of applying the SolTrace surface heat flux profile solution as a volumetric heat source to heat up the air inside the tube. Heat losses due to convection and thermal re-radiation are also determined as a function of different tube absorptivities.

Development and Assessment of CFD Models Including a Supplemental Program Code for Analyzing Buoyancy-Driven Flows Through BWR Fuel Assemblies in SFP Complete LOCA Scenarios

NASA Astrophysics Data System (ADS)

Artnak, Edward Joseph, III

This work seeks to illustrate the potential benefits afforded by implementing aspects of fluid dynamics, especially the latest computational fluid dynamics (CFD) modeling approach, through numerical experimentation and the traditional discipline of physical experimentation to improve the calibration of the severe reactor accident analysis code, MELCOR, in one of several spent fuel pool (SFP) complete loss-ofcoolant accident (LOCA) scenarios. While the scope of experimental work performed by Sandia National Laboratories (SNL) extends well beyond that which is reasonably addressed by our allotted resources and computational time in accordance with initial project allocations to complete the report, these simulated case trials produced a significant array of supplementary high-fidelity solutions and hydraulic flow-field data in support of SNL research objectives. Results contained herein show FLUENT CFD model representations of a 9x9 BWR fuel assembly in conditions corresponding to a complete loss-of-coolant accident scenario. In addition to the CFD model developments, a MATLAB based controlvolume model was constructed to independently assess the 9x9 BWR fuel assembly under similar accident scenarios. The data produced from this work show that FLUENT CFD models are capable of resolving complex flow fields within a BWR fuel assembly in the realm of buoyancy-induced mass flow rates and that characteristic hydraulic parameters from such CFD simulations (or physical experiments) are reasonably employed in corresponding constitutive correlations for developing simplified numerical models of comparable solution accuracy.

Clinical applications of image-based airway computational fluid dynamics: assessment of inhalation medication and endobronchial devices

NASA Astrophysics Data System (ADS)

De Backer, Jan W.; Vos, Wim G.; Germonpré, Paul; Salgado, Rodrigo; Parizel, Paul M.; De Backer, Wilfried

2009-02-01

Computational fluid dynamics (CFD) is a technique that is used increasingly in the biomedical field. Solving the flow equations numerically provides a convenient way to assess the efficiency of therapies and devices, ranging from cardiovascular stents and heart valves to hemodialysis workflows. Also in the respiratory field CFD has gained increasing interest, especially through the combination of three dimensional image reconstruction which results in highend patient-specific models. This paper provides an overview of clinical applications of CFD through image based modeling, resulting from recent studies performed in our center. We focused on two applications: assessment of the efficiency of inhalation medication and analysis of endobronchial valve placement. In the first application we assessed the mode of action of a novel bronchodilator in 10 treated patients and 4 controls. We assessed the local volume increase and resistance change based on the combination of imaging and CFD. We found a good correlation between the changes in volume and resistance coming from the CFD results and the clinical tests. In the second application we assessed the placement and effect of one way endobronchial valves on respiratory function in 6 patients. We found a strong patientspecific result of the therapy where in some patients the therapy resulted in complete atelectasis of the target lobe while in others the lobe remained inflated. We concluded from these applications that CFD can provide a better insight into clinically relevant therapies.

Visual Environments for CFD Research

NASA Technical Reports Server (NTRS)

Watson, Val; George, Michael W. (Technical Monitor)

1994-01-01

This viewgraph presentation gives an overview of the visual environments for computational fluid dynamics (CFD) research. It includes details on critical needs from the future computer environment, features needed to attain this environment, prospects for changes in and the impact of the visualization revolution on the human-computer interface, human processing capabilities, limits of personal environment and the extension of that environment with computers. Information is given on the need for more 'visual' thinking (including instances of visual thinking), an evaluation of the alternate approaches for and levels of interactive computer graphics, a visual analysis of computational fluid dynamics, and an analysis of visualization software.

Use of computational fluid dynamics in respiratory medicine.

PubMed

Fernández Tena, Ana; Casan Clarà, Pere

2015-06-01

Computational Fluid Dynamics (CFD) is a computer-based tool for simulating fluid movement. The main advantages of CFD over other fluid mechanics studies include: substantial savings in time and cost, the analysis of systems or conditions that are very difficult to simulate experimentally (as is the case of the airways), and a practically unlimited level of detail. We used the Ansys-Fluent CFD program to develop a conducting airway model to simulate different inspiratory flow rates and the deposition of inhaled particles of varying diameters, obtaining results consistent with those reported in the literature using other procedures. We hope this approach will enable clinicians to further individualize the treatment of different respiratory diseases. Copyright © 2014 SEPAR. Published by Elsevier Espana. All rights reserved.

Validation of a CFD Methodology for Variable Speed Power Turbine Relevant Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; McVetta, Ashlie B.

2013-01-01

Analysis tools are needed to investigate aerodynamic performance of Variable-Speed Power Turbines (VSPT) for rotorcraft applications. The VSPT operates at low Reynolds numbers (transitional flow) and over a wide range of incidence. Previously, the capability of a published three-equation turbulence model to predict accurately the transition location for three-dimensional heat transfer problems was assessed. In this paper, the results of a post-diction exercise using a three-dimensional flow in a transonic linear cascade comprising VSPT blading are presented. The measured blade pressure distributions and exit total pressure and flow angles for two incidence angles corresponding to cruise (i = 5.8deg) and takeoff (i = -36.7deg) were used for this study. For the higher loading condition of cruise and the negative incidence condition of takeoff, overall agreement with data may be considered satisfactory but areas of needed improvement are also indicated.

NASA. Marshall Space Flight Center Hydrostatic Bearing Activities

NASA Technical Reports Server (NTRS)

Benjamin, Theodore G.

1991-01-01

The basic approach for analyzing hydrostatic bearing flows at the Marshall Space Flight Center (MSFC) is briefly discussed. The Hydrostatic Bearing Team has responsibility for assessing and evaluating flow codes; evaluating friction, ignition, and galling effects; evaluating wear; and performing tests. The Office of Aerospace and Exploration Technology Turbomachinery Seals Tasks consist of tests and analysis. The MSFC in-house analyses utilize one-dimensional bulk-flow codes. Computational fluid dynamics (CFD) analysis is used to enhance understanding of bearing flow physics or to perform parametric analysis that are outside the bulk flow database. As long as the bulk flow codes are accurate enough for most needs, they will be utilized accordingly and will be supported by CFD analysis on an as-needed basis.

14 CFR Sec. 19-5 - Air transport traffic and capacity elements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... passenger-miles CFD * 210 Revenue cargo tons enplaned CFD * 217 Enplaned freight M 219 Enplaned mail M 230 Revenue tons transported CFD * 237 Transported freight S 239 Transported mail S 240 Revenue ton-miles CFD * 241 Revenue ton-miles passenger CFD * 247 Revenue ton-miles freight CFD * 249 Revenue ton-miles mail...

14 CFR 298.61 - Reporting of traffic statistics.

Code of Federal Regulations, 2012 CFR

2012-01-01

... S 140 Revenue passenger-miles CFD* 210 Revenue cargo tons enplaned CFD* 217 Enplaned freight M 219 Enplaned mail M 230 Revenue tons transported CFD* 237 Transported freight S 239 Transported mail S 240 Revenue ton-miles CFD* 241 Revenue ton-miles passenger CFD* 247 Revenue ton-miles freight CFD* 249 Revenue...

14 CFR 298.61 - Reporting of traffic statistics.

Code of Federal Regulations, 2014 CFR

2014-01-01

... S 140 Revenue passenger-miles CFD* 210 Revenue cargo tons enplaned CFD* 217 Enplaned freight M 219 Enplaned mail M 230 Revenue tons transported CFD* 237 Transported freight S 239 Transported mail S 240 Revenue ton-miles CFD* 241 Revenue ton-miles passenger CFD* 247 Revenue ton-miles freight CFD* 249 Revenue...

14 CFR 19-5 - Air transport traffic and capacity elements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... passenger-miles CFD * 210 Revenue cargo tons enplaned CFD * 217 Enplaned freight M 219 Enplaned mail M 230 Revenue tons transported CFD * 237 Transported freight S 239 Transported mail S 240 Revenue ton-miles CFD * 241 Revenue ton-miles passenger CFD * 247 Revenue ton-miles freight CFD * 249 Revenue ton-miles mail...

14 CFR 298.61 - Reporting of traffic statistics.

Code of Federal Regulations, 2013 CFR

2013-01-01

... S 140 Revenue passenger-miles CFD* 210 Revenue cargo tons enplaned CFD* 217 Enplaned freight M 219 Enplaned mail M 230 Revenue tons transported CFD* 237 Transported freight S 239 Transported mail S 240 Revenue ton-miles CFD* 241 Revenue ton-miles passenger CFD* 247 Revenue ton-miles freight CFD* 249 Revenue...

14 CFR Sec. 19-5 - Air transport traffic and capacity elements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... passenger-miles CFD * 210 Revenue cargo tons enplaned CFD * 217 Enplaned freight M 219 Enplaned mail M 230 Revenue tons transported CFD * 237 Transported freight S 239 Transported mail S 240 Revenue ton-miles CFD * 241 Revenue ton-miles passenger CFD * 247 Revenue ton-miles freight CFD * 249 Revenue ton-miles mail...

Design of A Cyclone Separator Using Approximation Method

NASA Astrophysics Data System (ADS)

Sin, Bong-Su; Choi, Ji-Won; Lee, Kwon-Hee

2017-12-01

A Separator is a device installed in industrial applications to separate mixed objects. The separator of interest in this research is a cyclone type, which is used to separate a steam-brine mixture in a geothermal plant. The most important performance of the cyclone separator is the collection efficiency. The collection efficiency in this study is predicted by performing the CFD (Computational Fluid Dynamics) analysis. This research defines six shape design variables to maximize the collection efficiency. Thus, the collection efficiency is set up as the objective function in optimization process. Since the CFD analysis requires a lot of calculation time, it is impossible to obtain the optimal solution by linking the gradient-based optimization algorithm. Thus, two approximation methods are introduced to obtain an optimum design. In this process, an L18 orthogonal array is adopted as a DOE method, and kriging interpolation method is adopted to generate the metamodel for the collection efficiency. Based on the 18 analysis results, the relative importance of each variable to the collection efficiency is obtained through the ANOVA (analysis of variance). The final design is suggested considering the results obtained from two optimization methods. The fluid flow analysis of the cyclone separator is conducted by using the commercial CFD software, ANSYS-CFX.

Numerical Analysis of 2-D and 3-D MHD Flows Relevant to Fusion Applications

DOE PAGES

Khodak, Andrei

2017-08-21

Here, the analysis of many fusion applications such as liquid-metal blankets requires application of computational fluid dynamics (CFD) methods for electrically conductive liquids in geometrically complex regions and in the presence of a strong magnetic field. A current state of the art general purpose CFD code allows modeling of the flow in complex geometric regions, with simultaneous conjugated heat transfer analysis in liquid and surrounding solid parts. Together with a magnetohydrodynamics (MHD) capability, the general purpose CFD code will be a valuable tool for the design and optimization of fusion devices. This paper describes an introduction of MHD capability intomore » the general purpose CFD code CFX, part of the ANSYS Workbench. The code was adapted for MHD problems using a magnetic induction approach. CFX allows introduction of user-defined variables using transport or Poisson equations. For MHD adaptation of the code three additional transport equations were introduced for the components of the magnetic field, in addition to the Poisson equation for electric potential. The Lorentz force is included in the momentum transport equation as a source term. Fusion applications usually involve very strong magnetic fields, with values of the Hartmann number of up to tens of thousands. In this situation a system of MHD equations become very rigid with very large source terms and very strong variable gradients. To increase system robustness, special measures were introduced during the iterative convergence process, such as linearization using source coefficient for momentum equations. The MHD implementation in general purpose CFD code was tested against benchmarks, specifically selected for liquid-metal blanket applications. Results of numerical simulations using present implementation closely match analytical solutions for a Hartmann number of up to 1500 for a 2-D laminar flow in the duct of square cross section, with conducting and nonconducting walls. Results for a 3-D test case are also included.« less

Numerical analysis of air-flow and temperature field in a passenger car compartment

NASA Astrophysics Data System (ADS)

Kamar, Haslinda Mohamed; Kamsah, Nazri; Mohammad Nor, Ahmad Miski

2012-06-01

This paper presents a numerical study on the temperature field inside a passenger's compartment of a Proton Wira saloon car using computational fluid dynamics (CFD) method. The main goal is to investigate the effects of different glazing types applied onto the front and rear windscreens of the car on the distribution of air-temperature inside the passenger compartment in the steady-state conditions. The air-flow condition in the passenger's compartment is also investigated. Fluent CFD software was used to develop a three-dimensional symmetrical model of the passenger's compartment. Simplified representations of the driver and one rear passenger were incorporated into the CFD model of the passenger's compartment. Two types of glazing were considered namely clear insulated laminated tint (CIL) with a shading coefficient of 0.78 and green insulated laminate tint (GIL) with a shading coefficient of 0.5. Results of the CFD analysis were compared with those obtained when the windscreens are made up of clear glass having a shading coefficient of 0.86. Results of the CFD analysis show that for a given glazing material, the temperature of the air around the driver is slightly lower than the air around the rear passenger. Also, the use of GIL glazing material on both the front and rear windscreens significantly reduces the air temperature inside the passenger's compartment of the car. This contributes to a better thermal comfort condition to the occupants. Swirling air flow condition occurs in the passenger compartment. The air-flow intensity and velocity are higher along the side wall of the passenger's compartment compared to that along the middle section of the compartment. It was also found that the use of glazing materials on both the front and rear windscreen has no significant effects on the air-flow condition inside the passenger's compartment of the car.

Numerical Analysis of 2-D and 3-D MHD Flows Relevant to Fusion Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khodak, Andrei

Here, the analysis of many fusion applications such as liquid-metal blankets requires application of computational fluid dynamics (CFD) methods for electrically conductive liquids in geometrically complex regions and in the presence of a strong magnetic field. A current state of the art general purpose CFD code allows modeling of the flow in complex geometric regions, with simultaneous conjugated heat transfer analysis in liquid and surrounding solid parts. Together with a magnetohydrodynamics (MHD) capability, the general purpose CFD code will be a valuable tool for the design and optimization of fusion devices. This paper describes an introduction of MHD capability intomore » the general purpose CFD code CFX, part of the ANSYS Workbench. The code was adapted for MHD problems using a magnetic induction approach. CFX allows introduction of user-defined variables using transport or Poisson equations. For MHD adaptation of the code three additional transport equations were introduced for the components of the magnetic field, in addition to the Poisson equation for electric potential. The Lorentz force is included in the momentum transport equation as a source term. Fusion applications usually involve very strong magnetic fields, with values of the Hartmann number of up to tens of thousands. In this situation a system of MHD equations become very rigid with very large source terms and very strong variable gradients. To increase system robustness, special measures were introduced during the iterative convergence process, such as linearization using source coefficient for momentum equations. The MHD implementation in general purpose CFD code was tested against benchmarks, specifically selected for liquid-metal blanket applications. Results of numerical simulations using present implementation closely match analytical solutions for a Hartmann number of up to 1500 for a 2-D laminar flow in the duct of square cross section, with conducting and nonconducting walls. Results for a 3-D test case are also included.« less

Validation of a Pressure-Based Combustion Simulation Tool Using a Single Element Injector Test Problem

NASA Technical Reports Server (NTRS)

Thakur, Siddarth; Wright, Jeffrey

2006-01-01

The traditional design and analysis practice for advanced propulsion systems, particularly chemical rocket engines, relies heavily on expensive full-scale prototype development and testing. Over the past decade, use of high-fidelity analysis and design tools such as CFD early in the product development cycle has been identified as one way to alleviate testing costs and to develop these devices better, faster and cheaper. Increased emphasis is being placed on developing and applying CFD models to simulate the flow field environments and performance of advanced propulsion systems. This necessitates the development of next generation computational tools which can be used effectively and reliably in a design environment by non-CFD specialists. A computational tool, called Loci-STREAM is being developed for this purpose. It is a pressure-based, Reynolds-averaged Navier-Stokes (RANS) solver for generalized unstructured grids, which is designed to handle all-speed flows (incompressible to hypersonic) and is particularly suitable for solving multi-species flow in fixed-frame combustion devices. Loci-STREAM integrates proven numerical methods for generalized grids and state-of-the-art physical models in a novel rule-based programming framework called Loci which allows: (a) seamless integration of multidisciplinary physics in a unified manner, and (b) automatic handling of massively parallel computing. The objective of the ongoing work is to develop a robust simulation capability for combustion problems in rocket engines. As an initial step towards validating this capability, a model problem is investigated in the present study which involves a gaseous oxygen/gaseous hydrogen (GO2/GH2) shear coaxial single element injector, for which experimental data are available. The sensitivity of the computed solutions to grid density, grid distribution, different turbulence models, and different near-wall treatments is investigated. A refined grid, which is clustered in the vicinity of the solid walls as well as the flame, is used to obtain a steady state solution which may be considered as the best solution attainable with the steady-state RANS methodology. From a design point of view, quick turnaround times are desirable; with this in mind, coarser grids are also employed and the resulting solutions are evaluated with respect to the fine grid solution.

A parallel offline CFD and closed-form approximation strategy for computationally efficient analysis of complex fluid flows

NASA Astrophysics Data System (ADS)

Allphin, Devin

Computational fluid dynamics (CFD) solution approximations for complex fluid flow problems have become a common and powerful engineering analysis technique. These tools, though qualitatively useful, remain limited in practice by their underlying inverse relationship between simulation accuracy and overall computational expense. While a great volume of research has focused on remedying these issues inherent to CFD, one traditionally overlooked area of resource reduction for engineering analysis concerns the basic definition and determination of functional relationships for the studied fluid flow variables. This artificial relationship-building technique, called meta-modeling or surrogate/offline approximation, uses design of experiments (DOE) theory to efficiently approximate non-physical coupling between the variables of interest in a fluid flow analysis problem. By mathematically approximating these variables, DOE methods can effectively reduce the required quantity of CFD simulations, freeing computational resources for other analytical focuses. An idealized interpretation of a fluid flow problem can also be employed to create suitably accurate approximations of fluid flow variables for the purposes of engineering analysis. When used in parallel with a meta-modeling approximation, a closed-form approximation can provide useful feedback concerning proper construction, suitability, or even necessity of an offline approximation tool. It also provides a short-circuit pathway for further reducing the overall computational demands of a fluid flow analysis, again freeing resources for otherwise unsuitable resource expenditures. To validate these inferences, a design optimization problem was presented requiring the inexpensive estimation of aerodynamic forces applied to a valve operating on a simulated piston-cylinder heat engine. The determination of these forces was to be found using parallel surrogate and exact approximation methods, thus evidencing the comparative benefits of this technique. For the offline approximation, latin hypercube sampling (LHS) was used for design space filling across four (4) independent design variable degrees of freedom (DOF). Flow solutions at the mapped test sites were converged using STAR-CCM+ with aerodynamic forces from the CFD models then functionally approximated using Kriging interpolation. For the closed-form approximation, the problem was interpreted as an ideal 2-D converging-diverging (C-D) nozzle, where aerodynamic forces were directly mapped by application of the Euler equation solutions for isentropic compression/expansion. A cost-weighting procedure was finally established for creating model-selective discretionary logic, with a synthesized parallel simulation resource summary provided.

Dependency of the Reynolds number on the water flow through the perforated tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Závodný, Zdenko, E-mail: zdenko.zavodny@stuba.sk; Bereznai, Jozef, E-mail: jozef.bereznai@stuba.sk; Urban, František

Safe and effective loading of nuclear reactor fuel assemblies demands qualitative and quantitative analysis of the relationship between the coolant temperature in the fuel assembly outlet, measured by the thermocouple, and the mean coolant temperature profile in the thermocouple plane position. It is not possible to perform the analysis directly in the reactor, so it is carried out using measurements on the physical model, and the CFD fuel assembly coolant flow models. The CFD models have to be verified and validated in line with the temperature and velocity profile obtained from the measurements of the cooling water flowing in themore » physical model of the fuel assembly. Simplified physical model with perforated central tube and its validated CFD model serve to design of the second physical model of the fuel assembly of the nuclear reactor VVER 440. Physical model will be manufactured and installed in the laboratory of the Institute of Energy Machines, Faculty of Mechanical Engineering of the Slovak University of Technology in Bratislava.« less

CFD analysis of a rotary kiln using for plaster production and discussion of the effects of flue gas recirculation application

NASA Astrophysics Data System (ADS)

Gürtürk, Mert; Oztop, Hakan F.; Pambudi, Nugroho Agung

2018-04-01

In this study, the CFD analysis of the rotary kiln is carried out for examining effects of various parameters on energy consumption and efficiency of the rotary kiln. The flue gas recirculation using in many applications is a useful method for combusting of fuel unburned in the flue gas. Also, effects of flue gas recirculation on the combusting of fuel, operating temperature and efficiency of the rotary kiln are discussed in this study. The rotary kiln, which is considered in this study, is used in plaster plant. Two different CFD models were created and these models are compared according to many parameters such as temperature distribution, mixture fraction, the mass fraction of O2, CO, CO and CH4 in the combustion chamber. It is found that the plaster plant has a great potential for an increase in energy efficiency. Results obtained for producers of rotary kiln and burner will be useful for determining better design parameters.

Design optimization of hydraulic turbine draft tube based on CFD and DOE method

NASA Astrophysics Data System (ADS)

Nam, Mun chol; Dechun, Ba; Xiangji, Yue; Mingri, Jin

2018-03-01

In order to improve performance of the hydraulic turbine draft tube in its design process, the optimization for draft tube is performed based on multi-disciplinary collaborative design optimization platform by combining the computation fluid dynamic (CFD) and the design of experiment (DOE) in this paper. The geometrical design variables are considered as the median section in the draft tube and the cross section in its exit diffuser and objective function is to maximize the pressure recovery factor (Cp). Sample matrixes required for the shape optimization of the draft tube are generated by optimal Latin hypercube (OLH) method of the DOE technique and their performances are evaluated through computational fluid dynamic (CFD) numerical simulation. Subsequently the main effect analysis and the sensitivity analysis of the geometrical parameters of the draft tube are accomplished. Then, the design optimization of the geometrical design variables is determined using the response surface method. The optimization result of the draft tube shows a marked performance improvement over the original.

Development and Analysis of a Bi-Directional Tidal Turbine

DTIC Science & Technology

2012-03-01

commercial CFD software ANSYS CFX was utilized to build a turbine map. The basic turbine map was developed for a 25 blade bi-axial turbine under...directional turbine created for this purpose. In the present study, the commercial CFD software ANSYS CFX was utilized to build a turbine map. The...sheath C. PROBLEM SPECIFICATIONS AND BOUNDARY CONDITIONS The simulation definition was created using ANSYS CFX -Pre. The best measurements to determine

SSME main combustion chamber and nozzle flowfield analysis

NASA Technical Reports Server (NTRS)

Farmer, R. C.; Wang, T. S.; Smith, S. D.; Prozan, R. J.

1986-01-01

An investigation is presented of the computational fluid dynamics (CFD) tools which would accurately analyze main combustion chamber and nozzle flow. The importance of combustion phenomena and local variations in mixture ratio are fully appreciated; however, the computational aspects of the gas dynamics involved were the sole issues addressed. The CFD analyses made are first compared with conventional nozzle analyses to determine the accuracy for steady flows, and then transient analyses are discussed.

Conversion of Component-Based Point Definition to VSP Model and Higher Order Meshing

NASA Technical Reports Server (NTRS)

Ordaz, Irian

2011-01-01

Vehicle Sketch Pad (VSP) has become a powerful conceptual and parametric geometry tool with numerous export capabilities for third-party analysis codes as well as robust surface meshing capabilities for computational fluid dynamics (CFD) analysis. However, a capability gap currently exists for reconstructing a fully parametric VSP model of a geometry generated by third-party software. A computer code called GEO2VSP has been developed to close this gap and to allow the integration of VSP into a closed-loop geometry design process with other third-party design tools. Furthermore, the automated CFD surface meshing capability of VSP are demonstrated for component-based point definition geometries in a conceptual analysis and design framework.

Experimental and Computational Analysis of Unidirectional Flow Through Stirling Engine Heater Head

NASA Technical Reports Server (NTRS)

Wilson, Scott D.; Dyson, Rodger W.; Tew, Roy C.; Demko, Rikako

2006-01-01

A high efficiency Stirling Radioisotope Generator (SRG) is being developed for possible use in long-duration space science missions. NASA s advanced technology goals for next generation Stirling convertors include increasing the Carnot efficiency and percent of Carnot efficiency. To help achieve these goals, a multi-dimensional Computational Fluid Dynamics (CFD) code is being developed to numerically model unsteady fluid flow and heat transfer phenomena of the oscillating working gas inside Stirling convertors. In the absence of transient pressure drop data for the zero mean oscillating multi-dimensional flows present in the Technology Demonstration Convertors on test at NASA Glenn Research Center, unidirectional flow pressure drop test data is used to compare against 2D and 3D computational solutions. This study focuses on tracking pressure drop and mass flow rate data for unidirectional flow though a Stirling heater head using a commercial CFD code (CFD-ACE). The commercial CFD code uses a porous-media model which is dependent on permeability and the inertial coefficient present in the linear and nonlinear terms of the Darcy-Forchheimer equation. Permeability and inertial coefficient were calculated from unidirectional flow test data. CFD simulations of the unidirectional flow test were validated using the porous-media model input parameters which increased simulation accuracy by 14 percent on average.

RotCFD Analysis of the AH-56 Cheyenne Hub Drag

NASA Technical Reports Server (NTRS)

Solis, Eduardo; Bass, Tal A.; Keith, Matthew D.; Oppenheim, Rebecca T.; Runyon, Bryan T.; Veras-Alba, Belen

2016-01-01

In 2016, the U.S. Army Aviation Development Directorate (ADD) conducted tests in the U.S. Army 7- by 10- Foot Wind Tunnel at NASA Ames Research Center of a nonrotating 2/5th-scale AH-56 rotor hub. The objective of the tests was to determine how removing the mechanical control gyro affected the drag. Data for the lift, drag, and pitching moment were recorded for the 4-bladed rotor hub in various hardware configurations, azimuth angles, and angles of attack. Numerical simulations of a selection of the configurations and orientations were then performed, and the results were compared with the test data. To generate the simulation results, the hardware configurations were modeled using Creo and Rhinoceros 5, three-dimensional surface modeling computer-aided design (CAD) programs. The CAD model was imported into Rotorcraft Computational Fluid Dynamics (RotCFD), a computational fluid dynamics (CFD) tool used for analyzing rotor flow fields. RotCFD simulation results were compared with the experimental results of three hardware configurations at two azimuth angles, two angles of attack, and with and without wind tunnel walls. The results help validate RotCFD as a tool for analyzing low-drag rotor hub designs for advanced high-speed rotorcraft concepts. Future work will involve simulating additional hub geometries to reduce drag or tailor to other desired performance levels.

A study on the flow characteristics of a direct drive turbine for energy conversion generation by experiment and CFD

NASA Astrophysics Data System (ADS)

Cho, Y. J.; Zullah, M. A.; Faizal, M.; Choi, Y. D.; Lee, Y. H.

2012-11-01

A variety of technologies has been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales. Due to the complexity of most offshore wave energy devices and their motion response in different sea states, physical tank tests are common practice for WEC design. Full scale tests are also necessary, but are expensive and only considered once the design has been optimized. Computational Fluid Dynamics (CFD) is now recognized as an important complement to traditional physical testing techniques in offshore engineering. Once properly calibrated and validated to the problem, CFD offers a high density of test data and results in a reasonable timescale to assist with design changes and improvements to the device. The purpose of this study is to investigate the performance of a newly developed direct drive hydro turbine (DDT), which will be built in a caisson for extraction of wave energy. Experiments and CFD analysis are conducted to clarify the turbine performance and internal flow characteristics. The results show that commercial CFD code can be applied successfully to the simulation of the wave motion in the water tank. The performance of the turbine for wave energy converter is studied continuously for a ongoing project.

CFD modelling of abdominal aortic aneurysm on hemodynamic loads using a realistic geometry with CT.

PubMed

Soudah, Eduardo; Ng, E Y K; Loong, T H; Bordone, Maurizio; Pua, Uei; Narayanan, Sriram

2013-01-01

The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA) geometric parameters, wall stress shear (WSS), abdominal flow patterns, intraluminal thrombus (ILT), and AAA arterial wall rupture using computational fluid dynamics (CFD). Real AAA 3D models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m(3) and a kinematic viscosity of 4 × 10(-3) Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index ( β ), saccular index ( γ ), deformation diameter ratio ( χ ), and tortuosity index ( ε )) and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation.

Fluid-structure coupling for wind turbine blade analysis using OpenFOAM

NASA Astrophysics Data System (ADS)

Dose, Bastian; Herraez, Ivan; Peinke, Joachim

2015-11-01

Modern wind turbine rotor blades are designed increasingly large and flexible. This structural flexibility represents a problem for the field of Computational Fluid Dynamics (CFD), which is used for accurate load calculations and detailed investigations of rotor aerodynamics. As the blade geometries within CFD simulations are considered stiff, the effect of blade deformation caused by aerodynamic loads cannot be captured by the common CFD approach. Coupling the flow solver with a structural solver can overcome this restriction and enables the investigation of flexible wind turbine blades. For this purpose, a new Finite Element (FE) solver was implemented into the open source CFD code OpenFOAM. Using a beam element formulation based on the Geometrically Exact Beam Theory (GEBT), the structural model can capture geometric non-linearities such as large deformations. Coupled with CFD solvers of the OpenFOAM package, the new framework represents a powerful tool for aerodynamic investigations. In this work, we investigated the aerodynamic performance of a state of the art wind turbine. For different wind speeds, aerodynamic key parameters are evaluated and compared for both, rigid and flexible blade geometries. The present work is funded within the framework of the joint project Smart Blades (0325601D) by the German Federal Ministry for Economic Affairs and Energy (BMWi) under decision of the German Federal Parliament.

Coupled thermal-fluid analysis with flowpath-cavity interaction in a gas turbine engine

NASA Astrophysics Data System (ADS)

Fitzpatrick, John Nathan

This study seeks to improve the understanding of inlet conditions of a large rotor-stator cavity in a turbofan engine, often referred to as the drive cone cavity (DCC). The inlet flow is better understood through a higher fidelity computational fluid dynamics (CFD) modeling of the inlet to the cavity, and a coupled finite element (FE) thermal to CFD fluid analysis of the cavity in order to accurately predict engine component temperatures. Accurately predicting temperature distribution in the cavity is important because temperatures directly affect the material properties including Young's modulus, yield strength, fatigue strength, creep properties. All of these properties directly affect the life of critical engine components. In addition, temperatures cause thermal expansion which changes clearances and in turn affects engine efficiency. The DCC is fed from the last stage of the high pressure compressor. One of its primary functions is to purge the air over the rotor wall to prevent it from overheating. Aero-thermal conditions within the DCC cavity are particularly challenging to predict due to the complex air flow and high heat transfer in the rotating component. Thus, in order to accurately predict metal temperatures a two-way coupled CFD-FE analysis is needed. Historically, when the cavity airflow is modeled for engine design purposes, the inlet condition has been over-simplified for the CFD analysis which impacts the results, particularly in the region around the compressor disc rim. The inlet is typically simplified by circumferentially averaging the velocity field at the inlet to the cavity which removes the effect of pressure wakes from the upstream rotor blades. The way in which these non-axisymmetric flow characteristics affect metal temperatures is not well understood. In addition, a constant air temperature scaled from a previous analysis is used as the simplified cavity inlet air temperature. Therefore, the objectives of this study are: (a) model the DCC cavity with a more physically representative inlet condition while coupling the solid thermal analysis and compressible air flow analysis that includes the fluid velocity, pressure, and temperature fields; (b) run a coupled analysis whose boundary conditions come from computational models, rather than thermocouple data; (c) validate the model using available experimental data; and (d) based on the validation, determine if the model can be used to predict air inlet and metal temperatures for new engine geometries. Verification with experimental results showed that the coupled analysis with the 3D no-bolt CFD model with predictive boundary conditions, over-predicted the HP6 offtake temperature by 16k. The maximum error was an over-prediction of 50k while the average error was 17k. The predictive model with 3D bolts also predicted cavity temperatures with an average error of 17k. For the two CFD models with predicted boundary conditions, the case without bolts performed better than the case with bolts. This is due to the flow errors caused by placing stationary bolts in a rotating reference frame. Therefore it is recommended that this type of analysis only be attempted for drive cone cavities with no bolts or shielded bolts.

Computational study of the heat transfer of an avian egg in a tray.

PubMed

Eren Ozcan, S; Andriessens, S; Berckmans, D

2010-04-01

The development of an embryo in an avian egg depends largely on its temperature. The embryo temperature is affected by its environment and the heat produced by the egg. In this paper, eggshell temperature and the heat transfer characteristics from one egg in a tray toward its environment are studied by means of computational fluid dynamics (CFD). Computational fluid dynamics simulations have the advantage of providing extensive 3-dimensional information on velocity and eggshell temperature distribution around an egg that otherwise is not possible to obtain by experiments. However, CFD results need to be validated against experimental data. The objectives were (1) to find out whether CFD can successfully simulate eggshell temperature from one egg in a tray by comparing to previously conducted experiments, (2) to visualize air flow and air temperature distribution around the egg in a detailed way, and (3) to perform sensitivity analysis on several variables affecting heat transfer. To this end, a CFD model was validated using 2 sets of temperature measurements yielding an effective model. From these simulations, it can be concluded that CFD can effectively be used to analyze heat transfer characteristics and eggshell temperature distribution around an egg. In addition, air flow and temperature distribution around the egg are visualized. It has been observed that temperature differences up to 2.6 degrees C are possible at high heat production (285 mW) and horizontal low flow rates (0.5 m/s). Sensitivity analysis indicates that average eggshell temperature is mainly affected by the inlet air velocity and temperature, flow direction, and the metabolic heat of the embryo and less by the thermal conductivity and emissivity of the egg and thermal emissivity of the tray.

Thermal hydraulic simulations, error estimation and parameter sensitivity studies in Drekar::CFD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Thomas Michael; Shadid, John N.; Pawlowski, Roger P.

2014-01-01

This report describes work directed towards completion of the Thermal Hydraulics Methods (THM) CFD Level 3 Milestone THM.CFD.P7.05 for the Consortium for Advanced Simulation of Light Water Reactors (CASL) Nuclear Hub effort. The focus of this milestone was to demonstrate the thermal hydraulics and adjoint based error estimation and parameter sensitivity capabilities in the CFD code called Drekar::CFD. This milestone builds upon the capabilities demonstrated in three earlier milestones; THM.CFD.P4.02 [12], completed March, 31, 2012, THM.CFD.P5.01 [15] completed June 30, 2012 and THM.CFD.P5.01 [11] completed on October 31, 2012.

Investigation of Navier-Stokes Code Verification and Design Optimization

NASA Technical Reports Server (NTRS)

Vaidyanathan, Rajkumar

2004-01-01

With rapid progress made in employing computational techniques for various complex Navier-Stokes fluid flow problems, design optimization problems traditionally based on empirical formulations and experiments are now being addressed with the aid of computational fluid dynamics (CFD). To be able to carry out an effective CFD-based optimization study, it is essential that the uncertainty and appropriate confidence limits of the CFD solutions be quantified over the chosen design space. The present dissertation investigates the issues related to code verification, surrogate model-based optimization and sensitivity evaluation. For Navier-Stokes (NS) CFD code verification a least square extrapolation (LSE) method is assessed. This method projects numerically computed NS solutions from multiple, coarser base grids onto a freer grid and improves solution accuracy by minimizing the residual of the discretized NS equations over the projected grid. In this dissertation, the finite volume (FV) formulation is focused on. The interplay between the xi concepts and the outcome of LSE, and the effects of solution gradients and singularities, nonlinear physics, and coupling of flow variables on the effectiveness of LSE are investigated. A CFD-based design optimization of a single element liquid rocket injector is conducted with surrogate models developed using response surface methodology (RSM) based on CFD solutions. The computational model consists of the NS equations, finite rate chemistry, and the k-6 turbulence closure. With the aid of these surrogate models, sensitivity and trade-off analyses are carried out for the injector design whose geometry (hydrogen flow angle, hydrogen and oxygen flow areas and oxygen post tip thickness) is optimized to attain desirable goals in performance (combustion length) and life/survivability (the maximum temperatures on the oxidizer post tip and injector face and a combustion chamber wall temperature). A preliminary multi-objective optimization study is carried out using a geometric mean approach. Following this, sensitivity analyses with the aid of variance-based non-parametric approach and partial correlation coefficients are conducted using data available from surrogate models of the objectives and the multi-objective optima to identify the contribution of the design variables to the objective variability and to analyze the variability of the design variables and the objectives. In summary the present dissertation offers insight into an improved coarse to fine grid extrapolation technique for Navier-Stokes computations and also suggests tools for a designer to conduct design optimization study and related sensitivity analyses for a given design problem.

A computational fluid dynamics (CFD) study of WEB-treated aneurysms: Can CFD predict WEB "compression" during follow-up?

PubMed

Caroff, Jildaz; Mihalea, Cristian; Da Ros, Valerio; Yagi, Takanobu; Iacobucci, Marta; Ikka, Léon; Moret, Jacques; Spelle, Laurent

2017-07-01

Recent reports have revealed a worsening of aneurysm occlusion between WEB treatment baseline and angiographic follow-up due to "compression" of the device. We utilized computational fluid dynamics (CFD) in order to determine whether the underlying mechanism of this worsening is flow related. We included data from all consecutive patients treated in our institution with a WEB for unruptured aneurysms located either at the middle cerebral artery or basilar tip. The CFD study was performed using pre-operative 3D rotational angiography. From digital subtraction follow-up angiographies patients were dichotomized into two groups: one with WEB "compression" and one without. We performed statistical analyses to determine a potential correlation between WEB compression and CFD inflow ratio. Between July 2012 and June 2015, a total of 22 unruptured middle cerebral artery or basilar tip aneurysms were treated with a WEB device in our department. Three patients were excluded from the analysis and the mean follow-up period was 17months. Eleven WEBs presented "compression" during follow-up. Interestingly, device "compression" was statistically correlated to the CFD inflow ratio (P=0.018), although not to aneurysm volume, aspect ratio or neck size. The mechanisms underlying the worsening of aneurysm occlusion in WEB-treated patients due to device compression are most likely complex as well as multifactorial. However, it is apparent from our pilot study that a high arterial inflow is, at least, partially involved. Further theoretical and animal research studies are needed to increase our understanding of this phenomenon. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Progress and challenges in the application of artificial intelligence to computational fluid dynamics

NASA Technical Reports Server (NTRS)

Andrews, Alison E.

1987-01-01

An approach to analyzing CFD knowledge-based systems is proposed which is based, in part, on the concept of knowledge-level analysis. Consideration is given to the expert cooling fan design system, the PAN AIR knowledge system, grid adaptation, and expert zonal grid generation. These AI/CFD systems demonstrate that current AI technology can be successfully applied to well-formulated problems that are solved by means of classification or selection of preenumerated solutions.

Ascent Aerodynamic Pressure Distributions on WB001

NASA Technical Reports Server (NTRS)

Vu, B.; Ruf, J.; Canabal, F.; Brunty, J.

1996-01-01

To support the reusable launch vehicle concept study, the aerodynamic data and surface pressure for WB001 were predicted using three computational fluid dynamic (CFD) codes at several flow conditions between code to code and code to aerodynamic database as well as available experimental data. A set of particular solutions have been selected and recommended for use in preliminary conceptual designs. These computational fluid dynamic (CFD) results have also been provided to the structure group for wing loading analysis.

Development of a radial ventricular assist device using numerical predictions and experimental haemolysis.

PubMed

Carswell, Dave; Hilton, Andy; Chan, Chris; McBride, Diane; Croft, Nick; Slone, Avril; Cross, Mark; Foster, Graham

2013-08-01

The objective of this study was to demonstrate the potential of Computational Fluid Dynamics (CFD) simulations in predicting the levels of haemolysis in ventricular assist devices (VADs). Three different prototypes of a radial flow VAD have been examined experimentally and computationally using CFD modelling to assess device haemolysis. Numerical computations of the flow field were computed using a CFD model developed with the use of the commercial software Ansys CFX 13 and a set of custom haemolysis analysis tools. Experimental values for the Normalised Index of Haemolysis (NIH) have been calculated as 0.020 g/100 L, 0.014 g/100 L and 0.0042 g/100 L for the three designs. Numerical analysis predicts an NIH of 0.021 g/100 L, 0.017 g/100 L and 0.0057 g/100 L, respectively. The actual differences between experimental and numerical results vary between 0.0012 and 0.003 g/100 L, with a variation of 5% for Pump 1 and slightly larger percentage differences for the other pumps. The work detailed herein demonstrates how CFD simulation and, more importantly, the numerical prediction of haemolysis may be used as an effective tool in order to help the designers of VADs manage the flow paths within pumps resulting in a less haemolytic device. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Analysis of Temperature and Humidity Field in a New Bulk Tobacco Curing Barn Based on CFD.

PubMed

Bai, Zhipeng; Guo, Duoduo; Li, Shoucang; Hu, Yaohua

2017-01-31

A new structure bulk tobacco curing barn was presented. To study the temperature and humidity field in the new structure tobacco curing barn, a 3D transient computational fluid dynamics (CFD) model was developed using porous medium, species transport, κ-ε turbulence and discrete phase models. The CFD results demonstrated that (1) the temperature and relative humidity predictions were validated by the experimental results, and comparison of simulation results with experimental data showed a fairly close agreement; (2) the temperature of the bottom and inlet area was higher than the top and outlet area, and water vapor concentrated on the top and outlet area in the barn; (3) tobacco loading density and thickness of tobacco leaves had an explicit effect on the temperature distributions in the barn.

SRM Internal Flow Tests and Computational Fluid Dynamic Analysis. Volume 3; Titan, ASRM, and Subscale Motor Analyses

NASA Technical Reports Server (NTRS)

1995-01-01

A computational fluid dynamics (CFD) analysis has been performed on the aft slot region of the Titan 4 Solid Rocket Motor Upgrade (SRMU). This analysis was performed in conjunction with MSFC structural modeling of the propellant grain to determine if the flow field induced stresses would adversely alter the propellant geometry to the extent of causing motor failure. The results of the coupled CFD/stress analysis have shown that there is a continual increase of flow field resistance at the aft slot due to the aft segment propellant grain being progressively moved radially toward the centerline of the motor port. This 'bootstrapping' effect between grain radial movement and internal flow resistance is conducive to causing a rapid motor failure.

Aerothermodynamic Flight Simulation Capabilities for Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Miller, Charles G.

1998-01-01

Aerothermodynamics, encompassing aerodynamics, aeroheating, and fluid dynamics and physical processes, is the genesis for the design and development of advanced space transportation vehicles and provides crucial information to other disciplines such as structures, materials, propulsion, avionics, and guidance, navigation and control. Sources of aerothermodynamic information are ground-based facilities, Computational Fluid Dynamic (CFD) and engineering computer codes, and flight experiments. Utilization of this aerothermodynamic triad provides the optimum aerothermodynamic design to safely satisfy mission requirements while reducing design conservatism, risk and cost. The iterative aerothermodynamic process for initial screening/assessment of aerospace vehicle concepts, optimization of aerolines to achieve/exceed mission requirements, and benchmark studies for final design and establishment of the flight data book are reviewed. Aerothermodynamic methodology centered on synergism between ground-based testing and CFD predictions is discussed for various flow regimes encountered by a vehicle entering the Earth s atmosphere from low Earth orbit. An overview of the resources/infrastructure required to provide accurate/creditable aerothermodynamic information in a timely manner is presented. Impacts on Langley s aerothermodynamic capabilities due to recent programmatic changes such as Center reorganization, downsizing, outsourcing, industry (as opposed to NASA) led programs, and so forth are discussed. Sample applications of these capabilities to high Agency priority, fast-paced programs such as Reusable Launch Vehicle (RLV)/X-33 Phases I and 11, X-34, Hyper-X and X-38 are presented and lessons learned discussed. Lastly, enhancements in ground-based testing/CFD capabilities necessary to partially/fully satisfy future requirements are addressed.

Management of a CFD organization in support of space hardware development

NASA Technical Reports Server (NTRS)

Schutzenhofer, L. A.; Mcconnaughey, P. K.; Mcconnaughey, H. V.; Wang, T. S.

1991-01-01

The management strategy of NASA-Marshall's CFD branch in support of space hardware development and code validation implements various elements of total quality management. The strategy encompasses (1) a teaming strategy which focuses on the most pertinent problem, (2) quick-turnaround analysis, (3) the evaluation of retrofittable design options through sensitivity analysis, and (4) coordination between the chief engineer and the hardware contractors. Advanced-technology concepts are being addressed via the definition of technology-development projects whose products are transferable to hardware programs and the integration of research activities with industry, government agencies, and universities, on the basis of the 'consortium' concept.

Adjoint-Based Aerodynamic Design of Complex Aerospace Configurations

NASA Technical Reports Server (NTRS)

Nielsen, Eric J.

2016-01-01

An overview of twenty years of adjoint-based aerodynamic design research at NASA Langley Research Center is presented. Adjoint-based algorithms provide a powerful tool for efficient sensitivity analysis of complex large-scale computational fluid dynamics (CFD) simulations. Unlike alternative approaches for which computational expense generally scales with the number of design parameters, adjoint techniques yield sensitivity derivatives of a simulation output with respect to all input parameters at the cost of a single additional simulation. With modern large-scale CFD applications often requiring millions of compute hours for a single analysis, the efficiency afforded by adjoint methods is critical in realizing a computationally tractable design optimization capability for such applications.

Evaluation of CFD to Determine Two-Dimensional Airfoil Characteristics for Rotorcraft Applications

NASA Technical Reports Server (NTRS)

Smith, Marilyn J.; Wong, Tin-Chee; Potsdam, Mark; Baeder, James; Phanse, Sujeet

2004-01-01

The efficient prediction of helicopter rotor performance, vibratory loads, and aeroelastic properties still relies heavily on the use of comprehensive analysis codes by the rotorcraft industry. These comprehensive codes utilize look-up tables to provide two-dimensional aerodynamic characteristics. Typically these tables are comprised of a combination of wind tunnel data, empirical data and numerical analyses. The potential to rely more heavily on numerical computations based on Computational Fluid Dynamics (CFD) simulations has become more of a reality with the advent of faster computers and more sophisticated physical models. The ability of five different CFD codes applied independently to predict the lift, drag and pitching moments of rotor airfoils is examined for the SC1095 airfoil, which is utilized in the UH-60A main rotor. Extensive comparisons with the results of ten wind tunnel tests are performed. These CFD computations are found to be as good as experimental data in predicting many of the aerodynamic performance characteristics. Four turbulence models were examined (Baldwin-Lomax, Spalart-Allmaras, Menter SST, and k-omega).

Intracranial Vascular Disease Evaluation With Combined Vessel Wall Imaging And Patient Specific Hemodynamics

NASA Astrophysics Data System (ADS)

Samson, Kurt; Mossa-Basha, Mahmud; Yuan, Chun; Canton, Maria De Gador; Aliseda, Alberto

2017-11-01

Intracranial vascular pathologies are evaluated with angiography, conventional digital subtraction angiography or non-invasive (MRI, CT). Current techniques present limitations on the resolution with which the vessel wall characteristics can be measured, presenting a major challenge to differential diagnostic of cerebral vasculopathies. A new combined approach is presented that incorporates patient-specific image-based CFD models with intracranial vessel-wall MRI (VWMRI). Comparisons of the VWMRI measurements, evaluated for the presence of wall enhancement and thin-walled regions, against CFD metrics such as wall shear stress (WSS), and oscillatory shear index (OSI) are used to understand how the new imaging technique developed can predict the influence of hemodynamics on the deterioration of the aneurysmal wall, leading to rupture. Additionally, histology of each resected aneurysm, evaluated for inflammatory infiltration and wall thickness features, is used to validate the analysis from VWMRI and CFD. This data presents a solid foundation on which to build a new framework for combined VWMRI-CFD to predict unstable wall changes in unruptured intracranial aneurysms, and support clinical monitoring and intervention decisions.

Development of a CFD Code for Analysis of Fluid Dynamic Forces in Seals

NASA Technical Reports Server (NTRS)

Athavale, Mahesh M.; Przekwas, Andrzej J.; Singhal, Ashok K.

1991-01-01

The aim is to develop a 3-D computational fluid dynamics (CFD) code for the analysis of fluid flow in cylindrical seals and evaluation of the dynamic forces on the seals. This code is expected to serve as a scientific tool for detailed flow analysis as well as a check for the accuracy of the 2D industrial codes. The features necessary in the CFD code are outlined. The initial focus was to develop or modify and implement new techniques and physical models. These include collocated grid formulation, rotating coordinate frames and moving grid formulation. Other advanced numerical techniques include higher order spatial and temporal differencing and an efficient linear equation solver. These techniques were implemented in a 2D flow solver for initial testing. Several benchmark test cases were computed using the 2D code, and the results of these were compared to analytical solutions or experimental data to check the accuracy. Tests presented here include planar wedge flow, flow due to an enclosed rotor, and flow in a 2D seal with a whirling rotor. Comparisons between numerical and experimental results for an annular seal and a 7-cavity labyrinth seal are also included.

Shape design and CFD analysis on a 1MW-class horizontal axis tidal current turbine blade

NASA Astrophysics Data System (ADS)

Singh, P. M.; Choi, Y. D.

2013-12-01

This study aims to develop a 1MW-class horizontal axis tidal current turbine rotor blade which can be applied near the southwest island regions of South Korea. On the basis of actual tidal current conditions of southern region of Korea, configuration design of 1MW class turbine rotor blade is carried out by BEMT (Blade element momentum theory). The hydrodynamic performance including the lift and drag forces, is conducted with the variation of the angle of attack using an open source code of X-Foil. The purpose of the study is to study the shape of the hydrofoil used and how it affects the performance of the turbine. After a thorough study of many airfoils, a new hydrofoil is developed using the S814 and DU-91-W2- 250 airfoils, which show good performance for rough conditions. A combination of the upper and lower surface of the two hydrofoils is tested. Three dimensional models were developed and the optimized blade geometry is used for CFD (Computational Fluid Dynamics) analysis with hexahedral numerical grids. Power coefficient, pressure coefficient and velocity distributions are investigated according to Tip Speed Ratio by CFD analysis.

CFD research and systems in Kawasaki Heavy Industries and its future prospects

NASA Astrophysics Data System (ADS)

Hiraoka, Koichi

1990-09-01

KHI Computational Fluid Dynamics (CFD) system is composed of VP100 computer and 2-D and 3-D Euler and/or Navier-Stokes (NS) analysis softwares. For KHI, this system has become a very powerful aerodynamic tool together with the Kawasaki 1 m Transonic Wind Tunnel. The 2-D Euler/NS software, developed in-house, is fully automated, requires no special skill, and was successfully applied to the design of YXX high lift devices and SST supersonic inlet, etc. The 3-D Euler/NS software, developed under joint research with NAL, has an interactively operated Multi-Block type grid generator and can effectively generate grids around complex airplane shapes. Due to the main memory size limitation, 3-D analysis of relatively simple shape, such as SST wing-body, was computed in-house on VP100, otherwise, such as detailed 3-D analyses of ASUKA and HOPE, were computed on NAL VP400, which is 10 times more powerful than VP100, under KHI-NAL joint research. These analysis results have very good correlation with experimental results. However, the present CFD system is less productive than wind tunnel and has applicability limitations.

Numerical and experimental validation for the thermal transmittance of windows with cellular shades

DOE PAGES

Hart, Robert

2018-02-21

Some highly energy efficient window attachment products are available today, but more rapid market adoption would be facilitated by fair performance metrics. It is important to have validated simulation tools to provide a basis for this analysis. This paper outlines a review and validation of the ISO 15099 center-of-glass zero-solar-load heat transfer correlations for windows with cellular shades. Thermal transmittance was measured experimentally, simulated using computational fluid dynamics (CFD) analysis, and simulated utilizing correlations from ISO 15099 as implemented in Berkeley Lab WINDOW and THERM software. CFD analysis showed ISO 15099 underestimates heat flux of rectangular cavities by up tomore » 60% when aspect ratio (AR) = 1 and overestimates heat flux up to 20% when AR = 0.5. CFD analysis also showed that wave-type surfaces of cellular shades have less than 2% impact on heat flux through the cavities and less than 5% for natural convection of room-side surface. WINDOW was shown to accurately represent heat flux of the measured configurations to a mean relative error of 0.5% and standard deviation of 3.8%. Finally, several shade parameters showed significant influence on correlation accuracy, including distance between shade and glass, inconsistency in cell stretch, size of perimeter gaps, and the mounting hardware.« less

Numerical and experimental validation for the thermal transmittance of windows with cellular shades

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, Robert

Some highly energy efficient window attachment products are available today, but more rapid market adoption would be facilitated by fair performance metrics. It is important to have validated simulation tools to provide a basis for this analysis. This paper outlines a review and validation of the ISO 15099 center-of-glass zero-solar-load heat transfer correlations for windows with cellular shades. Thermal transmittance was measured experimentally, simulated using computational fluid dynamics (CFD) analysis, and simulated utilizing correlations from ISO 15099 as implemented in Berkeley Lab WINDOW and THERM software. CFD analysis showed ISO 15099 underestimates heat flux of rectangular cavities by up tomore » 60% when aspect ratio (AR) = 1 and overestimates heat flux up to 20% when AR = 0.5. CFD analysis also showed that wave-type surfaces of cellular shades have less than 2% impact on heat flux through the cavities and less than 5% for natural convection of room-side surface. WINDOW was shown to accurately represent heat flux of the measured configurations to a mean relative error of 0.5% and standard deviation of 3.8%. Finally, several shade parameters showed significant influence on correlation accuracy, including distance between shade and glass, inconsistency in cell stretch, size of perimeter gaps, and the mounting hardware.« less

Interaction between Nbp35 and Cfd1 Proteins of Cytosolic Fe-S Cluster Assembly Reveals a Stable Complex Formation in Entamoeba histolytica

PubMed Central

Anwar, Shadab; Dikhit, Manas Ranjan; Singh, Krishn Pratap; Kar, Rajiv Kumar; Zaidi, Amir; Sahoo, Ganesh Chandra; Roy, Awadh Kishore; Nozaki, Tomoyoshi; Das, Pradeep; Ali, Vahab

2014-01-01

Iron-Sulfur (Fe-S) proteins are involved in many biological functions such as electron transport, photosynthesis, regulation of gene expression and enzymatic activities. Biosynthesis and transfer of Fe-S clusters depend on Fe-S clusters assembly processes such as ISC, SUF, NIF, and CIA systems. Unlike other eukaryotes which possess ISC and CIA systems, amitochondriate Entamoeba histolytica has retained NIF & CIA systems for Fe-S cluster assembly in the cytosol. In the present study, we have elucidated interaction between two proteins of E. histolytica CIA system, Cytosolic Fe-S cluster deficient 1 (Cfd1) protein and Nucleotide binding protein 35 (Nbp35). In-silico analysis showed that structural regions ranging from amino acid residues (P33-K35, G131-V135 and I147-E151) of Nbp35 and (G5-V6, M34-D39 and G46-A52) of Cfd1 are involved in the formation of protein-protein complex. Furthermore, Molecular dynamic (MD) simulations study suggested that hydrophobic forces surpass over hydrophilic forces between Nbp35 and Cfd1 and Van-der-Waal interaction plays crucial role in the formation of stable complex. Both proteins were separately cloned, expressed as recombinant fusion proteins in E. coli and purified to homogeneity by affinity column chromatography. Physical interaction between Nbp35 and Cfd1 proteins was confirmed in vitro by co-purification of recombinant Nbp35 with thrombin digested Cfd1 and in vivo by pull down assay and immunoprecipitation. The insilico, in vitro as well as in vivo results prove a stable interaction between these two proteins, supporting the possibility of its involvement in Fe-S cluster transfer to target apo-proteins through CIA machinery in E. histolytica. Our study indicates that initial synthesis of a Fe-S precursor in mitochondria is not necessary for the formation of Cfd1-Nbp35 complex. Thus, Cfd1 and Nbp35 with the help of cytosolic NifS and NifU proteins can participate in the maturation of non-mitosomal Fe-S proteins without any apparent assistance of mitosomes. PMID:25271645

Interaction between Nbp35 and Cfd1 proteins of cytosolic Fe-S cluster assembly reveals a stable complex formation in Entamoeba histolytica.

PubMed

Anwar, Shadab; Dikhit, Manas Ranjan; Singh, Krishn Pratap; Kar, Rajiv Kumar; Zaidi, Amir; Sahoo, Ganesh Chandra; Roy, Awadh Kishore; Nozaki, Tomoyoshi; Das, Pradeep; Ali, Vahab

2014-01-01

Iron-Sulfur (Fe-S) proteins are involved in many biological functions such as electron transport, photosynthesis, regulation of gene expression and enzymatic activities. Biosynthesis and transfer of Fe-S clusters depend on Fe-S clusters assembly processes such as ISC, SUF, NIF, and CIA systems. Unlike other eukaryotes which possess ISC and CIA systems, amitochondriate Entamoeba histolytica has retained NIF & CIA systems for Fe-S cluster assembly in the cytosol. In the present study, we have elucidated interaction between two proteins of E. histolytica CIA system, Cytosolic Fe-S cluster deficient 1 (Cfd1) protein and Nucleotide binding protein 35 (Nbp35). In-silico analysis showed that structural regions ranging from amino acid residues (P33-K35, G131-V135 and I147-E151) of Nbp35 and (G5-V6, M34-D39 and G46-A52) of Cfd1 are involved in the formation of protein-protein complex. Furthermore, Molecular dynamic (MD) simulations study suggested that hydrophobic forces surpass over hydrophilic forces between Nbp35 and Cfd1 and Van-der-Waal interaction plays crucial role in the formation of stable complex. Both proteins were separately cloned, expressed as recombinant fusion proteins in E. coli and purified to homogeneity by affinity column chromatography. Physical interaction between Nbp35 and Cfd1 proteins was confirmed in vitro by co-purification of recombinant Nbp35 with thrombin digested Cfd1 and in vivo by pull down assay and immunoprecipitation. The insilico, in vitro as well as in vivo results prove a stable interaction between these two proteins, supporting the possibility of its involvement in Fe-S cluster transfer to target apo-proteins through CIA machinery in E. histolytica. Our study indicates that initial synthesis of a Fe-S precursor in mitochondria is not necessary for the formation of Cfd1-Nbp35 complex. Thus, Cfd1 and Nbp35 with the help of cytosolic NifS and NifU proteins can participate in the maturation of non-mitosomal Fe-S proteins without any apparent assistance of mitosomes.

Multiscale computational modeling of a radiantly driven solar thermal collector

NASA Astrophysics Data System (ADS)

Ponnuru, Koushik

The objectives of the master's thesis are to present, discuss and apply sequential multiscale modeling that combines analytical, numerical (finite element-based) and computational fluid dynamic (CFD) analysis to assist in the development of a radiantly driven macroscale solar thermal collector for energy harvesting. The solar thermal collector is a novel green energy system that converts solar energy to heat and utilizes dry air as a working heat transfer fluid (HTF). This energy system has important advantages over competitive technologies: it is self-contained (no energy sources are needed), there are no moving parts, no oil or supplementary fluids are needed and it is environmentally friendly since it is powered by solar radiation. This work focuses on the development of multi-physics and multiscale models for predicting the performance of the solar thermal collector. Model construction and validation is organized around three distinct and complementary levels. The first level involves an analytical analysis of the thermal transpiration phenomenon and models for predicting the associated mass flow pumping that occurs in an aerogel membrane in the presence of a large thermal gradient. Within the aerogel, a combination of convection, conduction and radiation occurs simultaneously in a domain where the pore size is comparable to the mean free path of the gas molecules. CFD modeling of thermal transpiration is not possible because all the available commercial CFD codes solve the Navier Stokes equations only for continuum flow, which is based on the assumption that the net molecular mass diffusion is zero. However, thermal transpiration occurs in a flow regime where a non-zero net molecular mass diffusion exists. Thus these effects are modeled by using Sharipov's [2] analytical expression for gas flow characterized by high Knudsen number. The second level uses a detailed CFD model solving Navier Stokes equations for momentum, heat and mass transfer in the various components of the device. We have used state-of-the-art computational fluid dynamics (CFD) software, Flow3D (www.flow3d.com) to model the effects of multiple coupled physical processes including buoyancy driven flow from local temperature differences within the plenums, fluid-solid momentum and heat transfer, and coupled radiation exchange between the aerogel, top glazing and environment. In addition, the CFD models include both convection and radiation exchange between the top glazing and the environment. Transient and steady-state thermal models have been constructed using COMSOL Multiphysics. The third level consists of a lumped-element system model, which enables rapid parametric analysis and helps to develop an understanding of the system behavior; the mathematical models developed and multiple CFD simulations studies focus on simultaneous solution of heat, momentum, mass and gas volume fraction balances and succeed in accurate state variable distributions confirmed by experimental measurements.

A Measurement and Simulation Based Methodology for Cache Performance Modeling and Tuning

NASA Technical Reports Server (NTRS)

Waheed, Abdul; Yan, Jerry; Saini, Subhash (Technical Monitor)

1998-01-01

We present a cache performance modeling methodology that facilitates the tuning of uniprocessor cache performance for applications executing on shared memory multiprocessors by accurately predicting the effects of source code level modifications. Measurements on a single processor are initially used for identifying parts of code where cache utilization improvements may significantly impact the overall performance. Cache simulation based on trace-driven techniques can be carried out without gathering detailed address traces. Minimal runtime information for modeling cache performance of a selected code block includes: base virtual addresses of arrays, virtual addresses of variables, and loop bounds for that code block. Rest of the information is obtained from the source code. We show that the cache performance predictions are as reliable as those obtained through trace-driven simulations. This technique is particularly helpful to the exploration of various "what-if' scenarios regarding the cache performance impact for alternative code structures. We explain and validate this methodology using a simple matrix-matrix multiplication program. We then apply this methodology to predict and tune the cache performance of two realistic scientific applications taken from the Computational Fluid Dynamics (CFD) domain.

Ballistics Modeling for Non-Axisymmetric Hypervelocity Smart Bullets

DTIC Science & Technology

2014-06-03

can in principle come from experiments or computational fluid dynamics ( CFD ) calculations. CFD calculations are carried out for a standard bullet...come from experiments or com- putational fluid dynamics ( CFD ) calculations. CFD calculations are carried out for a standard bullet (0.308” 168 grain...11 2. Spin and Pitch Damping 11 3. Magnus Moment 12 IV. CFD Simulations and Ballistic Trajectories 12 A. CFD Modeling of a Standard Bullet 12 B

CO2 Washout Testing Using Various Inlet Vent Configurations in the Mark-III Space Suit

NASA Technical Reports Server (NTRS)

Korona, F. Adam; Norcross, Jason; Conger, Bruce; Navarro, Moses

2014-01-01

Requirements for using a space suit during ground testing include providing adequate carbon dioxide (CO2) washout for the suited subject. Acute CO2 exposure can lead to symptoms including headache, dyspnea, lethargy and eventually unconsciousness or even death. Symptoms depend on several factors including inspired partial pressure of CO2 (ppCO2), duration of exposure, metabolic rate of the subject and physiological differences between subjects. Computational Fluid Dynamic (CFD) analysis has predicted that the configuration of the suit inlet vent has a significant effect on oronasal CO2 concentrations. The main objective of this test is to characterize inspired oronasal ppCO2 for a variety of inlet vent configurations in the Mark-III space suit across a range of workload and flow rates. As a secondary objective, results will be compared to the predicted CO2 concentrations and used to refine existing CFD models. These CFD models will then be used to help design an inlet vent configuration for the Z-2 space suit, which maximizes oronasal CO2 washout. This test has not been completed, but is planned for January 2014. The results of this test will be incorporated into this paper. The testing methodology used in this test builds upon past CO2 washout testing performed on the Z-1 suit, Rear Entry I-Suit (REI) and the Enhanced Mobility Advanced Crew Escape Suit (EM-ACES). Three subjects will be tested in the Mark-III space suit with each subject performing two test sessions to allow for comparison between tests. Six different helmet inlet vent configurations will be evaluated during each test session. Suit pressure will be maintained at 4.3 psid. Subjects will wear the suit while walking on a treadmill to generate metabolic workloads of approximately 2000 and 3000 BTU/hr. Supply airflow rates of 6 and 4 actual cubic feet per minute (ACFM) will be tested at each workload. Subjects will wear an oronasal mask with an open port in front of the mouth and will be allowed to breathe freely. Oronasal ppCO2 will be monitored real-time via gas analyzers with sampling tubes connected to the oronasal mask. Metabolic rate will be calculated from the total oxygen consumption and CO2 production measured by additional gas analyzers at the air outlet from the suit. Real-time metabolic rate measurements will be used to adjust the treadmill workload to meet target metabolic rates. This paper provides detailed descriptions of the test hardware, methodology and results, as well as implications for future inlet vent design and ground testing in the Mark-III.

The Role of Computational Fluid Dynamics in the Management of Unruptured Intracranial Aneurysms: A Clinicians' View

PubMed Central

Singh, Pankaj K.; Marzo, Alberto; Coley, Stuart C.; Berti, Guntram; Bijlenga, Philippe; Lawford, Patricia V.; Villa-Uriol, Mari-Cruz; Rufenacht, Daniel A.; McCormack, Keith M.; Frangi, Alejandro; Patel, Umang J.; Hose, D. Rodney

2009-01-01

Objective. The importance of hemodynamics in the etiopathogenesis of intracranial aneurysms (IAs) is widely accepted. Computational fluid dynamics (CFD) is being used increasingly for hemodynamic predictions. However, alogn with the continuing development and validation of these tools, it is imperative to collect the opinion of the clinicians. Methods. A workshop on CFD was conducted during the European Society of Minimally Invasive Neurological Therapy (ESMINT) Teaching Course, Lisbon, Portugal. 36 delegates, mostly clinicians, performed supervised CFD analysis for an IA, using the @neuFuse software developed within the European project @neurIST. Feedback on the workshop was collected and analyzed. The performance was assessed on a scale of 1 to 4 and, compared with experts' performance. Results. Current dilemmas in the management of unruptured IAs remained the most important motivating factor to attend the workshop and majority of participants showed interest in participating in a multicentric trial. The participants achieved an average score of 2.52 (range 0–4) which was 63% (range 0–100%) of an expert user. Conclusions. Although participants showed a manifest interest in CFD, there was a clear lack of awareness concerning the role of hemodynamics in the etiopathogenesis of IAs and the use of CFD in this context. More efforts therefore are required to enhance understanding of the clinicians in the subject. PMID:19696903

Dynamics of Numerics & Spurious Behaviors in CFD Computations. Revised

NASA Technical Reports Server (NTRS)

Yee, Helen C.; Sweby, Peter K.

1997-01-01

The global nonlinear behavior of finite discretizations for constant time steps and fixed or adaptive grid spacings is studied using tools from dynamical systems theory. Detailed analysis of commonly used temporal and spatial discretizations for simple model problems is presented. The role of dynamics in the understanding of long time behavior of numerical integration and the nonlinear stability, convergence, and reliability of using time-marching approaches for obtaining steady-state numerical solutions in computational fluid dynamics (CFD) is explored. The study is complemented with examples of spurious behavior observed in steady and unsteady CFD computations. The CFD examples were chosen to illustrate non-apparent spurious behavior that was difficult to detect without extensive grid and temporal refinement studies and some knowledge from dynamical systems theory. Studies revealed the various possible dangers of misinterpreting numerical simulation of realistic complex flows that are constrained by available computing power. In large scale computations where the physics of the problem under study is not well understood and numerical simulations are the only viable means of solution, extreme care must be taken in both computation and interpretation of the numerical data. The goal of this paper is to explore the important role that dynamical systems theory can play in the understanding of the global nonlinear behavior of numerical algorithms and to aid the identification of the sources of numerical uncertainties in CFD.

Real-Time Visualization of an HPF-based CFD Simulation

NASA Technical Reports Server (NTRS)

Kremenetsky, Mark; Vaziri, Arsi; Haimes, Robert; Chancellor, Marisa K. (Technical Monitor)

1996-01-01

Current time-dependent CFD simulations produce very large multi-dimensional data sets at each time step. The visual analysis of computational results are traditionally performed by post processing the static data on graphics workstations. We present results from an alternate approach in which we analyze the simulation data in situ on each processing node at the time of simulation. The locally analyzed results, usually more economical and in a reduced form, are then combined and sent back for visualization on a graphics workstation.

Towards the Teraflop CFD

NASA Technical Reports Server (NTRS)

Schreiber, Robert; Simon, Horst D.

1992-01-01

We are surveying current projects in the area of parallel supercomputers. The machines considered here will become commercially available in the 1990 - 1992 time frame. All are suitable for exploring the critical issues in applying parallel processors to large scale scientific computations, in particular CFD calculations. This chapter presents an overview of the surveyed machines, and a detailed analysis of the various architectural and technology approaches taken. Particular emphasis is placed on the feasibility of a Teraflops capability following the paths proposed by various developers.

High-speed inlet research program and supporting analysis

NASA Technical Reports Server (NTRS)

Coltrin, Robert E.

1990-01-01

The technology challenges faced by the high speed inlet designer are discussed by describing the considerations that went into the design of the Mach 5 research inlet. It is shown that the emerging three dimensional viscous computational fluid dynamics (CFD) flow codes, together with small scale experiments, can be used to guide larger scale full inlet systems research. Then, in turn, the results of the large scale research, if properly instrumented, can be used to validate or at least to calibrate the CFD codes.

Monte Carlo Methodology Serves Up a Software Success

NASA Technical Reports Server (NTRS)

2003-01-01

Widely used for the modeling of gas flows through the computation of the motion and collisions of representative molecules, the Direct Simulation Monte Carlo method has become the gold standard for producing research and engineering predictions in the field of rarefied gas dynamics. Direct Simulation Monte Carlo was first introduced in the early 1960s by Dr. Graeme Bird, a professor at the University of Sydney, Australia. It has since proved to be a valuable tool to the aerospace and defense industries in providing design and operational support data, as well as flight data analysis. In 2002, NASA brought to the forefront a software product that maintains the same basic physics formulation of Dr. Bird's method, but provides effective modeling of complex, three-dimensional, real vehicle simulations and parallel processing capabilities to handle additional computational requirements, especially in areas where computational fluid dynamics (CFD) is not applicable. NASA's Direct Simulation Monte Carlo Analysis Code (DAC) software package is now considered the Agency s premier high-fidelity simulation tool for predicting vehicle aerodynamics and aerothermodynamic environments in rarified, or low-density, gas flows.

Large Eddy Simulation of Flow in Turbine Cascades Using LESTool and UNCLE Codes

NASA Technical Reports Server (NTRS)

Huang, P. G.

2004-01-01

During the period December 23,1997 and December August 31,2004, we accomplished the development of 2 CFD codes for DNS/LES/RANS simulation of turbine cascade flows, namely LESTool and UNCLE. LESTool is a structured code making use of 5th order upwind differencing scheme and UNCLE is a second-order-accuracy unstructured code. LESTool has both Dynamic SGS and Spalart's DES models and UNCLE makes use of URANS and DES models. The current report provides a description of methodologies used in the codes.

Large Eddy Simulation of Flow in Turbine Cascades Using LEST and UNCLE Codes

NASA Technical Reports Server (NTRS)

Ashpis, David (Technical Monitor); Huang, P. G.

2004-01-01

During the period December 23, 1997 and December August 31, 2004, we accomplished the development of 2 CFD codes for DNS/LES/RANS simulation of turbine cascade flows, namely LESTool and UNCLE. LESTool is a structured code making use of 5th order upwind differencing scheme and UNCLE is a second-order-accuracy unstructured code. LESTool has both Dynamic SGS and Sparlart's DES models and UNCLE makes use of URANS and DES models. The current report provides a description of methodologies used in the codes.

Stability and Control CFD Investigations of a Generic 53 Degree Swept UCAV Configuration

NASA Technical Reports Server (NTRS)

Frink, Neal T.

2014-01-01

NATO STO Task Group AVT-201 on "Extended Assessment of Reliable Stability & Control Prediction Methods for NATO Air Vehicles" is studying various computational approaches to predict stability and control parameters for aircraft undergoing non-linear flight conditions. This paper contributes an assessment through correlations with wind tunnel data for the state of aerodynamic predictive capability of time-accurate RANS methodology on the group's focus configuration, a 53deg swept and twisted lambda wing UCAV, undergoing a variety of roll, pitch, and yaw motions. The vehicle aerodynamics is dominated by the complex non-linear physics of round leading-edge vortex flow separation. Correlations with experimental data are made for static longitudinal/lateral sweeps, and at varying frequencies of prescribed roll/pitch/yaw sinusoidal motion for the vehicle operating with and without control surfaces. The data and the derived understanding should prove useful to the AVT-201 team and other researchers who are developing techniques for augmenting flight simulation models from low-speed CFD predictions of aircraft traversing non-linear regions of a flight envelope.

Computational Models for Nanoscale Fluid Dynamics and Transport Inspired by Nonequilibrium Thermodynamics1

PubMed Central

Radhakrishnan, Ravi; Yu, Hsiu-Yu; Eckmann, David M.; Ayyaswamy, Portonovo S.

2017-01-01

Traditionally, the numerical computation of particle motion in a fluid is resolved through computational fluid dynamics (CFD). However, resolving the motion of nanoparticles poses additional challenges due to the coupling between the Brownian and hydrodynamic forces. Here, we focus on the Brownian motion of a nanoparticle coupled to adhesive interactions and confining-wall-mediated hydrodynamic interactions. We discuss several techniques that are founded on the basis of combining CFD methods with the theory of nonequilibrium statistical mechanics in order to simultaneously conserve thermal equipartition and to show correct hydrodynamic correlations. These include the fluctuating hydrodynamics (FHD) method, the generalized Langevin method, the hybrid method, and the deterministic method. Through the examples discussed, we also show a top-down multiscale progression of temporal dynamics from the colloidal scales to the molecular scales, and the associated fluctuations, hydrodynamic correlations. While the motivation and the examples discussed here pertain to nanoscale fluid dynamics and mass transport, the methodologies presented are rather general and can be easily adopted to applications in convective heat transfer. PMID:28035168

Robust optimization of supersonic ORC nozzle guide vanes

NASA Astrophysics Data System (ADS)

Bufi, Elio A.; Cinnella, Paola

2017-03-01

An efficient Robust Optimization (RO) strategy is developed for the design of 2D supersonic Organic Rankine Cycle turbine expanders. The dense gas effects are not-negligible for this application and they are taken into account describing the thermodynamics by means of the Peng-Robinson-Stryjek-Vera equation of state. The design methodology combines an Uncertainty Quantification (UQ) loop based on a Bayesian kriging model of the system response to the uncertain parameters, used to approximate statistics (mean and variance) of the uncertain system output, a CFD solver, and a multi-objective non-dominated sorting algorithm (NSGA), also based on a Kriging surrogate of the multi-objective fitness function, along with an adaptive infill strategy for surrogate enrichment at each generation of the NSGA. The objective functions are the average and variance of the isentropic efficiency. The blade shape is parametrized by means of a Free Form Deformation (FFD) approach. The robust optimal blades are compared to the baseline design (based on the Method of Characteristics) and to a blade obtained by means of a deterministic CFD-based optimization.

NASA Computational Fluid Dynamics Conference. Volume 2: Sessions 7-12

NASA Technical Reports Server (NTRS)

1989-01-01

The objectives of the conference were to disseminate CFD research results to industry and university CFD researchers, to promote synergy among NASA CFD researchers, and to permit feedback from researchers outside of NASA on issues pacing the discipline of CFD. The focus of the conference was on the application of CFD technology but also included fundamental activities.

Combustor Operability and Performance Verification for HIFiRE Flight 2

NASA Technical Reports Server (NTRS)

Storch, Andrea M.; Bynum, Michael; Liu, Jiwen; Gruber, Mark

2011-01-01

As part of the Hypersonic International Flight Research Experimentation (HIFiRE) Direct-Connect Rig (HDCR) test and analysis activity, three-dimensional computational fluid dynamics (CFD) simulations were performed using two Reynolds-Averaged Navier Stokes solvers. Measurements obtained from ground testing in the NASA Langley Arc-Heated Scramjet Test Facility (AHSTF) were used to specify inflow conditions for the simulations and combustor data from four representative tests were used as benchmarks. Test cases at simulated flight enthalpies of Mach 5.84, 6.5, 7.5, and 8.0 were analyzed. Modeling parameters (e.g., turbulent Schmidt number and compressibility treatment) were tuned such that the CFD results closely matched the experimental results. The tuned modeling parameters were used to establish a standard practice in HIFiRE combustor analysis. Combustor performance and operating mode were examined and were found to meet or exceed the objectives of the HIFiRE Flight 2 experiment. In addition, the calibrated CFD tools were then applied to make predictions of combustor operation and performance for the flight configuration and to aid in understanding the impacts of ground and flight uncertainties on combustor operation.

CFD modeling of a UV-A LED baffled flat-plate photoreactor for environment applications: a mining wastewater case.

PubMed

Devia-Orjuela, John Steven; Betancourt-Buitrago, Luis Andrés; Machuca-Martinez, Fiderman

2018-06-02

The use of ultraviolet light in photoreactors for wastewater treatment has become popular as an alternative of known chemical oxidative substances. UV LED light represents cheaper, robust, and versatile alternative to traditional UV lamps. In this study, it was designed and evaluated a photoreactor with an approach of chemical fluid dynamics (CFD) and experimental validation. The evaluation consisted of (1) CFD velocity profile analysis, (2) characterization of the average light distribution with potassium ferrioxalate actinometry, (3) degradation of a typical recalcitrant metallic cyanocomplex Fe(CN) 6 3- , and (4) scavenger effect analysis in the photodegradation using potassium persulfate. Actinometrical essay concluded that the system was able to receive 1.93 μE/s. The reactor operated under turbulent regime and best result for Fe(CN) 6 3- degradation was obtained at 4 h of operation, using 5-W UV-A LEDs, with pH ~ 7 and 10 mM de S 2 O 8 2- . Baffled photoreactor demonstrated to be useful for this type of illumination and wastewater treatment.

Carbon Dioxide Washout Testing Using Various Inlet Vent Configurations in the Mark-III Space Suit

NASA Technical Reports Server (NTRS)

Korona, F. Adam; Norcross, Jason; Conger, Bruce; Navarro, Moses

2014-01-01

Requirements for using a space suit during ground testing include providing adequate carbon dioxide (CO2) washout for the suited subject. Acute CO2 exposure can lead to symptoms including headache, dyspnea, lethargy, and eventually unconsciousness or even death. Symptoms depend on several factors including inspired partial pressure of CO2 (ppCO2), duration of exposure, metabolic rate of the subject, and physiological differences between subjects. Computational Fluid Dynamics (CFD) analysis has predicted that the configuration of the suit inlet vent has a significant effect on oronasal CO2 concentrations. The main objective of this test was to characterize inspired oronasal ppCO2 for a variety of inlet vent configurations in the Mark-III suit across a range of workload and flow rates. Data and trends observed during testing along with refined CFD models will be used to help design an inlet vent configuration for the Z-2 space suit. The testing methodology used in this test builds upon past CO2 washout testing performed on the Z-1 suit, Rear Entry I-Suit, and the Enhanced Mobility Advanced Crew Escape Suit. Three subjects performed two test sessions each in the Mark-III suit to allow for comparison between tests. Six different helmet inlet vent configurations were evaluated during each test session. Suit pressure was maintained at 4.3 psid. Suited test subjects walked on a treadmill to generate metabolic workloads of approximately 2000 and 3000 BTU/hr. Supply airflow rates of 6 and 4 actual cubic feet per minute were tested at each workload. Subjects wore an oronasal mask with an open port in front of the mouth and were allowed to breathe freely. Oronasal ppCO2 was monitored real-time via gas analyzers with sampling tubes connected to the oronasal mask. Metabolic rate was calculated from the CO2 production measured by an additional gas analyzer at the air outlet from the suit. Real-time metabolic rate measurements were used to adjust the treadmill workload to meet target metabolic rates. This paper provides detailed descriptions of the test hardware, methodology and results, as well as implications for future inlet vent designs and ground testing.

Reduced order modeling and active flow control of an inlet duct

NASA Astrophysics Data System (ADS)

Ge, Xiaoqing

Many aerodynamic applications require the modeling of compressible flows in or around a body, e.g., the design of aircraft, inlet or exhaust duct, wind turbines, or tall buildings. Traditional methods use wind tunnel experiments and computational fluid dynamics (CFD) to investigate the spatial and temporal distribution of the flows. Although they provide a great deal of insight into the essential characteristics of the flow field, they are not suitable for control analysis and design due to the high physical/computational cost. Many model reduction methods have been studied to reduce the complexity of the flow model. There are two main approaches: linearization based input/output modeling and proper orthogonal decomposition (POD) based model reduction. The former captures mostly the local behavior near a steady state, which is suitable to model laminar flow dynamics. The latter obtains a reduced order model by projecting the governing equation onto an "optimal" subspace and is able to model complex nonlinear flow phenomena. In this research we investigate various model reduction approaches and compare them in flow modeling and control design. We propose an integrated model-based control methodology and apply it to the reduced order modeling and active flow control of compressible flows within a very aggressive (length to exit diameter ratio, L/D, of 1.5) inlet duct and its upstream contraction section. The approach systematically applies reduced order modeling, estimator design, sensor placement and control design to improve the aerodynamic performance. The main contribution of this work is the development of a hybrid model reduction approach that attempts to combine the best features of input/output model identification and POD method. We first identify a linear input/output model by using a subspace algorithm. We next project the difference between CFD response and the identified model response onto a set of POD basis. This trajectory is fit to a nonlinear dynamical model to augment the linear input/output model. Thus, the full system is decomposed into a dominant linear subsystem and a low order nonlinear subsystem. The hybrid model is then used for control design and compared with other modeling methods in CFD simulations. Numerical results indicate that the hybrid model accurately predicts the nonlinear behavior of the flow for a 2D diffuser contraction section model. It also performs best in terms of feedback control design and learning control. Since some outputs of interest (e.g., the AIP pressure recovery) are not observable during normal operations, static and dynamic estimators are designed to recreate the information from available sensor measurements. The latter also provides a state estimation for feedback controller. Based on the reduced order models and estimators, different controllers are designed to improve the aerodynamic performance of the contraction section and inlet duct. The integrated control methodology is evaluated with CFD simulations. Numerical results demonstrate the feasibility and efficacy of the active flow control based on reduced order models. Our reduced order models not only generate a good approximation of the nonlinear flow dynamics over a wide input range, but also help to design controllers that significantly improve the flow response. The tools developed for model reduction, estimator and control design can also be applied to wind tunnel experiment.

Method for CFD Simulation of Propellant Slosh in a Spherical Tank

NASA Technical Reports Server (NTRS)

Benson, David J.; Mason, Paul A.

2011-01-01

Propellant sloshing can impart unwanted disturbances to spacecraft, especially if the spacecraft controller is driving the system at the slosh frequency. This paper describes the work performed by the authors in simulating propellant slosh in a spherical tank using computational fluid dynamics (CFD). ANSYS-CFX is the CFD package used to perform the analysis. A 42 in spherical tank is studied with various fill fractions. Results are provided for the forces on the walls and the frequency of the slosh. Snapshots of slosh animation give a qualitative understanding of the propellant slosh. The results show that maximum slosh forces occur at a tank fill fraction of 0.4 and 0.6 due to the amount of mass participating in the slosh and the room available for sloshing to occur. The slosh frequency increases as the tank fill fraction increases.

Experimental and CFD modelling for thermal comfort and CO2 concentration in office building

NASA Astrophysics Data System (ADS)

Kabrein, H.; Hariri, A.; Leman, A. M.; Yusof, M. Z. M.; Afandi, A.

2017-09-01

Computational fluid dynamic CFD was used for simulating air flow, indoor air distribution and contamination concentration. Gases pollution and thermal discomfort affected occupational health and productivity of work place. The main objectives of this study are to investigate the impact of air change rate in CO2 concentration and to estimate the profile of CO2 concentration in the offices building. The thermal comfort and gases contamination are investigated by numerical analysis CFD which was validated by experiment. Thus the air temperature, air velocity and CO2 concentration were measured at several points in the chamber with four occupants. Comparing between experimental and numerical results showed good agreement. In addition, the CO2 concentration around human recorded high, compared to the other area. Moreover, the thermal comfort in this study is within the ASHRAE standard 55-2004.

Distribution of Acoustic Power Spectra for an Isolated Helicopter Fuselage

NASA Astrophysics Data System (ADS)

Kusyumov, A. N.; Mikhailov, S. A.; Garipova, L. I.; Batrakov, A. S.; Barakos, G.

2016-03-01

The broadband aerodynamic noise can be studied, assuming isotropic flow, turbulence and decay. Proudman's approach allows practical calculations of noise based on CFD solutions of RANS or URANS equations at the stage of post processing and analysis of the solution. Another aspect is the broadband acoustic spectrum and the distribution of acoustic power over a range of frequencies. The acoustic energy spectrum distribution in isotropic turbulence is non monotonic and has a maximum at a certain value of Strouhal number. In the present work the value of acoustic power peak frequency is determined using a prescribed form of acoustic energy spectrum distribution presented in papers by S. Sarkar and M. Y. Hussaini and by G. M. Lilley. CFD modelling of the flow around isolated helicopter fuselage model was considered using the HMB CFD code and the RANS equations.

Improving Fidelity of Launch Vehicle Liftoff Acoustic Simulations

NASA Technical Reports Server (NTRS)

Liever, Peter; West, Jeff

2016-01-01

Launch vehicles experience high acoustic loads during ignition and liftoff affected by the interaction of rocket plume generated acoustic waves with launch pad structures. Application of highly parallelized Computational Fluid Dynamics (CFD) analysis tools optimized for application on the NAS computer systems such as the Loci/CHEM program now enable simulation of time-accurate, turbulent, multi-species plume formation and interaction with launch pad geometry and capture the generation of acoustic noise at the source regions in the plume shear layers and impingement regions. These CFD solvers are robust in capturing the acoustic fluctuations, but they are too dissipative to accurately resolve the propagation of the acoustic waves throughout the launch environment domain along the vehicle. A hybrid Computational Fluid Dynamics and Computational Aero-Acoustics (CFD/CAA) modeling framework has been developed to improve such liftoff acoustic environment predictions. The framework combines the existing highly-scalable NASA production CFD code, Loci/CHEM, with a high-order accurate discontinuous Galerkin (DG) solver, Loci/THRUST, developed in the same computational framework. Loci/THRUST employs a low dissipation, high-order, unstructured DG method to accurately propagate acoustic waves away from the source regions across large distances. The DG solver is currently capable of solving up to 4th order solutions for non-linear, conservative acoustic field propagation. Higher order boundary conditions are implemented to accurately model the reflection and refraction of acoustic waves on launch pad components. The DG solver accepts generalized unstructured meshes, enabling efficient application of common mesh generation tools for CHEM and THRUST simulations. The DG solution is coupled with the CFD solution at interface boundaries placed near the CFD acoustic source regions. Both simulations are executed simultaneously with coordinated boundary condition data exchange.

Improved Helicopter Rotor Performance Prediction through Loose and Tight CFD/CSD Coupling

NASA Astrophysics Data System (ADS)

Ickes, Jacob C.

Helicopters and other Vertical Take-Off or Landing (VTOL) vehicles exhibit an interesting combination of structural dynamic and aerodynamic phenomena which together drive the rotor performance. The combination of factors involved make simulating the rotor a challenging and multidisciplinary effort, and one which is still an active area of interest in the industry because of the money and time it could save during design. Modern tools allow the prediction of rotorcraft physics from first principles. Analysis of the rotor system with this level of accuracy provides the understanding necessary to improve its performance. There has historically been a divide between the comprehensive codes which perform aeroelastic rotor simulations using simplified aerodynamic models, and the very computationally intensive Navier-Stokes Computational Fluid Dynamics (CFD) solvers. As computer resources become more available, efforts have been made to replace the simplified aerodynamics of the comprehensive codes with the more accurate results from a CFD code. The objective of this work is to perform aeroelastic rotorcraft analysis using first-principles simulations for both fluids and structural predictions using tools available at the University of Toledo. Two separate codes are coupled together in both loose coupling (data exchange on a periodic interval) and tight coupling (data exchange each time step) schemes. To allow the coupling to be carried out in a reliable and efficient way, a Fluid-Structure Interaction code was developed which automatically performs primary functions of loose and tight coupling procedures. Flow phenomena such as transonics, dynamic stall, locally reversed flow on a blade, and Blade-Vortex Interaction (BVI) were simulated in this work. Results of the analysis show aerodynamic load improvement due to the inclusion of the CFD-based airloads in the structural dynamics analysis of the Computational Structural Dynamics (CSD) code. Improvements came in the form of improved peak/trough magnitude prediction, better phase prediction of these locations, and a predicted signal with a frequency content more like the flight test data than the CSD code acting alone. Additionally, a tight coupling analysis was performed as a demonstration of the capability and unique aspects of such an analysis. This work shows that away from the center of the flight envelope, the aerodynamic modeling of the CSD code can be replaced with a more accurate set of predictions from a CFD code with an improvement in the aerodynamic results. The better predictions come at substantially increased computational costs between 1,000 and 10,000 processor-hours.

Unsteady Velocity Measurements in the NASA Research Low Speed Axial Compressor: Smooth Wall Configuration

NASA Technical Reports Server (NTRS)

Lepicovsky, Jan

2007-01-01

The report is a collection of experimental unsteady data acquired in the first stage of the NASA Low Speed Axial Compressor in configuration with smooth (solid) wall treatment over the first rotor. The aim of the report is to present a reliable experimental data base that can be used for analysis of the compressor flow behavior, and hopefully help with further improvements of compressor CFD codes. All data analysis is strictly restricted to verification of reliability of the experimental data reported. The report is divided into six main sections. First two sections cover the low speed axial compressor, the basic instrumentation, and the in-house developed methodology of unsteady velocity measurements using a thermo-anemometric split-fiber probe. The next two sections contain experimental data presented as averaged radial distributions for three compressor operation conditions, including the distribution of the total temperature rise over the first rotor, and ensemble averages of unsteady flow data based on a rotor blade passage period. Ensemble averages based on the rotor revolution period, and spectral analysis of unsteady flow parameters are presented in the last two sections. The report is completed with two appendices where performance and dynamic response of thermo-anemometric probes is discussed.

Vortex Analysis of Intra-Aneurismal Flow in Cerebral Aneurysms

PubMed Central

Sunderland, Kevin; Haferman, Christopher; Chintalapani, Gouthami

2016-01-01

This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in “patient-specific” geometries, using computational fluid dynamics (CFD) simulations. Modified versions of known λ 2 and Q-criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle. No statistical differences exist in DVO or number of vortex cores between 5 terminal IAs and 5 sidewall IAs. No strong correlation exists between vortex core characteristics and geometric or hemodynamic characteristics of IAs. Statistical independence suggests this proposed method may provide novel IA information. However, threshold values used to determine the vortex core regions and resolution of velocity data influenced analysis outcomes and have to be addressed in future studies. In conclusions, preliminary results show that the proposed methodology may help give novel insight toward aneurismal flow characteristic and help in future risk assessment given more developments. PMID:27891172

Vortex Analysis of Intra-Aneurismal Flow in Cerebral Aneurysms.

PubMed

Sunderland, Kevin; Haferman, Christopher; Chintalapani, Gouthami; Jiang, Jingfeng

2016-01-01

This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in "patient-specific" geometries, using computational fluid dynamics (CFD) simulations. Modified versions of known λ 2 and Q -criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle. No statistical differences exist in DVO or number of vortex cores between 5 terminal IAs and 5 sidewall IAs. No strong correlation exists between vortex core characteristics and geometric or hemodynamic characteristics of IAs. Statistical independence suggests this proposed method may provide novel IA information. However, threshold values used to determine the vortex core regions and resolution of velocity data influenced analysis outcomes and have to be addressed in future studies. In conclusions, preliminary results show that the proposed methodology may help give novel insight toward aneurismal flow characteristic and help in future risk assessment given more developments.

Experimental measurement of the aerodynamic charateristics of two-dimensional airfoils for an unmanned aerial vehicle

NASA Astrophysics Data System (ADS)

Velazquez, Luis; Nožička, Jiří; Vavřín, Jan

2012-04-01

This paper is part of the development of an airfoil for an unmanned aerial vehicle (UAV) with internal propulsion system; the investigation involves the analysis of the aerodynamic performance for the gliding condition of two-dimensional airfoil models which have been tested. This development is based on the modification of a selected airfoil from the NACA four digits family. The modification of this base airfoil was made in order to create a blowing outlet with the shape of a step on the suction surface since the UAV will have an internal propulsion system. This analysis involved obtaining the lift, drag and pitching moment coefficients experimentally for the situation where there is not flow through the blowing outlet, called the no blowing condition by means of wind tunnel tests. The methodology to obtain the forces experimentally was through an aerodynamic wire balance. Obtained results were compared with numerical results by means of computational fluid dynamics (CFD) from references and found in very good agreement. Finally, a selection of the airfoil with the best aerodynamic performance is done and proposed for further analysis including the blowing condition.

The aerospace plane design challenge: Credible computational fluid dynamics results

NASA Technical Reports Server (NTRS)

Mehta, Unmeel B.

1990-01-01

Computational fluid dynamics (CFD) is necessary in the design processes of all current aerospace plane programs. Single-stage-to-orbit (STTO) aerospace planes with air-breathing supersonic combustion are going to be largely designed by means of CFD. The challenge of the aerospace plane design is to provide credible CFD results to work from, to assess the risk associated with the use of those results, and to certify CFD codes that produce credible results. To establish the credibility of CFD results used in design, the following topics are discussed: CFD validation vis-a-vis measurable fluid dynamics (MFD) validation; responsibility for credibility; credibility requirement; and a guide for establishing credibility. Quantification of CFD uncertainties helps to assess success risk and safety risks, and the development of CFD as a design tool requires code certification. This challenge is managed by designing the designers to use CFD effectively, by ensuring quality control, and by balancing the design process. For designing the designers, the following topics are discussed: how CFD design technology is developed; the reasons Japanese companies, by and large, produce goods of higher quality than the U.S. counterparts; teamwork as a new way of doing business; and how ideas, quality, and teaming can be brought together. Quality control for reducing the loss imparted to the society begins with the quality of the CFD results used in the design process, and balancing the design process means using a judicious balance of CFD and MFD.

Design and Analysis Tool for External-Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

Slater, John W.

2012-01-01

A computational tool named SUPIN has been developed to design and analyze external-compression supersonic inlets for aircraft at cruise speeds from Mach 1.6 to 2.0. The inlet types available include the axisymmetric outward-turning, two-dimensional single-duct, two-dimensional bifurcated-duct, and streamline-traced Busemann inlets. The aerodynamic performance is characterized by the flow rates, total pressure recovery, and drag. The inlet flowfield is divided into parts to provide a framework for the geometry and aerodynamic modeling and the parts are defined in terms of geometric factors. The low-fidelity aerodynamic analysis and design methods are based on analytic, empirical, and numerical methods which provide for quick analysis. SUPIN provides inlet geometry in the form of coordinates and surface grids useable by grid generation methods for higher-fidelity computational fluid dynamics (CFD) analysis. SUPIN is demonstrated through a series of design studies and CFD analyses were performed to verify some of the analysis results.

TADS: A CFD-based turbomachinery and analysis design system with GUI. Volume 2: User's manual

NASA Technical Reports Server (NTRS)

Myers, R. A.; Topp, D. A.; Delaney, R. A.

1995-01-01

The primary objective of this study was the development of a computational fluid dynamics (CFD) based turbomachinery airfoil analysis and design system, controlled by a graphical user interface (GUI). The computer codes resulting from this effort are referred to as the Turbomachinery Analysis and Design System (TADS). This document is intended to serve as a user's manual for the computer programs which comprise the TADS system. TADS couples a throughflow solver (ADPAC) with a quasi-3D blade-to-blade solver (RVCQ3D) in an interactive package. Throughflow analysis capability was developed in ADPAC through the addition of blade force and blockage terms to the governing equations. A GUI was developed to simplify user input and automate the many tasks required to perform turbomachinery analysis and design. The coupling of various programs was done in a way that alternative solvers or grid generators could be easily incorporated into the TADS framework.

Coupled CFD-Thermal Analysis of Erosion Patterns Resulting from Nozzle Wedgeouts on the SRTMV-N2

NASA Technical Reports Server (NTRS)

Ables, Catherine; Davis, Philip

2014-01-01

The objective of this analysis was to study the effects of the erosion patterns from the introduction of nozzle flaws machined into the nozzle of the SRTMV-N2 (Solid Rocket Test Motor V Nozzle 2). The SRTMV-N2 motor was a single segment static subscale solid rocket motor used to further develop the RSRMV (Redesigned Solid Rocket Motor V Segment). Two flaws or "wedgeouts" were placed in the nozzle inlet parallel to the ply angles of that section to study erosion effects. One wedgeout was placed in the nose cap region and the other placed in the inlet ring on the opposite side of the bondline, separated 180 degrees circumferentially. A coupled CFD (Computational Fluid Analysis)-thermal iterative analytical approach was utilized at the wedgeouts to analyze the erosion profile during the burn time. The iterative CFD thermal approach was applied at five second intervals throughout the motor burn. The coupled fluid thermal boundary conditions were derived from a steady state CFD solution at the beginning of the interval. The derived heat fluxes were then applied along the surface and a transient thermal solution was developed to characterize the material response over the specified interval. Eroded profiles of each of the nozzle's wedgeouts and the original contour were created at each of the specified intervals. The final iteration of the erosion profile showed that both wedgeouts were "washedout," indicating that the erosion profile of the wedgeout had rejoined the original eroded contour, leaving no trace of the wedgeouts post fire. This analytical assessment agreed with post-fire observations made of the SRTMV-N2 wedgeouts, which noted a smooth eroded contour.

Supersonic Free-Jet Combustion in a Ramjet Burner

NASA Technical Reports Server (NTRS)

Trefny, Charles J.; Dippold, Vance F., III

2010-01-01

A new dual-mode ramjet combustor concept intended for operation over a wide flight Mach number range is described. Subsonic combustion mode is similar to that of a traditional ram combustor which allows operation at higher efficiency, and to lower flight Mach numbers than current dual-mode scramjets. High speed mode is characterized by supersonic combustion in a free-jet that traverses the subsonic combustion chamber to a variable nozzle. The maximum flight Mach number of this scheme is governed largely by the same physics as its classical counterpart. Although a variable combustor exit aperture is required, the need for fuel staging to accommodate the combustion process is eliminated. Local heating from shock-boundary-layer interactions on combustor walls is also eliminated. Given the parallel nature of the present scheme, overall flowpath length is less than that of present dual-mode configurations. Cycle analysis was done to define the flowpath geometry for computational fluid dynamics (CFD) analysis, and then to determine performance based on the CFD results. CFD results for Mach 5, 8, and 12 flight conditions indicate stable supersonic free-jet formation and nozzle reattachment, thereby establishing the basic feasibility of the concept. These results also reveal the structure of, and interactions between the free-jet and recirculating combustion chamber flows. Performance based on these CFD results is slightly less than that of the constant-pressure-combustion cycle analysis primarily due to these interactions. These differences are quantified and discussed. Additional CFD results at the Mach 8 flight condition show the effects of nozzle throat area variation on combustion chamber pressure, flow structure, and performance. Calculations with constant temperature walls were also done to evaluate heat flux and overall heat loads. Aspects of the concept that warrant further study are outlined. These include diffuser design, ramjet operation, mode transition, loss mechanisms, and the effects of secondary flow for wall cooling and combustion chamber pressurization. Also recommended is an examination of system-level aspects such as weight, thermal management and rocket integration as well as alternate geometries and variable geometry schemes.

A combined CFD-experimental method for developing an erosion equation for both gas-sand and liquid-sand flows

NASA Astrophysics Data System (ADS)

Mansouri, Amir

The surface degradation of equipment due to consecutive impacts of abrasive particles carried by fluid flow is called solid particle erosion. Solid particle erosion occurs in many industries including oil and gas. In order to prevent abrupt failures and costly repairs, it is essential to predict the erosion rate and identify the locations of the equipment that are mostly at risk. Computational Fluid Dynamics (CFD) is a powerful tool for predicting the erosion rate. Erosion prediction using CFD analysis includes three steps: (1) obtaining flow solution, (2) particle tracking and calculating the particle impact speed and angle, and (3) relating the particle impact information to mass loss of material through an erosion equation. Erosion equations are commonly generated using dry impingement jet tests (sand-air), since the particle impact speed and angle are assumed not to deviate from conditions in the jet. However, in slurry flows, a wide range of particle impact speeds and angles are produced in a single slurry jet test with liquid and sand particles. In this study, a novel and combined CFD/experimental method for developing an erosion equation in slurry flows is presented. In this method, a CFD analysis is used to characterize the particle impact speed, angle, and impact rate at specific locations on the test sample. Then, the particle impact data are related to the measured erosion depth to achieve an erosion equation from submerged testing. Traditionally, it was assumed that the erosion equation developed based on gas testing can be used for both gas-sand and liquid-sand flows. The erosion equations developed in this work were implemented in a CFD code, and CFD predictions were validated for various test conditions. It was shown that the erosion equation developed based on slurry tests can significantly improve the local thickness loss prediction in slurry flows. Finally, a generalized erosion equation is proposed which can be used to predict the erosion rate in gas-sand, water-sand and viscous liquid-sand flows with high accuracy. Furthermore, in order to gain a better understanding of the erosion mechanism, a comprehensive experimental study was conducted to investigate the important factors influencing the erosion rate in gas-sand and slurry flows. The wear pattern and total erosion ratio were measured in a direct impingement jet geometry (for both dry impact and submerged impingement jets). The effects of fluid viscosity, abrasive particle size, particle impact speed, jet inclination angle, standoff distance, sand concentration, and exposure time were investigated. Also, the eroded samples were studied with Scanning Electron Microscopy (SEM) to understand the erosion micro-structure. Also, the sand particle impact speed and angle were measured using a Particle Image Velocimetry (PIV) system. The measurements were conducted in two types of erosion testers (gas-solid and liquid-solid impinging jets). The Particle Tracking Velocimetry (PTV) technique was utilized which is capable of tracking individual small particles. Moreover, CFD modeling was performed to predict the particle impact data. Very good agreement between the CFD results and PTV measurements was observed.

Navier-Stokes flow field analysis of compressible flow in a high pressure safety relief valve

NASA Technical Reports Server (NTRS)

Vu, Bruce; Wang, Ten-See; Shih, Ming-Hsin; Soni, Bharat

1993-01-01

The objective of this study is to investigate the complex three-dimensional flowfield of an oxygen safety pressure relieve valve during an incident, with a computational fluid dynamic (CFD) analysis. Specifically, the analysis will provide a flow pattern that would lead to the expansion of the eventual erosion pattern of the hardware, so as to combine it with other findings to piece together a most likely scenario for the investigation. The CFD model is a pressure based solver. An adaptive upwind difference scheme is employed for the spatial discretization, and a predictor, multiple corrector method is used for the velocity-pressure coupling. The computational result indicated vortices formation near the opening of the valve which matched the erosion pattern of the damaged hardware.

CFD Modeling of Water Flow through Sudden Contraction and Expansion in a Horizontal Pipe

ERIC Educational Resources Information Center

Kaushik, V. V. R.; Ghosh, S.; Das, G.; Das, P. K.

2011-01-01

This paper deals with the use of commercial CFD software in teaching graduate level computational fluid dynamics. FLUENT 6.3.26 was chosen as the CFD software to teach students the entire CFD process in a single course. The course objective is to help students to learn CFD, use it in some practical problems and analyze as well as validate the…

Aeroacoustic Codes for Rotor Harmonic and BVI Noise. CAMRAD.Mod1/HIRES: Methodology and Users' Manual

NASA Technical Reports Server (NTRS)

Boyd, D. Douglas, Jr.; Brooks, Thomas F.; Burley, Casey L.; Jolly, J. Ralph, Jr.

1998-01-01

This document details the methodology and use of the CAMRAD.Mod1/HIRES codes, which were developed at NASA Langley Research Center for the prediction of helicopter harmonic and Blade-Vortex Interaction (BVI) noise. CANMAD.Mod1 is a substantially modified version of the performance/trim/wake code CANMAD. High resolution blade loading is determined in post-processing by HIRES and an associated indicial aerodynamics code. Extensive capabilities of importance to noise prediction accuracy are documented, including a new multi-core tip vortex roll-up wake model, higher harmonic and individual blade control, tunnel and fuselage correction input, diagnostic blade motion input, and interfaces for acoustic and CFD aerodynamics codes. Modifications and new code capabilities are documented with examples. A users' job preparation guide and listings of variables and namelists are given.

Numerical study of external burning flowfields

NASA Technical Reports Server (NTRS)

Bittner, Robert D.; Mcclinton, Charles R.

1991-01-01

This paper demonstrates the successful application of CFD to modeling an external burning flowfield. The study used the 2D, 3D, and PNS versions of the SPARK code. Various grids, boundary conditions, and ignition methodologies have been employed. Flameholding was achieved through the use of a subsonic outflow condition and a hot block located behind the step to ignite the fuel. Since the resulting burning produces a large subsonic region downstream of the cowl, this entire surface can be pressurized to the level of the back pressure. An evaluation of interactions between the ramjet exhaust and the external burning products demonstrate the complexity of this design issue. Ths code is now capable of evaluating the external burning effectiveness for flight vehicles using simple injector schemes, and the methodology can be readily applied to other external burning designs.

Sonic Boom Mitigation Through Aircraft Design and Adjoint Methodology

NASA Technical Reports Server (NTRS)

Rallabhandi, Siriam K.; Diskin, Boris; Nielsen, Eric J.

2012-01-01

This paper presents a novel approach to design of the supersonic aircraft outer mold line (OML) by optimizing the A-weighted loudness of sonic boom signature predicted on the ground. The optimization process uses the sensitivity information obtained by coupling the discrete adjoint formulations for the augmented Burgers Equation and Computational Fluid Dynamics (CFD) equations. This coupled formulation links the loudness of the ground boom signature to the aircraft geometry thus allowing efficient shape optimization for the purpose of minimizing the impact of loudness. The accuracy of the adjoint-based sensitivities is verified against sensitivities obtained using an independent complex-variable approach. The adjoint based optimization methodology is applied to a configuration previously optimized using alternative state of the art optimization methods and produces additional loudness reduction. The results of the optimizations are reported and discussed.

CFD and PIV Analysis of Hemodynamics in a Growing Intracranial Aneurysm

PubMed Central

Raschi, Marcelo; Mut, Fernando; Byrne, Greg; Putman, Christopher M.; Tateshima, Satoshi; Viñuela, Fernando; Tanoue, Tetsuya; Tanishita, Kazuo; Cebral, Juan R.

2011-01-01

Hemodynamics is thought to be a fundamental factor in the formation, progression and rupture of cerebral aneurysms. Understanding these mechanisms is important to improve their rupture risk assessment and treatment. In this study we analyze the blood flow field in a growing cerebral aneurysm using experimental particle image velocimetry (PIV) and computational fluid dynamics (CFD) techniques. Patient-specific models were constructed from longitudinal 3D computed tomography angiography (CTA) images acquired at one-year intervals. Physical silicone models were constructed from the CTA images using rapid prototyping techniques and pulsatile flow fields were measured with PIV. Corresponding CFD models were created and run under matching flow conditions. Both flow fields were aligned, interpolated, and compared qualitatively by inspection and quantitatively by defining similarity measures between the PIV and CFD vector fields. Results showed that both flow fields were in good agreement. Specifically, both techniques provided consistent representations of the main intra-aneurysmal flow structures, and their change during the geometric evolution of the aneurysm. Despite differences observed mainly in the near wall region and the inherent limitations of each technique, the information derived is consistent and can be used to study the role of hemodynamics in the natural history of intracranial aneurysms. PMID:22548127

Modeling of High Speed Reacting Flows: Established Practices and Future Challenges

NASA Technical Reports Server (NTRS)

Baurle, R. A.

2004-01-01

Computational fluid dynamics (CFD) has proven to be an invaluable tool for the design and analysis of high- speed propulsion devices. Massively parallel computing, together with the maturation of robust CFD codes, has made it possible to perform simulations of complete engine flowpaths. Steady-state Reynolds-Averaged Navier-Stokes simulations are now routinely used in the scramjet engine development cycle to determine optimal fuel injector arrangements, investigate trends noted during testing, and extract various measures of engine efficiency. Unfortunately, the turbulence and combustion models used in these codes have not changed significantly over the past decade. Hence, the CFD practitioner must often rely heavily on existing measurements (at similar flow conditions) to calibrate model coefficients on a case- by-case basis. This paper provides an overview of the modeled equations typically employed by commercial- quality CFD codes for high-speed combustion applications. Careful attention is given to the approximations employed for each of the unclosed terms in the averaged equation set. The salient features (and shortcomings) of common models used to close these terms are covered in detail, and several academic efforts aimed at addressing these shortcomings are discussed.

Virtual Diagnostics Interface: Real Time Comparison of Experimental Data and CFD Predictions for a NASA Ares I-Like Vehicle

NASA Technical Reports Server (NTRS)

Schwartz, Richard J.; Fleming, Gary A.

2007-01-01

Virtual Diagnostics Interface technology, or ViDI, is a suite of techniques utilizing image processing, data handling and three-dimensional computer graphics. These techniques aid in the design, implementation, and analysis of complex aerospace experiments. LiveView3D is a software application component of ViDI used to display experimental wind tunnel data in real-time within an interactive, three-dimensional virtual environment. The LiveView3D software application was under development at NASA Langley Research Center (LaRC) for nearly three years. LiveView3D recently was upgraded to perform real-time (as well as post-test) comparisons of experimental data with pre-computed Computational Fluid Dynamics (CFD) predictions. This capability was utilized to compare experimental measurements with CFD predictions of the surface pressure distribution of the NASA Ares I Crew Launch Vehicle (CLV) - like vehicle when tested in the NASA LaRC Unitary Plan Wind Tunnel (UPWT) in December 2006 - January 2007 timeframe. The wind tunnel tests were conducted to develop a database of experimentally-measured aerodynamic performance of the CLV-like configuration for validation of CFD predictive codes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quon, Eliot; Platt, Andrew; Yu, Yi-Hsiang

Extreme loads are often a key cost driver for wave energy converters (WECs). As an alternative to exhaustive Monte Carlo or long-term simulations, the most likely extreme response (MLER) method allows mid- and high-fidelity simulations to be used more efficiently in evaluating WEC response to events at the edges of the design envelope, and is therefore applicable to system design analysis. The study discussed in this paper applies the MLER method to investigate the maximum heave, pitch, and surge force of a point absorber WEC. Most likely extreme waves were obtained from a set of wave statistics data based onmore » spectral analysis and the response amplitude operators (RAOs) of the floating body; the RAOs were computed from a simple radiation-and-diffraction-theory-based numerical model. A weakly nonlinear numerical method and a computational fluid dynamics (CFD) method were then applied to compute the short-term response to the MLER wave. Effects of nonlinear wave and floating body interaction on the WEC under the anticipated 100-year waves were examined by comparing the results from the linearly superimposed RAOs, the weakly nonlinear model, and CFD simulations. Overall, the MLER method was successfully applied. In particular, when coupled to a high-fidelity CFD analysis, the nonlinear fluid dynamics can be readily captured.« less

Application of computational fluid dynamics to closed-loop bioreactors: I. Characterization and simulation of fluid-flow pattern and oxygen transfer.

PubMed

Littleton, Helen X; Daigger, Glen T; Strom, Peter F

2007-06-01

A full-scale, closed-loop bioreactor (Orbal oxidation ditch, Envirex brand technologies, Siemens, Waukesha, Wisconsin), previously examined for simultaneous biological nutrient removal (SBNR), was further evaluated using computational fluid dynamics (CFD). A CFD model was developed first by imparting the known momentum (calculated by tank fluid velocity and mass flowrate) to the fluid at the aeration disc region. Oxygen source (aeration) and sink (consumption) terms were introduced, and statistical analysis was applied to the CFD simulation results. The CFD model was validated with field data obtained from a test tank and a full-scale tank. The results indicated that CFD could predict the mixing pattern in closed-loop bioreactors. This enables visualization of the flow pattern, both with regard to flow velocity and dissolved-oxygen-distribution profiles. The velocity and oxygen-distribution gradients suggested that the flow patterns produced by directional aeration in closed-loop bioreactors created a heterogeneous environment that can result in dissolved oxygen variations throughout the bioreactor. Distinct anaerobic zones on a macroenvironment scale were not observed, but it is clear that, when flow passed around curves, a secondary spiral flow was generated. This second current, along with the main recirculation flow, could create alternating anaerobic and aerobic conditions vertically and horizontally, which would allow SBNR to occur. Reliable SBNR performance in Orbal oxidation ditches may be a result, at least in part, of such a spatially varying environment.

Emerging CFD Capabilities and Outlook: A NASA Langley Perspective

NASA Technical Reports Server (NTRS)

Biedron, Robert T.; Pao, S. Paul; Thomas, James L.

2004-01-01

COMSAC goals include increasing the acceptance of CFD as a viable tool for S&C predictions, as well as to focus CFD development and improvement towards the needs of the S&C community. We view this as a symbiotic relationship, with increasing improvement of CFD promoting increasing acceptance by the S&C community, and increasing acceptance spurring further improvements. In this presentation we want to provide an overview for the non CFD expert of current CFD strengths and weaknesses, as well as to highlight a few emerging capabilities that we feel will lead toward increased usefulness in S&C applications.

Comprehensive Forced Response Analysis of J2X Turbine Bladed-Discs with 360 Degree Variation in CFD Loading

NASA Technical Reports Server (NTRS)

Elrod, David; Christensen, Eric; Brown, Andrew

2011-01-01

The temporal frequency content of the dynamic pressure predicted by a 360 degree computational fluid dynamics (CFD) analysis of a turbine flow field provides indicators of forcing function excitation frequencies (e.g., multiples of blade pass frequency) for turbine components. For the Pratt and Whitney Rocketdyne J-2X engine turbopumps, Campbell diagrams generated using these forcing function frequencies and the results of NASTRAN modal analyses show a number of components with modes in the engine operating range. As a consequence, forced response and static analyses are required for the prediction of combined stress, high cycle fatigue safety factors (HCFSF). Cyclically symmetric structural models have been used to analyze turbine vane and blade rows, not only in modal analyses, but also in forced response and static analyses. Due to the tortuous flow pattern in the turbine, dynamic pressure loading is not cyclically symmetric. Furthermore, CFD analyses predict dynamic pressure waves caused by adjacent and non-adjacent blade/vane rows upstream and downstream of the row analyzed. A MATLAB script has been written to calculate displacements due to the complex cyclically asymmetric dynamic pressure components predicted by CFD analysis, for all grids in a blade/vane row, at a chosen turbopump running speed. The MATLAB displacements are then read into NASTRAN, and dynamic stresses are calculated, including an adjustment for possible mistuning. In a cyclically symmetric NASTRAN static analysis, static stresses due to centrifugal, thermal, and pressure loading at the mode running speed are calculated. MATLAB is used to generate the HCFSF at each grid in the blade/vane row. When compared to an approach assuming cyclic symmetry in the dynamic flow field, the current approach provides better assurance that the worst case safety factor has been identified. An extended example for a J-2X turbopump component is provided.

Simulation of Flow around Isolated Helicopter Fuselage

NASA Astrophysics Data System (ADS)

Kusyumov, A. N.; Mikhailov, S. A.; Romanova, E. V.; Garipov, A. O.; Nikolaev, E. I.; Barakos, G.

2013-04-01

Low fuselage drag has always been a key target of helicopter manufacturers. Therefore, this paper focuses on CFD predictions of the drag of several components of a typical helicopter fuselage. In the first section of the paper, validation of the obtained CFD predictions is carried out using wind tunnel measurements. The measurements were carried out at the Kazan National Research Technical University n.a. A. Tupolev. The second section of the paper is devoted to the analysis of drag contributions of several components of the ANSAT helicopter prototype fuselage using the RANS approach. For this purpose, several configurations of fuselages are considered with different levels of complexity including exhausts and skids. Depending on the complexity of the considered configuration and CFD mesh both the multi-block structured HMB solver and the unstructured commercial tool Fluent are used. Finally, the effect of an actuator disk on the predicted drag is addressed.

Verification, Validation, and Solution Quality in Computational Physics: CFD Methods Applied to Ice Sheet Physics

NASA Technical Reports Server (NTRS)

Thompson, David E.

2005-01-01

Procedures and methods for veri.cation of coding algebra and for validations of models and calculations used in the aerospace computational fluid dynamics (CFD) community would be ef.cacious if used by the glacier dynamics modeling community. This paper presents some of those methods, and how they might be applied to uncertainty management supporting code veri.cation and model validation for glacier dynamics. The similarities and differences between their use in CFD analysis and the proposed application of these methods to glacier modeling are discussed. After establishing sources of uncertainty and methods for code veri.cation, the paper looks at a representative sampling of veri.cation and validation efforts that are underway in the glacier modeling community, and establishes a context for these within an overall solution quality assessment. Finally, a vision of a new information architecture and interactive scienti.c interface is introduced and advocated.

Flow visualization methods for field test verification of CFD analysis of an open gloveport

DOE PAGES

Strons, Philip; Bailey, James L.

2017-01-01

Anemometer readings alone cannot provide a complete picture of air flow patterns at an open gloveport. Having a means to visualize air flow for field tests in general provides greater insight by indicating direction in addition to the magnitude of the air flow velocities in the region of interest. Furthermore, flow visualization is essential for Computational Fluid Dynamics (CFD) verification, where important modeling assumptions play a significant role in analyzing the chaotic nature of low-velocity air flow. A good example is shown Figure 1, where an unexpected vortex pattern occurred during a field test that could not have been measuredmore » relying only on anemometer readings. Here by, observing and measuring the patterns of the smoke flowing into the gloveport allowed the CFD model to be appropriately updated to match the actual flow velocities in both magnitude and direction.« less

CFD Data Sets on the WWW for Education and Testing

NASA Technical Reports Server (NTRS)

Globus, Al; Lasinski, T. A. (Technical Monitor)

1995-01-01

The Numerical Aerodynamic Simulation (NAS) Systems Division at NASA Ames Research Center has begun the development of a Computational Fluid Dynamics (CFD) data set archive on the World Wide Web (WWW) at URL http://www.nas.nasa.gov/NAS/DataSets/. Data sets are integrated with related information such as research papers, metadata, visualizations, etc. In this paper, four classes of users are identified and discussed: students, visualization developers, CFD practitioners, and management. Bandwidth and security issues are briefly reviewed and the status of the archive as of May 1995 is examined. Routine network distribution of data sets is likely to have profound implications for the conduct of science. The exact nature of these changes is subject to speculation, but the ability for anyone to examine the data, in addition to the investigator's analysis, may well play an important role in the future.

CFD Simulation of the Space Shuttle Launch Vehicle with Booster Separation Motor and Reaction Control System Plumes

NASA Technical Reports Server (NTRS)

Gea, L. M.; Vicker, D.

2006-01-01

The primary objective of this paper is to demonstrate the capability of computational fluid dynamics (CFD) to simulate a very complicated flow field encountered during the space shuttle ascent. The flow field features nozzle plumes from booster separation motor (BSM) and reaction control system (RCS) jets with a supersonic incoming cross flow at speed of Mach 4. The overset Navier-Stokes code OVERFLOW, was used to simulate the flow field surrounding the entire space shuttle launch vehicle (SSLV) with high geometric fidelity. The variable gamma option was chosen due to the high temperature nature of nozzle flows and different plume species. CFD predicted Mach contours are in good agreement with the schlieren photos from wind tunnel test. Flow fields are discussed in detail and the results are used to support the debris analysis for the space shuttle Return To Flight (RTF) task.

CFD Simulation of the Space Shuttle Launch Vehicle with Booster Separation Motor and Reaction Control Plumes

NASA Technical Reports Server (NTRS)

Gea, L. M.; Vicker, D.

2006-01-01

The primary objective of this paper is to demonstrate the capability of computational fluid dynamics (CFD) to simulate a very complicated flow field encountered during the space shuttle ascent. The flow field features nozzle plumes from booster separation motor (BSM) and reaction control system (RCS) jets with a supersonic incoming cross flow at speed of Mach 4. The overset Navier-Stokes code OVERFLOW, was used to simulate the flow field surrounding the entire space shuttle launch vehicle (SSLV) with high geometric fidelity. The variable gamma option was chosen due to the high temperature nature of nozzle flows and different plume species. CFD predicted Mach contours are in good agreement with the schlieren photos from wind tunnel test. Flow fields are discussed in detail and the results are used to support the debris analysis for the space shuttle Return To Flight (RTF) task.

CFD analysis of the two-phase bubbly flow characteristics in helically coiled rectangular and circular tube heat exchangers

NASA Astrophysics Data System (ADS)

Hussain, Alamin; Fsadni, Andrew M.

2016-03-01

Due to their ease of manufacture, high heat transfer efficiency and compact design, helically coiled heat exchangers are increasingly being adopted in a number of industries. The higher heat transfer efficiency over straight pipes is due to the secondary flow that develops as a result of the centrifugal force. In spite of the widespread use of helically coiled heat exchangers, and the presence of bubbly two-phase flow in a number of systems, very few studies have investigated the resultant flow characteristics. This paper will therefore present the results of CFD simulations for the two-phase bubbly flow in helically coiled heat exchangers as a function of the volumetric void fraction and the tube cross-section design. The CFD results are compared to the scarce flow visualisation experimental results available in the open literature.

CFD analysis of hypersonic, chemically reacting flow fields

NASA Technical Reports Server (NTRS)

Edwards, T. A.

1993-01-01

Design studies are underway for a variety of hypersonic flight vehicles. The National Aero-Space Plane will provide a reusable, single-stage-to-orbit capability for routine access to low earth orbit. Flight-capable satellites will dip into the atmosphere to maneuver to new orbits, while planetary probes will decelerate at their destination by atmospheric aerobraking. To supplement limited experimental capabilities in the hypersonic regime, computational fluid dynamics (CFD) is being used to analyze the flow about these configurations. The governing equations include fluid dynamic as well as chemical species equations, which are being solved with new, robust numerical algorithms. Examples of CFD applications to hypersonic vehicles suggest an important role this technology will play in the development of future aerospace systems. The computational resources needed to obtain solutions are large, but solution adaptive grids, convergence acceleration, and parallel processing may make run times manageable.

Toward a CFD nose-to-tail capability - Hypersonic unsteady Navier-Stokes code validation

NASA Technical Reports Server (NTRS)

Edwards, Thomas A.; Flores, Jolen

1989-01-01

Computational fluid dynamics (CFD) research for hypersonic flows presents new problems in code validation because of the added complexity of the physical models. This paper surveys code validation procedures applicable to hypersonic flow models that include real gas effects. The current status of hypersonic CFD flow analysis is assessed with the Compressible Navier-Stokes (CNS) code as a case study. The methods of code validation discussed to beyond comparison with experimental data to include comparisons with other codes and formulations, component analyses, and estimation of numerical errors. Current results indicate that predicting hypersonic flows of perfect gases and equilibrium air are well in hand. Pressure, shock location, and integrated quantities are relatively easy to predict accurately, while surface quantities such as heat transfer are more sensitive to the solution procedure. Modeling transition to turbulence needs refinement, though preliminary results are promising.