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.

Aeroelastic Modeling of a Nozzle Startup Transient

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2014-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,

Analysis, approximation, and computation of a coupled solid/fluid temperature control problem

NASA Technical Reports Server (NTRS)

Gunzburger, Max D.; Lee, Hyung C.

1993-01-01

An optimization problem is formulated motivated by the desire to remove temperature peaks, i.e., 'hot spots', along the bounding surfaces of containers of fluid flows. The heat equation of the solid container is coupled to the energy equations for the fluid. Heat sources can be located in the solid body, the fluid, or both. Control is effected by adjustments to the temperature of the fluid at the inflow boundary. Both mathematical analyses and computational experiments are given.

Automated Static Culture System Cell Module Mixing Protocol and Computational Fluid Dynamics Analysis

NASA Technical Reports Server (NTRS)

Kleis, Stanley J.; Truong, Tuan; Goodwin, Thomas J,

2004-01-01

This report is a documentation of a fluid dynamic analysis of the proposed Automated Static Culture System (ASCS) cell module mixing protocol. The report consists of a review of some basic fluid dynamics principles appropriate for the mixing of a patch of high oxygen content media into the surrounding media which is initially depleted of oxygen, followed by a computational fluid dynamics (CFD) study of this process for the proposed protocol over a range of the governing parameters. The time histories of oxygen concentration distributions and mechanical shear levels generated are used to characterize the mixing process for different parameter values.

Internal fluid mechanics research on supercomputers for aerospace propulsion systems

NASA Technical Reports Server (NTRS)

Miller, Brent A.; Anderson, Bernhard H.; Szuch, John R.

1988-01-01

The Internal Fluid Mechanics Division of the NASA Lewis Research Center is combining the key elements of computational fluid dynamics, aerothermodynamic experiments, and advanced computational technology to bring internal computational fluid mechanics (ICFM) to a state of practical application for aerospace propulsion systems. The strategies used to achieve this goal are to: (1) pursue an understanding of flow physics, surface heat transfer, and combustion via analysis and fundamental experiments, (2) incorporate improved understanding of these phenomena into verified 3-D CFD codes, and (3) utilize state-of-the-art computational technology to enhance experimental and CFD research. Presented is an overview of the ICFM program in high-speed propulsion, including work in inlets, turbomachinery, and chemical reacting flows. Ongoing efforts to integrate new computer technologies, such as parallel computing and artificial intelligence, into high-speed aeropropulsion research are described.

Transient thermal analysis of fluid systems

NASA Technical Reports Server (NTRS)

Chandler, G. D.; Trust, R. D.

1977-01-01

Computer program performs transient thermal analysis of any 2-node to 200-node-thermal network, which transports heat by fluid flow convection. Program can be modified to add conduction along tubes and radiation.

Multiphysics Analysis of a Solid-Core Nuclear Thermal Engine Thrust Chamber

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Canabal, Francisco; Cheng, Gary; Chen, Yen-Sen

2006-01-01

The objective of this effort is to develop an efficient and accurate thermo-fluid computational methodology to predict environments for a hypothetical solid-core, nuclear thermal engine thrust chamber. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics methodology. Formulations for heat transfer in solids and porous media were implemented and anchored. A two-pronged approach was employed in this effort: A detailed thermo-fluid analysis on a multi-channel flow element for mid-section corrosion investigation; and a global modeling of the thrust chamber to understand the effect of hydrogen dissociation and recombination on heat transfer and thrust performance. The formulations and preliminary results on both aspects are presented.

Overview of MSFC's Applied Fluid Dynamics Analysis Group Activities

NASA Technical Reports Server (NTRS)

Garcia, Roberto; Griffin, Lisa; Williams, Robert

2002-01-01

This viewgraph report presents an overview of activities and accomplishments of NASA's Marshall Space Flight Center's Applied Fluid Dynamics Analysis Group. Expertise in this group focuses on high-fidelity fluids design and analysis with application to space shuttle propulsion and next generation launch technologies. Topics covered include: computational fluid dynamics research and goals, turbomachinery research and activities, nozzle research and activities, combustion devices, engine systems, MDA development and CFD process improvements.

Computer-aided-engineering system for modeling and analysis of ECLSS integration testing

NASA Technical Reports Server (NTRS)

Sepahban, Sonbol

1987-01-01

The accurate modeling and analysis of two-phase fluid networks found in environmental control and life support systems is presently undertaken by computer-aided engineering (CAE) techniques whose generalized fluid dynamics package can solve arbitrary flow networks. The CAE system for integrated test bed modeling and analysis will also furnish interfaces and subsystem/test-article mathematical models. Three-dimensional diagrams of the test bed are generated by the system after performing the requisite simulation and analysis.

Overview of Sensitivity Analysis and Shape Optimization for Complex Aerodynamic Configurations

NASA Technical Reports Server (NTRS)

Newman, Perry A.; Newman, James C., III; Barnwell, Richard W.; Taylor, Arthur C., III; Hou, Gene J.-W.

1998-01-01

This paper presents a brief overview of some of the more recent advances in steady aerodynamic shape-design sensitivity analysis and optimization, based on advanced computational fluid dynamics. The focus here is on those methods particularly well- suited to the study of geometrically complex configurations and their potentially complex associated flow physics. When nonlinear state equations are considered in the optimization process, difficulties are found in the application of sensitivity analysis. Some techniques for circumventing such difficulties are currently being explored and are included here. Attention is directed to methods that utilize automatic differentiation to obtain aerodynamic sensitivity derivatives for both complex configurations and complex flow physics. Various examples of shape-design sensitivity analysis for unstructured-grid computational fluid dynamics algorithms are demonstrated for different formulations of the sensitivity equations. Finally, the use of advanced, unstructured-grid computational fluid dynamics in multidisciplinary analyses and multidisciplinary sensitivity analyses within future optimization processes is recommended and encouraged.

Direct differentiation of the quasi-incompressible fluid formulation of fluid-structure interaction using the PFEM

NASA Astrophysics Data System (ADS)

Zhu, Minjie; Scott, Michael H.

2017-07-01

Accurate and efficient response sensitivities for fluid-structure interaction (FSI) simulations are important for assessing the uncertain response of coastal and off-shore structures to hydrodynamic loading. To compute gradients efficiently via the direct differentiation method (DDM) for the fully incompressible fluid formulation, approximations of the sensitivity equations are necessary, leading to inaccuracies of the computed gradients when the geometry of the fluid mesh changes rapidly between successive time steps or the fluid viscosity is nonzero. To maintain accuracy of the sensitivity computations, a quasi-incompressible fluid is assumed for the response analysis of FSI using the particle finite element method and DDM is applied to this formulation, resulting in linearized equations for the response sensitivity that are consistent with those used to compute the response. Both the response and the response sensitivity can be solved using the same unified fractional step method. FSI simulations show that although the response using the quasi-incompressible and incompressible fluid formulations is similar, only the quasi-incompressible approach gives accurate response sensitivity for viscous, turbulent flows regardless of time step size.

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.

The Fourth Annual Thermal and Fluids Analysis Workshop

NASA Technical Reports Server (NTRS)

1992-01-01

The Fourth Annual Thermal and Fluids Analysis Workshop was held from August 17-21, 1992, at NASA Lewis Research Center. The workshop consisted of classes, vendor demonstrations, and paper sessions. The classes and vendor demonstrations provided participants with the information on widely used tools for thermal and fluids analysis. The paper sessions provided a forum for the exchange of information and ideas among thermal and fluids analysts. Paper topics included advances and uses of established thermal and fluids computer codes (such as SINDA and TRASYS) as well as unique modeling techniques and applications.

Faster Aerodynamic Simulation With Cart3D

NASA Technical Reports Server (NTRS)

2003-01-01

A NASA-developed aerodynamic simulation tool is ensuring the safety of future space operations while providing designers and engineers with an automated, highly accurate computer simulation suite. Cart3D, co-winner of NASA's 2002 Software of the Year award, is the result of over 10 years of research and software development conducted by Michael Aftosmis and Dr. John Melton of Ames Research Center and Professor Marsha Berger of the Courant Institute at New York University. Cart3D offers a revolutionary approach to computational fluid dynamics (CFD), the computer simulation of how fluids and gases flow around an object of a particular design. By fusing technological advancements in diverse fields such as mineralogy, computer graphics, computational geometry, and fluid dynamics, the software provides a new industrial geometry processing and fluid analysis capability with unsurpassed automation and efficiency.

Multiphysics Thrust Chamber Modeling for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Cheng, Gary; Chen, Yen-Sen

2006-01-01

The objective of this effort is to develop an efficient and accurate thermo-fluid computational methodology to predict environments for a solid-core, nuclear thermal engine thrust chamber. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation. A two-pronged approach is employed in this effort: A detailed thermo-fluid analysis on a multi-channel flow element for mid-section corrosion investigation; and a global modeling of the thrust chamber to understand the effect of heat transfer on thrust performance. Preliminary results on both aspects are presented.

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

EPA Science Inventory

This paper discusses a framework for fine-scale CFD modeling that may be developed to complement the present Community Multi-scale Air Quality (CMAQ) modeling system which itself is a computational fluid dynamics model. A goal of this presentation is to stimulate discussions on w...

Computational fluid dynamics characterization of a novel mixed cell raceway design

USDA-ARS?s Scientific Manuscript database

Computational fluid dynamics (CFD) analysis was performed on a new type of mixed cell raceway (MCR) that incorporates longitudinal plug flow using inlet and outlet weirs for the primary fraction of the total flow. As opposed to regular MCR wherein vortices are entirely characterized by the boundary ...

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC, year 2 quarter 1 progress report.

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

Lottes, S.A.; Bojanowski, C.; Shen, J.

2012-04-09

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well-benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water effects on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to improve design allowing for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, CFD analysis of the operation of the wind tunnel in the TFHRC wind engineering laboratory. This quarterly report documents technical progress on the project tasks for the period of October through December 2011.« less

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC, year 2 quarter 2 progress report

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

Lottes, S.A.; Bojanowski, C.; Shen, J.

2012-06-28

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water effects on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to improve design allowing for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, CFD analysis of the operation of the wind tunnel in the TFHRC wind engineering laboratory. This quarterly report documents technical progress on the project tasks for the period of January through March 2012.« less

Computational Fluid Dynamics Analysis of Thoracic Aortic Dissection

NASA Astrophysics Data System (ADS)

Tang, Yik; Fan, Yi; Cheng, Stephen; Chow, Kwok

2011-11-01

Thoracic Aortic Dissection (TAD) is a cardiovascular disease with high mortality. An aortic dissection is formed when blood infiltrates the layers of the vascular wall, and a new artificial channel, the false lumen, is created. The expansion of the blood vessel due to the weakened wall enhances the risk of rupture. Computational fluid dynamics analysis is performed to study the hemodynamics of this pathological condition. Both idealized geometry and realistic patient configurations from computed tomography (CT) images are investigated. Physiological boundary conditions from in vivo measurements are employed. Flow configuration and biomechanical forces are studied. Quantitative analysis allows clinicians to assess the risk of rupture in making decision regarding surgical intervention.

Numerical analysis on the action of centrifuge force in magnetic fluid rotating shaft seals

NASA Astrophysics Data System (ADS)

Zou, Jibin; Li, Xuehui; Lu, Yongping; Hu, Jianhui

2002-11-01

The magnetic fluid seal is suitable for high-speed rotating shaft seal applications. Centrifuge force will have evident influence on magnetic fluid rotating shaft seals. The seal capacity of the rotating shaft seal can be improved or increased by some measures. Through hydrodynamic analysis the moving status of the magnetic fluid is worked out. By numerical method, the magnetic field and the isobars in the magnetic fluid of a seal device are computed. Then the influence of the centrifuge force on the magnetic fluid seal is calculated quantitatively.

Data Point Averaging for Computational Fluid Dynamics Data

NASA Technical Reports Server (NTRS)

Norman, Jr., David (Inventor)

2016-01-01

A system and method for generating fluid flow parameter data for use in aerodynamic heating analysis. Computational fluid dynamics data is generated for a number of points in an area on a surface to be analyzed. Sub-areas corresponding to areas of the surface for which an aerodynamic heating analysis is to be performed are identified. A computer system automatically determines a sub-set of the number of points corresponding to each of the number of sub-areas and determines a value for each of the number of sub-areas using the data for the sub-set of points corresponding to each of the number of sub-areas. The value is determined as an average of the data for the sub-set of points corresponding to each of the number of sub-areas. The resulting parameter values then may be used to perform an aerodynamic heating analysis.

Data Point Averaging for Computational Fluid Dynamics Data

NASA Technical Reports Server (NTRS)

Norman, David, Jr. (Inventor)

2014-01-01

A system and method for generating fluid flow parameter data for use in aerodynamic heating analysis. Computational fluid dynamics data is generated for a number of points in an area on a surface to be analyzed. Sub-areas corresponding to areas of the surface for which an aerodynamic heating analysis is to be performed are identified. A computer system automatically determines a sub-set of the number of points corresponding to each of the number of sub-areas and determines a value for each of the number of sub-areas using the data for the sub-set of points corresponding to each of the number of sub-areas. The value is determined as an average of the data for the sub-set of points corresponding to each of the number of sub-areas. The resulting parameter values then may be used to perform an aerodynamic heating analysis.

Methods for simulation-based analysis of fluid-structure interaction.

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

Barone, Matthew Franklin; Payne, Jeffrey L.

2005-10-01

Methods for analysis of fluid-structure interaction using high fidelity simulations are critically reviewed. First, a literature review of modern numerical techniques for simulation of aeroelastic phenomena is presented. The review focuses on methods contained within the arbitrary Lagrangian-Eulerian (ALE) framework for coupling computational fluid dynamics codes to computational structural mechanics codes. The review treats mesh movement algorithms, the role of the geometric conservation law, time advancement schemes, wetted surface interface strategies, and some representative applications. The complexity and computational expense of coupled Navier-Stokes/structural dynamics simulations points to the need for reduced order modeling to facilitate parametric analysis. The proper orthogonalmore » decomposition (POD)/Galerkin projection approach for building a reduced order model (ROM) is presented, along with ideas for extension of the methodology to allow construction of ROMs based on data generated from ALE simulations.« less

Computational Analysis of Arc-Jet Wedge Tests Including Ablation and Shape Change

NASA Technical Reports Server (NTRS)

Goekcen, Tahir; Chen, Yih-Kanq; Skokova, Kristina A.; Milos, Frank S.

2010-01-01

Coupled fluid-material response analyses of arc-jet wedge ablation tests conducted in a NASA Ames arc-jet facility are considered. These tests were conducted using blunt wedge models placed in a free jet downstream of the 6-inch diameter conical nozzle in the Ames 60-MW Interaction Heating Facility. The fluid analysis includes computational Navier-Stokes simulations of the nonequilibrium flowfield in the facility nozzle and test box as well as the flowfield over the models. The material response analysis includes simulation of two-dimensional surface ablation and internal heat conduction, thermal decomposition, and pyrolysis gas flow. For ablating test articles undergoing shape change, the material response and fluid analyses are coupled in order to calculate the time dependent surface heating and pressure distributions that result from shape change. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator. Effects of the test article shape change on fluid and material response simulations are demonstrated, and computational predictions of surface recession, shape change, and in-depth temperatures are compared with the experimental measurements.

Fluid-structure finite-element vibrational analysis

NASA Technical Reports Server (NTRS)

Feng, G. C.; Kiefling, L.

1974-01-01

A fluid finite element has been developed for a quasi-compressible fluid. Both kinetic and potential energy are expressed as functions of nodal displacements. Thus, the formulation is similar to that used for structural elements, with the only differences being that the fluid can possess gravitational potential, and the constitutive equations for fluid contain no shear coefficients. Using this approach, structural and fluid elements can be used interchangeably in existing efficient sparse-matrix structural computer programs such as SPAR. The theoretical development of the element formulations and the relationships of the local and global coordinates are shown. Solutions of fluid slosh, liquid compressibility, and coupled fluid-shell oscillation problems which were completed using a temporary digital computer program are shown. The frequency correlation of the solutions with classical theory is excellent.

Summary of research in applied mathematics, numerical analysis, and computer sciences

NASA Technical Reports Server (NTRS)

1986-01-01

The major categories of current ICASE research programs addressed include: numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; control and parameter identification problems, with emphasis on effective numerical methods; computational problems in engineering and physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and computer systems and software, especially vector and parallel computers.

Experimental Testing and Computational Fluid Dynamics Simulation of Maple Seeds and Performance Analysis as a Wind Turbine

NASA Astrophysics Data System (ADS)

Holden, Jacob R.

Descending maple seeds generate lift to slow their fall and remain aloft in a blowing wind; have the wings of these seeds evolved to descend as slowly as possible? A unique energy balance equation, experimental data, and computational fluid dynamics simulations have all been developed to explore this question from a turbomachinery perspective. The computational fluid dynamics in this work is the first to be performed in the relative reference frame. Maple seed performance has been analyzed for the first time based on principles of wind turbine analysis. Application of the Betz Limit and one-dimensional momentum theory allowed for empirical and computational power and thrust coefficients to be computed for maple seeds. It has been determined that the investigated species of maple seeds perform near the Betz limit for power conversion and thrust coefficient. The power coefficient for a maple seed is found to be in the range of 48-54% and the thrust coefficient in the range of 66-84%. From Betz theory, the stream tube area expansion of the maple seed is necessary for power extraction. Further investigation of computational solutions and mechanical analysis find three key reasons for high maple seed performance. First, the area expansion is driven by maple seed lift generation changing the fluid momentum and requiring area to increase. Second, radial flow along the seed surface is promoted by a sustained leading edge vortex that centrifuges low momentum fluid outward. Finally, the area expansion is also driven by the spanwise area variation of the maple seed imparting a radial force on the flow. These mechanisms result in a highly effective device for the purpose of seed dispersal. However, the maple seed also provides insight into fundamental questions about how turbines can most effectively change the momentum of moving fluids in order to extract useful power or dissipate kinetic energy.

Application of computer generated color graphic techniques to the processing and display of three dimensional fluid dynamic data

NASA Technical Reports Server (NTRS)

Anderson, B. H.; Putt, C. W.; Giamati, C. C.

1981-01-01

Color coding techniques used in the processing of remote sensing imagery were adapted and applied to the fluid dynamics problems associated with turbofan mixer nozzles. The computer generated color graphics were found to be useful in reconstructing the measured flow field from low resolution experimental data to give more physical meaning to this information and in scanning and interpreting the large volume of computer generated data from the three dimensional viscous computer code used in the analysis.

Integrating aerodynamic surface modeling for computational fluid dynamics with computer aided structural analysis, design, and manufacturing

NASA Technical Reports Server (NTRS)

Thorp, Scott A.

1992-01-01

This presentation will discuss the development of a NASA Geometry Exchange Specification for transferring aerodynamic surface geometry between LeRC systems and grid generation software used for computational fluid dynamics research. The proposed specification is based on a subset of the Initial Graphics Exchange Specification (IGES). The presentation will include discussion of how the NASA-IGES standard will accommodate improved computer aided design inspection methods and reverse engineering techniques currently being developed. The presentation is in viewgraph format.

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.

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.

Research in applied mathematics, numerical analysis, and computer science

NASA Technical Reports Server (NTRS)

1984-01-01

Research conducted at the Institute for Computer Applications in Science and Engineering (ICASE) in applied mathematics, numerical analysis, and computer science is summarized and abstracts of published reports are presented. The major categories of the ICASE research program are: (1) numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; (2) control and parameter identification; (3) computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and (4) computer systems and software, especially vector and parallel computers.

Effect of Heliox on Respiratory Outcomes during Rigid Bronchoscopy in Term Lambs.

PubMed

Sowder, Justin C; Dahl, Mar Janna; Zuspan, Kaitlin R; Albertine, Kurt H; Null, Donald M; Barneck, Mitchell D; Grimmer, J Fredrik

2018-03-01

Objective To (1) compare physiologic changes during rigid bronchoscopy during spontaneous and mechanical ventilation and (2) evaluate the efficacy of a helium-oxygen (heliox) gas mixture as compared with room air during rigid bronchoscopy. Study Design Crossover animal study evaluating physiologic parameters during rigid bronchoscopy. Outcomes were compared with predicted computational fluid analysis. Setting Simulated ventilation via computational fluid dynamics analysis and term lambs undergoing rigid bronchoscopy. Methods Respiratory and physiologic outcomes were analyzed in a lamb model simulating bronchoscopy during foreign body aspiration to compare heliox with room air. The main outcome measures were blood oxygen saturation, heart rate, blood pressure, partial pressure of oxygen, and partial pressure of carbon dioxide. Computational fluid dynamics analysis was performed with SOLIDWORKS within a rigid pediatric bronchoscope during simulated ventilation comparing heliox with room air. Results For room air, lambs desaturated within 3 minutes during mechanical ventilation versus normal oxygen saturation during spontaneous ventilation ( P = .01). No improvement in respiratory outcomes was seen between heliox and room air during mechanical ventilation. Computational fluid dynamics analysis demonstrates increased turbulence within size 3.5 bronchoscopes when comparing heliox and room air. Meaningful comparisons could not be made due to the intolerance of the lambs to heliox in vivo. Conclusion During mechanical ventilation on room air, lambs desaturate more quickly during rigid bronchoscopy on settings that should be adequate. Heliox does not improve ventilation during rigid bronchoscopy.

Inlet Development for a Rocket Based Combined Cycle, Single Stage to Orbit Vehicle Using Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

DeBonis, J. R.; Trefny, C. J.; Steffen, C. J., Jr.

1999-01-01

Design and analysis of the inlet for a rocket based combined cycle engine is discussed. Computational fluid dynamics was used in both the design and subsequent analysis. Reynolds averaged Navier-Stokes simulations were performed using both perfect gas and real gas assumptions. An inlet design that operates over the required Mach number range from 0 to 12 was produced. Performance data for cycle analysis was post processed using a stream thrust averaging technique. A detailed performance database for cycle analysis is presented. The effect ot vehicle forebody compression on air capture is also examined.

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC, year 1 quarter 3 progress report.

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

Lottes, S.A.; Kulak, R.F.; Bojanowski, C.

2011-08-26

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well-benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water loads on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to assess them for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, vehicle stability under high wind loading, and the use of electromagnetic shock absorbers to improve vehicle stability under high wind conditions. This quarterly report documents technical progress on the project tasks for the period of April through June 2011.« less

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.

Computer simulation studies in fluid and calcium regulation and orthostatic intolerance

NASA Technical Reports Server (NTRS)

1985-01-01

The systems analysis approach to physiological research uses mathematical models and computer simulation. Major areas of concern during prolonged space flight discussed include fluid and blood volume regulation; cardiovascular response during shuttle reentry; countermeasures for orthostatic intolerance; and calcium regulation and bone atrophy. Potential contributions of physiologic math models to future flight experiments are examined.

Internal air flow analysis of a bladeless micro aerial vehicle hemisphere body using computational fluid dynamic

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

Othman, M. N. K., E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Zuradzman, M. Razlan, E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Hazry, D., E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my

2014-12-04

This paper explain the analysis of internal air flow velocity of a bladeless vertical takeoff and landing (VTOL) Micro Aerial Vehicle (MAV) hemisphere body. In mechanical design, before produce a prototype model, several analyses should be done to ensure the product's effectiveness and efficiency. There are two types of analysis method can be done in mechanical design; mathematical modeling and computational fluid dynamic. In this analysis, I used computational fluid dynamic (CFD) by using SolidWorks Flow Simulation software. The idea came through to overcome the problem of ordinary quadrotor UAV which has larger size due to using four rotors andmore » the propellers are exposed to environment. The bladeless MAV body is designed to protect all electronic parts, which means it can be used in rainy condition. It also has been made to increase the thrust produced by the ducted propeller compare to exposed propeller. From the analysis result, the air flow velocity at the ducted area increased to twice the inlet air. This means that the duct contribute to the increasing of air velocity.« less

Internal air flow analysis of a bladeless micro aerial vehicle hemisphere body using computational fluid dynamic

NASA Astrophysics Data System (ADS)

Othman, M. N. K.; Zuradzman, M. Razlan; Hazry, D.; Khairunizam, Wan; Shahriman, A. B.; Yaacob, S.; Ahmed, S. Faiz; Hussain, Abadalsalam T.

2014-12-01

This paper explain the analysis of internal air flow velocity of a bladeless vertical takeoff and landing (VTOL) Micro Aerial Vehicle (MAV) hemisphere body. In mechanical design, before produce a prototype model, several analyses should be done to ensure the product's effectiveness and efficiency. There are two types of analysis method can be done in mechanical design; mathematical modeling and computational fluid dynamic. In this analysis, I used computational fluid dynamic (CFD) by using SolidWorks Flow Simulation software. The idea came through to overcome the problem of ordinary quadrotor UAV which has larger size due to using four rotors and the propellers are exposed to environment. The bladeless MAV body is designed to protect all electronic parts, which means it can be used in rainy condition. It also has been made to increase the thrust produced by the ducted propeller compare to exposed propeller. From the analysis result, the air flow velocity at the ducted area increased to twice the inlet air. This means that the duct contribute to the increasing of air velocity.

Thermal Analysis of Magnetically-Coupled Pump for Cryogenic Applications

NASA Technical Reports Server (NTRS)

Senocak, Inanc; Udaykumar, H. S.; Ndri, Narcisse; Francois, Marianne; Shyy, Wei

1999-01-01

Magnetically-coupled pump is under evaluation at Kennedy Space Center for possible cryogenic applications. A major concern is the impact of low temperature fluid flows on the pump performance. As a first step toward addressing this and related issues, a computational fluid dynamics and heat transfer tool has been adopted in a pump geometry. The computational tool includes (i) a commercial grid generator to handle multiple grid blocks and complicated geometric definitions, and (ii) an in-house computational fluid dynamics and heat transfer software developed in the Principal Investigator's group at the University of Florida. Both pure-conduction and combined convection-conduction computations have been conducted. A pure-conduction analysis gives insufficient information about the overall thermal distribution. Combined convection-conduction analysis indicates the significant influence of the coolant over the entire flow path. Since 2-D simulation is of limited help, future work on full 3-D modeling of the pump using multi-materials is needed. A comprehensive and accurate model can be developed to take into account the effect of multi-phase flow in the cooling flow loop, and the magnetic interactions.

Computation of Coupled Thermal-Fluid Problems in Distributed Memory Environment

NASA Technical Reports Server (NTRS)

Wei, H.; Shang, H. M.; Chen, Y. S.

2001-01-01

The thermal-fluid coupling problems are very important to aerospace and engineering applications. Instead of analyzing heat transfer and fluid flow separately, this study merged two well-accepted engineering solution methods, SINDA for thermal analysis and FDNS for fluid flow simulation, into a unified multi-disciplinary thermal fluid prediction method. A fully conservative patched grid interface algorithm for arbitrary two-dimensional and three-dimensional geometry has been developed. The state-of-the-art parallel computing concept was used to couple SINDA and FDNS for the communication of boundary conditions through PVM (Parallel Virtual Machine) libraries. Therefore, the thermal analysis performed by SINDA and the fluid flow calculated by FDNS are fully coupled to obtain steady state or transient solutions. The natural convection between two thick-walled eccentric tubes was calculated and the predicted results match the experiment data perfectly. A 3-D rocket engine model and a real 3-D SSME geometry were used to test the current model, and the reasonable temperature field was obtained.

The Fifth Annual Thermal and Fluids Analysis Workshop

NASA Technical Reports Server (NTRS)

1993-01-01

The Fifth Annual Thermal and Fluids Analysis Workshop was held at the Ohio Aerospace Institute, Brook Park, Ohio, cosponsored by NASA Lewis Research Center and the Ohio Aerospace Institute, 16-20 Aug. 1993. The workshop consisted of classes, vendor demonstrations, and paper sessions. The classes and vendor demonstrations provided participants with the information on widely used tools for thermal and fluid analysis. The paper sessions provided a forum for the exchange of information and ideas among thermal and fluids analysts. Paper topics included advances and uses of established thermal and fluids computer codes (such as SINDA and TRASYS) as well as unique modeling techniques and applications.

Transient thermal, hydraulic, and mechanical analysis of a counter flow offset strip fin intermediate heat exchanger using an effective porous media approach

NASA Astrophysics Data System (ADS)

Urquiza, Eugenio

This work presents a comprehensive thermal hydraulic analysis of a compact heat exchanger using offset strip fins. The thermal hydraulics analysis in this work is followed by a finite element analysis (FEA) to predict the mechanical stresses experienced by an intermediate heat exchanger (IHX) during steady-state operation and selected flow transients. In particular, the scenario analyzed involves a gas-to-liquid IHX operating between high pressure helium and liquid or molten salt. In order to estimate the stresses in compact heat exchangers a comprehensive thermal and hydraulic analysis is needed. Compact heat exchangers require very small flow channels and fins to achieve high heat transfer rates and thermal effectiveness. However, studying such small features computationally contributes little to the understanding of component level phenomena and requires prohibitive computational effort using computational fluid dynamics (CFD). To address this issue, the analysis developed here uses an effective porous media (EPM) approach; this greatly reduces the computation time and produces results with the appropriate resolution [1]. This EPM fluid dynamics and heat transfer computational code has been named the Compact Heat Exchanger Explicit Thermal and Hydraulics (CHEETAH) code. CHEETAH solves for the two-dimensional steady-state and transient temperature and flow distributions in the IHX including the complicating effects of temperature-dependent fluid thermo-physical properties. Temperature- and pressure-dependent fluid properties are evaluated by CHEETAH and the thermal effectiveness of the IHX is also calculated. Furthermore, the temperature distribution can then be imported into a finite element analysis (FEA) code for mechanical stress analysis using the EPM methods developed earlier by the University of California, Berkeley, for global and local stress analysis [2]. These simulation tools will also allow the heat exchanger design to be improved through an iterative design process which will lead to a design with a reduced pressure drop, increased thermal effectiveness, and improved mechanical performance as it relates to creep deformation and transient thermal stresses.

NASA's hypersonic fluid and thermal physics program (Aerothermodynamics)

NASA Technical Reports Server (NTRS)

Graves, R. A.; Hunt, J. L.

1985-01-01

This survey paper gives an overview of NASA's hypersonic fluid and thermal physics program (recently renamed aerothermodynamics). The purpose is to present the elements of, example results from, and rationale and projection for this program. The program is based on improving the fundamental understanding of aerodynamic and aerothermodynamic flow phenomena over hypersonic vehicles in the continuum, transitional, and rarefied flow regimes. Vehicle design capabilities, computational fluid dynamics, computational chemistry, turbulence modeling, aerothermal loads, orbiter flight data analysis, orbiter experiments, laser photodiagnostics, and facilities are discussed.

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.

Overview of MSFC's Applied Fluid Dynamics Analysis Group Activities

NASA Technical Reports Server (NTRS)

Garcia, Roberto; Wang, Tee-See; Griffin, Lisa; Turner, James E. (Technical Monitor)

2001-01-01

This document is a presentation graphic which reviews the activities of the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center (i.e., Code TD64). The work of this group focused on supporting the space transportation programs. The work of the group is in Computational Fluid Dynamic tool development. This development is driven by hardware design needs. The major applications for the design and analysis tools are: turbines, pumps, propulsion-to-airframe integration, and combustion devices.

Shuttle cryogenics supply system optimization study. Volume 5, B-3, part 2: Appendix to programmers manual for math model

NASA Technical Reports Server (NTRS)

1973-01-01

A computer programmer's manual for a digital computer which will permit rapid and accurate parametric analysis of current and advanced attitude control propulsion systems is presented. The concept is for a cold helium pressurized, subcritical cryogen fluid supplied, bipropellant gas-fed attitude control propulsion system. The cryogen fluids are stored as liquids under low pressure and temperature conditions. The mathematical model provides a generalized form for the procedural technique employed in setting up the analysis program.

SPAR improved structure/fluid dynamic analysis capability

NASA Technical Reports Server (NTRS)

Oden, J. T.; Pearson, M. L.

1983-01-01

The capability of analyzing a coupled dynamic system of flowing fluid and elastic structure was added to the SPAR computer code. A method, developed and adopted for use in SPAR utilizes the existing assumed stress hybrid plan element in SPAR. An operational mode was incorporated in SPAR which provides the capability for analyzing the flaw of a two dimensional, incompressible, viscous fluid within rigid boundaries. Equations were developed to provide for the eventual analysis of the interaction of such fluids with an elastic solid.

Development of a cryogenic mixed fluid J-T cooling computer code, 'JTMIX'

NASA Technical Reports Server (NTRS)

Jones, Jack A.

1991-01-01

An initial study was performed for analyzing and predicting the temperatures and cooling capacities when mixtures of fluids are used in Joule-Thomson coolers and in heat pipes. A computer code, JTMIX, was developed for mixed gas J-T analysis for any fluid combination of neon, nitrogen, various hydrocarbons, argon, oxygen, carbon monoxide, carbon dioxide, and hydrogen sulfide. When used in conjunction with the NIST computer code, DDMIX, it has accurately predicted order-of-magnitude increases in J-T cooling capacities when various hydrocarbons are added to nitrogen, and it predicts nitrogen normal boiling point depressions to as low as 60 K when neon is added.

On the Use of Computers for Teaching Fluid Mechanics

NASA Technical Reports Server (NTRS)

Benson, Thomas J.

1994-01-01

Several approaches for improving the teaching of basic fluid mechanics using computers are presented. There are two objectives to these approaches: to increase the involvement of the student in the learning process and to present information to the student in a variety of forms. Items discussed include: the preparation of educational videos using the results of computational fluid dynamics (CFD) calculations, the analysis of CFD flow solutions using workstation based post-processing graphics packages, and the development of workstation or personal computer based simulators which behave like desk top wind tunnels. Examples of these approaches are presented along with observations from working with undergraduate co-ops. Possible problems in the implementation of these approaches as well as solutions to these problems are also discussed.

MPI implementation of PHOENICS: A general purpose computational fluid dynamics code

NASA Astrophysics Data System (ADS)

Simunovic, S.; Zacharia, T.; Baltas, N.; Spalding, D. B.

1995-03-01

PHOENICS is a suite of computational analysis programs that are used for simulation of fluid flow, heat transfer, and dynamical reaction processes. The parallel version of the solver EARTH for the Computational Fluid Dynamics (CFD) program PHOENICS has been implemented using Message Passing Interface (MPI) standard. Implementation of MPI version of PHOENICS makes this computational tool portable to a wide range of parallel machines and enables the use of high performance computing for large scale computational simulations. MPI libraries are available on several parallel architectures making the program usable across different architectures as well as on heterogeneous computer networks. The Intel Paragon NX and MPI versions of the program have been developed and tested on massively parallel supercomputers Intel Paragon XP/S 5, XP/S 35, and Kendall Square Research, and on the multiprocessor SGI Onyx computer at Oak Ridge National Laboratory. The preliminary testing results of the developed program have shown scalable performance for reasonably sized computational domains.

MPI implementation of PHOENICS: A general purpose computational fluid dynamics code

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

Simunovic, S.; Zacharia, T.; Baltas, N.

1995-04-01

PHOENICS is a suite of computational analysis programs that are used for simulation of fluid flow, heat transfer, and dynamical reaction processes. The parallel version of the solver EARTH for the Computational Fluid Dynamics (CFD) program PHOENICS has been implemented using Message Passing Interface (MPI) standard. Implementation of MPI version of PHOENICS makes this computational tool portable to a wide range of parallel machines and enables the use of high performance computing for large scale computational simulations. MPI libraries are available on several parallel architectures making the program usable across different architectures as well as on heterogeneous computer networks. Themore » Intel Paragon NX and MPI versions of the program have been developed and tested on massively parallel supercomputers Intel Paragon XP/S 5, XP/S 35, and Kendall Square Research, and on the multiprocessor SGI Onyx computer at Oak Ridge National Laboratory. The preliminary testing results of the developed program have shown scalable performance for reasonably sized computational domains.« less

FAST: A multi-processed environment for visualization of computational fluid dynamics

NASA Technical Reports Server (NTRS)

Bancroft, Gordon V.; Merritt, Fergus J.; Plessel, Todd C.; Kelaita, Paul G.; Mccabe, R. Kevin

1991-01-01

Three-dimensional, unsteady, multi-zoned fluid dynamics simulations over full scale aircraft are typical of the problems being investigated at NASA Ames' Numerical Aerodynamic Simulation (NAS) facility on CRAY2 and CRAY-YMP supercomputers. With multiple processor workstations available in the 10-30 Mflop range, we feel that these new developments in scientific computing warrant a new approach to the design and implementation of analysis tools. These larger, more complex problems create a need for new visualization techniques not possible with the existing software or systems available as of this writing. The visualization techniques will change as the supercomputing environment, and hence the scientific methods employed, evolves even further. The Flow Analysis Software Toolkit (FAST), an implementation of a software system for fluid mechanics analysis, is discussed.

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.

Computational approaches to computational aero-acoustics

NASA Technical Reports Server (NTRS)

Hardin, Jay C.

1996-01-01

The various techniques by which the goal of computational aeroacoustics (the calculation and noise prediction of a fluctuating fluid flow) may be achieved are reviewed. The governing equations for compressible fluid flow are presented. The direct numerical simulation approach is shown to be computationally intensive for high Reynolds number viscous flows. Therefore, other approaches, such as the acoustic analogy, vortex models and various perturbation techniques that aim to break the analysis into a viscous part and an acoustic part are presented. The choice of the approach is shown to be problem dependent.

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC year 1 quarter 4 progress report.

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

Lottes, S.A.; Kulak, R.F.; Bojanowski, C.

2011-12-09

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well-benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water effects on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to assess them for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, CFD analysis of the operation of the wind tunnel in the TFCHR wind engineering laboratory, vehicle stability under high wind loading, and the use of electromagnetic shock absorbers to improve vehicle stability under high wind conditions. This quarterly report documents technical progress on the project tasks for the period of July through September 2011.« 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.

Sampling Scattered Data Onto Rectangular Grids for Volume Visualization

DTIC Science & Technology

1989-12-01

30 4.4 Building A Rectangular Grid ..... ................ 30 4.5 Sampling Methds ...... ...................... 34 4.6...dimensional data have been developed recently. In computational fluid flow analysis, methods for constructing three dimen- sional numerical grids are...structure of rectangular grids. Because finite element analysis is useful in fields other than fluid flow analysis and the numerical grid has promising

Quantitative computer tomography analysis of post-operative subdural fluid volume predicts recurrence of chronic subdural haematoma.

PubMed

Xu, Fei-Fan; Chen, Jin-Hong; Leung, Gilberto Ka Kit; Hao, Shu-Yu; Xu, Long; Hou, Zong-Gang; Mao, Xiang; Shi, Guang-Zhi; Li, Jing-Sheng; Liu, Bai-Yun

2014-01-01

Post-operative volume of subdural fluid is considered to correlate with recurrence in chronic subdural haematoma (CSDH). Information on the applications of computer-assisted volumetric analysis in patients with CSDHs is lacking. To investigate the relationship between haematoma recurrence and longitudinal changes in subdural fluid volume using CT volumetric analysis. Fifty-four patients harbouring 64 CSDHs were studied prospectively. The association between recurrence rate and CT findings were investigated. Eleven patients (20.4%) experienced post-operative recurrence. Higher pre-operative (over 120 ml) and/or pre-discharge subdural fluid volumes (over 22 ml) were significantly associated with recurrence; the probability of non-recurrence for values below these thresholds were 92.7% and 95.2%, respectively. CSDHs with larger pre-operative (over 15.1 mm) and/or residual (over 11.7 mm) widths also had significantly increased recurrence rates. Bilateral CSDHs were not found to be more likely to recur in this series. On receiver-operating characteristic curve, the areas under curve for the magnitude of changes in subdural fluid volume were greater than a single time-point measure of either width or volume of the subdural fluid cavity. Close imaging follow-up is important for CSDH patients for recurrence prediction. Using quantitative CT volumetric analysis, strong evidence was provided that changes in the residual fluid volume during the 'self-resolution' period can be used as significantly radiological predictors of recurrence.

Study of Geometric Porosity on Static Stability and Drag Using Computational Fluid Dynamics for Rigid Parachute Shapes

NASA Technical Reports Server (NTRS)

Greathouse, James S.; Schwing, Alan M.

2015-01-01

This paper explores use of computational fluid dynamics to study the e?ect of geometric porosity on static stability and drag for NASA's Multi-Purpose Crew Vehicle main parachute. Both of these aerodynamic characteristics are of interest to in parachute design, and computational methods promise designers the ability to perform detailed parametric studies and other design iterations with a level of control previously unobtainable using ground or flight testing. The approach presented here uses a canopy structural analysis code to define the inflated parachute shapes on which structured computational grids are generated. These grids are used by the computational fluid dynamics code OVERFLOW and are modeled as rigid, impermeable bodies for this analysis. Comparisons to Apollo drop test data is shown as preliminary validation of the technique. Results include several parametric sweeps through design variables in order to better understand the trade between static stability and drag. Finally, designs that maximize static stability with a minimal loss in drag are suggested for further study in subscale ground and flight testing.

Flexible Launch Vehicle Stability Analysis Using Steady and Unsteady Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Bartels, Robert E.

2012-01-01

Launch vehicles frequently experience a reduced stability margin through the transonic Mach number range. This reduced stability margin can be caused by the aerodynamic undamping 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 line loads derived from steady rigid aerodynamics. However, a quasi-steady aeroelastic stability analysis can be unconservative at the critical Mach numbers, where experiment or unsteady computational aeroelastic analysis show a reduced or even negative aerodynamic damping.Amethod of enhancing the quasi-steady aeroelastic stability analysis of a launch vehicle with unsteady aerodynamics is developed that uses unsteady computational fluid dynamics to compute the response of selected lower-frequency modes. The response is contained in a time history of the vehicle line loads. A proper orthogonal decomposition of the unsteady aerodynamic line-load 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 are compared with the damping and frequency computed from unsteady computational aeroelasticity 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 computational aeroelastic results.

Computational and Experimental Fluid-Structure Interaction Analysis of a High-Lift Wing with a Slat-Cove Filler for Noise Reduction

NASA Technical Reports Server (NTRS)

Scholten, William D.; Patterson, Ryan D.; Hartl, Darren J.; Strganac, Thomas W.; Chapelon, Quentin H. C.; Turner, Travis

2017-01-01

Airframe noise is a significant component of overall noise produced by transport aircraft during landing and approach (low speed maneuvers). A significant source for this noise is the cove of the leading-edge slat. The slat-cove filler (SCF) has been shown to be effective at mitigating slat noise. The objective of this work is to understand the fluid-structure interaction (FSI) behavior of a superelastic shape memory alloy (SMA) SCF in flow using both computational and physical models of a high-lift wing. Initial understanding of flow around the SCF and wing is obtained using computational fluid dynamics (CFD) analysis at various angles of attack. A framework compatible with an SMA constitutive model (implemented as a user material subroutine) is used to perform FSI analysis for multiple flow and configuration cases. A scaled physical model of the high-lift wing is constructed and tested in the Texas A&M 3 ft-by-4-foot wind tunnel. Initial validation of both CFD and FSI analysis is conducted by comparing lift, drag and pressure distributions with experimental results.

Segmentation of Unstructured Datasets

NASA Technical Reports Server (NTRS)

Bhat, Smitha

1996-01-01

Datasets generated by computer simulations and experiments in Computational Fluid Dynamics tend to be extremely large and complex. It is difficult to visualize these datasets using standard techniques like Volume Rendering and Ray Casting. Object Segmentation provides a technique to extract and quantify regions of interest within these massive datasets. This thesis explores basic algorithms to extract coherent amorphous regions from two-dimensional and three-dimensional scalar unstructured grids. The techniques are applied to datasets from Computational Fluid Dynamics and from Finite Element Analysis.

Computational fluid dynamic modelling of cavitation

NASA Technical Reports Server (NTRS)

Deshpande, Manish; Feng, Jinzhang; Merkle, Charles L.

1993-01-01

Models in sheet cavitation in cryogenic fluids are developed for use in Euler and Navier-Stokes codes. The models are based upon earlier potential-flow models but enable the cavity inception point, length, and shape to be determined as part of the computation. In the present paper, numerical solutions are compared with experimental measurements for both pressure distribution and cavity length. Comparisons between models are also presented. The CFD model provides a relatively simple modification to an existing code to enable cavitation performance predictions to be included. The analysis also has the added ability of incorporating thermodynamic effects of cryogenic fluids into the analysis. Extensions of the current two-dimensional steady state analysis to three-dimensions and/or time-dependent flows are, in principle, straightforward although geometrical issues become more complicated. Linearized models, however offer promise of providing effective cavitation modeling in three-dimensions. This analysis presents good potential for improved understanding of many phenomena associated with cavity flows.

High-performance parallel analysis of coupled problems for aircraft propulsion

NASA Technical Reports Server (NTRS)

Felippa, C. A.; Farhat, C.; Lanteri, S.; Maman, N.; Piperno, S.; Gumaste, U.

1994-01-01

This research program deals with the application of high-performance computing methods for the analysis of complete jet engines. We have entitled this program by applying the two dimensional parallel aeroelastic codes to the interior gas flow problem of a bypass jet engine. The fluid mesh generation, domain decomposition, and solution capabilities were successfully tested. We then focused attention on methodology for the partitioned analysis of the interaction of the gas flow with a flexible structure and with the fluid mesh motion that results from these structural displacements. This is treated by a new arbitrary Lagrangian-Eulerian (ALE) technique that models the fluid mesh motion as that of a fictitious mass-spring network. New partitioned analysis procedures to treat this coupled three-component problem are developed. These procedures involved delayed corrections and subcycling. Preliminary results on the stability, accuracy, and MPP computational efficiency are reported.

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.

A parametric analysis of waves propagating in a porous solid saturated by a three-phase fluid.

PubMed

Santos, Juan E; Savioli, Gabriela B

2015-11-01

This paper presents an analysis of a model for the propagation of waves in a poroelastic solid saturated by a three-phase viscous, compressible fluid. The constitutive relations and the equations of motion are stated first. Then a plane wave analysis determines the phase velocities and attenuation coefficients of the four compressional waves and one shear wave that propagate in this type of medium. A procedure to compute the elastic constants in the constitutive relations is defined next. Assuming the knowledge of the shear modulus of the dry matrix, the other elastic constants in the stress-strain relations are determined by employing ideal gedanken experiments generalizing those of Biot's theory for single-phase fluids. These experiments yield expressions for the elastic constants in terms of the properties of the individual solid and fluids phases. Finally the phase velocities and attenuation coefficients of all waves are computed for a sample of Berea sandstone saturated by oil, gas, and water.

Immersogeometric cardiovascular fluid–structure interaction analysis with divergence-conforming B-splines

PubMed Central

Kamensky, David; Hsu, Ming-Chen; Yu, Yue; Evans, John A.; Sacks, Michael S.; Hughes, Thomas J. R.

2016-01-01

This paper uses a divergence-conforming B-spline fluid discretization to address the long-standing issue of poor mass conservation in immersed methods for computational fluid–structure interaction (FSI) that represent the influence of the structure as a forcing term in the fluid subproblem. We focus, in particular, on the immersogeometric method developed in our earlier work, analyze its convergence for linear model problems, then apply it to FSI analysis of heart valves, using divergence-conforming B-splines to discretize the fluid subproblem. Poor mass conservation can manifest as effective leakage of fluid through thin solid barriers. This leakage disrupts the qualitative behavior of FSI systems such as heart valves, which exist specifically to block flow. Divergence-conforming discretizations can enforce mass conservation exactly, avoiding this problem. To demonstrate the practical utility of immersogeometric FSI analysis with divergence-conforming B-splines, we use the methods described in this paper to construct and evaluate a computational model of an in vitro experiment that pumps water through an artificial valve. PMID:28239201

Aeroelastic analysis of bridge girder section using computer modeling

DOT National Transportation Integrated Search

2001-05-01

This report describes the numerical simulation of wind flow around bridges using the Finite Element Method (FEM) and the principles of Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD). Since, the suspension bridges are p...

Ongoing Analysis of Rocket Based Combined Cycle Engines by the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Ruf, Joseph; Holt, James B.; Canabal, Francisco

1999-01-01

This paper presents the status of analyses on three Rocket Based Combined Cycle configurations underway in the Applied Fluid Dynamics Analysis Group (TD64). TD64 is performing computational fluid dynamics analysis on a Penn State RBCC test rig, the proposed Draco axisymmetric RBCC engine and the Trailblazer engine. The intent of the analysis on the Penn State test rig is to benchmark the Finite Difference Navier Stokes code for ejector mode fluid dynamics. The Draco engine analysis is a trade study to determine the ejector mode performance as a function of three engine design variables. The Trailblazer analysis is to evaluate the nozzle performance in scramjet mode. Results to date of each analysis are presented.

Computational fluid dynamics for propulsion technology: Geometric grid visualization in CFD-based propulsion technology research

NASA Technical Reports Server (NTRS)

Ziebarth, John P.; Meyer, Doug

1992-01-01

The coordination is examined of necessary resources, facilities, and special personnel to provide technical integration activities in the area of computational fluid dynamics applied to propulsion technology. Involved is the coordination of CFD activities between government, industry, and universities. Current geometry modeling, grid generation, and graphical methods are established to use in the analysis of CFD design methodologies.

TEMPEST: A computer code for three-dimensional analysis of transient fluid dynamics

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

Fort, J.A.

TEMPEST (Transient Energy Momentum and Pressure Equations Solutions in Three dimensions) is a powerful tool for solving engineering problems in nuclear energy, waste processing, chemical processing, and environmental restoration because it analyzes and illustrates 3-D time-dependent computational fluid dynamics and heat transfer analysis. It is a family of codes with two primary versions, a N- Version (available to public) and a T-Version (not currently available to public). This handout discusses its capabilities, applications, numerical algorithms, development status, and availability and assistance.

STARS: An Integrated, Multidisciplinary, Finite-Element, Structural, Fluids, Aeroelastic, and Aeroservoelastic Analysis Computer Program

NASA Technical Reports Server (NTRS)

Gupta, K. K.

1997-01-01

A multidisciplinary, finite element-based, highly graphics-oriented, linear and nonlinear analysis capability that includes such disciplines as structures, heat transfer, linear aerodynamics, computational fluid dynamics, and controls engineering has been achieved by integrating several new modules in the original STARS (STructural Analysis RoutineS) computer program. Each individual analysis module is general-purpose in nature and is effectively integrated to yield aeroelastic and aeroservoelastic solutions of complex engineering problems. Examples of advanced NASA Dryden Flight Research Center projects analyzed by the code in recent years include the X-29A, F-18 High Alpha Research Vehicle/Thrust Vectoring Control System, B-52/Pegasus Generic Hypersonics, National AeroSpace Plane (NASP), SR-71/Hypersonic Launch Vehicle, and High Speed Civil Transport (HSCT) projects. Extensive graphics capabilities exist for convenient model development and postprocessing of analysis results. The program is written in modular form in standard FORTRAN language to run on a variety of computers, such as the IBM RISC/6000, SGI, DEC, Cray, and personal computer; associated graphics codes use OpenGL and IBM/graPHIGS language for color depiction. This program is available from COSMIC, the NASA agency for distribution of computer programs.

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.

FAST - A multiprocessed environment for visualization of computational fluid dynamics

NASA Technical Reports Server (NTRS)

Bancroft, Gordon V.; Merritt, Fergus J.; Plessel, Todd C.; Kelaita, Paul G.; Mccabe, R. Kevin

1991-01-01

The paper presents the Flow Analysis Software Toolset (FAST) to be used for fluid-mechanics analysis. The design criteria for FAST including the minimization of the data path in the computational fluid-dynamics (CFD) process, consistent user interface, extensible software architecture, modularization, and the isolation of three-dimensional tasks from the application programmer are outlined. Each separate process communicates through the FAST Hub, while other modules such as FAST Central, NAS file input, CFD calculator, surface extractor and renderer, titler, tracer, and isolev might work together to generate the scene. An interprocess communication package making it possible for FAST to operate as a modular environment where resources could be shared among different machines as well as a single host is discussed.

Ongoing Analyses of Rocket Based Combined Cycle Engines by the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Ruf, Joseph H.; Holt, James B.; Canabal, Francisco

2001-01-01

This paper presents the status of analyses on three Rocket Based Combined Cycle (RBCC) configurations underway in the Applied Fluid Dynamics Analysis Group (TD64). TD64 is performing computational fluid dynamics (CFD) analysis on a Penn State RBCC test rig, the proposed Draco axisymmetric RBCC engine and the Trailblazer engine. The intent of the analysis on the Penn State test rig is to benchmark the Finite Difference Navier Stokes (FDNS) code for ejector mode fluid dynamics. The Draco analysis was a trade study to determine the ejector mode performance as a function of three engine design variables. The Trailblazer analysis is to evaluate the nozzle performance in scramjet mode. Results to date of each analysis are presented.

Fluid Centrality: A Social Network Analysis of Social-Technical Relations in Computer-Mediated Communication

ERIC Educational Resources Information Center

Enriquez, Judith Guevarra

2010-01-01

In this article, centrality is explored as a measure of computer-mediated communication (CMC) in networked learning. Centrality measure is quite common in performing social network analysis (SNA) and in analysing social cohesion, strength of ties and influence in CMC, and computer-supported collaborative learning research. It argues that measuring…

The numerical dynamic for highly nonlinear partial differential equations

NASA Technical Reports Server (NTRS)

Lafon, A.; Yee, H. C.

1992-01-01

Problems associated with the numerical computation of highly nonlinear equations in computational fluid dynamics are set forth and analyzed in terms of the potential ranges of spurious behaviors. A reaction-convection equation with a nonlinear source term is employed to evaluate the effects related to spatial and temporal discretizations. The discretization of the source term is described according to several methods, and the various techniques are shown to have a significant effect on the stability of the spurious solutions. Traditional linearized stability analyses cannot provide the level of confidence required for accurate fluid dynamics computations, and the incorporation of nonlinear analysis is proposed. Nonlinear analysis based on nonlinear dynamical systems complements the conventional linear approach and is valuable in the analysis of hypersonic aerodynamics and combustion phenomena.

Modelling low Reynolds number vortex-induced vibration problems with a fixed mesh fluid-solid interaction formulation

NASA Astrophysics Data System (ADS)

González Cornejo, Felipe A.; Cruchaga, Marcela A.; Celentano, Diego J.

2017-11-01

The present work reports a fluid-rigid solid interaction formulation described within the framework of a fixed-mesh technique. The numerical analysis is focussed on the study of a vortex-induced vibration (VIV) of a circular cylinder at low Reynolds number. The proposed numerical scheme encompasses the fluid dynamics computation in an Eulerian domain where the body is embedded using a collection of markers to describe its shape, and the rigid solid's motion is obtained with the well-known Newton's law. The body's velocity is imposed on the fluid domain through a penalty technique on the embedded fluid-solid interface. The fluid tractions acting on the solid are computed from the fluid dynamic solution of the flow around the body. The resulting forces are considered to solve the solid motion. The numerical code is validated by contrasting the obtained results with those reported in the literature using different approaches for simulating the flow past a fixed circular cylinder as a benchmark problem. Moreover, a mesh convergence analysis is also done providing a satisfactory response. In particular, a VIV problem is analyzed, emphasizing the description of the synchronization phenomenon.

Magic angle spinning NMR below 6 K with a computational fluid dynamics analysis of fluid flow and temperature gradients

NASA Astrophysics Data System (ADS)

Sesti, Erika L.; Alaniva, Nicholas; Rand, Peter W.; Choi, Eric J.; Albert, Brice J.; Saliba, Edward P.; Scott, Faith J.; Barnes, Alexander B.

2018-01-01

We report magic angle spinning (MAS) up to 8.5 kHz with a sample temperature below 6 K using liquid helium as a variable temperature fluid. Cross polarization 13C NMR spectra exhibit exquisite sensitivity with a single transient. Remarkably, 1H saturation recovery experiments show a 1H T1 of 21 s with MAS below 6 K in the presence of trityl radicals in a glassy matrix. Leveraging the thermal spin polarization available at 4.2 K versus 298 K should result in 71 times higher signal intensity. Taking the 1H longitudinal relaxation into account, signal averaging times are therefore predicted to be expedited by a factor of >500. Computer assisted design (CAD) and finite element analysis were employed in both the design and diagnostic stages of this cryogenic MAS technology development. Computational fluid dynamics (CFD) models describing temperature gradients and fluid flow are presented. The CFD models bearing and drive gas maintained at 100 K, while a colder helium variable temperature fluid stream cools the center of a zirconia rotor. Results from the CFD were used to optimize the helium exhaust path and determine the sample temperature. This novel cryogenic experimental platform will be integrated with pulsed dynamic nuclear polarization and electron decoupling to interrogate biomolecular structure within intact human cells.

Modular thermal analyzer routine, volume 1

NASA Technical Reports Server (NTRS)

Oren, J. A.; Phillips, M. A.; Williams, D. R.

1972-01-01

The Modular Thermal Analyzer Routine (MOTAR) is a general thermal analysis routine with strong capabilities for performing thermal analysis of systems containing flowing fluids, fluid system controls (valves, heat exchangers, etc.), life support systems, and thermal radiation situations. Its modular organization permits the analysis of a very wide range of thermal problems for simple problems containing a few conduction nodes to those containing complicated flow and radiation analysis with each problem type being analyzed with peak computational efficiency and maximum ease of use. The organization and programming methods applied to MOTAR achieved a high degree of computer utilization efficiency in terms of computer execution time and storage space required for a given problem. The computer time required to perform a given problem on MOTAR is approximately 40 to 50 percent that required for the currently existing widely used routines. The computer storage requirement for MOTAR is approximately 25 percent more than the most commonly used routines for the most simple problems but the data storage techniques for the more complicated options should save a considerable amount of space.

An Integrated Solution for Performing Thermo-fluid Conjugate Analysis

NASA Technical Reports Server (NTRS)

Kornberg, Oren

2009-01-01

A method has been developed which integrates a fluid flow analyzer and a thermal analyzer to produce both steady state and transient results of 1-D, 2-D, and 3-D analysis models. The Generalized Fluid System Simulation Program (GFSSP) is a one dimensional, general purpose fluid analysis code which computes pressures and flow distributions in complex fluid networks. The MSC Systems Improved Numerical Differencing Analyzer (MSC.SINDA) is a one dimensional general purpose thermal analyzer that solves network representations of thermal systems. Both GFSSP and MSC.SINDA have graphical user interfaces which are used to build the respective model and prepare it for analysis. The SINDA/GFSSP Conjugate Integrator (SGCI) is a formbase graphical integration program used to set input parameters for the conjugate analyses and run the models. The contents of this paper describes SGCI and its thermo-fluids conjugate analysis techniques and capabilities by presenting results from some example models including the cryogenic chill down of a copper pipe, a bar between two walls in a fluid stream, and a solid plate creating a phase change in a flowing fluid.

Lattice Boltzmann computation of creeping fluid flow in roll-coating applications

NASA Astrophysics Data System (ADS)

Rajan, Isac; Kesana, Balashanker; Perumal, D. Arumuga

2018-04-01

Lattice Boltzmann Method (LBM) has advanced as a class of Computational Fluid Dynamics (CFD) methods used to solve complex fluid systems and heat transfer problems. It has ever-increasingly attracted the interest of researchers in computational physics to solve challenging problems of industrial and academic importance. In this current study, LBM is applied to simulate the creeping fluid flow phenomena commonly encountered in manufacturing technologies. In particular, we apply this novel method to simulate the fluid flow phenomena associated with the "meniscus roll coating" application. This prevalent industrial problem encountered in polymer processing and thin film coating applications is modelled as standard lid-driven cavity problem to which creeping flow analysis is applied. This incompressible viscous flow problem is studied in various speed ratios, the ratio of upper to lower lid speed in two different configurations of lid movement - parallel and anti-parallel wall motion. The flow exhibits interesting patterns which will help in design of roll coaters.

Comparison of competing segmentation standards for X-ray computed topographic imaging using Lattice Boltzmann techniques

NASA Astrophysics Data System (ADS)

Larsen, J. D.; Schaap, M. G.

2013-12-01

Recent advances in computing technology and experimental techniques have made it possible to observe and characterize fluid dynamics at the micro-scale. Many computational methods exist that can adequately simulate fluid flow in porous media. Lattice Boltzmann methods provide the distinct advantage of tracking particles at the microscopic level and returning macroscopic observations. While experimental methods can accurately measure macroscopic fluid dynamics, computational efforts can be used to predict and gain insight into fluid dynamics by utilizing thin sections or computed micro-tomography (CMT) images of core sections. Although substantial effort have been made to advance non-invasive imaging methods such as CMT, fluid dynamics simulations, and microscale analysis, a true three dimensional image segmentation technique has not been developed until recently. Many competing segmentation techniques are utilized in industry and research settings with varying results. In this study lattice Boltzmann method is used to simulate stokes flow in a macroporous soil column. Two dimensional CMT images were used to reconstruct a three dimensional representation of the original sample. Six competing segmentation standards were used to binarize the CMT volumes which provide distinction between solid phase and pore space. The permeability of the reconstructed samples was calculated, with Darcy's Law, from lattice Boltzmann simulations of fluid flow in the samples. We compare simulated permeability from differing segmentation algorithms to experimental findings.

A non-oscillatory energy-splitting method for the computation of compressible multi-fluid flows

NASA Astrophysics Data System (ADS)

Lei, Xin; Li, Jiequan

2018-04-01

This paper proposes a new non-oscillatory energy-splitting conservative algorithm for computing multi-fluid flows in the Eulerian framework. In comparison with existing multi-fluid algorithms in the literature, it is shown that the mass fraction model with isobaric hypothesis is a plausible choice for designing numerical methods for multi-fluid flows. Then we construct a conservative Godunov-based scheme with the high order accurate extension by using the generalized Riemann problem solver, through the detailed analysis of kinetic energy exchange when fluids are mixed under the hypothesis of isobaric equilibrium. Numerical experiments are carried out for the shock-interface interaction and shock-bubble interaction problems, which display the excellent performance of this type of schemes and demonstrate that nonphysical oscillations are suppressed around material interfaces substantially.

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

NASA Technical Reports Server (NTRS)

Li, Wu; Shields, Elwood; Geiselhart, Karl

2011-01-01

This paper documents a mixed-fidelity approach for the design of low-boom supersonic aircraft with a focus on fuselage shaping.A low-boom configuration that is based on low-fidelity analysis is used as the baseline. The fuselage shape is modified iteratively to obtain a configuration with an equivalent-area distribution derived from computational fluid dynamics analysis that attempts to match a predetermined low-boom target area distribution and also yields a low-boom ground signature. The ground signature of the final configuration is calculated by using a state-of-the-art computational-fluid-dynamics-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 computational fluid dynamics equivalent-area distribution. This result supports the validity of 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.

Computational Fluid Dynamic Simulation of Flow in Abrasive Water Jet Machining

NASA Astrophysics Data System (ADS)

Venugopal, S.; Sathish, S.; Jothi Prakash, V. M.; Gopalakrishnan, T.

2017-03-01

Abrasive water jet cutting is one of the most recently developed non-traditional manufacturing technologies. In this machining, the abrasives are mixed with suspended liquid to form semi liquid mixture. The general nature of flow through the machining, results in fleeting wear of the nozzle which decrease the cutting performance. The inlet pressure of the abrasive water suspension has main effect on the major destruction characteristics of the inner surface of the nozzle. The aim of the project is to analyze the effect of inlet pressure on wall shear and exit kinetic energy. The analysis could be carried out by changing the taper angle of the nozzle, so as to obtain optimized process parameters for minimum nozzle wear. The two phase flow analysis would be carried by using computational fluid dynamics tool CFX. It is also used to analyze the flow characteristics of abrasive water jet machining on the inner surface of the nozzle. The availability of optimized process parameters of abrasive water jet machining (AWJM) is limited to water and experimental test can be cost prohibitive. In this case, Computational fluid dynamics analysis would provide better results.

Digital analysis of wind tunnel imagery to measure fluid thickness

NASA Technical Reports Server (NTRS)

Easton, Roger L., Jr.; Enge, James

1992-01-01

Documented here are the procedure and results obtained from the application of digital image processing techniques to the problem of measuring the thickness of a deicing fluid on a model airfoil during simulated takeoffs. The fluid contained a fluorescent dye and the images were recorded under flash illumination on photographic film. The films were digitized and analyzed on a personal computer to obtain maps of the fluid thickness.

Calculating far-field radiated sound pressure levels from NASTRAN output

NASA Technical Reports Server (NTRS)

Lipman, R. R.

1986-01-01

FAFRAP is a computer program which calculates far field radiated sound pressure levels from quantities computed by a NASTRAN direct frequency response analysis of an arbitrarily shaped structure. Fluid loading on the structure can be computed directly by NASTRAN or an added-mass approximation to fluid loading on the structure can be used. Output from FAFRAP includes tables of radiated sound pressure levels and several types of graphic output. FAFRAP results for monopole and dipole sources compare closely with an explicit calculation of the radiated sound pressure level for those sources.

A Novel Shape Parameterization Approach

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.

1999-01-01

This paper presents a novel parameterization approach for complex shapes suitable for a multidisciplinary design optimization application. The approach consists of two basic concepts: (1) parameterizing the shape perturbations rather than the geometry itself and (2) performing the shape deformation by means of the soft objects animation algorithms used in computer graphics. Because the formulation presented in this paper is independent of grid topology, we can treat computational fluid dynamics and finite element grids in a similar manner. The proposed approach is simple, compact, and efficient. Also, the analytical sensitivity derivatives are easily computed for use in a gradient-based optimization. This algorithm is suitable for low-fidelity (e.g., linear aerodynamics and equivalent laminated plate structures) and high-fidelity analysis tools (e.g., nonlinear computational fluid dynamics and detailed finite element modeling). This paper contains the implementation details of parameterizing for planform, twist, dihedral, thickness, and camber. The results are presented for a multidisciplinary design optimization application consisting of nonlinear computational fluid dynamics, detailed computational structural mechanics, performance, and a simple propulsion module.

Multidisciplinary Aerodynamic-Structural Shape Optimization Using Deformation (MASSOUD)

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.

2000-01-01

This paper presents a multidisciplinary shape parameterization approach. The approach consists of two basic concepts: (1) parameterizing the shape perturbations rather than the geometry itself and (2) performing the shape deformation by means of the soft object animation algorithms used in computer graphics. Because the formulation presented in this paper is independent of grid topology, we can treat computational fluid dynamics and finite element grids in the same manner. The proposed approach is simple, compact, and efficient. Also, the analytical sensitivity derivatives are easily computed for use in a gradient-based optimization. This algorithm is suitable for low-fidelity (e.g., linear aerodynamics and equivalent laminate plate structures) and high-fidelity (e.g., nonlinear computational fluid dynamics and detailed finite element modeling) analysis tools. This paper contains the implementation details of parameterizing for planform, twist, dihedral, thickness, camber, and free-form surface. Results are presented for a multidisciplinary application consisting of nonlinear computational fluid dynamics, detailed computational structural mechanics, and a simple performance module.

Multidisciplinary Aerodynamic-Structural Shape Optimization Using Deformation (MASSOUD)

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.

2000-01-01

This paper presents a multidisciplinary shape parameterization approach. The approach consists of two basic concepts: (1) parameterizing the shape perturbations rather than the geometry itself and (2) performing the shape deformation by means of the soft object animation algorithms used in computer graphics. Because the formulation presented in this paper is independent of grid topology, we can treat computational fluid dynamics and finite element grids in a similar manner. The proposed approach is simple, compact, and efficient. Also, the analytical sensitivity derivatives are easily computed for use in a gradient-based optimization. This algorithm is suitable for low-fidelity (e.g., linear aerodynamics and equivalent laminated plate structures) and high-fidelity (e.g., nonlinear computational fluid dynamics and detailed finite element modeling analysis tools. This paper contains the implementation details of parameterizing for planform, twist, dihedral, thickness, camber, and free-form surface. Results are presented for a multidisciplinary design optimization application consisting of nonlinear computational fluid dynamics, detailed computational structural mechanics, and a simple performance module.

Convection equation modeling: A non-iterative direct matrix solution algorithm for use with SINDA

NASA Technical Reports Server (NTRS)

Schrage, Dean S.

1993-01-01

The determination of the boundary conditions for a component-level analysis, applying discrete finite element and finite difference modeling techniques often requires an analysis of complex coupled phenomenon that cannot be described algebraically. For example, an analysis of the temperature field of a coldplate surface with an integral fluid loop requires a solution to the parabolic heat equation and also requires the boundary conditions that describe the local fluid temperature. However, the local fluid temperature is described by a convection equation that can only be solved with the knowledge of the locally-coupled coldplate temperatures. Generally speaking, it is not computationally efficient, and sometimes, not even possible to perform a direct, coupled phenomenon analysis of the component-level and boundary condition models within a single analysis code. An alternative is to perform a disjoint analysis, but transmit the necessary information between models during the simulation to provide an indirect coupling. For this approach to be effective, the component-level model retains full detail while the boundary condition model is simplified to provide a fast, first-order prediction of the phenomenon in question. Specifically for the present study, the coldplate structure is analyzed with a discrete, numerical model (SINDA) while the fluid loop convection equation is analyzed with a discrete, analytical model (direct matrix solution). This indirect coupling allows a satisfactory prediction of the boundary condition, while not subjugating the overall computational efficiency of the component-level analysis. In the present study a discussion of the complete analysis of the derivation and direct matrix solution algorithm of the convection equation is presented. Discretization is analyzed and discussed to extend of solution accuracy, stability and computation speed. Case studies considering a pulsed and harmonic inlet disturbance to the fluid loop are analyzed to assist in the discussion of numerical dissipation and accuracy. In addition, the issues of code melding or integration with standard class solvers such as SINDA are discussed to advise the user of the potential problems to be encountered.

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.

Heat pipe radiators for space

NASA Technical Reports Server (NTRS)

Sellers, J. P.

1976-01-01

Analysis of the data heat pipe radiator systems tested in both vacuum and ambient environments was continued. The systems included (1) a feasibility VCHP header heat-pipe panel, (2) the same panel reworked to eliminate the VCHP feature and referred to as the feasibility fluid header panel, and (3) an optimized flight-weight fluid header panel termed the 'prototype.' A description of freeze-thaw thermal vacuum tests conducted on the feasibility VCHP was included. In addition, the results of ambient tests made on the feasibility fluid header are presented, including a comparison with analytical results. A thermal model of a fluid header heat pipe radiator was constructed and a computer program written. The program was used to make a comparison of the VCHP and fluid-header concepts for both single and multiple panel applications. The computer program was also employed for a parametric study, including optimum feeder heat pipe spacing, of the prototype fluid header.

Fluid/Structure Interaction Studies of Aircraft Using High Fidelity Equations on Parallel Computers

NASA Technical Reports Server (NTRS)

Guruswamy, Guru; VanDalsem, William (Technical Monitor)

1994-01-01

Abstract Aeroelasticity which involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of modern aircraft such as High Speed Civil Transport (HSCT) and Advanced Subsonic Transport (AST) which can experience complex flow/structure interactions. HSCT can experience vortex induced aeroelastic oscillations whereas AST can experience transonic buffet associated structural oscillations. Both aircraft may experience a dip in the flutter speed at the transonic regime. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Computations using these high fidelity equations require large computational resources both in memory and speed. Current conventional super computers have reached their limitations both in memory and speed. As a result, parallel computers have evolved to overcome the limitations of conventional computers. This paper will address the transition that is taking place in computational aeroelasticity from conventional computers to parallel computers. The paper will address special techniques needed to take advantage of the architecture of new parallel computers. Results will be illustrated from computations made on iPSC/860 and IBM SP2 computer by using ENSAERO code that directly couples the Euler/Navier-Stokes flow equations with high resolution finite-element structural equations.

Thermal and fluid-dynamics behavior of circulating systems in the case of pressure relief

NASA Astrophysics Data System (ADS)

Moeller, L.

Aspects of safety in the case of large-scale installations with operational high-pressure conditions must be an important consideration already during the design of such installations, taking into account all conceivable disturbances. Within an analysis of such disturbances, studies related to pressure relief processes will have to occupy a central position. For such studies, it is convenient to combine experiments involving small-scale models of the actual installation with suitable computational programs. The experiments can be carried out at lower pressures and temperatures if the actual fluid is replaced by another medium, such as, for instance, a refrigerant. This approach has been used in the present investigation. The obtained experimental data are employed as a basis for a verification of the results provided by the computational model 'Frelap-UK' which has been expressly developed for the analysis of system behavior in the case of pressure relief. It is found that the computer fluid-dynamics characteristics agree with the experimental results.

Thermal Hydraulics Design and Analysis Methodology for a Solid-Core Nuclear Thermal Rocket Engine Thrust Chamber

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Canabal, Francisco; Chen, Yen-Sen; Cheng, Gary; Ito, Yasushi

2013-01-01

Nuclear thermal propulsion is a leading candidate for in-space propulsion for human Mars missions. This chapter describes a thermal hydraulics design and analysis methodology developed at the NASA Marshall Space Flight Center, in support of the nuclear thermal propulsion development effort. The objective of this campaign is to bridge the design methods in the Rover/NERVA era, with a modern computational fluid dynamics and heat transfer methodology, to predict thermal, fluid, and hydrogen environments of a hypothetical solid-core, nuclear thermal engine the Small Engine, designed in the 1960s. The computational methodology is based on an unstructured-grid, pressure-based, all speeds, chemically reacting, computational fluid dynamics and heat transfer platform, while formulations of flow and heat transfer through porous and solid media were implemented to describe those of hydrogen flow channels inside the solid24 core. Design analyses of a single flow element and the entire solid-core thrust chamber of the Small Engine were performed and the results are presented herein

Computational investigation of fluid flow and heat transfer of an economizer by porous medium approach

NASA Astrophysics Data System (ADS)

Babu, C. Rajesh; Kumar, P.; Rajamohan, G.

2017-07-01

Computation of fluid flow and heat transfer in an economizer is simulated by a porous medium approach, with plain tubes having a horizontal in-line arrangement and cross flow arrangement in a coal-fired thermal power plant. The economizer is a thermal mechanical device that captures waste heat from the thermal exhaust flue gasses through heat transfer surfaces to preheat boiler feed water. In order to evaluate the fluid flow and heat transfer on tubes, a numerical analysis on heat transfer performance is carried out on an 110 t/h MCR (Maximum continuous rating) boiler unit. In this study, thermal performance is investigated using the computational fluid dynamics (CFD) simulation using ANSYS FLUENT. The fouling factor ε and the overall heat transfer coefficient ψ are employed to evaluate the fluid flow and heat transfer. The model demands significant computational details for geometric modeling, grid generation, and numerical calculations to evaluate the thermal performance of an economizer. The simulation results show that the overall heat transfer coefficient 37.76 W/(m2K) and economizer coil side pressure drop of 0.2 (kg/cm2) are found to be conformity within the tolerable limits when compared with existing industrial economizer data.

Semiannual report, 1 April - 30 September 1991

NASA Technical Reports Server (NTRS)

1991-01-01

The major categories of the current Institute for Computer Applications in Science and Engineering (ICASE) research program are: (1) numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; (2) control and parameter identification problems, with emphasis on effective numerical methods; (3) computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and (4) computer systems and software for parallel computers. Research in these areas is discussed.

Stability of mixed time integration schemes for transient thermal analysis

NASA Technical Reports Server (NTRS)

Liu, W. K.; Lin, J. I.

1982-01-01

A current research topic in coupled-field problems is the development of effective transient algorithms that permit different time integration methods with different time steps to be used simultaneously in various regions of the problems. The implicit-explicit approach seems to be very successful in structural, fluid, and fluid-structure problems. This paper summarizes this research direction. A family of mixed time integration schemes, with the capabilities mentioned above, is also introduced for transient thermal analysis. A stability analysis and the computer implementation of this technique are also presented. In particular, it is shown that the mixed time implicit-explicit methods provide a natural framework for the further development of efficient, clean, modularized computer codes.

Simplified dynamic analysis to evaluate liquefaction-induced lateral deformation of earth slopes: a computational fluid dynamics approach

NASA Astrophysics Data System (ADS)

Jafarian, Yaser; Ghorbani, Ali; Ahmadi, Omid

2014-09-01

Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied soil is considered as viscous fluid. In this manner, the liquefied soil behaves as non-Newtonian fluid, whose viscosity decreases as the shear strain rate increases. The current study incorporates computational fluid dynamics to propose a simplified dynamic analysis for the liquefaction-induced lateral deformation of earth slopes. The numerical procedure involves a quasi-linear elastic model for small to moderate strains and a Bingham fluid model for large strain states during liquefaction. An iterative procedure is considered to estimate the strain-compatible shear stiffness of soil. The post-liquefaction residual strength of soil is considered as the initial Bingham viscosity. Performance of the numerical procedure is examined by using the results of centrifuge model and shaking table tests together with some field observations of lateral ground deformation. The results demonstrate that the proposed procedure predicts the time history of lateral ground deformation with a reasonable degree of precision.

Deformation and Breakup of Two Fluid Jets

NASA Astrophysics Data System (ADS)

Doshi, Pankaj; Ramkrishna, Doraiswamy; Basaran, Osman

2001-11-01

Two fluid jets consists of an inner liquid core surrounded by an annulus of outer immiscible liquid. The perturbation in the inner and outer interphase could cause capillary instability resulting in large deformation and breakup of the jet into drops. The jet breakup and drop size distribution is largely influenced by the properties of inner and outer fluid phases. Out of the various jet breakup phenomena one with most technological importance is the one in which inner interphase ruptures followed by the outer interphase resulting in the formation of compound drops. The compound drop formation is very useful for the microencapsulation technology, which find use in diverse pharmaceutical and chemical industry applications. In this paper we present a computational analysis of non-linear deformation and breakup of two fluid jets of Newtonian fluids. The analysis involves study of capillary instability driven deformation of a free jet with periodic boundary conditions. Although small amplitude deformation of two fluid jets have previously been studied, large amplitude deformation exhibiting interesting nonlinear dynamics and eventual breakup of the two fluid jets have been beyond the reach of previously used analytical and computational techniques. The computational difficulties result from the facts that (1) the inner and outer interphase can overturn during the motion and (2) pressure and normal stress are discontinuous at the inner interphase. We overcome both of these difficulties by using a new Galerkin/finite element algorithm that relies on a powerful elliptic mesh generation technique. The results to be presented includes jet deformation and breakup time as a function of inner and outer fluid phase properties. The highlight of the results will be prediction of drop size distribution which is of critical importance for microencapsulation technology.

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.

Giant intracranial aneurysm embolization with a yield stress fluid material: insights from CFD analysis.

PubMed

Wang, Weixiong; Graziano, Francesca; Russo, Vittorio; Ulm, Arthur J; De Kee, Daniel; Khismatullin, Damir B

2013-01-01

The endovascular treatment of intracranial aneurysms remains a challenge, especially when the aneurysm is large in size and has irregular, non-spherical geometry. In this paper, we use computational fluid dynamics to simulate blood flow in a vertebro-basilar junction giant aneurysm for the following three cases: (1) an empty aneurysm, (2) an aneurysm filled with platinum coils, and (3) an aneurysm filled with a yield stress fluid material. In the computational model, blood and the coil-filled region are treated as a non-Newtonian fluid and an isotropic porous medium, respectively. The results show that yield stress fluids can be used for aneurysm embolization provided the yield stress value is 20 Pa or higher. Specifically, flow recirculation in the aneurysm and the size of the inflow jet impingement zone on the aneurysm wall are substantially reduced by yield stress fluid treatment. Overall, this study opens up the possibility of using yield stress fluids for effective embolization of large-volume intracranial aneurysms.

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.

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.

Aerodynamic design optimization using sensitivity analysis and computational fluid dynamics

NASA Technical Reports Server (NTRS)

Baysal, Oktay; Eleshaky, Mohamed E.

1991-01-01

A new and efficient method is presented for aerodynamic design optimization, which is based on a computational fluid dynamics (CFD)-sensitivity analysis algorithm. The method is applied to design a scramjet-afterbody configuration for an optimized axial thrust. The Euler equations are solved for the inviscid analysis of the flow, which in turn provides the objective function and the constraints. The CFD analysis is then coupled with the optimization procedure that uses a constrained minimization method. The sensitivity coefficients, i.e. gradients of the objective function and the constraints, needed for the optimization are obtained using a quasi-analytical method rather than the traditional brute force method of finite difference approximations. During the one-dimensional search of the optimization procedure, an approximate flow analysis (predicted flow) based on a first-order Taylor series expansion is used to reduce the computational cost. Finally, the sensitivity of the optimum objective function to various design parameters, which are kept constant during the optimization, is computed to predict new optimum solutions. The flow analysis of the demonstrative example are compared with the experimental data. It is shown that the method is more efficient than the traditional methods.

TAP 2: A finite element program for thermal analysis of convectively cooled structures

NASA Technical Reports Server (NTRS)

Thornton, E. A.

1980-01-01

A finite element computer program (TAP 2) for steady-state and transient thermal analyses of convectively cooled structures is presented. The program has a finite element library of six elements: two conduction/convection elements to model heat transfer in a solid, two convection elements to model heat transfer in a fluid, and two integrated conduction/convection elements to represent combined heat transfer in tubular and plate/fin fluid passages. Nonlinear thermal analysis due to temperature-dependent thermal parameters is performed using the Newton-Raphson iteration method. Transient analyses are performed using an implicit Crank-Nicolson time integration scheme with consistent or lumped capacitance matrices as an option. Program output includes nodal temperatures and element heat fluxes. Pressure drops in fluid passages may be computed as an option. User instructions and sample problems are presented in appendixes.

Trash Diverter Orientation Angle Optimization at Run-Off River Type Hydro-power Plant using CFD

NASA Astrophysics Data System (ADS)

Munisamy, Kannan M.; Kamal, Ahmad; Shuaib, Norshah Hafeez; Yusoff, Mohd. Zamri; Hasini, Hasril; Rashid, Azri Zainol; Thangaraju, Savithry K.; Hamid, Hazha

2010-06-01

Tenom Pangi Hydro Power Station in Tenom, Sabah is suffering from poor river quality with a lot of suspended trashes. This problem necessitates the need for a trash diverter to divert the trash away from the intake region. Previously, a trash diverter (called Trash Diverter I) was installed at the site but managed to survived for a short period of time due to an impact with huge log as a results of a heavy flood. In the current project, a second trash diverter structure is designed (called Trash Diverter II) with improved features compared to Trash Diverter I. The Computational Fluid Dynamics (CFD) analysis is done to evaluate the river flow interaction onto the trash diverter from the fluid flow point of view, Computational Fluids Dynamics is a numerical approach to solve fluid flow profile for different inlet conditions. In this work, the river geometry is modeled using commercial CFD code, FLUENT®. The computational model consists of Reynolds Averaged Navier-Stokes (RANS) equations coupled with other related models using the properties of the fluids under investigation. The model is validated with site-measurements done at Tenom Pangi Hydro Power Station. Different operating condition of river flow rate and weir opening is also considered. The optimum angle is determined in this simulation to further use the data for 3D simulation and structural analysis.

Irrigation of human prepared root canal – ex vivo based computational fluid dynamics analysis

PubMed Central

Šnjarić, Damir; Čarija, Zoran; Braut, Alen; Halaji, Adelaida; Kovačević, Maja; Kuiš, Davor

2012-01-01

Aim To analyze the influence of the needle type, insertion depth, and irrigant flow rate on irrigant flow pattern, flow velocity, and apical pressure by ex-vivo based endodontic irrigation computational fluid dynamics (CFD) analysis. Methods Human upper canine root canal was prepared using rotary files. Contrast fluid was introduced in the root canal and scanned by computed tomography (CT) providing a three-dimensional object that was exported to the computer-assisted design (CAD) software. Two probe points were established in the apical portion of the root canal model for flow velocity and pressure measurement. Three different CAD models of 27G irrigation needles (closed-end side-vented, notched open-end, and bevel open-end) were created and placed at 25, 50, 75, and 95% of the working length (WL). Flow rates of 0.05, 0.1, 0.2, 0.3, and 0.4 mL/s were simulated. A total of 60 irrigation simulations were performed by CFD fluid flow solver. Results Closed-end side-vented needle required insertion depth closer to WL, regarding efficient irrigant replacement, compared to open-end irrigation needle types, which besides increased velocity produced increased irrigant apical pressure. For all irrigation needle types and needle insertion depths, the increase of flow rate was followed by an increased irrigant apical pressure. Conclusions The human root canal shape obtained by CT is applicable in the CFD analysis of endodontic irrigation. All the analyzed values –irrigant flow pattern, velocity, and pressure – were influenced by irrigation needle type, as well as needle insertion depth and irrigant flow rate. PMID:23100209

Irrigation of human prepared root canal--ex vivo based computational fluid dynamics analysis.

PubMed

Snjaric, Damir; Carija, Zoran; Braut, Alen; Halaji, Adelaida; Kovacevic, Maja; Kuis, Davor

2012-10-01

To analyze the influence of the needle type, insertion depth, and irrigant flow rate on irrigant flow pattern, flow velocity, and apical pressure by ex-vivo based endodontic irrigation computational fluid dynamics (CFD) analysis. Human upper canine root canal was prepared using rotary files. Contrast fluid was introduced in the root canal and scanned by computed tomography (CT) providing a three-dimensional object that was exported to the computer-assisted design (CAD) software. Two probe points were established in the apical portion of the root canal model for flow velocity and pressure measurement. Three different CAD models of 27G irrigation needles (closed-end side-vented, notched open-end, and bevel open-end) were created and placed at 25, 50, 75, and 95% of the working length (WL). Flow rates of 0.05, 0.1, 0.2, 0.3, and 0.4 mL/s were simulated. A total of 60 irrigation simulations were performed by CFD fluid flow solver. Closed-end side-vented needle required insertion depth closer to WL, regarding efficient irrigant replacement, compared to open-end irrigation needle types, which besides increased velocity produced increased irrigant apical pressure. For all irrigation needle types and needle insertion depths, the increase of flow rate was followed by an increased irrigant apical pressure. The human root canal shape obtained by CT is applicable in the CFD analysis of endodontic irrigation. All the analyzed values -irrigant flow pattern, velocity, and pressure - were influenced by irrigation needle type, as well as needle insertion depth and irrigant flow rate.

Computational Analysis of Human Blood Flow

NASA Astrophysics Data System (ADS)

Panta, Yogendra; Marie, Hazel; Harvey, Mark

2009-11-01

Fluid flow modeling with commercially available computational fluid dynamics (CFD) software is widely used to visualize and predict physical phenomena related to various biological systems. In this presentation, a typical human aorta model was analyzed assuming the blood flow as laminar with complaint cardiac muscle wall boundaries. FLUENT, a commercially available finite volume software, coupled with Solidworks, a modeling software, was employed for the preprocessing, simulation and postprocessing of all the models.The analysis mainly consists of a fluid-dynamics analysis including a calculation of the velocity field and pressure distribution in the blood and a mechanical analysis of the deformation of the tissue and artery in terms of wall shear stress. A number of other models e.g. T branches, angle shaped were previously analyzed and compared their results for consistency for similar boundary conditions. The velocities, pressures and wall shear stress distributions achieved in all models were as expected given the similar boundary conditions. The three dimensional time dependent analysis of blood flow accounting the effect of body forces with a complaint boundary was also performed.

Research in Parallel Algorithms and Software for Computational Aerosciences

DOT National Transportation Integrated Search

1996-04-01

Phase I is complete for the development of a Computational Fluid Dynamics : with automatic grid generation and adaptation for the Euler : analysis of flow over complex geometries. SPLITFLOW, an unstructured Cartesian : grid code developed at Lockheed...

Domain decomposition for aerodynamic and aeroacoustic analyses, and optimization

NASA Technical Reports Server (NTRS)

Baysal, Oktay

1995-01-01

The overarching theme was the domain decomposition, which intended to improve the numerical solution technique for the partial differential equations at hand; in the present study, those that governed either the fluid flow, or the aeroacoustic wave propagation, or the sensitivity analysis for a gradient-based optimization. The role of the domain decomposition extended beyond the original impetus of discretizing geometrical complex regions or writing modular software for distributed-hardware computers. It induced function-space decompositions and operator decompositions that offered the valuable property of near independence of operator evaluation tasks. The objectives have gravitated about the extensions and implementations of either the previously developed or concurrently being developed methodologies: (1) aerodynamic sensitivity analysis with domain decomposition (SADD); (2) computational aeroacoustics of cavities; and (3) dynamic, multibody computational fluid dynamics using unstructured meshes.

SPLASH program for three dimensional fluid dynamics with free surface boundaries

NASA Astrophysics Data System (ADS)

Yamaguchi, A.

1996-05-01

This paper describes a three dimensional computer program SPLASH that solves Navier-Stokes equations based on the Arbitrary Lagrangian Eulerian (ALE) finite element method. SPLASH has been developed for application to the fluid dynamics problems including the moving boundary of a liquid metal cooled Fast Breeder Reactor (FBR). To apply SPLASH code to the free surface behavior analysis, a capillary model using a cubic Spline function has been developed. Several sample problems, e.g., free surface oscillation, vortex shedding development, and capillary tube phenomena, are solved to verify the computer program. In the analyses, the numerical results are in good agreement with the theoretical value or experimental observance. Also SPLASH code has been applied to an analysis of a free surface sloshing experiment coupled with forced circulation flow in a rectangular tank. This is a simplified situation of the flow field in a reactor vessel of the FBR. The computational simulation well predicts the general behavior of the fluid flow inside and the free surface behavior. Analytical capability of the SPLASH code has been verified in this study and the application to more practical problems such as FBR design and safety analysis is under way.

Liquid Microjunction Surface Sampling Probe Fluid Dynamics: Computational and Experimental Analysis of Coaxial Intercapillary Positioning Effects on Sample Manipulation

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

ElNaggar, Mariam S; Barbier, Charlotte N; Van Berkel, Gary J

A coaxial geometry liquid microjunction surface sampling probe (LMJ-SSP) enables direct extraction of analytes from surfaces for subsequent analysis by techniques like mass spectrometry. Solution dynamics at the probe-to-sample surface interface in the LMJ-SSP has been suspected to influence sampling efficiency and dispersion but has not been rigorously investigated. The effect on flow dynamics and analyte transport to the mass spectrometer caused by coaxial retraction of the inner and outer capillaries from each other and the surface during sampling with a LMJ-SSP was investigated using computational fluid dynamics and experimentation. A transparent LMJ-SSP was constructed to provide the means formore » visual observation of the dynamics of the surface sampling process. Visual observation, computational fluid dynamics (CFD) analysis, and experimental results revealed that inner capillary axial retraction from the flush position relative to the outer capillary transitioned the probe from a continuous sampling and injection mode through an intermediate regime to sample plug formationmode caused by eddy currents at the sampling end of the probe. The potential for analytical implementation of these newly discovered probe operational modes is discussed.« less

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.

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.

Development of Multidisciplinary, Multifidelity Analysis, Integration, and Optimization of Aerospace Vehicles

DTIC Science & Technology

2010-02-27

investigated in more detail. The intermediate level of fidelity, though more expensive, is then used to refine the analysis , add geometric detail, and...design stage is used to further refine the analysis , narrowing the design to a handful of options. Figure 1. Integrated Hierarchical Framework. In...computational structural and computational fluid modeling. For the structural analysis tool we used McIntosh Structural Dynamics’ finite element code CNEVAL

The numerical approach adopted in toba computer code for mass and heat transfer dynamic analysis of metal hydride hydrogen storage beds

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

El Osery, I.A.

1983-12-01

Modelling studies of metal hydride hydrogen storage beds is a part of an extensive R and D program conducted in Egypt on hydrogen energy. In this context two computer programs; namely RET and RET1; have been developed. In RET computer program, a cylindrical conduction bed model is considered and an approximate analytical solution is used for solution of the associated mass and heat transfer problem. This problem is solved in RET1 computer program numerically allowing more flexibility in operating conditions but still limited to cylindrical configuration with only two alternatives for heat exchange; either fluid is passing through tubes imbeddedmore » in the solid alloy matrix or solid rods are surrounded by annular fluid tubes. The present computer code TOBA is more flexible and realistic. It performs the mass and heat transfer dynamic analysis of metal hydride storage beds using a variety of geometrical and operating alternatives.« less

Dual Solutions for Nonlinear Flow Using Lie Group Analysis

PubMed Central

Awais, Muhammad; Hayat, Tasawar; Irum, Sania; Saleem, Salman

2015-01-01

`The aim of this analysis is to investigate the existence of the dual solutions for magnetohydrodynamic (MHD) flow of an upper-convected Maxwell (UCM) fluid over a porous shrinking wall. We have employed the Lie group analysis for the simplification of the nonlinear differential system and computed the absolute invariants explicitly. An efficient numerical technique namely the shooting method has been employed for the constructions of solutions. Dual solutions are computed for velocity profile of an upper-convected Maxwell (UCM) fluid flow. Plots reflecting the impact of dual solutions for the variations of Deborah number, Hartman number, wall mass transfer are presented and analyzed. Streamlines are also plotted for the wall mass transfer effects when suction and blowing situations are considered. PMID:26575996

Coupled Aerodynamic and Structural Sensitivity Analysis of a High-Speed Civil Transport

NASA Technical Reports Server (NTRS)

Mason, B. H.; Walsh, J. L.

2001-01-01

An objective of the High Performance Computing and Communication Program at the NASA Langley Research Center is to demonstrate multidisciplinary shape and sizing optimization of a complete aerospace vehicle configuration by using high-fidelity, finite-element structural analysis and computational fluid dynamics aerodynamic analysis. In a previous study, a multi-disciplinary analysis system for a high-speed civil transport was formulated to integrate a set of existing discipline analysis codes, some of them computationally intensive, This paper is an extension of the previous study, in which the sensitivity analysis for the coupled aerodynamic and structural analysis problem is formulated and implemented. Uncoupled stress sensitivities computed with a constant load vector in a commercial finite element analysis code are compared to coupled aeroelastic sensitivities computed by finite differences. The computational expense of these sensitivity calculation methods is discussed.

Bulk-Flow Analysis, part A

NASA Technical Reports Server (NTRS)

Childs, Dara W.

1993-01-01

The bulk-flow analysis results for this contract are incorporated in the following publications: 'Fluid-Structure Interaction Forces at Pump-Impeller Shroud Surfaces for Axial Vibration Analysis'; 'Centrifugal Acceleration Modes for Incompressible Fluid in the Leakage Annulus Between a Shrouded Pump Impeller and Its Housing'; 'Influence of Impeller Shroud Forces on Pump Rotordynamics'; 'Pressure Oscillation in the Leakage Annulus Between a Shrouded Impeller and Its Housing Due to Impeller-Discharge-Pressure Disturbances'; and 'Compressibility Effects on Rotor Forces in the Leakage Path Between a Shrouded Pump Impeller and Its Housing'. These publications are summarized and included in this final report. Computational Fluid Mechanics (CFD) results developed by Dr. Erian Baskharone are reported separately.

Vibration exciting mechanisms induced by flow in turbomachine stages

NASA Technical Reports Server (NTRS)

Thompson, W. E.

1980-01-01

The quasisteady computer analysis of the perturbated centrifugal impeller passage flow was reviewed. A total of 115 stage calculations were used to define the fluid damping coefficient, delta sub fluid. Results indicate that the average total damping coefficient per stage needed for stability is delta sub total 1.85.

Bulk-Flow Analysis of Hybrid Thrust Bearings for Advanced Cryogenic Turbopumps

NASA Technical Reports Server (NTRS)

SanAndres, Luis

1998-01-01

A bulk-flow analysis and computer program for prediction of the static load performance and dynamic force coefficients of angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings have been completed. The product of the research is an efficient computational tool for the design of high-speed thrust bearings for cryogenic fluid turbopumps. The study addresses the needs of a growing technology that requires of reliable fluid film bearings to provide the maximum operating life with optimum controllable rotordynamic characteristics at the lowest cost. The motion of a cryogenic fluid on the thin film lands of a thrust bearing is governed by a set of bulk-flow mass and momentum conservation and energy transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. The bulk-flow model includes flow turbulence with fluid inertia advection, Coriolis and centrifugal acceleration effects on the bearing recesses and film lands. The cryogenic fluid properties are obtained from realistic thermophysical equations of state. Turbulent bulk-flow shear parameters are based on Hirs' model with Moody's friction factor equations allowing a simple simulation for machined bearing surface roughness. A perturbation analysis leads to zeroth-order nonlinear equations governing the fluid flow for the thrust bearing operating at a static equilibrium position, and first-order linear equations describing the perturbed fluid flow for small amplitude shaft motions in the axial direction. Numerical solution to the zeroth-order flow field equations renders the bearing flow rate, thrust load, drag torque and power dissipation. Solution to the first-order equations determines the axial stiffness, damping and inertia force coefficients. The computational method uses well established algorithms and generic subprograms available from prior developments. The Fortran9O computer program hydrothrust runs on a Windows 95/NT personal computer. The program, help files and examples are licensed by Texas A&M University Technology License Office. The study of the static and dynamic performance of two hydrostatic/hydrodynamic bearings demonstrates the importance of centrifugal and advection fluid inertia effects for operation at high rotational speeds. The first example considers a conceptual hydrostatic thrust bearing for an advanced liquid hydrogen turbopump operating at 170,000 rpm. The large axial stiffness and damping coefficients of the bearing should provide accurate control and axial positioning of the turbopump and also allow for unshrouded impellers, therefore increasing the overall pump efficiency. The second bearing uses a refrigerant R134a, and its application in oil-free air conditioning compressors is of great technological importance and commercial value. The computed predictions reveal that the LH2 bearing load capacity and flow rate increase with the recess pressure (i.e. increasing orifice diameters). The bearing axial stiffness has a maximum for a recess pressure rati of approx. 0.55. while the axial damping coefficient decreases as the recess pressure ratio increases. The computer results from three flow models are compared. These models are a) inertialess, b) fluid inertia at recess edges only, and c) full fluid inertia at both recess edges and film lands. The full inertia model shows the lowest flow rates, axial load capacity and stiffness coefficient but on the other hand renders the largest damping coefficients and inertia coefficients. The most important findings are related to the reduction of the outflow through the inner radius and the appearance of subambient pressures. The performance of the refrigerant hybrid thrust bearing is evaluated at two operating speeds and pressure drops. The computed results are presented in dimensionless form to evidence consistent trends in the bearing performance characteristics. As the applied axial load increases, the bearing film thickness and flow rate decrease while the recess pressure increases. The axial stiffness coefficient shows a maximum for a certain intermediate load while the damping coefficient steadily increases. The computed results evidence the paramount of centrifugal fluid inertia at low recess pressures (i.e. low loads), and where there is actually an inflow through the bearing inner diameter, accompanied by subambient pressures just downstream of the bearing recess edge. These results are solely due to centrifugal fluid inertia and advection transport effects. Recommendations include the extension of the computer program to handle flexure pivot tilting pad hybrid bearings and the ability to calculate moment coefficients for shaft angular misalignments.

Ninth Thermal and Fluids Analysis Workshop Proceedings

NASA Technical Reports Server (NTRS)

Sakowski, Barbara (Compiler)

1999-01-01

The Ninth Thermal and Fluids Analysis Workshop (TFAWS 98) was held at the Ohio Aerospace Institute in Cleveland, Ohio from August 31 to September 4, 1998. The theme for the hands-on training workshop and conference was "Integrating Computational Fluid Dynamics and Heat Transfer into the Design Process." Highlights of the workshop (in addition to the papers published herein) included an address by the NASA Chief Engineer, Dr. Daniel Mulville; a CFD short course by Dr. John D. Anderson of the University of Maryland; and a short course by Dr. Robert Cochran of Sandia National Laboratories. In addition, lectures and hands-on training were offered in the use of several cutting-edge engineering design and analysis-oriented CFD and Heat Transfer tools. The workshop resulted in international participation of over 125 persons representing aerospace and automotive industries, academia, software providers, government agencies, and private corporations. The papers published herein address issues and solutions related to the integration of computational fluid dynamics and heat transfer into the engineering design process. Although the primary focus is aerospace, the topics and ideas presented are applicable to many other areas where these and other disciplines are interdependent.

Personal Computer Transport Analysis Program

NASA Technical Reports Server (NTRS)

DiStefano, Frank, III; Wobick, Craig; Chapman, Kirt; McCloud, Peter

2012-01-01

The Personal Computer Transport Analysis Program (PCTAP) is C++ software used for analysis of thermal fluid systems. The program predicts thermal fluid system and component transients. The output consists of temperatures, flow rates, pressures, delta pressures, tank quantities, and gas quantities in the air, along with air scrubbing component performance. PCTAP s solution process assumes that the tubes in the system are well insulated so that only the heat transfer between fluid and tube wall and between adjacent tubes is modeled. The system described in the model file is broken down into its individual components; i.e., tubes, cold plates, heat exchangers, etc. A solution vector is built from the components and a flow is then simulated with fluid being transferred from one component to the next. The solution vector of components in the model file is built at the initiation of the run. This solution vector is simply a list of components in the order of their inlet dependency on other components. The component parameters are updated in the order in which they appear in the list at every time step. Once the solution vectors have been determined, PCTAP cycles through the components in the solution vector, executing their outlet function for each time-step increment.

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

Sierra Thermal/Fluid Team

SIERRA/Aero is a compressible fluid dynamics program intended to solve a wide variety compressible fluid flows including transonic and hypersonic problems. This document describes the commands for assembling a fluid model for analysis with this module, henceforth referred to simply as Aero for brevity. Aero is an application developed using the SIERRA Toolkit (STK). The intent of STK is to provide a set of tools for handling common tasks that programmers encounter when developing a code for numerical simulation. For example, components of STK provide field allocation and management, and parallel input/output of field and mesh data. These services alsomore » allow the development of coupled mechanics analysis software for a massively parallel computing environment. In the definitions of the commands that follow, the term Real_Max denotes the largest floating point value that can be represented on a given computer. Int_Max is the largest such integer value.« less

The Role of Multiphysics Simulation in Multidisciplinary Analysis

NASA Technical Reports Server (NTRS)

Rifai, Steven M.; Ferencz, Robert M.; Wang, Wen-Ping; Spyropoulos, Evangelos T.; Lawrence, Charles; Melis, Matthew E.

1998-01-01

This article describes the applications of the Spectrum(Tm) Solver in Multidisciplinary Analysis (MDA). Spectrum, a multiphysics simulation software based on the finite element method, addresses compressible and incompressible fluid flow, structural, and thermal modeling as well as the interaction between these disciplines. Multiphysics simulation is based on a single computational framework for the modeling of multiple interacting physical phenomena. Interaction constraints are enforced in a fully-coupled manner using the augmented-Lagrangian method. Within the multiphysics framework, the finite element treatment of fluids is based on Galerkin-Least-Squares (GLS) method with discontinuity capturing operators. The arbitrary-Lagrangian-Eulerian method is utilized to account for deformable fluid domains. The finite element treatment of solids and structures is based on the Hu-Washizu variational principle. The multiphysics architecture lends itself naturally to high-performance parallel computing. Aeroelastic, propulsion, thermal management and manufacturing applications are presented.

Development of an integrated BEM approach for hot fluid structure interaction

NASA Technical Reports Server (NTRS)

Dargush, G. F.; Banerjee, P. K.; Shi, Y.

1991-01-01

The development of a comprehensive fluid-structure interaction capability within a boundary element computer code is described. This new capability is implemented in a completely general manner, so that quite arbitrary geometry, material properties and boundary conditions may be specified. Thus, a single analysis code can be used to run structures-only problems, fluids-only problems, or the combined fluid-structure problem. In all three cases, steady or transient conditions can be selected, with or without thermal effects. Nonlinear analyses can be solved via direct iteration or by employing a modified Newton-Raphson approach. A number of detailed numerical examples are included at the end of these two sections to validate the formulations and to emphasize both the accuracy and generality of the computer code. A brief review of the recent applicable boundary element literature is included for completeness. The fluid-structure interaction facility is discussed. Once again, several examples are provided to highlight this unique capability. A collection of potential boundary element applications that have been uncovered as a result of work related to the present grant is given. For most of those problems, satisfactory analysis techniques do not currently exist.

Computational fluid dynamics applications at McDonnel Douglas

NASA Technical Reports Server (NTRS)

Hakkinen, R. J.

1987-01-01

Representative examples are presented of applications and development of advanced Computational Fluid Dynamics (CFD) codes for aerodynamic design at the McDonnell Douglas Corporation (MDC). Transonic potential and Euler codes, interactively coupled with boundary layer computation, and solutions of slender-layer Navier-Stokes approximation are applied to aircraft wing/body calculations. An optimization procedure using evolution theory is described in the context of transonic wing design. Euler methods are presented for analysis of hypersonic configurations, and helicopter rotors in hover and forward flight. Several of these projects were accepted for access to the Numerical Aerodynamic Simulation (NAS) facility at the NASA-Ames Research Center.

TEMPEST: A three-dimensional time-dependent computer program for hydrothermal analysis: Volume 1, Numerical methods and input instructions

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

Trent, D.S.; Eyler, L.L.; Budden, M.J.

This document describes the numerical methods, current capabilities, and the use of the TEMPEST (Version L, MOD 2) computer program. TEMPEST is a transient, three-dimensional, hydrothermal computer program that is designed to analyze a broad range of coupled fluid dynamic and heat transfer systems of particular interest to the Fast Breeder Reactor thermal-hydraulic design community. The full three-dimensional, time-dependent equations of motion, continuity, and heat transport are solved for either laminar or turbulent fluid flow, including heat diffusion and generation in both solid and liquid materials. 10 refs., 22 figs., 2 tabs.

Investigation of the effects of miniscrew-assisted rapid palatal expansion on airflow in the upper airway of an adult patient with obstructive sleep apnea syndrome using computational fluid-structure interaction analysis

PubMed Central

Hur, Jae-Sik; Kim, Hyoung-Ho; Choi, Jin-Young; Suh, Sang-Ho

2017-01-01

Objective The objective of this study was to investigate the effects of miniscrew-assisted rapid palatal expansion (MARPE) on changes in airflow in the upper airway (UA) of an adult patient with obstructive sleep apnea syndrome (OSAS) using computational fluid-structure interaction analysis. Methods Three-dimensional UA models fabricated from cone beam computed tomography images obtained before (T0) and after (T1) MARPE in an adult patient with OSAS were used for computational fluid dynamics with fluid-structure interaction analysis. Seven and nine cross-sectional planes (interplane distance of 10 mm) in the nasal cavity (NC) and pharynx, respectively, were set along UA. Changes in the cross-sectional area and changes in airflow velocity and pressure, node displacement, and total resistance at maximum inspiration (MI), rest, and maximum expiration (ME) were investigated at each plane after MARPE. Results The cross-sectional areas at most planes in NC and the upper half of the pharynx were significantly increased at T1. Moreover, airflow velocity decreased in the anterior NC at MI and ME and in the nasopharynx and oropharynx at MI. The decrease in velocity was greater in NC than in the pharynx. The airflow pressure in the anterior NC and entire pharynx exhibited a decrease at T1. The amount of node displacement in NC and the pharynx was insignificant at both T0 and T1. Absolute values for the total resistance at MI, rest, and ME were lower at T1 than at T0. Conclusions MARPE improves airflow and decreases resistance in UA; therefore, it may be an effective treatment modality for adult patients with moderate OSAS. PMID:29090123

An analysis on the magnetic fluid seal capacity

NASA Astrophysics Data System (ADS)

Meng, Zhao; Jibin, Zou; Jianhui, Hu

2006-08-01

The capacity of the magnetic fluid seal depends on the magnetic field and the saturation magnetization of the magnetic fluid. There are many factors that influence the magnetic field and the seal capacity of the magnetic fluid seal, such as the sealing gap, the shaft eccentricity, the shaft diameter, and the centrifugal force. In this paper, these factors are analyzed by numerical computations. When the material and structure are the same, the magnetic fluid seal capacity will reduce with the increasing of the sealing gap. When the shaft diameter is large the gravity should be considered. The centrifugal force has influence on the magnetic fluid seal capacity.

Non-intrusive uncertainty quantification of computational fluid dynamics simulations: notes on the accuracy and efficiency

NASA Astrophysics Data System (ADS)

Zimoń, Małgorzata; Sawko, Robert; Emerson, David; Thompson, Christopher

2017-11-01

Uncertainty quantification (UQ) is increasingly becoming an indispensable tool for assessing the reliability of computational modelling. Efficient handling of stochastic inputs, such as boundary conditions, physical properties or geometry, increases the utility of model results significantly. We discuss the application of non-intrusive generalised polynomial chaos techniques in the context of fluid engineering simulations. Deterministic and Monte Carlo integration rules are applied to a set of problems, including ordinary differential equations and the computation of aerodynamic parameters subject to random perturbations. In particular, we analyse acoustic wave propagation in a heterogeneous medium to study the effects of mesh resolution, transients, number and variability of stochastic inputs. We consider variants of multi-level Monte Carlo and perform a novel comparison of the methods with respect to numerical and parametric errors, as well as computational cost. The results provide a comprehensive view of the necessary steps in UQ analysis and demonstrate some key features of stochastic fluid flow systems.

Fluid Structure Interaction in a Turbine Blade

NASA Technical Reports Server (NTRS)

Gorla, Rama S. R.

2004-01-01

An unsteady, three dimensional Navier-Stokes solution in rotating frame formulation for turbomachinery applications is presented. Casting the governing equations in a rotating frame enabled the freezing of grid motion and resulted in substantial savings in computer time. The turbine blade was computationally simulated and probabilistically evaluated in view of several uncertainties in the aerodynamic, structural, material and thermal variables that govern the turbine blade. The interconnection between the computational fluid dynamics code and finite element structural analysis code was necessary to couple the thermal profiles with the structural design. The stresses and their variations were evaluated at critical points on the Turbine blade. Cumulative distribution functions and sensitivity factors were computed for stress responses due to aerodynamic, geometric, mechanical and thermal random variables.

A New Modular Approach for Tightly Coupled Fluid/Structure Analysis

NASA Technical Reports Server (NTRS)

Guruswamy, Guru

2003-01-01

Static aeroelastic computations are made using a C++ executive suitable for closely coupled fluid/structure interaction studies. The fluid flow is modeled using the Euler/Navier Stokes equations and the structure is modeled using finite elements. FORTRAN based fluids and structures codes are integrated under C++ environment. The flow and structural solvers are treated as separate object files. The data flow between fluids and structures is accomplished using I/O. Results are demonstrated for transonic flow over partially flexible surface that is important for aerospace vehicles. Use of this development to accurately predict flow induced structural failure will be demonstrated.

Numerical and experimental analysis of a thin liquid film on a rotating disk related to development of a spacecraft absorption cooling system

NASA Technical Reports Server (NTRS)

Faghri, Amir; Swanson, Theodore D.

1989-01-01

The numerical and experimental analysis of a thin liquid film on a rotating and a stationary disk related to the development of an absorber unit for a high capacity spacecraft absorption cooling system, is described. The creation of artificial gravity by the use of a centrifugal field was focused upon in this report. Areas covered include: (1) One-dimensional computation of thin liquid film flows; (2) Experimental measurement of film height and visualization of flow; (3) Two-dimensional computation of the free surface flow of a thin liquid film using a pressure optimization method; (4) Computation of heat transfer in two-dimensional thin film flow; (5) Development of a new computational methodology for the free surface flows using a permeable wall; (6) Analysis of fluid flow and heat transfer in a thin film in the presence and absence of gravity; and (7) Comparison of theoretical prediction and experimental data. The basic phenomena related to fluid flow and heat transfer on rotating systems reported here can also be applied to other areas of space systems.

A magnetic fluid seal for rotary blood pumps: image and computational analyses of behaviors of magnetic fluids.

PubMed

Mitamura, Yoshinori; Yano, Tetsuya; Okamoto, Eiji

2013-01-01

A magnetic fluid (MF) seal has excellent durability. The performance of an MF seal, however, has been reported to decrease in liquids (several days). We have developed an MF seal that has a shield mechanism. The seal was perfect for 275 days in water. To investigate the effect of a shield, behaviors of MFs in a seal in water were studied both experimentally and computationally. (a) Two kinds of MF seals, one with a shield and one without a shield, were installed in a centrifugal pump. Behaviors of MFs in the seals in water were observed with a video camera and high-speed microscope. In the seal without a shield, the surface of the water in the seal waved and the turbulent flow affected behaviors of the MFs. In contrast, MFs rotated stably in the seal with a shield in water even at high rotational speeds. (b) Computational fluid dynamics analysis revealed that a stationary secondary flow pattern in the seal and small velocity difference between magnetic fluid and water at the interface. These MF behaviors prolonged the life of an MF seal in water.

Design approach of an aquaculture cage system for deployment in the constructed channel flow environments of a power plant

PubMed Central

Lee, Jihoon; Fredriksson, David W.; DeCew, Judson; Drach, Andrew; Yim, Solomon C.

2018-01-01

This study provides an engineering approach for designing an aquaculture cage system for use in constructed channel flow environments. As sustainable aquaculture has grown globally, many novel techniques have been introduced such as those implemented in the global Atlantic salmon industry. The advent of several highly sophisticated analysis software systems enables the development of such novel engineering techniques. These software systems commonly include three-dimensional (3D) drafting, computational fluid dynamics, and finite element analysis. In this study, a combination of these analysis tools is applied to evaluate a conceptual aquaculture system for potential deployment in a power plant effluent channel. The channel is supposedly clean; however, it includes elevated water temperatures and strong currents. The first portion of the analysis includes the design of a fish cage system with specific net solidities using 3D drafting techniques. Computational fluid dynamics is then applied to evaluate the flow reduction through the system from the previously generated solid models. Implementing the same solid models, a finite element analysis is performed on the critical components to assess the material stresses produced by the drag force loads that are calculated from the fluid velocities. PMID:29897954

Operation of the Institute for Computer Applications in Science and Engineering

NASA Technical Reports Server (NTRS)

1975-01-01

The ICASE research program is described in detail; it consists of four major categories: (1) efficient use of vector and parallel computers, with particular emphasis on the CDC STAR-100; (2) numerical analysis, with particular emphasis on the development and analysis of basic numerical algorithms; (3) analysis and planning of large-scale software systems; and (4) computational research in engineering and the natural sciences, with particular emphasis on fluid dynamics. The work in each of these areas is described in detail; other activities are discussed, a prognosis of future activities are included.

2D Mesh Manipulation

DTIC Science & Technology

2011-11-01

the Poisson form of the equations can also be generated by manipulating the computational space , so forcing functions become superfluous . The...ABSTRACT Unstructured methods for region discretization have become common in computational fluid dynamics (CFD) analysis because of certain benefits...application of Winslow elliptic smoothing equations to unstructured meshes. It has been shown that it is not necessary for the computational space of

ICASE

NASA Technical Reports Server (NTRS)

1994-01-01

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in the areas of (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest, including acoustics and combustion; (3) experimental research in transition and turbulence and aerodynamics involving Langley facilities and scientists; and (4) computer science.

Interpolation Method Needed for Numerical Uncertainty Analysis of Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Groves, Curtis; Ilie, Marcel; Schallhorn, Paul

2014-01-01

Using Computational Fluid Dynamics (CFD) to predict a flow field is an approximation to the exact problem and uncertainties exist. There is a method to approximate the errors in CFD via Richardson's Extrapolation. This method is based off of progressive grid refinement. To estimate the errors in an unstructured grid, the analyst must interpolate between at least three grids. This paper describes a study to find an appropriate interpolation scheme that can be used in Richardson's extrapolation or other uncertainty method to approximate errors. Nomenclature

Thermohydrodynamic Analysis of Cryogenic Liquid Turbulent Flow Fluid Film Bearings

NASA Technical Reports Server (NTRS)

SanAndres, Luis

1996-01-01

Computational programs developed for the thermal analysis of tilting and flexure-pad hybrid bearings, and the unsteady flow and transient response of a point mass rotor supported on fluid film bearings are described. The motion of a cryogenic liquid on the thin film annular region of a fluid film bearing is described by a set of mass and momentum conservation, and energy transport equations for the turbulent bulk-flow velocities and pressure, and accompanied by thermophysical state equations for evaluation of the fluid material properties. Zeroth-order equations describe the fluid flow field for a journal static equilibrium position, while first-order (linear) equations govern the fluid flow for small amplitude-journal center translational motions. Solution to the zeroth-order flow field equations provides the bearing flow rate, load capacity, drag torque and temperature rise. Solution to the first-order equations determines the rotordynamic force coefficients due to journal radial motions.

Aeroelastic Analysis Of Joined Wing Of High Altitude Long Endurance (HALE) Aircraft Based On The Sensor-Craft Configuration

NASA Astrophysics Data System (ADS)

Marisarla, Soujanya; Ghia, Urmila; "Karman" Ghia, Kirti

2002-11-01

Towards a comprehensive aeroelastic analysis of a joined wing, fluid dynamics and structural analyses are initially performed separately. Steady flow calculations are currently performed using 3-D compressible Navier-Stokes equations. Flow analysis of M6-Onera wing served to validate the software for the fluid dynamics analysis. The complex flow field of the joined wing is analyzed and the prevailing fluid dynamic forces are computed using COBALT software. Currently, these forces are being transferred as fluid loads on the structure. For the structural analysis, several test cases were run considering the wing as a cantilever beam; these served as validation cases. A nonlinear structural analysis of the wing is being performed using ANSYS software to predict the deflections and stresses on the joined wing. Issues related to modeling, and selecting appropriate mesh for the structure were addressed by first performing a linear analysis. The frequencies and mode shapes of the deformed wing are obtained from modal analysis. Both static and dynamic analyses are carried out, and the results obtained are carefully analyzed. Loose coupling between the fluid and structural analyses is currently being examined.

Effects of Fluid Environment on Microbial Uptake Kinetics

DTIC Science & Technology

1990-09-26

Marine snow parti- is crucial for the performance of all biological wastewater cles, large amorphous aggregates that form in marine sys - treatment...particle trajectories in computer models (Tambo and Wata- nabe 1979). These computer-generated aggregates, de- the %%ater column (Table 2). This analysis

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

Computational Particle Dynamic Simulations on Multicore Processors (CPDMu) Final Report Phase I

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

Schmalz, Mark S

2011-07-24

Statement of Problem - Department of Energy has many legacy codes for simulation of computational particle dynamics and computational fluid dynamics applications that are designed to run on sequential processors and are not easily parallelized. Emerging high-performance computing architectures employ massively parallel multicore architectures (e.g., graphics processing units) to increase throughput. Parallelization of legacy simulation codes is a high priority, to achieve compatibility, efficiency, accuracy, and extensibility. General Statement of Solution - A legacy simulation application designed for implementation on mainly-sequential processors has been represented as a graph G. Mathematical transformations, applied to G, produce a graph representation {und G}more » for a high-performance architecture. Key computational and data movement kernels of the application were analyzed/optimized for parallel execution using the mapping G {yields} {und G}, which can be performed semi-automatically. This approach is widely applicable to many types of high-performance computing systems, such as graphics processing units or clusters comprised of nodes that contain one or more such units. Phase I Accomplishments - Phase I research decomposed/profiled computational particle dynamics simulation code for rocket fuel combustion into low and high computational cost regions (respectively, mainly sequential and mainly parallel kernels), with analysis of space and time complexity. Using the research team's expertise in algorithm-to-architecture mappings, the high-cost kernels were transformed, parallelized, and implemented on Nvidia Fermi GPUs. Measured speedups (GPU with respect to single-core CPU) were approximately 20-32X for realistic model parameters, without final optimization. Error analysis showed no loss of computational accuracy. Commercial Applications and Other Benefits - The proposed research will constitute a breakthrough in solution of problems related to efficient parallel computation of particle and fluid dynamics simulations. These problems occur throughout DOE, military and commercial sectors: the potential payoff is high. We plan to license or sell the solution to contractors for military and domestic applications such as disaster simulation (aerodynamic and hydrodynamic), Government agencies (hydrological and environmental simulations), and medical applications (e.g., in tomographic image reconstruction). Keywords - High-performance Computing, Graphic Processing Unit, Fluid/Particle Simulation. Summary for Members of Congress - Department of Energy has many simulation codes that must compute faster, to be effective. The Phase I research parallelized particle/fluid simulations for rocket combustion, for high-performance computing systems.« less

Aeroelasticity of wing and wing-body configurations on parallel computers

NASA Technical Reports Server (NTRS)

Byun, Chansup

1995-01-01

The objective of this research is to develop computationally efficient methods for solving aeroelasticity problems on parallel computers. Both uncoupled and coupled methods are studied in this research. For the uncoupled approach, the conventional U-g method is used to determine the flutter boundary. The generalized aerodynamic forces required are obtained by the pulse transfer-function analysis method. For the coupled approach, the fluid-structure interaction is obtained by directly coupling finite difference Euler/Navier-Stokes equations for fluids and finite element dynamics equations for structures. This capability will significantly impact many aerospace projects of national importance such as Advanced Subsonic Civil Transport (ASCT), where the structural stability margin becomes very critical at the transonic region. This research effort will have direct impact on the High Performance Computing and Communication (HPCC) Program of NASA in the area of parallel computing.

An experimental-computational analysis of MHV cavitation: effects of leaflet squeezing and rebound.

PubMed

Makhijani, V B; Yang, H Q; Singhal, A K; Hwang, N H

1994-04-01

A combined experimental-computational study was performed to investigate the flow mechanics which could cause cavitation during the squeezing and rebounding phases of valve closure in the 29 mm mitral bileaflet Edwards-Duromedics (ED) mechanical heart valve (MHV). Leaflet closing motion was measured in vitro, and input into a computational fluid mechanics software package, CFD-ACE, to compute flow velocities and pressures in the small gap space between the occluder tip and valve housing. The possibility of cavitation inception was predicted when fluid pressures dropped below the saturated vapor pressure for blood plasma. The computational analysis indicated that cavitation is more likely to be induced during valve rebound rather than the squeezing phase of valve closure in the 29 mm ED-MHV. Also, there is a higher probability of cavitation at lower values of the gap width at the point of impact between the leaflet tip and housing. These predictions of cavitation inception are not likely to be significantly influenced by the water-hammer pressure gradient that develops during valve closure.

Analysis of high injection pressure and ambient temperature on biodiesel spray characteristics using computational fluid dynamics

NASA Astrophysics Data System (ADS)

Hashim, Akasha; Khalid, Amir; Jaat, Norrizam; Sapit, Azwan; Razali, Azahari; Nizam, Akmal

2017-09-01

Efficiency of combustion engines are highly affected by the formation of air-fuel mixture prior to ignition and combustion process. This research investigate the mixture formation and spray characteristics of biodiesel blends under variant in high ambient and injection conditions using Computational Fluid Dynamics (CFD). The spray characteristics such as spray penetration length, spray angle and fluid flow were observe under various operating conditions. Results show that increase in injection pressure increases the spray penetration length for both biodiesel and diesel. Results also indicate that higher spray angle of biodiesel can be seen as the injection pressure increases. This study concludes that spray characteristics of biodiesel blend is greatly affected by the injection and ambient conditions.

On the role of fluids in stick-slip dynamics of saturated granular fault gouge using a coupled computational fluid dynamics-discrete element approach

NASA Astrophysics Data System (ADS)

Dorostkar, Omid; Guyer, Robert A.; Johnson, Paul A.; Marone, Chris; Carmeliet, Jan

2017-05-01

The presence of fault gouge has considerable influence on slip properties of tectonic faults and the physics of earthquake rupture. The presence of fluids within faults also plays a significant role in faulting and earthquake processes. In this paper, we present 3-D discrete element simulations of dry and fluid-saturated granular fault gouge and analyze the effect of fluids on stick-slip behavior. Fluid flow is modeled using computational fluid dynamics based on the Navier-Stokes equations for an incompressible fluid and modified to take into account the presence of particles. Analysis of a long time train of slip events shows that the (1) drop in shear stress, (2) compaction of granular layer, and (3) the kinetic energy release during slip all increase in magnitude in the presence of an incompressible fluid, compared to dry conditions. We also observe that on average, the recurrence interval between slip events is longer for fluid-saturated granular fault gouge compared to the dry case. This observation is consistent with the occurrence of larger events in the presence of fluid. It is found that the increase in kinetic energy during slip events for saturated conditions can be attributed to the increased fluid flow during slip. Our observations emphasize the important role that fluid flow and fluid-particle interactions play in tectonic fault zones and show in particular how discrete element method (DEM) models can help understand the hydromechanical processes that dictate fault slip.

High-Performance Parallel Analysis of Coupled Problems for Aircraft Propulsion

NASA Technical Reports Server (NTRS)

Felippa, C. A.; Farhat, C.; Park, K. C.; Gumaste, U.; Chen, P.-S.; Lesoinne, M.; Stern, P.

1996-01-01

This research program dealt with the application of high-performance computing methods to the numerical simulation of complete jet engines. The program was initiated in January 1993 by applying two-dimensional parallel aeroelastic codes to the interior gas flow problem of a bypass jet engine. The fluid mesh generation, domain decomposition and solution capabilities were successfully tested. Attention was then focused on methodology for the partitioned analysis of the interaction of the gas flow with a flexible structure and with the fluid mesh motion driven by these structural displacements. The latter is treated by a ALE technique that models the fluid mesh motion as that of a fictitious mechanical network laid along the edges of near-field fluid elements. New partitioned analysis procedures to treat this coupled three-component problem were developed during 1994 and 1995. These procedures involved delayed corrections and subcycling, and have been successfully tested on several massively parallel computers, including the iPSC-860, Paragon XP/S and the IBM SP2. For the global steady-state axisymmetric analysis of a complete engine we have decided to use the NASA-sponsored ENG10 program, which uses a regular FV-multiblock-grid discretization in conjunction with circumferential averaging to include effects of blade forces, loss, combustor heat addition, blockage, bleeds and convective mixing. A load-balancing preprocessor tor parallel versions of ENG10 was developed. During 1995 and 1996 we developed the capability tor the first full 3D aeroelastic simulation of a multirow engine stage. This capability was tested on the IBM SP2 parallel supercomputer at NASA Ames. Benchmark results were presented at the 1196 Computational Aeroscience meeting.

Multidisciplinary High-Fidelity Analysis and Optimization of Aerospace Vehicles. Part 2; Preliminary Results

NASA Technical Reports Server (NTRS)

Walsh, J. L.; Weston, R. P.; Samareh, J. A.; Mason, B. H.; Green, L. L.; Biedron, R. T.

2000-01-01

An objective of the High Performance Computing and Communication Program at the NASA Langley Research Center is to demonstrate multidisciplinary shape and sizing optimization of a complete aerospace vehicle configuration by using high-fidelity finite-element structural analysis and computational fluid dynamics aerodynamic analysis in a distributed, heterogeneous computing environment that includes high performance parallel computing. A software system has been designed and implemented to integrate a set of existing discipline analysis codes, some of them computationally intensive, into a distributed computational environment for the design of a high-speed civil transport configuration. The paper describes both the preliminary results from implementing and validating the multidisciplinary analysis and the results from an aerodynamic optimization. The discipline codes are integrated by using the Java programming language and a Common Object Request Broker Architecture compliant software product. A companion paper describes the formulation of the multidisciplinary analysis and optimization system.

Practical quality control tools for curves and surfaces

NASA Technical Reports Server (NTRS)

Small, Scott G.

1992-01-01

Curves (geometry) and surfaces created by Computer Aided Geometric Design systems in the engineering environment must satisfy two basic quality criteria: the geometric shape must have the desired engineering properties; and the objects must be parameterized in a way which does not cause computational difficulty for geometric processing and engineering analysis. Interactive techniques are described which are in use at Boeing to evaluate the quality of aircraft geometry prior to Computational Fluid Dynamic analysis, including newly developed methods for examining surface parameterization and its effects.

Remote Visualization and Remote Collaboration On Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Watson, Val; Lasinski, T. A. (Technical Monitor)

1995-01-01

A new technology has been developed for remote visualization that provides remote, 3D, high resolution, dynamic, interactive viewing of scientific data (such as fluid dynamics simulations or measurements). Based on this technology, some World Wide Web sites on the Internet are providing fluid dynamics data for educational or testing purposes. This technology is also being used for remote collaboration in joint university, industry, and NASA projects in computational fluid dynamics and wind tunnel testing. Previously, remote visualization of dynamic data was done using video format (transmitting pixel information) such as video conferencing or MPEG movies on the Internet. The concept for this new technology is to send the raw data (e.g., grids, vectors, and scalars) along with viewing scripts over the Internet and have the pixels generated by a visualization tool running on the viewer's local workstation. The visualization tool that is currently used is FAST (Flow Analysis Software Toolkit).

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.

Flow Applications of the Least Squares Finite Element Method

NASA Technical Reports Server (NTRS)

Jiang, Bo-Nan

1998-01-01

The main thrust of the effort has been towards the development, analysis and implementation of the least-squares finite element method (LSFEM) for fluid dynamics and electromagnetics applications. In the past year, there were four major accomplishments: 1) special treatments in computational fluid dynamics and computational electromagnetics, such as upwinding, numerical dissipation, staggered grid, non-equal order elements, operator splitting and preconditioning, edge elements, and vector potential are unnecessary; 2) the analysis of the LSFEM for most partial differential equations can be based on the bounded inverse theorem; 3) the finite difference and finite volume algorithms solve only two Maxwell equations and ignore the divergence equations; and 4) the first numerical simulation of three-dimensional Marangoni-Benard convection was performed using the LSFEM.

Nondestructive microimaging during preclinical pin-on-plate testing of novel materials for arthroplasty.

PubMed

Teeter, Matthew G; Langohr, G Daniel G; Medley, John B; Holdsworth, David W

2014-02-01

The purpose of this study was to determine the ability of micro-computed tomography to quantify wear in preclinical pin-on-plate testing of materials for use in joint arthroplasty. Wear testing of CoCr pins articulating against six polyetheretherketone plates was performed using a pin-on-plate apparatus over 2 million cycles. Change in volume due to wear was quantified with gravimetric analysis and with micro-computed tomography, and the volumes were compared. Separately, the volume of polyetheretherketone pin-on-plate specimens that had been soaking in fluid for 52 weeks was quantified with both gravimetric analysis and micro-computed tomography, and repeated after drying. The volume change with micro-computed tomography was compared to the mass change with gravimetric analysis. The mean wear volume measured was 8.02 ± 6.38 mm(3) with gravimetric analysis and 6.76 ± 5.38 mm(3) with micro-computed tomography (p = 0.06). Micro-computed tomography volume measurements did not show a statistically significant change with drying for either the plates (p = 0.60) or the pins (p = 0.09), yet drying had a significant effect on the gravimetric mass measurements for both the plates (p = 0.03) and the pins (p = 0.04). Micro-computed tomography provided accurate measurements of wear in polyetheretherketone pin-on-plate test specimens, and no statistically significant change was caused by fluid uptake. Micro-computed tomography quantifies wear depth and wear volume, mapped to the specific location of damage on the specimen, and is also capable of examining subsurface density as well as cracking. Its noncontact, nondestructive nature makes it ideal for preclinical testing of materials, in which further additional analysis techniques may be utilized.

Multiphase fluid-solid coupled analysis of shock-bubble-stone interaction in shockwave lithotripsy.

PubMed

Wang, Kevin G

2017-10-01

A novel multiphase fluid-solid-coupled computational framework is applied to investigate the interaction of a kidney stone immersed in liquid with a lithotripsy shock wave (LSW) and a gas bubble near the stone. The main objective is to elucidate the effects of a bubble in the shock path to the elastic and fracture behaviors of the stone. The computational framework couples a finite volume 2-phase computational fluid dynamics solver with a finite element computational solid dynamics solver. The surface of the stone is represented as a dynamic embedded boundary in the computational fluid dynamics solver. The evolution of the bubble surface is captured by solving the level set equation. The interface conditions at the surfaces of the stone and the bubble are enforced through the construction and solution of local fluid-solid and 2-fluid Riemann problems. This computational framework is first verified for 3 example problems including a 1D multimaterial Riemann problem, a 3D shock-stone interaction problem, and a 3D shock-bubble interaction problem. Next, a series of shock-bubble-stone-coupled simulations are presented. This study suggests that the dynamic response of a bubble to LSW varies dramatically depending on its initial size. Bubbles with an initial radius smaller than a threshold collapse within 1 μs after the passage of LSW, whereas larger bubbles do not. For a typical LSW generated by an electrohydraulic lithotripter (p max  = 35.0MPa, p min  =- 10.1MPa), this threshold is approximately 0.12mm. Moreover, this study suggests that a noncollapsing bubble imposes a negative effect on stone fracture as it shields part of the LSW from the stone. On the other hand, a collapsing bubble may promote fracture on the proximal surface of the stone, yet hinder fracture from stone interior. Copyright © 2016 John Wiley & Sons, Ltd.

High-performance parallel analysis of coupled problems for aircraft propulsion

NASA Technical Reports Server (NTRS)

Felippa, C. A.; Farhat, C.; Chen, P.-S.; Gumaste, U.; Leoinne, M.; Stern, P.

1995-01-01

This research program deals with the application of high-performance computing methods to the numerical simulation of complete jet engines. The program was initiated in 1993 by applying two-dimensional parallel aeroelastic codes to the interior gas flow problem of a by-pass jet engine. The fluid mesh generation, domain decomposition and solution capabilities were successfully tested. Attention was then focused on methodology for the partitioned analysis of the interaction of the gas flow with a flexible structure and with the fluid mesh motion driven by these structural displacements. The latter is treated by an ALE technique that models the fluid mesh motion as that of a fictitious mechanical network laid along the edges of near-field fluid elements. New partitioned analysis procedures to treat this coupled 3-component problem were developed in 1994. These procedures involved delayed corrections and subcycling, and have been successfully tested on several massively parallel computers. For the global steady-state axisymmetric analysis of a complete engine we have decided to use the NASA-sponsored ENG10 program, which uses a regular FV-multiblock-grid discretization in conjunction with circumferential averaging to include effects of blade forces, loss, combustor heat addition, blockage, bleeds and convective mixing. A load-balancing preprocessor for parallel versions of ENG10 has been developed. It is planned to use the steady-state global solution provided by ENG10 as input to a localized three-dimensional FSI analysis for engine regions where aeroelastic effects may be important.

ANALYSIS OF FLOW THROUGH A HUMAN ORAL MODEL FOR USE IN INHALATION TOXICOLOGY AND AEROSOL THERAPY PROTOCOLS

EPA Science Inventory

RATIONALE
Understanding the transport and deposition of inhaled aerosols is of fundamental importance to inhalation toxicology and aerosol therapy. Herein, we focus on the development of a computer based oral morphology and related computational fluid dynamics (CFD) studi...

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.

Fluid Analysis and Improved Structure of an ATEG Heat Exchanger Based on Computational Fluid Dynamics

NASA Astrophysics Data System (ADS)

Tang, Z. B.; Deng, Y. D.; Su, C. Q.; Yuan, X. H.

2015-06-01

In this study, a numerical model has been employed to analyze the internal flow field distribution in a heat exchanger applied for an automotive thermoelectric generator based on computational fluid dynamics. The model simulates the influence of factors relevant to the heat exchanger, including the automotive waste heat mass flow velocity, temperature, internal fins, and back pressure. The result is in good agreement with experimental test data. Sensitivity analysis of the inlet parameters shows that increase of the exhaust velocity, compared with the inlet temperature, makes little contribution (0.1 versus 0.19) to the heat transfer but results in a detrimental back pressure increase (0.69 versus 0.21). A configuration equipped with internal fins is proved to offer better thermal performance compared with that without fins. Finally, based on an attempt to improve the internal flow field, a more rational structure is obtained, offering a more homogeneous temperature distribution, higher average heat transfer coefficient, and lower back pressure.

Multidisciplinary High-Fidelity Analysis and Optimization of Aerospace Vehicles. Part 1; Formulation

NASA Technical Reports Server (NTRS)

Walsh, J. L.; Townsend, J. C.; Salas, A. O.; Samareh, J. A.; Mukhopadhyay, V.; Barthelemy, J.-F.

2000-01-01

An objective of the High Performance Computing and Communication Program at the NASA Langley Research Center is to demonstrate multidisciplinary shape and sizing optimization of a complete aerospace vehicle configuration by using high-fidelity, finite element structural analysis and computational fluid dynamics aerodynamic analysis in a distributed, heterogeneous computing environment that includes high performance parallel computing. A software system has been designed and implemented to integrate a set of existing discipline analysis codes, some of them computationally intensive, into a distributed computational environment for the design of a highspeed civil transport configuration. The paper describes the engineering aspects of formulating the optimization by integrating these analysis codes and associated interface codes into the system. The discipline codes are integrated by using the Java programming language and a Common Object Request Broker Architecture (CORBA) compliant software product. A companion paper presents currently available results.

Computations of Axisymmetric Flows in Hypersonic Shock Tubes

NASA Technical Reports Server (NTRS)

Sharma, Surendra P.; Wilson, Gregory J.

1995-01-01

A time-accurate two-dimensional fluid code is used to compute test times in shock tubes operated at supersonic speeds. Unlike previous studies, this investigation resolves the finer temporal details of the shock-tube flow by making use of modern supercomputers and state-of-the-art computational fluid dynamic solution techniques. The code, besides solving the time-dependent fluid equations, also accounts for the finite rate chemistry in the hypersonic environment. The flowfield solutions are used to estimate relevant shock-tube parameters for laminar flow, such as test times, and to predict density and velocity profiles. Boundary-layer parameters such as bar-delta(sub u), bar-delta(sup *), and bar-tau(sub w), and test time parameters such as bar-tau and particle time of flight t(sub f), are computed and compared with those evaluated by using Mirels' correlations. This article then discusses in detail the effects of flow nonuniformities on particle time-of-flight behind the normal shock and, consequently, on the interpretation of shock-tube data. This article concludes that for accurate interpretation of shock-tube data, a detailed analysis of flowfield parameters, using a computer code such as used in this study, must be performed.

Tracking interface and common curve dynamics for two-fluid flow in porous media

DOE PAGES

Mcclure, James E.; Miller, Cass T.; Gray, W. G.; ...

2016-04-29

Pore-scale studies of multiphase flow in porous medium systems can be used to understand transport mechanisms and quantitatively determine closure relations that better incorporate microscale physics into macroscale models. Multiphase flow simulators constructed using the lattice Boltzmann method provide a means to conduct such studies, including both the equilibrium and dynamic aspects. Moving, storing, and analyzing the large state space presents a computational challenge when highly-resolved models are applied. We present an approach to simulate multiphase flow processes in which in-situ analysis is applied to track multiphase flow dynamics at high temporal resolution. We compute a comprehensive set of measuresmore » of the phase distributions and the system dynamics, which can be used to aid fundamental understanding and inform closure relations for macroscale models. The measures computed include microscale point representations and macroscale averages of fluid saturations, the pressure and velocity of the fluid phases, interfacial areas, interfacial curvatures, interface and common curve velocities, interfacial orientation tensors, phase velocities and the contact angle between the fluid-fluid interface and the solid surface. Test cases are studied to validate the approach and illustrate how measures of system state can be obtained and used to inform macroscopic theory.« less

Analysis of Aerospike Plume Induced Base-Heating Environment

NASA Technical Reports Server (NTRS)

Wang, Ten-See

1998-01-01

Computational analysis is conducted to study the effect of an aerospike engine plume on X-33 base-heating environment during ascent flight. To properly account for the effect of forebody and aftbody flowfield such as shocks and to allow for potential plume-induced flow-separation, thermo-flowfield of trajectory points is computed. The computational methodology is based on a three-dimensional finite-difference, viscous flow, chemically reacting, pressure-base computational fluid dynamics formulation, and a three-dimensional, finite-volume, spectral-line based weighted-sum-of-gray-gases radiation absorption model computational heat transfer formulation. The predicted convective and radiative base-heat fluxes are presented.

A theoretical method for the analysis and design of axisymmetric bodies. [flow distribution and incompressible fluids

NASA Technical Reports Server (NTRS)

Beatty, T. D.

1975-01-01

A theoretical method is presented for the computation of the flow field about an axisymmetric body operating in a viscous, incompressible fluid. A potential flow method was used to determine the inviscid flow field and to yield the boundary conditions for the boundary layer solutions. Boundary layer effects in the forces of displacement thickness and empirically modeled separation streamlines are accounted for in subsequent potential flow solutions. This procedure is repeated until the solutions converge. An empirical method was used to determine base drag allowing configuration drag to be computed.

Computational Fluid Dynamics Technology for Hypersonic Applications

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2003-01-01

Several current challenges in computational fluid dynamics and aerothermodynamics for hypersonic vehicle applications are discussed. Example simulations are presented from code validation and code benchmarking efforts to illustrate capabilities and limitations. Opportunities to advance the state-of-art in algorithms, grid generation and adaptation, and code validation are identified. Highlights of diverse efforts to address these challenges are then discussed. One such effort to re-engineer and synthesize the existing analysis capability in LAURA, VULCAN, and FUN3D will provide context for these discussions. The critical (and evolving) role of agile software engineering practice in the capability enhancement process is also noted.

Special purpose computer system with highly parallel pipelines for flow visualization using holography technology

NASA Astrophysics Data System (ADS)

Masuda, Nobuyuki; Sugie, Takashige; Ito, Tomoyoshi; Tanaka, Shinjiro; Hamada, Yu; Satake, Shin-ichi; Kunugi, Tomoaki; Sato, Kazuho

2010-12-01

We have designed a PC cluster system with special purpose computer boards for visualization of fluid flow using digital holographic particle tracking velocimetry (DHPTV). In this board, there is a Field Programmable Gate Array (FPGA) chip in which is installed a pipeline for calculating the intensity of an object from a hologram by fast Fourier transform (FFT). This cluster system can create 1024 reconstructed images from a 1024×1024-grid hologram in 0.77 s. It is expected that this system will contribute to the analysis of fluid flow using DHPTV.

An assessment of computational fluid dynamic techniques in the analysis and design of turbomachinery - The 1990 Freeman Scholar Lecture

NASA Technical Reports Server (NTRS)

Lakshminarayana, B.

1991-01-01

Various computational fluid dynamic techniques are reviewed focusing on the Euler and Navier-Stokes solvers with a brief assessment of boundary layer solutions, and quasi-3D and quasi-viscous techniques. Particular attention is given to a pressure-based method, explicit and implicit time marching techniques, a pseudocompressibility technique for incompressible flow, and zonal techniques. Recommendations are presented with regard to the most appropriate technique for various flow regimes and types of turbomachinery, incompressible and compressible flows, cascades, rotors, stators, liquid-handling, and gas-handling turbomachinery.

Calculation of three-dimensional, inviscid, supersonic, steady flows

NASA Technical Reports Server (NTRS)

Moretti, G.

1981-01-01

A detailed description of a computational program for the evaluation of three dimensional supersonic, inviscid, steady flow past airplanes is presented. Emphasis was put on how a powerful, automatic mapping technique is coupled to the fluid mechanical analysis. Each of the three constituents of the analysis (body geometry, mapping technique, and gas dynamical effects) was carefully coded and described. Results of computations based on sample geometrics and discussions are also presented.

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

Multidisciplinary System Reliability Analysis

NASA Technical Reports Server (NTRS)

Mahadevan, Sankaran; Han, Song; Chamis, Christos C. (Technical Monitor)

2001-01-01

The objective of this study is to develop a new methodology for estimating the reliability of engineering systems that encompass multiple disciplines. The methodology is formulated in the context of the NESSUS probabilistic structural analysis code, developed under the leadership of NASA Glenn Research Center. The NESSUS code has been successfully applied to the reliability estimation of a variety of structural engineering systems. This study examines whether the features of NESSUS could be used to investigate the reliability of systems in other disciplines such as heat transfer, fluid mechanics, electrical circuits etc., without considerable programming effort specific to each discipline. In this study, the mechanical equivalence between system behavior models in different disciplines are investigated to achieve this objective. A new methodology is presented for the analysis of heat transfer, fluid flow, and electrical circuit problems using the structural analysis routines within NESSUS, by utilizing the equivalence between the computational quantities in different disciplines. This technique is integrated with the fast probability integration and system reliability techniques within the NESSUS code, to successfully compute the system reliability of multidisciplinary systems. Traditional as well as progressive failure analysis methods for system reliability estimation are demonstrated, through a numerical example of a heat exchanger system involving failure modes in structural, heat transfer and fluid flow disciplines.

Multi-Disciplinary System Reliability Analysis

NASA Technical Reports Server (NTRS)

Mahadevan, Sankaran; Han, Song

1997-01-01

The objective of this study is to develop a new methodology for estimating the reliability of engineering systems that encompass multiple disciplines. The methodology is formulated in the context of the NESSUS probabilistic structural analysis code developed under the leadership of NASA Lewis Research Center. The NESSUS code has been successfully applied to the reliability estimation of a variety of structural engineering systems. This study examines whether the features of NESSUS could be used to investigate the reliability of systems in other disciplines such as heat transfer, fluid mechanics, electrical circuits etc., without considerable programming effort specific to each discipline. In this study, the mechanical equivalence between system behavior models in different disciplines are investigated to achieve this objective. A new methodology is presented for the analysis of heat transfer, fluid flow, and electrical circuit problems using the structural analysis routines within NESSUS, by utilizing the equivalence between the computational quantities in different disciplines. This technique is integrated with the fast probability integration and system reliability techniques within the NESSUS code, to successfully compute the system reliability of multi-disciplinary systems. Traditional as well as progressive failure analysis methods for system reliability estimation are demonstrated, through a numerical example of a heat exchanger system involving failure modes in structural, heat transfer and fluid flow disciplines.

Consider a non-spherical elephant: computational fluid dynamics simulations of heat transfer coefficients and drag verified using wind tunnel experiments.

PubMed

Dudley, Peter N; Bonazza, Riccardo; Porter, Warren P

2013-07-01

Animal momentum and heat transfer analysis has historically used direct animal measurements or approximations to calculate drag and heat transfer coefficients. Research can now use modern 3D rendering and computational fluid dynamics software to simulate animal-fluid interactions. Key questions are the level of agreement between simulations and experiments and how superior they are to classical approximations. In this paper we compared experimental and simulated heat transfer and drag calculations on a scale model solid aluminum African elephant casting. We found good agreement between experimental and simulated data and large differences from classical approximations. We used the simulation results to calculate coefficients for heat transfer and drag of the elephant geometry. Copyright © 2013 Wiley Periodicals, Inc.

CFD Based Computations of Flexible Helicopter Blades for Stability Analysis

NASA Technical Reports Server (NTRS)

Guruswamy, Guru P.

2011-01-01

As a collaborative effort among government aerospace research laboratories an advanced version of a widely used computational fluid dynamics code, OVERFLOW, was recently released. This latest version includes additions to model flexible rotating multiple blades. In this paper, the OVERFLOW code is applied to improve the accuracy of airload computations from the linear lifting line theory that uses displacements from beam model. Data transfers required at every revolution are managed through a Unix based script that runs jobs on large super-cluster computers. Results are demonstrated for the 4-bladed UH-60A helicopter. Deviations of computed data from flight data are evaluated. Fourier analysis post-processing that is suitable for aeroelastic stability computations are performed.

On the role of fluids in stick-slip dynamics of saturated granular fault gouge using a coupled computational fluid dynamics-discrete element approach: STICK-SLIP IN SATURATED FAULT GOUGE

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

Dorostkar, Omid; Guyer, Robert A.; Johnson, Paul A.

The presence of fault gouge has considerable influence on slip properties of tectonic faults and the physics of earthquake rupture. The presence of fluids within faults also plays a significant role in faulting and earthquake processes. In this study, we present 3-D discrete element simulations of dry and fluid-saturated granular fault gouge and analyze the effect of fluids on stick-slip behavior. Fluid flow is modeled using computational fluid dynamics based on the Navier-Stokes equations for an incompressible fluid and modified to take into account the presence of particles. Analysis of a long time train of slip events shows that themore » (1) drop in shear stress, (2) compaction of granular layer, and (3) the kinetic energy release during slip all increase in magnitude in the presence of an incompressible fluid, compared to dry conditions. We also observe that on average, the recurrence interval between slip events is longer for fluid-saturated granular fault gouge compared to the dry case. This observation is consistent with the occurrence of larger events in the presence of fluid. It is found that the increase in kinetic energy during slip events for saturated conditions can be attributed to the increased fluid flow during slip. Finally, our observations emphasize the important role that fluid flow and fluid-particle interactions play in tectonic fault zones and show in particular how discrete element method (DEM) models can help understand the hydromechanical processes that dictate fault slip.« less

On the role of fluids in stick-slip dynamics of saturated granular fault gouge using a coupled computational fluid dynamics-discrete element approach: STICK-SLIP IN SATURATED FAULT GOUGE

DOE PAGES

Dorostkar, Omid; Guyer, Robert A.; Johnson, Paul A.; ...

2017-05-01

The presence of fault gouge has considerable influence on slip properties of tectonic faults and the physics of earthquake rupture. The presence of fluids within faults also plays a significant role in faulting and earthquake processes. In this study, we present 3-D discrete element simulations of dry and fluid-saturated granular fault gouge and analyze the effect of fluids on stick-slip behavior. Fluid flow is modeled using computational fluid dynamics based on the Navier-Stokes equations for an incompressible fluid and modified to take into account the presence of particles. Analysis of a long time train of slip events shows that themore » (1) drop in shear stress, (2) compaction of granular layer, and (3) the kinetic energy release during slip all increase in magnitude in the presence of an incompressible fluid, compared to dry conditions. We also observe that on average, the recurrence interval between slip events is longer for fluid-saturated granular fault gouge compared to the dry case. This observation is consistent with the occurrence of larger events in the presence of fluid. It is found that the increase in kinetic energy during slip events for saturated conditions can be attributed to the increased fluid flow during slip. Finally, our observations emphasize the important role that fluid flow and fluid-particle interactions play in tectonic fault zones and show in particular how discrete element method (DEM) models can help understand the hydromechanical processes that dictate fault slip.« less

Seismic low-frequency-based calculation of reservoir fluid mobility and its applications

NASA Astrophysics Data System (ADS)

Chen, Xue-Hua; He, Zhen-Hua; Zhu, Si-Xin; Liu, Wei; Zhong, Wen-Li

2012-06-01

Low frequency content of seismic signals contains information related to the reservoir fluid mobility. Based on the asymptotic analysis theory of frequency-dependent reflectivity from a fluid-saturated poroelastic medium, we derive the computational implementation of reservoir fluid mobility and present the determination of optimal frequency in the implementation. We then calculate the reservoir fluid mobility using the optimal frequency instantaneous spectra at the low-frequency end of the seismic spectrum. The methodology is applied to synthetic seismic data from a permeable gas-bearing reservoir model and real land and marine seismic data. The results demonstrate that the fluid mobility shows excellent quality in imaging the gas reservoirs. It is feasible to detect the location and spatial distribution of gas reservoirs and reduce the non-uniqueness and uncertainty in fluid identification.

Software for Analyzing Sequences of Flow-Related Images

NASA Technical Reports Server (NTRS)

Klimek, Robert; Wright, Ted

2004-01-01

Spotlight is a computer program for analysis of sequences of images generated in combustion and fluid physics experiments. Spotlight can perform analysis of a single image in an interactive mode or a sequence of images in an automated fashion. The primary type of analysis is tracking of positions of objects over sequences of frames. Features and objects that are typically tracked include flame fronts, particles, droplets, and fluid interfaces. Spotlight automates the analysis of object parameters, such as centroid position, velocity, acceleration, size, shape, intensity, and color. Images can be processed to enhance them before statistical and measurement operations are performed. An unlimited number of objects can be analyzed simultaneously. Spotlight saves results of analyses in a text file that can be exported to other programs for graphing or further analysis. Spotlight is a graphical-user-interface-based program that at present can be executed on Microsoft Windows and Linux operating systems. A version that runs on Macintosh computers is being considered.

SRM Internal Flow Test and Computational Fluid Dynamic Analysis. Volume 1; Major Task Summaries

NASA Technical Reports Server (NTRS)

Whitesides, R. Harold; Dill, Richard A.; Purinton, David C.

1995-01-01

During the four year period of performance for NASA contract, NASB-39095, ERC has performed a wide variety of tasks to support the design and continued development of new and existing solid rocket motors and the resolution of operational problems associated with existing solid rocket motor's at NASA MSFC. This report summarizes the support provided to NASA MSFC during the contractual period of performance. The report is divided into three main sections. The first section presents summaries for the major tasks performed. These tasks are grouped into three major categories: full scale motor analysis, subscale motor analysis and cold flow analysis. The second section includes summaries describing the computational fluid dynamics (CFD) tasks performed. The third section, the appendices of the report, presents detailed descriptions of the analysis efforts as well as published papers, memoranda and final reports associated with specific tasks. These appendices are referenced in the summaries. The subsection numbers for the three sections correspond to the same topics for direct cross referencing.

Multiple shooting shadowing for sensitivity analysis of chaotic dynamical systems

NASA Astrophysics Data System (ADS)

Blonigan, Patrick J.; Wang, Qiqi

2018-02-01

Sensitivity analysis methods are important tools for research and design with simulations. Many important simulations exhibit chaotic dynamics, including scale-resolving turbulent fluid flow simulations. Unfortunately, conventional sensitivity analysis methods are unable to compute useful gradient information for long-time-averaged quantities in chaotic dynamical systems. Sensitivity analysis with least squares shadowing (LSS) can compute useful gradient information for a number of chaotic systems, including simulations of chaotic vortex shedding and homogeneous isotropic turbulence. However, this gradient information comes at a very high computational cost. This paper presents multiple shooting shadowing (MSS), a more computationally efficient shadowing approach than the original LSS approach. Through an analysis of the convergence rate of MSS, it is shown that MSS can have lower memory usage and run time than LSS.

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.

Program Aids Design Of Fluid-Circulating Systems

NASA Technical Reports Server (NTRS)

Bacskay, Allen; Dalee, Robert

1992-01-01

Computer Aided Systems Engineering and Analysis (CASE/A) program is interactive software tool for trade study and analysis, designed to increase productivity during all phases of systems engineering. Graphics-based command-driven software package provides user-friendly computing environment in which engineer analyzes performance and interface characteristics of ECLS/ATC system. Useful during all phases of spacecraft-design program, from initial conceptual design trade studies to actual flight, including pre-flight prediction and in-flight analysis of anomalies. Written in FORTRAN 77.

Automating the parallel processing of fluid and structural dynamics calculations

NASA Technical Reports Server (NTRS)

Arpasi, Dale J.; Cole, Gary L.

1987-01-01

The NASA Lewis Research Center is actively involved in the development of expert system technology to assist users in applying parallel processing to computational fluid and structural dynamic analysis. The goal of this effort is to eliminate the necessity for the physical scientist to become a computer scientist in order to effectively use the computer as a research tool. Programming and operating software utilities have previously been developed to solve systems of ordinary nonlinear differential equations on parallel scalar processors. Current efforts are aimed at extending these capabilities to systems of partial differential equations, that describe the complex behavior of fluids and structures within aerospace propulsion systems. This paper presents some important considerations in the redesign, in particular, the need for algorithms and software utilities that can automatically identify data flow patterns in the application program and partition and allocate calculations to the parallel processors. A library-oriented multiprocessing concept for integrating the hardware and software functions is described.

Computational fluid dynamics analysis of SSME phase 2 and phase 2+ preburner injector element hydrogen flow paths

NASA Technical Reports Server (NTRS)

Ruf, Joseph H.

1992-01-01

Phase 2+ Space Shuttle Main Engine powerheads, E0209 and E0215 degraded their main combustion chamber (MCC) liners at a faster rate than is normal for phase 2 powerheads. One possible cause of the accelerated degradation was a reduction of coolant flow through the MCC. Hardware changes were made to the preburner fuel leg which may have reduced the resistance and, therefore, pulled some of the hydrogen from the MCC coolant leg. A computational fluid dynamics (CFD) analysis was performed to determine hydrogen flow path resistances of the phase 2+ fuel preburner injector elements relative to the phase 2 element. FDNS was implemented on axisymmetric grids with the hydrogen assumed to be incompressible. The analysis was performed in two steps: the first isolated the effect of the different inlet areas and the second modeled the entire injector element hydrogen flow path.

Computational fluid dynamics of airfoils and wings

NASA Technical Reports Server (NTRS)

Garabedian, P.; Mcfadden, G.

1982-01-01

It is pointed out that transonic flow is one of the fields where computational fluid dynamics turns out to be most effective. Codes for the design and analysis of supercritical airfoils and wings have become standard tools of the aircraft industry. The present investigation is concerned with mathematical models and theorems which account for some of the progress that has been made. The most successful aerodynamics codes are those for the analysis of flow at off-design conditions where weak shock waves appear. A major breakthrough was achieved by Murman and Cole (1971), who conceived of a retarded difference scheme which incorporates artificial viscosity to capture shocks in the supersonic zone. This concept has been used to develop codes for the analysis of transonic flow past a swept wing. Attention is given to the trailing edge and the boundary layer, entropy inequalities and wave drag, shockless airfoils, and the inverse swept wing code.

Computational Fluid Dynamics Analysis of Nozzle in Abrasive Water Jet Machining

NASA Astrophysics Data System (ADS)

Venugopal, S.; Chandresekaran, M.; Muthuraman, V.; Sathish, S.

2017-03-01

Abrasive water jet cutting is one of the most recently developed non-traditional manufacturing technologies. The general nature of flow through the machining, results in rapid wear of the nozzle which decrease the cutting performance. It is well known that the inlet pressure of the abrasive water suspension has main effect on the erosion characteristics of the inner surface of the nozzle. The objective of the project is to analyze the effect of inlet pressure on wall shear and exit kinetic energy. The analysis would be carried out by varying the inlet pressure of the nozzle, so as to obtain optimized process parameters for minimum nozzle wear. The two phase flow analysis would be carried by using computational fluid dynamics tool CFX. The availability of minimized process parameters such as of abrasive water jet machining (AWJM) is limited to water and experimental test can be cost prohibitive.

Coupled Finite Volume and Finite Element Method Analysis of a Complex Large-Span Roof Structure

NASA Astrophysics Data System (ADS)

Szafran, J.; Juszczyk, K.; Kamiński, M.

2017-12-01

The main goal of this paper is to present coupled Computational Fluid Dynamics and structural analysis for the precise determination of wind impact on internal forces and deformations of structural elements of a longspan roof structure. The Finite Volume Method (FVM) serves for a solution of the fluid flow problem to model the air flow around the structure, whose results are applied in turn as the boundary tractions in the Finite Element Method problem structural solution for the linear elastostatics with small deformations. The first part is carried out with the use of ANSYS 15.0 computer system, whereas the FEM system Robot supports stress analysis in particular roof members. A comparison of the wind pressure distribution throughout the roof surface shows some differences with respect to that available in the engineering designing codes like Eurocode, which deserves separate further numerical studies. Coupling of these two separate numerical techniques appears to be promising in view of future computational models of stochastic nature in large scale structural systems due to the stochastic perturbation method.

Concurrent extensions to the FORTRAN language for parallel programming of computational fluid dynamics algorithms

NASA Technical Reports Server (NTRS)

Weeks, Cindy Lou

1986-01-01

Experiments were conducted at NASA Ames Research Center to define multi-tasking software requirements for multiple-instruction, multiple-data stream (MIMD) computer architectures. The focus was on specifying solutions for algorithms in the field of computational fluid dynamics (CFD). The program objectives were to allow researchers to produce usable parallel application software as soon as possible after acquiring MIMD computer equipment, to provide researchers with an easy-to-learn and easy-to-use parallel software language which could be implemented on several different MIMD machines, and to enable researchers to list preferred design specifications for future MIMD computer architectures. Analysis of CFD algorithms indicated that extensions of an existing programming language, adaptable to new computer architectures, provided the best solution to meeting program objectives. The CoFORTRAN Language was written in response to these objectives and to provide researchers a means to experiment with parallel software solutions to CFD algorithms on machines with parallel architectures.

An evaluation of Computational Fluid dynamics model for flood risk analysis

NASA Astrophysics Data System (ADS)

Di Francesco, Silvia; Biscarini, Chiara; Montesarchio, Valeria

2014-05-01

This work presents an analysis of the hydrological-hydraulic engineering requisites for Risk evaluation and efficient flood damage reduction plans. Most of the research efforts have been dedicated to the scientific and technical aspects of risk assessment, providing estimates of possible alternatives and of the risk associated. In the decision making process for mitigation plan, the contribute of scientist is crucial, due to the fact that Risk-Damage analysis is based on evaluation of flow field ,of Hydraulic Risk and on economical and societal considerations. The present paper will focus on the first part of process, the mathematical modelling of flood events which is the base for all further considerations. The evaluation of potential catastrophic damage consequent to a flood event and in particular to dam failure requires modelling of the flood with sufficient detail so to capture the spatial and temporal evolutions of the event, as well of the velocity field. Thus, the selection of an appropriate mathematical model to correctly simulate flood routing is an essential step. In this work we present the application of two 3D Computational fluid dynamics models to a synthetic and real case study in order to evaluate the correct evolution of flow field and the associated flood Risk . The first model is based on a opensource CFD platform called openFoam. Water flow is schematized with a classical continuum approach based on Navier-Stokes equation coupled with Volume of fluid (VOF) method to take in account the multiphase character of river bottom-water- air systems. The second model instead is based on the Lattice Boltzmann method, an innovative numerical fluid dynamics scheme based on Boltzmann's kinetic equation that represents the flow dynamics at the macroscopic level by incorporating a microscopic kinetic approach. Fluid is seen as composed by particles that can move and collide among them. Simulation results from both models are promising and congruent to experimental results available in literature, thought the LBM model requires less computational effort respect to the NS one.

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.

Proper Orthogonal Decomposition in Optimal Control of Fluids

NASA Technical Reports Server (NTRS)

Ravindran, S. S.

1999-01-01

In this article, we present a reduced order modeling approach suitable for active control of fluid dynamical systems based on proper orthogonal decomposition (POD). The rationale behind the reduced order modeling is that numerical simulation of Navier-Stokes equations is still too costly for the purpose of optimization and control of unsteady flows. We examine the possibility of obtaining reduced order models that reduce computational complexity associated with the Navier-Stokes equations while capturing the essential dynamics by using the POD. The POD allows extraction of certain optimal set of basis functions, perhaps few, from a computational or experimental data-base through an eigenvalue analysis. The solution is then obtained as a linear combination of these optimal set of basis functions by means of Galerkin projection. This makes it attractive for optimal control and estimation of systems governed by partial differential equations. We here use it in active control of fluid flows governed by the Navier-Stokes equations. We show that the resulting reduced order model can be very efficient for the computations of optimization and control problems in unsteady flows. Finally, implementational issues and numerical experiments are presented for simulations and optimal control of fluid flow through channels.

TAP 1: A Finite Element Program for Steady-State Thermal Analysis of Convectively Cooled Structures

NASA Technical Reports Server (NTRS)

Thornton, E. A.

1976-01-01

The program has a finite element library of six elements: two conduction/convection elements to model heat transfer in a solid, two convection elements to model heat transfer in a fluid, and two integrated conduction/convection elements to represent combined heat transfer in tubular and plate/fin fluid passages. Nonlinear thermal analysis due to temperature dependent thermal parameters is performed using the Newton-Raphson iteration method. Program output includes nodal temperatures and element heat fluxes. Pressure drops in fluid passages may be computed as an option. A companion plotting program for displaying the finite element model and predicted temperature distributions is presented. User instructions and sample problems are presented in appendixes.

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.

Multi-component fluid flow through porous media by interacting lattice gas computer simulation

NASA Astrophysics Data System (ADS)

Cueva-Parra, Luis Alberto

In this work we study structural and transport properties such as power-law behavior of trajectory of each constituent and their center of mass, density profile, mass flux, permeability, velocity profile, phase separation, segregation, and mixing of miscible and immiscible multicomponent fluid flow through rigid and non-consolidated porous media. The considered parameters are the mass ratio of the components, temperature, external pressure, and porosity. Due to its solid theoretical foundation and computational simplicity, the selected approaches are the Interacting Lattice Gas with Monte Carlo Method (Metropolis Algorithm) and direct sampling, combined with particular collision rules. The percolation mechanism is used for modeling initial random porous media. The introduced collision rules allow to model non-consolidated porous media, because part of the kinetic energy of the fluid particles is transfered to barrier particles, which are the components of the porous medium. Having gained kinetic energy, the barrier particles can move. A number of interesting results are observed. Some findings include, (i) phase separation in immiscible fluid flow through a medium with no barrier particles (porosity p P = 1). (ii) For the flow of miscible fluids through rigid porous medium with porosity close to percolation threshold (p C), the flux density (measure of permeability) shows a power law increase ∝ (pC - p) mu with mu = 2.0, and the density profile is found to decay with height ∝ exp(-mA/Bh), consistent with the barometric height law. (iii) Sedimentation and driving of barrier particles in fluid flow through non-consolidated porous medium. This study involves developing computer simulation models with efficient serial and parallel codes, extensive data analysis via graphical utilities, and computer visualization techniques.

Numerical analysis of laminar and turbulent incompressible flows using the finite element Fluid Dynamics Analysis Package (FIDAP)

NASA Technical Reports Server (NTRS)

Sohn, Jeong L.

1988-01-01

The purpose of the study is the evaluation of the numerical accuracy of FIDAP (Fluid Dynamics Analysis Package). Accordingly, four test problems in laminar and turbulent incompressible flows are selected and the computational results of these problems compared with other numerical solutions and/or experimental data. These problems include: (1) 2-D laminar flow inside a wall-driven cavity; (2) 2-D laminar flow over a backward-facing step; (3) 2-D turbulent flow over a backward-facing step; and (4) 2-D turbulent flow through a turn-around duct.

A magnetic fluid seal for rotary blood pumps: Behaviors of magnetic fluids in a magnetic fluid seal.

PubMed

Mitamura, Yoshinori; Yano, Tetsuya; Nakamura, Wataru; Okamoto, Eiji

2013-01-01

A magnetic fluid (MF) seal has excellent durability. The performance of an MF seal, however, has been reported to decrease in liquids (several days). We have developed an MF seal that has a shield mechanism. The seal was perfect for 275 days in water. To investigate the effect of a shield, behaviors of MFs in a seal in water were studied both experimentally and computationally. (a) Two kinds of MF seals, one with a shield and one without a shield, were installed in a centrifugal pump. Behaviors of MFs in the seals in water were observed with a video camera and high-speed microscope. In the seal without a shield, the surface of the water in the seal waved and the turbulent flow affected behaviors of the MFs. In contrast, MFs rotated stably in the seal with a shield in water even at high rotational speeds. (b) Computational fluid dynamics analysis revealed that a stationary secondary flow pattern in the seal and small velocity difference between magnetic fluid and water at the interface. These MF behaviors prolonged the life of an MF seal in water.

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.

Overview of ICE Project: Integration of Computational Fluid Dynamics and Experiments

NASA Technical Reports Server (NTRS)

Stegeman, James D.; Blech, Richard A.; Babrauckas, Theresa L.; Jones, William H.

2001-01-01

Researchers at the NASA Glenn Research Center have developed a prototype integrated environment for interactively exploring, analyzing, and validating information from computational fluid dynamics (CFD) computations and experiments. The Integrated CFD and Experiments (ICE) project is a first attempt at providing a researcher with a common user interface for control, manipulation, analysis, and data storage for both experiments and simulation. ICE can be used as a live, on-tine system that displays and archives data as they are gathered; as a postprocessing system for dataset manipulation and analysis; and as a control interface or "steering mechanism" for simulation codes while visualizing the results. Although the full capabilities of ICE have not been completely demonstrated, this report documents the current system. Various applications of ICE are discussed: a low-speed compressor, a supersonic inlet, real-time data visualization, and a parallel-processing simulation code interface. A detailed data model for the compressor application is included in the appendix.

Impact of fluid-structure interaction on direct tumor-targeting in a representative hepatic artery system.

PubMed

Childress, Emily M; Kleinstreuer, Clement

2014-03-01

Direct targeting of solid tumors with chemotherapeutic drugs and/or radioactive microspheres can be a treatment option which minimizes side-effects and reduces cost. Briefly, computational analysis generates particle release maps (PRMs) which visually link upstream particle injection regions in the main artery with associated exit branches, some connected to tumors. The overall goal is to compute patient-specific PRMs realistically, accurately, and cost-effectively, which determines the suitable radial placement of a micro-catheter for optimal particle injection. Focusing in this paper on new steps towards realism and accuracy, the impact of fluid-structure interaction on direct drug-targeting is evaluated, using a representative hepatic artery system with liver tumor as a test bed. Specifically, the effect of arterial wall motion was demonstrated by modeling a two-way fluid-structure interaction analysis with Lagrangian particle tracking in the bifurcating arterial system. Clearly, rapid computational evaluation of optimal catheter location for tumor-targeting in a clinical application is very important. Hence, rigid-wall cases were also compared to the flexible scenario to establish whether PRMs generated when based on simplifying assumptions could provide adequate guidance towards ideal catheter placement. It was found that the best rigid (i.e., time-averaged) geometry is the physiological one that occurs during the diastolic targeting interval.

Numerical simulation of water evaporation inside vertical circular tubes

NASA Astrophysics Data System (ADS)

Ocłoń, Paweł; Nowak, Marzena; Majewski, Karol

2013-10-01

In this paper the results of simplified numerical analysis of water evaporation in vertical circular tubes are presented. The heat transfer in fluid domain (water or wet steam) and solid domain (tube wall) is analyzed. For the fluid domain the temperature field is calculated solving energy equation using the Control Volume Method and for the solid domain using the Finite Element Method. The heat transfer between fluid and solid domains is conjugated using the value of heat transfer coefficient from evaporating liquid to the tube wall. It is determined using the analytical Steiner-Taborek correlation. The pressure changes in fluid are computed using Friedel model.

ICASE semiannual report, April 1 - September 30, 1989

NASA Technical Reports Server (NTRS)

1990-01-01

The Institute conducts unclassified basic research in applied mathematics, numerical analysis, and computer science in order to extend and improve problem-solving capabilities in science and engineering, particularly in aeronautics and space. The major categories of the current Institute for Computer Applications in Science and Engineering (ICASE) research program are: (1) numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; (2) control and parameter identification problems, with emphasis on effective numerical methods; (3) computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and (4) computer systems and software, especially vector and parallel computers. ICASE reports are considered to be primarily preprints of manuscripts that have been submitted to appropriate research journals or that are to appear in conference proceedings.

The application of CAD, CAE & CAM in development of butterfly valve’s disc

NASA Astrophysics Data System (ADS)

Asiff Razif Shah Ranjit, Muhammad; Hanie Abdullah, Nazlin

2017-06-01

The improved design of a butterfly valve disc is based on the concept of sandwich theory. Butterfly valves are mostly used in various industries such as oil and gas plant. The primary failure modes for valves are indented disc, keyways and shaft failure and the cavitation damage. Emphasis on the application of CAD, a new model of the butterfly valve’s disc structure was designed. The structure analysis was analysed using the finite element analysis. Butterfly valve performance factors can be obtained is by using Computational Fluid Dynamics (CFD) software to simulate the physics of fluid flow in a piping system around a butterfly valve. A comparison analysis was done using the finite element to justify the performance of the structure. The second application of CAE is the computational fluid flow analysis. The upstream pressure and the downstream pressure was analysed to calculate the cavitation index and determine the performance throughout each opening position of the valve. The CAM process was done using 3D printer to produce a prototype and analysed the structure in form of prototype. The structure was downscale fabricated based on the model designed initially through the application of CAD. This study is utilized the application of CAD, CAE and CAM for a better improvement of the butterfly valve’s disc components.

Multi-fluid CFD analysis in Process Engineering

NASA Astrophysics Data System (ADS)

Hjertager, B. H.

2017-12-01

An overview of modelling and simulation of flow processes in gas/particle and gas/liquid systems are presented. Particular emphasis is given to computational fluid dynamics (CFD) models that use the multi-dimensional multi-fluid techniques. Turbulence modelling strategies for gas/particle flows based on the kinetic theory for granular flows are given. Sub models for the interfacial transfer processes and chemical kinetics modelling are presented. Examples are shown for some gas/particle systems including flow and chemical reaction in risers as well as gas/liquid systems including bubble columns and stirred tanks.

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.

Cumulative reports and publications through December 31, 1989

NASA Technical Reports Server (NTRS)

1990-01-01

A complete list of reports from the Institute for Computer Applications in Science and Engineering (ICASE) is presented. The major categories of the current ICASE research program are: numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; control and parameter identification problems, with emphasis on effectual numerical methods; computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, structural analysis, and chemistry; computer systems and software, especially vector and parallel computers, microcomputers, and data management. Since ICASE reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available.

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.

Bird impact analysis package for turbine engine fan blades

NASA Technical Reports Server (NTRS)

Hirschbein, M. S.

1982-01-01

A computer program has been developed to analyze the gross structural response of turbine engine fan blades subjected to bird strikes. The program couples a NASTRAN finite element model and modal analysis of a fan blade with a multi-mode bird impact analysis computer program. The impact analysis uses the NASTRAN blade model and a fluid jet model of the bird to interactively calculate blade loading during a bird strike event. The analysis package is computationaly efficient, easy to use and provides a comprehensive history of the gross structual blade response. Example cases are presented for a representative fan blade.

Computational Analysis of the Transonic Dynamics Tunnel Using FUN3D

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

Chwalowski, Pawel; Quon, Eliot; Brynildsen, Scott E.

This paper presents results from an explanatory two-year effort of applying Computational Fluid Dynamics (CFD) to analyze the empty-tunnel flow in the NASA Langley Research Center Transonic Dynamics Tunnel (TDT). The TDT is a continuous-flow, closed circuit, 16- x 16-foot slotted-test-section wind tunnel, with capabilities to use air or heavy gas as a working fluid. In this study, experimental data acquired in the empty tunnel using the R-134a test medium was used to calibrate the computational data. The experimental calibration data includes wall pressures, boundary-layer profiles, and the tunnel centerline Mach number profiles. Subsonic and supersonic flow regimes were considered,more » focusing on Mach 0.5, 0.7 and Mach 1.1 in the TDT test section. This study discusses the computational domain, boundary conditions, and initial conditions selected in the resulting steady-state analyses using NASA's FUN3D CFD software.« less

Computational Analysis of the Transonic Dynamics Tunnel Using FUN3D

NASA Technical Reports Server (NTRS)

Chwalowski, Pawel; Quon, Eliot; Brynildsen, Scott E.

2016-01-01

This paper presents results from an exploratory two-year effort of applying Computational Fluid Dynamics (CFD) to analyze the empty-tunnel flow in the NASA Langley Research Center Transonic Dynamics Tunnel (TDT). The TDT is a continuous-flow, closed circuit, 16- x 16-foot slotted-test-section wind tunnel, with capabilities to use air or heavy gas as a working fluid. In this study, experimental data acquired in the empty tunnel using the R-134a test medium was used to calibrate the computational data. The experimental calibration data includes wall pressures, boundary-layer profiles, and the tunnel centerline Mach number profiles. Subsonic and supersonic flow regimes were considered, focusing on Mach 0.5, 0.7 and Mach 1.1 in the TDT test section. This study discusses the computational domain, boundary conditions, and initial conditions selected and the resulting steady-state analyses using NASA's FUN3D CFD software.

Fluid Dynamic and Stability Analysis of a Thin Liquid Sheet

NASA Technical Reports Server (NTRS)

McMaster, Matthew S.

1992-01-01

Interest in thin sheet flows has recently been renewed due to their potential application in space radiators. Theoretical and experimental studies of the fluid dynamics and stability of thin liquid sheet flows have been carried out in this thesis. A computer program was developed to determine the cross-sectional shape of the edge cylinder given the cross-sectional area of the edge cylinder. A stability analysis was performed on a non-planer liquid sheet. A study was conducted to determine the effects of air resistance on the sheet.

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).

Lecture notes in economics and mathematical system. Volume 150: Supercritical wing sections 3

NASA Technical Reports Server (NTRS)

Bauer, F.; Garabedian, P.; Korn, D.

1977-01-01

Application of computational fluid dynamics to the design and analysis of supercritical wing sections is discussed. Computer programs used to study the flight of modern aircraft at high subsonic speeds are listed and described. The cascades of shockless transonic airfoils that are expected to increase the efficiency of compressors and turbines are included.

Cumulutive reports and publications through December 31, 1984

NASA Technical Reports Server (NTRS)

1985-01-01

A complete list of the Institute for Computer Applications in Science and Engineering (ICASE) Reports are given. Since ICASE Reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available. Topics include numerical methods, parameter identification, fluid dynamics, acoustics, structural analysis, and computers.

Flow induction by pressure forces

NASA Technical Reports Server (NTRS)

Garris, C. A.; Toh, K. H.; Amin, S.

1992-01-01

A dual experimental/computational approach to the fluid mechanics of complex interactions that take place in a rotary-jet ejector is presented. The long-range goal is to perform both detailed flow mapping and finite element computational analysis. The described work represents an initial finding on the experimental mapping program. Test results on the hubless rotary-jet are discussed.

Grid Generation for Multidisciplinary Design and Optimization of an Aerospace Vehicle: Issues and Challenges

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.

2000-01-01

The purpose of this paper is to discuss grid generation issues and to challenge the grid generation community to develop tools suitable for automated multidisciplinary analysis and design optimization of aerospace vehicles. Special attention is given to the grid generation issues of computational fluid dynamics and computational structural mechanics disciplines.

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.

Energy balance and the composition of weight loss during prolonged space flight

NASA Technical Reports Server (NTRS)

Leonard, J. I.

1982-01-01

Integrated metabolic balance analysis, Skylab integrated metabolic balance analysis and computer simulation of fluid-electrolyte responses to zero-g, overall mission weight and tissue losses, energy balance, diet and exercise, continuous changes, electrolyte losses, caloric and exercise requirements, and body composition are discussed.

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.

Axisymmetric computational fluid dynamics analysis of a film/dump-cooled rocket nozzle plume

NASA Technical Reports Server (NTRS)

Tucker, P. K.; Warsi, S. A.

1993-01-01

Prediction of convective base heating rates for a new launch vehicle presents significant challenges to analysts concerned with base environments. The present effort seeks to augment classical base heating scaling techniques via a detailed investigation of the exhaust plume shear layer of a single H2/O2 Space Transportation Main Engine (STME). Use of fuel-rich turbine exhaust to cool the STME nozzle presented concerns regarding potential recirculation of these gases to the base region with attendant increase in the base heating rate. A pressure-based full Navier-Stokes computational fluid dynamics (CFD) code with finite rate chemistry is used to predict plumes for vehicle altitudes of 10 kft and 50 kft. Levels of combustible species within the plume shear layers are calculated in order to assess assumptions made in the base heating analysis.

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.

Simulation of a Canard in Fluid Flow Driven by a Piezoelectric Beam with a Software Control Loop

DTIC Science & Technology

2014-04-01

The canard is actuated by a piezoelectric beam that bends as voltage is applied. The voltage is controlled by a software subroutine that measures...Dynamic system Modeling Co-simulation Simulation Abaqus Finite element analysis (FEA) Finite element method (FEM) Computational...is unlimited. i CONTENTS Page Introduction 1 Model Description 1 Fluid Model 2 Structural Model 3 Control Subroutine 4 Results 4

Experimental and theoretical analysis of nanofluids based on high temperature-heat transfer fluid with enhanced thermal properties

NASA Astrophysics Data System (ADS)

Navas, Javier; Sánchez-Coronilla, Antonio; Martín, Elisa I.; Gómez-Villarejo, Roberto; Teruel, Miriam; Gallardo, Juan Jesús; Aguilar, Teresa; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; Martín-Calleja, Joaquín

2017-04-01

In this work, nanofluids were prepared using commercial Cu nanoparticles and a commercial high temperature-heat transfer Fluid (eutectic mixture of diphenyl oxide and biphenyl) as the base fluid, which is used in concentrating solar power (CSP) plants. Different properties such as density, viscosity, heat capacity and thermal conductivity were characterized. Nanofluids showed enhanced heat transfer efficiency. In detail, the incorporation of Cu nanoparticles led to an increase of the heat capacity up to 14%. Also, thermal conductivity was increased up to 13%. Finally, the performance of the nanofluids prepared increased up to 11% according to the Dittus-Boelter correlation. On the other hand, equilibrium molecular dynamics simulation was used to model the experimental nanofluid system studied. Thermodynamic properties such as heat capacity and thermal conductivity were calculated and the results were compared with experimental data. The analysis of the radial function distributions (RDFs) and the inspection of the spatial distribution functions (SDFs) indicate the important role that plays the metal-oxygen interaction in the system. Dynamic properties such as the diffusion coefficients of base fluid and nanofluid were computed according to Einstein relation by computing the mean square displacement (MSD). Supplementary online material is available in electronic form at http://www.epjap.org

Simultaneous Aerodynamic and Structural Design Optimization (SASDO) for a 3-D Wing

NASA Technical Reports Server (NTRS)

Gumbert, Clyde R.; Hou, Gene J.-W.; Newman, Perry A.

2001-01-01

The formulation and implementation of an optimization method called Simultaneous Aerodynamic and Structural Design Optimization (SASDO) is shown as an extension of the Simultaneous Aerodynamic Analysis and Design Optimization (SAADO) method. It is extended by the inclusion of structure element sizing parameters as design variables and Finite Element Method (FEM) analysis responses as constraints. The method aims to reduce the computational expense. incurred in performing shape and sizing optimization using state-of-the-art Computational Fluid Dynamics (CFD) flow analysis, FEM structural analysis and sensitivity analysis tools. SASDO is applied to a simple. isolated, 3-D wing in inviscid flow. Results show that the method finds the saine local optimum as a conventional optimization method with some reduction in the computational cost and without significant modifications; to the analysis tools.

Research Reports: 1988 NASA/ASEE Summer Faculty Fellowship Program

NASA Technical Reports Server (NTRS)

Freeman, L. Michael (Editor); Chappell, Charles R. (Editor); Cothran, Ernestine K. (Editor); Karr, Gerald R. (Editor)

1988-01-01

The basic objectives are to further the professional knowledge of qualified engineering and science faculty members; to stimulate an exchange of ideas between participants and NASA: to enrich and refresh the research and teaching activities of the participants' institutions; and to contribute to the research objectives of the NASA centers. Topics addressed include: cryogenics; thunderstorm simulation; computer techniques; computer assisted instruction; system analysis weather forecasting; rocket engine design; crystal growth; control systems design; turbine pumps for the Space Shuttle Main engine; electron mobility; heat transfer predictions; rotor dynamics; mathematical models; computational fluid dynamics; and structural analysis.

CAPRI: Using a Geometric Foundation for Computational Analysis and Design

NASA Technical Reports Server (NTRS)

Haimes, Robert

2002-01-01

CAPRI (Computational Analysis Programming Interface) is a software development tool intended to make computerized design, simulation and analysis faster and more efficient. The computational steps traditionally taken for most engineering analysis (Computational Fluid Dynamics (CFD), structural analysis, etc.) are: Surface Generation, usually by employing a Computer Aided Design (CAD) system; Grid Generation, preparing the volume for the simulation; Flow Solver, producing the results at the specified operational point; Post-processing Visualization, interactively attempting to understand the results. It should be noted that the structures problem is more tractable than CFD; there are fewer mesh topologies used and the grids are not as fine (this problem space does not have the length scaling issues of fluids). For CFD, these steps have worked well in the past for simple steady-state simulations at the expense of much user interaction. The data was transmitted between phases via files. In most cases, the output from a CAD system could go IGES files. The output from Grid Generators and Solvers do not really have standards though there are a couple of file formats that can be used for a subset of the gridding (i.e. PLOT3D) data formats and the upcoming CGNS). The user would have to patch up the data or translate from one format to another to move to the next step. Sometimes this could take days. Instead of the serial approach to analysis, CAPRI takes a geometry centric approach. CAPRI is a software building tool-kit that refers to two ideas: (1) A simplified, object-oriented, hierarchical view of a solid part integrating both geometry and topology definitions, and (2) programming access to this part or assembly and any attached data. The connection to the geometry is made through an Application Programming Interface (API) and not a file system.

77 FR 64834 - Computational Fluid Dynamics Best Practice Guidelines for Dry Cask Applications

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-23

... NUCLEAR REGULATORY COMMISSION [NRC-2012-0250] Computational Fluid Dynamics Best Practice... public comments on draft NUREG-2152, ``Computational Fluid Dynamics Best Practice Guidelines for Dry Cask... System (ADAMS): You may access publicly-available documents online in the NRC Library at http://www.nrc...

Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, part 1

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1992-01-01

Experimental and computational fluid dynamic activities in rocket propulsion were discussed. The workshop was an open meeting of government, industry, and academia. A broad number of topics were discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, part 2

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1992-01-01

Presented here are 59 abstracts and presentations and three invited presentations given at the Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion held at the George C. Marshall Space Flight Center, April 28-30, 1992. The purpose of the workshop is to discuss experimental and computational fluid dynamic activities in rocket propulsion. The workshop is an open meeting for government, industry, and academia. A broad number of topics are discussed, including a computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1993-01-01

Conference publication includes 79 abstracts and presentations and 3 invited presentations given at the Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion held at George C. Marshall Space Flight Center, April 20-22, 1993. The purpose of the workshop is to discuss experimental and computational fluid dynamic activities in rocket propulsion. The workshop is an open meeting for government, industry, and academia. A broad number of topics are discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, Part 1

NASA Technical Reports Server (NTRS)

Williams, Robert W. (Compiler)

1993-01-01

Conference publication includes 79 abstracts and presentations given at the Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion held at the George C. Marshall Space Flight Center, April 20-22, 1993. The purpose of this workshop is to discuss experimental and computational fluid dynamic activities in rocket propulsion. The workshop is an open meeting for government, industry, and academia. A broad number of topics are discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Physical aspects of computing the flow of a viscous fluid

NASA Technical Reports Server (NTRS)

Mehta, U. B.

1984-01-01

One of the main themes in fluid dynamics at present and in the future is going to be computational fluid dynamics with the primary focus on the determination of drag, flow separation, vortex flows, and unsteady flows. A computation of the flow of a viscous fluid requires an understanding and consideration of the physical aspects of the flow. This is done by identifying the flow regimes and the scales of fluid motion, and the sources of vorticity. Discussions of flow regimes deal with conditions of incompressibility, transitional and turbulent flows, Navier-Stokes and non-Navier-Stokes regimes, shock waves, and strain fields. Discussions of the scales of fluid motion consider transitional and turbulent flows, thin- and slender-shear layers, triple- and four-deck regions, viscous-inviscid interactions, shock waves, strain rates, and temporal scales. In addition, the significance and generation of vorticity are discussed. These physical aspects mainly guide computations of the flow of a viscous fluid.

Analysis of two-phase flow inter-subchannel mass and momentum exchanges by the two-fluid model approach

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

Ninokata, H.; Deguchi, A.; Kawahara, A.

1995-09-01

A new void drift model for the subchannel analysis method is presented for the thermohydraulics calculation of two-phase flows in rod bundles where the flow model uses a two-fluid formulation for the conservation of mass, momentum and energy. A void drift model is constructed based on the experimental data obtained in a geometrically simple inter-connected two circular channel test sections using air-water as working fluids. The void drift force is assumed to be an origin of void drift velocity components of the two-phase cross-flow in a gap area between two adjacent rods and to overcome the momentum exchanges at themore » phase interface and wall-fluid interface. This void drift force is implemented in the cross flow momentum equations. Computational results have been successfully compared to experimental data available including 3x3 rod bundle data.« less

Peristaltic transport of copper-water nanofluid saturating porous medium

NASA Astrophysics Data System (ADS)

Abbasi, F. M.; Hayat, T.; Ahmad, B.

2015-03-01

Prime goal of present study is to model the problem for peristaltic transport of copper-water nanofluid in an asymmetric channel. The fluid fills porous space. Analysis is carried out in the presence of mixed conviction, viscous dissipation and heat generation/absorption. Long wavelength and low Reynolds number approximations are utilized in problem formulation. Numerical computations are presented for the axial velocity, pressure gradient, streamlines, temperature and heat transfer rate at the boundary. Graphical analysis is carried out to examine the effects of sundry parameters on flow quantities of interest. Results revealed that the axial velocity of copper-water nanofluid decreases with an increase in the nanoparticle volume fraction. Copper nanoparticles prove effective coolant since they sufficiently reduce the fluid temperature and show increase in the heat transfer between the fluid and solid boundary. Moreover temperature of the fluid decreases by increasing the permeability of porous medium.

The Shock and Vibration Digest. Volume 7, Number 5, May 1975.

DTIC Science & Technology

Contents: Dynamic response of fluid-filled shells; News briefs; Short courses; Abstracts from the current literature -- (Analysis and design, computer programs, environments, phenomenology, experimentation, components, systems); Author index ; Literature review; Book reviews.

Probing Reliability of Transport Phenomena Based Heat Transfer and Fluid Flow Analysis in Autogeneous Fusion Welding Process

NASA Astrophysics Data System (ADS)

Bag, S.; de, A.

2010-09-01

The transport phenomena based heat transfer and fluid flow calculations in weld pool require a number of input parameters. Arc efficiency, effective thermal conductivity, and viscosity in weld pool are some of these parameters, values of which are rarely known and difficult to assign a priori based on the scientific principles alone. The present work reports a bi-directional three-dimensional (3-D) heat transfer and fluid flow model, which is integrated with a real number based genetic algorithm. The bi-directional feature of the integrated model allows the identification of the values of a required set of uncertain model input parameters and, next, the design of process parameters to achieve a target weld pool dimension. The computed values are validated with measured results in linear gas-tungsten-arc (GTA) weld samples. Furthermore, a novel methodology to estimate the overall reliability of the computed solutions is also presented.

Special issue of Computers and Fluids in honor of Cecil E. (Chuck) Leith

DOE PAGES

Zhou, Ye; Herring, Jackson

2017-05-12

Here, this special issue of Computers and Fluids is dedicated to Cecil E. (Chuck) Leith in honor of his research contributions, leadership in the areas of statistical fluid mechanics, computational fluid dynamics, and climate theory. Leith's contribution to these fields emerged from his interest in solving complex fluid flow problems--even those at high Mach numbers--in an era well before large scale supercomputing became the dominant mode of inquiry into these fields. Yet the issues raised and solved by his research effort are still of vital interest today.

Special issue of Computers and Fluids in honor of Cecil E. (Chuck) Leith

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

Zhou, Ye; Herring, Jackson

Here, this special issue of Computers and Fluids is dedicated to Cecil E. (Chuck) Leith in honor of his research contributions, leadership in the areas of statistical fluid mechanics, computational fluid dynamics, and climate theory. Leith's contribution to these fields emerged from his interest in solving complex fluid flow problems--even those at high Mach numbers--in an era well before large scale supercomputing became the dominant mode of inquiry into these fields. Yet the issues raised and solved by his research effort are still of vital interest today.

Computational Fluid Dynamics Analysis of High Injection Pressure Blended Biodiesel

NASA Astrophysics Data System (ADS)

Khalid, Amir; Jaat, Norrizam; Faisal Hushim, Mohd; Manshoor, Bukhari; Zaman, Izzuddin; Sapit, Azwan; Razali, Azahari

2017-08-01

Biodiesel have great potential for substitution with petrol fuel for the purpose of achieving clean energy production and emission reduction. Among the methods that can control the combustion properties, controlling of the fuel injection conditions is one of the successful methods. The purpose of this study is to investigate the effect of high injection pressure of biodiesel blends on spray characteristics using Computational Fluid Dynamics (CFD). Injection pressure was observed at 220 MPa, 250 MPa and 280 MPa. The ambient temperature was kept held at 1050 K and ambient pressure 8 MPa in order to simulate the effect of boost pressure or turbo charger during combustion process. Computational Fluid Dynamics were used to investigate the spray characteristics of biodiesel blends such as spray penetration length, spray angle and mixture formation of fuel-air mixing. The results shows that increases of injection pressure, wider spray angle is produced by biodiesel blends and diesel fuel. The injection pressure strongly affects the mixture formation, characteristics of fuel spray, longer spray penetration length thus promotes the fuel and air mixing.

20 plus Years of Computational Fluid Dynamics for the Space Shuttle

NASA Technical Reports Server (NTRS)

Gomez, Reynaldo J., III

2011-01-01

This slide presentation reviews the use of computational fluid dynamics in performing analysis of the space shuttle with particular reference to the return to flight analysis and other shuttle problems. Slides show a comparison of pressure coefficient with the shuttle ascent configuration between the wind tunnel test and the computed values. the evolution of the grid system for the space shuttle launch vehicle (SSLv) from the early 80's to one in 2004, the grid configuration of the bipod ramp redesign from the original design to the current configuration, charts with the computations showing solid rocket booster surface pressures from wind tunnel data, calculated over two grid systems (i.e., the original 14 grid system, and the enhanced 113 grid system), and the computed flight orbiter wing loads are compared with strain gage data on STS-50 during flight. The loss of STS-107 initiated an unprecedented review of all external environments. The current SSLV grid system of 600+ grids, 1.8 Million surface points and 95+ million volume points is shown. The inflight entry analyses is shown, and the use of Overset CFD as a key part to many external tank redesign and debris assessments is discussed. The work that still remains to be accomplished for future shuttle flights is discussed.

Computational Fluid Dynamic (CFD) Study of an Articulating Turbine Blade Cascade

DTIC Science & Technology

2016-11-01

turbine blades to have fluid run through them during use1—a feature which many newer engines include. A cutaway view of a typical rotorcraft engine...ARL-TR-7871 ● NOV 2016 US Army Research Laboratory Computational Fluid Dynamic (CFD) Study of an Articulating Turbine Blade ...ARL-TR-7871 ● NOV 2016 US Army Research Laboratory Computational Fluid Dynamic (CFD) Study of an Articulating Turbine Blade Cascade by Luis

Simulating three dimensional wave run-up over breakwaters covered by antifer units

NASA Astrophysics Data System (ADS)

Najafi-Jilani, A.; Niri, M. Zakiri; Naderi, Nader

2014-06-01

The paper presents the numerical analysis of wave run-up over rubble-mound breakwaters covered by antifer units using a technique integrating Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD) software. Direct application of Navier-Stokes equations within armour blocks, is used to provide a more reliable approach to simulate wave run-up over breakwaters. A well-tested Reynolds-averaged Navier-Stokes (RANS) Volume of Fluid (VOF) code (Flow-3D) was adopted for CFD computations. The computed results were compared with experimental data to check the validity of the model. Numerical results showed that the direct three dimensional (3D) simulation method can deliver accurate results for wave run-up over rubble mound breakwaters. The results showed that the placement pattern of antifer units had a great impact on values of wave run-up so that by changing the placement pattern from regular to double pyramid can reduce the wave run-up by approximately 30%. Analysis was done to investigate the influences of surface roughness, energy dissipation in the pores of the armour layer and reduced wave run-up due to inflow into the armour and stone layer.

Comprehensive Benchmark Suite for Simulation of Particle Laden Flows Using the Discrete Element Method with Performance Profiles from the Multiphase Flow with Interface eXchanges (MFiX) Code

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

Liu, Peiyuan; Brown, Timothy; Fullmer, William D.

Five benchmark problems are developed and simulated with the computational fluid dynamics and discrete element model code MFiX. The benchmark problems span dilute and dense regimes, consider statistically homogeneous and inhomogeneous (both clusters and bubbles) particle concentrations and a range of particle and fluid dynamic computational loads. Several variations of the benchmark problems are also discussed to extend the computational phase space to cover granular (particles only), bidisperse and heat transfer cases. A weak scaling analysis is performed for each benchmark problem and, in most cases, the scalability of the code appears reasonable up to approx. 103 cores. Profiling ofmore » the benchmark problems indicate that the most substantial computational time is being spent on particle-particle force calculations, drag force calculations and interpolating between discrete particle and continuum fields. Hardware performance analysis was also carried out showing significant Level 2 cache miss ratios and a rather low degree of vectorization. These results are intended to serve as a baseline for future developments to the code as well as a preliminary indicator of where to best focus performance optimizations.« less

Extension of the ADjoint Approach to a Laminar Navier-Stokes Solver

NASA Astrophysics Data System (ADS)

Paige, Cody

The use of adjoint methods is common in computational fluid dynamics to reduce the cost of the sensitivity analysis in an optimization cycle. The forward mode ADjoint is a combination of an adjoint sensitivity analysis method with a forward mode automatic differentiation (AD) and is a modification of the reverse mode ADjoint method proposed by Mader et al.[1]. A colouring acceleration technique is presented to reduce the computational cost increase associated with forward mode AD. The forward mode AD facilitates the implementation of the laminar Navier-Stokes (NS) equations. The forward mode ADjoint method is applied to a three-dimensional computational fluid dynamics solver. The resulting Euler and viscous ADjoint sensitivities are compared to the reverse mode Euler ADjoint derivatives and a complex-step method to demonstrate the reduced computational cost and accuracy. Both comparisons demonstrate the benefits of the colouring method and the practicality of using a forward mode AD. [1] Mader, C.A., Martins, J.R.R.A., Alonso, J.J., and van der Weide, E. (2008) ADjoint: An approach for the rapid development of discrete adjoint solvers. AIAA Journal, 46(4):863-873. doi:10.2514/1.29123.

Multiphysics Nuclear Thermal Rocket Thrust Chamber Analysis

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2005-01-01

The objective of this effort is t o develop an efficient and accurate thermo-fluid computational methodology to predict environments for hypothetical thrust chamber design and analysis. The current task scope is to perform multidimensional, multiphysics analysis of thrust performance and heat transfer analysis for a hypothetical solid-core, nuclear thermal engine including thrust chamber and nozzle. The multiphysics aspects of the model include: real fluid dynamics, chemical reactivity, turbulent flow, and conjugate heat transfer. The model will be designed to identify thermal, fluid, and hydrogen environments in all flow paths and materials. This model would then be used to perform non- nuclear reproduction of the flow element failures demonstrated in the Rover/NERVA testing, investigate performance of specific configurations and assess potential issues and enhancements. A two-pronged approach will be employed in this effort: a detailed analysis of a multi-channel, flow-element, and global modeling of the entire thrust chamber assembly with a porosity modeling technique. It is expected that the detailed analysis of a single flow element would provide detailed fluid, thermal, and hydrogen environments for stress analysis, while the global thrust chamber assembly analysis would promote understanding of the effects of hydrogen dissociation and heat transfer on thrust performance. These modeling activities will be validated as much as possible by testing performed by other related efforts.

Noise optimization of a regenerative automotive fuel pump

NASA Astrophysics Data System (ADS)

Wang, J. F.; Feng, H. H.; Mou, X. L.; Huang, Y. X.

2017-03-01

The regenerative pump used in automotive is facing a noise problem. To understand the mechanism in detail, Computational Fluid Dynamics (CFD) and Computational Acoustic Analysis (CAA) together were used to understand the fluid and acoustic characteristics of the fuel pump using ANSYS-CFX 15.0 and LMS Virtual. Lab Rev12, respectively. The CFD model and acoustical model were validated by mass flow rate test and sound pressure test, respectively. Comparing the computational and experimental results shows that sound pressure levels at the observer position are consistent at high frequencies, especially at blade passing frequency. After validating the models, several numerical models were analyzed in the study for noise improvement. It is observed that for configuration having greater number of impeller blades, noise level was significantly improved at blade passing frequency, when compared to that of the original model.

An Integrated Model of the Cardiovascular and Central Nervous Systems for Analysis of Microgravity Induced Fluid Redistribution

NASA Technical Reports Server (NTRS)

Price, R.; Gady, S.; Heinemann, K.; Nelson, E. S.; Mulugeta, L.; Ethier, C. R.; Samuels, B. C.; Feola, A.; Vera, J.; Myers, J. G.

2015-01-01

A recognized side effect of prolonged microgravity exposure is visual impairment and intracranial pressure (VIIP) syndrome. The medical understanding of this phenomenon is at present preliminary, although it is hypothesized that the headward shift of bodily fluids in microgravity may be a contributor. Computational models can be used to provide insight into the origins of VIIP. In order to further investigate this phenomenon, NASAs Digital Astronaut Project (DAP) is developing an integrated computational model of the human body which is divided into the eye, the cerebrovascular system, and the cardiovascular system. This presentation will focus on the development and testing of the computational model of an integrated model of the cardiovascular system (CVS) and central nervous system (CNS) that simulates the behavior of pressures, volumes, and flows within these two physiological systems.

Tools for 3D scientific visualization in computational aerodynamics at NASA Ames Research Center

NASA Technical Reports Server (NTRS)

Bancroft, Gordon; Plessel, Todd; Merritt, Fergus; Watson, Val

1989-01-01

Hardware, software, and techniques used by the Fluid Dynamics Division (NASA) for performing visualization of computational aerodynamics, which can be applied to the visualization of flow fields from computer simulations of fluid dynamics about the Space Shuttle, are discussed. Three visualization techniques applied, post-processing, tracking, and steering, are described, as well as the post-processing software packages used, PLOT3D, SURF (Surface Modeller), GAS (Graphical Animation System), and FAST (Flow Analysis software Toolkit). Using post-processing methods a flow simulation was executed on a supercomputer and, after the simulation was complete, the results were processed for viewing. It is shown that the high-resolution, high-performance three-dimensional workstation combined with specially developed display and animation software provides a good tool for analyzing flow field solutions obtained from supercomputers.

Impact of composite plates: Analysis of stresses and forces

NASA Technical Reports Server (NTRS)

Moon, F. C.; Kim, B. S.; Fang-Landau, S. R.

1976-01-01

The foreign object damage resistance of composite fan blades was studied. Edge impact stresses in an anisotropic plate were first calculated incorporating a constrained layer damping model. It is shown that a very thin damping layer can dramatically decrease the maximum normal impact stresses. A multilayer model of a composite plate is then presented which allows computation of the interlaminar normal and shear stresses. Results are presented for the stresses due to a line impact load normal to the plane of a composite plate. It is shown that significant interlaminar tensile stresses can develop during impact. A computer code was developed for this problem using the fast Fourier transform. A marker and cell computer code were also used to investigate the hydrodynamic impact of a fluid slug against a wall or turbine blade. Application of fluid modeling of bird impact is reviewed.

Computing the Thermodynamic State of a Cryogenic Fluid

NASA Technical Reports Server (NTRS)

Willen, G. Scott; Hanna, Gregory J.; Anderson, Kevin R.

2005-01-01

The Cryogenic Tank Analysis Program (CTAP) predicts the time-varying thermodynamic state of a cryogenic fluid in a tank or a Dewar flask. CTAP is designed to be compatible with EASY5x, which is a commercial software package that can be used to simulate a variety of processes and equipment systems. The mathematical model implemented in CTAP is a first-order differential equation for the pressure as a function of time.

Computational Analysis of Effect of Transient Fluid Force on Composite Structures

DTIC Science & Technology

2013-12-01

as they well represent an E-glass fiber reinforced composite frequently used in research and industrial applications. The fluid domain was sized...provide unique perspectives on peak stress ratios . The two models both share increased structural rigidity. The cylinder is reinforced by... Poisson ratio of 0.3 and Young’s modulus of 20 GPa were added to the transient structural engineering data cell (Figure 69). 78 Figure 69. E-Glass

Fluid Stochastic Petri Nets: Theory, Applications, and Solution

NASA Technical Reports Server (NTRS)

Horton, Graham; Kulkarni, Vidyadhar G.; Nicol, David M.; Trivedi, Kishor S.

1996-01-01

In this paper we introduce a new class of stochastic Petri nets in which one or more places can hold fluid rather than discrete tokens. We define a class of fluid stochastic Petri nets in such a way that the discrete and continuous portions may affect each other. Following this definition we provide equations for their transient and steady-state behavior. We present several examples showing the utility of the construct in communication network modeling and reliability analysis, and discuss important special cases. We then discuss numerical methods for computing the transient behavior of such nets. Finally, some numerical examples are presented.

Computer animation challenges for computational fluid dynamics

NASA Astrophysics Data System (ADS)

Vines, Mauricio; Lee, Won-Sook; Mavriplis, Catherine

2012-07-01

Computer animation requirements differ from those of traditional computational fluid dynamics (CFD) investigations in that visual plausibility and rapid frame update rates trump physical accuracy. We present an overview of the main techniques for fluid simulation in computer animation, starting with Eulerian grid approaches, the Lattice Boltzmann method, Fourier transform techniques and Lagrangian particle introduction. Adaptive grid methods, precomputation of results for model reduction, parallelisation and computation on graphical processing units (GPUs) are reviewed in the context of accelerating simulation computations for animation. A survey of current specific approaches for the application of these techniques to the simulation of smoke, fire, water, bubbles, mixing, phase change and solid-fluid coupling is also included. Adding plausibility to results through particle introduction, turbulence detail and concentration on regions of interest by level set techniques has elevated the degree of accuracy and realism of recent animations. Basic approaches are described here. Techniques to control the simulation to produce a desired visual effect are also discussed. Finally, some references to rendering techniques and haptic applications are mentioned to provide the reader with a complete picture of the challenges of simulating fluids in computer animation.

Chaos analysis of viscoelastic chaotic flows of polymeric fluids in a micro-channel

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

Lim, C. P.; Lam, Y. C., E-mail: myclam@ntu.edu.sg; BioSystems and Micromechanics

2015-07-15

Many fluids, including biological fluids such as mucus and blood, are viscoelastic. Through the introduction of chaotic flows in a micro-channel and the construction of maps of characteristic chaos parameters, differences in viscoelastic properties of these fluids can be measured. This is demonstrated by creating viscoelastic chaotic flows induced in an H-shaped micro-channel through the steady infusion of a polymeric fluid of polyethylene oxide (PEO) and another immiscible fluid (silicone oil). A protocol for chaos analysis was established and demonstrated for the analysis of the chaotic flows generated by two polymeric fluids of different molecular weight but with similar relaxationmore » times. The flows were shown to be chaotic through the computation of their correlation dimension (D{sub 2}) and the largest Lyapunov exponent (λ{sub 1}), with D{sub 2} being fractional and λ{sub 1} being positive. Contour maps of D{sub 2} and λ{sub 1} of the respective fluids in the operating space, which is defined by the combination of polymeric fluids and silicone oil flow rates, were constructed to represent the characteristic of the chaotic flows generated. It was observed that, albeit being similar, the fluids have generally distinct characteristic maps with some similar trends. The differences in the D{sub 2} and λ{sub 1} maps are indicative of the difference in the molecular weight of the polymers in the fluids because the driving force of the viscoelastic chaotic flows is of molecular origin. This approach in constructing the characteristic maps of chaos parameters can be employed as a diagnostic tool for biological fluids and, more generally, chaotic signals.« less

Left ventricular fluid mechanics: the long way from theoretical models to clinical applications.

PubMed

Pedrizzetti, Gianni; Domenichini, Federico

2015-01-01

The flow inside the left ventricle is characterized by the formation of vortices that smoothly accompany blood from the mitral inlet to the aortic outlet. Computational fluid dynamics permitted to shed some light on the fundamental processes involved with vortex motion. More recently, patient-specific numerical simulations are becoming an increasingly feasible tool that can be integrated with the developing imaging technologies. The existing computational methods are reviewed in the perspective of their potential role as a novel aid for advanced clinical analysis. The current results obtained by simulation methods either alone or in combination with medical imaging are summarized. Open problems are highlighted and perspective clinical applications are discussed.

User's Manual for Thermal Analysis Program of Axially Grooved Heat Pipe (HTGAP)

NASA Technical Reports Server (NTRS)

Kamotani, Y.

1978-01-01

A computer program that numerically predicts the steady state temperature distribution inside an axially grooved heat pipe wall for a given groove geometry and working fluid under various heat input and output modes is described. The program computes both evaporator and condenser film coefficients. The program is able to handle both axisymmetric and nonaxisymmetric heat transfer cases. Non-axisymmetric heat transfer results either from non-uniform input at the evaporator or non-uniform heat removal from the condenser, or from both. The presence of a liquid pool in the condenser region under one-g condition also causes non-axisymmetric heat transfer, and its effect on the pipe wall temperature distribution is included in the present program. The hydrodynamic aspect of an axially grooved heat pipe is studied in the Groove Analysis Program (GAP). The present thermal analysis program assumes that the GAP program (or other similar programs) is run first so that the heat transport limit and optimum fluid charge of the heat pipe are known a priori.

Performance Analysis of Scientific and Engineering Applications Using MPInside and TAU

NASA Technical Reports Server (NTRS)

Saini, Subhash; Mehrotra, Piyush; Taylor, Kenichi Jun Haeng; Shende, Sameer Suresh; Biswas, Rupak

2010-01-01

In this paper, we present performance analysis of two NASA applications using performance tools like Tuning and Analysis Utilities (TAU) and SGI MPInside. MITgcmUV and OVERFLOW are two production-quality applications used extensively by scientists and engineers at NASA. MITgcmUV is a global ocean simulation model, developed by the Estimating the Circulation and Climate of the Ocean (ECCO) Consortium, for solving the fluid equations of motion using the hydrostatic approximation. OVERFLOW is a general-purpose Navier-Stokes solver for computational fluid dynamics (CFD) problems. Using these tools, we analyze the MPI functions (MPI_Sendrecv, MPI_Bcast, MPI_Reduce, MPI_Allreduce, MPI_Barrier, etc.) with respect to message size of each rank, time consumed by each function, and how ranks communicate. MPI communication is further analyzed by studying the performance of MPI functions used in these two applications as a function of message size and number of cores. Finally, we present the compute time, communication time, and I/O time as a function of the number of cores.

Implementation of Finite Volume based Navier Stokes Algorithm Within General Purpose Flow Network Code

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Majumdar, Alok

2012-01-01

This paper describes a finite volume based numerical algorithm that allows multi-dimensional computation of fluid flow within a system level network flow analysis. There are several thermo-fluid engineering problems where higher fidelity solutions are needed that are not within the capacity of system level codes. The proposed algorithm will allow NASA's Generalized Fluid System Simulation Program (GFSSP) to perform multi-dimensional flow calculation within the framework of GFSSP s typical system level flow network consisting of fluid nodes and branches. The paper presents several classical two-dimensional fluid dynamics problems that have been solved by GFSSP's multi-dimensional flow solver. The numerical solutions are compared with the analytical and benchmark solution of Poiseulle, Couette and flow in a driven cavity.

Energy Finite Element Analysis for Computing the High Frequency Vibration of the Aluminum Testbed Cylinder and Correlating the Results to Test Data

NASA Technical Reports Server (NTRS)

Vlahopoulos, Nickolas

2005-01-01

The Energy Finite Element Analysis (EFEA) is a finite element based computational method for high frequency vibration and acoustic analysis. The EFEA solves with finite elements governing differential equations for energy variables. These equations are developed from wave equations. Recently, an EFEA method for computing high frequency vibration of structures either in vacuum or in contact with a dense fluid has been presented. The presence of fluid loading has been considered through added mass and radiation damping. The EFEA developments were validated by comparing EFEA results to solutions obtained by very dense conventional finite element models and solutions from classical techniques such as statistical energy analysis (SEA) and the modal decomposition method for bodies of revolution. EFEA results have also been compared favorably with test data for the vibration and the radiated noise generated by a large scale submersible vehicle. The primary variable in EFEA is defined as the time averaged over a period and space averaged over a wavelength energy density. A joint matrix computed from the power transmission coefficients is utilized for coupling the energy density variables across any discontinuities, such as change of plate thickness, plate/stiffener junctions etc. When considering the high frequency vibration of a periodically stiffened plate or cylinder, the flexural wavelength is smaller than the interval length between two periodic stiffeners, therefore the stiffener stiffness can not be smeared by computing an equivalent rigidity for the plate or cylinder. The periodic stiffeners must be regarded as coupling components between periodic units. In this paper, Periodic Structure (PS) theory is utilized for computing the coupling joint matrix and for accounting for the periodicity characteristics.

Fluid-structure interaction analysis and lifetime estimation of a natural gas pipeline centrifugal compressor under near-choke and near-surge conditions

NASA Astrophysics Data System (ADS)

Ju, Yaping; Liu, Hui; Yao, Ziyun; Xing, Peng; Zhang, Chuhua

2015-11-01

Up to present, there have been no studies concerning the application of fluid-structure interaction (FSI) analysis to the lifetime estimation of multi-stage centrifugal compressors under dangerous unsteady aerodynamic excitations. In this paper, computational fluid dynamics (CFD) simulations of a three-stage natural gas pipeline centrifugal compressor are performed under near-choke and near-surge conditions, and the unsteady aerodynamic pressure acting on impeller blades are obtained. Then computational structural dynamics (CSD) analysis is conducted through a one-way coupling FSI model to predict alternating stresses in impeller blades. Finally, the compressor lifetime is estimated using the nominal stress approach. The FSI results show that the impellers of latter stages suffer larger fluctuation stresses but smaller mean stresses than those at preceding stages under near-choke and near-surge conditions. The most dangerous position in the compressor is found to be located near the leading edge of the last-stage impeller blade. Compressor lifetime estimation shows that the investigated compressor can run up to 102.7 h under the near-choke condition and 200.2 h under the near-surge condition. This study is expected to provide a scientific guidance for the operation safety of natural gas pipeline centrifugal compressors.

Development of a New Arterial-Line Filter Design Using Computational Fluid Dynamics Analysis

PubMed Central

Herbst, Daniel P.; Najm, Hani K.

2012-01-01

Abstract: Arterial-line filters used during extracorporeal circulation continue to rely on the physical properties of a wetted micropore and reductions in blood flow velocity to affect air separation from the circulating blood volume. Although problems associated with air embolism during cardiac surgery persist, a number of investigators have concluded that further improvements in filtration are needed to enhance air removal during cardiopulmonary bypass procedures. This article reviews theoretical principles of micropore filter technology and outlines the development of a new arterial-line filter concept using computational fluid dynamics analysis. Manufacturer-supplied data of a micropore screen and experimental results taken from an ex vivo test circuit were used to define the inputs needed for numerical modeling of a new filter design. Flow patterns, pressure distributions, and velocity profiles predicted with computational fluid dynamics softwarewere used to inform decisions on model refinements and how to achieve initial design goals of ≤225 mL prime volume and ≤500 cm2 of screen surface area. Predictions for optimal model geometry included a screen angle of 56° from the horizontal plane with a total surface area of 293.9 cm2 and a priming volume of 192.4 mL. This article describes in brief the developmental process used to advance a new filter design and supports the value of numerical modeling in this undertaking. PMID:23198394

Development of a new arterial-line filter design using computational fluid dynamics analysis.

PubMed

Herbst, Daniel P; Najm, Hani K

2012-09-01

Arterial-line filters used during extracorporeal circulation continue to rely on the physical properties of a wetted micropore and reductions in blood flow velocity to affect air separation from the circulating blood volume. Although problems associated with air embolism during cardiac surgery persist, a number of investigators have concluded that further improvements in filtration are needed to enhance air removal during cardiopulmonary bypass procedures. This article reviews theoretical principles of micropore filter technology and outlines the development of a new arterial-line filter concept using computational fluid dynamics analysis. Manufacturer-supplied data of a micropore screen and experimental results taken from an ex vivo test circuit were used to define the inputs needed for numerical modeling of a new filter design. Flow patterns, pressure distributions, and velocity profiles predicted with computational fluid dynamics software were used to inform decisions on model refinements and how to achieve initial design goals of < or = 225 mL prime volume and < or = 500 cm2 of screen surface area. Predictions for optimal model geometry included a screen angle of 56 degrees from the horizontal plane with a total surface area of 293.9 cm2 and a priming volume of 192.4 mL. This article describes in brief the developmental process used to advance a new filter design and supports the value of numerical modeling in this undertaking.

Thirteenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion and Launch Vehicle Technology. Volume 2

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1996-01-01

This conference publication includes various abstracts and presentations given at the 13th Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion and Launch Vehicle Technology held at the George C. Marshall Space Flight Center April 25-27 1995. The purpose of the workshop was to discuss experimental and computational fluid dynamic activities in rocket propulsion and launch vehicles. The workshop was an open meeting for government, industry, and academia. A broad number of topics were discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

A numerical comparison with an exact solution for the transient response of a cylinder immersed in a fluid. [computer simulated underwater tests to determine transient response of a submerged cylindrical shell

NASA Technical Reports Server (NTRS)

Giltrud, M. E.; Lucas, D. S.

1979-01-01

The transient response of an elastic cylindrical shell immersed in an acoustic media that is engulfed by a plane wave is determined numerically. The method applies to the USA-STAGS code which utilizes the finite element method for the structural analysis and the doubly asymptotic approximation for the fluid-structure interaction. The calculations are compared to an exact analysis for two separate loading cases: a plane step wave and an exponentially decaying plane wave.

Gesellschaft fuer angewandte Mathematik und Mechanik, Annual Scientific Meeting, Universitaet Regensburg, Regensburg, West Germany, April 16-19, 1984, Proceedings

NASA Astrophysics Data System (ADS)

Problems in applied mathematics and mechanics are addressed in reviews and reports. Areas covered are vibration and stability, elastic and plastic mechanics, fluid mechanics, the numerical treatment of differential equations (general theory and finite-element methods in particular), optimization, decision theory, stochastics, actuarial mathematics, applied analysis and mathematical physics, and numerical analysis. Included are major lectures on separated flows, the transition regime of rarefied-gas dynamics, recent results in nonlinear elasticity, fluid-elastic vibration, the new computer arithmetic, and unsteady wave propagation in layered elastic bodies.

Analysis of physical-chemical processes governing SSME internal fluid flows

NASA Technical Reports Server (NTRS)

Singhal, A. K.; Owens, S. F.; Mukerjee, T.; Keeton, L. W.; Prakash, C.; Przekwas, A. J.

1984-01-01

The efforts to adapt CHAM's computational fluid dynamics code, PHOENICS, to the analysis of flow within the high pressure fuel turbopump (HPFTP) aft-platform seal cavity of the SSME are summarized. In particular, the special purpose PHOENICS satellite and ground station specifically formulated for this application are listed and described, and the preliminary results of the first part two-dimensional analyses are presented and discussed. Planned three-dimensional analyses are also briefly outlined. To further understand the mixing and combustion processes in the SSME fuelside preburners, a single oxygen-hydrogen jet element was investigated.

Hydrodynamic design of generic pump components

NASA Technical Reports Server (NTRS)

Eastland, A. H. J.; Dodson, H. C.

1991-01-01

Inducer and impellar base geometries were defined for a fuel pump for a generic generator cycle. Blade surface data and inlet flowfield definition are available in sufficient detail to allow computational fluid dynamic analysis of the two components.

Simultaneous Aerodynamic Analysis and Design Optimization (SAADO) for a 3-D Flexible Wing

NASA Technical Reports Server (NTRS)

Gumbert, Clyde R.; Hou, Gene J.-W.

2001-01-01

The formulation and implementation of an optimization method called Simultaneous Aerodynamic Analysis and Design Optimization (SAADO) are extended from single discipline analysis (aerodynamics only) to multidisciplinary analysis - in this case, static aero-structural analysis - and applied to a simple 3-D wing problem. The method aims to reduce the computational expense incurred in performing shape optimization using state-of-the-art Computational Fluid Dynamics (CFD) flow analysis, Finite Element Method (FEM) structural analysis and sensitivity analysis tools. Results for this small problem show that the method reaches the same local optimum as conventional optimization. However, unlike its application to the win,, (single discipline analysis), the method. as I implemented here, may not show significant reduction in the computational cost. Similar reductions were seen in the two-design-variable (DV) problem results but not in the 8-DV results given here.

Aerodynamic Analysis of Morphing Blades

NASA Astrophysics Data System (ADS)

Harris, Caleb; Macphee, David; Carlisle, Madeline

2016-11-01

Interest in morphing blades has grown with applications for wind turbines and other aerodynamic blades. This passive control method has advantages over active control methods such as lower manufacturing and upkeep costs. This study has investigated the lift and drag forces on individual blades with experimental and computational analysis. The goal has been to show that these blades delay stall and provide larger lift-to-drag ratios at various angles of attack. Rigid and flexible airfoils were cast from polyurethane and silicone respectively, then lift and drag forces were collected from a load cell during 2-D testing in a wind tunnel. Experimental data was used to validate computational models in OpenFOAM. A finite volume fluid-structure-interaction solver was used to model the flexible blade in fluid flow. Preliminary results indicate delay in stall and larger lift-to-drag ratios by maintaining more optimal angles of attack when flexing. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.

Computational Fluid Dynamic Analysis of Enhancing Passenger Cabin Comfort Using PCM

NASA Astrophysics Data System (ADS)

Purusothaman, M.; Valarmathi, T. N.; Dada Mohammad, S. K.

2016-09-01

The main purpose of this study is to determine a cost effective way to enhance passenger cabin comfort by analyzing the effect of solar radiation of a open parked vehicle, which is exposed to constant solar radiation on a hot and sunny day. Maximum heat accumulation occurs in the car cabin due to the solar radiation. By means of computational fluid dynamics (CFD) analysis, a simulation process is conducted for the thermal regulation of the passenger cabin using a layer of phase change material (PCM) on the roof structure of a stationary car when exposed to ambient temperature on a hot sunny day. The heat energy accumulated in the passenger cabin is absorbed by a layer of PCM for phase change process. The installation of a ventilation system which uses an exhaust fan to create a natural convection scenario in the cabin is also considered to enhance passenger comfort along with PCM.

Principles of Biomimetic Vascular Network Design Applied to a Tissue-Engineered Liver Scaffold

PubMed Central

Hoganson, David M.; Pryor, Howard I.; Spool, Ira D.; Burns, Owen H.; Gilmore, J. Randall

2010-01-01

Branched vascular networks are a central component of scaffold architecture for solid organ tissue engineering. In this work, seven biomimetic principles were established as the major guiding technical design considerations of a branched vascular network for a tissue-engineered scaffold. These biomimetic design principles were applied to a branched radial architecture to develop a liver-specific vascular network. Iterative design changes and computational fluid dynamic analysis were used to optimize the network before mold manufacturing. The vascular network mold was created using a new mold technique that achieves a 1:1 aspect ratio for all channels. In vitro blood flow testing confirmed the physiologic hemodynamics of the network as predicted by computational fluid dynamic analysis. These results indicate that this biomimetic liver vascular network design will provide a foundation for developing complex vascular networks for solid organ tissue engineering that achieve physiologic blood flow. PMID:20001254

Principles of biomimetic vascular network design applied to a tissue-engineered liver scaffold.

PubMed

Hoganson, David M; Pryor, Howard I; Spool, Ira D; Burns, Owen H; Gilmore, J Randall; Vacanti, Joseph P

2010-05-01

Branched vascular networks are a central component of scaffold architecture for solid organ tissue engineering. In this work, seven biomimetic principles were established as the major guiding technical design considerations of a branched vascular network for a tissue-engineered scaffold. These biomimetic design principles were applied to a branched radial architecture to develop a liver-specific vascular network. Iterative design changes and computational fluid dynamic analysis were used to optimize the network before mold manufacturing. The vascular network mold was created using a new mold technique that achieves a 1:1 aspect ratio for all channels. In vitro blood flow testing confirmed the physiologic hemodynamics of the network as predicted by computational fluid dynamic analysis. These results indicate that this biomimetic liver vascular network design will provide a foundation for developing complex vascular networks for solid organ tissue engineering that achieve physiologic blood flow.

Physically-Based Modelling and Real-Time Simulation of Fluids.

NASA Astrophysics Data System (ADS)

Chen, Jim Xiong

1995-01-01

Simulating physically realistic complex fluid behaviors presents an extremely challenging problem for computer graphics researchers. Such behaviors include the effects of driving boats through water, blending differently colored fluids, rain falling and flowing on a terrain, fluids interacting in a Distributed Interactive Simulation (DIS), etc. Such capabilities are useful in computer art, advertising, education, entertainment, and training. We present a new method for physically-based modeling and real-time simulation of fluids in computer graphics and dynamic virtual environments. By solving the 2D Navier -Stokes equations using a CFD method, we map the surface into 3D using the corresponding pressures in the fluid flow field. This achieves realistic real-time fluid surface behaviors by employing the physical governing laws of fluids but avoiding extensive 3D fluid dynamics computations. To complement the surface behaviors, we calculate fluid volume and external boundary changes separately to achieve full 3D general fluid flow. To simulate physical activities in a DIS, we introduce a mechanism which uses a uniform time scale proportional to the clock-time and variable time-slicing to synchronize physical models such as fluids in the networked environment. Our approach can simulate many different fluid behaviors by changing the internal or external boundary conditions. It can model different kinds of fluids by varying the Reynolds number. It can simulate objects moving or floating in fluids. It can also produce synchronized general fluid flows in a DIS. Our model can serve as a testbed to simulate many other fluid phenomena which have never been successfully modeled previously.

Field-sensitivity To Rheological Parameters

NASA Astrophysics Data System (ADS)

Freund, Jonathan; Ewoldt, Randy

2017-11-01

We ask this question: where in a flow is a quantity of interest Q quantitatively sensitive to the model parameters θ-> describing the rheology of the fluid? This field sensitivity is computed via the numerical solution of the adjoint flow equations, as developed to expose the target sensitivity δQ / δθ-> (x) via the constraint of satisfying the flow equations. Our primary example is a sphere settling in Carbopol, for which we have experimental data. For this Carreau-model configuration, we simultaneously calculate how much a local change in the fluid intrinsic time-scale λ, limit-viscosities ηo and η∞, and exponent n would affect the drag D. Such field sensitivities can show where different fluid physics in the model (time scales, elastic versus viscous components, etc.) are important for the target observable and generally guide model refinement based on predictive goals. In this case, the computational cost of solving the local sensitivity problem is negligible relative to the flow. The Carreau-fluid/sphere example is illustrative; the utility of field sensitivity is in the design and analysis of less intuitive flows, for which we provide some additional examples.

Fluid Structural Analysis of Human Cerebral Aneurysm Using Their Own Wall Mechanical Properties

PubMed Central

Valencia, Alvaro; Burdiles, Patricio; Ignat, Miguel; Mura, Jorge; Rivera, Rodrigo; Sordo, Juan

2013-01-01

Computational Structural Dynamics (CSD) simulations, Computational Fluid Dynamics (CFD) simulation, and Fluid Structure Interaction (FSI) simulations were carried out in an anatomically realistic model of a saccular cerebral aneurysm with the objective of quantifying the effects of type of simulation on principal fluid and solid mechanics results. Eight CSD simulations, one CFD simulation, and four FSI simulations were made. The results allowed the study of the influence of the type of material elements in the solid, the aneurism's wall thickness, and the type of simulation on the modeling of a human cerebral aneurysm. The simulations use their own wall mechanical properties of the aneurysm. The more complex simulation was the FSI simulation completely coupled with hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness. The FSI simulation coupled in one direction using hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness is the one that presents the most similar results with respect to the more complex FSI simulation, requiring one-fourth of the calculation time. PMID:24151523

Computational and Experimental Investigations of the Molecular Scale Structure and Dynamics of Gologically Important Fluids and Mineral-Fluid Interfaces

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

Bowers, Geoffrey

United States Department of Energy grant DE-FG02-10ER16128, “Computational and Spectroscopic Investigations of the Molecular Scale Structure and Dynamics of Geologically Important Fluids and Mineral-Fluid Interfaces” (Geoffrey M. Bowers, P.I.) focused on developing a molecular-scale understanding of processes that occur in fluids and at solid-fluid interfaces using the combination of spectroscopic, microscopic, and diffraction studies with molecular dynamics computer modeling. The work is intimately tied to the twin proposal at Michigan State University (DOE DE-FG02-08ER15929; same title: R. James Kirkpatrick, P.I. and A. Ozgur Yazaydin, co-P.I.).

Research in progress and other activities of the Institute for Computer Applications in Science and Engineering

NASA Technical Reports Server (NTRS)

1993-01-01

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics and computer science during the period April 1, 1993 through September 30, 1993. The major categories of the current ICASE research program are: (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest to LaRC, including acoustic and combustion; (3) experimental research in transition and turbulence and aerodynamics involving LaRC facilities and scientists; and (4) computer science.

[Computer-assisted image processing for quantifying histopathologic variables in the healing of colonic anastomosis in dogs].

PubMed

Novelli, M D; Barreto, E; Matos, D; Saad, S S; Borra, R C

1997-01-01

The authors present the experimental results of the computerized quantifying of tissular structures involved in the reparative process of colonic anastomosis performed by manual suture and biofragmentable ring. The quantified variables in this study were: oedema fluid, myofiber tissue, blood vessel and cellular nuclei. An image processing software developed at Laboratório de Informática Dedicado à Odontologia (LIDO) was utilized to quantifying the pathognomonic alterations in the inflammatory process in colonic anastomosis performed in 14 dogs. The results were compared to those obtained through traditional way diagnosis by two pathologists in view of counterproof measures. The criteria for these diagnoses were defined in levels represented by absent, light, moderate and intensive which were compared to analysis performed by the computer. There was significant statistical difference between two techniques: the biofragmentable ring technique exhibited low oedema fluid, organized myofiber tissue and higher number of alongated cellular nuclei in relation to manual suture technique. The analysis of histometric variables through computational image processing was considered efficient and powerful to quantify the main tissular inflammatory and reparative changing.

Design and Analysis of Turbomachinery for Space Applications

NASA Technical Reports Server (NTRS)

Dorney, D.; Garcia, Roberto (Technical Monitor)

2002-01-01

This presentation provides an overview of CORSAIR, a three dimensional computational fluid dynamics software code for the analysis of turbomachinery components available from NASA, and discusses its potential use in the design of these parts. Topics covered include: time-dependent equations of motion, grid topology, turbulence models, boundary conditions, parallel simulations and miscellaneous capabilities.

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.

Computational fluid mechanics utilizing the variational principle of modeling damping seals

NASA Technical Reports Server (NTRS)

Abernathy, J. M.

1986-01-01

A computational fluid dynamics code for application to traditional incompressible flow problems has been developed. The method is actually a slight compressibility approach which takes advantage of the bulk modulus and finite sound speed of all real fluids. The finite element numerical analog uses a dynamic differencing scheme based, in part, on a variational principle for computational fluid dynamics. The code was developed in order to study the feasibility of damping seals for high speed turbomachinery. Preliminary seal analyses have been performed.

Interfacial gauge methods for incompressible fluid dynamics

PubMed Central

Saye, Robert

2016-01-01

Designing numerical methods for incompressible fluid flow involving moving interfaces, for example, in the computational modeling of bubble dynamics, swimming organisms, or surface waves, presents challenges due to the coupling of interfacial forces with incompressibility constraints. A class of methods, denoted interfacial gauge methods, is introduced for computing solutions to the corresponding incompressible Navier-Stokes equations. These methods use a type of “gauge freedom” to reduce the numerical coupling between fluid velocity, pressure, and interface position, allowing high-order accurate numerical methods to be developed more easily. Making use of an implicit mesh discontinuous Galerkin framework, developed in tandem with this work, high-order results are demonstrated, including surface tension dynamics in which fluid velocity, pressure, and interface geometry are computed with fourth-order spatial accuracy in the maximum norm. Applications are demonstrated with two-phase fluid flow displaying fine-scaled capillary wave dynamics, rigid body fluid-structure interaction, and a fluid-jet free surface flow problem exhibiting vortex shedding induced by a type of Plateau-Rayleigh instability. The developed methods can be generalized to other types of interfacial flow and facilitate precise computation of complex fluid interface phenomena. PMID:27386567

Computational Fluid Dynamics: Past, Present, And Future

NASA Technical Reports Server (NTRS)

Kutler, Paul

1988-01-01

Paper reviews development of computational fluid dynamics and explores future prospects of technology. Report covers such topics as computer technology, turbulence, development of solution methodology, developemnt of algorithms, definition of flow geometries, generation of computational grids, and pre- and post-data processing.

Development of Efficient Real-Fluid Model in Simulating Liquid Rocket Injector Flows

NASA Technical Reports Server (NTRS)

Cheng, Gary; Farmer, Richard

2003-01-01

The characteristics of propellant mixing near the injector have a profound effect on the liquid rocket engine performance. However, the flow features near the injector of liquid rocket engines are extremely complicated, for example supercritical-pressure spray, turbulent mixing, and chemical reactions are present. Previously, a homogeneous spray approach with a real-fluid property model was developed to account for the compressibility and evaporation effects such that thermodynamics properties of a mixture at a wide range of pressures and temperatures can be properly calculated, including liquid-phase, gas- phase, two-phase, and dense fluid regions. The developed homogeneous spray model demonstrated a good success in simulating uni- element shear coaxial injector spray combustion flows. However, the real-fluid model suffered a computational deficiency when applied to a pressure-based computational fluid dynamics (CFD) code. The deficiency is caused by the pressure and enthalpy being the independent variables in the solution procedure of a pressure-based code, whereas the real-fluid model utilizes density and temperature as independent variables. The objective of the present research work is to improve the computational efficiency of the real-fluid property model in computing thermal properties. The proposed approach is called an efficient real-fluid model, and the improvement of computational efficiency is achieved by using a combination of a liquid species and a gaseous species to represent a real-fluid species.

Analysis of electrophoresis performance

NASA Technical Reports Server (NTRS)

Roberts, Glyn O.

1988-01-01

A flexible efficient computer code is being developed to simulate electrophoretic separation phenomena, in either a cylindrical or a rectangular geometry. The code will computer the evolution in time of the concentrations of an arbitrary number of chemical species, and of the temperature, pH distribution, conductivity, electric field, and fluid motion. Use of nonuniform meshes and fast accurate implicit time-stepping will yield accurate answers at economical cost.

Aerodynamic analysis of Pegasus - Computations vs reality

NASA Technical Reports Server (NTRS)

Mendenhall, Michael R.; Lesieutre, Daniel J.; Whittaker, C. H.; Curry, Robert E.; Moulton, Bryan

1993-01-01

Pegasus, a three-stage, air-launched, winged space booster was developed to provide fast and efficient commercial launch services for small satellites. The aerodynamic design and analysis of Pegasus was conducted without benefit of wind tunnel tests using only computational aerodynamic and fluid dynamic methods. Flight test data from the first two operational flights of Pegasus are now available, and they provide an opportunity to validate the accuracy of the predicted pre-flight aerodynamic characteristics. Comparisons of measured and predicted flight characteristics are presented and discussed. Results show that the computational methods provide reasonable aerodynamic design information with acceptable margins. Post-flight analyses illustrate certain areas in which improvements are desired.

Reduced-Order Models for the Aeroelastic Analysis of Ares Launch Vehicles

NASA Technical Reports Server (NTRS)

Silva, Walter A.; Vatsa, Veer N.; Biedron, Robert T.

2010-01-01

This document presents the development and application of unsteady aerodynamic, structural dynamic, and aeroelastic reduced-order models (ROMs) for the ascent aeroelastic analysis of the Ares I-X flight test and Ares I crew launch vehicles using the unstructured-grid, aeroelastic FUN3D computational fluid dynamics (CFD) code. The purpose of this work is to perform computationally-efficient aeroelastic response calculations that would be prohibitively expensive via computation of multiple full-order aeroelastic FUN3D solutions. These efficient aeroelastic ROM solutions provide valuable insight regarding the aeroelastic sensitivity of the vehicles to various parameters over a range of dynamic pressures.

Cumulative reports and publications through 31 December 1983

NASA Technical Reports Server (NTRS)

1983-01-01

All reports for the calendar years 1975 through December 1983 are listed by author. Since ICASE reports are intended to be preprints of articles for journals and conference proceedings, the published reference is included when available. Thirteen older journal and conference proceedings references are included as well as five additional reports by ICASE personnel. Major categories of research covered include: (1) numerical methods, with particular emphasis on the development and analysis of basic algorithms; (2) computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, structural analysis, and chemistry; and (3) computer systems and software, especially vector and parallel computers, microcomputers, and data management.

Thermo-fluid-dynamics of natural convection around a heated vertical plate with a critical assessment of the standard similarity theory

NASA Astrophysics Data System (ADS)

Guha, Abhijit; Nayek, Subhajit

2017-10-01

A compulsory element of all textbooks on natural convection has been a detailed similarity analysis for laminar natural convection on a heated semi-infinite vertical plate and a routinely used boundary condition for such analysis is u = 0 at x = 0. The same boundary condition continues to be assumed in related theoretical analyses, even in recent publications. The present work examines the consequence of this long-held assumption, which appears to have never been questioned in the literature, on the fluid dynamics and heat transfer characteristics. The assessment has been made here by solving the Navier-Stokes equations numerically with two boundary conditions—one with constrained velocity at x = 0 to mimic the similarity analysis and the other with no such constraints simulating the case of a heated vertical plate in an infinite expanse of the quiescent fluid medium. It is found that the fluid flow field given by the similarity theory is drastically different from that given by the computational fluid dynamics (CFD) simulations with unconstrained velocity. This also reflects on the Nusselt number, the prediction of the CFD simulations with unconstrained velocity being quite close to the experimentally measured values at all Grashof and Prandtl numbers (this is the first time theoretically computed values of the average Nusselt number N u ¯ are found to be so close to the experimental values). The difference of the Nusselt number (Δ N u ¯ ) predicted by the similarity theory and that by the CFD simulations (as well as the measured values), both computed with a high degree of precision, can be very significant, particularly at low Grashof numbers and at Prandtl numbers far removed from unity. Computations show that within the range of investigations (104 ≤ GrL ≤ 108, 0.01 ≤ Pr ≤ 100), the maximum value of Δ N u ¯ may be of the order 50%. Thus, for quantitative predictions, the available theory (i.e., similarity analysis) can be rather inadequate. With the help of the CFD simulations, the details of the fluid dynamics, particularly the physics of fluid entrainment, are thoroughly studied. It is shown that the relative proportions of the fluid entrainment from the bottom, top, and side of the vertical plate depend on the size of the region of interest (ROI). As the size of the ROI is made large, most of the entrained fluid comes from the bottom, a little bit from the top and almost no fluid enters from the side; the nature of entrainment is opposite in the similarity analysis for which all the fluid enters from the side and no fluid enters either from the bottom or the top. The two sets of CFD simulations establish, in particular, the conclusion that it is the inappropriateness of the age-old boundary condition u = 0 at x = 0, and not the boundary layer approximation, that is the principal cause for the vulnerability of the standard similarity analyses (and integral theories) for natural convection. The CFD solutions further demonstrate the effects of finite length and finite thickness of the plate on the flow field and the shape of the buoyant jet. The different boundary conditions on the two sides of the vertical plate and the presence of its finite thickness make the buoyant jet bend over the top edge of the plate and make the evolution of entrainment from the two sides of the free buoyant jet different. The entrainment velocity from the two sides, however, equilibrates at a certain distance above the plate. The asymmetry in the velocity and temperature fields above the plate decreases more rapidly when Pr is smaller and GrL is greater. It is shown that sufficiently above the plate, the distributions of axial velocity and temperature in the buoyant jet tend to be symmetric with respect to an axis that seems to pass through the vertical mid-plane of the plate, i.e., the jet tends to lose its history of origination.

Pretest predictions of surface strain and fluid pressures in mercury targets undergoing thermal shock

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

Taleyarkhan, R.P.; Kim, S.H.; Haines, J.

The authors provide a perspective overview of pretest modeling and analysis work related to thermal shock effects in spallation neutron source targets that were designed for conducting thermal shock experiments at the Los Alamos Neutron Science Center (LANSCE). Data to be derived are to be used for benchmarking computational tools as well as to assess the efficacy of optical gauges for monitoring dynamic fluid pressures and phenomena such as the onset of cavitation.

Hybrid Parallelization of Adaptive MHD-Kinetic Module in Multi-Scale Fluid-Kinetic Simulation Suite

DOE PAGES

Borovikov, Sergey; Heerikhuisen, Jacob; Pogorelov, Nikolai

2013-04-01

The Multi-Scale Fluid-Kinetic Simulation Suite has a computational tool set for solving partially ionized flows. In this paper we focus on recent developments of the kinetic module which solves the Boltzmann equation using the Monte-Carlo method. The module has been recently redesigned to utilize intra-node hybrid parallelization. We describe in detail the redesign process, implementation issues, and modifications made to the code. Finally, we conduct a performance analysis.

Calculating Mass Diffusion in High-Pressure Binary Fluids

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth

2004-01-01

A comprehensive mathematical model of mass diffusion has been developed for binary fluids at high pressures, including critical and supercritical pressures. Heretofore, diverse expressions, valid for limited parameter ranges, have been used to correlate high-pressure binary mass-diffusion-coefficient data. This model will likely be especially useful in the computational simulation and analysis of combustion phenomena in diesel engines, gas turbines, and liquid rocket engines, wherein mass diffusion at high pressure plays a major role.

A Dynamic Analysis of Hydrodynamic Wave Journal Bearings

NASA Technical Reports Server (NTRS)

Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G.

2008-01-01

The purpose of this paper is to study the dynamic behavior of a three-wave journal bearing using a transient approach. The transient analysis permits the determination of the rotor behavior after the fractional frequency whirl appears. The journal trajectory is determined by solving a set of nonlinear equations of motion using the Runge-Katta method. The fluid film forces are computed by integrating the transient Reynolds equation at each time step location of the shaft with respect to the bearing. Because of the large values of the rotational speeds, turbulent effects were included in the computations. The influence of the temperature on the viscosity was also considered. Numerical results were compared to experimenta1 results obtained at the NASA Glenn Research Center. Comparisons of the theoretical results with experimental data were found to be in good agreement. The numerical and experimental results showed that the fluid film of a three-wave journal bearing having a diameter of 30 mm, a length of 27 mm, and a wave amplitude ratio greater than 0.15 is stable even at rotational speeds of 60,000 RPM. For lower wave amplitude ratios, the threshold speed at which the fluid film becomes unstable depends on the wave amplitude and on the supply pocket pressure. Even if the fluid film is unstable, the wave bearing maintains the whirl orbit inside the bearing clearance.

Computational fluid modeling and performance analysis of a bidirectional rotating perfusion culture system.

PubMed

Kang, Chang-Wei; Wang, Yan; Tania, Marshella; Zhou, Huancheng; Gao, Yi; Ba, Te; Tan, Guo-Dong Sean; Kim, Sangho; Leo, Hwa Liang

2013-01-01

A myriad of bioreactor configurations have been investigated as extracorporeal medical support systems for temporary replacement of vital organ functions. In recent years, studies have demonstrated that the rotating bioreactors have the potential to be utilized as bioartificial liver assist devices (BLADs) owing to their advantage of ease of scalability of cell-culture volume. However, the fluid movement in the rotating chamber will expose the suspended cells to unwanted flow structures with abnormally high shear conditions that may result in poor cell stability and in turn lower the efficacy of the bioreactor system. In this study, we compared the hydrodynamic performance of our modified rotating bioreactor design with that of an existing rotating bioreactor design. Computational fluid dynamic analysis coupled with experimental results were employed in the optimization process for the development of the modified bioreactor design. Our simulation results showed that the modified bioreactor had lower fluid induced shear stresses and more uniform flow conditions within its rotating chamber than the conventional design. Experimental results revealed that the cells within the modified bioreactor also exhibited better cell-carrier attachment, higher metabolic activity, and cell viability compared to those in the conventional design. In conclusion, this study was able to provide important insights into the flow physics within the rotating bioreactors, and help enhanced the hydrodynamic performance of an existing rotating bioreactor for BLAD applications. © 2013 American Institute of Chemical Engineers.

Role of computational fluid dynamics in unsteady aerodynamics for aeroelasticity

NASA Technical Reports Server (NTRS)

Guruswamy, Guru P.; Goorjian, Peter M.

1989-01-01

In the last two decades there have been extensive developments in computational unsteady transonic aerodynamics. Such developments are essential since the transonic regime plays an important role in the design of modern aircraft. Therefore, there has been a large effort to develop computational tools with which to accurately perform flutter analysis at transonic speeds. In the area of Computational Fluid Dynamics (CFD), unsteady transonic aerodynamics are characterized by the feature of modeling the motion of shock waves over aerodynamic bodies, such as wings. This modeling requires the solution of nonlinear partial differential equations. Most advanced codes such as XTRAN3S use the transonic small perturbation equation. Currently, XTRAN3S is being used for generic research in unsteady aerodynamics and aeroelasticity of almost full aircraft configurations. Use of Euler/Navier Stokes equations for simple typical sections has just begun. A brief history of the development of CFD for aeroelastic applications is summarized. The development of unsteady transonic aerodynamics and aeroelasticity are also summarized.

Risk assessment of occupational exposure to benzene using numerical simulation in a complex geometry of a reforming unit of petroleum refinery.

PubMed

Bayatian, Majid; Ashrafi, Khosro; Azari, Mansour Rezazadeh; Jafari, Mohammad Javad; Mehrabi, Yadollah

2018-04-01

There has been an increasing concern about the continuous and the sudden release of volatile organic pollutants from petroleum refineries and occupational and environmental exposures. Benzene is one of the most prevalent volatile compounds, and it has been addressed by many authors for its potential toxicity in occupational and environmental settings. Due to the complexities of sampling and analysis of benzene in routine and accidental situations, a reliable estimation of the benzene concentration in the outdoor setting of refinery using a computational fluid dynamics (CFD) could be instrumental for risk assessment of occupational exposure. In the present work, a computational fluid dynamic model was applied for exposure risk assessment with consideration of benzene being released continuously from a reforming unit of a refinery. For simulation of benzene dispersion, GAMBIT, FLUENT, and CFD post software are used as preprocessing, processing, and post-processing, respectively. Computational fluid dynamic validation was carried out by comparing the computed data with the experimental measurements. Eventually, chronic daily intake and lifetime cancer risk for routine operations through the two seasons of a year are estimated through the simulation model. Root mean square errors are 0.19 and 0.17 for wind speed and concentration, respectively. Lifetime risk assessments of workers are 0.4-3.8 and 0.0096-0.25 per 1000 workers in stable and unstable atmospheric conditions, respectively. Exposure risk is unacceptable for the head of shift work, chief engineer, and general workers in 141 days (38.77%) in a year. The results of this study show that computational fluid dynamics is a useful tool for modeling of benzene exposure in a complex geometry and can be used to estimate lifetime risks of occupation groups in a refinery setting.

HIGH-FIDELITY SIMULATION-DRIVEN MODEL DEVELOPMENT FOR COARSE-GRAINED COMPUTATIONAL FLUID DYNAMICS

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

Hanna, Botros N.; Dinh, Nam T.; Bolotnov, Igor A.

Nuclear reactor safety analysis requires identifying various credible accident scenarios and determining their consequences. For a full-scale nuclear power plant system behavior, it is impossible to obtain sufficient experimental data for a broad range of risk-significant accident scenarios. In single-phase flow convective problems, Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) can provide us with high fidelity results when physical data are unavailable. However, these methods are computationally expensive and cannot be afforded for simulation of long transient scenarios in nuclear accidents despite extraordinary advances in high performance scientific computing over the past decades. The major issue is themore » inability to make the transient computation parallel, thus making number of time steps required in high-fidelity methods unaffordable for long transients. In this work, we propose to apply a high fidelity simulation-driven approach to model sub-grid scale (SGS) effect in Coarse Grained Computational Fluid Dynamics CG-CFD. This approach aims to develop a statistical surrogate model instead of the deterministic SGS model. We chose to start with a turbulent natural convection case with volumetric heating in a horizontal fluid layer with a rigid, insulated lower boundary and isothermal (cold) upper boundary. This scenario of unstable stratification is relevant to turbulent natural convection in a molten corium pool during a severe nuclear reactor accident, as well as in containment mixing and passive cooling. The presented approach demonstrates how to create a correction for the CG-CFD solution by modifying the energy balance equation. A global correction for the temperature equation proves to achieve a significant improvement to the prediction of steady state temperature distribution through the fluid layer.« less

Quasi-one-dimensional compressible flow across face seals and narrow slots. 2: Computer program

NASA Technical Reports Server (NTRS)

Zuk, J.; Smith, P. J.

1972-01-01

A computer program is presented for compressible fluid flow with friction across face seals and through narrow slots. The computer program carries out a quasi-one-dimensional flow analysis which is valid for laminar and turbulent flows under both subsonic and choked flow conditions for parallel surfaces. The program is written in FORTRAN IV. The input and output variables are in either the International System of Units (SI) or the U.S. customary system.

Using Computers in Fluids Engineering Education

NASA Technical Reports Server (NTRS)

Benson, Thomas J.

1998-01-01

Three approaches for using computers to improve basic fluids engineering education are presented. The use of computational fluid dynamics solutions to fundamental flow problems is discussed. The use of interactive, highly graphical software which operates on either a modern workstation or personal computer is highlighted. And finally, the development of 'textbooks' and teaching aids which are used and distributed on the World Wide Web is described. Arguments for and against this technology as applied to undergraduate education are also discussed.

Computer program MCAP-TOSS calculates steady-state fluid dynamics of coolant in parallel channels and temperature distribution in surrounding heat-generating solid

NASA Technical Reports Server (NTRS)

Lee, A. Y.

1967-01-01

Computer program calculates the steady state fluid distribution, temperature rise, and pressure drop of a coolant, the material temperature distribution of a heat generating solid, and the heat flux distributions at the fluid-solid interfaces. It performs the necessary iterations automatically within the computer, in one machine run.

Thirteenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion and Launch Vehicle Technology. Volume 1

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1996-01-01

The purpose of the workshop was to discuss experimental and computational fluid dynamic activities in rocket propulsion and launch vehicles. The workshop was an open meeting for government, industry, and academia. A broad number of topics were discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Computer simulation to predict energy use, greenhouse gas emissions and costs for production of fluid milk using alternative processing methods

USDA-ARS?s Scientific Manuscript database

Computer simulation is a useful tool for benchmarking the electrical and fuel energy consumption and water use in a fluid milk plant. In this study, a computer simulation model of the fluid milk process based on high temperature short time (HTST) pasteurization was extended to include models for pr...

Computational analysis of plane and parabolic flow of MHD Carreau fluid with buoyancy and exponential heat source effects

NASA Astrophysics Data System (ADS)

Krishna, P. Mohan; Sandeep, N.; Sharma, Ram Prakash

2017-05-01

This paper presents the two-dimensional magnetohydrodynamic Carreau fluid flow over a plane and parabolic regions in the form of buoyancy and exponential heat source effects. Soret and Dufour effects are used to examine the heat and mass transfer process. The system of ODE's is obtained by utilizing similarity transformations. The RK-based shooting process is employed to generate the numerical solutions. The impact of different parameters of interest on fluid flow, concentration and thermal fields is characterized graphically. Tabular results are presented to discuss the wall friction, reduced Nusselt and Sherwood numbers. It is seen that the flow, thermal and concentration boundary layers of the plane and parabolic flows of Carreau fluid are non-uniform.

Grid-converged solution and analysis of the unsteady viscous flow in a two-dimensional shock tube

NASA Astrophysics Data System (ADS)

Zhou, Guangzhao; Xu, Kun; Liu, Feng

2018-01-01

The flow in a shock tube is extremely complex with dynamic multi-scale structures of sharp fronts, flow separation, and vortices due to the interaction of the shock wave, the contact surface, and the boundary layer over the side wall of the tube. Prediction and understanding of the complex fluid dynamics are of theoretical and practical importance. It is also an extremely challenging problem for numerical simulation, especially at relatively high Reynolds numbers. Daru and Tenaud ["Evaluation of TVD high resolution schemes for unsteady viscous shocked flows," Comput. Fluids 30, 89-113 (2001)] proposed a two-dimensional model problem as a numerical test case for high-resolution schemes to simulate the flow field in a square closed shock tube. Though many researchers attempted this problem using a variety of computational methods, there is not yet an agreed-upon grid-converged solution of the problem at the Reynolds number of 1000. This paper presents a rigorous grid-convergence study and the resulting grid-converged solutions for this problem by using a newly developed, efficient, and high-order gas-kinetic scheme. Critical data extracted from the converged solutions are documented as benchmark data. The complex fluid dynamics of the flow at Re = 1000 are discussed and analyzed in detail. Major phenomena revealed by the numerical computations include the downward concentration of the fluid through the curved shock, the formation of the vortices, the mechanism of the shock wave bifurcation, the structure of the jet along the bottom wall, and the Kelvin-Helmholtz instability near the contact surface. Presentation and analysis of those flow processes provide important physical insight into the complex flow physics occurring in a shock tube.

Computational Fluid Dynamics Analysis of the Effect of Plaques in the Left Coronary Artery

PubMed Central

Chaichana, Thanapong; Sun, Zhonghua; Jewkes, James

2012-01-01

This study was to investigate the hemodynamic effect of simulated plaques in left coronary artery models, which were generated from a sample patient's data. Plaques were simulated and placed at the left main stem and the left anterior descending (LAD) to produce at least 60% coronary stenosis. Computational fluid dynamics analysis was performed to simulate realistic physiological conditions that reflect the in vivo cardiac hemodynamics, and comparison of wall shear stress (WSS) between Newtonian and non-Newtonian fluid models was performed. The pressure gradient (PSG) and flow velocities in the left coronary artery were measured and compared in the left coronary models with and without presence of plaques during cardiac cycle. Our results showed that the highest PSG was observed in stenotic regions caused by the plaques. Low flow velocity areas were found at postplaque locations in the left circumflex, LAD, and bifurcation. WSS at the stenotic locations was similar between the non-Newtonian and Newtonian models although some more details were observed with non-Newtonian model. There is a direct correlation between coronary plaques and subsequent hemodynamic changes, based on the simulation of plaques in the realistic coronary models. PMID:22400051

Angled injection: Hybrid fluid film bearings for cryogenic applications

NASA Technical Reports Server (NTRS)

SanAndres, Luis

1995-01-01

A computational bulk-flow analysis for prediction of the force coefficients of hybrid fluid film bearings with angled orifice injection is presented. Past measurements on water-lubricated hybrid bearings with angle orifice injection have demonstrated improved rotordynamic performance with virtual elimination of cross-coupled stiffness coefficients and nul or negative whirl frequency ratios. A simple analysis reveals that the fluid momentum exchange at the orifice discharge produces a pressure rise in the recess which retards the shear flow induced by journal rotation, and consequently, reduces cross-coupling forces. The predictions from the model correlate well with experimental measurements from a radial and 45 deg angled orifice injection, five recess water hybrid bearings (C = 125 microns) operating at 10.2, 17.4, and 24.6 krpm and with nominal supply pressures equal to 4, 5.5, and 7 MPa. An application example for a liquid oxygen six recess/pad hybrid journal bearing shows the advantages of tangential orifice injection on the rotordynamic force coefficients and stability indicator for forward whirl motions and without performance degradation on direct stiffness and damping coefficients. The computer program generated, 'hydrojet,' extends and complements previously developed codes.

Marc Henry de Frahan | NREL

Science.gov Websites

Computing Project, Marc develops high-fidelity turbulence models to enhance simulation accuracy and efficient numerical algorithms for future high performance computing hardware architectures. Research Interests High performance computing High order numerical methods for computational fluid dynamics Fluid

A Computational Fluid Dynamic Model for a Novel Flash Ironmaking Process

NASA Astrophysics Data System (ADS)

Perez-Fontes, Silvia E.; Sohn, Hong Yong; Olivas-Martinez, Miguel

A computational fluid dynamic model for a novel flash ironmaking process based on the direct gaseous reduction of iron oxide concentrates is presented. The model solves the three-dimensional governing equations including both gas-phase and gas-solid reaction kinetics. The turbulence-chemistry interaction in the gas-phase is modeled by the eddy dissipation concept incorporating chemical kinetics. The particle cloud model is used to track the particle phase in a Lagrangian framework. A nucleation and growth kinetics rate expression is adopted to calculate the reduction rate of magnetite concentrate particles. Benchmark experiments reported in the literature for a nonreacting swirling gas jet and a nonpremixed hydrogen jet flame were simulated for validation. The model predictions showed good agreement with measurements in terms of gas velocity, gas temperature and species concentrations. The relevance of the computational model for the analysis of a bench reactor operation and the design of an industrial-pilot plant is discussed.

Parallelization of implicit finite difference schemes in computational fluid dynamics

NASA Technical Reports Server (NTRS)

Decker, Naomi H.; Naik, Vijay K.; Nicoules, Michel

1990-01-01

Implicit finite difference schemes are often the preferred numerical schemes in computational fluid dynamics, requiring less stringent stability bounds than the explicit schemes. Each iteration in an implicit scheme involves global data dependencies in the form of second and higher order recurrences. Efficient parallel implementations of such iterative methods are considerably more difficult and non-intuitive. The parallelization of the implicit schemes that are used for solving the Euler and the thin layer Navier-Stokes equations and that require inversions of large linear systems in the form of block tri-diagonal and/or block penta-diagonal matrices is discussed. Three-dimensional cases are emphasized and schemes that minimize the total execution time are presented. Partitioning and scheduling schemes for alleviating the effects of the global data dependencies are described. An analysis of the communication and the computation aspects of these methods is presented. The effect of the boundary conditions on the parallel schemes is also discussed.

Construction and Utilization of a Beowulf Computing Cluster: A User's Perspective

NASA Technical Reports Server (NTRS)

Woods, Judy L.; West, Jeff S.; Sulyma, Peter R.

2000-01-01

Lockheed Martin Space Operations - Stennis Programs (LMSO) at the John C Stennis Space Center (NASA/SSC) has designed and built a Beowulf computer cluster which is owned by NASA/SSC and operated by LMSO. The design and construction of the cluster are detailed in this paper. The cluster is currently used for Computational Fluid Dynamics (CFD) simulations. The CFD codes in use and their applications are discussed. Examples of some of the work are also presented. Performance benchmark studies have been conducted for the CFD codes being run on the cluster. The results of two of the studies are presented and discussed. The cluster is not currently being utilized to its full potential; therefore, plans are underway to add more capabilities. These include the addition of structural, thermal, fluid, and acoustic Finite Element Analysis codes as well as real-time data acquisition and processing during test operations at NASA/SSC. These plans are discussed as well.

Modeling of a Sequential Two-Stage Combustor

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Liu, N.-S.; Gallagher, J. R.; Ryder, R. C.; Brankovic, A.; Hendricks, J. A.

2005-01-01

A sequential two-stage, natural gas fueled power generation combustion system is modeled to examine the fundamental aerodynamic and combustion characteristics of the system. The modeling methodology includes CAD-based geometry definition, and combustion computational fluid dynamics analysis. Graphical analysis is used to examine the complex vortical patterns in each component, identifying sources of pressure loss. The simulations demonstrate the importance of including the rotating high-pressure turbine blades in the computation, as this results in direct computation of combustion within the first turbine stage, and accurate simulation of the flow in the second combustion stage. The direct computation of hot-streaks through the rotating high-pressure turbine stage leads to improved understanding of the aerodynamic relationships between the primary and secondary combustors and the turbomachinery.

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC. Quarterly report January through March 2011. Year 1 Quarter 2 progress report.

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

Lottes, S. A.; Kulak, R. F.; Bojanowski, C.

2011-05-19

This project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at the Turner-Fairbank Highway Research Center for a period of five years, beginning in October 2010. The analysis methods employ well-benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focusmore » of the project are wind and water loads on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to assess them for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, vehicle stability under high wind loading, and the use of electromagnetic shock absorbers to improve vehicle stability under high wind conditions. This quarterly report documents technical progress on the project tasks for the period of January through March 2011.« less

Shaded computer graphic techniques for visualizing and interpreting analytic fluid flow models

NASA Technical Reports Server (NTRS)

Parke, F. I.

1981-01-01

Mathematical models which predict the behavior of fluid flow in different experiments are simulated using digital computers. The simulations predict values of parameters of the fluid flow (pressure, temperature and velocity vector) at many points in the fluid. Visualization of the spatial variation in the value of these parameters is important to comprehend and check the data generated, to identify the regions of interest in the flow, and for effectively communicating information about the flow to others. The state of the art imaging techniques developed in the field of three dimensional shaded computer graphics is applied to visualization of fluid flow. Use of an imaging technique known as 'SCAN' for visualizing fluid flow, is studied and the results are presented.

The NASTRAN theoretical manual

NASA Technical Reports Server (NTRS)

1981-01-01

Designed to accommodate additions and modifications, this commentary on NASTRAN describes the problem solving capabilities of the program in a narrative fashion and presents developments of the analytical and numerical procedures that underlie the program. Seventeen major sections and numerous subsections cover; the organizational aspects of the program, utility matrix routines, static structural analysis, heat transfer, dynamic structural analysis, computer graphics, special structural modeling techniques, error analysis, interaction between structures and fluids, and aeroelastic analysis.

Computational Fluid Dynamics Simulation Study of Active Power Control in Wind Plants

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

Fleming, Paul; Aho, Jake; Gebraad, Pieter

2016-08-01

This paper presents an analysis performed on a wind plant's ability to provide active power control services using a high-fidelity computational fluid dynamics-based wind plant simulator. This approach allows examination of the impact on wind turbine wake interactions within a wind plant on performance of the wind plant controller. The paper investigates several control methods for improving performance in waked conditions. One method uses wind plant wake controls, an active field of research in which wind turbine control systems are coordinated to account for their wakes, to improve the overall performance. Results demonstrate the challenge of providing active power controlmore » in waked conditions but also the potential methods for improving this performance.« less

Research in Applied Mathematics, Fluid Mechanics and Computer Science

NASA Technical Reports Server (NTRS)

1999-01-01

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period October 1, 1998 through March 31, 1999.

[Research activities in applied mathematics, fluid mechanics, and computer science

NASA Technical Reports Server (NTRS)

1995-01-01

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period April 1, 1995 through September 30, 1995.

Computer program for quasi-one-dimensional compressible flow with area change and friction - Application to gas film seals

NASA Technical Reports Server (NTRS)

Zuk, J.; Smith, P. J.

1974-01-01

A computer program is presented for compressible fluid flow with friction and area change. The program carries out a quasi-one-dimensional flow analysis which is valid for laminar and turbulent flows under both subsonic and choked flow conditions. The program was written to be applied to gas film seals. The area-change analysis should prove useful for choked flow conditions with small mean thickness, as well as for face seals where radial area change is significant. The program is written in FORTRAN 4.

Automated Parameter Studies Using a Cartesian Method

NASA Technical Reports Server (NTRS)

Murman, Scott M.; Aftosimis, Michael J.; Nemec, Marian

2004-01-01

Computational Fluid Dynamics (CFD) is now routinely used to analyze isolated points in a design space by performing steady-state computations at fixed flight conditions (Mach number, angle of attack, sideslip), for a fixed geometric configuration of interest. This "point analysis" provides detailed information about the flowfield, which aides an engineer in understanding, or correcting, a design. A point analysis is typically performed using high fidelity methods at a handful of critical design points, e.g. a cruise or landing configuration, or a sample of points along a flight trajectory.

Analytical approach on the stiffness of MR fluid filled spring

NASA Astrophysics Data System (ADS)

Sikulskyi, Stanislav; Kim, Daewon

2017-04-01

A solid mechanical spring generally exhibits uniform stiffness. This paper studies a mechanical spring filled with magnetorheological (MR) fluid to achieve controllable stiffness. The hollow spring filled with MR fluid is subjected to a controlled magnetic field in order to change the viscosity of the MR fluid and thereby to change the overall stiffness of the spring. MR fluid is considered as a Bingham viscoplastic linear material in the mathematical model. The goal of this research is to study the feasibility of such spring system by analytically computing the effects of MR fluid on overall spring stiffness. For this purpose, spring mechanics and MR fluid behavior are studied to increase the accuracy of the analysis. Numerical simulations are also performed to generate some assumptions, which simplify calculations in the analytical part. The accuracy of the present approach is validated by comparing the analytical results to previously known experimental results. Overall stiffness variations of the spring are also discussed for different spring designs.

Nonlinear Computational Aeroelasticity: Formulations and Solution Algorithms

DTIC Science & Technology

2003-03-01

problem is proposed. Fluid-structure coupling algorithms are then discussed with some emphasis on distributed computing strategies. Numerical results...the structure and the exchange of structure motion to the fluid. The computational fluid dynamics code PFES is our finite element code for the numerical ...unstructured meshes). It was numerically demonstrated [1-3] that EBS can be less diffusive than SUPG [4-6] and the standard Finite Volume schemes

Multi-blocking strategies for the INS3D incompressible Navier-Stokes code

NASA Technical Reports Server (NTRS)

Gatlin, Boyd

1990-01-01

With the continuing development of bigger and faster supercomputers, computational fluid dynamics (CFD) has become a useful tool for real-world engineering design and analysis. However, the number of grid points necessary to resolve realistic flow fields numerically can easily exceed the memory capacity of available computers. In addition, geometric shapes of flow fields, such as those in the Space Shuttle Main Engine (SSME) power head, may be impossible to fill with continuous grids upon which to obtain numerical solutions to the equations of fluid motion. The solution to this dilemma is simply to decompose the computational domain into subblocks of manageable size. Computer codes that are single-block by construction can be modified to handle multiple blocks, but ad-hoc changes in the FORTRAN have to be made for each geometry treated. For engineering design and analysis, what is needed is generalization so that the blocking arrangement can be specified by the user. INS3D is a computer program for the solution of steady, incompressible flow problems. It is used frequently to solve engineering problems in the CFD Branch at Marshall Space Flight Center. INS3D uses an implicit solution algorithm and the concept of artificial compressibility to provide the necessary coupling between the pressure field and the velocity field. The development of generalized multi-block capability in INS3D is described.

A unified momentum equation approach for computing thermal residual stresses during melting and solidification

NASA Astrophysics Data System (ADS)

Yeo, Haram; Ki, Hyungson

2018-03-01

In this article, we present a novel numerical method for computing thermal residual stresses from a viewpoint of fluid-structure interaction (FSI). In a thermal processing of a material, residual stresses are developed as the material undergoes melting and solidification, and liquid, solid, and a mixture of liquid and solid (or mushy state) coexist and interact with each other during the process. In order to accurately account for the stress development during phase changes, we derived a unified momentum equation from the momentum equations of incompressible fluids and elastoplastic solids. In this approach, the whole fluid-structure system is treated as a single continuum, and the interaction between fluid and solid phases across the mushy zone is naturally taken into account in a monolithic way. For thermal analysis, an enthalpy-based method was employed. As a numerical example, a two-dimensional laser heating problem was considered, where a carbon steel sheet was heated by a Gaussian laser beam. Momentum and energy equations were discretized on a uniform Cartesian grid in a finite volume framework, and temperature-dependent material properties were used. The austenite-martensite phase transformation of carbon steel was also considered. In this study, the effects of solid strains, fluid flow, mushy zone size, and laser heating time on residual stress formation were investigated.

A portable and affordable extensional rheometer for field testing

NASA Astrophysics Data System (ADS)

Hallmark, Bart; Bryan, Matthew; Bosson, Ed; Butler, Simon; Hoier, Tom; Magens, Ole; Pistre, Nicolas; Pratt, Lee; Ward, Betsy-Ann; Wibberley, Sam; Wilson, D. Ian

2016-12-01

Extensional shear testing is often needed to characterise the behaviour of complex fluids found in industry and nature. Traditional extensional rheometers are typically expensive, fragile and heavy and are only suited to making measurements in a laboratory environment. For some applications, it is necessary to make in situ rheological measurements where, for example, fluid properties change rapidly over time or where laboratory facilities are unavailable. This paper reports the development and validation of an inexpensive, lightweight and robust ‘open source’ extensional rheometer, Seymour II. Validation was carried out experimentally and computationally. Measurements on a Newtonian fluid (492 mPa s Brookfield silicone oil) yielded results of 510  ±  51 mPa s; these are comfortably within the range of  ±10% which other authors have quoted for extensional techniques using laboratory rheometers. Comparison of the observed filament thinning dynamics to those obtained using computational fluid dynamics (CFD) gave good qualitative agreement. Use of Seymour II at the University of Cambridge Botanic Gardens revealed that the mucilage of the ‘crane flower’, Strelitzia reginae, was a viscoelastic fluid whose extensional response could be described by a two-mode Giesekus equation. Engineering drawings and image analysis code for Seymour II are available for download at the project website, www.seymourII.org/.

Generating Inviscid and Viscous Fluid Flow Simulations over a Surface Using a Quasi-simultaneous Technique

NASA Technical Reports Server (NTRS)

Sturdza, Peter (Inventor); Martins-Rivas, Herve (Inventor); Suzuki, Yoshifumi (Inventor)

2014-01-01

A fluid-flow simulation over a computer-generated surface is generated using a quasi-simultaneous technique. The simulation includes a fluid-flow mesh of inviscid and boundary-layer fluid cells. An initial fluid property for an inviscid fluid cell is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. An initial boundary-layer fluid property a boundary-layer fluid cell is determined using the initial fluid property and a viscous fluid simulation that simulates fluid viscous effects. An updated boundary-layer fluid property is determined for the boundary-layer fluid cell using the initial fluid property, initial boundary-layer fluid property, and an interaction law. The interaction law approximates the inviscid fluid simulation using a matrix of aerodynamic influence coefficients computed using a two-dimensional surface panel technique and a fluid-property vector. An updated fluid property is determined for the inviscid fluid cell using the updated boundary-layer fluid property.

Blading Design for Axial Turbomachines

DTIC Science & Technology

1989-05-01

three- dimensional, viscous computation systems appear to have a long development period ahead, in which fluid shear stress modeling and computation time ...and n directions and T is the shear stress , As a consequence the solution time is longer than for integral methods, dependent largely on thc accuracy of...distributions over airfoils is an adaptation of thin plate deflection theory from stress analysis. At the same time , it minimizes designer effort

Interfacial gauge methods for incompressible fluid dynamics

DOE PAGES

Saye, R.

2016-06-10

Designing numerical methods for incompressible fluid flow involving moving interfaces, for example, in the computational modeling of bubble dynamics, swimming organisms, or surface waves, presents challenges due to the coupling of interfacial forces with incompressibility constraints. A class of methods, denoted interfacial gauge methods, is introduced for computing solutions to the corresponding incompressible Navier-Stokes equations. These methods use a type of "gauge freedom" to reduce the numerical coupling between fluid velocity, pressure, and interface position, allowing high-order accurate numerical methods to be developed more easily. Making use of an implicit mesh discontinuous Galerkin framework, developed in tandem with this work,more » high-order results are demonstrated, including surface tension dynamics in which fluid velocity, pressure, and interface geometry are computed with fourth-order spatial accuracy in the maximum norm. Applications are demonstrated with two-phase fluid flow displaying fine-scaled capillary wave dynamics, rigid body fluid-structure interaction, and a fluid-jet free surface flow problem exhibiting vortex shedding induced by a type of Plateau-Rayleigh instability. The developed methods can be generalized to other types of interfacial flow and facilitate precise computation of complex fluid interface phenomena.« less

Analyses of ACPL thermal/fluid conditioning system

NASA Technical Reports Server (NTRS)

Stephen, L. A.; Usher, L. H.

1976-01-01

Results of engineering analyses are reported. Initial computations were made using a modified control transfer function where the systems performance was characterized parametrically using an analytical model. The analytical model was revised to represent the latest expansion chamber fluid manifold design, and systems performance predictions were made. Parameters which were independently varied in these computations are listed. Systems predictions which were used to characterize performance are primarily transient computer plots comparing the deviation between average chamber temperature and the chamber temperature requirement. Additional computer plots were prepared. Results of parametric computations with the latest fluid manifold design are included.

Analysis of Flowfields over Four-Engine DC-X Rockets

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Cornelison, Joni

1996-01-01

The objective of this study is to validate a computational methodology for the aerodynamic performance of an advanced conical launch vehicle configuration. The computational methodology is based on a three-dimensional, viscous flow, pressure-based computational fluid dynamics formulation. Both wind-tunnel and ascent flight-test data are used for validation. Emphasis is placed on multiple-engine power-on effects. Computational characterization of the base drag in the critical subsonic regime is the focus of the validation effort; until recently, almost no multiple-engine data existed for a conical launch vehicle configuration. Parametric studies using high-order difference schemes are performed for the cold-flow tests, whereas grid studies are conducted for the flight tests. The computed vehicle axial force coefficients, forebody, aftbody, and base surface pressures compare favorably with those of tests. The results demonstrate that with adequate grid density and proper distribution, a high-order difference scheme, finite rate afterburning kinetics to model the plume chemistry, and a suitable turbulence model to describe separated flows, plume/air mixing, and boundary layers, computational fluid dynamics is a tool that can be used to predict the low-speed aerodynamic performance for rocket design and operations.

Computational Predictions of the Performance Wright 'Bent End' Propellers

NASA Technical Reports Server (NTRS)

Wang, Xiang-Yu; Ash, Robert L.; Bobbitt, Percy J.; Prior, Edwin (Technical Monitor)

2002-01-01

Computational analysis of two 1911 Wright brothers 'Bent End' wooden propeller reproductions have been performed and compared with experimental test results from the Langley Full Scale Wind Tunnel. The purpose of the analysis was to check the consistency of the experimental results and to validate the reliability of the tests. This report is one part of the project on the propeller performance research of the Wright 'Bent End' propellers, intend to document the Wright brothers' pioneering propeller design contributions. Two computer codes were used in the computational predictions. The FLO-MG Navier-Stokes code is a CFD (Computational Fluid Dynamics) code based on the Navier-Stokes Equations. It is mainly used to compute the lift coefficient and the drag coefficient at specified angles of attack at different radii. Those calculated data are the intermediate results of the computation and a part of the necessary input for the Propeller Design Analysis Code (based on Adkins and Libeck method), which is a propeller design code used to compute the propeller thrust coefficient, the propeller power coefficient and the propeller propulsive efficiency.

Computer simulation of the effect of dDAVP with saline loading on fluid balance after 24-hour head-down tilt

NASA Technical Reports Server (NTRS)

Srinivasan, R. S.; Simanonok, K. E.; Charles, J. B.

1994-01-01

Fluid loading (FL) before Shuttle reentry is a countermeasure currently in use by NASA to improve the orthostatic tolerance of astronauts during reentry and postflight. The fluid load consists of water and salt tablets equivalent to 32 oz (946 ml) of isotonic saline. However, the effectiveness of this countermeasure has been observed to decrease with the duration of spaceflight. The countermeasure's effectiveness may be improved by enhancing fluid retention using analogs of vasopressin such as lypressin (LVP) and desmopressin (dDAVP). In a computer simulation study reported previously, we attempted to assess the improvement in fluid retention obtained by the use of LVP administered before FL. The present study is concerned with the use of dDAVP. In a recent 24-hour, 6 degree head-down tilt (HDT) study involving seven men, dDAVP was found to improve orthostatic tolerance as assessed by both lower body negative pressure (LBNP) and stand tests. The treatment restored Luft's cumulative stress index (cumulative product of magnitude and duration of LBNP) to nearly pre-bedrest level. The heart rate was lower and stroke volume was marginally higher at the same LBNP levels with administration of dDAVP compared to placebo. Lower heart rates were also observed with dDAVP during stand test, despite the lower level of cardiovascular stress. These improvements were seen with only a small but significant increase in plasma volume of approximately 3 percent. This paper presents a computer simulation analysis of some of the results of this HDT study.

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

A CFD/CSD Interaction Methodology for Aircraft Wings

NASA Technical Reports Server (NTRS)

Bhardwaj, Manoj K.

1997-01-01

With advanced subsonic transports and military aircraft operating in the transonic regime, it is becoming important to determine the effects of the coupling between aerodynamic loads and elastic forces. Since aeroelastic effects can contribute significantly to the design of these aircraft, there is a strong need in the aerospace industry to predict these aero-structure interactions computationally. To perform static aeroelastic analysis in the transonic regime, high fidelity computational fluid dynamics (CFD) analysis tools must be used in conjunction with high fidelity computational structural fluid dynamics (CSD) analysis tools due to the nonlinear behavior of the aerodynamics in the transonic regime. There is also a need to be able to use a wide variety of CFD and CSD tools to predict these aeroelastic effects in the transonic regime. Because source codes are not always available, it is necessary to couple the CFD and CSD codes without alteration of the source codes. In this study, an aeroelastic coupling procedure is developed which will perform static aeroelastic analysis using any CFD and CSD code with little code integration. The aeroelastic coupling procedure is demonstrated on an F/A-18 Stabilator using NASTD (an in-house McDonnell Douglas CFD code) and NASTRAN. In addition, the Aeroelastic Research Wing (ARW-2) is used for demonstration of the aeroelastic coupling procedure by using ENSAERO (NASA Ames Research Center CFD code) and a finite element wing-box code (developed as part of this research).

System and method measuring fluid flow in a conduit

DOEpatents

Ortiz, Marcos German; Kidd, Terrel G.

1999-01-01

A system for measuring fluid mass flow in a conduit in which there exists a pressure differential in the fluid between at least two spaced-apart locations in the conduit. The system includes a first pressure transducer disposed in the side of the conduit at a first location for measuring pressure of fluid at that location, a second or more pressure transducers disposed in the side of the conduit at a second location, for making multiple measurements of pressure of fluid in the conduit at that location, and a computer for computing the average pressure of the multiple measurements at the second location and for computing flow rate of fluid in the conduit from the pressure measurement by the first pressure transducer and from the average pressure calculation of the multiple measurements.

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.

Exploring a Multiphysics Resolution Approach for Additive Manufacturing

NASA Astrophysics Data System (ADS)

Estupinan Donoso, Alvaro Antonio; Peters, Bernhard

2018-06-01

Metal additive manufacturing (AM) is a fast-evolving technology aiming to efficiently produce complex parts while saving resources. Worldwide, active research is being performed to solve the existing challenges of this growing technique. Constant computational advances have enabled multiscale and multiphysics numerical tools that complement the traditional physical experimentation. In this contribution, an advanced discrete-continuous concept is proposed to address the physical phenomena involved during laser powder bed fusion. The concept treats powder as discrete by the extended discrete element method, which predicts the thermodynamic state and phase change for each particle. The fluid surrounding is solved with multiphase computational fluid dynamics techniques to determine momentum, heat, gas and liquid transfer. Thus, results track the positions and thermochemical history of individual particles in conjunction with the prevailing fluid phases' temperature and composition. It is believed that this methodology can be employed to complement experimental research by analysis of the comprehensive results, which can be extracted from it to enable AM processes optimization for parts qualification.

Analysis of solid particles falling down and interacting in a channel with sedimentation using fictitious boundary method

NASA Astrophysics Data System (ADS)

Usman, K.; Walayat, K.; Mahmood, R.; Kousar, N.

2018-06-01

We have examined the behavior of solid particles in particulate flows. The interaction of particles with each other and with the fluid is analyzed. Solid particles can move freely through a fixed computational mesh using an Eulerian approach. Fictitious boundary method (FBM) is used for treating the interaction between particles and the fluid. Hydrodynamic forces acting on the particle's surface are calculated using an explicit volume integral approach. A collision model proposed by Glowinski, Singh, Joseph and coauthors is used to handle particle-wall and particle-particle interactions. The particulate flow is computed using multigrid finite element solver FEATFLOW. Numerical experiments are performed considering two particles falling and colliding and sedimentation of many particles while interacting with each other. Results for these experiments are presented and compared with the reference values. Effects of the particle-particle interaction on the motion of the particles and on the physical behavior of the fluid-particle system has been analyzed.

Description and detection of burst events in turbulent flows

NASA Astrophysics Data System (ADS)

Schmid, P. J.; García-Gutierrez, A.; Jiménez, J.

2018-04-01

A mathematical and computational framework is developed for the detection and identification of coherent structures in turbulent wall-bounded shear flows. In a first step, this data-based technique will use an embedding methodology to formulate the fluid motion as a phase-space trajectory, from which state-transition probabilities can be computed. Within this formalism, a second step then applies repeated clustering and graph-community techniques to determine a hierarchy of coherent structures ranked by their persistencies. This latter information will be used to detect highly transitory states that act as precursors to violent and intermittent events in turbulent fluid motion (e.g., bursts). Used as an analysis tool, this technique allows the objective identification of intermittent (but important) events in turbulent fluid motion; however, it also lays the foundation for advanced control strategies for their manipulation. The techniques are applied to low-dimensional model equations for turbulent transport, such as the self-sustaining process (SSP), for varying levels of complexity.

Influence of mechanical rock properties and fracture healing rate on crustal fluid flow dynamics

NASA Astrophysics Data System (ADS)

Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel; de Riese, Tamara

2016-04-01

Fluid flow in the Earth's crust is very slow over extended periods of time, during which it occurs within the connected pore space of rocks. If the fluid production rate exceeds a certain threshold, matrix permeability alone is insufficient to drain the fluid volume and fluid pressure builds up, thereby reducing the effective stress supported by the rock matrix. Hydraulic fractures form once the effective pressure exceeds the tensile strength of the rock matrix and act subsequently as highly effective fluid conduits. Once local fluid pressure is sufficiently low again, flow ceases and fractures begin to heal. Since fluid flow is controlled by the alternation of fracture permeability and matrix permeability, the flow rate in the system is strongly discontinuous and occurs in intermittent pulses. Resulting hydraulic fracture networks are largely self-organized: opening and subsequent healing of hydraulic fractures depends on the local fluid pressure and on the time-span between fluid pulses. We simulate this process with a computer model and describe the resulting dynamics statistically. Special interest is given to a) the spatially and temporally discontinuous formation and closure of fractures and fracture networks and b) the total flow rate over time. The computer model consists of a crustal-scale dual-porosity setup. Control parameters are the pressure- and time-dependent fracture healing rate, and the strength and the permeability of the intact rock. Statistical analysis involves determination of the multifractal properties and of the power spectral density of the temporal development of the total drainage rate and hydraulic fractures. References Bons, P. D. (2001). The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures. Tectonophysics, 336, 1-17. Miller, S. a., & Nur, A. (2000). Permeability as a toggle switch in fluid-controlled crustal processes. Earth and Planetary Science Letters, 183(1-2), 133-146. Sachau, T., Bons, P. D., & Gomez-Rivas, E. (2015). Transport efficiency and dynamics of hydraulic fracture networks. Frontiers in Physics, 3.

Computer program for computing the properties of seventeen fluids. [cryogenic liquids

NASA Technical Reports Server (NTRS)

Brennan, J. A.; Friend, D. G.; Arp, V. D.; Mccarty, R. D.

1992-01-01

The present study describes modifications and additions to the MIPROPS computer program for calculating the thermophysical properties of 17 fluids. These changes include adding new fluids, new properties, and a new interface to the program. The new program allows the user to select the input and output parameters and the units to be displayed for each parameter. Fluids added to the MIPROPS program are carbon dioxide, carbon monoxide, deuterium, helium, normal hydrogen, and xenon. The most recent modifications to the MIPROPS program are the addition of viscosity and thermal conductivity correlations for parahydrogen and the addition of the fluids normal hydrogen and xenon. The recently added interface considerably increases the program's utility.

Substellar fragmentation in self-gravitating fluids with a major phase transition

NASA Astrophysics Data System (ADS)

Füglistaler, A.; Pfenniger, D.

2015-06-01

Context. The observation of various ices in cold molecular clouds, the existence of ubiquitous substellar, cold H2 globules in planetary nebulae and supernova remnants, or the mere existence of comets suggest that the physics of very cold interstellar gas might be much richer than usually envisioned. At the extreme of low temperatures (≲10 K), H2 itself is subject to a phase transition crossing the entire cosmic gas density scale. Aims: This well-known, laboratory-based fact motivates us to study the ideal case of a cold neutral gaseous medium in interstellar conditions for which the bulk of the mass, instead of trace elements, is subject to a gas-liquid or gas-solid phase transition. Methods: On the one hand, the equilibrium of general non-ideal fluids is studied using the virial theorem and linear stability analysis. On the other hand, the non-linear dynamics is studied using computer simulations to characterize the expected formation of solid bodies analogous to comets. The simulations are run with a state-of-the-art molecular dynamics code (LAMMPS) using the Lennard-Jones inter-molecular potential. The long-range gravitational forces can be taken into account together with short-range molecular forces with finite limited computational resources, using super-molecules, provided the right scaling is followed. Results: The concept of super-molecule, where the phase transition conditions are preserved by the proper choice of the particle parameters, is tested with computer simulations, allowing us to correctly satisfy the Jeans instability criterion for one-phase fluids. The simulations show that fluids presenting a phase transition are gravitationally unstable as well, independent of the strength of the gravitational potential, producing two distinct kinds of substellar bodies, those dominated by gravity (planetoids) and those dominated by molecular attractive force (comets). Conclusions: Observations, formal analysis, and computer simulations suggest the possibility of the formation of substellar H2 clumps in cold molecular clouds due to the combination of phase transition and gravity. Fluids presenting a phase transition are gravitationally unstable, independent of the strength of the gravitational potential. Arbitrarily small H2 clumps may form even at relatively high temperatures up to 400-600 K, according to virial analysis. The combination of phase transition and gravity may be relevant for a wider range of astrophysical situations, such as proto-planetary disks. Figures 33-44 are available in electronic form at http://www.aanda.org

Use of Generalized Fluid System Simulation Program (GFSSP) for Teaching and Performing Senior Design Projects at the Educational Institutions

NASA Technical Reports Server (NTRS)

Majumdar, A. K.; Hedayat, A.

2015-01-01

This paper describes the experience of the authors in using the Generalized Fluid System Simulation Program (GFSSP) in teaching Design of Thermal Systems class at University of Alabama in Huntsville. GFSSP is a finite volume based thermo-fluid system network analysis code, developed at NASA/Marshall Space Flight Center, and is extensively used in NASA, Department of Defense, and aerospace industries for propulsion system design, analysis, and performance evaluation. The educational version of GFSSP is freely available to all US higher education institutions. The main purpose of the paper is to illustrate the utilization of this user-friendly code for the thermal systems design and fluid engineering courses and to encourage the instructors to utilize the code for the class assignments as well as senior design projects. The need for a generalized computer program for thermofluid analysis in a flow network has been felt for a long time in aerospace industries. Designers of thermofluid systems often need to know pressures, temperatures, flow rates, concentrations, and heat transfer rates at different parts of a flow circuit for steady state or transient conditions. Such applications occur in propulsion systems for tank pressurization, internal flow analysis of rocket engine turbopumps, chilldown of cryogenic tanks and transfer lines, and many other applications of gas-liquid systems involving fluid transients and conjugate heat and mass transfer. Computer resource requirements to perform time-dependent, three-dimensional Navier-Stokes computational fluid dynamic (CFD) analysis of such systems are prohibitive and therefore are not practical. Available commercial codes are generally suitable for steady state, single-phase incompressible flow. Because of the proprietary nature of such codes, it is not possible to extend their capability to satisfy the above-mentioned needs. Therefore, the Generalized Fluid System Simulation Program (GFSSP1) has been developed at NASA Marshall Space Flight Center (MSFC) as a general fluid flow system solver capable of handling phase changes, compressibility, mixture thermodynamics and transient operations. It also includes the capability to model external body forces such as gravity and centrifugal effects in a complex flow network. The objectives of GFSSP development are: a) to develop a robust and efficient numerical algorithm to solve a system of equations describing a flow network containing phase changes, mixing, and rotation; and b) to implement the algorithm in a structured, easy-to-use computer program. The analysis of thermofluid dynamics in a complex network requires resolution of the system into fluid nodes and branches, and solid nodes and conductors as shown in Figure 1. Figure 1 shows a schematic and GFSSP flow circuit of a counter-flow heat exchanger. Hot nitrogen gas is flowing through a pipe, colder nitrogen is flowing counter to the hot stream in the annulus pipe and heat transfer occurs through metal tubes. The problem considered is to calculate flowrates and temperature distributions in both streams. GFSSP has a unique data structure, as shown in Figure 2, that allows constructing all possible arrangements of a flow network with no limit on the number of elements. The elements of a flow network are boundary nodes where pressure and temperature are specified, internal nodes where pressure and temperature are calculated, and branches where flowrates are calculated. For conjugate heat transfer problems, there are three additional elements: solid node, ambient node, and conductor. The solid and fluid nodes are connected with solid-fluid conductors. GFSSP solves the conservation equations of mass and energy, and equation of state in internal nodes to calculate pressure, temperature and resident mass. The momentum conservation equation is solved in branches to calculate flowrate. It also solves for energy conservation equations to calculate temperatures of solid nodes. The equations are coupled and nonlinear; therefore, they are solved by an iterative numerical scheme. GFSSP employs a unique numerical scheme known as simultaneous adjustment with successive substitution (SASS), which is a combination of Newton-Raphson and successive substitution methods. The mass and momentum conservation equations and the equation of state are solved by the Newton-Raphson method while the conservation of energy and species are solved by the successive substitution method. GFSSP is linked with two thermodynamic property programs, GASP2 and WASP3 and GASPAK4, that provide thermodynamic and thermophysical properties of selected fluids. Both programs cover a range of pressure and temperature that allows fluid properties to be evaluated for liquid, liquid-vapor (saturation), and vapor region. GASP and WASP provide properties of 12 fluids. GASPAK includes a library of 36 fluids. GFSSP has three major parts. The first part is the graphical user interface (GUI), visual thermofluid analyzer of systems and components (VTASC). VTASC allows users to create a flow circuit by a 'point and click' paradigm. It creates the GFSSP input file after the completion of the model building process. GFSSP's GUI provides the users a platform to build and run their models. It also allows post-processing of results. The network flow circuit is first built using three basic elements: boundary node, internal node, and branch.

3D MR flow analysis in realistic rapid-prototyping model systems of the thoracic aorta: comparison with in vivo data and computational fluid dynamics in identical vessel geometries.

PubMed

Canstein, C; Cachot, P; Faust, A; Stalder, A F; Bock, J; Frydrychowicz, A; Küffer, J; Hennig, J; Markl, M

2008-03-01

The knowledge of local vascular anatomy and function in the human body is of high interest for the diagnosis and treatment of cardiovascular disease. A comprehensive analysis of the hemodynamics in the thoracic aorta is presented based on the integration of flow-sensitive 4D MRI with state-of-the-art rapid prototyping technology and computational fluid dynamics (CFD). Rapid prototyping was used to transform aortic geometries as measured by contrast-enhanced MR angiography into realistic vascular models with large anatomical coverage. Integration into a flow circuit with patient-specific pulsatile in-flow conditions and application of flow-sensitive 4D MRI permitted detailed analysis of local and global 3D flow dynamics in a realistic vascular geometry. Visualization of characteristic 3D flow patterns and quantitative comparisons of the in vitro experiments with in vivo data and CFD simulations in identical vascular geometries were performed to evaluate the accuracy of vascular model systems. The results indicate the potential of such patient-specific model systems for detailed experimental simulation of realistic vascular hemodynamics. Further studies are warranted to examine the influence of refined boundary conditions of the human circulatory system such as fluid-wall interaction and their effect on normal and pathological blood flow characteristics associated with vascular geometry. (c) 2008 Wiley-Liss, Inc.

New Computational Methods for the Prediction and Analysis of Helicopter Noise

NASA Technical Reports Server (NTRS)

Strawn, Roger C.; Oliker, Leonid; Biswas, Rupak

1996-01-01

This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise.

Tensor methodology and computational geometry in direct computational experiments in fluid mechanics

NASA Astrophysics Data System (ADS)

Degtyarev, Alexander; Khramushin, Vasily; Shichkina, Julia

2017-07-01

The paper considers a generalized functional and algorithmic construction of direct computational experiments in fluid dynamics. Notation of tensor mathematics is naturally embedded in the finite - element operation in the construction of numerical schemes. Large fluid particle, which have a finite size, its own weight, internal displacement and deformation is considered as an elementary computing object. Tensor representation of computational objects becomes strait linear and uniquely approximation of elementary volumes and fluid particles inside them. The proposed approach allows the use of explicit numerical scheme, which is an important condition for increasing the efficiency of the algorithms developed by numerical procedures with natural parallelism. It is shown that advantages of the proposed approach are achieved among them by considering representation of large particles of a continuous medium motion in dual coordinate systems and computing operations in the projections of these two coordinate systems with direct and inverse transformations. So new method for mathematical representation and synthesis of computational experiment based on large particle method is proposed.

Analysis of Flow Migration in an Ultra-Compact Combustor

DTIC Science & Technology

2011-03-01

Computational Fluid Dynamics . . . . . . . . . . . . . . . 6 UNICORN Unsteady Ignition and Combustion with Reactions . . . . 8 LBO Lean Blowout...the magnitude of enhanced flame speeds due to g- loading using the UNICORN CFD code. The study examined flame propagation for a hydrogen-air mixture in

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...

Least Squares Shadowing Sensitivity Analysis of Chaotic Flow Around a Two-Dimensional Airfoil

NASA Technical Reports Server (NTRS)

Blonigan, Patrick J.; Wang, Qiqi; Nielsen, Eric J.; Diskin, Boris

2016-01-01

Gradient-based sensitivity analysis has proven to be an enabling technology for many applications, including design of aerospace vehicles. However, conventional sensitivity analysis methods break down when applied to long-time averages of chaotic systems. This breakdown is a serious limitation because many aerospace applications involve physical phenomena that exhibit chaotic dynamics, most notably high-resolution large-eddy and direct numerical simulations of turbulent aerodynamic flows. A recently proposed methodology, Least Squares Shadowing (LSS), avoids this breakdown and advances the state of the art in sensitivity analysis for chaotic flows. The first application of LSS to a chaotic flow simulated with a large-scale computational fluid dynamics solver is presented. The LSS sensitivity computed for this chaotic flow is verified and shown to be accurate, but the computational cost of the current LSS implementation is high.

A novel potential/viscous flow coupling technique for computing helicopter flow fields

NASA Technical Reports Server (NTRS)

Summa, J. Michael; Strash, Daniel J.; Yoo, Sungyul

1990-01-01

Because of the complexity of helicopter flow field, a zonal method of analysis of computational aerodynamics is required. Here, a new procedure for coupling potential and viscous flow is proposed. An overlapping, velocity coupling technique is to be developed with the unique feature that the potential flow surface singularity strengths are obtained directly from the Navier-Stokes at a smoother inner fluid boundary. The closed-loop iteration method proceeds until the velocity field is converged. This coupling should provide the means of more accurate viscous computations of the near-body and rotor flow fields with resultant improved analysis of such important performance parameters as helicopter fuselage drag and rotor airloads.

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.

Spectral analysis of the turbulent mixing of two fluids

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

Steinkamp, M.J.

1996-02-01

The authors describe a spectral approach to the investigation of fluid instability, generalized turbulence, and the interpenetration of fluids across an interface. The technique also applies to a single fluid with large variations in density. Departures of fluctuating velocity components from the local mean are far subsonic, but the mean Mach number can be large. Validity of the description is demonstrated by comparisons with experiments on turbulent mixing due to the late stages of Rayleigh-Taylor instability, when the dynamics become approximately self-similar in response to a constant body force. Generic forms for anisotropic spectral structure are described and used asmore » a basis for deriving spectrally integrated moment equations that can be incorporated into computer codes for scientific and engineering analyses.« less

Finite element analysis in fluids; Proceedings of the Seventh International Conference on Finite Element Methods in Flow Problems, University of Alabama, Huntsville, Apr. 3-7, 1989

NASA Technical Reports Server (NTRS)

Chung, T. J. (Editor); Karr, Gerald R. (Editor)

1989-01-01

Recent advances in computational fluid dynamics are examined in reviews and reports, with an emphasis on finite-element methods. Sections are devoted to adaptive meshes, atmospheric dynamics, combustion, compressible flows, control-volume finite elements, crystal growth, domain decomposition, EM-field problems, FDM/FEM, and fluid-structure interactions. Consideration is given to free-boundary problems with heat transfer, free surface flow, geophysical flow problems, heat and mass transfer, high-speed flow, incompressible flow, inverse design methods, MHD problems, the mathematics of finite elements, and mesh generation. Also discussed are mixed finite elements, multigrid methods, non-Newtonian fluids, numerical dissipation, parallel vector processing, reservoir simulation, seepage, shallow-water problems, spectral methods, supercomputer architectures, three-dimensional problems, and turbulent flows.

MHD Convective Flow of Jeffrey Fluid Due to a Curved Stretching Surface with Homogeneous-Heterogeneous Reactions

PubMed Central

Imtiaz, Maria; Hayat, Tasawar; Alsaedi, Ahmed

2016-01-01

This paper looks at the flow of Jeffrey fluid due to a curved stretching sheet. Effect of homogeneous-heterogeneous reactions is considered. An electrically conducting fluid in the presence of applied magnetic field is considered. Convective boundary conditions model the heat transfer analysis. Transformation method reduces the governing nonlinear partial differential equations into the ordinary differential equations. Convergence of the obtained series solutions is explicitly discussed. Characteristics of sundry parameters on the velocity, temperature and concentration profiles are analyzed by plotting graphs. Computations for pressure, skin friction coefficient and surface heat transfer rate are presented and examined. It is noted that fluid velocity and temperature through curvature parameter are enhanced. Increasing values of Biot number correspond to the enhancement in temperature and Nusselt number. PMID:27583457

Modeling Potential Carbon Monoxide Exposure Due to Operation of a Major Rocket Engine Altitude Test Facility Using Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Blotzer, Michael J.; Woods, Jody L.

2009-01-01

This viewgraph presentation reviews computational fluid dynamics as a tool for modelling the dispersion of carbon monoxide at the Stennis Space Center's A3 Test Stand. The contents include: 1) Constellation Program; 2) Constellation Launch Vehicles; 3) J2X Engine; 4) A-3 Test Stand; 5) Chemical Steam Generators; 6) Emission Estimates; 7) Located in Existing Test Complex; 8) Computational Fluid Dynamics; 9) Computational Tools; 10) CO Modeling; 11) CO Model results; and 12) Next steps.

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.

Apparatus for and Method of Monitoring Condensed Water in Steam Pipes at High Temperature

NASA Technical Reports Server (NTRS)

Lih, Shyh-Shiuh (Inventor); Bao, Xiaoqi (Inventor); Bar-Cohen, Yoseph (Inventor); Lee, Hyeong Jae (Inventor)

2016-01-01

A system and method for monitoring the properties of a fluid, such as water, in a steam pipe without mechanically penetrating the wall of the pipe. The system uses a piezoelectric transducer to launch an ultrasonic probe signal into the pipe. Reflected ultrasonic signals are captured in a transducer, which can be the same transducer that launched the probe signal. The reflected signals are subjected to data processing, which can include filtering, amplification, analog-to-digital conversion and autocorrelation analysis. A result is extracted which is indicative of a property of the fluid, such as a height of the condensed fluid, a cavitation of the condensed fluid, and a surface perturbation of the condensed fluid. The result can be recorded, displayed, and/or transmitted to another location. One embodiment of the system has been constructed and tested based on a general purpose programmable computer using instructions recorded in machine-readable non-volatile memory.

In-Service Monitoring of Steam Pipe Systems at High Temperatures

NASA Technical Reports Server (NTRS)

Sherrit, Stewart (Inventor); Scott, James Samson (Inventor); Bar-Cohen, Yoseph (Inventor); Badescu, Mircea (Inventor); Widholm, Scott E. (Inventor); Lih, Shyh-Shiuh (Inventor); Bao, Xiaoqi (Inventor); Blosiu, Julian O. (Inventor)

2014-01-01

A system and method for monitoring the properties of a fluid, such as water, in a steam pipe without mechanically penetrating the wall of the pipe. The system uses a piezoelectric transducer to launch an ultrasonic probe signal into the pipe. Reflected ultrasonic signals are captured in a transducer, which can be the same transducer that launched the probe signal. The reflected signals are subjected to data processing, which can include filtering, amplification, analog-to-digital conversion and autocorrelation analysis. A result is extracted which is indicative of a property of the fluid, such as a height of the condensed fluid, a cavitation of the condensed fluid, and a surface perturbation of the condensed fluid. The result can be recorded, displayed, and/or transmitted to another location. One embodiment of the system has been constructed and tested based on a general purpose programmable computer using instructions recorded in machine-readable non-volatile memory.

Numerical Stability and Control Analysis Towards Falling-Leaf Prediction Capabilities of Splitflow for Two Generic High-Performance Aircraft Models

NASA Technical Reports Server (NTRS)

Charlton, Eric F.

1998-01-01

Aerodynamic analysis are performed using the Lockheed-Martin Tactical Aircraft Systems (LMTAS) Splitflow computational fluid dynamics code to investigate the computational prediction capabilities for vortex-dominated flow fields of two different tailless aircraft models at large angles of attack and sideslip. These computations are performed with the goal of providing useful stability and control data to designers of high performance aircraft. Appropriate metrics for accuracy, time, and ease of use are determined in consultations with both the LMTAS Advanced Design and Stability and Control groups. Results are obtained and compared to wind-tunnel data for all six components of forces and moments. Moment data is combined to form a "falling leaf" stability analysis. Finally, a handful of viscous simulations were also performed to further investigate nonlinearities and possible viscous effects in the differences between the accumulated inviscid computational and experimental data.

A scalable nonlinear fluid-structure interaction solver based on a Schwarz preconditioner with isogeometric unstructured coarse spaces in 3D

NASA Astrophysics Data System (ADS)

Kong, Fande; Cai, Xiao-Chuan

2017-07-01

Nonlinear fluid-structure interaction (FSI) problems on unstructured meshes in 3D appear in many applications in science and engineering, such as vibration analysis of aircrafts and patient-specific diagnosis of cardiovascular diseases. In this work, we develop a highly scalable, parallel algorithmic and software framework for FSI problems consisting of a nonlinear fluid system and a nonlinear solid system, that are coupled monolithically. The FSI system is discretized by a stabilized finite element method in space and a fully implicit backward difference scheme in time. To solve the large, sparse system of nonlinear algebraic equations at each time step, we propose an inexact Newton-Krylov method together with a multilevel, smoothed Schwarz preconditioner with isogeometric coarse meshes generated by a geometry preserving coarsening algorithm. Here "geometry" includes the boundary of the computational domain and the wet interface between the fluid and the solid. We show numerically that the proposed algorithm and implementation are highly scalable in terms of the number of linear and nonlinear iterations and the total compute time on a supercomputer with more than 10,000 processor cores for several problems with hundreds of millions of unknowns.

Deformation and breakup of liquid-liquid threads, jets, and drops

NASA Astrophysics Data System (ADS)

Doshi, Pankaj

The formation and breakup of two-fluid jets and drops find application in various industrially important processes like microencapsulation, inkjet printing, dispersion and emulsion formation, micro fluidics. Two important aspects of these problems are studied in this thesis. The first regards the study of the dynamics of a two-fluid jet issuing out of a concentric nozzle and breaking into multiple liquid drops. The second aspect concerns the study of the dynamics of liquid-liquid interface rupture. Highly robust and accurate numerical algorithms based on the Galerkin finite element method (G/FEM) and elliptic mesh generation technique are developed. The most important results of this research are the prediction of compound drop formation and volume partitioning between primary drop and satellite drops, which are of critical importance for microencapsulation technology. Another equally important result is computational and experimental demonstration of a self-similar behavior for the rupture of liquid-liquid interface. The final focus is the study of the pinch-off dynamics of generalized-Newtonian fluids with deformation-rate-dependent rheology using asymptotic analysis and numerical computation. A significant result is the first ever prediction of self-similar pinch-off of liquid threads of generalized Newtonian fluids.

Strongly Coupled Fluid-Body Dynamics in the Immersed Boundary Projection Method

NASA Astrophysics Data System (ADS)

Wang, Chengjie; Eldredge, Jeff D.

2014-11-01

A computational algorithm is developed to simulate dynamically coupled interaction between fluid and rigid bodies. The basic computational framework is built upon a multi-domain immersed boundary method library, whirl, developed in previous work. In this library, the Navier-Stokes equations for incompressible flow are solved on a uniform Cartesian grid by the vorticity-based immersed boundary projection method of Colonius and Taira. A solver for the dynamics of rigid-body systems is also included. The fluid and rigid-body solvers are strongly coupled with an iterative approach based on the block Gauss-Seidel method. Interfacial force, with its intimate connection with the Lagrange multipliers used in the fluid solver, is used as the primary iteration variable. Relaxation, developed from a stability analysis of the iterative scheme, is used to achieve convergence in only 2-4 iterations per time step. Several two- and three-dimensional numerical tests are conducted to validate and demonstrate the method, including flapping of flexible wings, self-excited oscillations of a system of linked plates and three-dimensional propulsion of flexible fluked tail. This work has been supported by AFOSR, under Award FA9550-11-1-0098.

Variability of hemodynamic parameters using the common viscosity assumption in a computational fluid dynamics analysis of intracranial aneurysms.

PubMed

Suzuki, Takashi; Takao, Hiroyuki; Suzuki, Takamasa; Suzuki, Tomoaki; Masuda, Shunsuke; Dahmani, Chihebeddine; Watanabe, Mitsuyoshi; Mamori, Hiroya; Ishibashi, Toshihiro; Yamamoto, Hideki; Yamamoto, Makoto; Murayama, Yuichi

2017-01-01

In most simulations of intracranial aneurysm hemodynamics, blood is assumed to be a Newtonian fluid. However, it is a non-Newtonian fluid, and its viscosity profile differs among individuals. Therefore, the common viscosity assumption may not be valid for all patients. This study aims to test the suitability of the common viscosity assumption. Blood viscosity datasets were obtained from two healthy volunteers. Three simulations were performed for three different-sized aneurysms, two using measured value-based non-Newtonian models and one using a Newtonian model. The parameters proposed to predict an aneurysmal rupture obtained using the non-Newtonian models were compared with those obtained using the Newtonian model. The largest difference (25%) in the normalized wall shear stress (NWSS) was observed in the smallest aneurysm. Comparing the difference ratio to the NWSS with the Newtonian model between the two Non-Newtonian models, the difference of the ratio was 17.3%. Irrespective of the aneurysmal size, computational fluid dynamics simulations with either the common Newtonian or non-Newtonian viscosity assumption could lead to values different from those of the patient-specific viscosity model for hemodynamic parameters such as NWSS.

Parallel computational fluid dynamics '91; Conference Proceedings, Stuttgart, Germany, Jun. 10-12, 1991

NASA Technical Reports Server (NTRS)

Reinsch, K. G. (Editor); Schmidt, W. (Editor); Ecer, A. (Editor); Haeuser, Jochem (Editor); Periaux, J. (Editor)

1992-01-01

A conference was held on parallel computational fluid dynamics and produced related papers. Topics discussed in these papers include: parallel implicit and explicit solvers for compressible flow, parallel computational techniques for Euler and Navier-Stokes equations, grid generation techniques for parallel computers, and aerodynamic simulation om massively parallel systems.

A Computational Investigation for Determining the Natural Frequencies and Damping Effects of Diaphragm-Implemented Spacecraft Propellant Tanks

NASA Technical Reports Server (NTRS)

Lenahen, Brian; Bernier, Adrien; Gangadharan, Sathya; Sudermann, James; Marsell, Brandon

2012-01-01

Spin-stabilization maneuvers are typically performed by spacecraft entering low-earth orbit to maintain attitude stability. These maneuvers induce periodic fluid movement inside the spacecraft's propellant tank known as fuel slosh, which is responsible for creating forces and moments on the sidewalls of the propellant tank. These forces and moments adversely affect spin-stabilization and risk jeopardizing the mission of the spacecraft. Therefore, propellant tanks are designed with propellant management devices (PMD's) such as barnes or diaphragms which work to counteract the forces and moments associated with fuel slosh. However, despite the presence of PMD's, the threat of spin-stabilization interference still exists should the propellant tank be excited at its natural frequency. When the fluid is excited at its natural frequency, the forces and moments acting on the propellant tank are amplified and may result in destabilizing the spacecraft. Thus, a computational analysis is conducted concerning diaphragm-implemented propellant tanks excited at their natural frequencies. Using multi-disciplinary computational fluid dynamics (CFD) software, computational models are developed to reflect potential scenarios that spacecraft propellant tanks could experience. By simulating the propellant tank under a wide array of parameters and variables including fill-level, gravity and diaphragm material and shape, a better understanding is gained as to how these parameters individually and collectively affect liquid propellant tanks and ultimately, spacecraft attitude dynamics.

A ferrofluid based energy harvester: Computational modeling, analysis, and experimental validation

NASA Astrophysics Data System (ADS)

Liu, Qi; Alazemi, Saad F.; Daqaq, Mohammed F.; Li, Gang

2018-03-01

A computational model is described and implemented in this work to analyze the performance of a ferrofluid based electromagnetic energy harvester. The energy harvester converts ambient vibratory energy into an electromotive force through a sloshing motion of a ferrofluid. The computational model solves the coupled Maxwell's equations and Navier-Stokes equations for the dynamic behavior of the magnetic field and fluid motion. The model is validated against experimental results for eight different configurations of the system. The validated model is then employed to study the underlying mechanisms that determine the electromotive force of the energy harvester. Furthermore, computational analysis is performed to test the effect of several modeling aspects, such as three-dimensional effect, surface tension, and type of the ferrofluid-magnetic field coupling on the accuracy of the model prediction.

Advances in computational design and analysis of airbreathing propulsion systems

NASA Technical Reports Server (NTRS)

Klineberg, John M.

1989-01-01

The development of commercial and military aircraft depends, to a large extent, on engine manufacturers being able to achieve significant increases in propulsion capability through improved component aerodynamics, materials, and structures. The recent history of propulsion has been marked by efforts to develop computational techniques that can speed up the propulsion design process and produce superior designs. The availability of powerful supercomputers, such as the NASA Numerical Aerodynamic Simulator, and the potential for even higher performance offered by parallel computer architectures, have opened the door to the use of multi-dimensional simulations to study complex physical phenomena in propulsion systems that have previously defied analysis or experimental observation. An overview of several NASA Lewis research efforts is provided that are contributing toward the long-range goal of a numerical test-cell for the integrated, multidisciplinary design, analysis, and optimization of propulsion systems. Specific examples in Internal Computational Fluid Mechanics, Computational Structural Mechanics, Computational Materials Science, and High Performance Computing are cited and described in terms of current capabilities, technical challenges, and future research directions.

Cumulative reports and publications

NASA Technical Reports Server (NTRS)

1993-01-01

A complete list of Institute for Computer Applications in Science and Engineering (ICASE) reports are listed. Since ICASE reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available. The major categories of the current ICASE research program are: applied and numerical mathematics, including numerical analysis and algorithm development; theoretical and computational research in fluid mechanics in selected areas of interest to LaRC, including acoustics and combustion; experimental research in transition and turbulence and aerodynamics involving LaRC facilities and scientists; and computer science.

System and method measuring fluid flow in a conduit

DOEpatents

Ortiz, M.G.; Kidd, T.G.

1999-05-18

A system is described for measuring fluid mass flow in a conduit in which there exists a pressure differential in the fluid between at least two spaced-apart locations in the conduit. The system includes a first pressure transducer disposed in the side of the conduit at a first location for measuring pressure of fluid at that location, a second or more pressure transducers disposed in the side of the conduit at a second location, for making multiple measurements of pressure of fluid in the conduit at that location, and a computer for computing the average pressure of the multiple measurements at the second location and for computing flow rate of fluid in the conduit from the pressure measurement by the first pressure transducer and from the average pressure calculation of the multiple measurements. 3 figs.

Posttest analysis of LOFT LOCE L2-3 using the ESA RELAP4 blowdown model. [PWR

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

Perryman, J.L.; Samuels, T.K.; Cooper, C.H.

A posttest analysis of the blowdown portion of Loss-of-Coolant Experiment (LOCE) L2-3, which was conducted in the Loss-of-Fluid Test (LOFT) facility, was performed using the experiment safety analysis (ESA) RELAP4/MOD5 computer model. Measured experimental parameters were compared with the calculations in order to assess the conservatisms in the ESA RELAP4/MOD5 model.

Numerical study of the influence of solid polarization on electrophoresis at finite Debye thickness.

PubMed

Bhattacharyya, Somnath; De, Simanta

2015-09-01

The influence of solid polarization on the electrophoresis of a uniformly charged dielectric particle for finite values of the particle-to-fluid dielectric permittivity ratio is analyzed quantitatively without imposing the thin Debye length or weak-field assumption. Present analysis is based on the computation of the coupled Poisson-Nernst-Planck and Stokes equations in the fluid domain along with the Laplace equation within the solid. The electrophoretic velocity is determined through the balance of forces acting on the particle. The solid polarization of the charged particle produces a reduction on its electrophoretic velocity compared to a nonpolarizable particle of the same surface charge density. In accordance with the existing thin-layer analysis, our computed results for thin Debye layer shows that the solid polarization is important only when the applied electric field is strong. When the Debye length is in the order of the particle size, the electrophoretic velocity decreases with the rise of the particle permittivity and attains a saturation limit at large values of the permittivity. Our computed solution for electrophoretic velocity is in agreement with the existing asymptotic analyses based on a thin Debye layer for limiting cases.

Distributed collaborative probabilistic design of multi-failure structure with fluid-structure interaction using fuzzy neural network of regression

NASA Astrophysics Data System (ADS)

Song, Lu-Kai; Wen, Jie; Fei, Cheng-Wei; Bai, Guang-Chen

2018-05-01

To improve the computing efficiency and precision of probabilistic design for multi-failure structure, a distributed collaborative probabilistic design method-based fuzzy neural network of regression (FR) (called as DCFRM) is proposed with the integration of distributed collaborative response surface method and fuzzy neural network regression model. The mathematical model of DCFRM is established and the probabilistic design idea with DCFRM is introduced. The probabilistic analysis of turbine blisk involving multi-failure modes (deformation failure, stress failure and strain failure) was investigated by considering fluid-structure interaction with the proposed method. The distribution characteristics, reliability degree, and sensitivity degree of each failure mode and overall failure mode on turbine blisk are obtained, which provides a useful reference for improving the performance and reliability of aeroengine. Through the comparison of methods shows that the DCFRM reshapes the probability of probabilistic analysis for multi-failure structure and improves the computing efficiency while keeping acceptable computational precision. Moreover, the proposed method offers a useful insight for reliability-based design optimization of multi-failure structure and thereby also enriches the theory and method of mechanical reliability design.

A cyclostationary multi-domain analysis of fluid instability in Kaplan turbines

NASA Astrophysics Data System (ADS)

Pennacchi, P.; Borghesani, P.; Chatterton, S.

2015-08-01

Hydraulic instabilities represent a critical problem for Francis and Kaplan turbines, reducing their useful life due to increase of fatigue on the components and cavitation phenomena. Whereas an exhaustive list of publications on computational fluid-dynamic models of hydraulic instability is available, the possibility of applying diagnostic techniques based on vibration measurements has not been investigated sufficiently, also because the appropriate sensors seldom equip hydro turbine units. The aim of this study is to fill this knowledge gap and to exploit fully, for this purpose, the potentiality of combining cyclostationary analysis tools, able to describe complex dynamics such as those of fluid-structure interactions, with order tracking procedures, allowing domain transformations and consequently the separation of synchronous and non-synchronous components. This paper will focus on experimental data obtained on a full-scale Kaplan turbine unit, operating in a real power plant, tackling the issues of adapting such diagnostic tools for the analysis of hydraulic instabilities and proposing techniques and methodologies for a highly automated condition monitoring system.

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.

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.

Multiphysics Thermal-Fluid Design Analysis of a Non-Nuclear Tester for Hot-Hydrogen Materials and Component Development

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Foote, John; Litchford, Ron

2006-01-01

The objective of this effort is to perform design analyses for a non-nuclear hot-hydrogen materials tester, as a first step towards developing efficient and accurate multiphysics, thermo-fluid computational methodology to predict environments for hypothetical solid-core, nuclear thermal engine thrust chamber design and analysis. The computational methodology is based on a multidimensional, finite-volume, turbulent, chemically reacting, thermally radiating, unstructured-grid, and pressure-based formulation. The multiphysics invoked in this study include hydrogen dissociation kinetics and thermodynamics, turbulent flow, convective, and thermal radiative heat transfers. The goals of the design analyses are to maintain maximum hot-hydrogen jet impingement energy and to minimize chamber wall heating. The results of analyses on three test fixture configurations and the rationale for final selection are presented. The interrogation of physics revealed that reactions of hydrogen dissociation and recombination are highly correlated with local temperature and are necessary for accurate prediction of the hot-hydrogen jet temperature.

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

Parallel Three-Dimensional Computation of Fluid Dynamics and Fluid-Structure Interactions of Ram-Air Parachutes

NASA Technical Reports Server (NTRS)

Tezduyar, Tayfun E.

1998-01-01

This is a final report as far as our work at University of Minnesota is concerned. The report describes our research progress and accomplishments in development of high performance computing methods and tools for 3D finite element computation of aerodynamic characteristics and fluid-structure interactions (FSI) arising in airdrop systems, namely ram-air parachutes and round parachutes. This class of simulations involves complex geometries, flexible structural components, deforming fluid domains, and unsteady flow patterns. The key components of our simulation toolkit are a stabilized finite element flow solver, a nonlinear structural dynamics solver, an automatic mesh moving scheme, and an interface between the fluid and structural solvers; all of these have been developed within a parallel message-passing paradigm.

The 'upstream wake' of swimming and flying animals and its correlation with propulsive efficiency.

PubMed

Peng, Jifeng; Dabiri, John O

2008-08-01

The interaction between swimming and flying animals and their fluid environments generates downstream wake structures such as vortices. In most studies, the upstream flow in front of the animal is neglected. In this study, we demonstrate the existence of upstream fluid structures even though the upstream flow is quiescent or possesses a uniform incoming velocity. Using a computational model, the flow generated by a swimmer (an oscillating flexible plate) is simulated and a new fluid mechanical analysis is applied to the flow to identify the upstream fluid structures. These upstream structures show the exact portion of fluid that is going to interact with the swimmer. A mass flow rate is then defined based on the upstream structures, and a metric for propulsive efficiency is established using the mass flow rate and the kinematics of the swimmer. We propose that the unsteady mass flow rate defined by the upstream fluid structures can be used as a metric to measure and objectively compare the efficiency of locomotion in water and air.

Lectures series in computational fluid dynamics

NASA Technical Reports Server (NTRS)

Thompson, Kevin W.

1987-01-01

The lecture notes cover the basic principles of computational fluid dynamics (CFD). They are oriented more toward practical applications than theory, and are intended to serve as a unified source for basic material in the CFD field as well as an introduction to more specialized topics in artificial viscosity and boundary conditions. Each chapter in the test is associated with a videotaped lecture. The basic properties of conservation laws, wave equations, and shock waves are described. The duality of the conservation law and wave representations is investigated, and shock waves are examined in some detail. Finite difference techniques are introduced for the solution of wave equations and conservation laws. Stability analysis for finite difference approximations are presented. A consistent description of artificial viscosity methods are provided. Finally, the problem of nonreflecting boundary conditions are treated.

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.

Computational study of the melting-freezing transition in the quantum hard-sphere system for intermediate densities. II. Structural features.

PubMed

Sesé, Luis M; Bailey, Lorna E

2007-04-28

The structural features of the quantum hard-sphere system in the region of the fluid-face-centered-cubic-solid transition, for reduced number densities 0.45

A semi-implicit level set method for multiphase flows and fluid-structure interaction problems

NASA Astrophysics Data System (ADS)

Cottet, Georges-Henri; Maitre, Emmanuel

2016-06-01

In this paper we present a novel semi-implicit time-discretization of the level set method introduced in [8] for fluid-structure interaction problems. The idea stems from a linear stability analysis derived on a simplified one-dimensional problem. The semi-implicit scheme relies on a simple filter operating as a pre-processing on the level set function. It applies to multiphase flows driven by surface tension as well as to fluid-structure interaction problems. The semi-implicit scheme avoids the stability constraints that explicit scheme need to satisfy and reduces significantly the computational cost. It is validated through comparisons with the original explicit scheme and refinement studies on two-dimensional benchmarks.

Extended development of a sodium hydroxide thermal energy storage module

NASA Technical Reports Server (NTRS)

Rice, R. E.; Rowny, P. E.; Cohen, B. M.

1980-01-01

The post-test evaluation of a single heat exchanger sodium hydroxide thermal energy storage module for use in solar electric generation is reported. Chemical analyses of the storage medium used in the experimental model are presented. The experimental verification of the module performance using an alternate heat transfer fluid, Caloria HT-43, is described. Based on these results, a design analysis of a dual heat exchanger concept within the storage module is presented. A computer model and a reference design for the dual system (storage working fluid/power cycle working fluid) were completed. The dual system is estimated to have a capital cost of approximately one half that of the single heat exchanger concept.

Experimental quantification of the fluid dynamics in blood-processing devices through 4D-flow imaging: A pilot study on a real oxygenator/heat-exchanger module.

PubMed

Piatti, Filippo; Palumbo, Maria Chiara; Consolo, Filippo; Pluchinotta, Francesca; Greiser, Andreas; Sturla, Francesco; Votta, Emiliano; Siryk, Sergii V; Vismara, Riccardo; Fiore, Gianfranco Beniamino; Lombardi, Massimo; Redaelli, Alberto

2018-02-08

The performance of blood-processing devices largely depends on the associated fluid dynamics, which hence represents a key aspect in their design and optimization. To this aim, two approaches are currently adopted: computational fluid-dynamics, which yields highly resolved three-dimensional data but relies on simplifying assumptions, and in vitro experiments, which typically involve the direct video-acquisition of the flow field and provide 2D data only. We propose a novel method that exploits space- and time-resolved magnetic resonance imaging (4D-flow) to quantify the complex 3D flow field in blood-processing devices and to overcome these limitations. We tested our method on a real device that integrates an oxygenator and a heat exchanger. A dedicated mock loop was implemented, and novel 4D-flow sequences with sub-millimetric spatial resolution and region-dependent velocity encodings were defined. Automated in house software was developed to quantify the complex 3D flow field within the different regions of the device: region-dependent flow rates, pressure drops, paths of the working fluid and wall shear stresses were computed. Our analysis highlighted the effects of fine geometrical features of the device on the local fluid-dynamics, which would be unlikely observed by current in vitro approaches. Also, the effects of non-idealities on the flow field distribution were captured, thanks to the absence of the simplifying assumptions that typically characterize numerical models. To the best of our knowledge, our approach is the first of its kind and could be extended to the analysis of a broad range of clinically relevant devices. Copyright © 2017 Elsevier Ltd. All rights reserved.

Segment-specific resistivity improves body fluid volume estimates from bioimpedance spectroscopy in hemodialysis patients.

PubMed

Zhu, F; Kuhlmann, M K; Kaysen, G A; Sarkar, S; Kaitwatcharachai, C; Khilnani, R; Stevens, L; Leonard, E F; Wang, J; Heymsfield, S; Levin, N W

2006-02-01

Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold-standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck, and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Twenty-nine maintenance hemodialysis patients (16 men) underwent body composition analysis including whole body MRI, whole body potassium (40K) content, deuterium, and sodium bromide dilution, and segmental and wrist-to-ankle bioimpedance spectroscopy, all performed on the same day before a hemodialysis. Segment-specific resistivity was determined from segmental fat-free mass (FFM; by MRI), hydration status of FFM (by deuterium and sodium bromide), tissue resistance (by SBIS), and segment length. Segmental FFM was higher and extracellular hydration of FFM was lower in men compared with women. Segment-specific resistivity values for arm, trunk, and leg all differed from the uniform resistivity used in traditional SBIS algorithms. Estimates for whole body ECV, ICV, and total body water from SBIS using segmental instead of uniform resistivity values and after adjustment for unmeasured fluid volumes of the body did not differ significantly from gold-standard measures. The uniform tissue resistivity values used in traditional SBIS algorithms result in underestimation of ECV, ICV, and total body water. Use of segmental resistivity values combined with adjustment for body volumes that are neglected by traditional SBIS technique significantly improves estimations of body fluid volume in hemodialysis patients.

Bulk viscosity of water in acoustic modal analysis and experiment

NASA Astrophysics Data System (ADS)

Kůrečka, Jan; Habán, Vladimír; Himr, Daniel

2018-06-01

Bulk viscosity is an important factor in the damping properties of fluid systems and exhibits frequency dependent behaviour. A comparison between modal analysis in ANSYS Acoustics, custom code and experimental data is presented in this paper. The measured system consists of closed ended water-filled steel pipes of different lengths. The influence of a pipe wall, flanges on both ends and longitudinal waves in the structural part were included in measurement evaluation. Therefore, the obtained values of sound speed and bulk viscosity are parameters of the fluid. A numerical simulation was carried out only using fluid volume in a range of bulk viscosity. Damping characteristics in this range were compared to measured values. The results show a significant influence of sound speed and subsequently, the use of sound speed value regressed from experimental data yields a better fit between the measurement and the computation.

Journal and Wave Bearing Impedance Calculation Software

NASA Technical Reports Server (NTRS)

Hanford, Amanda; Campbell, Robert

2012-01-01

The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.

Computational Fluid Dynamic Analysis of Hydrodynamic forces on inundated bridge decks

NASA Astrophysics Data System (ADS)

Afzal, Bushra; Guo, Junke; Kerenyi, Kornel

2010-11-01

The hydraulic forces experienced by an inundated bridge deck have great importance in the design of bridges. Flood flows or hurricane add significant hydrodynamic loading on bridges, possibly resulting in failure of the bridge superstructures. The objective of the study is to establish validated computational practice to address research needs of the transportation community via computational fluid dynamic simulations. The reduced scale experiments conducted at Turner-Fairbank Highway Research Center establish the foundations of validated computational practices to address the research needs of the transportation community. Three bridge deck prototypes were used: a typical six-girder highway bridge deck, a three-girder deck, and a streamlined deck designed to better withstand the hydraulic forces. Results of the study showed that the streamlined deck significantly reduces drag, lift, and moment coefficient in comparison to the other bridge deck types. The CFD results matched the experimental data in terms of the relationship between inundation ratio and force measured at the bridge. The results of the present research will provide a tool for designing new bridges and retrofitting old ones.

Flow visualization of CFD using graphics workstations

NASA Technical Reports Server (NTRS)

Lasinski, Thomas; Buning, Pieter; Choi, Diana; Rogers, Stuart; Bancroft, Gordon

1987-01-01

High performance graphics workstations are used to visualize the fluid flow dynamics obtained from supercomputer solutions of computational fluid dynamic programs. The visualizations can be done independently on the workstation or while the workstation is connected to the supercomputer in a distributed computing mode. In the distributed mode, the supercomputer interactively performs the computationally intensive graphics rendering tasks while the workstation performs the viewing tasks. A major advantage of the workstations is that the viewers can interactively change their viewing position while watching the dynamics of the flow fields. An overview of the computer hardware and software required to create these displays is presented. For complex scenes the workstation cannot create the displays fast enough for good motion analysis. For these cases, the animation sequences are recorded on video tape or 16 mm film a frame at a time and played back at the desired speed. The additional software and hardware required to create these video tapes or 16 mm movies are also described. Photographs illustrating current visualization techniques are discussed. Examples of the use of the workstations for flow visualization through animation are available on video tape.

Management of pericardial fluid in blunt trauma: variability in practice and predictors of operative outcome in patients with computed tomography evidence of pericardial fluid

PubMed Central

Witt, Cordelie E.; Linnau, Ken F.; Maier, Ronald V.; Rivara, Frederick P.; Vavilala, Monica S.; Bulger, Eileen M.; Arbabi, Saman

2017-01-01

Background The objectives of this study were to assess current variability in management preferences for blunt trauma patients with pericardial fluid, and to identify characteristics associated with operative intervention for patients with pericardial fluid on admission computed tomography (CT) scan. Methods This was a mixed-methods study of blunt trauma patients with pericardial fluid. The first portion was a research survey of members of the Eastern Association for the Surgery of Trauma conducted in 2016, in which surgeons were presented with four clinical scenarios of blunt trauma patients with pericardial fluid. The second portion of the study was a retrospective evaluation of all blunt trauma patients ≥14 years treated at our Level I trauma center between 1/1/2010 and 11/1/2015 with pericardial fluid on admission CT scan. Results For the survey portion of our study, 393 surgeons responded (27% response rate). There was significant variability in management preferences for scenarios depicting trace pericardial fluid on CT with concerning hemodynamics, and for scenarios depicting hemopericardium intraoperatively. For the separate retrospective portion of our study, we identified 75 blunt trauma patients with pericardial fluid on admission CT scan. Seven underwent operative management; six of these had hypotension and/or electrocardiogram changes. In multivariable analysis, pericardial fluid amount was a significant predictor of receiving pericardial window (relative risk for one category increase in pericardial fluid amount: 3.99, 95% CI 1.47-10.81) but not of mortality. Conclusions There is significant variability in management preferences for patients with pericardial fluid from blunt trauma, indicating a need for evidence-based research. Our institutional data suggest that patients with minimal to small amounts of pericardial fluid without concerning clinical findings may be observed. Patients with moderate to large amounts of pericardial fluid who are clinically stable with normal hemodynamics may also appear appropriate for observation, although confirmation in larger studies is needed. Patients with hemodynamic instability should undergo operative exploration. Level of Evidence Level IV, Therapeutic/Care Management PMID:28129264

Computational fluid dynamics - The coming revolution

NASA Technical Reports Server (NTRS)

Graves, R. A., Jr.

1982-01-01

The development of aerodynamic theory is traced from the days of Aristotle to the present, with the next stage in computational fluid dynamics dependent on superspeed computers for flow calculations. Additional attention is given to the history of numerical methods inherent in writing computer codes applicable to viscous and inviscid analyses for complex configurations. The advent of the superconducting Josephson junction is noted to place configurational demands on computer design to avoid limitations imposed by the speed of light, and a Japanese projection of a computer capable of several hundred billion operations/sec is mentioned. The NASA Numerical Aerodynamic Simulator is described, showing capabilities of a billion operations/sec with a memory of 240 million words using existing technology. Near-term advances in fluid dynamics are discussed.

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.

CFD: computational fluid dynamics or confounding factor dissemination? The role of hemodynamics in intracranial aneurysm rupture risk assessment.

PubMed

Xiang, J; Tutino, V M; Snyder, K V; Meng, H

2014-10-01

Image-based computational fluid dynamics holds a prominent position in the evaluation of intracranial aneurysms, especially as a promising tool to stratify rupture risk. Current computational fluid dynamics findings correlating both high and low wall shear stress with intracranial aneurysm growth and rupture puzzle researchers and clinicians alike. These conflicting findings may stem from inconsistent parameter definitions, small datasets, and intrinsic complexities in intracranial aneurysm growth and rupture. In Part 1 of this 2-part review, we proposed a unifying hypothesis: both high and low wall shear stress drive intracranial aneurysm growth and rupture through mural cell-mediated and inflammatory cell-mediated destructive remodeling pathways, respectively. In the present report, Part 2, we delineate different wall shear stress parameter definitions and survey recent computational fluid dynamics studies, in light of this mechanistic heterogeneity. In the future, we expect that larger datasets, better analyses, and increased understanding of hemodynamic-biologic mechanisms will lead to more accurate predictive models for intracranial aneurysm risk assessment from computational fluid dynamics. © 2014 by American Journal of Neuroradiology.

Revisiting Newtonian and Non-Newtonian Fluid Mechanics Using Computer Algebra

ERIC Educational Resources Information Center

Knight, D. G.

2006-01-01

This article illustrates how a computer algebra system, such as Maple[R], can assist in the study of theoretical fluid mechanics, for both Newtonian and non-Newtonian fluids. The continuity equation, the stress equations of motion, the Navier-Stokes equations, and various constitutive equations are treated, using a full, but straightforward,…

Fluid Flow Investigations within a 37 Element CANDU Fuel Bundle Supported by Magnetic Resonance Velocimetry and Computational Fluid Dynamics

DOE PAGES

Piro, M.H.A; Wassermann, F.; Grundmann, S.; ...

2017-05-23

The current work presents experimental and computational investigations of fluid flow through a 37 element CANDU nuclear fuel bundle. Experiments based on Magnetic Resonance Velocimetry (MRV) permit three-dimensional, three-component fluid velocity measurements to be made within the bundle with sub-millimeter resolution that are non-intrusive, do not require tracer particles or optical access of the flow field. Computational fluid dynamic (CFD) simulations of the foregoing experiments were performed with the hydra-th code using implicit large eddy simulation, which were in good agreement with experimental measurements of the fluid velocity. Greater understanding has been gained in the evolution of geometry-induced inter-subchannel mixing,more » the local effects of obstructed debris on the local flow field, and various turbulent effects, such as recirculation, swirl and separation. These capabilities are not available with conventional experimental techniques or thermal-hydraulic codes. Finally, the overall goal of this work is to continue developing experimental and computational capabilities for further investigations that reliably support nuclear reactor performance and safety.« less

Fluid Flow Investigations within a 37 Element CANDU Fuel Bundle Supported by Magnetic Resonance Velocimetry and Computational Fluid Dynamics

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

Piro, M.H.A; Wassermann, F.; Grundmann, S.

The current work presents experimental and computational investigations of fluid flow through a 37 element CANDU nuclear fuel bundle. Experiments based on Magnetic Resonance Velocimetry (MRV) permit three-dimensional, three-component fluid velocity measurements to be made within the bundle with sub-millimeter resolution that are non-intrusive, do not require tracer particles or optical access of the flow field. Computational fluid dynamic (CFD) simulations of the foregoing experiments were performed with the hydra-th code using implicit large eddy simulation, which were in good agreement with experimental measurements of the fluid velocity. Greater understanding has been gained in the evolution of geometry-induced inter-subchannel mixing,more » the local effects of obstructed debris on the local flow field, and various turbulent effects, such as recirculation, swirl and separation. These capabilities are not available with conventional experimental techniques or thermal-hydraulic codes. Finally, the overall goal of this work is to continue developing experimental and computational capabilities for further investigations that reliably support nuclear reactor performance and safety.« less

A variational multiscale method for particle-cloud tracking in turbomachinery flows

NASA Astrophysics Data System (ADS)

Corsini, A.; Rispoli, F.; Sheard, A. G.; Takizawa, K.; Tezduyar, T. E.; Venturini, P.

2014-11-01

We present a computational method for simulation of particle-laden flows in turbomachinery. The method is based on a stabilized finite element fluid mechanics formulation and a finite element particle-cloud tracking method. We focus on induced-draft fans used in process industries to extract exhaust gases in the form of a two-phase fluid with a dispersed solid phase. The particle-laden flow causes material wear on the fan blades, degrading their aerodynamic performance, and therefore accurate simulation of the flow would be essential in reliable computational turbomachinery analysis and design. The turbulent-flow nature of the problem is dealt with a Reynolds-Averaged Navier-Stokes model and Streamline-Upwind/Petrov-Galerkin/Pressure-Stabilizing/Petrov-Galerkin stabilization, the particle-cloud trajectories are calculated based on the flow field and closure models for the turbulence-particle interaction, and one-way dependence is assumed between the flow field and particle dynamics. We propose a closure model utilizing the scale separation feature of the variational multiscale method, and compare that to the closure utilizing the eddy viscosity model. We present computations for axial- and centrifugal-fan configurations, and compare the computed data to those obtained from experiments, analytical approaches, and other computational methods.

Thermal stratification potential in rocket engine coolant channels

NASA Technical Reports Server (NTRS)

Kacynski, Kenneth J.

1992-01-01

The potential for rocket engine coolant channel flow stratification was computationally studied. A conjugate, 3-D, conduction/advection analysis code (SINDA/FLUINT) was used. Core fluid temperatures were predicted to vary by over 360 K across the coolant channel, at the throat section, indicating that the conventional assumption of a fully mixed fluid may be extremely inaccurate. Because of the thermal stratification of the fluid, the walls exposed to the rocket engine exhaust gases will be hotter than an assumption of full mixing would imply. In this analysis, wall temperatures were 160 K hotter in the turbulent mixing case than in the full mixing case. The discrepancy between the full mixing and turbulent mixing analyses increased with increasing heat transfer. Both analysis methods predicted identical channel resistances at the coolant inlet, but in the stratified analysis the thermal resistance was negligible. The implications are significant. Neglect of thermal stratification could lead to underpredictions in nozzle wall temperatures. Even worse, testing at subscale conditions may be inadequate for modeling conditions that would exist in a full scale engine.

Analysis of localized fringes in the holographic optical Schlieren system

NASA Technical Reports Server (NTRS)

Kurtz, R. L.

1980-01-01

The relation between localization of interference fringes in classical and holographic interferometry is reviewed and an application of holographic interferometry is considered for which the object is a transparent medium with nonhomogeneous refractive index. The technique is based on the analysis of the optical path length change of the object wave as it propagates through a transparent medium. Phase shifts due to variations of the speed of light within the medium give rise to an interference pattern. The resulting interferogram can be used to determine the physical properties of the medium or transparent object. Such properties include the mass density of fluids, electron densities of plasmas, the temperature of fluids, the chemical species concentration of fluids, and the state of stress in solids. The optical wave used can be either a simple plane or spherical wave, or it may be a complicated spatial wave scattered by a diffusing screen. The mathematical theory on the formation and analysis of localized fringes, the general theoretical concepts used, and a computer code for analysis are included along with the inversion of fringe order data.

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part I - theoretical analysis

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

Zacharia, T.; David, S.A.; Vitek, J.M.

1989-12-01

A computational and experimental study was carried out to quantitatively understand the influence of the heat flow and the fluid flow in the transient development of the weld pool during gas tungsten arc (GTA) and laser beam welding of Type 304 stainless steel. Stationary gas tungsten arc and laser beam welds were made on two heats of Type 304 austenitic stainless steels containing 90 ppm sulfur and 240 ppm sulfur. A transient heat transfer model was utilized to simulate the heat flow and fluid flow in the weld pool. In this paper, the results of the heat flow and fluidmore » flow analysis are presented.« less

Programmable calculator software for computation of the plasma binding of ligands.

PubMed

Conner, D P; Rocci, M L; Larijani, G E

1986-01-01

The computation of the extent of plasma binding of a ligand to plasma constituents using radiolabeled ligand and equilibrium dialysis is complex and tedious. A computer program for the HP-41C Handheld Computer Series (Hewlett-Packard) was developed to perform these calculations. The first segment of the program constructs a standard curve for quench correction of post-dialysis plasma and buffer samples, using either external standard ratio (ESR) or sample channels ratio (SCR) techniques. The remainder of the program uses the counts per minute, SCR or ESR, and post-dialysis volume of paired plasma and buffer samples generated from the dialysis procedure to compute the extent of binding after correction for background radiation, counting efficiency, and intradialytic shifts of fluid between plasma and buffer compartments during dialysis. This program greatly simplifies the analysis of equilibrium dialysis data and has been employed in the analysis of dexamethasone binding in normal and uremic sera.

2D Automatic body-fitted structured mesh generation using advancing extraction method

USDA-ARS?s Scientific Manuscript database

This paper presents an automatic mesh generation algorithm for body-fitted structured meshes in Computational Fluids Dynamics (CFD) analysis using the Advancing Extraction Method (AEM). The method is applicable to two-dimensional domains with complex geometries, which have the hierarchical tree-like...

2D automatic body-fitted structured mesh generation using advancing extraction method

USDA-ARS?s Scientific Manuscript database

This paper presents an automatic mesh generation algorithm for body-fitted structured meshes in Computational Fluids Dynamics (CFD) analysis using the Advancing Extraction Method (AEM). The method is applicable to two-dimensional domains with complex geometries, which have the hierarchical tree-like...

Insect Flight: Computation and Biomimetic Design

DTIC Science & Technology

2008-05-31

Mechanics, 37, 183-210 (2005). • Z. Jane Wang, ”Insect Flight”, McGraw Hill Year Book of Science and Technology, 2006. • Anders Andersen, Umberto Pesavento ...Umberto Pesavento , and Z. Jane Wang, ’Analysis of transitions between fluttering, tumbling and steady descent of falling cards’, Journal of Fluid

Advances in Quantum Trajectory Approaches to Dynamics

NASA Astrophysics Data System (ADS)

Askar, Attila

2001-03-01

The quantum fluid dynamics (QFD) formulation is based on the separation of the amplitude and phase of the complex wave function in Schrodinger's equation. The approach leads to conservation laws for an equivalent "gas continuum". The Lagrangian [1] representation corresponds to following the particles of the fluid continuum, i. e. calculating "quantum trajectories". The Eulerian [2] representation on the other hand, amounts to observing the dynamics of the gas continuum at the points of a fixed coordinate frame. The combination of several factors leads to a most encouraging computational efficiency. QFD enables the numerical analysis to deal with near monotonic amplitude and phase functions. The Lagrangian description concentrates the computation effort to regions of highest probability as an optimal adaptive grid. The Eulerian representation allows the study of multi-coordinate problems as a set of one-dimensional problems within an alternating direction methodology. An explicit time integrator limits the increase in computational effort with the number of discrete points to linear. Discretization of the space via local finite elements [1,2] and global radial functions [3] will be discussed. Applications include wave packets in four-dimensional quadratic potentials and two coordinate photo-dissociation problems for NOCl and NO2. [1] "Quantum fluid dynamics (QFD) in the Lagrangian representation with applications to photo-dissociation problems", F. Sales, A. Askar and H. A. Rabitz, J. Chem. Phys. 11, 2423 (1999) [2] "Multidimensional wave-packet dynamics within the fluid dynamical formulation of the Schrodinger equation", B. Dey, A. Askar and H. A. Rabitz, J. Chem. Phys. 109, 8770 (1998) [3] "Solution of the quantum fluid dynamics equations with radial basis function interpolation", Xu-Guang Hu, Tak-San Ho, H. A. Rabitz and A. Askar, Phys. Rev. E. 61, 5967 (2000)

Implementing a Loosely Coupled Fluid Structure Interaction Finite Element Model in PHASTA

NASA Astrophysics Data System (ADS)

Pope, David

Fluid Structure Interaction problems are an important multi-physics phenomenon in the design of aerospace vehicles and other engineering applications. A variety of computational fluid dynamics solvers capable of resolving the fluid dynamics exist. PHASTA is one such computational fluid dynamics solver. Enhancing the capability of PHASTA to resolve Fluid-Structure Interaction first requires implementing a structural dynamics solver. The implementation also requires a correction of the mesh used to solve the fluid equations to account for the deformation of the structure. This results in mesh motion and causes the need for an Arbitrary Lagrangian-Eulerian modification to the fluid dynamics equations currently implemented in PHASTA. With the implementation of both structural dynamics physics, mesh correction, and the Arbitrary Lagrangian-Eulerian modification of the fluid dynamics equations, PHASTA is made capable of solving Fluid-Structure Interaction problems.

CFD simulation of flow through heart: a perspective review.

PubMed

Khalafvand, S S; Ng, E Y K; Zhong, L

2011-01-01

The heart is an organ which pumps blood around the body by contraction of muscular wall. There is a coupled system in the heart containing the motion of wall and the motion of blood fluid; both motions must be computed simultaneously, which make biological computational fluid dynamics (CFD) difficult. The wall of the heart is not rigid and hence proper boundary conditions are essential for CFD modelling. Fluid-wall interaction is very important for real CFD modelling. There are many assumptions for CFD simulation of the heart that make it far from a real model. A realistic fluid-structure interaction modelling the structure by the finite element method and the fluid flow by CFD use more realistic coupling algorithms. This type of method is very powerful to solve the complex properties of the cardiac structure and the sensitive interaction of fluid and structure. The final goal of heart modelling is to simulate the total heart function by integrating cardiac anatomy, electrical activation, mechanics, metabolism and fluid mechanics together, as in the computational framework.

Wavelets, non-linearity and turbulence in fusion plasmas

NASA Astrophysics Data System (ADS)

van Milligen, B. Ph.

Introduction Linear spectral analysis tools Wavelet analysis Wavelet spectra and coherence Joint wavelet phase-frequency spectra Non-linear spectral analysis tools Wavelet bispectra and bicoherence Interpretation of the bicoherence Analysis of computer-generated data Coupled van der Pol oscillators A large eddy simulation model for two-fluid plasma turbulence A long wavelength plasma drift wave model Analysis of plasma edge turbulence from Langmuir probe data Radial coherence observed on the TJ-IU torsatron Bicoherence profile at the L/H transition on CCT Conclusions

Analysis of the autonomous problem about coupled active non-Newtonian multi-seepage in sparse medium

NASA Astrophysics Data System (ADS)

Deng, Shuxian; Li, Hongen

2017-10-01

The flow field of non-Newtonian fluid in sparse medium was analyzed by computational fluid dynamics (CFD) method. The results show that the axial velocity and radial velocity of the non-Newtonian fluid are larger than those of the Newtonian fluid due to the coupling of the viscosity of the non-Newtonian fluid and the shear rate, and the tangential velocity is less than that of the Newtonian fluid. These differences lead to the difference in the sparse medium Non-Newtonian fluids are of a special nature. The influence of the weight function on the global existence and blasting of the problem is discussed by analyzing the non-Newtonian percolation equation with nonlocal and weighted non-local Dirichlet boundary conditions. According to the non-Newtonian percolation equation, we define the weak solution of the problem and expound the local existence of the weak solution. Then we construct the test function and prove the weak comparison principle by using the Grown well inequality. The overall existence and blasting are analyzed by constructing the upper and lower solutions.

Comparison of Response Surface and Kriging Models in the Multidisciplinary Design of an Aerospike Nozzle

NASA Technical Reports Server (NTRS)

Simpson, Timothy W.

1998-01-01

The use of response surface models and kriging models are compared for approximating non-random, deterministic computer analyses. After discussing the traditional response surface approach for constructing polynomial models for approximation, kriging is presented as an alternative statistical-based approximation method for the design and analysis of computer experiments. Both approximation methods are applied to the multidisciplinary design and analysis of an aerospike nozzle which consists of a computational fluid dynamics model and a finite element analysis model. Error analysis of the response surface and kriging models is performed along with a graphical comparison of the approximations. Four optimization problems are formulated and solved using both approximation models. While neither approximation technique consistently outperforms the other in this example, the kriging models using only a constant for the underlying global model and a Gaussian correlation function perform as well as the second order polynomial response surface models.

Research in Varying Burner Tilt Angle to Reduce Rear Pass Temperature in Coal Fired Boiler

NASA Astrophysics Data System (ADS)

Thrangaraju, Savithry K.; Munisamy, Kannan M.; Baskaran, Saravanan

2017-04-01

This research shows the investigation conducted on one of techniques that is used in Manjung 700 MW tangentially fired coal power plant. The investigation conducted in this research is finding out the right tilt angle for the burners in the boiler that causes an efficient temperature distribution and combustion gas flow pattern in the boiler especially at the rear pass section. The main outcome of the project is to determine the right tilt angle for the burner to create an efficient temperature distribution and combustion gas flow pattern that able to increase the efficiency of the boiler. The investigation is carried out by using Computational Fluid Dynamics method to obtain the results by varying the burner tilt angle. The boiler model is drawn by using designing software which is called Solid Works and Fluent from Computational Fluid Dynamics is used to conduct the analysis on the boiler model. The analysis is to imitate the real combustion process in the real Manjung 700 MW boiler. The expected results are to determine the right burner tilt angle with a computational fluid analysis by obtaining the temperature distribution and combustion gas flow pattern for each of the three angles set for the burner tilt angle in FLUENT software. Three burner tilt angles are selected which are burner tilt angle at (0°) as test case 1, burner tilt angle at (+10°) as test case 2 and burner tilt angle at (-10°) as test case 3. These entire three cases were run in CFD software and the results of temperature distribution and velocity vector were obtained to find out the changes on the three cases at the furnace and rear pass section of the boiler. The results are being compared in analysis part by plotting graphs to determine the right tilting angle that reduces the rear pass temperature.

User's manual for master: Modeling of aerodynamic surfaces by 3-dimensional explicit representation. [input to three dimensional computational fluid dynamics

NASA Technical Reports Server (NTRS)

Gibson, S. G.

1983-01-01

A system of computer programs was developed to model general three dimensional surfaces. Surfaces are modeled as sets of parametric bicubic patches. There are also capabilities to transform coordinates, to compute mesh/surface intersection normals, and to format input data for a transonic potential flow analysis. A graphical display of surface models and intersection normals is available. There are additional capabilities to regulate point spacing on input curves and to compute surface/surface intersection curves. Input and output data formats are described; detailed suggestions are given for user input. Instructions for execution are given, and examples are shown.

Nonlinear analysis of a shock-loaded membrane.

NASA Technical Reports Server (NTRS)

Madden, R.; Remington, P. J.

1973-01-01

Results from a computer method for analyzing the unsteady interaction of a fluid stream and a flat circular elastic membrane are presented. The loading on the membrane is assumed to be caused by the firing of a shock tube. The fluid pressures and velocities are determined from a scheme based on the numerical method of characteristics, and the membrane is analyzed using exact relations for membrane strain. The interactive solution is found to give peak stresses 40% lower than a solution which assumes a pressure invariant in space and time.

Flow and Heat Transfer Analysis of an Eyring-Powell Fluid in a Pipe

NASA Astrophysics Data System (ADS)

Ali, N.; Nazeer, F.; Nazeer, Mubbashar

2018-02-01

The steady non-isothermal flow of an Eyring-Powell fluid in a pipe is investigated using both perturbation and numerical methods. The results are presented for two viscosity models, namely the Reynolds model and the Vogel model. The shooting method is employed to compute the numerical solution. Criteria for validity of perturbation solution are developed. When these criteria are met, it is shown that the perturbation solution is in good agreement with the numerical solution. The influence of various emerging parameters on the velocity and temperature field is also shown.

A novel method for a fast diagnosis of septic arthritis using mid infrared and deported spectroscopy.

PubMed

Albert, Jean-David; Monbet, Valérie; Jolivet-Gougeon, Anne; Fatih, Nadia; Le Corvec, Maëna; Seck, Malik; Charpentier, Frédéric; Coiffier, Guillaume; Boussard-Pledel, Catherine; Bureau, Bruno; Guggenbuhl, Pascal; Loréal, Olivier

2016-05-01

To assess the ability of mid infrared deported spectroscopy to discriminate synovial fluids samples of septic arthritis patients from other causes of joint effusion. Synovial fluids obtained from patients with clinically suspected arthritis were collected, analysed and classified according to standard diagnostic procedures as septic or non-septic. A spectroscopic analysis on synovial fluid samples was then performed using a coiled optical fiber made with chalcogenide glass. After a factorial analysis of the normalized spectra and the computation of a Fisher test used to select the most relevant components, a logistic regression model was fitted, allowing to attribute a score between 0 - non-septic -, and 1 - septic. In a first phase, we analysed the synovial fluids from 122 different synovial fluids including 6 septic arthritis among arthritis of various origins. Septic synovial fluids were identified with a sensitivity of 95.8% and a specificity of 93.9% and an AUROC of 0.977. The analysis of an independent set of samples (n=42, including two septic arthritis) gave similar values. Our data strongly supports the interest of mid infrared deported spectroscopy, which could be used potentially at point of care, for a rapid and easy diagnosis of septic arthritis. Now, the precision of the diagnosis must be evaluated through a multicentric study on a larger panel of patients. Copyright © 2015 Société française de rhumatologie. Published by Elsevier SAS. All rights reserved.

Simulating coupled dynamics of a rigid-flexible multibody system and compressible fluid

NASA Astrophysics Data System (ADS)

Hu, Wei; Tian, Qiang; Hu, HaiYan

2018-04-01

As a subsequent work of previous studies of authors, a new parallel computation approach is proposed to simulate the coupled dynamics of a rigid-flexible multibody system and compressible fluid. In this approach, the smoothed particle hydrodynamics (SPH) method is used to model the compressible fluid, the natural coordinate formulation (NCF) and absolute nodal coordinate formulation (ANCF) are used to model the rigid and flexible bodies, respectively. In order to model the compressible fluid properly and efficiently via SPH method, three measures are taken as follows. The first is to use the Riemann solver to cope with the fluid compressibility, the second is to define virtual particles of SPH to model the dynamic interaction between the fluid and the multibody system, and the third is to impose the boundary conditions of periodical inflow and outflow to reduce the number of SPH particles involved in the computation process. Afterwards, a parallel computation strategy is proposed based on the graphics processing unit (GPU) to detect the neighboring SPH particles and to solve the dynamic equations of SPH particles in order to improve the computation efficiency. Meanwhile, the generalized-alpha algorithm is used to solve the dynamic equations of the multibody system. Finally, four case studies are given to validate the proposed parallel computation approach.

Computational fluid dynamics: An engineering tool?

NASA Astrophysics Data System (ADS)

Anderson, J. D., Jr.

1982-06-01

Computational fluid dynamics in general, and time dependent finite difference techniques in particular, are examined from the point of view of direct engineering applications. Examples are given of the supersonic blunt body problem and gasdynamic laser calculations, where such techniques are clearly engineering tools. In addition, Navier-Stokes calculations of chemical laser flows are discussed as an example of a near engineering tool. Finally, calculations of the flowfield in a reciprocating internal combustion engine are offered as a promising future engineering application of computational fluid dynamics.

A High Performance Computing Approach to the Simulation of Fluid Solid Interaction Problems with Rigid and Flexible Components (Open Access Publisher’s Version)

DTIC Science & Technology

2014-08-01

performance computing, smoothed particle hydrodynamics, rigid body dynamics, flexible body dynamics ARMAN PAZOUKI ∗, RADU SERBAN ∗, DAN NEGRUT ∗ A...HIGH PERFORMANCE COMPUTING APPROACH TO THE SIMULATION OF FLUID-SOLID INTERACTION PROBLEMS WITH RIGID AND FLEXIBLE COMPONENTS This work outlines a unified...are implemented to model rigid and flexible multibody dynamics. The two- way coupling of the fluid and solid phases is supported through use of

Computation of fluid and particle motion from a time-sequenced image pair: a global outlier identification approach.

PubMed

Ray, Nilanjan

2011-10-01

Fluid motion estimation from time-sequenced images is a significant image analysis task. Its application is widespread in experimental fluidics research and many related areas like biomedical engineering and atmospheric sciences. In this paper, we present a novel flow computation framework to estimate the flow velocity vectors from two consecutive image frames. In an energy minimization-based flow computation, we propose a novel data fidelity term, which: 1) can accommodate various measures, such as cross-correlation or sum of absolute or squared differences of pixel intensities between image patches; 2) has a global mechanism to control the adverse effect of outliers arising out of motion discontinuities, proximity of image borders; and 3) can go hand-in-hand with various spatial smoothness terms. Further, the proposed data term and related regularization schemes are both applicable to dense and sparse flow vector estimations. We validate these claims by numerical experiments on benchmark flow data sets. © 2011 IEEE

Comparison of Computational Results with a Low-g, Nitrogen Slosh and Boiling Experiment

NASA Technical Reports Server (NTRS)

Stewart, Mark E.; Moder, Jeffrey P.

2015-01-01

This paper compares a fluid/thermal simulation, in Fluent, with a low-g, nitrogen slosh and boiling experiment. In 2010, the French Space Agency, CNES, performed cryogenic nitrogen experiments in a low-g aircraft campaign. From one parabolic flight, a low-g interval was simulated that focuses on low-g motion of nitrogen liquid and vapor with significant condensation, evaporation, and boiling. The computational results are compared with high-speed video, pressure data, heat transfer, and temperature data from sensors on the axis of the cylindrically shaped tank. These experimental and computational results compare favorably. The initial temperature stratification is in good agreement, and the two-phase fluid motion is qualitatively captured. Temperature data is matched except that the temperature sensors are unable to capture fast temperature transients when the sensors move from wet to dry (liquid to vapor) operation. Pressure evolution is approximately captured, but condensation and evaporation rate modeling and prediction need further theoretical analysis.

Investigation on the forced response of a radial turbine under aerodynamic excitations

NASA Astrophysics Data System (ADS)

Ma, Chaochen; Huang, Zhi; Qi, Mingxu

2016-04-01

Rotor blades in a radial turbine with nozzle guide vanes typically experience harmonic aerodynamic excitations due to the rotor stator interaction. Dynamic stresses induced by the harmonic excitations can result in high cycle fatigue (HCF) of the blades. A reliable prediction method for forced response issue is essential to avoid the HCF problem. In this work, the forced response mechanisms were investigated based on a fluid structure interaction (FSI) method. Aerodynamic excitations were obtained by three-dimensional unsteady computational fluid dynamics (CFD) simulation with phase shifted periodic boundary conditions. The first two harmonic pressures were determined as the primary components of the excitation and applied to finite element (FE) model to conduct the computational structural dynamics (CSD) simulation. The computed results from the harmonic forced response analysis show good agreement with the predictions of Singh's advanced frequency evaluation (SAFE) diagram. Moreover, the mode superposition method used in FE simulation offers an efficient way to provide quantitative assessments of mode response levels and resonant strength.

On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle

NASA Astrophysics Data System (ADS)

Weingart, Robert

This thesis is about the validation of a computational fluid dynamics simulation of a ground vehicle by means of a low-budget coast-down test. The vehicle is built to the standards of the 2014 Formula SAE rules. It is equipped with large wings in the front and rear of the car; the vertical loads on the tires are measured by specifically calibrated shock potentiometers. The coast-down test was performed on a runway of a local airport and is used to determine vehicle specific coefficients such as drag, downforce, aerodynamic balance, and rolling resistance for different aerodynamic setups. The test results are then compared to the respective simulated results. The drag deviates about 5% from the simulated to the measured results. The downforce numbers show a deviation up to 18% respectively. Moreover, a sensitivity analysis of inlet velocities, ride heights, and pitch angles was performed with the help of the computational simulation.

Self-reconfigurable ship fluid-network modeling for simulation-based design

NASA Astrophysics Data System (ADS)

Moon, Kyungjin

Our world is filled with large-scale engineering systems, which provide various services and conveniences in our daily life. A distinctive trend in the development of today's large-scale engineering systems is the extensive and aggressive adoption of automation and autonomy that enable the significant improvement of systems' robustness, efficiency, and performance, with considerably reduced manning and maintenance costs, and the U.S. Navy's DD(X), the next-generation destroyer program, is considered as an extreme example of such a trend. This thesis pursues a modeling solution for performing simulation-based analysis in the conceptual or preliminary design stage of an intelligent, self-reconfigurable ship fluid system, which is one of the concepts of DD(X) engineering plant development. Through the investigations on the Navy's approach for designing a more survivable ship system, it is found that the current naval simulation-based analysis environment is limited by the capability gaps in damage modeling, dynamic model reconfiguration, and simulation speed of the domain specific models, especially fluid network models. As enablers of filling these gaps, two essential elements were identified in the formulation of the modeling method. The first one is the graph-based topological modeling method, which will be employed for rapid model reconstruction and damage modeling, and the second one is the recurrent neural network-based, component-level surrogate modeling method, which will be used to improve the affordability and efficiency of the modeling and simulation (M&S) computations. The integration of the two methods can deliver computationally efficient, flexible, and automation-friendly M&S which will create an environment for more rigorous damage analysis and exploration of design alternatives. As a demonstration for evaluating the developed method, a simulation model of a notional ship fluid system was created, and a damage analysis was performed. Next, the models representing different design configurations of the fluid system were created, and damage analyses were performed with them in order to find an optimal design configuration for system survivability. Finally, the benefits and drawbacks of the developed method were discussed based on the result of the demonstration.

Analysis of Mars Pathfinder Entry Data, Aerothermal Heating, and Heat Shield Material Response

NASA Technical Reports Server (NTRS)

Milos, Frank; Chen, Y. K.; Tran, H. K.; Rasky, Daniel J. (Technical Monitor)

1997-01-01

The Mars Pathfinder heatshield contained several thermocouples and resistance thermometers. A description of the experiment, the entry data, and analysis of the entry environment and material response is presented. In particular, the analysis addresses uncertainties of the data and the fluid dynamics and material response models. The calculations use the latest trajectory and atmosphere reconstructions for the Pathfinder entry. A modified version of the GIANTS code is used for CFD (computational fluid dynamics) analyses, and FIAT is used for material response. The material response and flowfield are coupled appropriately. Three different material response models are considered. The analysis of Pathfinder entry data for validation of aerothermal heating and material response models is complicated by model uncertainties and unanticipated data-acquisition and processing problems. We will discuss these issues as well as ramifications of the data and analysis for future Mars missions.

Advanced Usage of Vehicle Sketch Pad for CFD-Based Conceptual Design

NASA Technical Reports Server (NTRS)

Ordaz, Irian; Li, Wu

2013-01-01

Conceptual design is the most fluid phase of aircraft design. It is important to be able to perform large scale design space exploration of candidate concepts that can achieve the design intent to avoid more costly configuration changes in later stages of design. This also means that conceptual design is highly dependent on the disciplinary analysis tools to capture the underlying physics accurately. The required level of analysis fidelity can vary greatly depending on the application. Vehicle Sketch Pad (VSP) allows the designer to easily construct aircraft concepts and make changes as the design matures. More recent development efforts have enabled VSP to bridge the gap to high-fidelity analysis disciplines such as computational fluid dynamics and structural modeling for finite element analysis. This paper focuses on the current state-of-the-art geometry modeling for the automated process of analysis and design of low-boom supersonic concepts using VSP and several capability-enhancing design tools.

High Accuracy Liquid Propellant Slosh Predictions Using an Integrated CFD and Controls Analysis Interface

NASA Technical Reports Server (NTRS)

Marsell, Brandon; Griffin, David; Schallhorn, Dr. Paul; Roth, Jacob

2012-01-01

Coupling computational fluid dynamics (CFD) with a controls analysis tool elegantly allows for high accuracy predictions of the interaction between sloshing liquid propellants and th e control system of a launch vehicle. Instead of relying on mechanical analogs which are not valid during aU stages of flight, this method allows for a direct link between the vehicle dynamic environments calculated by the solver in the controls analysis tool to the fluid flow equations solved by the CFD code. This paper describes such a coupling methodology, presents the results of a series of test cases, and compares said results against equivalent results from extensively validated tools. The coupling methodology, described herein, has proven to be highly accurate in a variety of different cases.

Integrated CFD and Controls Analysis Interface for High Accuracy Liquid Propellant Slosh Predictions

NASA Technical Reports Server (NTRS)

Marsell, Brandon; Griffin, David; Schallhorn, Paul; Roth, Jacob

2012-01-01

Coupling computational fluid dynamics (CFD) with a controls analysis tool elegantly allows for high accuracy predictions of the interaction between sloshing liquid propellants and the control system of a launch vehicle. Instead of relying on mechanical analogs which are n0t va lid during all stages of flight, this method allows for a direct link between the vehicle dynamic environments calculated by the solver in the controls analysis tool to the fluid now equations solved by the CFD code. This paper describes such a coupling methodology, presents the results of a series of test cases, and compares said results against equivalent results from extensively validated tools. The coupling methodology, described herein, has proven to be highly accurate in a variety of different cases.

Analysis of cryogenic propellant behavior in microgravity and low thrust environments

NASA Technical Reports Server (NTRS)

Fisher, Mark F.; Schmidt, George R.; Martin, James J.

1991-01-01

Predictions of a CFD program calculating a fluid-free surface shape and motion as a function of imposed acceleration are validated against the drop-tower test data collected to support design and performance assessments of the Saturn S-IVB stage liquid-hydrogen tank. The drop-tower facility, experimental package, and experiment procedures are outlined, and the program is described. It is noted that the validation analysis confirms the program's suitability for predicting low-g fluid slosh behavior, and that a similar analysis could examine the effect of incorporating baffles and screens to impede initiation of any unwanted side loads due to slosh. It is concluded that in actual vehicle applications, the engine thrust tailoff profile should be included in computer simulations if the precise interface versus time definition is needed.

Historical evolution of vortex-lattice methods

NASA Technical Reports Server (NTRS)

Deyoung, J.

1976-01-01

A review of the beginning and some orientation of the vortex-lattice method were given. The historical course of this method was followed in conjunction with its field of computational fluid dynamics, spanning the period from L.F. Richardson's paper in 1910 to 1975. The following landmarks were pointed out: numerical analysis of partial differential equations, lifting-line theory, finite-difference method, 1/4-3/4 rule, block relaxation technique, application of electronic computers, and advanced panel methods.

Computational Fluid Dynamics Demonstration of Rigid Bodies in Motion

NASA Technical Reports Server (NTRS)

Camarena, Ernesto; Vu, Bruce T.

2011-01-01

The Design Analysis Branch (NE-Ml) at the Kennedy Space Center has not had the ability to accurately couple Rigid Body Dynamics (RBD) and Computational Fluid Dynamics (CFD). OVERFLOW-D is a flow solver that has been developed by NASA to have the capability to analyze and simulate dynamic motions with up to six Degrees of Freedom (6-DOF). Two simulations were prepared over the course of the internship to demonstrate 6DOF motion of rigid bodies under aerodynamic loading. The geometries in the simulations were based on a conceptual Space Launch System (SLS). The first simulation that was prepared and computed was the motion of a Solid Rocket Booster (SRB) as it separates from its core stage. To reduce computational time during the development of the simulation, only half of the physical domain with respect to the symmetry plane was simulated. Then a full solution was prepared and computed. The second simulation was a model of the SLS as it departs from a launch pad under a 20 knot crosswind. This simulation was reduced to Two Dimensions (2D) to reduce both preparation and computation time. By allowing 2-DOF for translations and 1-DOF for rotation, the simulation predicted unrealistic rotation. The simulation was then constrained to only allow translations.

Multiphysics Computational Analysis of a Solid-Core Nuclear Thermal Engine Thrust Chamber

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Canabal, Francisco; Cheng, Gary; Chen, Yen-Sen

2007-01-01

The objective of this effort is to develop an efficient and accurate computational heat transfer methodology to predict thermal, fluid, and hydrogen environments for a hypothetical solid-core, nuclear thermal engine - the Small Engine. In addition, the effects of power profile and hydrogen conversion on heat transfer efficiency and thrust performance were also investigated. The computational methodology is based on an unstructured-grid, pressure-based, all speeds, chemically reacting, computational fluid dynamics platform, while formulations of conjugate heat transfer were implemented to describe the heat transfer from solid to hydrogen inside the solid-core reactor. The computational domain covers the entire thrust chamber so that the afore-mentioned heat transfer effects impact the thrust performance directly. The result shows that the computed core-exit gas temperature, specific impulse, and core pressure drop agree well with those of design data for the Small Engine. Finite-rate chemistry is very important in predicting the proper energy balance as naturally occurring hydrogen decomposition is endothermic. Locally strong hydrogen conversion associated with centralized power profile gives poor heat transfer efficiency and lower thrust performance. On the other hand, uniform hydrogen conversion associated with a more uniform radial power profile achieves higher heat transfer efficiency, and higher thrust performance.

Computational Fluid Dynamics Based 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. The work presented under this task uses the first-principles based Computational Fluid Dynamics (CFD) technique to compute heat transfer from 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 tank wall and cryogenic propellant, and that between tank wall and ullage gas were then simulated. The results showed that 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.

Airborne Shaped Sonic Boom Demonstration Pressure Measurements with Computational Fluid Dynamics Comparisons

NASA Technical Reports Server (NTRS)

Haering, Edward A., Jr.; Murray, James E.; Purifoy, Dana D.; Graham, David H.; Meredith, Keith B.; Ashburn, Christopher E.; Stucky, Mark

2005-01-01

The Shaped Sonic Boom Demonstration project showed for the first time that by careful design of aircraft contour the resultant sonic boom can maintain a tailored shape, propagating through a real atmosphere down to ground level. In order to assess the propagation characteristics of the shaped sonic boom and to validate computational fluid dynamics codes, airborne measurements were taken of the pressure signatures in the near field by probing with an instrumented F-15B aircraft, and in the far field by overflying an instrumented L-23 sailplane. This paper describes each aircraft and their instrumentation systems, the airdata calibration, analysis of the near- and far-field airborne data, and shows the good to excellent agreement between computational fluid dynamics solutions and flight data. The flights of the Shaped Sonic Boom Demonstration aircraft occurred in two phases. Instrumentation problems were encountered during the first phase, and corrections and improvements were made to the instrumentation system for the second phase, which are documented in the paper. Piloting technique and observations are also given. These airborne measurements of the Shaped Sonic Boom Demonstration aircraft are a unique and important database that will be used to validate design tools for a new generation of quiet supersonic aircraft.

Theory and simulation of time-fractional fluid diffusion in porous media

NASA Astrophysics Data System (ADS)

Carcione, José M.; Sanchez-Sesma, Francisco J.; Luzón, Francisco; Perez Gavilán, Juan J.

2013-08-01

We simulate a fluid flow in inhomogeneous anisotropic porous media using a time-fractional diffusion equation and the staggered Fourier pseudospectral method to compute the spatial derivatives. A fractional derivative of the order of 0 < ν < 2 replaces the first-order time derivative in the classical diffusion equation. It implies a time-dependent permeability tensor having a power-law time dependence, which describes memory effects and accounts for anomalous diffusion. We provide a complete analysis of the physics based on plane waves. The concepts of phase, group and energy velocities are analyzed to describe the location of the diffusion front, and the attenuation and quality factors are obtained to quantify the amplitude decay. We also obtain the frequency-domain Green function. The time derivative is computed with the Grünwald-Letnikov summation, which is a finite-difference generalization of the standard finite-difference operator to derivatives of fractional order. The results match the analytical solution obtained from the Green function. An example of the pressure field generated by a fluid injection in a heterogeneous sandstone illustrates the performance of the algorithm for different values of ν. The calculation requires storing the whole pressure field in the computer memory since anomalous diffusion ‘recalls the past’.

Shock Location Dominated Transonic Flight Loads on the Active Aeroelastic Wing

NASA Technical Reports Server (NTRS)

Lokos, William A.; Lizotte, Andrew; Lindsley, Ned J.; Stauf, Rick

2005-01-01

During several Active Aeroelastic Wing research flights, the shadow of the over-wing shock could be observed because of natural lighting conditions. As the plane accelerated, the shock location moved aft, and as the shadow passed the aileron and trailing-edge flap hinge lines, their associated hinge moments were substantially affected. The observation of the dominant effect of shock location on aft control surface hinge moments led to this investigation. This report investigates the effect of over-wing shock location on wing loads through flight-measured data and analytical predictions. Wing-root and wing-fold bending moment and torque and leading- and trailing-edge hinge moments have been measured in flight using calibrated strain gages. These same loads have been predicted using a computational fluid dynamics code called the Euler Navier-Stokes Three Dimensional Aeroelastic Code. The computational fluid dynamics study was based on the elastically deformed shape estimated by a twist model, which in turn was derived from in-flight-measured wing deflections provided by a flight deflection measurement system. During level transonic flight, the shock location dominated the wing trailing-edge control surface hinge moments. The computational fluid dynamics analysis based on the shape provided by the flight deflection measurement system produced very similar results and substantially correlated with the measured loads data.

A comparative study of serial and parallel aeroelastic computations of wings

NASA Technical Reports Server (NTRS)

Byun, Chansup; Guruswamy, Guru P.

1994-01-01

A procedure for computing the aeroelasticity of wings on parallel multiple-instruction, multiple-data (MIMD) computers is presented. In this procedure, fluids are modeled using Euler equations, and structures are modeled using modal or finite element equations. The procedure is designed in such a way that each discipline can be developed and maintained independently by using a domain decomposition approach. In the present parallel procedure, each computational domain is scalable. A parallel integration scheme is used to compute aeroelastic responses by solving fluid and structural equations concurrently. The computational efficiency issues of parallel integration of both fluid and structural equations are investigated in detail. This approach, which reduces the total computational time by a factor of almost 2, is demonstrated for a typical aeroelastic wing by using various numbers of processors on the Intel iPSC/860.

Device and method for measuring multi-phase fluid flow in a conduit using an elbow flow meter

DOEpatents

Ortiz, Marcos G.; Boucher, Timothy J.

1997-01-01

A system for measuring fluid flow in a conduit. The system utilizes pressure transducers disposed generally in line upstream and downstream of the flow of fluid in a bend in the conduit. Data from the pressure transducers is transmitted to a microprocessor or computer. The pressure differential measured by the pressure transducers is then used to calculate the fluid flow rate in the conduit. Control signals may then be generated by the microprocessor or computer to control flow, total fluid dispersed, (in, for example, an irrigation system), area of dispersal or other desired effect based on the fluid flow in the conduit.

Deterministic Local Sensitivity Analysis of Augmented Systems - II: Applications to the QUENCH-04 Experiment Using the RELAP5/MOD3.2 Code System

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

Ionescu-Bujor, Mihaela; Jin Xuezhou; Cacuci, Dan G.

2005-09-15

The adjoint sensitivity analysis procedure for augmented systems for application to the RELAP5/MOD3.2 code system is illustrated. Specifically, the adjoint sensitivity model corresponding to the heat structure models in RELAP5/MOD3.2 is derived and subsequently augmented to the two-fluid adjoint sensitivity model (ASM-REL/TF). The end product, called ASM-REL/TFH, comprises the complete adjoint sensitivity model for the coupled fluid dynamics/heat structure packages of the large-scale simulation code RELAP5/MOD3.2. The ASM-REL/TFH model is validated by computing sensitivities to the initial conditions for various time-dependent temperatures in the test bundle of the Quench-04 reactor safety experiment. This experiment simulates the reflooding with water ofmore » uncovered, degraded fuel rods, clad with material (Zircaloy-4) that has the same composition and size as that used in typical pressurized water reactors. The most important response for the Quench-04 experiment is the time evolution of the cladding temperature of heated fuel rods. The ASM-REL/TFH model is subsequently used to perform an illustrative sensitivity analysis of this and other time-dependent temperatures within the bundle. The results computed by using the augmented adjoint sensitivity system, ASM-REL/TFH, highlight the reliability, efficiency, and usefulness of the adjoint sensitivity analysis procedure for computing time-dependent sensitivities.« less

Computational Aerodynamic Analysis of Offshore Upwind and Downwind Turbines

DOE PAGES

Zhao, Qiuying; Sheng, Chunhua; Afjeh, Abdollah

2014-01-01

Aerodynamic interactions of the model NREL 5 MW offshore horizontal axis wind turbines (HAWT) are investigated using a high-fidelity computational fluid dynamics (CFD) analysis. Four wind turbine configurations are considered; three-bladed upwind and downwind and two-bladed upwind and downwind configurations, which operate at two different rotor speeds of 12.1 and 16 RPM. In the present study, both steady and unsteady aerodynamic loads, such as the rotor torque, blade hub bending moment, and base the tower bending moment of the tower, are evaluated in detail to provide overall assessment of different wind turbine configurations. Aerodynamic interactions between the rotor and tower are analyzed,more » including the rotor wake development downstream. The computational analysis provides insight into aerodynamic performance of the upwind and downwind, two- and three-bladed horizontal axis wind turbines.« less

Multidimensional bioseparation with modular microfluidics

DOEpatents

Chirica, Gabriela S.; Renzi, Ronald F.

2013-08-27

A multidimensional chemical separation and analysis system is described including a prototyping platform and modular microfluidic components capable of rapid and convenient assembly, alteration and disassembly of numerous candidate separation systems. Partial or total computer control of the separation system is possible. Single or multiple alternative processing trains can be tested, optimized and/or run in parallel. Examples related to the separation and analysis of human bodily fluids are given.

Methods for High-Order Multi-Scale and Stochastic Problems Analysis, Algorithms, and Applications

DTIC Science & Technology

2016-10-17

finite volume schemes, discontinuous Galerkin finite element method, and related methods, for solving computational fluid dynamics (CFD) problems and...approximation for finite element methods. (3) The development of methods of simulation and analysis for the study of large scale stochastic systems of...laws, finite element method, Bernstein-Bezier finite elements , weakly interacting particle systems, accelerated Monte Carlo, stochastic networks 16

First- and Second-Order Sensitivity Analysis of a P-Version Finite Element Equation Via Automatic Differentiation

NASA Technical Reports Server (NTRS)

Hou, Gene

1998-01-01

Sensitivity analysis is a technique for determining derivatives of system responses with respect to design parameters. Among many methods available for sensitivity analysis, automatic differentiation has been proven through many applications in fluid dynamics and structural mechanics to be an accurate and easy method for obtaining derivatives. Nevertheless, the method can be computational expensive and can require a high memory space. This project will apply an automatic differentiation tool, ADIFOR, to a p-version finite element code to obtain first- and second- order then-nal derivatives, respectively. The focus of the study is on the implementation process and the performance of the ADIFOR-enhanced codes for sensitivity analysis in terms of memory requirement, computational efficiency, and accuracy.

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.

A numerical solution of the Navier-Stokes equations for supercritical fluid thermodynamic analysis

NASA Technical Reports Server (NTRS)

Heinmiller, P. J.

1971-01-01

An explicit numerical solution of the compressible Navier-Stokes equations is applied to the thermodynamic analysis of supercritical oxygen in the Apollo cryogenic storage system. The wave character is retained in the conservation equations which are written in the basic fluid variables for a two-dimensional Cartesian coordinate system. Control-volume cells are employed to simplify imposition of boundary conditions and to ensure strict observance of local and global conservation principles. Non-linear real-gas thermodynamic properties responsible for the pressure collapse phenomonon in supercritical fluids are represented by tabular and empirical functions relating pressure and temperature to density and internal energy. Wall boundary conditions are adjusted at one cell face to emit a prescribed mass flowrate. Scaling principles are invoked to achieve acceptable computer execution times for very low Mach number convection problems. Detailed simulations of thermal stratification and fluid mixing occurring under low acceleration in the Apollo 12 supercritical oxygen tank are presented which model the pressure decay associated with de-stratification induced by an ordinary vehicle maneuver and heater cycle operation.

Characterization and Analyses of Valves, Feed Lines and Tanks used in Propellant Delivery Systems at NASA SSC

NASA Technical Reports Server (NTRS)

Ryan, Harry M.; Coote, David J.; Ahuja, Vineet; Hosangadi, Ashvin

2006-01-01

Accurate modeling of liquid rocket engine test processes involves assessing critical fluid mechanic and heat and mass transfer mechanisms within a cryogenic environment, and accurately modeling fluid properties such as vapor pressure and liquid and gas densities as a function of pressure and temperature. The Engineering and Science Directorate at the NASA John C. Stennis Space Center has developed and implemented such analytic models and analysis processes that have been used over a broad range of thermodynamic systems and resulted in substantial improvements in rocket propulsion testing services. In this paper, we offer an overview of the analyses techniques used to simulate pressurization and propellant fluid systems associated with the test stands at the NASA John C. Stennis Space Center. More specifically, examples of the global performance (one-dimensional) of a propellant system are provided as predicted using the Rocket Propulsion Test Analysis (RPTA) model. Computational fluid dynamic (CFD) analyses utilizing multi-element, unstructured, moving grid capability of complex cryogenic feed ducts, transient valve operation, and pressurization and mixing in propellant tanks are provided as well.

Effect of homogenous-heterogeneous reactions on MHD Prandtl fluid flow over a stretching sheet

NASA Astrophysics Data System (ADS)

Khan, Imad; Malik, M. Y.; Hussain, Arif; Salahuddin, T.

An analysis is performed to explore the effects of homogenous-heterogeneous reactions on two-dimensional flow of Prandtl fluid over a stretching sheet. In present analysis, we used the developed model of homogeneous-heterogeneous reactions in boundary layer flow. The mathematical configuration of presented flow phenomenon yields the nonlinear partial differential equations. Using scaling transformations, the governing partial differential equations (momentum equation and homogenous-heterogeneous reactions equations) are transformed into non-linear ordinary differential equations (ODE's). Then, resulting non-linear ODE's are solved by computational scheme known as shooting method. The quantitative and qualitative manners of concerned physical quantities (velocity, concentration and drag force coefficient) are examined under prescribed physical constrained through figures and tables. It is observed that velocity profile enhances verses fluid parameters α and β while Hartmann number reduced it. The homogeneous and heterogeneous reactions parameters have reverse effects on concentration profile. Concentration profile shows retarding behavior for large values of Schmidt number. Skin fraction coefficient enhances with increment in Hartmann number H and fluid parameter α .

Device and method for measuring multi-phase fluid flow and density of fluid in a conduit having a gradual bend

DOEpatents

Ortiz, Marcos German; Boucher, Timothy J.

1998-01-01

A system for measuring fluid flow in a conduit having a gradual bend or arc, and a straight section. The system includes pressure transducers, one or more disposed in the conduit on the outside of the arc, and one disposed in the conduit in a straight section thereof. The pressure transducers measure the pressure of fluid in the conduit at the locations of the pressure transducers and this information is used by a computational device to calculate fluid flow rate in the conduit. For multi-phase fluid, the density of the fluid is measured by another pair of pressure transducers, one of which is located in the conduit elevationally above the other. The computation device then uses the density measurement along with the fluid pressure measurements, to calculate fluid flow.

A collision scheme for hybrid fluid-particle simulation of plasmas

NASA Astrophysics Data System (ADS)

Nguyen, Christine; Lim, Chul-Hyun; Verboncoeur, John

2006-10-01

Desorption phenomena at the wall of a tokamak can lead to the introduction of impurities at the edge of a thermonuclear plasma. In particular, the use of carbon as a constituent of the tokamak wall, as planned for ITER, requires the study of carbon and hydrocarbon transport in the plasma, including understanding of collisional interaction with the plasma. These collisions can result in new hydrocarbons, hydrogen, secondary electrons and so on. Computational modeling is a primary tool for studying these phenomena. XOOPIC [1] and OOPD1 are widely used computer modeling tools for the simulation of plasmas. Both are particle type codes. Particle simulation gives more kinetic information than fluid simulation, but more computation time is required. In order to reduce this disadvantage, hybrid simulation has been developed, and applied to the modeling of collisions. Present particle simulation tools such as XOOPIC and OODP1 employ a Monte Carlo model for the collisions between particle species and a neutral background gas defined by its temperature and pressure. In fluid-particle hybrid plasma models, collisions include combinations of particle and fluid interactions categorized by projectile-target pairing: particle-particle, particle-fluid, and fluid-fluid. For verification of this hybrid collision scheme, we compare simulation results to analytic solutions for classical plasma models. [1] Verboncoeur et al. Comput. Phys. Comm. 87, 199 (1995).

3D Reconstruction of Chick Embryo Vascular Geometries Using Non-invasive High-Frequency Ultrasound for Computational Fluid Dynamics Studies.

PubMed

Tan, Germaine Xin Yi; Jamil, Muhammad; Tee, Nicole Gui Zhen; Zhong, Liang; Yap, Choon Hwai

2015-11-01

Recent animal studies have provided evidence that prenatal blood flow fluid mechanics may play a role in the pathogenesis of congenital cardiovascular malformations. To further these researches, it is important to have an imaging technique for small animal embryos with sufficient resolution to support computational fluid dynamics studies, and that is also non-invasive and non-destructive to allow for subject-specific, longitudinal studies. In the current study, we developed such a technique, based on ultrasound biomicroscopy scans on chick embryos. Our technique included a motion cancelation algorithm to negate embryonic body motion, a temporal averaging algorithm to differentiate blood spaces from tissue spaces, and 3D reconstruction of blood volumes in the embryo. The accuracy of the reconstructed models was validated with direct stereoscopic measurements. A computational fluid dynamics simulation was performed to model fluid flow in the generated construct of a Hamburger-Hamilton (HH) stage 27 embryo. Simulation results showed that there were divergent streamlines and a low shear region at the carotid duct, which may be linked to the carotid duct's eventual regression and disappearance by HH stage 34. We show that our technique has sufficient resolution to produce accurate geometries for computational fluid dynamics simulations to quantify embryonic cardiovascular fluid mechanics.

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.

Computational fluid dynamics uses in fluid dynamics/aerodynamics education

NASA Technical Reports Server (NTRS)

Holst, Terry L.

1994-01-01

The field of computational fluid dynamics (CFD) has advanced to the point where it can now be used for the purpose of fluid dynamics physics education. Because of the tremendous wealth of information available from numerical simulation, certain fundamental concepts can be efficiently communicated using an interactive graphical interrogation of the appropriate numerical simulation data base. In other situations, a large amount of aerodynamic information can be communicated to the student by interactive use of simple CFD tools on a workstation or even in a personal computer environment. The emphasis in this presentation is to discuss ideas for how this process might be implemented. Specific examples, taken from previous publications, will be used to highlight the presentation.

STS-1 environmental control and life support system. Consumables and thermal analysis

NASA Technical Reports Server (NTRS)

Steines, G.

1980-01-01

The Environmental Control and Life Support Systems (ECLSS)/thermal systems analysis for the Space Transportation System 1 Flight (STS-1) was performed using the shuttle environmental consumables usage requirements evaluation (SECURE) computer program. This program employs a nodal technique utilizing the Fortran Environmental Analysis Routines (FEAR). The output parameters evaluated were consumable quantities, fluid temperatures, heat transfer and rejection, and cabin atmospheric pressure. Analysis of these indicated that adequate margins exist for the nonpropulsive consumables and related thermal environment.

Conference on Fluid Machinery, 8th, Budapest, Hungary, Sept. 1987, Proceedings. Volumes 1 & 2

NASA Astrophysics Data System (ADS)

Szabo, A.; Kisbocskoi, L.

The present conference on turbomachine fluid mechanics gives attention to the analysis of labyrinth seals, irrigation turbomachinery, axial-flow fans, poppet valves, the generation of Karman vortices, self-rectifying Wells-type air turbines, computer simulations for water-supply systems, the computation of meridional flow in turbomachines, entrained air effects on vortex pump performance, the three-dimensional potential flow in a draft tube, and hydro powerplant diagnostic methods. Also discussed are a mathematical model for the initiation of cavitation wear, cryogenic flow in ejectors, flow downstream of guide vanes in a Kaplan turbine, unsteady flow in rotating cascades, novel methods for turbomachine vibration monitoring, cavitation breakdown in centrifugal pumps, test results for Banki turbines, centrifugal compressor return-channel flow, performance predictions for regenerative turbomachines, and secondary flows in a centrifugal pump.

Domain decomposition algorithms and computation fluid dynamics

NASA Technical Reports Server (NTRS)

Chan, Tony F.

1988-01-01

In the past several years, domain decomposition was a very popular topic, partly motivated by the potential of parallelization. While a large body of theory and algorithms were developed for model elliptic problems, they are only recently starting to be tested on realistic applications. The application of some of these methods to two model problems in computational fluid dynamics are investigated. Some examples are two dimensional convection-diffusion problems and the incompressible driven cavity flow problem. The construction and analysis of efficient preconditioners for the interface operator to be used in the iterative solution of the interface solution is described. For the convection-diffusion problems, the effect of the convection term and its discretization on the performance of some of the preconditioners is discussed. For the driven cavity problem, the effectiveness of a class of boundary probe preconditioners is 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.

Distributed-Memory Computing With the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA)

NASA Technical Reports Server (NTRS)

Riley, Christopher J.; Cheatwood, F. McNeil

1997-01-01

The Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA), a Navier-Stokes solver, has been modified for use in a parallel, distributed-memory environment using the Message-Passing Interface (MPI) standard. A standard domain decomposition strategy is used in which the computational domain is divided into subdomains with each subdomain assigned to a processor. Performance is examined on dedicated parallel machines and a network of desktop workstations. The effect of domain decomposition and frequency of boundary updates on performance and convergence is also examined for several realistic configurations and conditions typical of large-scale computational fluid dynamic analysis.

Computational Study of Intracranial Aneurysms with Flow Diverting Stent: Correlation with Surgical Outcome

NASA Astrophysics Data System (ADS)

Tang, Yik Sau; Chiu, Tin Lok; Tsang, Anderson Chun On; Leung, Gilberto Ka Kit; Chow, Kwok Wing

2016-11-01

Intracranial aneurysm, abnormal swelling of the cerebral artery, can cause massive internal bleeding in the subarachnoid space upon aneurysm rupture, leading to a high mortality rate. Deployment of a flow diverting stent through endovascular technique can obstruct the blood flow into the aneurysm, thus reducing the risk of rupture. Patient-specific models with both bifurcation and sidewall aneurysms have been investigated. Computational fluid dynamics analysis with physiological boundary conditions has been performed. Several hemodynamic parameters including volume flow rate into the aneurysm and the energy (sum of the fluid kinetic and potential energy) loss between the inlet and outlets were analyzed and compared with the surgical outcome. Based on the simulation results, we conjecture that a clinically successful case might imply less blood flow into the aneurysm after stenting, and thus a smaller amount of energy loss in driving the fluid flow in that portion of artery. This study might provide physicians with quantitative information for surgical decision making. (Partial financial support by the Innovation and Technology Support Program (ITS/011/13 & ITS/150/15) of the Hong Kong Special Administrative Region Government)

Fluid-structure analysis of a flexible flapping airfoil at low Reynolds number flow

NASA Astrophysics Data System (ADS)

Unger, Ralf; Haupt, Matthias C.; Horst, Peter; Radespiel, Rolf

2012-01-01

In this paper, a coupling simulation methodology is applied to investigate the fluid flow around a light and flexible airfoil based on a handfoil of a seagull. A finite element model of the flexible airfoil is fully coupled to the flow solver by using a load and displacement transfer as well as a fluid grid deformation algorithm. The flow field is characterized by a laminar-turbulent transition at a Reynolds number of Re=100 000, which takes place along a laminar separation bubble. An unsteady Reynolds-averaged Navier-Stokes flow solver is used to take this transition process into account by comparison of a critical N-factor with the N-factor computed by the eN-method. Results of computations have shown that the flexibility of the airfoil has a major influence on the thrust efficiency, the mean drag and lift, and the location of laminar-turbulent transition. The thrust efficiency can be considerably improved by increasing the plunging amplitude and by using a time dependent airfoil stiffness, inspired by the muscle contraction of birds.

Assess and improve the sustainability of water treatment facility using Computational Fluid Dynamics

NASA Astrophysics Data System (ADS)

Zhang, Jie; Tejada-Martinez, Andres; Lei, Hongxia; Zhang, Qiong

2016-11-01

Fluids problems in water treatment industry are often simplified or omitted since the focus is usually on chemical process only. However hydraulics also plays an important role in determining effluent water quality. Recent studies have demonstrated that computational fluid dynamics (CFD) has the ability to simulate the physical and chemical processes in reactive flows in water treatment facilities, such as in chlorine and ozone disinfection tanks. This study presents the results from CFD simulations of reactive flow in an existing full-scale ozone disinfection tank and in potential designs. Through analysis of the simulation results, we found that baffling factor and CT10 are not optimal indicators of disinfection performance. We also found that the relationship between effluent CT (the product of disinfectant concentration and contact time) obtained from CT transport simulation and baffling factor depends on the location of ozone release. In addition, we analyzed the environmental and economic impacts of ozone disinfection tank designs and developed a composite indicator to quantify the sustainability of ozone disinfection tank in technological, environmental and economic dimensions.

Computational Flow Analysis of a Left Ventricular Assist Device

NASA Technical Reports Server (NTRS)

Kiris, Cetin; Kwak, Dochan; Benkowski, Robert

1995-01-01

Computational fluid dynamics has been developed to a level where it has become an Indispensable part of aerospace research and design. Technology developed foe aerospace applications am also be utilized for the benefit of human health. For example, a flange-to-flange rocket engine fuel-pump simulation includes the rotating and non-rotating components: the flow straighteners, the impeller, and diffusers A Ventricular Assist Device developed by NASA Johnson Space Center and Baylor College of Medicine has a design similar to a rocket engine fuel pump in that it also consists of a flow straightener, an impeller, and a diffuser. Accurate and detailed knowledge of the flowfield obtained by incompressible flow calculations can be greatly beneficial to designers in their effort to reduce the cost and improve the reliability of these devices. In addition to the geometric complexities, a variety of flow phenomena are encountered in biofluids Then include turbulent boundary layer separation, wakes, transition, tip vortex resolution, three-dimensional effects, and Reynolds number effects. In order to increase the role of Computational Fluid Dynamics (CFD) in the design process the CFD analysis tools must be evaluated and validated so that designers gain Confidence in their use. The incompressible flow solver, INS3D, has been applied to flow inside of a liquid rocket engine turbopump components and extensively validated. This paper details how the computational flow simulation capability developed for liquid rocket engine pump component analysis has bean applied to the Left Ventricular Assist Device being developed jointly by NASA JSC and Baylor College of Medicine.

Shape optimization of pulsatile ventricular assist devices using FSI to minimize thrombotic risk

NASA Astrophysics Data System (ADS)

Long, C. C.; Marsden, A. L.; Bazilevs, Y.

2014-10-01

In this paper we perform shape optimization of a pediatric pulsatile ventricular assist device (PVAD). The device simulation is carried out using fluid-structure interaction (FSI) modeling techniques within a computational framework that combines FEM for fluid mechanics and isogeometric analysis for structural mechanics modeling. The PVAD FSI simulations are performed under realistic conditions (i.e., flow speeds, pressure levels, boundary conditions, etc.), and account for the interaction of air, blood, and a thin structural membrane separating the two fluid subdomains. The shape optimization study is designed to reduce thrombotic risk, a major clinical problem in PVADs. Thrombotic risk is quantified in terms of particle residence time in the device blood chamber. Methods to compute particle residence time in the context of moving spatial domains are presented in a companion paper published in the same issue (Comput Mech, doi: 10.1007/s00466-013-0931-y, 2013). The surrogate management framework, a derivative-free pattern search optimization method that relies on surrogates for increased efficiency, is employed in this work. For the optimization study shown here, particle residence time is used to define a suitable cost or objective function, while four adjustable design optimization parameters are used to define the device geometry. The FSI-based optimization framework is implemented in a parallel computing environment, and deployed with minimal user intervention. Using five SEARCH/ POLL steps the optimization scheme identifies a PVAD design with significantly better throughput efficiency than the original device.

Mean electromotive force generated by asymmetric fluid flow near the surface of earth's outer core

NASA Astrophysics Data System (ADS)

Bhattacharyya, Archana

1992-10-01

The phi component of the mean electromotive force, (ETF) generated by asymmetric flow of fluid just beneath the core-mantle boundary (CMB), is obtained using a geomagnetic field model. This analysis is based on the supposition that the axisymmetric part of fluid flow beneath the CMB is tangentially geostrophic and toroidal. For all the epochs studied, the computed phi component is stronger in the Southern Hemisphere than that in the Northern Hemisphere. Assuming a linear relationship between (ETF) and the azimuthally averaged magnetic field (AAMF), the only nonzero off-diagonal components of the pseudotensor relating ETF to AAMF, are estimated as functions of colatitude, and the physical implications of the results are discussed.

Teaching Computer-Aided Design of Fluid Flow and Heat Transfer Engineering Equipment.

ERIC Educational Resources Information Center

Gosman, A. D.; And Others

1979-01-01

Describes a teaching program for fluid mechanics and heat transfer which contains both computer aided learning (CAL) and computer aided design (CAD) components and argues that the understanding of the physical and numerical modeling taught in the CAL course is essential to the proper implementation of CAD. (Author/CMV)

Implications of the effective one-component analysis of pair correlations in colloidal fluids with polydispersity

NASA Astrophysics Data System (ADS)

Pond, Mark J.; Errington, Jeffrey R.; Truskett, Thomas M.

2011-09-01

Partial pair-correlation functions of colloidal suspensions with continuous polydispersity can be challenging to characterize from optical microscopy or computer simulation data due to inadequate sampling. As a result, it is common to adopt an effective one-component description of the structure that ignores the differences between particle types. Unfortunately, whether this kind of simplified description preserves or averages out information important for understanding the behavior of the fluid depends on the degree of polydispersity and can be difficult to assess, especially when the corresponding multicomponent description of the pair correlations is unavailable for comparison. Here, we present a computer simulation study that examines the implications of adopting an effective one-component structural description of a polydisperse fluid. The square-well model that we investigate mimics key aspects of the experimental behavior of suspended colloids with short-range, polymer-mediated attractions. To characterize the partial pair-correlation functions and thermodynamic excess entropy of this system, we introduce a Monte Carlo sampling strategy appropriate for fluids with a large number of pseudo-components. The data from our simulations at high particle concentrations, as well as exact theoretical results for dilute systems, show how qualitatively different trends between structural order and particle attractions emerge from the multicomponent and effective one-component treatments, even with systems characterized by moderate polydispersity. We examine consequences of these differences for excess-entropy based scalings of shear viscosity, and we discuss how use of the multicomponent treatment reveals similarities between the corresponding dynamic scaling behaviors of attractive colloids and liquid water that the effective one-component analysis does not capture.

Root Cause Analysis: An Examination of Odontogenic Origins of Acute Maxillary Sinusitis in Both Immunocompetent & Immunocompromised Patients.

PubMed

McCarty, Jennifer L; David, Ryan M; Lensing, Shelly Y; Samant, Rohan S; Kumar, Manoj; Van Hemert, Rudy L; Angtuaco, Edgardo J C; Fitzgerald, Ryan T

Dental and periodontal diseases represent important but often overlooked causes of acute sinusitis. Our goal was to examine the prevalence of potential odontogenic sources of acute maxillary sinusitis according to immune status and their associations with sinusitis. A retrospective review of maxillofacial computed tomography studies from 2013 to 2014 was performed. Each maxillary sinus and its ipsilateral dentition were evaluated for findings of acute sinusitis and dental/periodontal disease. Eighty-four patients (24 immunocompetent, 60 immunocompromised) had 171 maxillary sinuses that met inclusion criteria for acute maxillary sinusitis. Inspection of dentition revealed oroantral fistula in 1%, periapical lucencies in 16%, and projecting tooth root(s) in 71% of cases. Immunocompromised patients were more likely to have bilateral sinusitis than immunocompetent patients (67% vs 33%, P = 0.005). A paired case-control analysis in a subset of patients with unilateral maxillary sinusitis (n = 39) showed a higher prevalence of periapical lucency in association with sinuses that had an air fluid level-29% of sinuses with a fluid level had periapical lucency compared with 12% without sinus fluid (P = 0.033). Potential odontogenic sources of acute maxillary sinusitis are highly prevalent in both immunocompetent and immunocompromised patients, although the 2 patient populations demonstrate no difference in the prevalence of these potential odontogenic sources. Periapical lucencies were found to be associated with an ipsilateral sinus fluid level. Increased awareness of the importance of dental and periodontal diseases as key components of maxillofacial computed tomography interpretation would facilitate a more appropriate and timely treatment.

ADDRESSING ENVIRONMENTAL ENGINEERING CHALLENGES WITH COMPUTATIONAL FLUID DYNAMICS

EPA Science Inventory

This paper discusses the status and application of Computational Fluid Dynamics )CFD) models to address environmental engineering challenges for more detailed understanding of air pollutant source emissions, atmospheric dispersion and resulting human exposure. CFD simulations ...

Smart algorithms and adaptive methods in computational fluid dynamics

NASA Astrophysics Data System (ADS)

Tinsley Oden, J.

1989-05-01

A review is presented of the use of smart algorithms which employ adaptive methods in processing large amounts of data in computational fluid dynamics (CFD). Smart algorithms use a rationally based set of criteria for automatic decision making in an attempt to produce optimal simulations of complex fluid dynamics problems. The information needed to make these decisions is not known beforehand and evolves in structure and form during the numerical solution of flow problems. Once the code makes a decision based on the available data, the structure of the data may change, and criteria may be reapplied in order to direct the analysis toward an acceptable end. Intelligent decisions are made by processing vast amounts of data that evolve unpredictably during the calculation. The basic components of adaptive methods and their application to complex problems of fluid dynamics are reviewed. The basic components of adaptive methods are: (1) data structures, that is what approaches are available for modifying data structures of an approximation so as to reduce errors; (2) error estimation, that is what techniques exist for estimating error evolution in a CFD calculation; and (3) solvers, what algorithms are available which can function in changing meshes. Numerical examples which demonstrate the viability of these approaches are presented.

Nonlinear finite amplitude vibrations of sharp-edged beams in viscous fluids

NASA Astrophysics Data System (ADS)

Aureli, M.; Basaran, M. E.; Porfiri, M.

2012-03-01

In this paper, we study flexural vibrations of a cantilever beam with thin rectangular cross section submerged in a quiescent viscous fluid and undergoing oscillations whose amplitude is comparable with its width. The structure is modeled using Euler-Bernoulli beam theory and the distributed hydrodynamic loading is described by a single complex-valued hydrodynamic function which accounts for added mass and fluid damping experienced by the structure. We perform a parametric 2D computational fluid dynamics analysis of an oscillating rigid lamina, representative of a generic beam cross section, to understand the dependence of the hydrodynamic function on the governing flow parameters. We find that increasing the frequency and amplitude of the vibration elicits vortex shedding and convection phenomena which are, in turn, responsible for nonlinear hydrodynamic damping. We establish a manageable nonlinear correction to the classical hydrodynamic function developed for small amplitude vibration and we derive a computationally efficient reduced order modal model for the beam nonlinear oscillations. Numerical and theoretical results are validated by comparison with ad hoc designed experiments on tapered beams and multimodal vibrations and with data available in the literature. Findings from this work are expected to find applications in the design of slender structures of interest in marine applications, such as biomimetic propulsion systems and energy harvesting devices.

Computation of Nonlinear Hydrodynamic Loads on Floating Wind Turbines Using Fluid-Impulse Theory: Preprint

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

Kok Yan Chan, G.; Sclavounos, P. D.; Jonkman, J.

2015-04-02

A hydrodynamics computer module was developed for the evaluation of the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation for coupling with the FAST program. The recently developed formulation allows the computation of linear and nonlinear loads on floating bodies in the time domain and avoids the computationally intensive evaluation of temporal and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loadsmore » is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently. Computations are presented of the linear and nonlinear loads on the MIT/NREL tension-leg platform. Comparisons were carried out with frequency-domain linear and second-order methods. Emphasis was placed on modeling accuracy of the magnitude of nonlinear low- and high-frequency wave loads in a sea state. Although fluid-impulse theory is applied to floating wind turbines in this paper, the theory is applicable to other offshore platforms as well.« less

Neptune Aerocapture Systems Analysis

NASA Technical Reports Server (NTRS)

Lockwood, Mary Kae

2004-01-01

A Neptune Aerocapture Systems Analysis is completed to determine the feasibility, benefit and risk of an aeroshell aerocapture system for Neptune and to identify technology gaps and technology performance goals. The high fidelity systems analysis is completed by a five center NASA team and includes the following disciplines and analyses: science; mission design; aeroshell configuration screening and definition; interplanetary navigation analyses; atmosphere modeling; computational fluid dynamics for aerodynamic performance and database definition; initial stability analyses; guidance development; atmospheric flight simulation; computational fluid dynamics and radiation analyses for aeroheating environment definition; thermal protection system design, concepts and sizing; mass properties; structures; spacecraft design and packaging; and mass sensitivities. Results show that aerocapture can deliver 1.4 times more mass to Neptune orbit than an all-propulsive system for the same launch vehicle. In addition aerocapture results in a 3-4 year reduction in trip time compared to all-propulsive systems. Aerocapture is feasible and performance is adequate for the Neptune aerocapture mission. Monte Carlo simulation results show 100% successful capture for all cases including conservative assumptions on atmosphere and navigation. Enabling technologies for this mission include TPS manufacturing; and aerothermodynamic methods and validation for determining coupled 3-D convection, radiation and ablation aeroheating rates and loads, and the effects on surface recession.

Development of small scale cluster computer for numerical analysis

NASA Astrophysics Data System (ADS)

Zulkifli, N. H. N.; Sapit, A.; Mohammed, A. N.

2017-09-01

In this study, two units of personal computer were successfully networked together to form a small scale cluster. Each of the processor involved are multicore processor which has four cores in it, thus made this cluster to have eight processors. Here, the cluster incorporate Ubuntu 14.04 LINUX environment with MPI implementation (MPICH2). Two main tests were conducted in order to test the cluster, which is communication test and performance test. The communication test was done to make sure that the computers are able to pass the required information without any problem and were done by using simple MPI Hello Program where the program written in C language. Additional, performance test was also done to prove that this cluster calculation performance is much better than single CPU computer. In this performance test, four tests were done by running the same code by using single node, 2 processors, 4 processors, and 8 processors. The result shows that with additional processors, the time required to solve the problem decrease. Time required for the calculation shorten to half when we double the processors. To conclude, we successfully develop a small scale cluster computer using common hardware which capable of higher computing power when compare to single CPU processor, and this can be beneficial for research that require high computing power especially numerical analysis such as finite element analysis, computational fluid dynamics, and computational physics analysis.

Device and method for measuring multi-phase fluid flow in a conduit using an elbow flow meter

DOEpatents

Ortiz, M.G.; Boucher, T.J.

1997-06-24

A system is described for measuring fluid flow in a conduit. The system utilizes pressure transducers disposed generally in line upstream and downstream of the flow of fluid in a bend in the conduit. Data from the pressure transducers is transmitted to a microprocessor or computer. The pressure differential measured by the pressure transducers is then used to calculate the fluid flow rate in the conduit. Control signals may then be generated by the microprocessor or computer to control flow, total fluid dispersed, (in, for example, an irrigation system), area of dispersal or other desired effect based on the fluid flow in the conduit. 2 figs.

Computational fluid dynamics combustion analysis evaluation

NASA Technical Reports Server (NTRS)

Kim, Y. M.; Shang, H. M.; Chen, C. P.; Ziebarth, J. P.

1992-01-01

This study involves the development of numerical modelling in spray combustion. These modelling efforts are mainly motivated to improve the computational efficiency in the stochastic particle tracking method as well as to incorporate the physical submodels of turbulence, combustion, vaporization, and dense spray effects. The present mathematical formulation and numerical methodologies can be casted in any time-marching pressure correction methodologies (PCM) such as FDNS code and MAST code. A sequence of validation cases involving steady burning sprays and transient evaporating sprays will be included.

A finite difference method for a coupled model of wave propagation in poroelastic materials.

PubMed

Zhang, Yang; Song, Limin; Deffenbaugh, Max; Toksöz, M Nafi

2010-05-01

A computational method for time-domain multi-physics simulation of wave propagation in a poroelastic medium is presented. The medium is composed of an elastic matrix saturated with a Newtonian fluid, and the method operates on a digital representation of the medium where a distinct material phase and properties are specified at each volume cell. The dynamic response to an acoustic excitation is modeled mathematically with a coupled system of equations: elastic wave equation in the solid matrix and linearized Navier-Stokes equation in the fluid. Implementation of the solution is simplified by introducing a common numerical form for both solid and fluid cells and using a rotated-staggered-grid which allows stable solutions without explicitly handling the fluid-solid boundary conditions. A stability analysis is presented which can be used to select gridding and time step size as a function of material properties. The numerical results are shown to agree with the analytical solution for an idealized porous medium of periodically alternating solid and fluid layers.