Science.gov

Sample records for advanced fluid dynamics

  1. AFDM: An Advanced Fluid-Dynamics Model

    SciTech Connect

    Bohl, W.R.; Parker, F.R. ); Wilhelm, D. . Inst. fuer Neutronenphysik und Reaktortechnik); Berthier, J. ); Goutagny, L. . Inst. de Protection et de Surete Nucleaire); Ninokata,

    1990-09-01

    AFDM, or the Advanced Fluid-Dynamics Model, is a computer code that investigates new approaches simulating the multiphase-flow fluid-dynamics aspects of severe accidents in fast reactors. The AFDM formalism starts with differential equations similar to those in the SIMMER-II code. These equations are modified to treat three velocity fields and supplemented with a variety of new models. The AFDM code has 12 topologies describing what material contacts are possible depending on the presence or absence of a given material in a computational cell, on the dominant liquid, and on the continuous phase. Single-phase, bubbly, churn-turbulent, cellular, and dispersed flow regimes are permitted for the pool situations modeled. Virtual mass terms are included for vapor in liquid-continuous flow. Interfacial areas between the continuous and discontinuous phases are convected to allow some tracking of phenomenological histories. Interfacial areas are also modified by models of nucleation, dynamic forces, turbulence, flashing, coalescence, and mass transfer. Heat transfer is generally treated using engineering correlations. Liquid-vapor phase transitions are handled with the nonequilibrium, heat-transfer-limited model, whereas melting and freezing processes are based on equilibrium considerations. Convection is treated using a fractional-step method of time integration, including a semi-implicit pressure iteration. A higher-order differencing option is provided to control numerical diffusion. The Los Alamos SESAME equation-of-state has been implemented using densities and temperatures as the independent variables. AFDM programming has vectorized all computational loops consistent with the objective of producing an exportable code. 24 refs., 4 figs.

  2. The AFDM (advanced fluid dynamics model) program: Scope and significance

    SciTech Connect

    Bohl, W.R.; Parker, F.R. ); Wilhelm, D. . Inst. fuer Neutronenphysik und Reaktortechnik); Berthier, J. )

    1990-01-01

    The origins and goals of the advanced fluid dynamics model (AFDM) program are described, and the models, algorithm, and coding used in the resulting AFDM computer program are summarized. A sample fuel-steel boiling pool calculation is presented and compared with a similar SIMMER-II calculation. A subjective assessment of the AFDM developments is given, and areas where future work is possible are detailed. 10 refs.

  3. Microgravity fluid management requirements of advanced solar dynamic power systems

    NASA Technical Reports Server (NTRS)

    Migra, Robert P.

    1987-01-01

    The advanced solar dynamic system (ASDS) program is aimed at developing the technology for highly efficient, lightweight space power systems. The approach is to evaluate Stirling, Brayton and liquid metal Rankine power conversion systems (PCS) over the temperature range of 1025 to 1400K, identify the critical technologies and develop these technologies. Microgravity fluid management technology is required in several areas of this program, namely, thermal energy storage (TES), heat pipe applications and liquid metal, two phase flow Rankine systems. Utilization of the heat of fusion of phase change materials offers potential for smaller, lighter TES systems. The candidate TES materials exhibit large volume change with the phase change. The heat pipe is an energy dense heat transfer device. A high temperature application may transfer heat from the solar receiver to the PCS working fluid and/or TES. A low temperature application may transfer waste heat from the PCS to the radiator. The liquid metal Rankine PCS requires management of the boiling/condensing process typical of two phase flow systems.

  4. Computational structural mechanics and fluid dynamics: Advances and trends; Proceedings of the Symposium, Washington, DC, Oct. 17-19, 1988

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K. (Editor); Dwoyer, Douglas L. (Editor)

    1988-01-01

    Recent advances in computational structural and fluid dynamics are discussed in reviews and reports. Topics addressed include fluid-structure interaction and aeroelasticity, CFD techniques for reacting flows, micromechanics, stability and eigenproblems, probabilistic methods and chaotic dynamics, and perturbation and spectral methods. Consideration is given to finite-element, finite-volume, and boundary-element methods; adaptive methods; parallel processing machines and applications; and visualization, mesh generation, and AI interfaces.

  5. Proceedings of the International Symposium on Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances

    SciTech Connect

    Faybishenko, B.

    1999-02-01

    This publication contains extended abstracts of papers presented at the International Symposium ''Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances'' held at Ernest Orlando Lawrence Berkeley National Laboratory on February 10-12, 1999. This Symposium is organized in Honor of the 80th Birthday of Paul A. Witherspoon, who initiated some of the early investigations on flow and transport in fractured rocks at the University of California, Berkeley, and at Lawrence Berkeley National Laboratory. He is a key figure in the development of basic concepts, modeling, and field measurements of fluid flow and contaminant transport in fractured rock systems. The technical problems of assessing fluid flow, radionuclide transport, site characterization, modeling, and performance assessment in fractured rocks remain the most challenging aspects of subsurface flow and transport investigations. An understanding of these important aspects of hydrogeology is needed to assess disposal of nu clear wastes, development of geothermal resources, production of oil and gas resources, and remediation of contaminated sites. These Proceedings of more than 100 papers from 12 countries discuss recent scientific and practical developments and the status of our understanding of fluid flow and radionuclide transport in fractured rocks. The main topics of the papers are: Theoretical studies of fluid flow in fractured rocks; Multi-phase flow and reactive chemical transport in fractured rocks; Fracture/matrix interactions; Hydrogeological and transport testing; Fracture flow models; Vadose zone studies; Isotopic studies of flow in fractured systems; Fractures in geothermal systems; Remediation and colloid transport in fractured systems; and Nuclear waste disposal in fractured rocks.

  6. Computational fluid dynamics in the design and analysis of thermal processes: a review of recent advances.

    PubMed

    Norton, Tomás; Tiwari, Brijesh; Sun, Da Wen

    2013-01-01

    The design of thermal processes in the food industry has undergone great developments in the last two decades due to the availability of cheap computer power alongside advanced modelling techniques such as computational fluid dynamics (CFD). CFD uses numerical algorithms to solve the non-linear partial differential equations of fluid mechanics and heat transfer so that the complex mechanisms that govern many food-processing systems can be resolved. In thermal processing applications, CFD can be used to build three-dimensional models that are both spatially and temporally representative of a physical system to produce solutions with high levels of physical realism without the heavy costs associated with experimental analyses. Therefore, CFD is playing an ever growing role in the development of optimization of conventional as well as the development of new thermal processes in the food industry. This paper discusses the fundamental aspects involved in developing CFD solutions and forms a state-of-the-art review on various CFD applications in conventional as well as novel thermal processes. The challenges facing CFD modellers of thermal processes are also discussed. From this review it is evident that present-day CFD software, with its rich tapestries of mathematical physics, numerical methods and visualization techniques, is currently recognized as a formidable and pervasive technology which can permit comprehensive analyses of thermal processing.

  7. AFDM: An advanced fluid-dynamics model. Volume 6: EOS-AFDM interface

    SciTech Connect

    Henneges, G.; Kleinheins, S.

    1994-01-01

    This volume of the Advanced Fluid-Dynamics Model (AFDM) documents the modeling of the equation of state (EOS) in the code. The authors present an overview of the basic concepts underlying the thermodynamics modeling and resulting EOS, which is a set of relations between the thermodynamic properties of materials. The AFDM code allows for multiphase-multimaterial systems, which they explore in three phase models: two-material solid, two-material liquid, and three-material vapor. They describe and compare two ways of specifying the EOS of materials: (1) as simplified analytic expressions, or (2) as tables that precisely describe the properties of materials and their interactions for mechanical equilibrium. Either of the two EOS models implemented in AFDM can be selected by specifying the option when preprocessing the source code for compilation. Last, the authors determine thermophysical properties such as surface tension, thermal conductivities, and viscosities in the model for the intracell exchanges of AFDM. Specific notations, routines, EOS data, plots, test results, and corrections to the code are available in the appendices.

  8. The coupling of fluids, dynamics, and controls on advanced architecture computers

    NASA Technical Reports Server (NTRS)

    Atwood, Christopher

    1995-01-01

    This grant provided for the demonstration of coupled controls, body dynamics, and fluids computations in a workstation cluster environment; and an investigation of the impact of peer-peer communication on flow solver performance and robustness. The findings of these investigations were documented in the conference articles.The attached publication, 'Towards Distributed Fluids/Controls Simulations', documents the solution and scaling of the coupled Navier-Stokes, Euler rigid-body dynamics, and state feedback control equations for a two-dimensional canard-wing. The poor scaling shown was due to serialized grid connectivity computation and Ethernet bandwidth limits. The scaling of a peer-to-peer communication flow code on an IBM SP-2 was also shown. The scaling of the code on the switched fabric-linked nodes was good, with a 2.4 percent loss due to communication of intergrid boundary point information. The code performance on 30 worker nodes was 1.7 (mu)s/point/iteration, or a factor of three over a Cray C-90 head. The attached paper, 'Nonlinear Fluid Computations in a Distributed Environment', documents the effect of several computational rate enhancing methods on convergence. For the cases shown, the highest throughput was achieved using boundary updates at each step, with the manager process performing communication tasks only. Constrained domain decomposition of the implicit fluid equations did not degrade the convergence rate or final solution. The scaling of a coupled body/fluid dynamics problem on an Ethernet-linked cluster was also shown.

  9. Advanced feedback control of indoor air quality using real-time computational fluid dynamics

    SciTech Connect

    Ratnam, E.; Campbell, T.; Bradley, R.

    1998-10-01

    This paper describes the partial implementation of a novel method of controlling indoor air quality (IAQ) for critical applications. The proposed method uses a numerical modeling technique known as computational fluid dynamics (CFD) for modeling the effect of variable ventilation rates for intelligent and rapid control of air contamination in space. This paper describes how a CFD model is made to run in real time linked to a feedback control loop. The technique was simulated in a graphical programming language. The simulation results indicate that a quasi-transient potential flow CFD model is a viable technique for feedback control of IAQ, and it is currently being implemented in an experimental validation.

  10. Advances in Fluid Dynamics of Subsurface Flow of Groundwater, Hydrocarbons, and CO2

    NASA Astrophysics Data System (ADS)

    Weyer, K. U.

    2015-12-01

    In the past, the chemical methods of contaminant hydrogeology have dominated much of hydrogeological thinking. In their wake, understanding the physics of subsurface fluid flow and its application to practice and science seemingly has played a secondary role and it often has been replaced by numerical modelling only. Building an understanding of the actual physics of subsurface flow beyond numerical modelling, however, is a confusing experience exposing one to conflicting statements from the sides of engineers, hydrogeologists, and, for a decade or more, by the followers of free convection and density-driven flow. Within the physics of subsurface flow a number of questions arise, such as: Is water really incompressible as assumed in engineering hydraulics? How does buoyancy work? Are underground buoyancy forces generally directed vertically upwards or downwards? What is the consequential difference between hydrostatic and hydrodynamic conditions? What are the force fields causing subsurface flow for water, hydrocarbons and CO2? Is fluid flow really driven by pressure gradients as assumed in reservoir engineering? What is the effect of geothermal gradients on subsurface flow? Do convection cells and free convection exist on-shore? How does variable density flow work? Can today's numerical codes adequately determine variable density flow? Does saltwater really sink to the bottom of geologic systems due to its higher density? Aquitards create confining conditions and thereby confine fluid movements to aquifers? Does more water flow in aquifers than aquitards? The presentation will shed light on the maze of conflicting statements issued within engineering hydraulics and groundwater dynamics. It will also present a field case and its numerical modelling of variable density flow at a major industrial landfill site. The presentation will thereby foster the understanding of the correct physics involved and how this physics can be beneficially applied to practical cases

  11. An advanced combustion research facility for validating computational fluid dynamics codes

    NASA Astrophysics Data System (ADS)

    Bullard, J. B.; Hurley, C. D.; Eccles, N. C.

    1991-12-01

    The Sector Combustion Rig (SCR), built to obtain experimental data which could be used to verify computational fluid dynamic programs and to investigate the formation and consumption of combustion products through a combustor, is described. This rig was designed to accommodate sectors of full size engine combustion chambers and to test them at real or simulated engine operating conditions. Changes made to improve the operating, measurement, and data handling capabilities of the rig as a result of experience from several years of operations are described together with some of the features which contribute to the uniqueness of the SCR. The SCR gas analysis system and instrumentation are described. Extracts from some results obtained during a recent program of tests on a Rolls-Royce RB211 combustor are given.

  12. Fracturing Fluid Characterization Facility (FFCF): Recent advances

    SciTech Connect

    Shah, S.N.; Fagan, J.E.

    1995-07-01

    The objectives of this project are: (1)Investigate fluid rheological behavior, dynamic fluid leak-off behavior, and proppant transport characteristics of various fracturing fluids used for stimulating oil and gas bearing formations. (2) Develop new information for characterizing the behavior of fracturing fluids under conditions more representative of the behavior in actual fractures. (3) Continue utilizing the advanced capabilities of the high pressure simulator (HPS) to perform near-term research and development activities and not to construct a large-scale simulator that was proposed originally. This paper describes equipment enhancements, data acquisition and instrumentation upgrades, R&D test results, and future research planned for the Fracturing Fluid Characterization Facility.

  13. Computational Fluid Dynamic Analysis of the Posterior Airway Space After Maxillomandibular Advancement For Obstructive Sleep Apnea Syndrome

    PubMed Central

    Sittitavornwong, Somsak; Waite, Peter D.; Shih, Alan M.; Cheng, Gary C.; Koomullil, Roy; Ito, Yasushi; Cure, Joel K; Harding, Susan M.; Litaker, Mark

    2013-01-01

    Purpose Evaluate the soft tissue change of the upper airway after maxillomandibular advancement (MMA) by computational fluid dynamics (CFD). Materials and Methods Eight OSAS patients who required MMA were recruited into this study. All participants had pre- and post-operative computed tomography (CT) and underwent MMA by a single oral and maxillofacial surgeon. Upper airway CT data sets for these 8 participants were created with high-fidelity 3-D numerical models for computational fluid dynamics (CFD). The 3-D models were simulated and analyzed to study how changes in airway anatomy affects pressure effort required for normal breathing. Airway dimensions, skeletal changes, Apnea-Hypopnea Index (AHI), and pressure efforts of pre- and post-operative 3-D models were compared and correlations interpreted. Results After MMA, laminar and turbulent air flow was significantly decreased at every level of the airway. The cross-sectional areas at the soft palate and tongue base were significantly increased. Conclusions This study shows that MMA increases airway dimensions by the increasing the occipital base (Base) - pogonion (Pg) distance. An increase of the Base-Pg distance showed a significant correlation with an AHI improvement and a decreased pressure effort of the upper airway. Decreasing the pressure effort will decrease the breathing workload. This improves the condition of OSAS. PMID:23642544

  14. Computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    1989-01-01

    An overview of computational fluid dynamics (CFD) activities at the Langley Research Center is given. The role of supercomputers in CFD research, algorithm development, multigrid approaches to computational fluid flows, aerodynamics computer programs, computational grid generation, turbulence research, and studies of rarefied gas flows are among the topics that are briefly surveyed.

  15. Polymer Fluid Dynamics.

    ERIC Educational Resources Information Center

    Bird, R. Byron

    1980-01-01

    Problems in polymer fluid dynamics are described, including development of constitutive equations, rheometry, kinetic theory, flow visualization, heat transfer studies, flows with phase change, two-phase flow, polymer unit operations, and drag reduction. (JN)

  16. Results of the Workshop on Two-Phase Flow, Fluid Stability and Dynamics: Issues in Power, Propulsion, and Advanced Life Support Systems

    NASA Technical Reports Server (NTRS)

    McQuillen, John; Rame, Enrique; Kassemi, Mohammad; Singh, Bhim; Motil, Brian

    2003-01-01

    The Two-phase Flow, Fluid Stability and Dynamics Workshop was held on May 15, 2003 in Cleveland, Ohio to define a coherent scientific research plan and roadmap that addresses the multiphase fluid problems associated with NASA s technology development program. The workshop participants, from academia, industry and government, prioritized various multiphase issues and generated a research plan and roadmap to resolve them. This report presents a prioritization of the various multiphase flow and fluid stability phenomena related primarily to power, propulsion, fluid and thermal management and advanced life support; and a plan to address these issues in a logical and timely fashion using analysis, ground-based and space-flight experiments.

  17. Computational fluid dynamic control

    NASA Technical Reports Server (NTRS)

    Hartley, Tom T.; Deabreu-Garcia, Alex

    1989-01-01

    A general technique is presented for modeling fluid, or gas, dynamic systems specifically for the development of control systems. The numerical methods which are generally used in computational fluid dynamics are borrowed to create either continuous-time or discrete-time models of the particular fluid system. The resulting equations can be either left in a nonlinear form, or easily linearized about an operating point. As there are typically very many states in these systems, the usual linear model reduction methods can be used on them to allow a low-order controller to be designed. A simple example is given which typifies many internal flow control problems. The resulting control is termed computational fluid dynamic control.

  18. Computational fluid dynamic applications

    SciTech Connect

    Chang, S.-L.; Lottes, S. A.; Zhou, C. Q.

    2000-04-03

    The rapid advancement of computational capability including speed and memory size has prompted the wide use of computational fluid dynamics (CFD) codes to simulate complex flow systems. CFD simulations are used to study the operating problems encountered in system, to evaluate the impacts of operation/design parameters on the performance of a system, and to investigate novel design concepts. CFD codes are generally developed based on the conservation laws of mass, momentum, and energy that govern the characteristics of a flow. The governing equations are simplified and discretized for a selected computational grid system. Numerical methods are selected to simplify and calculate approximate flow properties. For turbulent, reacting, and multiphase flow systems the complex processes relating to these aspects of the flow, i.e., turbulent diffusion, combustion kinetics, interfacial drag and heat and mass transfer, etc., are described in mathematical models, based on a combination of fundamental physics and empirical data, that are incorporated into the code. CFD simulation has been applied to a large variety of practical and industrial scale flow systems.

  19. Relativistic fluid dynamics. Proceedings.

    NASA Astrophysics Data System (ADS)

    Anile, A. M.; Choquet-Bruhat, Y.

    Contents: 1. Covariant theory of conductivity in ideal fluid or solid media (B. Carter). 2. Hamiltonian techniques for relativistic fluid dynamics and stability theory (D. D. Holm). 3. Covariant fluid mechanics and thermodynamics: an introduction (W. Israel). 4. Relativistic plasmas (H. Weitzner). 5. An improved relativistic warm plasma model (A. M. Anile, S. Pennisi). 6. Relativistic extended thermodynamics II (I. Müller). 7. Relativistic extended thermodynamics: general assumptions and mathematical procedure (T. Ruggeri). 8. Relativistic hydrodynamics and heavy ion reactions (D. Strottman). 9. Some problems in relativistic hydrodynamics (C. G. van Weert).

  20. Astrophysical fluid dynamics

    NASA Astrophysics Data System (ADS)

    Ogilvie, Gordon I.

    2016-06-01

    > These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is `frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, including shocks and other discontinuities, are discussed. The spherical blast wave resulting from a supernova, and involving a strong shock, is a classic problem that can be solved analytically. Steady solutions with spherical or axial symmetry reveal the physics of winds and jets from stars and discs. The linearized equations determine the oscillation modes of astrophysical bodies, as well as their stability and their response to tidal forcing.

  1. 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.

  2. Fluid dynamics of heart development.

    PubMed

    Santhanakrishnan, Arvind; Miller, Laura A

    2011-09-01

    The morphology, muscle mechanics, fluid dynamics, conduction properties, and molecular biology of the developing embryonic heart have received much attention in recent years due to the importance of both fluid and elastic forces in shaping the heart as well as the striking relationship between the heart's evolution and development. Although few studies have directly addressed the connection between fluid dynamics and heart development, a number of studies suggest that fluids may play a key role in morphogenic signaling. For example, fluid shear stress may trigger biochemical cascades within the endothelial cells of the developing heart that regulate chamber and valve morphogenesis. Myocardial activity generates forces on the intracardiac blood, creating pressure gradients across the cardiac wall. These pressures may also serve as epigenetic signals. In this article, the fluid dynamics of the early stages of heart development is reviewed. The relevant work in cardiac morphology, muscle mechanics, regulatory networks, and electrophysiology is also reviewed in the context of intracardial fluid dynamics. PMID:21327946

  3. Advances in three-dimensional coronary imaging and computational fluid dynamics: is virtual fractional flow reserve more than just a pretty picture?

    PubMed

    Poon, Eric K W; Hayat, Umair; Thondapu, Vikas; Ooi, Andrew S H; Ul Haq, Muhammad Asrar; Moore, Stephen; Foin, Nicolas; Tu, Shengxian; Chin, Cheng; Monty, Jason P; Marusic, Ivan; Barlis, Peter

    2015-08-01

    Percutaneous coronary intervention (PCI) has shown a high success rate in the treatment of coronary artery disease. The decision to perform PCI often relies on the cardiologist's visual interpretation of coronary lesions during angiography. This has inherent limitations, particularly due to the low resolution and two-dimensional nature of angiography. State-of-the-art modalities such as three-dimensional quantitative coronary angiography, optical coherence tomography and invasive fractional flow reserve (FFR) may improve clinicians' understanding of both the anatomical and physiological importance of coronary lesions. While invasive FFR is the gold standard technique for assessment of the haemodynamic significance of coronary lesions, recent studies have explored a surrogate for FFR derived solely from three-dimensional reconstruction of the invasive angiogram, and therefore eliminating need for a pressure wire. Utilizing advanced computational fluid dynamics research, this virtual fractional flow reserve (vFFR) has demonstrated reasonable correlation with invasive measurements and remains an intense area of ongoing study. However, at present, several limitations and computational fluid dynamic assumptions may preclude vFFR from widespread clinical use. This review demonstrates the tight integration of advanced three-dimensional imaging techniques and vFFR in assessing coronary artery disease, reviews the advantages and disadvantages of such techniques and attempts to provide a glimpse of how such advances may benefit future clinical decision-making during PCI. PMID:26247271

  4. Stellar Astrophysical Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Thompson, Michael J.; Christensen-Dalsgaard, Jørgen

    2003-05-01

    Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. Stellar Rotation and Magnetic Fields: 6. Stellar rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and stellar magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for stellar dynamics Edward A

  5. Stellar Astrophysical Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Thompson, Michael J.; Christensen-Dalsgaard, Jørgen

    2008-02-01

    Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. Stellar Rotation and Magnetic Fields: 6. Stellar rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and stellar magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for stellar dynamics Edward A

  6. Computational Fluid Dynamics Library

    2005-03-04

    CFDLib05 is the Los Alamos Computational Fluid Dynamics LIBrary. This is a collection of hydrocodes using a common data structure and a common numerical method, for problems ranging from single-field, incompressible flow, to multi-species, multi-field, compressible flow. The data structure is multi-block, with a so-called structured grid in each block. The numerical method is a Finite-Volume scheme employing a state vector that is fully cell-centered. This means that the integral form of the conservation lawsmore » is solved on the physical domain that is represented by a mesh of control volumes. The typical control volume is an arbitrary quadrilateral in 2D and an arbitrary hexahedron in 3D. The Finite-Volume scheme is for time-unsteady flow and remains well coupled by means of time and space centered fluxes; if a steady state solution is required, the problem is integrated forward in time until the user is satisfied that the state is stationary.« less

  7. Body Fluid Dynamics: Back to the Future

    PubMed Central

    Bhave, Gautam; Neilson, Eric G.

    2014-01-01

    Pioneering investigations conducted over a half century ago on tonicity, transcapillary fluid exchange, and the distribution of water and solute serve as a foundation for understanding the physiology of body fluid spaces. With passage of time, however, some of these concepts have lost their connectivity to more contemporary information. Here we examine the physical forces determining the compartmentalization of body fluid and its movement across capillary and cell membrane barriers, drawing particular attention to the interstitium operating as a dynamic interface for water and solute distribution rather than as a static reservoir. Newer work now supports an evolving model of body fluid dynamics that integrates exchangeable Na+ stores and transcapillary dynamics with advances in interstitial matrix biology. PMID:22034644

  8. Body fluid dynamics: back to the future.

    PubMed

    Bhave, Gautam; Neilson, Eric G

    2011-12-01

    Pioneering investigations conducted over a half century ago on tonicity, transcapillary fluid exchange, and the distribution of water and solute serve as a foundation for understanding the physiology of body fluid spaces. With passage of time, however, some of these concepts have lost their connectivity to more contemporary information. Here we examine the physical forces determining the compartmentalization of body fluid and its movement across capillary and cell membrane barriers, drawing particular attention to the interstitium operating as a dynamic interface for water and solute distribution rather than as a static reservoir. Newer work now supports an evolving model of body fluid dynamics that integrates exchangeable Na(+) stores and transcapillary dynamics with advances in interstitial matrix biology. PMID:22034644

  9. Wanapum Dam Advanced Hydro Turbine Upgrade Project: Part 2 - Evaluation of Fish Passage Test Results Using Computational Fluid Dynamics

    SciTech Connect

    Dresser, Thomas J.; Dotson, Curtis L.; Fisher, Richard K.; Graf, Michael J.; Richmond, Marshall C.; Rakowski, Cynthia L.; Carlson, Thomas J.; Mathur, Dilip; Heisey, Paul G.

    2007-10-10

    This paper, the second part of a 2 part paper, discusses the use of Computational Fluid Dynamics (CFD) to gain further insight into the results of fish release testing conducted to evaluate the modifications made to upgrade Unit 8 at Wanapum Dam. Part 1 discusses the testing procedures and fish passage survival. Grant PUD is working with Voith Siemens Hydro (VSH) and the Pacific Northwest National Laboratory (PNNL) of DOE and Normandeau Associates in this evaluation. VSH has prepared the geometry for the CFD analysis corresponding to the four operating conditions tested with Unit 9, and the 5 operating conditions tested with Unit 8. Both VSH and PNNL have conducting CFD simulations of the turbine intakes, stay vanes, wicket gates, turbine blades and draft tube of the units. Primary objectives of the analyses were: • determine estimates of where the inserted fish passed the turbine components • determine the characteristics of the flow field along the paths calculated for pressure, velocity gradients and acceleration associated with fish sized bodies • determine the velocity gradients at the structures where fish to structure interaction is predicted. • correlate the estimated fish location of passage with observed injuries • correlate the calculated pressure and acceleration with the information recorded with the sensor fish • utilize the results of the analysis to further interpret the results of the testing. This paper discusses the results of the CFD analyses made to assist the interpretation of the fish test results.

  10. Fluid Dynamics with Free Surfaces

    1992-02-01

    RIPPLE is a two-dimensional, transient, free surface incompressible fluid dynamics program. It allows multiple free surfaces with surface tension and wall adhesion forces and has a partial cell treatment which allows curved boundaries and interior obstacles.

  11. The Variety of Fluid Dynamics.

    ERIC Educational Resources Information Center

    Barnes, Francis; And Others

    1980-01-01

    Discusses three research topics which are concerned with eminently practical problems and deal at the same time with fundamental fluid dynamical problems. These research topics come from the general areas of chemical and biological engineering, geophysics, and pure mathematics. (HM)

  12. Fluid Dynamics of Bottle Filling

    NASA Astrophysics Data System (ADS)

    McGough, Patrick; Gao, Haijing; Appathurai, Santosh; Basaran, Osman

    2011-11-01

    Filling of bottles is a widely practiced operation in a large number of industries. Well known examples include filling of ``large'' bottles with shampoos and cleaners in the household products and beauty care industries and filling of ``small'' bottles in the pharmaceutical industry. Some bottle filling operations have recently drawn much attention from the fluid mechanics community because of the occurrence of a multitude of complex flow regimes, transitions, and instabilities such as mounding and coiling that occur as a bottle is filled with a fluid. In this talk, we present a primarily computational study of the fluid dynamical challenges that can arise during the rapid filling of bottles. Given the diversity of fluids used in filling applications, we consider four representative classes of fluids that exhibit Newtonian, shear-thinning, viscoelastic, and yield-stress rheologies. The equations governing the dynamics of bottle filling are solved either in their full 3D but axisymmetric form or using the slender-jet approximation.

  13. The handbook of fluid dynamics

    SciTech Connect

    Johnson, R.W.

    1998-07-01

    This book provides professionals in the field of fluid dynamics with a comprehensive guide and resource. The book balances three traditional areas of fluid mechanics--theoretical, computational, and experimental--and expounds on basic science and engineering techniques. Each chapter introduces a topic, discusses the primary issues related to this subject, outlines approaches taken by experts, and supplies references for further information. Topics discussed include: (1) basic engineering fluid dynamics; (2) classical fluid dynamics; (3) turbulence modeling; (4) reacting flows; (5) multiphase flows; (6) flow and porous media; (7) high Reynolds number asymptotic theories; (8) finite difference method; (9) finite volume method; (10) finite element methods; (11) spectral element methods for incompressible flows; (12) experimental methods, such as hot-wire anemometry, laser-Doppler velocimetry, and flow visualization; and (13) applications, such as axial-flow compressor and fan aerodynamics, turbomachinery, airfoils and wings, atmospheric flows, and mesoscale oceanic flows.

  14. Fluid dynamics test method

    NASA Technical Reports Server (NTRS)

    Gayman, W. H.

    1974-01-01

    Test method and apparatus determine fluid effective mass and damping in frequency range where effective mass may be considered as total mass less sum of slosh masses. Apparatus is designed so test tank and its mounting yoke are supported from structural test wall by series of flexures.

  15. Geophysical Fluid Dynamics Outreach Films

    NASA Astrophysics Data System (ADS)

    Aurnou, J. M.; Schwarz, J. W.; Noguez, G.

    2012-12-01

    Here we will present high definition films of laboratory experiments demonstrating basic fluid motions similar to those occurring in atmospheres and oceans. In these experiments, we use water to simulate the fluid dynamics of both the liquid (oceans) and gaseous (atmospheric) envelopes. To simulate the spinning of the earth, we carry out the experiments on a rotating table. For each experiment, we begin by looking at our system first without the effects of rotation. Then, we include rotation to see how the behavior of the fluid changes due to the Coriolis accelerations. Our hope is that by viewing these experiments one will develop a sense for how fluids behave both in rotating and non-rotating systems. By noting the differences between the experiments, it should then be possible to establish a basis to think about large-scale fluid motions that exist in Earth's oceans and atmospheres as well as on planets other than Earth.Plan view image of vortices in a rotating tank of fluid. Movies of such flows make accessible the often difficult to comprehend fluid dynamical processes that occur in planetary atmospheres and oceans.

  16. Computational Fluid Dynamics Symposium on Aeropropulsion

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Recognizing the considerable advances that have been made in computational fluid dynamics, the Internal Fluid Mechanics Division of NASA Lewis Research Center sponsored this symposium with the objective of providing a forum for exchanging information regarding recent developments in numerical methods, physical and chemical modeling, and applications. This conference publication is a compilation of 4 invited and 34 contributed papers presented in six sessions: algorithms one and two, turbomachinery, turbulence, components application, and combustors. Topics include numerical methods, grid generation, chemically reacting flows, turbulence modeling, inlets, nozzles, and unsteady flows.

  17. Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE): Lunar Advanced Volatile Analysis (LAVA) Capillary Fluid Dynamic Restriction Effects on Gas Chromatography

    NASA Technical Reports Server (NTRS)

    Gonzalez, Marianne; Quinn, Jacqueline; Captain, Janine; Santiago-Bond, Josephine; Starr, Stanley

    2015-01-01

    The Resource Prospector (RP) mission with the Regolith and Environment Science and Oxygen Lunar Volatile Extraction (RESOLVE) payload aims to show the presence of water in lunar regolith, and establish a proving ground for NASAs mission to Mars. One of the analysis is performed by the Lunar Advanced Volatiles Analysis (LAVA) subsystem, which consists of a fluid network that facilitates the transport of volatile samples to a gas chromatograph and mass spectrometer (GC-MS) instrument. The understanding of fluid dynamics directed from the GC to the MS is important due to the influence of flow rates and pressures that affect the accuracy of and prevent the damage to the overall GC-MS instrument. The micro-scale capillary fluid network within the GC alone has various lengths and inner-diameters; therefore, determination of pressure differentials and flow rates are difficult to model computationally, with additional complexity from the vacuum conditions in space and lack of a lunar atmosphere. A series of tests were performed on an experimental set-up of the system where the inner diameters of the GC transfer line connecting to the MS were varied. The effect on chromatography readings were also studied by applying these lines onto a GC instrument. It was found that a smaller inner diameter transfer line resulted in a lower flow rate, as well as a lower pressure differential across the thermal conductivity detector (TCD) unit of the GC and a negligible pressure drop across the mock-up capillary column. The chromatography was affected with longer retention times and broader peak integrations. It was concluded that a 0.050 mm inner diameter line still proved most suitable for the systems flow rate preferences. In addition, it was evident that this small transfer line portrayed some expense to GC signal characteristics and the wait time for steady-state operation.

  18. Incompressible Viscous Fluid Dynamics

    1992-02-13

    NACHOS2 is a finite element program designed for the analysis of two-dimensional, incompressible viscous fluid flow problems. The basic flows considered may be isothermal, nonisothermal, or may involve other physical processes, such as mass transport. Both steady and transient flows may be analyzed. The class of problems treated are those described by the two-dimensional (plane or axisymmetric) incompressible form of the Navier-Stokes equations. An energy transport equation is included in the formulation for problems inmore » which heat transfer effects are important. Two auxiliary transport equations can be added to describe other physical processes,e.g. mass transfer, chemical reactions. Among the specific types of flow problems treated are: isothermal flow; forced, free, or mixed convection; conjugate heat transfer; flow in saturated porous media with or without heat transfer; and inelastic, non-Newtonian flows with or without heat transfer. Other problem classes are possible depending on the specific definitions applied to the auxiliary transport equations.« less

  19. Artificial Heart Fluid Dynamics.

    NASA Astrophysics Data System (ADS)

    Mussivand, Tofigh Varcaneh

    Flow characteristics within pneumatic, pulsatile, and pusher plate prosthetic hearts were studied. The blood pumps evaluated were duplicates of pumps used for in vivo calf and for clinical implantation at the Cleveland Clinic Foundation. Human dura mater bioprosthetic, caged disk, and Bjork-Shiley tilting disk valves were employed in the pumps. Dual camera video tape and synchronized still photography were used to study flow patterns. Diffused light and a planar laser source provided illumination. The laser light was fanned into a plane with a thickness of 0.2 mm to 10 mm. Magnesium oxide and Amberlite particles were used as tracers. Aqueous-glycerol, aqueous-sucrose solutions and mineral oil were used as blood analog fluids. Inflow, outflow, drive, and afterload pressures, diaphragm motion, cardiac output, and heart rate were measured and recorded. An electrical circuit was developed to synchronize pump diaphragm motion with captured images of flow trajectories. After digitizing the trajectories, velocities, global and local turbulence, and shear stresses were obtained. Disturbed and recirculating zones were identified. Qualitative and quantitative analyses were performed using data obtained from the digitization of flow trajectories. Simultaneous turbulence and stasis were observed during most phases of the cardiac cycles in all the pumps tested. A maximum Reynold's shear stress of 2889 dynes/cm ^2 occurred at 120 beats per minute (bpm). The peak velocity was 146 cm/sec during systole. The identified regions of recirculation, low velocity and disturbed flow were shown to correlate with thrombosed areas of explanted blood pumps. The maximum calculated turbulence intensity was 106 cm/sec which occurred at 120 bpm during systole.

  20. Computational Fluid Dynamics For Helicopters

    NASA Technical Reports Server (NTRS)

    Caradonna, F. X.; Mccroskey, W. J.

    1990-01-01

    Powerful computer codes undergoing development. Report reviews development of computational fluid dynamics (CFD) for prediction of airflow around rotary wings of helicopters. Reviews progress in following endeavors: Prediction and verification of flows under various operating conditions; calculation of interactions between rotor blades and vortexes; analysis of viscous, transonic flows about airfoils; and study of formation of vortexes at tips of rotors.

  1. Fluid dynamic bowtie attenuators

    NASA Astrophysics Data System (ADS)

    Szczykutowicz, Timothy P.; Hermus, James

    2015-03-01

    Fluence field modulated CT allows for improvements in image quality and dose reduction. To date, only 1-D modulators have been proposed, the extension to 2-D modulation is difficult with solid-metal attenuation-based modulators. This work proposes to use liquids and gas to attenuate the x-ray beam which can be arrayed allowing for 2-D fluence modulation. The thickness of liquid and the pressure for a given path length of gas were determined that provided the same attenuation as 30 cm of soft tissue at 80, 100, 120, and 140 kV. Gaseous Xenon and liquid Iodine, Zinc Chloride, and Cerium Chloride were studied. Additionally, we performed some proof-of-concept experiments in which (1) a single cell of liquid was connected to a reservoir which allowed the liquid thickness to be modulated and (2) a 96 cell array was constructed in which the liquid thickness in each cell was adjusted manually. Liquid thickness varied as a function of kV and chemical composition, with Zinc Chloride allowing for the smallest thickness; 1.8, 2.25, 3, and 3.6 cm compensated for 30 cm of soft tissue at 80, 100, 120, and 140 kV respectively. The 96 cell Iodine attenuator allowed for a reduction in both dynamic range to the detector and scatter to primary ratio. Successful modulation of a single cell was performed at 0, 90, and 130 degrees using a simple piston/actuator. The thickness of liquids and the Xenon gas pressure seem logistically implementable within the constraints of CBCT and diagnostic CT systems.

  2. Advanced working fluids: Thermodynamic properties

    NASA Astrophysics Data System (ADS)

    Lee, Lloyd L.; Gering, Kevin L.

    1990-10-01

    Electrolytes are used as working fluids in gas fired heat pump chiller engine cycles. To find out which molecular parameters of the electrolytes impact on cycle performance, a molecular theory is developed for calculating solution properties, enthalpies, vapor-liquid equilibria, and engine cycle performance. Aqueous and ammoniac single and mixed salt solutions in single and multisolvent systems are investigated. An accurate correlation is developed to evaluate properties for concentrated electrolyte solutions. Sensitivity analysis is used to determine the impact of molecular parameters on the thermodynamic properties and cycle performance. The preferred electrolytes are of 1-1 valence type, small ion size, high molecular weight, and in strongly colligative cosolvent. The operating windows are determined for a number of absorption fluids of industrial importance.

  3. Visualization of Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Gerald-Yamasaki, Michael; Hultquist, Jeff; Bryson, Steve; Kenwright, David; Lane, David; Walatka, Pamela; Clucas, Jean; Watson, Velvin; Lasinski, T. A. (Technical Monitor)

    1995-01-01

    Scientific visualization serves the dual purpose of exploration and exposition of the results of numerical simulations of fluid flow. Along with the basic visualization process which transforms source data into images, there are four additional components to a complete visualization system: Source Data Processing, User Interface and Control, Presentation, and Information Management. The requirements imposed by the desired mode of operation (i.e. real-time, interactive, or batch) and the source data have their effect on each of these visualization system components. The special requirements imposed by the wide variety and size of the source data provided by the numerical simulation of fluid flow presents an enormous challenge to the visualization system designer. We describe the visualization system components including specific visualization techniques and how the mode of operation and source data requirements effect the construction of computational fluid dynamics visualization systems.

  4. 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.

  5. Advanced solar dynamic technology program

    NASA Technical Reports Server (NTRS)

    Calogeras, James

    1990-01-01

    Viewgraphs and discussion on Advanced Solar Dynamic Technology Program are presented. Topics covered include: advanced solar dynamic technology program; advanced concentrators; advanced heat receivers; power conversion systems; dished all metal honeycomb sandwich panels; Stirling cavity heat pipe receiver; Brayton solar receiver; and thermal energy storage technology.

  6. Electro-Fluid Dynamic Jets

    NASA Astrophysics Data System (ADS)

    Campbell, Nicholas

    2014-11-01

    The success of dielectric barrier discharge (DBD) plasma actuators as flow control devices in transducing electrical energy directly into near instantaneous fluid motion has been limited due to momentum loss near the wall. To increase the feasibility of these devices, they have been used to drive a channel flow, creating a jet under quiescent conditions. Electrostatic Fluid Accelerators (EFA) have also been shown to drive internal gas flows. The present work draws on the success of the DBD driven plasma channels, while exploring a new electrode configuration that stems from EFA designs, in order to actuate more of the bulk fluid. Major parameters, applied voltage and operating frequency as well as electrode gap and choice of electrode (material, shape, size); were experimentally investigated using Particle Image Velocimetry to obtain time averaged, 2D velocity fields. Results indicate significant variation of performance with these parameters and suggest that in comparison to surface DBD actuators an order magnitude improvement in efficiency is possible. Furthermore, the qualitative aspect of an electro-fluid dynamic jet shows greater versatility in application for use as both boundary layer flow control and driving internal gas flows.

  7. 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.

  8. Computational fluid dynamics: Transition to design applications

    NASA Technical Reports Server (NTRS)

    Bradley, R. G.; Bhateley, I. C.; Howell, G. A.

    1987-01-01

    The development of aerospace vehicles, over the years, was an evolutionary process in which engineering progress in the aerospace community was based, generally, on prior experience and data bases obtained through wind tunnel and flight testing. Advances in the fundamental understanding of flow physics, wind tunnel and flight test capability, and mathematical insights into the governing flow equations were translated into improved air vehicle design. The modern day field of Computational Fluid Dynamics (CFD) is a continuation of the growth in analytical capability and the digital mathematics needed to solve the more rigorous form of the flow equations. Some of the technical and managerial challenges that result from rapidly developing CFD capabilites, some of the steps being taken by the Fort Worth Division of General Dynamics to meet these challenges, and some of the specific areas of application for high performance air vehicles are presented.

  9. Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)

    SciTech Connect

    Not Available

    2010-08-01

    Fact sheet describing NREL CSP Program capabilities in the area of thermal storage and advanced heat transfer fluids: measuring thermophysical properties, measuring fluid flow and heat transfer, and simulating flow of thermal energy and fluid.

  10. Fluid dynamics in developmental biology: moving fluids that shape ontogeny

    PubMed Central

    Cartwright, Julyan H.E.; Piro, Oreste; Tuval, Idan

    2009-01-01

    Human conception, indeed fertilization in general, takes place in a fluid, but what role does fluid dynamics have during the subsequent development of an organism? It is becoming increasingly clear that the number of genes in the genome of a typical organism is not sufficient to specify the minutiae of all features of its ontogeny. Instead, genetics often acts as a choreographer, guiding development but leaving some aspects to be controlled by physical and chemical means. Fluids are ubiquitous in biological systems, so it is not surprising that fluid dynamics should play an important role in the physical and chemical processes shaping ontogeny. However, only in a few cases have the strands been teased apart to see exactly how fluid forces operate to guide development. Here, we review instances in which the hand of fluid dynamics in developmental biology is acknowledged, both in human development and within a wider biological context, together with some in which fluid dynamics is notable but whose workings have yet to be understood, and we provide a fluid dynamicist’s perspective on possible avenues for future research. PMID:19794816

  11. Final Report: Computational Fluid Dynamics and Combustion Dynamics, February 15, 1995 - February 14, 1998

    SciTech Connect

    Colella, Phillip

    1998-09-22

    The HPCC Grand Challenge Project on Computational Fluid Dynamics and Combustion Dynamics focuses on the development of advanced numerical methodologies for modeling realistic engineering problems in combustion and other areas of fluid dynamics. The project was a collaboration between two DOE Laboratories (LBNL and LANL) and two universities (University of California, Berkeley, and New York University). In this document, we report on the work done under the UC Berkeley portion of the grant.

  12. "Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"

    SciTech Connect

    Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann

    2008-06-12

    ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers

  13. Kinetic foundations of relativistic dissipative fluid dynamics

    NASA Astrophysics Data System (ADS)

    Denicol, G. S.

    2014-12-01

    In this contribution we discuss in detail the most widespread formalisms employed to derive relativistic dissipative fluid dynamics from the Boltzmann equation: Chapman-Enskog expansion and Israel-Stewart theory. We further point out the drawbacks of each theory and explain possible ways to circumvent them. Recent developments in the derivation of fluid dynamics from the Boltzmann equation are also discussed.

  14. Nonlinear ship waves and computational fluid dynamics

    PubMed Central

    MIYATA, Hideaki; ORIHARA, Hideo; SATO, Yohei

    2014-01-01

    Research works undertaken in the first author’s laboratory at the University of Tokyo over the past 30 years are highlighted. Finding of the occurrence of nonlinear waves (named Free-Surface Shock Waves) in the vicinity of a ship advancing at constant speed provided the start-line for the progress of innovative technologies in the ship hull-form design. Based on these findings, a multitude of the Computational Fluid Dynamic (CFD) techniques have been developed over this period, and are highlighted in this paper. The TUMMAC code has been developed for wave problems, based on a rectangular grid system, while the WISDAM code treats both wave and viscous flow problems in the framework of a boundary-fitted grid system. These two techniques are able to cope with almost all fluid dynamical problems relating to ships, including the resistance, ship’s motion and ride-comfort issues. Consequently, the two codes have contributed significantly to the progress in the technology of ship design, and now form an integral part of the ship-designing process. PMID:25311139

  15. Nonlinear ship waves and computational fluid dynamics.

    PubMed

    Miyata, Hideaki; Orihara, Hideo; Sato, Yohei

    2014-01-01

    Research works undertaken in the first author's laboratory at the University of Tokyo over the past 30 years are highlighted. Finding of the occurrence of nonlinear waves (named Free-Surface Shock Waves) in the vicinity of a ship advancing at constant speed provided the start-line for the progress of innovative technologies in the ship hull-form design. Based on these findings, a multitude of the Computational Fluid Dynamic (CFD) techniques have been developed over this period, and are highlighted in this paper. The TUMMAC code has been developed for wave problems, based on a rectangular grid system, while the WISDAM code treats both wave and viscous flow problems in the framework of a boundary-fitted grid system. These two techniques are able to cope with almost all fluid dynamical problems relating to ships, including the resistance, ship's motion and ride-comfort issues. Consequently, the two codes have contributed significantly to the progress in the technology of ship design, and now form an integral part of the ship-designing process.

  16. Advanced Flicker Spectroscopy of Fluid Membranes

    NASA Astrophysics Data System (ADS)

    Döbereiner, Hans-Günther; Gompper, Gerhard; Haluska, Christopher; Kroll, Daniel; Petrov, Peter; Riske, Karin

    2003-07-01

    The bending elasticity of a fluid membrane is characterized by its modulus and spontaneous curvature. We present a new method, advanced flicker spectroscopy of giant nonspherical vesicles, which makes it possible to simultaneously measure both parameters for the first time. Our analysis is based on the generation of a large set of reference data from Monte Carlo simulations of randomly triangulated surfaces. As an example of the potential of the procedure, we monitor thermal trajectories of vesicle shapes and discuss the elastic response of zwitterionic membranes to transmembrane pH gradients. Our technique makes it possible to easily characterize membrane curvature as a function of environmental conditions.

  17. Fluid Dynamics of the Heart and its Valves

    NASA Astrophysics Data System (ADS)

    Peskin, Charles S.

    1997-11-01

    The fluid dynamics of the heart involve the interaction of blood, a viscous incompressible fluid, with the flexible, elastic, fiber-reinforced heart valve leaflets that are immersed in that fluid. Neither the fluid motion nor the valve leaflet motion are known in advance: both must be computed simultaneously by solving their coupled equations of motion. This can be done by the immersed boundary method(Peskin CS and McQueen DM: A general method for the computer simulation of biological systems interacting with fluids. In: Biological Fluid Dynamics (Ellington CP and Pedley TJ, eds.), The Company of Biologists Limited, Cambridge UK, 1995, pp. 265-276.), which can be extended to incorporate the contractile fiber architecture of the muscular heart walls as well as the valve leaflets and the blood. In this way we arrive at a three-dimensional computer model of the heart(Peskin CS and McQueen DM: Fluid dynamics of the heart and its valves. In: Case Studies in Mathematical Modeling: Ecology, Physiology, and Cell Biology (Othmer HG, Adler FR, Lewis MA, and Dallon JC, eds.), Prentice-Hall, Englewood Cliffs NJ, 1996, pp. 309-337.), which can be used as a test chamber for the design of prosthetic cardiac valves, and also to study the function of the heart in health and in disease. Numerical solutions of the equations of cardiac fluid dynamics obtained by the immersed boundary method will be presented in the form of a video animation of the beating heart.

  18. Potential applications of computational fluid dynamics to biofluid analysis

    NASA Technical Reports Server (NTRS)

    Kwak, D.; Chang, J. L. C.; Rogers, S. E.; Rosenfeld, M.; Kwak, D.

    1988-01-01

    Computational fluid dynamics was developed to the stage where it has become an indispensable part of aerospace research and design. In view of advances made in aerospace applications, the computational approach can be used for biofluid mechanics research. Several flow simulation methods developed for aerospace problems are briefly discussed for potential applications to biofluids, especially to blood flow analysis.

  19. Fundamentals and recent advances in X-ray micro computed tomography (microCT) applied on thermal-fluid dynamics and multiphase flows

    NASA Astrophysics Data System (ADS)

    Santini, Maurizio

    2015-11-01

    X-ray computed tomography (CT) is a well-known technique nowadays, since its first practical application by Sir. G. Hounsfield (Nobel price for medicine 1979) has continually benefited from optimising improvements, especially in medical applications. Indeed, also application of CT in various engineering research fields provides fundamental informations on a wide range of applications, considering that the technique is not destructive, allowing 3D visualization without perturbation of the analysed material. Nowadays, it is technologically possible to design and realize an equipment that achieve a micrometric resolution and even improve the sensibility in revealing differences in materials having very radiotransparency, allowing i.e. to distinguish between different fluids (with different density) or states of matter (like with two-phase flows). At the University of Bergamo, a prototype of an X-ray microCT system was developed since 2008, so being fully operative from 2012, with specific customizations for investigations in thermal-fluid dynamics and multiphase flow researches. A technical session held at the UIT International Conference in L'Aquila (Italy), at which this paper is referring, has presented some microCT fundamentals, to allow the audience to gain basics to follow the “fil-rouge” that links all the instrumentation developments, till the recent applications. Hereinafter are reported some applications currently developed at Bergamo University at the X-ray computed micro-tomography laboratory.

  20. Computational fluid dynamics in cardiovascular disease.

    PubMed

    Lee, Byoung-Kwon

    2011-08-01

    Computational fluid dynamics (CFD) is a mechanical engineering field for analyzing fluid flow, heat transfer, and associated phenomena, using computer-based simulation. CFD is a widely adopted methodology for solving complex problems in many modern engineering fields. The merit of CFD is developing new and improved devices and system designs, and optimization is conducted on existing equipment through computational simulations, resulting in enhanced efficiency and lower operating costs. However, in the biomedical field, CFD is still emerging. The main reason why CFD in the biomedical field has lagged behind is the tremendous complexity of human body fluid behavior. Recently, CFD biomedical research is more accessible, because high performance hardware and software are easily available with advances in computer science. All CFD processes contain three main components to provide useful information, such as pre-processing, solving mathematical equations, and post-processing. Initial accurate geometric modeling and boundary conditions are essential to achieve adequate results. Medical imaging, such as ultrasound imaging, computed tomography, and magnetic resonance imaging can be used for modeling, and Doppler ultrasound, pressure wire, and non-invasive pressure measurements are used for flow velocity and pressure as a boundary condition. Many simulations and clinical results have been used to study congenital heart disease, heart failure, ventricle function, aortic disease, and carotid and intra-cranial cerebrovascular diseases. With decreasing hardware costs and rapid computing times, researchers and medical scientists may increasingly use this reliable CFD tool to deliver accurate results. A realistic, multidisciplinary approach is essential to accomplish these tasks. Indefinite collaborations between mechanical engineers and clinical and medical scientists are essential. CFD may be an important methodology to understand the pathophysiology of the development and

  1. Fluid dynamics computer programs for NERVA turbopump

    NASA Technical Reports Server (NTRS)

    Brunner, J. J.

    1972-01-01

    During the design of the NERVA turbopump, numerous computer programs were developed for the analyses of fluid dynamic problems within the machine. Program descriptions, example cases, users instructions, and listings for the majority of these programs are presented.

  2. Fluid Dynamics of Human Phonation and Speech

    NASA Astrophysics Data System (ADS)

    Mittal, Rajat; Erath, Byron D.; Plesniak, Michael W.

    2013-01-01

    This article presents a review of the fluid dynamics, flow-structure interactions, and acoustics associated with human phonation and speech. Our voice is produced through the process of phonation in the larynx, and an improved understanding of the underlying physics of this process is essential to advancing the treatment of voice disorders. Insights into the physics of phonation and speech can also contribute to improved vocal training and the development of new speech compression and synthesis schemes. This article introduces the key biomechanical features of the laryngeal physiology, reviews the basic principles of voice production, and summarizes the progress made over the past half-century in understanding the flow physics of phonation and speech. Laryngeal pathologies, which significantly enhance the complexity of phonatory dynamics, are discussed. After a thorough examination of the state of the art in computational modeling and experimental investigations of phonatory biomechanics, we present a synopsis of the pacing issues in this arena and an outlook for research in this fascinating subject.

  3. Patterns and flow in frictional fluid dynamics

    PubMed Central

    Sandnes, B.; Flekkøy, E.G.; Knudsen, H.A.; Måløy, K.J.; See, H.

    2011-01-01

    Pattern-forming processes in simple fluids and suspensions have been studied extensively, and the basic displacement structures, similar to viscous fingers and fractals in capillary dominated flows, have been identified. However, the fundamental displacement morphologies in frictional fluids and granular mixtures have not been mapped out. Here we consider Coulomb friction and compressibility in the fluid dynamics, and discover surprising responses including highly intermittent flow and a transition to quasi-continuodynamics. Moreover, by varying the injection rate over several orders of magnitude, we characterize new dynamic modes ranging from stick-slip bubbles at low rate to destabilized viscous fingers at high rate. We classify the fluid dynamics into frictional and viscous regimes, and present a unified description of emerging morphologies in granular mixtures in the form of extended phase diagrams. PMID:21505444

  4. Interfacial gauge methods for incompressible fluid dynamics.

    PubMed

    Saye, Robert

    2016-06-01

    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

  5. 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

  6. AIR INGRESS ANALYSIS: COMPUTATIONAL FLUID DYNAMIC MODELS

    SciTech Connect

    Chang H. Oh; Eung S. Kim; Richard Schultz; Hans Gougar; David Petti; Hyung S. Kang

    2010-08-01

    The Idaho National Laboratory (INL), under the auspices of the U.S. Department of Energy, is performing research and development that focuses on key phenomena important during potential scenarios that may occur in very high temperature reactors (VHTRs). Phenomena Identification and Ranking Studies to date have ranked an air ingress event, following on the heels of a VHTR depressurization, as important with regard to core safety. Consequently, the development of advanced air ingress-related models and verification and validation data are a very high priority. Following a loss of coolant and system depressurization incident, air will enter the core of the High Temperature Gas Cooled Reactor through the break, possibly causing oxidation of the in-the core and reflector graphite structure. Simple core and plant models indicate that, under certain circumstances, the oxidation may proceed at an elevated rate with additional heat generated from the oxidation reaction itself. Under postulated conditions of fluid flow and temperature, excessive degradation of the lower plenum graphite can lead to a loss of structural support. Excessive oxidation of core graphite can also lead to the release of fission products into the confinement, which could be detrimental to a reactor safety. Computational fluid dynamic model developed in this study will improve our understanding of this phenomenon. This paper presents two-dimensional and three-dimensional CFD results for the quantitative assessment of the air ingress phenomena. A portion of results of the density-driven stratified flow in the inlet pipe will be compared with results of the experimental results.

  7. 'Fluid Dynamics,' mixed media by Tina York depicts fluid dynamics studies at the Ames Research

    NASA Technical Reports Server (NTRS)

    2001-01-01

    'Fluid Dynamics,' mixed media by Tina York depicts fluid dynamics studies at the Ames Research Center. The purpose of such studies is to learn more about what happens to an object when it encounters the friction of atmospheric resistence (such as a plane encountering resistance as it speeds through the air). used in Ames 60 year history by Glenn Bugos NASA SP-4314

  8. Fluid Dynamics in Sucker Rod Pumps

    SciTech Connect

    Cutler, R.P.; Mansure, A.J.

    1999-01-14

    Sucker rod pumps are installed in approximately 90% of all oil wells in the U.S. Although they have been widely used for decades, there are many issues regarding the fluid dynamics of the pump that have not been fully investigated. A project was conducted at Sandia National Laboratories to develop unimproved understanding of the fluid dynamics inside a sucker rod pump. A mathematical flow model was developed to predict pressures in any pump component or an entire pump under single-phase fluid and pumping conditions. Laboratory flow tests were conducted on instrumented individual pump components and on a complete pump to verify and refine the model. The mathematical model was then converted to a Visual Basic program to allow easy input of fluid, geometry and pump parameters and to generate output plots. Examples of issues affecting pump performance investigated with the model include the effects of viscosity, surface roughness, valve design details, plunger and valve pressure differentials, and pumping rate.

  9. Molecular dynamics simulations of microscale fluid transport

    SciTech Connect

    Wong, C.C.; Lopez, A.R.; Stevens, M.J.; Plimpton, S.J.

    1998-02-01

    Recent advances in micro-science and technology, like Micro-Electro-Mechanical Systems (MEMS), have generated a group of unique liquid flow problems that involve characteristic length scales of a Micron. Also, in manufacturing processes such as coatings, current continuum models are unable to predict microscale physical phenomena that appear in these non-equilibrium systems. It is suspected that in these systems, molecular-level processes can control the interfacial energy and viscoelastic properties at the liquid/solid boundary. A massively parallel molecular dynamics (MD) code has been developed to better understand microscale transport mechanisms, fluid-structure interactions, and scale effects in micro-domains. Specifically, this MD code has been used to analyze liquid channel flow problems for a variety of channel widths, e.g. 0.005-0.05 microns. This report presents results from MD simulations of Poiseuille flow and Couette flow problems and addresses both scaling and modeling issues. For Poiseuille flow, the numerical predictions are compared with existing data to investigate the variation of the friction factor with channel width. For Couette flow, the numerical predictions are used to determine the degree of slip at the liquid/solid boundary. Finally, the results also indicate that shear direction with respect to the wall lattice orientation can be very important. Simulation results of microscale Couette flow and microscale Poiseuille flow for two different surface structures and two different shear directions will be presented.

  10. Chaotic dynamics in dense fluids

    SciTech Connect

    Posch, H.A.; Hoover, W.G.

    1987-09-01

    We present calculations of the full spectra of Lyapunov exponents for 8- and 32-particle systems with periodic boundary conditions and interacting with the repulsive part of a Lennard-Jones potential both in equilibrium and nonequilibrium steady states. Lyapunov characteristic exponents lambda/sub n/ describe the mean exponential rates of divergence and convergence of neighbouring trajectories in phase-space. They are useful in characterizing the stochastic properties of a dynamical system. A new algorithm for their calculation is presented which incorporates ideas from control theory and constraint nonequilibrium molecular dynamics. 4 refs., 1 fig.

  11. Variational principles for stochastic fluid dynamics

    PubMed Central

    Holm, Darryl D.

    2015-01-01

    This paper derives stochastic partial differential equations (SPDEs) for fluid dynamics from a stochastic variational principle (SVP). The paper proceeds by taking variations in the SVP to derive stochastic Stratonovich fluid equations; writing their Itô representation; and then investigating the properties of these stochastic fluid models in comparison with each other, and with the corresponding deterministic fluid models. The circulation properties of the stochastic Stratonovich fluid equations are found to closely mimic those of the deterministic ideal fluid models. As with deterministic ideal flows, motion along the stochastic Stratonovich paths also preserves the helicity of the vortex field lines in incompressible stochastic flows. However, these Stratonovich properties are not apparent in the equivalent Itô representation, because they are disguised by the quadratic covariation drift term arising in the Stratonovich to Itô transformation. This term is a geometric generalization of the quadratic covariation drift term already found for scalar densities in Stratonovich's famous 1966 paper. The paper also derives motion equations for two examples of stochastic geophysical fluid dynamics; namely, the Euler–Boussinesq and quasi-geostropic approximations. PMID:27547083

  12. Dynamical studies of confined fluids and polymers

    NASA Astrophysics Data System (ADS)

    Grabowski, Christopher A.

    Soft matter, a class of materials including polymers, colloids, and surfactant molecules, are ubiquitous in our everyday lives. Plastics, soaps, foods and living organisms are mostly comprised of soft materials. Research conducted to understand soft matter behavior at the molecular level is essential to create new materials with unique properties. Self-healing plastics, targeted drug delivery, and nanowire assemblies have all been further advanced by soft matter research. The author of this dissertation investigates fundamental soft matter systems, including polymer solutions and melts, colloid dispersions in polymer melts, and interfacial fluids. The dynamics of polymers and confined fluids were studied using the single-molecule sensitive technique of fluorescence correlation spectroscopy (FCS). Here, fluorescent dyes are attached to polymer coils or by introducing free dyes directly into the solution/film. Complementary experiments were also performed, utilizing atomic force microscopy (AFM) and ellipsometry. FCS and AFM experiments demonstrated the significant difference in properties of thin fluid films of the nearly spherical, nonpolar molecule TEHOS (tetrakis(2-ethylhexoxy)silane) when compared to its bulk counterpart. AFM experiments confirmed TEHOS orders in layers near a solid substrate. FCS experiments show that free dyes introduced in these thin films do not have a single diffusion coefficient, indicating that these films have heterogeneity at the molecular level. FCS experiments have been applied to study the diffusion of gold colloids. The diffusion of gold colloids in polymer melts was found to dramatically depart from the Stokes-Einstein prediction when colloid size was smaller than the surrounding polymer mesh size. This effect is explained by noting the viscosity experienced by the colloid is not equivalent to the overall bulk viscosity of the polymer melt. The conformational change of polymers immersed in a binary solvent was measured via FCS

  13. The Fluid Dynamics of Plumes

    NASA Astrophysics Data System (ADS)

    Hansen, U.

    Plumes form as instabilities from thermal boundary layers of convecting systems.The shape, the size and the temporal evolution of plumes is strongly influenced by the vis- cosity of the material. Employing a numerical scheme the evolution of plumes in fluids with strong temperature and temperature-pressure dependent viscosity has been stud- ied. The strong dependence of viscosity on temperature leads to a pulse-like evolution of the plumes.Pulses of hot material rise episodically through the pre-established low viscosity channels. In a later stage the plumes generate extended network-like struc- tures in the thermal boundary layers. Pressure dependence of the viscosity leads to a significant cooling of the plumes.Furthe a fragmentation of one plume into several smaller ones is commonly observed. While internal convection takes place within the plume head, only little entrainment of material is observed.

  14. Computational fluid dynamics - A personal view

    NASA Technical Reports Server (NTRS)

    Hussaini, M. Y.

    1989-01-01

    This paper provides a personal view of computational fluid dynamics. The main theme is divided into two categories - one dealing with algorithms and engineering applications and the other with scientific investigations. The former category may be termed computational aerodynamics, with the objective of providing reliable aerodynamic or engineering predictions. The latter category is essentially basic research, where the algorithmic tools are used to unravel and elucidate fluid-dynamic phenomena hard to obtain in a laboratory. A critique of the numerical solution techniques for both compressible and incompressible flows is included. The discussion on scientific investigations deals in particular with transition and turbulence.

  15. Reduced MHD and Astrophysical Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Arter, Wayne

    2011-08-01

    Recent work has shown a relationship between between the equations of Reduced Magnetohydrodynamics (RMHD), used to model magnetic fusion laboratory experiments, and incompressible magnetoconvection (IMC), employed in the simulation of astrophysical fluid dynamics (AFD), which means that the two systems are mathematically equivalent in certain geometries. Limitations on the modelling of RMHD, which were found over twenty years ago, are reviewed for an AFD audience, together with hitherto unpublished material on the role of finite-time singularities in the discrete equations used to model fluid dynamical systems. Possible implications for turbulence modelling are mentioned.

  16. Fluid Dynamic Verification Experiments on STS-70

    NASA Technical Reports Server (NTRS)

    Kleis, Stanley J.

    1996-01-01

    Fluid dynamic experiments were flown on STS-70 as phase two of the engineering evaluation of the first bioreactor Engineering Development Unit (EDU#1). The phase one experiments were comparative cell cultures in identical units on earth and onboard STS-70. In phase two, two types of fluid dynamic experiments were performed. Qualitative comparisons of the basic flow patterns were evaluated with the use of 'dye' streaklines formed from alternate injections of either a mild acid or base solution into the external flow loop that was then perfused into the vessel. The presence of Bromothymol Blue in the fluid then caused color changes from yellow to blue or vice versa, indicating the basic fluid motions. This reversible change could be repeated as desired. In the absence of significant density differences in the fluid, the flow patterns in space should be the same as on earth. Video tape records of the flow patterns for a wide range of operating conditions were obtained. The second type of fluid dynamic experiment was the quantitative evaluation of the trajectories of solid beads of various densities and sizes. The beads were introduced into the vessel and the paths recorded on video tape, with the vessel operated at various rotation rates and flow perfusion rates. Because of space limitations, the video camera was placed as close as possible to the vessel, resulting in significant optical distortion. This report describes the analysis methods to obtain comparisons between the in-flight fluid dynamics and numerical models of the flow field. The methods include optical corrections to the video images and calculation of the bead trajectories for given operating conditions and initial bead locations.

  17. Particle dynamics in fluids with random interactions

    NASA Astrophysics Data System (ADS)

    Shagolsem, Lenin S.; Rabin, Yitzhak

    2016-05-01

    We study the dynamics of particles in a multi-component 2d Lennard-Jones (LJ) fluid in the limiting case where all the particles are different (APD). The equilibrium properties of this APD system were studied in our earlier work [L. S. Shagolsem et al., J. Chem. Phys. 142, 051104 (2015).]. We use molecular dynamics simulations to investigate the statistical properties of particle trajectories in a temperature range covering both the fluid and the solid-fluid coexistence region. We calculate the mean-square displacement as well as displacement, angle, and waiting time distributions, and compare the results with those for one-component LJ fluid. As temperature is lowered, the dynamics of the APD system becomes increasingly complex, as the intrinsic difference between the particles is amplified by neighborhood identity ordering and by the inhomogeneous character of the solid-fluid coexistence region. The ramifications of our results for the analysis of protein tracking experiments in living cells are discussed.

  18. Fluid dynamics in porous media with Sailfish

    NASA Astrophysics Data System (ADS)

    Coelho, Rodrigo C. V.; Neumann, Rodrigo F.

    2016-09-01

    In this work we show the application of Sailfish to the study of fluid dynamics in porous media. Sailfish is an open-source software based on the lattice-Boltzmann method. This application of computational fluid dynamics is of particular interest to the oil and gas industry and the subject could be a starting point for an undergraduate or graduate student in physics or engineering. We built artificial samples of porous media with different porosities and used Sailfish to simulate the fluid flow through them in order to calculate their permeability and tortuosity. We also present a simple way to obtain the specific superficial area of porous media using Python libraries. To contextualise these concepts, we analyse the applicability of the Kozeny-Carman equation, which is a well-known permeability-porosity relation, to our artificial samples.

  19. The Fluid Dynamics of Competitive Swimming

    NASA Astrophysics Data System (ADS)

    Wei, Timothy; Mark, Russell; Hutchison, Sean

    2014-01-01

    Nowhere in sport is performance so dependent on the interaction of the athlete with the surrounding medium than in competitive swimming. As a result, understanding (at least implicitly) and controlling (explicitly) the fluid dynamics of swimming are essential to earning a spot on the medal stand. This is an extremely complex, highly multidisciplinary problem with a broad spectrum of research approaches. This review attempts to provide a historical framework for the fluid dynamics-related aspects of human swimming research, principally conducted roughly over the past five decades, with an emphasis on the past 25 years. The literature is organized below to show a continuous integration of computational and experimental technologies into the sport. Illustrations from the authors' collaborations over a 10-year period, coupling the knowledge and experience of an elite-level coach, a lead biomechanician at USA Swimming, and an experimental fluid dynamicist, are intended to bring relevance and immediacy to the review.

  20. Environmental Fluid Dynamics in Space Capsule

    NASA Astrophysics Data System (ADS)

    Yin, Zhaohua

    Environmental fluid dynamics began to get more and more concern recently because of its effects on indoor air quality and ventilation strategy. Our research is trying to use the tools of Environmental fluid dynamics to investigate the life support system (LSS) for manned space flight, especially for future long-term planetary exploration flight (permanent space station and lunar base, space greenhouse of controlled ecological life support systems (CELSS) etc.). The PIV technique will be adopted to obtain the velocity of the flow field and dyed fluids to capture the temperature field. On the other hand, we will use the commercial software (FLUENT) to numerical simulate the same problem. The results in this work can be used to improve the ventilation efficiency, reduce the energy costs and try to make the air in space capsule less effluvial.

  1. Fluid dynamics in porous media with Sailfish

    NASA Astrophysics Data System (ADS)

    Coelho, Rodrigo C. V.; Neumann, Rodrigo F.

    2016-09-01

    In this work we show the application of Sailfish to the study of fluid dynamics in porous media. Sailfish is an open-source software based on the lattice-Boltzmann method. This application of computational fluid dynamics is of particular interest to the oil and gas industry and the subject could be a starting point for an undergraduate or graduate student in physics or engineering. We built artificial samples of porous media with different porosities and used Sailfish to simulate the fluid flow through them in order to calculate their permeability and tortuosity. We also present a simple way to obtain the specific superficial area of porous media using Python libraries. To contextualise these concepts, we analyse the applicability of the Kozeny–Carman equation, which is a well-known permeability–porosity relation, to our artificial samples.

  2. Nonlinear astrophysical fluid dynamics: the video.

    NASA Astrophysics Data System (ADS)

    Norman, M. L.

    A videotape has been assembled containing animations shown by speakers at the Nonlinear Astrophysical Fluid Dynamics Conference. This videotape forms a useful supplement to the conference proceedings. The videotape is available from the National Center for Supercomputing Applications for the cost of materials (6 for 1/2″tapes; 12.50 for 3/4″tapes) and shipping.

  3. Computational fluid dynamics in oil burner design

    SciTech Connect

    Butcher, T.A.

    1997-09-01

    In Computational Fluid Dynamics, the differential equations which describe flow, heat transfer, and mass transfer are approximately solved using a very laborious numerical procedure. Flows of practical interest to burner designs are always turbulent, adding to the complexity of requiring a turbulence model. This paper presents a model for burner design.

  4. V/STOL aircraft and fluid dynamic

    NASA Astrophysics Data System (ADS)

    Roberts, L.; Anderson, S. B.

    1982-01-01

    The impact of military applications on rotorcraft and V/STOL aircraft design with respect to fixed wing aircraft is discussed. The influence of the mission needs on the configurational design of V/STOL aircraft, the implications regarding some problems in fluid dynamics relating to propulsive flows, and their interaction with the aircraft and the ground plane, are summarized.

  5. Dynamics of squeezing fluids: Clapping wet hands

    NASA Astrophysics Data System (ADS)

    Gart, Sean; Chang, Brian; Slama, Brice; Goodnight, Randy; Um, Soong Ho; Jung, Sunghwan

    2013-08-01

    Droplets splash around when a fluid volume is quickly compressed. This phenomenon has been observed during common activities such as kids clapping with wet hands. The underlying mechanism involves a fluid volume being compressed vertically between two objects. This compression causes the fluid volume to be ejected radially and thereby generate fluid threads and droplets at a high speed. In this study, we designed and performed laboratory experiments to observe the process of thread and drop formation after a fluid is squeezed. A thicker rim at the outer edge forms and moves after the squeezing, and then becomes unstable and breaks into smaller drops. This process differs from previous well-known examples (i.e., transient crown splashes and continuous water bells) in aspects of transient fluid feeding, expanding rim dynamics, or sparsely distributed drops. We compared experimental measurements with theoretical models over three different stages; early squeezing, intermediate sheet-expansion, and later break-up of the liquid thread. In the earlier stage, the fluid is squeezed and its initial velocity is governed by the lubrication force. The outer rim of the liquid sheet forms curved trajectories due to gravity, inertia, drag, and surface tension. At the late stage, drop spacing set by the initial capillary instability does not change in the course of rim expansion, consequently final ejected droplets are very sparse compared to the size of the rim.

  6. Computational fluid dynamics in a marine environment

    NASA Technical Reports Server (NTRS)

    Carlson, Arthur D.

    1987-01-01

    The introduction of the supercomputer and recent advances in both Reynolds averaged, and large eddy simulation fluid flow approximation techniques to the Navier-Stokes equations, have created a robust environment for the exploration of problems of interest to the Navy in general, and the Naval Underwater Systems Center in particular. The nature of problems that are of interest, and the type of resources needed for their solution are addressed. The goal is to achieve a good engineering solution to the fluid-structure interaction problem. It is appropriate to indicate that a paper by D. Champman played a major role in developing the interest in the approach discussed.

  7. Effects of fluid dynamics on cleaning efficacy of supercritical fluids

    SciTech Connect

    Phelps, M.R.; Willcox, W.A.; Silva, L.J.; Butner, R.S.

    1993-03-01

    Pacific Northwest Laboratory (PNL) and Boeing Aerospace Company are developing a process to clean metal parts using a supercritical solvent. This work is part of an effort to address issues inhibiting the rapid commercialization of Supercritical Fluid Parts Cleaning (SFPC). PNL assembled a SFPC test stand to observe the relationship between the fluid dynamics of the system and the mass transfer of a contaminant from the surface of a contaminated metal coupon into the bulk fluid. The bench-scale test stand consists of a ``Berty`` autoclave modified for these tests and supporting hardware to achieve supercritical fluids parts cleaning. Three separate sets of tests were conducted using supercritical carbon dioxide. For the first two tests, a single stainless steel coupon was cleaned with organic solvents to remove surface residue, doped with a single contaminant, and then cleaned in the SFPC test stand. Contaminants studied were Dow Corning 200 fluid (dimethylpolysiloxane) and Castle/Sybron X-448 High-temperature Oil (a polybutane/mineral oil mixture). A set of 5-minute cleaning runs was conducted for each dopant at various autoclave impeller speeds. Test results from the first two sets of experiments indicate that precision cleaning for difficult-to-remove contaminants can be dramatically improved by introducing and increasing turbulence within the system. Metal coupons that had been previously doped with aircraft oil were used in a third set of tests. The coupons were placed in the SFPC test stand and subjected to different temperatures, pressures, and run times at a constant impeller speed. The cleanliness of each part was measured by Optically Stimulated Electron Emission. The third set of tests show that levels of cleanliness attained with supercritical carbon dioxide compare favorably with solvent and aqueous cleaning levels.

  8. Effects of fluid dynamics on cleaning efficacy of supercritical fluids

    SciTech Connect

    Phelps, M.R.; Willcox, W.A.; Silva, L.J.; Butner, R.S.

    1993-03-01

    Pacific Northwest Laboratory (PNL) and Boeing Aerospace Company are developing a process to clean metal parts using a supercritical solvent. This work is part of an effort to address issues inhibiting the rapid commercialization of Supercritical Fluid Parts Cleaning (SFPC). PNL assembled a SFPC test stand to observe the relationship between the fluid dynamics of the system and the mass transfer of a contaminant from the surface of a contaminated metal coupon into the bulk fluid. The bench-scale test stand consists of a Berty'' autoclave modified for these tests and supporting hardware to achieve supercritical fluids parts cleaning. Three separate sets of tests were conducted using supercritical carbon dioxide. For the first two tests, a single stainless steel coupon was cleaned with organic solvents to remove surface residue, doped with a single contaminant, and then cleaned in the SFPC test stand. Contaminants studied were Dow Corning 200 fluid (dimethylpolysiloxane) and Castle/Sybron X-448 High-temperature Oil (a polybutane/mineral oil mixture). A set of 5-minute cleaning runs was conducted for each dopant at various autoclave impeller speeds. Test results from the first two sets of experiments indicate that precision cleaning for difficult-to-remove contaminants can be dramatically improved by introducing and increasing turbulence within the system. Metal coupons that had been previously doped with aircraft oil were used in a third set of tests. The coupons were placed in the SFPC test stand and subjected to different temperatures, pressures, and run times at a constant impeller speed. The cleanliness of each part was measured by Optically Stimulated Electron Emission. The third set of tests show that levels of cleanliness attained with supercritical carbon dioxide compare favorably with solvent and aqueous cleaning levels.

  9. Fluid Dynamics of Bubbly Liquids

    NASA Technical Reports Server (NTRS)

    Tsang, Y. H.; Koch, D. L.; Zenit, R.; Sangani, A.; Kushch, V. I.; Spelt, P. D. M.; Hoffman, M.; Nahra, H.; Fritz, C.; Dolesh, R.

    2002-01-01

    Experiments have been performed to study the average flow properties of inertially dominated bubbly liquids which may be described by a novel analysis. Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The suspension was produced using a bank of 900 glass capillaries with inner diameter of about 100 microns in a quasi-steady fashion. In addition, salt was added to the suspension to prevent bubble-bubble coalescence. As a result, a nearly monodisperse suspension of bubble was produced. By increasing the inclination angle, we were able to explore an increasing amount of shear to buoyancy motion. A pipe flow experiment with the liquid being recirculated is under construction. This will provide an even larger range of shear to buoyancy motion. We are planning a microgravity experiment in which a bubble suspension is subjected to shearing in a couette cell in the absence of a buoyancy-driven relative motion of the two phases. By employing a single-wire, hot film anemometer, we were able to obtain the liquid velocity fluctuations. The shear stress at the wall was measured using a hot film probe flush mounted on the wall. The gas volume fraction, bubble velocity, and bubble velocity fluctuations were measured using a homemade, dual impedance probe. In addition, we also employed a high-speed camera to obtain the bubble size distribution and bubble shape in a dilute suspension. A rapid decrease in bubble velocity for a dilute bubble suspension is attributed to the effects of bubble-wall collisions. The more gradual decrease of bubble velocity as gas volume fraction increases, due to subsequent hindering of bubble motion, is in qualitative agreement with the predictions of Spelt and Sangani for the effects of potential-flow bubble-bubble interactions on the mean velocity. The

  10. Advances in cardiovascular fluid mechanics: bench to bedside.

    PubMed

    Dasi, Lakshmi P; Sucosky, Philippe; de Zelicourt, Diane; Sundareswaran, Kartik; Jimenez, Jorge; Yoganathan, Ajit P

    2009-04-01

    This paper presents recent advances in cardiovascular fluid mechanics that define the current state of the art. These studies include complex multimodal investigations with advanced measurement and simulation techniques. We first discuss the complex flows within the total cavopulmonary connection in Fontan patients. We emphasize the quantification of energy losses by studying the importance of caval offsets as well as the differences among various Fontan surgical protocols. In our studies of the fluid mechanics of prosthetic heart valves, we reveal for the first time the full three-dimensional complexity of flow fields in the vicinity of bileaflet and trileaflet valves and the microscopic hinge flow dynamics. We also present results of these valves functioning in a patient-specific native aorta geometry. Our in vitro mitral valve studies show the complex mechanism of the native mitral valve apparatus. We demonstrate that the different components of the mitral valve have independent and synergistically complex functions that allow the valve to operate efficiently. We also show how valve mechanics change under pathological and repair conditions associated with enlarged ventricles. Finally, our ex vivo studies on the interactions between the aortic valve and its surrounding hemodynamic environment are aimed at providing insights into normal valve function and valve pathology. We describe the development of organ- and tissue-culture systems and the biological response of the tissue subjected to their respective simulated mechanical environment. The studies noted above have enhanced our understanding of the complex fluid mechanics associated with the cardiovascular system and have led to new translational technologies.

  11. Techniques for animation of CFD results. [computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Horowitz, Jay; Hanson, Jeffery C.

    1992-01-01

    Video animation is becoming increasingly vital to the computational fluid dynamics researcher, not just for presentation, but for recording and comparing dynamic visualizations that are beyond the current capabilities of even the most powerful graphic workstation. To meet these needs, Lewis Research Center has recently established a facility to provide users with easy access to advanced video animation capabilities. However, producing animation that is both visually effective and scientifically accurate involves various technological and aesthetic considerations that must be understood both by the researcher and those supporting the visualization process. These considerations include: scan conversion, color conversion, and spatial ambiguities.

  12. Advances in fluid resuscitation of hemorrhagic shock

    PubMed Central

    Tremblay, Lorraine N.; Rizoli, Sandro B.; Brenneman, Frederick D.

    2001-01-01

    The optimal fluid for resuscitation in hemorrhagic shock would combine the volume expansion and oxygen-carrying capacity of blood without the need for cross-matching or the risk of disease transmission. Although the ideal fluid has yet to be discovered, current options are discussed in this review, including crystalloids, colloids, blood and blood substitutes. The future role of blood substitutes is not yet defined, but the potential advantages in trauma or elective surgery may prove to be enormous. PMID:11407826

  13. Fluid-dynamical model for antisurfactants

    NASA Astrophysics Data System (ADS)

    Conn, Justin J. A.; Duffy, Brian R.; Pritchard, David; Wilson, Stephen K.; Halling, Peter J.; Sefiane, Khellil

    2016-04-01

    We construct a fluid-dynamical model for the flow of a solution with a free surface at which surface tension acts. This model can describe both classical surfactants, which decrease the surface tension of the solution relative to that of the pure solvent, and antisurfactants (such as many salts when added to water, and small amounts of water when added to alcohol) which increase it. We demonstrate the utility of the model by considering the linear stability of an infinitely deep layer of initially quiescent fluid. In particular, we predict the occurrence of an instability driven by surface-tension gradients, which occurs for antisurfactant, but not for surfactant, solutions.

  14. Modeling Tools Predict Flow in Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    2010-01-01

    "Because rocket engines operate under extreme temperature and pressure, they present a unique challenge to designers who must test and simulate the technology. To this end, CRAFT Tech Inc., of Pipersville, Pennsylvania, won Small Business Innovation Research (SBIR) contracts from Marshall Space Flight Center to develop software to simulate cryogenic fluid flows and related phenomena. CRAFT Tech enhanced its CRUNCH CFD (computational fluid dynamics) software to simulate phenomena in various liquid propulsion components and systems. Today, both government and industry clients in the aerospace, utilities, and petrochemical industries use the software for analyzing existing systems as well as designing new ones."

  15. Advanced binary cycles: Optimum working fluids

    SciTech Connect

    Gawlik, K.; Hassani, V.

    1997-12-31

    A computer model (Cycle Analysis Simulation Tool, CAST) and a methodology have been developed to perform value analysis for small, low- to moderate-temperature binary geothermal power plants. The value analysis method allows for incremental changes in the levelized electricity cost (LEC) to be determined between a baseline plant and a modified plant. Thermodynamic cycle analyses and component sizing are carried out in the model followed by economic analysis which provides LEC results. The emphasis of the present work is on evaluating the effect of mixed working fluids instead of pure fluids on the LEC of a geothermal binary plant that uses a simple Organic Rankine Cycle. Four resources were studied spanning the range of 265{degrees}F to 375{degrees}F. A variety of isobutane and propane based mixtures, in addition to pure fluids, were used as working fluids. This study shows that the use of propane mixtures at a 265{degrees}F resource can reduce the LEC by 24% when compared to a base case value that utilizes commercial isobutane as its working fluid. The cost savings drop to 6% for a 375{degrees}F resource, where an isobutane mixture is favored. Supercritical cycles were found to have the lowest cost at all resources.

  16. Advanced binary cycles: Optimum working fluids

    SciTech Connect

    Gawlik, K.; Hassani, V.

    1997-12-31

    A computer model (Cycle Analysis Simulation Tool, CAST) and a methodology have been developed to perform value analysis for small, low- to moderate-temperature binary geothermal power plants. The value analysis method allows for incremental changes in the levelized electricity cost (LEC) to be determined between a baseline plant and a modified plant. Thermodynamic cycle analyses and component sizing are carried out in the model followed by economic analysis which provides LEC results. The emphasis of the present work is on evaluating the effect of mixed working fluids instead of pure fluids on the LEC of a geothermal binary plant that uses a simple Organic Rankine Cycle. Four resources were studied spanning the range of 265 F to 375 F. A variety of isobutane and propane based mixtures, in addition to pure fluids, were used as working fluids. This study shows that the use of propane mixtures at a 265 F resource can reduce the LEC by 24% when compared to a base case value that utilizes commercial isobutane as its working fluid. The cost savings drop to 6% for a 375 F resource, where an isobutane mixture is favored. Supercritical cycles were found to have the lowest cost at all resources.

  17. Collective dynamics of sperm in viscoelastic fluid

    NASA Astrophysics Data System (ADS)

    Tung, Chih-Kuan; Harvey, Benedict B.; Fiore, Alyssa G.; Ardon, Florencia; Suarez, Susan S.; Wu, Mingming

    Collective dynamics in biology is an interesting subject for physicists, in part because of its close relations to emergent behaviors in condensed matter, such as phase separation and criticality. However, the emergence of order is often less drastic in systems composed of the living cells, sometimes due to the natural variability among individual organisms. Here, using bull sperm as a model system, we demonstrate that the cells migrate collectively in viscoelastic fluids, exhibiting behavior similar to ``flocking''. This collectiveness is greatly reduced in similarly viscous Newtonian fluids, suggesting that the cell-cell interaction is primarily a result of the elastic property or the memory effect of the fluids, instead of pure hydrodynamic interactions. Unlike bacterial swarming, this collectiveness does not require a change in phenotype of the cells; therefore, it is a better model system for physicists. Supported by NIH grant 1R01HD070038.

  18. Advanced Heat Transfer and Thermal Storage Fluids

    SciTech Connect

    Moens, L.; Blake, D.

    2005-01-01

    The design of the next generation solar parabolic trough systems for power production will require the development of new thermal energy storage options with improved economics or operational characteristics. Current heat-transfer fluids such as VP-1?, which consists of a eutectic mixture of biphenyl and diphenyl oxide, allow a maximum operating temperature of ca. 300 C, a limit above which the vapor pressure would become too high and would require pressure-rated tanks. The use of VP-1? also suffers from a freezing point around 13 C that requires heating during cold periods. One of the goals for future trough systems is the use of heat-transfer fluids that can act as thermal storage media and that allow operating temperatures around 425 C combined with lower limits around 0 C. This paper presents an outline of our latest approach toward the development of such thermal storage fluids.

  19. The fluid dynamics of human birth

    NASA Astrophysics Data System (ADS)

    Lehn, Andrea; Leftwich, Megan C.

    2012-11-01

    This study investigates the fluid dynamics associated with the human birth process. Specifically, we investigate the role of the viscosity of the amniotic fluid in transferring force from the contracting uterus to the fetus during delivery. This experimental work uses an approximate uterus and dilated cervix-fabricated with liquid latex-filled with a fluid of known viscosity and an oblong solid fetus. The force required to extract the fetus is recorded for several values of amniotic viscosity. The study looks at both pull-out force values (where the fetus is pulled from outside the uterus) and push-out force values (where pressure in the experimental uterus is used to remove the fetus). In addition to the viscosity study, we also investigate the increased force required to deliver an offset fetus by tilting the major axis of the oblong fetus and repeating the pull-and push-out experiments. This study will provide knowledge about the fundamental fluid dynamic processes involved in human birth.

  20. Fluid Dynamics in Sucker Rod Pumps

    SciTech Connect

    Cutler, Robert P.; Mansure, Arthur J.

    1999-06-01

    Sucker rod pumps are installed in approximately 90% of all oil wells in the U.S. Although they have been widely used for decades, there are many issues regarding the fluid dynamics of the pump that have not been filly investigated. A project was conducted at Sandia National Laboratories to develop an improved understanding of the fluid dynamics inside a sucker rod pump. A mathematical flow model was developed to predict pressures in any pump component or an entire pump under single-phase fluid and pumping conditions. Laboratory flow tests were conducted on instrumented individual pump components and on a complete pump to verifi and refine the model. The mathematical model was then converted to a Visual Basic program to allow easy input of fluid, geometry and pump parameters and to generate output plots. Examples of issues affecting pump performance investigated with the model include the effects of viscosity, surface roughness, valve design details, plunger and valve pressure differentials, and pumping rate.

  1. Glassy dynamics in a confined monatomic fluid

    NASA Astrophysics Data System (ADS)

    Krishnan, S. H.; Ayappa, K. G.

    2012-07-01

    Molecular dynamic simulations of a strongly inhomogeneous system reveals that a single-component soft-sphere fluid can behave as a fragile glass former due to confinement. The self-intermediate scattering function, Fs(k,t), of a Lennard-Jones fluid confined in slit-shaped pores, which can accomodate two to four fluid layers, exhibits a two-step relaxation at moderate temperatures. The mean-squared displacement data are found to follow time-temperature superposition and both the self-diffusivity and late α relaxation times exhibit power-law divergences as the fluid is cooled. The system possesses a crossover temperature and follows the scalings of mode coupling theory for the glass transition. The temperature dependence of the self-diffusivity can be expressed using the Vogel-Fulcher-Tammann equation, and estimates of the fragility index of the system indicates a fragile glass former. At lower temperatures, signatures of additional relaxation processes are observed in the various dynamical quantities with a three-step relaxation observed in the Fs(k,t).

  2. GMRES acceleration of computational fluid dynamics codes

    NASA Technical Reports Server (NTRS)

    Wigton, L. B.; Yu, N. J.; Young, D. P.

    1985-01-01

    The generalized minimal residual algorithm (GMRES) is a conjugate-gradient like method that applies directly to nonsymmetric linear systems of equations. In this paper, GMRES is modified to handle nonlinear equations characteristic of computational fluid dynamics. Attention is devoted to the concept of preconditioning and the role it plays in assuring rapid convergence. A formulation is developed that allows GMRES to be preconditioned by the solution procedures already built into existing computer codes. Examples are provided that demonstrate the ability of GMRES to greatly improve the robustness and rate of convergence of current state-of-the-art fluid dynamics codes. Theoretical aspects of GMRES are presented that explain why it works. Finally, the advantage GMRES enjoys over related methods such as conjugate gradients are discussed.

  3. Fluid dynamics of cytotoxic safety cabinets.

    PubMed

    Braconnier, R; Bonthoux, F

    2010-03-01

    This study investigated the specific fluid dynamics characteristics of cytotoxic safety cabinets (CSC), particularly those used in cancer drug reconstitution operations. Measurements taken on site were used to derive characteristic data for these cabinets. An in-depth laboratory investigation of airflows inside another CSC was also conducted. Anemometric values recorded on these two installations enabled the experimental validation of computational fluid dynamics methods applied to CSC. The digital flow simulations conducted provide a better understanding of the detailed flow structure inside a CSC and made it possible to study the influence of different operating parameters on the air velocity distribution inside the cabinet front opening: recycled air temperature, product protection airflow rate, suction openings spatial distribution, air compensation mode and draughts, operator arm penetration, and operator presence in front of the cabinet. PMID:20007340

  4. Isentropic fluid dynamics in a curved pipe

    NASA Astrophysics Data System (ADS)

    Colombo, Rinaldo M.; Holden, Helge

    2016-10-01

    In this paper we study isentropic flow in a curved pipe. We focus on the consequences of the geometry of the pipe on the dynamics of the flow. More precisely, we present the solution of the general Cauchy problem for isentropic fluid flow in an arbitrarily curved, piecewise smooth pipe. We consider initial data in the subsonic regime, with small total variation about a stationary solution. The proof relies on the front-tracking method and is based on [1].

  5. Geometric methods in computational fluid dynamics. [turbomachinery

    NASA Technical Reports Server (NTRS)

    Eiseman, P. R.

    1980-01-01

    General methods for the construction of geometric computational fluid dynamic algorithms are presented which simulate a variety of flow fields in various nontrivial regions. Included are: basic developments with tensors; various forms for the equations of motion; generalized numerical methods and boundary conditions; and methods for mesh generation to meet the strong geometric constraints of turbomachines. Coordinate generation is shown generally to yield mesh descriptions from one or more transformations that are smoothly joined together to form a composite mesh.

  6. Delaunay triangulation and computational fluid dynamics meshes

    NASA Technical Reports Server (NTRS)

    Posenau, Mary-Anne K.; Mount, David M.

    1992-01-01

    In aerospace computational fluid dynamics (CFD) calculations, the Delaunay triangulation of suitable quadrilateral meshes can lead to unsuitable triangulated meshes. Here, we present case studies which illustrate the limitations of using structured grid generation methods which produce points in a curvilinear coordinate system for subsequent triangulations for CFD applications. We discuss conditions under which meshes of quadrilateral elements may not produce a Delaunay triangulation suitable for CFD calculations, particularly with regard to high aspect ratio, skewed quadrilateral elements.

  7. Thin film dynamics of viscoelastic fluids

    NASA Astrophysics Data System (ADS)

    Lebon, Luc; Limat, Laurent

    2012-11-01

    We present here viscoelastic fluids in thin film flows, such as liquid bells or liquid curtains. The viscoelastic property of the liquids exhibits specific dynamics in such flows. In the case of bells, the elastic strength tends to extend the bell size for example. In the case of curtain flows, original behaviour of holes are observed with specific growth mechanism for bubbles trapped in the flow.

  8. Advanced designs for fluid flow visualization

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Research was carried out on existing and new designs for minimally intrusive measurement of flow fields in the Geophysical Fluid Flow Cell and the proposed Atmospheric General Circulation Experiment. The following topics are discussed: (1) identification and removal of foreign particles, (2) search for higher dielectric photochromic solutions, (3) selection of uv light source, (4) analysis of refractive techniques and (5) examination of fresnel lens applicability.

  9. Application of computational fluid dynamics techniques to blood pumps.

    PubMed

    Sukumar, R; Athavale, M M; Makhijani, V B; Przekwas, A J

    1996-06-01

    Present-day computational fluid dynamics (CFD) techniques can be used to analyze the behavior of fluid flow in a variety of pumps. CFD can be a powerful tool during the design stage for rapid virtual prototyping of different designs, analyzing performance parameters, and making design improvements. Computational flow solutions provide information such as the location and size of stagnation zones and the local shear rate. These parameters can be correlated to the extent of hemolysis and thrombus formation and are critical to the success of a blood pump. CFD-ACE, an advanced commercial CFD code developed by CFD Research Corporation, has been applied to fluid flows in rotary machines, such as axial flow pumps and inducers. Preprocessing and postprocessing tools for efficient grid generation and advanced graphical flow visualization are integrated seamlessly with CFD-ACE. The code has structured multiblock grid capability, non-Newtonian fluid treatment, a variety of turbulence models, and an Eulerian-Langrangian particle tracking model. CFD-ACE has been used successfully to study the flow characteristics in an axial flow blood pump. An unstructured flow solver that greatly automates the process of grid generation and speeds up the flow simulation is under development. PMID:8817950

  10. The fluid dynamics of the chocolate fountain

    NASA Astrophysics Data System (ADS)

    Townsend, Adam K.; Wilson, Helen J.

    2016-01-01

    We consider the fluid dynamics of the chocolate fountain. Molten chocolate is a mildly shear-thinning non-Newtonian fluid. Dividing the flow into three main domains—the pumped flow up the centre, the film flow over each dome, and the freely falling curtain flow between the domes—we generate a wide-ranging study of Newtonian and non-Newtonian fluid mechanics. The central pumped flow is a benchmark to elucidate the effects of shear-thinning. The dome flow can be modelled as a thin-film flow with the leading-order effects being a simple balance of gravity and viscosity. Finally, the curtain flow is analytically intractable but is related to the existing theory of water bells (both inviscid and viscous). In pipe flow, Newtonian fluids exhibit a parabolic velocity profile; shear-thinning makes the profile more blunted. In thin-film flow over the dome, gravitational and viscous effects balance and the dome shape is not important beyond the local slope. We find that the chocolate thins and slows down as it travels down the dome. Finally, in the curtain flow, we predict the shape of the falling sheet for an inviscid fluid, and compare this with the literature to predict the shape for a viscous fluid, having shown that viscous forces are too great to ignore. We also find that the primary effect driving the shape of the curtain (which falls inwards towards the axis of the fountain) is surface tension. We find that the three domains provide excellent introductions to non-Newtonian mechanics, the important mathematical technique of scaling, and how to manipulate existing data to make our own predictions. We also find that the topic generates interest among the public in our engagement work.

  11. Cryogenic Fluid Management Technologies for Advanced Green Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Motil, Susan M.; Meyer, Michael L.; Tucker, Stephen P.

    2007-01-01

    In support of the Exploration Vision for returning to the Moon and beyond, NASA and its partners are developing and testing critical cryogenic fluid propellant technologies that will meet the need for high performance propellants on long-term missions. Reliable knowledge of low-gravity cryogenic fluid management behavior is lacking and yet is critical in the areas of tank thermal and pressure control, fluid acquisition, mass gauging, and fluid transfer. Such knowledge can significantly reduce or even eliminate tank fluid boil-off losses for long term missions, reduce propellant launch mass and required on-orbit margins, and simplify vehicle operations. The Propulsion and Cryogenic Advanced Development (PCAD) Project is performing experimental and analytical evaluation of several areas within Cryogenic Fluid Management (CFM) to enable NASA's Exploration Vision. This paper discusses the status of the PCAD CFM technology focus areas relative to the anticipated CFM requirements to enable execution of the Vision for Space Exploration.

  12. Dynamically-Tunable Smart Composites Featuring Electro-Rheological Fluids

    NASA Astrophysics Data System (ADS)

    Gandhi, Mukesh V.; Thompson, Brian S.

    1990-02-01

    A new generation of revolutionary multi-functional, dynamically-tunable, intelligent, ultra-advanced composite materials featuring electro-rheological fluids is proposed herein for the active continuum vibrational-control of structural systems. This paper reports on pioneering proof-of-concept experimental investigations focused on evaluating the elastodynamic transient and also the forced response characteristics of beams fabricated in this new class of materials. The results of these investigations clearly demonstrate the ability to dramatically change the vibrational characteristics of beam-like specimens fabricated in ultra-advanced composite materials by changing the electrical field imposed on the fluid domains. In addition, experimental results are presented which characterize the elastodynamic response of a connecting rod of a slider-crank mechanism fabricated in these ultra-advanced composite materials. Again, the combined forced and parametric responses are controlled by the voltage imposed on the electro-rheological fluid domain in the structure. The capability of these materials to interface with modern solid-state electronics can be exploited by extending the fundamental phenomenological work presented herein through the successful incorporation of intelligent sensor technologies and modern control strategies in order to significantly accelerate the evolution of these novel composite materials for the military and aerospace industries.

  13. Dynamics of fluid mixing in separated flows

    NASA Astrophysics Data System (ADS)

    Leder, A.

    1991-05-01

    Separated flows at high Re (>103) are highly turbulent. In some situations the turbulence generation and mixing processes associated with flow separation are desirable, e.g., in heat exchangers or in many chemical engineering applications. In others, e.g., stalled airfoils, separation must be avoided as it causes loss in pressure and kinetic energy. To control the phenomenon effectively, physical mechanisms of flow separation and related aspects, such as the growth of flow instabilities in shear layers, the process of vortex formation, and the dynamics of fluid mixing in recirculating flow regions, must be understood. In many cases numerical procedures, e.g., Navier-Stokes calculations including k-ɛ turbulence modeling, fail to predict real physical mechanisms in separated flows.1,2 Separated flows in the lee of bluff bodies have been studied for many years.3,4 However, accurate measurements of the magnitude and direction of velocities and the magnitude of the terms of the Reynolds stress tensor have been restricted by the unsuitability of the hot-wire anemometer in recirculating flows. The development of the pulsed-wire anemometer, flying hot-wire anemometer, and laser-Doppler anemometry (LDA) allows more reliable measurements also in turbulent separated flows.5-8 The aim of this paper is to investigate the dynamics of undisturbed fluid mixing in separated regions of 2-D, incompressible flows with visualization techniques and LDA. Measurements were performed with a vertical flat plate model, mounted in a closed-circuit wind tunnel at low blockage ratio. Because of the noninvasive character, optical techniques like LDA are more suitable to analyze complex fluid motions than pulsed-wire and flying-wire anemometry. The LDA system used to investigate turbulent flow structures consists of a two-channel version operating in backscatter mode and a specifically developed phase detector to extract phase-averaged information from recorded measurement ensembles.9 Endplates

  14. Computational Fluid Dynamics - Applications in Manufacturing Processes

    NASA Astrophysics Data System (ADS)

    Beninati, Maria Laura; Kathol, Austin; Ziemian, Constance

    2012-11-01

    A new Computational Fluid Dynamics (CFD) exercise has been developed for the undergraduate introductory fluid mechanics course at Bucknell University. The goal is to develop a computational exercise that students complete which links the manufacturing processes course and the concurrent fluid mechanics course in a way that reinforces the concepts in both. In general, CFD is used as a tool to increase student understanding of the fundamentals in a virtual world. A ``learning factory,'' which is currently in development at Bucknell seeks to use the laboratory as a means to link courses that previously seemed to have little correlation at first glance. A large part of the manufacturing processes course is a project using an injection molding machine. The flow of pressurized molten polyurethane into the mold cavity can also be an example of fluid motion (a jet of liquid hitting a plate) that is applied in manufacturing. The students will run a CFD process that captures this flow using their virtual mold created with a graphics package, such as SolidWorks. The laboratory structure is currently being implemented and analyzed as a part of the ``learning factory''. Lastly, a survey taken before and after the CFD exercise demonstrate a better understanding of both the CFD and manufacturing process.

  15. 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.

  16. Structure and dynamics of electrorheological fluids

    SciTech Connect

    Martin, J.E.; Odinek, J.; Halsey, T.C.; Kamien, R.

    1998-01-01

    We have used two-dimensional light scattering to study the structure and dynamics of a single-scattering electrorheological fluid in the quiescent state and in steady and oscillatory shear. Studies of the quiescent fluid show that particle columns grow in two stages. Particles first chain along the electric field, causing scattering lobes to appear orthogonal to the field, and then aggregate into columns, causing the scattering lobes to move to smaller angles. Column formation can be understood in terms of a thermal coarsening model we present, whereas the early-time scattering in the direction parallel to the field can be compared to the theory of line liquids. In simple shear the scattering lobes are inclined in the direction of fluid vorticity, in detailed agreement with the independent droplet model of the shear thinning viscosity. In oscillatory shear the orientation of the scattering lobes varies nonsinusoidally. This nonlinear dynamics is described by a kinetic chain model, which provides a theory of the nonlinear shear rheology in arbitrary shear flows. {copyright} {ital 1998} {ital The American Physical Society}

  17. Fluid dynamics of the cerebral aqueduct.

    PubMed

    Jacobson, E E; Fletcher, D F; Morgan, M K; Johnston, I H

    1996-01-01

    Despite a multitude of theories describing the mechanics of the intracranial spaces in diseases such as hydrocephalus, little is known about the mechanics of normal CSF flow. A pressure difference is required to drive CSF flow. Knowing that the pressure difference driving fluid through the aqueduct is beyond the resolution of clinically used pressure transducers, a computational fluid dynamics program was used to analyze flow through an aqueduct shape. Flow through this duct was compared with that through a cylinder and through a double hourglass. Both steady and oscillating flows were tested, revealing that only 1.1 Pa of pressure is required to move CSF through the aqueduct. This suggests that normally less than 5% of the total resistance to CSF flow within the CSF pathways occurs in the aqueduct.

  18. Fluid dynamical description of relativistic nuclear collisions

    NASA Technical Reports Server (NTRS)

    Nix, J. R.; Strottman, D.

    1982-01-01

    On the basis of both a conventional relativistic nuclear fluid dynamic model and a two fluid generalization that takes into account the interpenetration of the target and projectile upon contact, collisions between heavy nuclei moving at relativistic speeds are calculated. This is done by solving the relevant equations of motion numerically in three spatial dimensions by use of particle in cell finite difference computing techniques. The effect of incorporating a density isomer, or quasistable state, in the nuclear equation of state at three times normal nuclear density, and the effect of doubling the nuclear compressibility coefficient are studied. For the reaction 20Ne + 238U at a laboratory bombarding energy per nucleon of 393 MeV, the calculated distributions in energy and angle of outgoing charged particles are compared with recent experimental data both integrated over all impact parameters and for nearly central collisions.

  19. Advances in the microrheology of complex fluids.

    PubMed

    Waigh, Thomas Andrew

    2016-07-01

    New developments in the microrheology of complex fluids are considered. Firstly the requirements for a simple modern particle tracking microrheology experiment are introduced, the error analysis methods associated with it and the mathematical techniques required to calculate the linear viscoelasticity. Progress in microrheology instrumentation is then described with respect to detectors, light sources, colloidal probes, magnetic tweezers, optical tweezers, diffusing wave spectroscopy, optical coherence tomography, fluorescence correlation spectroscopy, elastic- and quasi-elastic scattering techniques, 3D tracking, single molecule methods, modern microscopy methods and microfluidics. New theoretical techniques are also reviewed such as Bayesian analysis, oversampling, inversion techniques, alternative statistical tools for tracks (angular correlations, first passage probabilities, the kurtosis, motor protein step segmentation etc), issues in micro/macro rheological agreement and two particle methodologies. Applications where microrheology has begun to make some impact are also considered including semi-flexible polymers, gels, microorganism biofilms, intracellular methods, high frequency viscoelasticity, comb polymers, active motile fluids, blood clots, colloids, granular materials, polymers, liquid crystals and foods. Two large emergent areas of microrheology, non-linear microrheology and surface microrheology are also discussed. PMID:27245584

  20. Advances in the microrheology of complex fluids

    NASA Astrophysics Data System (ADS)

    Waigh, Thomas Andrew

    2016-07-01

    New developments in the microrheology of complex fluids are considered. Firstly the requirements for a simple modern particle tracking microrheology experiment are introduced, the error analysis methods associated with it and the mathematical techniques required to calculate the linear viscoelasticity. Progress in microrheology instrumentation is then described with respect to detectors, light sources, colloidal probes, magnetic tweezers, optical tweezers, diffusing wave spectroscopy, optical coherence tomography, fluorescence correlation spectroscopy, elastic- and quasi-elastic scattering techniques, 3D tracking, single molecule methods, modern microscopy methods and microfluidics. New theoretical techniques are also reviewed such as Bayesian analysis, oversampling, inversion techniques, alternative statistical tools for tracks (angular correlations, first passage probabilities, the kurtosis, motor protein step segmentation etc), issues in micro/macro rheological agreement and two particle methodologies. Applications where microrheology has begun to make some impact are also considered including semi-flexible polymers, gels, microorganism biofilms, intracellular methods, high frequency viscoelasticity, comb polymers, active motile fluids, blood clots, colloids, granular materials, polymers, liquid crystals and foods. Two large emergent areas of microrheology, non-linear microrheology and surface microrheology are also discussed.

  1. 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.

  2. Computational fluid dynamics applications at McDonnel Douglas

    NASA Astrophysics Data System (ADS)

    Hakkinen, R. J.

    1987-03-01

    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.

  3. Geophysical fluid dynamics: whence, whither and why?

    NASA Astrophysics Data System (ADS)

    Vallis, Geoffrey K.

    2016-08-01

    This article discusses the role of geophysical fluid dynamics (GFD) in understanding the natural environment, and in particular the dynamics of atmospheres and oceans on Earth and elsewhere. GFD, as usually understood, is a branch of the geosciences that deals with fluid dynamics and that, by tradition, seeks to extract the bare essence of a phenomenon, omitting detail where possible. The geosciences in general deal with complex interacting systems and in some ways resemble condensed matter physics or aspects of biology, where we seek explanations of phenomena at a higher level than simply directly calculating the interactions of all the constituent parts. That is, we try to develop theories or make simple models of the behaviour of the system as a whole. However, these days in many geophysical systems of interest, we can also obtain information for how the system behaves by almost direct numerical simulation from the governing equations. The numerical model itself then explicitly predicts the emergent phenomena-the Gulf Stream, for example-something that is still usually impossible in biology or condensed matter physics. Such simulations, as manifested, for example, in complicated general circulation models, have in some ways been extremely successful and one may reasonably now ask whether understanding a complex geophysical system is necessary for predicting it. In what follows we discuss such issues and the roles that GFD has played in the past and will play in the future.

  4. Geophysical fluid dynamics: whence, whither and why?

    PubMed Central

    2016-01-01

    This article discusses the role of geophysical fluid dynamics (GFD) in understanding the natural environment, and in particular the dynamics of atmospheres and oceans on Earth and elsewhere. GFD, as usually understood, is a branch of the geosciences that deals with fluid dynamics and that, by tradition, seeks to extract the bare essence of a phenomenon, omitting detail where possible. The geosciences in general deal with complex interacting systems and in some ways resemble condensed matter physics or aspects of biology, where we seek explanations of phenomena at a higher level than simply directly calculating the interactions of all the constituent parts. That is, we try to develop theories or make simple models of the behaviour of the system as a whole. However, these days in many geophysical systems of interest, we can also obtain information for how the system behaves by almost direct numerical simulation from the governing equations. The numerical model itself then explicitly predicts the emergent phenomena—the Gulf Stream, for example—something that is still usually impossible in biology or condensed matter physics. Such simulations, as manifested, for example, in complicated general circulation models, have in some ways been extremely successful and one may reasonably now ask whether understanding a complex geophysical system is necessary for predicting it. In what follows we discuss such issues and the roles that GFD has played in the past and will play in the future.

  5. Geophysical fluid dynamics: whence, whither and why?

    PubMed Central

    2016-01-01

    This article discusses the role of geophysical fluid dynamics (GFD) in understanding the natural environment, and in particular the dynamics of atmospheres and oceans on Earth and elsewhere. GFD, as usually understood, is a branch of the geosciences that deals with fluid dynamics and that, by tradition, seeks to extract the bare essence of a phenomenon, omitting detail where possible. The geosciences in general deal with complex interacting systems and in some ways resemble condensed matter physics or aspects of biology, where we seek explanations of phenomena at a higher level than simply directly calculating the interactions of all the constituent parts. That is, we try to develop theories or make simple models of the behaviour of the system as a whole. However, these days in many geophysical systems of interest, we can also obtain information for how the system behaves by almost direct numerical simulation from the governing equations. The numerical model itself then explicitly predicts the emergent phenomena—the Gulf Stream, for example—something that is still usually impossible in biology or condensed matter physics. Such simulations, as manifested, for example, in complicated general circulation models, have in some ways been extremely successful and one may reasonably now ask whether understanding a complex geophysical system is necessary for predicting it. In what follows we discuss such issues and the roles that GFD has played in the past and will play in the future. PMID:27616918

  6. Fluid flow dynamics under location uncertainty

    NASA Astrophysics Data System (ADS)

    Mémin, Etienne

    2014-03-01

    We present a derivation of a stochastic model of Navier Stokes equations that relies on a decomposition of the velocity fields into a differentiable drift component and a time uncorrelated uncertainty random term. This type of decomposition is reminiscent in spirit to the classical Reynolds decomposition. However, the random velocity fluctuations considered here are not differentiable with respect to time, and they must be handled through stochastic calculus. The dynamics associated with the differentiable drift component is derived from a stochastic version of the Reynolds transport theorem. It includes in its general form an uncertainty dependent "subgrid" bulk formula that cannot be immediately related to the usual Boussinesq eddy viscosity assumption constructed from thermal molecular agitation analogy. This formulation, emerging from uncertainties on the fluid parcels location, explains with another viewpoint some subgrid eddy diffusion models currently used in computational fluid dynamics or in geophysical sciences and paves the way for new large-scales flow modelling. We finally describe an applications of our formalism to the derivation of stochastic versions of the Shallow water equations or to the definition of reduced order dynamical systems.

  7. Direct modeling for computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Xu, Kun

    2015-06-01

    All fluid dynamic equations are valid under their modeling scales, such as the particle mean free path and mean collision time scale of the Boltzmann equation and the hydrodynamic scale of the Navier-Stokes (NS) equations. The current computational fluid dynamics (CFD) focuses on the numerical solution of partial differential equations (PDEs), and its aim is to get the accurate solution of these governing equations. Under such a CFD practice, it is hard to develop a unified scheme that covers flow physics from kinetic to hydrodynamic scales continuously because there is no such governing equation which could make a smooth transition from the Boltzmann to the NS modeling. The study of fluid dynamics needs to go beyond the traditional numerical partial differential equations. The emerging engineering applications, such as air-vehicle design for near-space flight and flow and heat transfer in micro-devices, do require further expansion of the concept of gas dynamics to a larger domain of physical reality, rather than the traditional distinguishable governing equations. At the current stage, the non-equilibrium flow physics has not yet been well explored or clearly understood due to the lack of appropriate tools. Unfortunately, under the current numerical PDE approach, it is hard to develop such a meaningful tool due to the absence of valid PDEs. In order to construct multiscale and multiphysics simulation methods similar to the modeling process of constructing the Boltzmann or the NS governing equations, the development of a numerical algorithm should be based on the first principle of physical modeling. In this paper, instead of following the traditional numerical PDE path, we introduce direct modeling as a principle for CFD algorithm development. Since all computations are conducted in a discretized space with limited cell resolution, the flow physics to be modeled has to be done in the mesh size and time step scales. Here, the CFD is more or less a direct

  8. Domain decomposition algorithms and computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Chan, Tony F.

    1988-01-01

    Some of the new domain decomposition algorithms are applied to two model problems in computational fluid dynamics: the two-dimensional convection-diffusion problem and the incompressible driven cavity flow problem. First, a brief introduction to the various approaches of domain decomposition is given, and a survey of domain decomposition preconditioners for the operator on the interface separating the subdomains is then presented. For the convection-diffusion problem, 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 examined.

  9. Kinematics and Fluid Dynamics of Jellyfish Maneuvering

    NASA Astrophysics Data System (ADS)

    Miller, Laura; Hoover, Alex

    2014-11-01

    Jellyfish propel themselves through the water through periodic contractions of their elastic bells. Some jellyfish, such as the moon jellyfish Aurelia aurita and the upside down jellyfish Cassiopea xamachana, can perform turns via asymmetric contractions of the bell. The fluid dynamics of jellyfish forward propulsion and turning is explored here by analyzing the contraction kinematics of several species and using flow visualization to quantify the resulting flow fields. The asymmetric contraction and structure of the jellyfish generates asymmetries in the starting and stopping vortices. This creates a diagonal jet and a net torque acting on the jellyfish. Results are compared to immersed boundary simulations

  10. Three-Dimensional Computational Fluid Dynamics

    SciTech Connect

    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.

  11. Supercomputer applications in computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Holst, Terry L.

    1989-01-01

    The field of computational fluid dynamics (CFD) using large-scale supercomputer applications is discussed. Formulational and computational requirements for the various governing equations, including the Euler and Navier-tokes approaches, are examined for typical problems including the viscous flow field solution about a complete aerospace vehicle. Recent computed results and experimental comparisons are given to highlight the presentation. The future of CFD associated with three-dimensional applications is found to be rapidly expanding across a broad front, including internal and external flows and flows across the entire speed regime.

  12. The Fluid Dynamics Demo Kit: Part II

    NASA Astrophysics Data System (ADS)

    Underhill, Patrick; Fix, Hannah; Haines, Timothy; Prestridge, Kathy; Flack, Karen

    2012-11-01

    This talk will focus on the current contents and efforts building a fluid dynamics demonstration/experiment kit through the APS-DFD Mentoring and Outreach Committee and with funding from the APS DFD. The current experiments include predicting how far the water from a water gun will go, predicting how long a Heron's fountain will run, measuring the viscosity of corn syrup by measuring terminal velocity, and measuring the flow rate through a siphon. We will discuss the testing and development of these experiments and the results of field testing. Ideas for future experiments will also be discussed.

  13. Computational fluid dynamics using CATIA created geometry

    NASA Astrophysics Data System (ADS)

    Gengler, Jeanne E.

    1989-07-01

    A method has been developed to link the geometry definition residing on a CAD/CAM system with a computational fluid dynamics (CFD) tool needed to evaluate aerodynamic designs and requiring the memory capacity of a supercomputer. Requirements for surfaces suitable for CFD analysis are discussed. Techniques for developing surfaces and verifying their smoothness are compared, showing the capability of the CAD/CAM system. The utilization of a CAD/CAM system to create a computational mesh is explained, and the mesh interaction with the geometry and input file preparation for the CFD analysis is discussed.

  14. Expanding Participation in Fluid Dynamics Research

    NASA Astrophysics Data System (ADS)

    Tagg, Randall

    2015-11-01

    Two legacies provided by great scientists are scientific discoveries and more scientists. Is there a way that these impacts can be magnified? Examples using the Taylor-Couette experiment and other fluid dynamics problems will demonstrate that indeed more people can fruitfully engage in open and even bold investigation. Participants include high school students, teachers, undergraduates, artists, business developers and interested laypersons. With imagination, good training, and a suitable lab space, a special tribute can be given to those who mentor us by scaling up the breadth of their influence.

  15. Distributed visualization for computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Sosoka, Don J.; Facca, Anthony A.

    1992-01-01

    Distributed concurrent visualization and computation in computational fluid dynamics (CFD) is not a new concept. Specialized applications such as Realtime Interactive Particle-tracer (RIP) and vendor specific tools like Distributed Graphics Language (DGL) have been in use for some time. This paper describes a current project underway at NASA Lewis Research Center to provide the CFD researcher with an easy method for incorporating distributed processing concepts into program development. Details on the FORTRAN capable interface to a set of network and visualization functions are presented along with some results from initial CFD case studies that employ these techniques.

  16. Distributed visualization for computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Sosoka, Don J.; Facca, Anthony A.

    1992-02-01

    Distributed concurrent visualization and computation in computational fluid dynamics (CFD) is not a new concept. Specialized applications such as Realtime Interactive Particle-tracer (RIP) and vendor specific tools like Distributed Graphics Language (DGL) have been in use for some time. This paper describes a current project underway at NASA Lewis Research Center to provide the CFD researcher with an easy method for incorporating distributed processing concepts into program development. Details on the FORTRAN capable interface to a set of network and visualization functions are presented along with some results from initial CFD case studies that employ these techniques.

  17. Nuclear Energy -- Knowledge Base for Advanced Modeling and Simulation (NE-KAMS) Code Verification and Validation Data Standards and Requirements: Fluid Dynamics Version 1.0

    SciTech Connect

    Greg Weirs; Hyung Lee

    2011-09-01

    V&V and UQ are the primary means to assess the accuracy and reliability of M&S and, hence, to establish confidence in M&S. Though other industries are establishing standards and requirements for the performance of V&V and UQ, at present, the nuclear industry has not established such standards or requirements. However, the nuclear industry is beginning to recognize that such standards are needed and that the resources needed to support V&V and UQ will be very significant. In fact, no single organization has sufficient resources or expertise required to organize, conduct and maintain a comprehensive V&V and UQ program. What is needed is a systematic and standardized approach to establish and provide V&V and UQ resources at a national or even international level, with a consortium of partners from government, academia and industry. Specifically, what is needed is a structured and cost-effective knowledge base that collects, evaluates and stores verification and validation data, and shows how it can be used to perform V&V and UQ, leveraging collaboration and sharing of resources to support existing engineering and licensing procedures as well as science-based V&V and UQ processes. The Nuclear Energy Knowledge base for Advanced Modeling and Simulation (NE-KAMS) is being developed at the Idaho National Laboratory in conjunction with Bettis Laboratory, Sandia National Laboratories, Argonne National Laboratory, Utah State University and others with the objective of establishing a comprehensive and web-accessible knowledge base to provide V&V and UQ resources for M&S for nuclear reactor design, analysis and licensing. The knowledge base will serve as an important resource for technical exchange and collaboration that will enable credible and reliable computational models and simulations for application to nuclear power. NE-KAMS will serve as a valuable resource for the nuclear industry, academia, the national laboratories, the U.S. Nuclear Regulatory Commission (NRC) and

  18. Overview af MSFC's Applied Fluid Dynamics Analysis Group Activities

    NASA Technical Reports Server (NTRS)

    Garcia, Roberto; Griffin, Lisa; Williams, Robert

    2004-01-01

    This paper presents viewgraphs on NASA Marshall Space Flight Center's Applied Fluid Dynamics Analysis Group Activities. The topics include: 1) Status of programs at MSFC; 2) Fluid Mechanics at MSFC; 3) Relevant Fluid Dynamics Activities at MSFC; and 4) Shuttle Return to Flight.

  19. Fluid dynamic effects on precision cleaning with supercritical fluids

    SciTech Connect

    Phelps, M.R.; Hogan, M.O.; Silva, L.J.

    1994-06-01

    Pacific Northwest Laboratory staff have assembled a small supercritical fluids parts cleaning test stand to characterize how system dynamics affect the efficacy of precision cleaning with supercritical carbon dioxide. A soiled stainless steel coupon, loaded into a ``Berty`` autoclave, was used to investigate how changes in system turbulence and solvent temperature influenced the removal of test dopants. A pulsed laser beam through a fiber optic was used to investigate real-time contaminant removal. Test data show that cleaning efficiency is a function of system agitation, solvent density, and temperature. These data also show that high levels of cleaning efficiency can generally be achieved with high levels of system agitation at relatively low solvent densities and temperatures. Agitation levels, temperatures, and densities needed for optimal cleaning are largely contaminant dependent. Using proper system conditions, the levels of cleanliness achieved with supercritical carbon dioxide compare favorably with conventional precision cleaning methods. Additional research is currently being conducted to generalize the relationship between cleaning performance and parameters such as contaminant solubilities, mass transfer rates, and solvent agitation. These correlations can be used to optimize cleaning performance, system design, and time and energy consumption for particular parts cleaning applications.

  20. Integration of physiology and fluid dynamics.

    PubMed

    Schmalzriedt, Sven; Jenne, Marc; Mauch, Klaus; Reuss, Matthias

    2003-01-01

    The purpose of strategies for the integration of fluid dynamics and physiology is the development of more reliable simulation tools to accelerate the process of scale-up. The rigorous mathematical modeling of the richly interactive relationship between the dynamic response of biosystems and the physical environment changing in time and space must rest on the link between coupled momentum, energy and mass balances and structured modeling of the biophase. With the exponential increase in massive computer capabilities hard- and software tools became available for simulation strategies based on such holistic integration approaches. The review discusses fundamental aspects of application of computational fluid dynamics (CFD) to three-dimensional two-phase turbulence flow in stirred tank bioreactors. Examples of coupling momentum and material balance equations with simple unstructured kinetic models for the behavior of the biophase are used to illustrate the application of these strategies to the selection of suitable impeller configurations. The examples reviewed in this paper include distribution of carbon and energy source in fed batch cultures as well as dissolved oxygen fields during aerobic fermentations. A more precise forecasting of the impact of the multitude of interactions must, however, rest upon a rigorous understanding of the response of the cell factory to the complex dynamic stimulation due to space- and time-dependent concentration fields. The paper also introduces some ideas for fast and very fast experimental observations of intracellular pool concentrations based on stimulus response methods. These observations finally lead to a more complex integration approach based on the coupling of CFD and structured metabolic models.

  1. The Future with Cryogenic Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Scurlock, R. G.

    The applications of cryogenic systems have expanded over the past 50 years into many areas of our lives. During this time, the impact of the common features of Cryogenic Fluid Dynamics, CryoFD, on the economic design of these cryogenic systems, has grown out of a long series of experimental studies carried out by teams of postgraduate students at Southampton University.These studies have sought to understand the heat transfer and convective behavior of cryogenic liquids and vapors, but they have only skimmed over the many findings made, on the strong convective motions of fluids at low temperatures. The convection takes place in temperature gradients up to 10,000 K per meter, and density gradients of 1000% per meter and more, with rapid temperature and spatially dependent changes in physical properties like viscosity and surface tension, making software development and empirical correlations almost impossible to achieve. These temperature and density gradients are far larger than those met in other convecting systems at ambient temperatures, and there is little similarity. The paper will discuss the likely impact of CryoFD on future cryogenic systems, and hopefully inspire further research to support and expand the use of existing findings, and to improve the economy of present-day systems even more effectively. Particular examples to be mentioned include the following. Doubling the cooling power of cryo-coolers by a simple use of CryoFD. Reducing the boil-off rate of liquid helium stored at the South Pole, such that liquid helium availability is now all-the-year-round. Helping to develop the 15 kA current leads for the LHC superconducting magnets at CERN, with much reduced refrigeration loads. Improving the heat transfer capability of boiling heat transfer surfaces by 10 to 100 fold. This paper is an edited text of an invited plenary presentation at ICEC25/ICMC2014 by Professor Scurlock on the occasion of his being presented with the ICEC Mendelssohn Award for his

  2. Modeling quantum fluid dynamics at nonzero temperatures

    PubMed Central

    Berloff, Natalia G.; Brachet, Marc; Proukakis, Nick P.

    2014-01-01

    The detailed understanding of the intricate dynamics of quantum fluids, in particular in the rapidly growing subfield of quantum turbulence which elucidates the evolution of a vortex tangle in a superfluid, requires an in-depth understanding of the role of finite temperature in such systems. The Landau two-fluid model is the most successful hydrodynamical theory of superfluid helium, but by the nature of the scale separations it cannot give an adequate description of the processes involving vortex dynamics and interactions. In our contribution we introduce a framework based on a nonlinear classical-field equation that is mathematically identical to the Landau model and provides a mechanism for severing and coalescence of vortex lines, so that the questions related to the behavior of quantized vortices can be addressed self-consistently. The correct equation of state as well as nonlocality of interactions that leads to the existence of the roton minimum can also be introduced in such description. We review and apply the ideas developed for finite-temperature description of weakly interacting Bose gases as possible extensions and numerical refinements of the proposed method. We apply this method to elucidate the behavior of the vortices during expansion and contraction following the change in applied pressure. We show that at low temperatures, during the contraction of the vortex core as the negative pressure grows back to positive values, the vortex line density grows through a mechanism of vortex multiplication. This mechanism is suppressed at high temperatures. PMID:24704874

  3. Spectral Methods for Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Zang, T. A.; Streett, C. L.; Hussaini, M. Y.

    1994-01-01

    As a tool for large-scale computations in fluid dynamics, spectral methods were prophesized in 1944, born in 1954, virtually buried in the mid-1960's, resurrected in 1969, evangalized in the 1970's, and catholicized in the 1980's. The use of spectral methods for meteorological problems was proposed by Blinova in 1944 and the first numerical computations were conducted by Silberman (1954). By the early 1960's computers had achieved sufficient power to permit calculations with hundreds of degrees of freedom. For problems of this size the traditional way of computing the nonlinear terms in spectral methods was expensive compared with finite-difference methods. Consequently, spectral methods fell out of favor. The expense of computing nonlinear terms remained a severe drawback until Orszag (1969) and Eliasen, Machenauer, and Rasmussen (1970) developed the transform methods that still form the backbone of many large-scale spectral computations. The original proselytes of spectral methods were meteorologists involved in global weather modeling and fluid dynamicists investigating isotropic turbulence. The converts who were inspired by the successes of these pioneers remained, for the most part, confined to these and closely related fields throughout the 1970's. During that decade spectral methods appeared to be well-suited only for problems governed by ordinary diSerential eqllations or by partial differential equations with periodic boundary conditions. And, of course, the solution itself needed to be smooth. Some of the obstacles to wider application of spectral methods were: (1) poor resolution of discontinuous solutions; (2) inefficient implementation of implicit methods; and (3) drastic geometric constraints. All of these barriers have undergone some erosion during the 1980's, particularly the latter two. As a result, the applicability and appeal of spectral methods for computational fluid dynamics has broadened considerably. The motivation for the use of spectral

  4. Active Polar Two-Fluid Macroscopic Dynamics

    NASA Astrophysics Data System (ADS)

    Pleiner, Harald; Svensek, Daniel; Brand, Helmut R.

    2014-03-01

    We study the dynamics of systems with a polar dynamic preferred direction. Examples include the pattern-forming growth of bacteria (in a solvent, shoals of fish (moving in water currents), flocks of birds and migrating insects (flying in windy air). Because the preferred direction only exists dynamically, but not statically, the macroscopic variable of choice is the macroscopic velocity associated with the motion of the active units. We derive the macroscopic equations for such a system and discuss novel static, reversible and irreversible cross-couplings connected to this second velocity. We find a normal mode structure quite different compared to the static descriptions, as well as linear couplings between (active) flow and e.g. densities and concentrations due to the genuine two-fluid transport derivatives. On the other hand, we get, quite similar to the static case, a direct linear relation between the stress tensor and the structure tensor. This prominent ``active'' term is responsible for many active effects, meaning that our approach can describe those effects as well. In addition, we also deal with explicitly chiral systems, which are important for many active systems. In particular, we find an active flow-induced heat current specific for the dynamic chiral polar order.

  5. Recent advances in protein profiling of tissues and tissue fluids.

    PubMed

    Yang, Shi; Huang, Chun-Ming

    2007-08-01

    Creating protein profiles of tissues and tissue fluids, which contain secreted proteins and peptides released from various cells, is critical for biomarker discovery as well as drug and vaccine target selection. It is extremely difficult to obtain pure samples from tissues or tissue fluids, however, and identification of complex protein mixtures is still a challenge for mass spectrometry analysis. Here, we summarize recent advances in techniques for extracting proteins from tissues for mass spectrometry profiling and imaging. We also introduce a novel technique using a capillary ultrafiltration (CUF) probe to enable in vivo collection of proteins from the tissue microenvironment. The CUF probe technique is compared with existing sampling techniques, including perfusion, saline wash, fine-needle aspiration and microdialysis. In this review, we also highlight quantitative mass spectrometric proteomic approaches with, and without, stable-isotope labels. Advances in quantitative proteomics will significantly improve protein profiling of tissue and tissue fluid samples collected by CUF probes.

  6. AFDM: An Advanced Fluid-Dynamics Model

    SciTech Connect

    Parker, F.R.

    1990-09-01

    The T6P postprocessor analyzes data from TAPE6 and TAPE36. The processor calculates new variables, integrates variables over regions of the mesh, compares values of a variable of a given problem at selected times, compares values of a variable at selected times between problems for parameter studies, calculates derivatives of a variable with respect to time or another variable, and traces a variable at a requested location in the mesh over time. The data are presented to the user graphically, using two-dimesnional graphs and three-dimensional perspective or contour plots. Interactive graphic techniques may be used with perspective plots.

  7. Advances in modelling of biomimetic fluid flow at different scales

    PubMed Central

    2011-01-01

    The biomimetic flow at different scales has been discussed at length. The need of looking into the biological surfaces and morphologies and both geometrical and physical similarities to imitate the technological products and processes has been emphasized. The complex fluid flow and heat transfer problems, the fluid-interface and the physics involved at multiscale and macro-, meso-, micro- and nano-scales have been discussed. The flow and heat transfer simulation is done by various CFD solvers including Navier-Stokes and energy equations, lattice Boltzmann method and molecular dynamics method. Combined continuum-molecular dynamics method is also reviewed. PMID:21711847

  8. Current Results and Proposed Activities in Microgravity Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Polezhaev, V. I.

    1996-01-01

    The Institute for Problems in Mechanics' Laboratory work in mathematical and physical modelling of fluid mechanics develops models, methods, and software for analysis of fluid flow, instability analysis, direct numerical modelling and semi-empirical models of turbulence, as well as experimental research and verification of these models and their applications in technological fluid dynamics, microgravity fluid mechanics, geophysics, and a number of engineering problems. This paper presents an overview of the results in microgravity fluid dynamics research during the last two years. Nonlinear problems of weakly compressible and compressible fluid flows are discussed.

  9. Cardiac fluid dynamics anticipates heart adaptation.

    PubMed

    Pedrizzetti, Gianni; Martiniello, Alfonso R; Bianchi, Valter; D'Onofrio, Antonio; Caso, Pio; Tonti, Giovanni

    2015-01-21

    Hemodynamic forces represent an epigenetic factor during heart development and are supposed to influence the pathology of the grown heart. Cardiac blood motion is characterized by a vortical dynamics, and it is common belief that the cardiac vortex has a role in disease progressions or regression. Here we provide a preliminary demonstration about the relevance of maladaptive intra-cardiac vortex dynamics in the geometrical adaptation of the dysfunctional heart. We employed an in vivo model of patients who present a stable normal heart function in virtue of the cardiac resynchronization therapy (CRT, bi-ventricular pace-maker) and who are expected to develop left ventricle remodeling if pace-maker was switched off. Intra-ventricular fluid dynamics is analyzed by echocardiography (Echo-PIV). Under normal conditions, the flow presents a longitudinal alignment of the intraventricular hemodynamic forces. When pacing is temporarily switched off, flow forces develop a misalignment hammering onto lateral walls, despite no other electro-mechanical change is noticed. Hemodynamic forces result to be the first event that evokes a physiological activity anticipating cardiac changes and could help in the prediction of longer term heart adaptations.

  10. Fluid flow dynamics in MAS systems.

    PubMed

    Wilhelm, Dirk; Purea, Armin; Engelke, Frank

    2015-08-01

    The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor. PMID:26073599

  11. [The dynamics of the amniotic fluid].

    PubMed

    Minh, H N; Douvin, D; Smadja, A; Orcel, L

    1978-01-01

    Morphological study of the ovular membranes showing that under the amnion, until term, there persists perfectly live and active chorial cytotrophoblast covered by a well vascularised and developed parietal decidua. Under the electron microscopy, the apical pole of the amniotic cells as well as their intercellular space are bordered by microvilli. Their basal pole has squat pedicels. The chorion which supports the amnion is avascular. The surface of the cytotrophoblast opposite the chorio-amnion is raised by numerous protuberances in the form of pedicels. The trophoblast is also furrowed by intercellular canals bordered by microvilli and reinforced by desmosomes. Two cellular appearances may be distinguished in the trophoblast: elements similar to the syncytial type with the characteristics of steroid cells and elements of a Langhans type which may play a role in protein synthesis. The decidual cells, in a quinconcial perivascular arrangement, are rich in pinocytotic vesicles. Thus whilst it is undeniable that the foetus plays a certain role in the dynamics of the amniotic fluid by swallowing and urinary excretion, these phenomena are minimal in relation to exchanges through the ovular membranes. Transamniotic passage is the first stage in movement of the fluid. The chorion, by virtue of its plexiform, areolar structure forms the next stop. From the chorion, the circulation continues through the intercellular canals of the trophoblast and the amniotic fluid is thus brought into the well vascularised parietal decidua. In addition to this extracellular circulation, the authors fell that there exists an intracellular passage by uptake and secretion, as evidenced by the high degree of pinocytosis within the cells.

  12. 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.

  13. Domain decomposition methods in computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Gropp, William D.; Keyes, David E.

    1992-01-01

    The divide-and-conquer paradigm of iterative domain decomposition, or substructuring, has become a practical tool in computational fluid dynamic applications because of its flexibility in accommodating adaptive refinement through locally uniform (or quasi-uniform) grids, its ability to exploit multiple discretizations of the operator equations, and the modular pathway it provides towards parallelism. These features are illustrated on the classic model problem of flow over a backstep using Newton's method as the nonlinear iteration. Multiple discretizations (second-order in the operator and first-order in the preconditioner) and locally uniform mesh refinement pay dividends separately, and they can be combined synergistically. Sample performance results are included from an Intel iPSC/860 hypercube implementation.

  14. Shuttle rocket booster computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Chung, T. J.; Park, O. Y.

    1988-01-01

    Additional results and a revised and improved computer program listing from the shuttle rocket booster computational fluid dynamics formulations are presented. Numerical calculations for the flame zone of solid propellants are carried out using the Galerkin finite elements, with perturbations expanded to the zeroth, first, and second orders. The results indicate that amplification of oscillatory motions does indeed prevail in high frequency regions. For the second order system, the trend is similar to the first order system for low frequencies, but instabilities may appear at frequencies lower than those of the first order system. The most significant effect of the second order system is that the admittance is extremely oscillatory between moderately high frequency ranges.

  15. 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.

  16. Graphics supercomputer for computational fluid dynamics research

    NASA Astrophysics Data System (ADS)

    Liaw, Goang S.

    1994-11-01

    The objective of this project is to purchase a state-of-the-art graphics supercomputer to improve the Computational Fluid Dynamics (CFD) research capability at Alabama A & M University (AAMU) and to support the Air Force research projects. A cutting-edge graphics supercomputer system, Onyx VTX, from Silicon Graphics Computer Systems (SGI), was purchased and installed. Other equipment including a desktop personal computer, PC-486 DX2 with a built-in 10-BaseT Ethernet card, a 10-BaseT hub, an Apple Laser Printer Select 360, and a notebook computer from Zenith were also purchased. A reading room has been converted to a research computer lab by adding some furniture and an air conditioning unit in order to provide an appropriate working environments for researchers and the purchase equipment. All the purchased equipment were successfully installed and are fully functional. Several research projects, including two existing Air Force projects, are being performed using these facilities.

  17. Artificial Intelligence In Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Vogel, Alison Andrews

    1991-01-01

    Paper compares four first-generation artificial-intelligence (Al) software systems for computational fluid dynamics. Includes: Expert Cooling Fan Design System (EXFAN), PAN AIR Knowledge System (PAKS), grid-adaptation program MITOSIS, and Expert Zonal Grid Generation (EZGrid). Focuses on knowledge-based ("expert") software systems. Analyzes intended tasks, kinds of knowledge possessed, magnitude of effort required to codify knowledge, how quickly constructed, performances, and return on investment. On basis of comparison, concludes Al most successful when applied to well-formulated problems solved by classifying or selecting preenumerated solutions. In contrast, application of Al to poorly understood or poorly formulated problems generally results in long development time and large investment of effort, with no guarantee of success.

  18. Collective dynamics of sperm in viscoelastic fluid

    NASA Astrophysics Data System (ADS)

    Tung, Chih-Kuan; Fiore, Alyssa G.; Ardon, Florencia; Suarez, Susan S.; Wu, Mingming

    2015-03-01

    Collective dynamics of artificial swimmers has gathered a lot of attention from physicists, in part because of its close relations to emergent behaviors in condensed matter, such as phase transitions. However, the emergence of order tends to be less drastic in the systems composed of real living cells, sometimes due to the natural variability in individual organisms. Here, using bull sperm as a model system, we demonstrate that the local orientation order of sperm spontaneously emerges in viscoelastic fluids, migrating collectively in clusters in high cell concentrations, or pairs in low cell concentrations. This collectiveness is similar to a liquid-gas phase transition, as both phases coexist simultaneously in our system. Unlike bacterial swarming, this collectiveness does not require the cells to be in a different phenotype than the regular swimming one, providing further simplicity to the physicists. We will discuss the underlying interaction mechanism, and the potential influence in biology. Supported by NIH Grant 1R01HD070038.

  19. Dynamics and Emergent Structures in Active Fluids

    NASA Astrophysics Data System (ADS)

    Baskaran, Aparna

    2014-03-01

    In this talk, we consider an active fluid of colloidal sized particles, with the primary manifestation of activity being a self-replenishing velocity along one body axis of the particle. This is a minimal model for varied systems such as bacterial colonies, cytoskeletal filament motility assays vibrated granular particles and self propelled diffusophoretic colloids, depending on the nature of interaction among the particles. Using microscopic Brownian dynamics simulations, coarse-graining using the tools of non-equilibrium statistical mechanics and analysis of macroscopic hydrodynamic theories, we characterize emergent structures seen in these systems, which are determined by the symmetry of the interactions among the active units, such as propagating density waves, dense stationary bands, asters and phase separated isotropic clusters. We identify a universal mechanism, termed ``self-regulation,'' as the underlying physics that leads to these structures in diverse systems. Support from NSF through DMR-1149266 and DMR-0820492.

  20. Domain decomposition methods in computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Gropp, William D.; Keyes, David E.

    1991-01-01

    The divide-and-conquer paradigm of iterative domain decomposition, or substructuring, has become a practical tool in computational fluid dynamic applications because of its flexibility in accommodating adaptive refinement through locally uniform (or quasi-uniform) grids, its ability to exploit multiple discretizations of the operator equations, and the modular pathway it provides towards parallelism. These features are illustrated on the classic model problem of flow over a backstep using Newton's method as the nonlinear iteration. Multiple discretizations (second-order in the operator and first-order in the preconditioner) and locally uniform mesh refinement pay dividends separately, and they can be combined synergistically. Sample performance results are included from an Intel iPSC/860 hypercube implementation.

  1. Study of ebullated bed fluid dynamics

    NASA Astrophysics Data System (ADS)

    Schaefer, R. J.; Rundell, D. N.; Shou, J. K.

    1983-07-01

    The fluid dynamics occurring in a coal liquefaction reactor is measured and compared with cold flow fluidization results. Catalyst bed expansions and gas holdups are higher in the Process Development Unit (PDU) than those observed in the cold flow tests for slurries having the same nominal viscosity. Comparison of PDU results with cold flow results shows that the bulk of the operating reactor gas flow lies in the ideal bubbly regime. Existence of churn turbulent behavior during these two experiments is consistent with trends observed in earlier cold flow experiments. Two and three phase fluidization experiments are carried out. Bed expansion is primarily a function of slurry velocity, with gas velocity having only a weak effect. A viscometer is adapted for measurement of the viscosity of coal slurries at high temperature and pressure. A significant degree of backmixing occurs in the H-Coal system.

  2. Visualization of unsteady computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Haimes, Robert

    1994-01-01

    A brief summary of the computer environment used for calculating three dimensional unsteady Computational Fluid Dynamic (CFD) results is presented. This environment requires a super computer as well as massively parallel processors (MPP's) and clusters of workstations acting as a single MPP (by concurrently working on the same task) provide the required computational bandwidth for CFD calculations of transient problems. The cluster of reduced instruction set computers (RISC) is a recent advent based on the low cost and high performance that workstation vendors provide. The cluster, with the proper software can act as a multiple instruction/multiple data (MIMD) machine. A new set of software tools is being designed specifically to address visualizing 3D unsteady CFD results in these environments. Three user's manuals for the parallel version of Visual3, pV3, revision 1.00 make up the bulk of this report.

  3. Deep Eutectic Salt Formulations Suitable as Advanced Heat Transfer Fluids

    SciTech Connect

    Raade, Justin; Roark, Thomas; Vaughn, John; Bradshaw, Robert

    2013-07-22

    Concentrating solar power (CSP) facilities are comprised of many miles of fluid-filled pipes arranged in large grids with reflective mirrors used to capture radiation from the sun. Solar radiation heats the fluid which is used to produce steam necessary to power large electricity generation turbines. Currently, organic, oil-based fluid in the pipes has a maximum temperature threshold of 400 °C, allowing for the production of electricity at approximately 15 cents per kilowatt hour. The DOE hopes to foster the development of an advanced heat transfer fluid that can operate within higher temperature ranges. The new heat transfer fluid, when used with other advanced technologies, could significantly decrease solar electricity cost. Lower costs would make solar thermal electricity competitive with gas and coal and would offer a clean, renewable source of energy. Molten salts exhibit many desirable heat transfer qualities within the range of the project objectives. Halotechnics developed advanced heat transfer fluids (HTFs) for application in solar thermal power generation. This project focused on complex mixtures of inorganic salts that exhibited a high thermal stability, a low melting point, and other favorable characteristics. A high-throughput combinatorial research and development program was conducted in order to achieve the project objective. Over 19,000 candidate formulations were screened. The workflow developed to screen various chemical systems to discover salt formulations led to mixtures suitable for use as HTFs in both parabolic trough and heliostat CSP plants. Furthermore, salt mixtures which will not interfere with fertilizer based nitrates were discovered. In addition for use in CSP, the discovered salt mixtures can be applied to electricity storage, heat treatment of alloys and other industrial processes.

  4. Geometry and dynamics of fluid-fluid interfaces

    NASA Astrophysics Data System (ADS)

    Thrasher, Matthew Evan

    We observed the evolution of unstable fluid interfaces in experiments on viscous fingering, pinch-off, and bouncing jets. If we can first identify classes of universal behavior, then we can begin building a unified framework to understand nonlinear processes. We performed the first experimental test of the harmonic moments of viscous fingering patterns, grown by injecting air into a thin layer of silicone oil, which was confined between two closely spaced plates, called a Hele-Shaw cell. We observed that the predicted decay of the moments was accurate within our measurement uncertainty, which confirmed the predicted conservation of the moments for zero surface tension. With greater forcing, the air bubble will undergo a secondary tip-splitting instability, where the fingers of air fork into two or more fingers. We discovered two selection rules for the changing base width and the nearly invariant opening angle of fjords, which are the regions of oil between the fingers of air. We then compared our experiments on viscous fingering with diffusion-limited aggregation (DLA), a model of unstable growth. We calculated that DLA and viscous fingering have the same spectrum of singularities [called f(alpha)] within measurement uncertainty. Since the spectrum is a global encapsulation of the growth dynamics and scaling properties, we say that the two processes are in the same scaling universality class. All of these results for viscous fingering are expected to apply to other physical systems which approximate Laplacian growth, a model of an interface where its growth rate is determined by the local gradient of a field φ obeying Laplace's equation ∇2 φ=0. Next we present preliminary work on the experimental test of two predictions for flows in Hele-Shaw cells: (1) soliton-like behavior of two viscous domains and (2) self-similar, universal pinch-off of an inviscid bubble in a viscous liquid. Finally, we report our observations and analysis of a liquid stream with

  5. Chain Dynamics in a Dilute Magnetorheological Fluid

    NASA Technical Reports Server (NTRS)

    Liu, Jing; Hagenbuchle, Martin

    1996-01-01

    The structure, formation, and dynamics of dilute, mono-dispersive ferrofluid emulsions in an external magnetic field have been investigated using dynamic light scattering techniques. In the absence of the magnetic field, the emulsion particles are randomly distributed and behave like hard spheres in Brownian motion. An applied magnetic field induces a magnetic dipole moment in each particle. Dipolar interactions between particles align them into chains where correlation functions show two decay processes. The short-time decay shows the motion of straight chains as a whole where the apparent chain length increases with the applied magnetic field and the particle volume fraction. Good scaling results are obtained showing that the apparent chain length grows with time following a power law with exponent of 0.6 and depends on the applied field, particle volume fraction, and diffusion constant of the particles. The long-time decay in the correlation function shows oscillation when the chains reach a certain length with time and stiffness with threshold field This result shows that chains not only fluctuate, but move in a periodic motion with a frequency of 364 Hz at lambda = 15. It may suggest the existence of phonons. This work is the first step in the understanding of the structure formation, especially chain coarsening mechanism, of magnetorheological (MR) fluids at higher volume fractions.

  6. Dynamic Hydraulic Fluid Stimulation Regulated Intramedullary Pressure

    PubMed Central

    Hu, Minyi; Serra-Hsu, Frederick; Bethel, Neville; Lin, Liangjun; Ferreri, Suzanne; Cheng, Jiqi; Qin, Yi-Xian

    2013-01-01

    Physical signals within bone, i.e. generated from mechanical loading, have the potential to initiate skeletal adaptation. Strong evidence has pointed to bone fluid flow (BFF) as a media between an external load and the bone cells, in which altered velocity and pressure can ultimately initiate the mechanotransduction and the remodeling process within bone. Load-induced BFF can be altered by factors such as intramedullary pressure (ImP) and/or bone matrix strain, mediating bone adaptation. Previous studies have shown that BFF induced by ImP alone, with minimum bone strain, can initiate bone remodeling. However, identifying induced ImP dynamics and bone strain factor in vivo using a non-invasive method still remains challenging. To apply ImP as a means for alteration of BFF, it was hypothesized that non-invasive dynamic hydraulic stimulation (DHS) can induce local ImP with minimal bone strain to potentially elicit osteogenic adaptive responses via bone-muscle coupling. The goal of this study was to evaluate the immediate effects on local and distant ImP and strain in response to a range of loading frequencies using DHS. Simultaneous femoral and tibial ImP and bone strain values were measured in three 15-month-old female Sprague Dawley rats during DHS loading on the tibia with frequencies of 1Hz to 10Hz. DHS showed noticeable effects on ImP induction in the stimulated tibia in a nonlinear fashion in response to DHS over the range of loading frequencies, where peaked at 2Hz. DHS at various loading frequencies generated minimal bone strain in the tibiae. Maximal bone strain measured at all loading frequencies was less than 8με. No detectable induction of ImP or bone strain was observed in the femur. This study suggested that oscillatory DHS may regulate the local fluid dynamics with minimal mechanical strain in bone, which serves critically in bone adaptation. These results clearly implied DHS’s potential as an effective, non-invasive intervention for osteopenia and

  7. Fluid Dynamic of Pressurized Coal Gasifiers.

    SciTech Connect

    Louge, M.T.

    1997-11-01

    Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we have conducted a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea was to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employed a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, experiments employing plastic and glass powders fluidized with mixtures of sulfur hexafluoride, carbon dioxide, helium and air at ambient temperature and pressure achieved hydrodynamic similarity with generic high-temperature risers of variable scale operating at 1 and 8 atm. We interpreted our results in the upper riser using steady, fully developed momentum balances for the gas and solid phases. This analysis showed that, for a wide range of experiments, two parameters capture the dependence of the pressure gradients upon the ratio of the mean gas and solid mass flow rates. The first is the ratio of the mean particle slip and superficial gas velocities. The second represents spatial correlations between the radial profiles of interstitial gas velocity and voidage. Variations of the first with dimensionless parameters indicated that our `atmospheric` and `pressurized` experiments conformed to distinct viscous and inertial regimes. In this study, we established also that the descending velocity

  8. Computational fluid dynamics applications to improve crop production systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Computational fluid dynamics (CFD), numerical analysis and simulation tools of fluid flow processes have emerged from the development stage and become nowadays a robust design tool. It is widely used to study various transport phenomena which involve fluid flow, heat and mass transfer, providing det...

  9. Computational Fluid Dynamics of rising droplets

    SciTech Connect

    Wagner, Matthew; Francois, Marianne M.

    2012-09-05

    The main goal of this study is to perform simulations of droplet dynamics using Truchas, a LANL-developed computational fluid dynamics (CFD) software, and compare them to a computational study of Hysing et al.[IJNMF, 2009, 60:1259]. Understanding droplet dynamics is of fundamental importance in liquid-liquid extraction, a process used in the nuclear fuel cycle to separate various components. Simulations of a single droplet rising by buoyancy are conducted in two-dimensions. Multiple parametric studies are carried out to ensure the problem set-up is optimized. An Interface Smoothing Length (ISL) study and mesh resolution study are performed to verify convergence of the calculations. ISL is a parameter for the interface curvature calculation. Further, wall effects are investigated and checked against existing correlations. The ISL study found that the optimal ISL value is 2.5{Delta}x, with {Delta}x being the mesh cell spacing. The mesh resolution study found that the optimal mesh resolution is d/h=40, for d=drop diameter and h={Delta}x. In order for wall effects on terminal velocity to be insignificant, a conservative wall width of 9d or a nonconservative wall width of 7d can be used. The percentage difference between Hysing et al.[IJNMF, 2009, 60:1259] and Truchas for the velocity profiles vary from 7.9% to 9.9%. The computed droplet velocity and interface profiles are found in agreement with the study. The CFD calculations are performed on multiple cores, using LANL's Institutional High Performance Computing.

  10. Fluid Mechanics, Drag Reduction and Advanced Configuration Aeronautics

    NASA Technical Reports Server (NTRS)

    Bushnell, Dennis M.

    2000-01-01

    This paper discusses Advanced Aircraft configurational approaches across the speed range, which are either enabled, or greatly enhanced, by clever Flow Control. Configurations considered include Channel Wings with circulation control for VTOL (but non-hovering) operation with high cruise speed, strut-braced CTOL transports with wingtip engines and extensive ('natural') laminar flow control, a midwing double fuselage CTOL approach utilizing several synergistic methods for drag-due-to-lift reduction, a supersonic strut-braced configuration with order of twice the L/D of current approaches and a very advanced, highly engine flow-path-integrated hypersonic cruise machine. This paper indicates both the promise of synergistic flow control approaches as enablers for 'Revolutions' in aircraft performance and fluid mechanic 'areas of ignorance' which impede their realization and provide 'target-rich' opportunities for Fluids Research.

  11. Computational fluid dynamics modelling in cardiovascular medicine.

    PubMed

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

    2016-01-01

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

  12. Computational fluid dynamics modelling in cardiovascular medicine

    PubMed Central

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

    2016-01-01

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

  13. Computational fluid dynamics modelling in cardiovascular medicine.

    PubMed

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

    2016-01-01

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

  14. Fluid and structural measurements to advance gas turbine technology

    NASA Technical Reports Server (NTRS)

    Hartmann, M. J.

    1980-01-01

    In the present paper, the current status of fluid and structural measurements is reviewed, and some potential improvements in gas turbine machinery, directly associated with the new measuring capability are discussed. Some considerations concerning the impact of the new capability on the methods and approaches that will be used in the further development of advanced technology, in general, and to aeropropulsion gas turbine machinery, in particular, are presented.

  15. Some Aspects of uncertainty in computational fluid dynamics results

    NASA Technical Reports Server (NTRS)

    Mehta, U. B.

    1991-01-01

    Uncertainties are inherent in computational fluid dynamics (CFD). These uncertainties need to be systematically addressed and managed. Sources of these uncertainty analysis are discussed. Some recommendations are made for quantification of CFD uncertainties. A practical method of uncertainty analysis is based on sensitivity analysis. When CFD is used to design fluid dynamic systems, sensitivity-uncertainty analysis is essential.

  16. A Critical Review of Dynamic Wetting by Complex Fluids: From Newtonian Fluids to Non-Newtonian Fluids and Nanofluids.

    PubMed

    Lu, Gui; Wang, Xiao-Dong; Duan, Yuan-Yuan

    2016-10-01

    Dynamic wetting is an important interfacial phenomenon in many industrial applications. There have been many excellent reviews of dynamic wetting, especially on super-hydrophobic surfaces with physical or chemical coatings, porous layers, hybrid micro/nano structures and biomimetic structures. This review summarizes recent research on dynamic wetting from the viewpoint of the fluids rather than the solid surfaces. The reviewed fluids range from simple Newtonian fluids to non-Newtonian fluids and complex nanofluids. The fundamental physical concepts and principles involved in dynamic wetting phenomena are also reviewed. This review focus on recent investigations of dynamic wetting by non-Newtonian fluids, including the latest experimental studies with a thorough review of the best dynamic wetting models for non-Newtonian fluids, to illustrate their successes and limitations. This paper also reports on new results on the still fledgling field of nanofluid wetting kinetics. The challenges of research on nanofluid dynamic wetting is not only due to the lack of nanoscale experimental techniques to probe the complex nanoparticle random motion, but also the lack of multiscale experimental techniques or theories to describe the effects of nanoparticle motion at the nanometer scale (10(-9) m) on the dynamic wetting taking place at the macroscopic scale (10(-3) m). This paper describes the various types of nanofluid dynamic wetting behaviors. Two nanoparticle dissipation modes, the bulk dissipation mode and the local dissipation mode, are proposed to resolve the uncertainties related to the various types of dynamic wetting mechanisms reported in the literature.

  17. Non-metric fluid dynamics and cosmology on Finsler spacetimes

    NASA Astrophysics Data System (ADS)

    Hohmann, Manuel

    2016-01-01

    We generalize the kinetic theory of fluids, in which the description of fluids is based on the geodesic motion of particles, to spacetimes modeled by Finsler geometry. Our results show that Finsler spacetimes are a suitable background for fluid dynamics and that the equation of motion for a collisionless fluid is given by the Liouville equation, as it is also the case for a metric background geometry. We finally apply this model to collisionless dust and a general fluid with cosmological symmetry and derive the corresponding equations of motion. It turns out that the equation of motion for a dust fluid is a simple generalization of the well-known Euler equations.

  18. 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.

  19. Preface: Recent Advances in Fractional Dynamics.

    PubMed

    Srivastava, H M; Baleanu, Dumitru; Li, Changpin

    2016-08-01

    This Special Focus Issue contains several recent developments and advances on the subject of Fractional Dynamics and its widespread applications in various areas of the mathematical, physical, and engineering sciences. PMID:27586617

  20. Preface: Recent Advances in Fractional Dynamics

    NASA Astrophysics Data System (ADS)

    Srivastava, H. M.; Baleanu, Dumitru; Li, Changpin

    2016-08-01

    This Special Focus Issue contains several recent developments and advances on the subject of Fractional Dynamics and its widespread applications in various areas of the mathematical, physical, and engineering sciences.

  1. Numerical, analytical, experimental study of fluid dynamic forces in seals

    NASA Astrophysics Data System (ADS)

    Shapiro, William; Artiles, Antonio; Aggarwal, Bharat; Walowit, Jed; Athavale, Mahesh M.; Preskwas, Andrzej J.

    1992-04-01

    NASA/Lewis Research Center is sponsoring a program for providing computer codes for analyzing and designing turbomachinery seals for future aerospace and engine systems. The program is made up of three principal components: (1) the development of advanced three dimensional (3-D) computational fluid dynamics codes, (2) the production of simpler two dimensional (2-D) industrial codes, and (3) the development of a knowledge based system (KBS) that contains an expert system to assist in seal selection and design. The first task has been to concentrate on cylindrical geometries with straight, tapered, and stepped bores. Improvements have been made by adoption of a colocated grid formulation, incorporation of higher order, time accurate schemes for transient analysis and high order discretization schemes for spatial derivatives. This report describes the mathematical formulations and presents a variety of 2-D results, including labyrinth and brush seal flows. Extensions of 3-D are presently in progress.

  2. Numerical, analytical, experimental study of fluid dynamic forces in seals

    NASA Technical Reports Server (NTRS)

    Shapiro, William; Artiles, Antonio; Aggarwal, Bharat; Walowit, Jed; Athavale, Mahesh M.; Preskwas, Andrzej J.

    1992-01-01

    NASA/Lewis Research Center is sponsoring a program for providing computer codes for analyzing and designing turbomachinery seals for future aerospace and engine systems. The program is made up of three principal components: (1) the development of advanced three dimensional (3-D) computational fluid dynamics codes, (2) the production of simpler two dimensional (2-D) industrial codes, and (3) the development of a knowledge based system (KBS) that contains an expert system to assist in seal selection and design. The first task has been to concentrate on cylindrical geometries with straight, tapered, and stepped bores. Improvements have been made by adoption of a colocated grid formulation, incorporation of higher order, time accurate schemes for transient analysis and high order discretization schemes for spatial derivatives. This report describes the mathematical formulations and presents a variety of 2-D results, including labyrinth and brush seal flows. Extensions of 3-D are presently in progress.

  3. Computational fluid dynamics for the CFBR : challenges that lie ahead /

    SciTech Connect

    Kashiwa, B. A.; Yang, Wen-ching,

    2001-01-01

    The potential of Computational Fluid Dynamics as a tool for design and analysis of the Circulating Fluidized Bed Reactor is considered. The ruminations are largely philosophical in nature, and are based mainly on experience. An assessment of where CFD may, or may not, be a helpful tool for developing the needed understanding, is furnished. To motivate this assessment, a clarification of what composes a CFD analysis is provided. Status of CFD usage in CFBR problems is summarized briefly. Some successes and failures of CFD in CFBR analysis are also discussed; this suggests a practical way to proceed toward the goal of adding CFD as a useful tool, to be used in combination with well-defined experiments, for CFBR needs. The conclusion is that there remains substantial hope that CFD could be very useful in this application. In order to make the hope a reality, nontrivial, and achievable, advances in multiphase flow theory must be made.

  4. The Fluid Dynamics Demo Kit: Part I

    NASA Astrophysics Data System (ADS)

    Flack, Karen; Underhill, Patrick; Prestridge, Kathy

    2012-11-01

    The goal of this project is to develop a fluid dynamics demonstration/experiment kit that can be used by professors and graduate students at high school outreach events. The demonstrations in the kit will be easy to use and true crowd pleasers in order to inspire understanding and pique curiosity about the physics of flow. The kits will be inexpensive, containing readily available materials so that teachers can duplicate the demonstrations and experiments. The kits will be left with the teachers as a gift from the American Physics Society. The experiments and demonstrations cover the concepts of conservation of mass, momentum, and energy, Bernoulli's equation, frictional losses and the ideal gas law. For each experiment, the teachers will receive presentation material, access to instructional videos, plus a worksheet that can be used in a high school physics classroom. This kit has been developed through the efforts of the APS-DFD Mentoring and Outreach Committee and has received funding from the APS-DFD. Work funded by the APS-DFD.

  5. Visualization of unsteady computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Haimes, Robert

    1995-01-01

    The current computing environment that most researchers are using for the calculation of 3D unsteady Computational Fluid Dynamic (CFD) results is a super-computer class machine. The Massively Parallel Processors (MPP's) such as the 160 node IBM SP2 at NAS and clusters of workstations acting as a single MPP (like NAS's SGI Power-Challenge array) provide the required computation bandwidth for CFD calculations of transient problems. Work is in progress on a set of software tools designed specifically to address visualizing 3D unsteady CFD results in these super-computer-like environments. The visualization is concurrently executed with the CFD solver. The parallel version of Visual3, pV3 required splitting up the unsteady visualization task to allow execution across a network of workstation(s) and compute servers. In this computing model, the network is almost always the bottleneck so much of the effort involved techniques to reduce the size of the data transferred between machines.

  6. Fluid dynamic factors in tracheal pressure measurement.

    PubMed

    Chang, H K; Mortola, J P

    1981-07-01

    Because tracheal pressure measurement generally involves the use of a cannula or an endotracheal tube, fluid dynamic factors may cause a considerable artifact. We present a theoretical explanation of the observed apparent paradox in which the resistance of a tracheal cannula or an endotracheal tube is isolation was found to exceed the resistance of the airways plus the cannula or the tube in situ. By estimating the viscous dissipation and the kinetic energy change in a conduit with sudden variation of cross-sectional area, a predictive model is derived. The predictions are verified by a series of in vitro experiments with both steady and oscillatory flows. The experiments showed that the pressure recorded from the sidearm of a tracheal cannula or endotracheal tube contains an error which, in general, increased with the mean Reynolds' number of the through flow and also depends on the diameter ratio between the trachea and the tube or cannula, the position of the pressure tap, and the frequency of ventilation. When feasible, direct measurement with a needle in the trachea is suggested as a way to avoid the possible artifacts arising from the use fo a side tap of the cannula. Theoretical considerations, as well as in vitro and animal experiments, indicate that adding a properly chosen expansion to the tracheal cannula makes it possible to alter inspiratory and expiratory pressures selectively. This device may prove useful in control of breathing studies. PMID:7263418

  7. Polymer Fluid Dynamics: Continuum and Molecular Approaches.

    PubMed

    Bird, R B; Giacomin, A J

    2016-06-01

    To solve problems in polymer fluid dynamics, one needs the equations of continuity, motion, and energy. The last two equations contain the stress tensor and the heat-flux vector for the material. There are two ways to formulate the stress tensor: (a) One can write a continuum expression for the stress tensor in terms of kinematic tensors, or (b) one can select a molecular model that represents the polymer molecule and then develop an expression for the stress tensor from kinetic theory. The advantage of the kinetic theory approach is that one gets information about the relation between the molecular structure of the polymers and the rheological properties. We restrict the discussion primarily to the simplest stress tensor expressions or constitutive equations containing from two to four adjustable parameters, although we do indicate how these formulations may be extended to give more complicated expressions. We also explore how these simplest expressions are recovered as special cases of a more general framework, the Oldroyd 8-constant model. Studying the simplest models allows us to discover which types of empiricisms or molecular models seem to be worth investigating further. We also explore equivalences between continuum and molecular approaches. We restrict the discussion to several types of simple flows, such as shearing flows and extensional flows, which are of greatest importance in industrial operations. Furthermore, if these simple flows cannot be well described by continuum or molecular models, then it is not necessary to lavish time and energy to apply them to more complex flow problems. PMID:27276553

  8. Transcapillary fluid dynamics during the menstrual cycle.

    PubMed

    Oian, P; Tollan, A; Fadnes, H O; Noddeland, H; Maltau, J M

    1987-04-01

    Transcapillary fluid dynamics in the follicular and luteal phase in women without symptoms of premenstrual syndrome were studied. Interstitial colloid osmotic pressure was measured by the "wick" method and interstitial hydrostatic pressure by the "wick-in-needle" method in subcutaneous tissue on the thorax and ankle. From follicular to luteal phase, the following changes were observed: Colloid osmotic pressures were significantly reduced, both in plasma (mean 2.5 mm Hg) and in the interstitium (thorax mean 1.9 mm Hg and ankle mean 2.0 mm Hg). The interstitial hydrostatic pressures did not change. There were no significant changes in serum albumin, hemoglobin, or hematocrit. A slight, but significant, weight gain was observed (mean 0.7 kg). The reduced plasma and interstitial colloid osmotic pressures in the luteal phase may be due to water retention, but the observed reductions in colloid osmotic pressures are probably not fully explained by simple dilution. A reduction in total protein mass in the luteal phase is suggested.

  9. HYDRA, A finite element computational fluid dynamics code: User manual

    SciTech Connect

    Christon, M.A.

    1995-06-01

    HYDRA is a finite element code which has been developed specifically to attack the class of transient, incompressible, viscous, computational fluid dynamics problems which are predominant in the world which surrounds us. The goal for HYDRA has been to achieve high performance across a spectrum of supercomputer architectures without sacrificing any of the aspects of the finite element method which make it so flexible and permit application to a broad class of problems. As supercomputer algorithms evolve, the continuing development of HYDRA will strive to achieve optimal mappings of the most advanced flow solution algorithms onto supercomputer architectures. HYDRA has drawn upon the many years of finite element expertise constituted by DYNA3D and NIKE3D Certain key architectural ideas from both DYNA3D and NIKE3D have been adopted and further improved to fit the advanced dynamic memory management and data structures implemented in HYDRA. The philosophy for HYDRA is to focus on mapping flow algorithms to computer architectures to try and achieve a high level of performance, rather than just performing a port.

  10. Optimal control of molecular motion expressed through quantum fluid dynamics

    NASA Astrophysics Data System (ADS)

    Dey, Bijoy K.; Rabitz, Herschel; Askar, Attila

    2000-04-01

    A quantum fluid-dynamic (QFD) control formulation is presented for optimally manipulating atomic and molecular systems. In QFD the control quantum system is expressed in terms of the probability density ρ and the quantum current j. This choice of variables is motivated by the generally expected slowly varying spatial-temporal dependence of the fluid-dynamical variables. The QFD approach is illustrated for manipulation of the ground electronic state dynamics of HCl induced by an external electric field.

  11. 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)

  12. Application of wave mechanics theory to fluid dynamics problems: Fundamentals

    NASA Technical Reports Server (NTRS)

    Krzywoblocki, M. Z. V.

    1974-01-01

    The application of the basic formalistic elements of wave mechanics theory is discussed. The theory is used to describe the physical phenomena on the microscopic level, the fluid dynamics of gases and liquids, and the analysis of physical phenomena on the macroscopic (visually observable) level. The practical advantages of relating the two fields of wave mechanics and fluid mechanics through the use of the Schroedinger equation constitute the approach to this relationship. Some of the subjects include: (1) fundamental aspects of wave mechanics theory, (2) laminarity of flow, (3) velocity potential, (4) disturbances in fluids, (5) introductory elements of the bifurcation theory, and (6) physiological aspects in fluid dynamics.

  13. COMPUTATIONAL FLUID DYNAMICS MODELING ANALYSIS OF COMBUSTORS

    SciTech Connect

    Mathur, M.P.; Freeman, Mark; Gera, Dinesh

    2001-11-06

    In the current fiscal year FY01, several CFD simulations were conducted to investigate the effects of moisture in biomass/coal, particle injection locations, and flow parameters on carbon burnout and NO{sub x} inside a 150 MW GEEZER industrial boiler. Various simulations were designed to predict the suitability of biomass cofiring in coal combustors, and to explore the possibility of using biomass as a reburning fuel to reduce NO{sub x}. Some additional CFD simulations were also conducted on CERF combustor to examine the combustion characteristics of pulverized coal in enriched O{sub 2}/CO{sub 2} environments. Most of the CFD models available in the literature treat particles to be point masses with uniform temperature inside the particles. This isothermal condition may not be suitable for larger biomass particles. To this end, a stand alone program was developed from the first principles to account for heat conduction from the surface of the particle to its center. It is envisaged that the recently developed non-isothermal stand alone module will be integrated with the Fluent solver during next fiscal year to accurately predict the carbon burnout from larger biomass particles. Anisotropy in heat transfer in radial and axial will be explored using different conductivities in radial and axial directions. The above models will be validated/tested on various fullscale industrial boilers. The current NO{sub x} modules will be modified to account for local CH, CH{sub 2}, and CH{sub 3} radicals chemistry, currently it is based on global chemistry. It may also be worth exploring the effect of enriched O{sub 2}/CO{sub 2} environment on carbon burnout and NO{sub x} concentration. The research objective of this study is to develop a 3-Dimensional Combustor Model for Biomass Co-firing and reburning applications using the Fluent Computational Fluid Dynamics Code.

  14. 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.

  15. Control of fluid dynamics by nanoparticles in laser melting

    NASA Astrophysics Data System (ADS)

    Ma, Chao; Chen, Lianyi; Xu, Jiaquan; Zhao, Jingzhou; Li, Xiaochun

    2015-03-01

    Effective control of fluid dynamics is of remarkable scientific and practical significance. It is hypothesized that nanoparticles could offer a novel means to control fluid dynamics. In this study, laser melting was used to investigate the feasibility of tuning fluid dynamics by nanoparticles and possibly breaking existing limits of conventional laser processing techniques. Alumina nanoparticles reinforced nickel samples, fabricated through electrocodeposition, were used for laser melting experiments. Since the melt pool surface is controlled by the fluid dynamics, surface topographies were carefully studied to reveal the nanoparticle effect on the fluid dynamics. Characterizations of surface topographies and microstructures of pure Ni and Ni/Al2O3 nanocomposite were carried out before and after laser melting. The surface roughness of the Ni/Al2O3 nanocomposite sample was reduced significantly by laser melting, which broke the existing limit of laser surface polishing of pure Ni. It is believed that the nanoparticles increased the viscosity of the molten metal, thereby enhancing the viscous damping of the capillary oscillations in the melt pool, to produce a much smoother surface. Moreover, the experimental study also revealed that the viscosity enhancement by the nanoparticles effectively suppressed the thermocapillary flows which would introduce artificial asperities on a surface. The experimental results suggest that nanoparticles are effective in controlling melt pool dynamics and overcoming the existing limits of laser processing. The new methodology, fluid dynamics control by nanoparticles, opens a new pathway to enrich liquid based processes for broad applications.

  16. Capillary filling dynamics of viscoelastic fluids

    NASA Astrophysics Data System (ADS)

    Bandopadhyay, Aditya; Ghosh, Uddipta; Chakraborty, Suman

    2014-05-01

    We consider the filling of a capillary by a viscoelastic fluid described by the Phan-Thien-Tanner (PTT) constitutive behavior. By considering both vertical capillary filling and horizontal capillary filling, we demarcate the role played by gravity and fluid rheology towards long-time oscillations in the capillary penetration depth. We also consider the isothermal filling of the capillary for a closed channel and thus bring out the fundamental differences in the nature of capillary filling for PTT and Newtonian fluids for closed channels in comparison to open channels. Through a scaling analysis, we highlight a distinct viscoelastic regime in the horizontal capillary filling which is in contrast to the Washburn scaling seen in the case of Newtonian fluids. Such an analysis with a very general constitutive behavior is therefore expected to shed light on many areas of microfluidics which focus on biofluids that are often well described by the PTT constitutive behavior.

  17. Fluid dynamics: Turbulence spreads like wildfire

    NASA Astrophysics Data System (ADS)

    Graham, Michael D.

    2015-10-01

    A simple model captures the key features of the transition from smooth to turbulent flow for a fluid in a pipe. The findings pave the way for more-complex models and may have engineering ramifications. See Letter p.550

  18. Visualization of Unsteady Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Haimes, Robert

    1997-01-01

    The current compute environment that most researchers are using for the calculation of 3D unsteady Computational Fluid Dynamic (CFD) results is a super-computer class machine. The Massively Parallel Processors (MPP's) such as the 160 node IBM SP2 at NAS and clusters of workstations acting as a single MPP (like NAS's SGI Power-Challenge array and the J90 cluster) provide the required computation bandwidth for CFD calculations of transient problems. If we follow the traditional computational analysis steps for CFD (and we wish to construct an interactive visualizer) we need to be aware of the following: (1) Disk space requirements. A single snap-shot must contain at least the values (primitive variables) stored at the appropriate locations within the mesh. For most simple 3D Euler solvers that means 5 floating point words. Navier-Stokes solutions with turbulence models may contain 7 state-variables. (2) Disk speed vs. Computational speeds. The time required to read the complete solution of a saved time frame from disk is now longer than the compute time for a set number of iterations from an explicit solver. Depending, on the hardware and solver an iteration of an implicit code may also take less time than reading the solution from disk. If one examines the performance improvements in the last decade or two, it is easy to see that depending on disk performance (vs. CPU improvement) may not be the best method for enhancing interactivity. (3) Cluster and Parallel Machine I/O problems. Disk access time is much worse within current parallel machines and cluster of workstations that are acting in concert to solve a single problem. In this case we are not trying to read the volume of data, but are running the solver and the solver outputs the solution. These traditional network interfaces must be used for the file system. (4) Numerics of particle traces. Most visualization tools can work upon a single snap shot of the data but some visualization tools for transient

  19. The Aerospace Plane Design Challenge: Credible Computational Fluid Dynamics Results

    NASA Technical Reports Server (NTRS)

    Mehta, Unmeel B.

    1991-01-01

    The aerospace plane design challenge is presented in the form of the view-graphs. The following topics are included: the CFD design technology development; CFD validation vs. measurable fluid dynamics validation; and discussion of results.

  20. The importance of fluid dynamics for MBR fouling mitigation.

    PubMed

    Böhm, Lutz; Drews, Anja; Prieske, Helmut; Bérubé, Pierre R; Kraume, Matthias

    2012-10-01

    The importance of the multiphase fluid dynamics for fouling mitigation in MBR systems has been widely acknowledged with air sparging having been applied commercially for about 20 years. However, the effects of air scouring are still not fully understood since the transient orthogonal and parallel flows as well as turbulent eddies created by bubbling generate complex hydrodynamic flow fields in the vicinity of a membrane. There is no generally valid model that describes the relationship between fouling rate and fluid dynamics. So, a reliable and universally applicable model to optimize membrane module and tank geometries, air scouring and filtration cycles is still pending. In addition to providing a discussion on the importance of multiphase fluid dynamics for fouling control, this review aims at developing guidelines to choose appropriate experimental and numerical methods for fluid dynamics investigations in MBR systems. PMID:22704186

  1. 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 ...

  2. The coupled dynamics of fluids and spacecraft in low gravity and low gravity fluid measurement

    NASA Technical Reports Server (NTRS)

    Hansman, R. John; Peterson, Lee D.; Crawley, Edward F.

    1987-01-01

    The very large mass fraction of liquids stored on broad current and future generation spacecraft has made critical the technologies of describing the fluid-spacecraft dynamics and measuring or gauging the fluid. Combined efforts in these areas are described, and preliminary results are presented. The coupled dynamics of fluids and spacecraft in low gravity study is characterizing the parametric behavior of fluid-spacecraft systems in which interaction between the fluid and spacecraft dynamics is encountered. Particular emphasis is given to the importance of nonlinear fluid free surface phenomena to the coupled dynamics. An experimental apparatus has been developed for demonstrating a coupled fluid-spacecraft system. In these experiments, slosh force signals are fed back to a model tank actuator through a tunable analog second order integration circuit. In this manner, the tank motion is coupled to the resulting slosh force. Results are being obtained in 1-g and in low-g (on the NASA KC-135) using dynamic systems nondimensionally identical except for the Bond numbers.

  3. 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.

  4. Computational Fluid Dynamics Program at NASA Ames Research Center

    NASA Technical Reports Server (NTRS)

    Holst, Terry L.

    1989-01-01

    The Computational Fluid Dynamics (CFD) Program at NASA Ames Research Center is reviewed and discussed. The technical elements of the CFD Program are listed and briefly discussed. These elements include algorithm research, research and pilot code development, scientific visualization, advanced surface representation, volume grid generation, and numerical optimization. Next, the discipline of CFD is briefly discussed and related to other areas of research at NASA Ames including experimental fluid dynamics, computer science research, computational chemistry, and numerical aerodynamic simulation. These areas combine with CFD to form a larger area of research, which might collectively be called computational technology. The ultimate goal of computational technology research at NASA Ames is to increase the physical understanding of the world in which we live, solve problems of national importance, and increase the technical capabilities of the aerospace community. Next, the major programs at NASA Ames that either use CFD technology or perform research in CFD are listed and discussed. Briefly, this list includes turbulent/transition physics and modeling, high-speed real gas flows, interdisciplinary research, turbomachinery demonstration computations, complete aircraft aerodynamics, rotorcraft applications, powered lift flows, high alpha flows, multiple body aerodynamics, and incompressible flow applications. Some of the individual problems actively being worked in each of these areas is listed to help define the breadth or extent of CFD involvement in each of these major programs. State-of-the-art examples of various CFD applications are presented to highlight most of these areas. The main emphasis of this portion of the presentation is on examples which will not otherwise be treated at this conference by the individual presentations. Finally, a list of principal current limitations and expected future directions is given.

  5. Fluid dynamics of competitive swimming: An experimental study

    NASA Astrophysics Data System (ADS)

    Wei, T.; Voorhees, A.; Mark, R.; Mittal, R.

    2004-11-01

    The world of competitive swimming is dynamic. Swimmers today are bigger, stronger and faster than they ever have been. The training regimen of an elite athlete includes not only endless practice of his or her skills, but also a carefully planned diet, strength and endurance training, and hours of mental preparation. Within this framework, researchers from Rutgers and George Washington Universities have teamed with USA Swimming to develop advanced, fluid dynamics based training and analysis tools for current and future Olympic swimmers. The focus of this presentation will be on the objectives, methodologies and early outcomes of DPIV measurements of flow around swimmers. Testing was conducted at the Olympic training center in Colorado Springs and focussed specifically on the dolphin kick, an undulating motion swimmers use at the beginning of a race and after pushing off from the wall during a turn. Movies of flow measurements around swimmers, including Beth Botsford, the 1996 Olympic Gold Medalist in the 100 m backstroke, will be presented.

  6. Predictive Dynamic Security Assessment through Advanced Computing

    SciTech Connect

    Huang, Zhenyu; Diao, Ruisheng; Jin, Shuangshuang; Chen, Yousu

    2014-11-30

    Abstract— Traditional dynamic security assessment is limited by several factors and thus falls short in providing real-time information to be predictive for power system operation. These factors include the steady-state assumption of current operating points, static transfer limits, and low computational speed. This addresses these factors and frames predictive dynamic security assessment. The primary objective of predictive dynamic security assessment is to enhance the functionality and computational process of dynamic security assessment through the use of high-speed phasor measurements and the application of advanced computing technologies for faster-than-real-time simulation. This paper presents algorithms, computing platforms, and simulation frameworks that constitute the predictive dynamic security assessment capability. Examples of phasor application and fast computation for dynamic security assessment are included to demonstrate the feasibility and speed enhancement for real-time applications.

  7. 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).

  8. Hard sphere dynamics for normal and granular fluids.

    PubMed

    Dufty, James W; Baskaran, Aparna

    2005-06-01

    A fluid of N smooth, hard spheres is considered as a model for normal (elastic collision) and granular (inelastic collision) fluids. The potential energy is discontinuous for hard spheres so that the pairwise forces are singular and the usual forms of Newtonian and Hamiltonian mechanics do not apply. Nevertheless, particle trajectories in the N particle phase space are well defined and the generators for these trajectories can be identified. The first part of this presentation is a review of the generators for the dynamics of observables and probability densities. The new results presented in the second part refer to applications of these generators to the Liouville dynamics for granular fluids. A set of eigenvalues and eigenfunctions of the generator for this Liouville dynamics system is identified in a special stationary representation. This provides a class of exact solutions to the Liouville equation that are closely related to hydrodynamics for granular fluids.

  9. Dynamic Simulations of Advanced Fuel Cycles

    SciTech Connect

    Steven J. Piet; Brent W. Dixon; Jacob J. Jacobson; Gretchen E. Matthern; David E. Shropshire

    2011-03-01

    Years of performing dynamic simulations of advanced nuclear fuel cycle options provide insights into how they could work and how one might transition from the current once-through fuel cycle. This paper summarizes those insights from the context of the 2005 objectives and goals of the U.S. Advanced Fuel Cycle Initiative (AFCI). Our intent is not to compare options, assess options versus those objectives and goals, nor recommend changes to those objectives and goals. Rather, we organize what we have learned from dynamic simulations in the context of the AFCI objectives for waste management, proliferation resistance, uranium utilization, and economics. Thus, we do not merely describe “lessons learned” from dynamic simulations but attempt to answer the “so what” question by using this context. The analyses have been performed using the Verifiable Fuel Cycle Simulation of Nuclear Fuel Cycle Dynamics (VISION). We observe that the 2005 objectives and goals do not address many of the inherently dynamic discriminators among advanced fuel cycle options and transitions thereof.

  10. Application of computational fluid dynamics methods to improve thermal hydraulic code analysis

    NASA Astrophysics Data System (ADS)

    Sentell, Dennis Shannon, Jr.

    A computational fluid dynamics code is used to model the primary natural circulation loop of a proposed small modular reactor for comparison to experimental data and best-estimate thermal-hydraulic code results. Recent advances in computational fluid dynamics code modeling capabilities make them attractive alternatives to the current conservative approach of coupled best-estimate thermal hydraulic codes and uncertainty evaluations. The results from a computational fluid dynamics analysis are benchmarked against the experimental test results of a 1:3 length, 1:254 volume, full pressure and full temperature scale small modular reactor during steady-state power operations and during a depressurization transient. A comparative evaluation of the experimental data, the thermal hydraulic code results and the computational fluid dynamics code results provides an opportunity to validate the best-estimate thermal hydraulic code's treatment of a natural circulation loop and provide insights into expanded use of the computational fluid dynamics code in future designs and operations. Additionally, a sensitivity analysis is conducted to determine those physical phenomena most impactful on operations of the proposed reactor's natural circulation loop. The combination of the comparative evaluation and sensitivity analysis provides the resources for increased confidence in model developments for natural circulation loops and provides for reliability improvements of the thermal hydraulic code.

  11. Advanced numerics for multi-dimensional fluid flow calculations

    SciTech Connect

    Vanka, S.P.

    1984-04-01

    In recent years, there has been a growing interest in the development and use of mathematical models for the simulation of fluid flow, heat transfer and combustion processes in engineering equipment. The equations representing the multi-dimensional transport of mass, momenta and species are numerically solved by finite-difference or finite-element techniques. However despite the multiude of differencing schemes and solution algorithms, and the advancement of computing power, the calculation of multi-dimensional flows, especially three-dimensional flows, remains a mammoth task. The following discussion is concerned with the author's recent work on the construction of accurate discretization schemes for the partial derivatives, and the efficient solution of the set of nonlinear algebraic equations resulting after discretization. The present work has been jointly supported by the Ramjet Engine Division of the Wright Patterson Air Force Base, Ohio, and the NASA Lewis Research Center.

  12. Advanced numerics for multi-dimensional fluid flow calculations

    NASA Technical Reports Server (NTRS)

    Vanka, S. P.

    1984-01-01

    In recent years, there has been a growing interest in the development and use of mathematical models for the simulation of fluid flow, heat transfer and combustion processes in engineering equipment. The equations representing the multi-dimensional transport of mass, momenta and species are numerically solved by finite-difference or finite-element techniques. However despite the multiude of differencing schemes and solution algorithms, and the advancement of computing power, the calculation of multi-dimensional flows, especially three-dimensional flows, remains a mammoth task. The following discussion is concerned with the author's recent work on the construction of accurate discretization schemes for the partial derivatives, and the efficient solution of the set of nonlinear algebraic equations resulting after discretization. The present work has been jointly supported by the Ramjet Engine Division of the Wright Patterson Air Force Base, Ohio, and the NASA Lewis Research Center.

  13. Helicity and singular structures in fluid dynamics

    PubMed Central

    Moffatt, H. Keith

    2014-01-01

    Helicity is, like energy, a quadratic invariant of the Euler equations of ideal fluid flow, although, unlike energy, it is not sign definite. In physical terms, it represents the degree of linkage of the vortex lines of a flow, conserved when conditions are such that these vortex lines are frozen in the fluid. Some basic properties of helicity are reviewed, with particular reference to (i) its crucial role in the dynamo excitation of magnetic fields in cosmic systems; (ii) its bearing on the existence of Euler flows of arbitrarily complex streamline topology; (iii) the constraining role of the analogous magnetic helicity in the determination of stable knotted minimum-energy magnetostatic structures; and (iv) its role in depleting nonlinearity in the Navier-Stokes equations, with implications for the coherent structures and energy cascade of turbulence. In a final section, some singular phenomena in low Reynolds number flows are briefly described. PMID:24520175

  14. Derivation of anisotropic dissipative fluid dynamics from the Boltzmann equation

    NASA Astrophysics Data System (ADS)

    Molnár, Etele; Niemi, Harri; Rischke, Dirk H.

    2016-06-01

    Fluid-dynamical equations of motion can be derived from the Boltzmann equation in terms of an expansion around a single-particle distribution function which is in local thermodynamical equilibrium, i.e., isotropic in momentum space in the rest frame of a fluid element. However, in situations where the single-particle distribution function is highly anisotropic in momentum space, such as the initial stage of heavy-ion collisions at relativistic energies, such an expansion is bound to break down. Nevertheless, one can still derive a fluid-dynamical theory, called anisotropic dissipative fluid dynamics, in terms of an expansion around a single-particle distribution function, f^0 k, which incorporates (at least parts of) the momentum anisotropy via a suitable parametrization. We construct such an expansion in terms of polynomials in energy and momentum in the direction of the anisotropy and of irreducible tensors in the two-dimensional momentum subspace orthogonal to both the fluid velocity and the direction of the anisotropy. From the Boltzmann equation we then derive the set of equations of motion for the irreducible moments of the deviation of the single-particle distribution function from f^0 k. Truncating this set via the 14-moment approximation, we obtain the equations of motion of anisotropic dissipative fluid dynamics.

  15. Fracturing fluid characterization: State-of-the-art facility and advanced technology

    SciTech Connect

    Shah, S., Asadi, M.,

    1997-10-01

    The petroleum industry has used hydraulic fracturing technique to stimulate low and high permeability oil and gas reservoirs to enhance their potential recoveries. Nevertheless, the design and implementation of a scientifically and economically sound fracturing job, due to the lack of knowledge of theological behavior of hydraulic fracturing fluids under field conditions, remains a challenge. Furthermore, as often the case, the current level of technical knowledge with research institutes, service companies, and operators does not translate to field applications. One of the principal reasons for this technology gap, is the lack of understanding of the theological behavior of hydraulic fracturing fluids under field conditions, which primarily relates to the limitations in scaling down the field conditions to the laboratory. The Fracturing Fluid Characterization Facility (FFCF) project was therefore, proposed with the intent of providing the industry with a better understanding of the behavior of these fracturing fluids and their proppant transport characteristics under downhole fracture condition. At the FFCF, a fully operational High Pressure Simulator (HPS), as seen in Figure 1, constitutes a vertical, variable width, parallel plate flow apparatus and is capable of operating at elevated temperatures (up to 2500F) and pressures (up to 1200 psi). The HPS simulates, to the maximum degree practical, all conditions experienced by a fracturing fluid from its formulation on the surface, its flow down the wellbore, through perforations, its injection into the fracture, and its leakage into the rock formation (Figure 1). Together with the onsite auxiliary equipment (Figure 2), such as Mixing and Pumping System, Pre-conditioning System, Data Acquisition System, and Rheology Measuring System (Figure 2), the HPS is the most advanced fracture simulator available to conduct research, mimicking field conditions, in the following areas: Rheology Characterization of Fracturing

  16. Fluid dynamics: In pursuit of turbulence

    NASA Astrophysics Data System (ADS)

    Knebel, Johannes; Weber, Markus F.; Frey, Erwin

    2016-03-01

    In the transition from laminar to turbulent pipe flow, puffs of turbulence form, split and decay. The phenomenology and lifetime of these turbulent puffs exhibit population dynamics that also drive predator-prey ecosystems on the edge of extinction.

  17. Dynamic high pressure: Why it makes metallic fluid hydrogen

    NASA Astrophysics Data System (ADS)

    Nellis, W. J.

    2015-09-01

    Metallic fluid H has been made by dynamic compression decades after Wigner and Huntington (WH) predicted its existence in 1935. The density at which it was made is within a few percent of the density predicted by WH. Metallic fluid H was achieved by multiple-shock compression of liquid H2, which is quasi-isentropic and thermally equilibrated. That is, the compressions were isentropic but for enough temperature and entropy to drive the crossover to completion from H2 to H at 9-fold compression. The metallic fluid is highly degenerate: T/TF≈0.014. The basic ideas of dynamic compression, also known as supersonic, adiabatic, nonlinear hydrodynamics, were developed in the last half of the Nineteenth Century in European universities. Today dynamic compression is generally unfamiliar to the scientific community, which impedes general understanding as to why fluid H becomes metallic at a pressure observable in a laboratory. The purposes of this paper are to (i) present a brief review of dynamic compression and its affects on materials, (ii) review considerations that led to the sample holder designed specifically to make metallic fluid H, and (iii) present a brief inter-comparison of dynamic and static methods to achieve high pressure relative to their prospects for making metallic H.

  18. Experimental analysis on MR fluid channel flow dynamics with complex fluid-wall interactions

    NASA Astrophysics Data System (ADS)

    Nishiyama, Hideya; Takana, Hidemasa; Shinohara, Keisuke; Mizuki, Kotoe; Katagiri, Kazunari; Ohta, Makoto

    2011-05-01

    MR fluid plugging performance by aggregation of magnetized particles in MR fluid is recently expected to be one of the most promising applications in medical or safety devices, such as blood flow control, steam issuing shut-down valve and fuel supply control for automobile. In this study, dynamic response of MR fluid plugging and its breakdown in a pressure mode with complex fluid-wall interactions was experimentally investigated, considering the effects of magnetic flux density, wall surface structure, wall permeability and wall elasticity of tube. Higher endurance pressure is obtained for wall surface groove structure and for steel wall due to a strong anchoring effect by rigid cluster formation in a concave region and strong MR fluid column formation in a channel core region, respectively. Furthermore, MR fluid plugging performance and the fluid storage characteristic of PVA tube as a bio-material was clarified. Because of the large radial expansion of the tube at the applied magnetic region in a pressure mode, PVA tube shows unique characteristics, such as storing MR fluid under magnetic field and MR fluid jet issuing under releasing magnetic field.

  19. Encyclopedia of fluid mechanics. Volume 2 - Dynamics of single-fluid flows and mixing

    NASA Astrophysics Data System (ADS)

    Cheremisinoff, N. P.

    Various papers on the dynamics of single-fluid flows and mixing are presented. The general topics addressed include: channel and free surface flows, mixing phenomena and practices, and fluid transport equipment. Individual papers discuss: statistics of deep water surface waves, unstable turbulent channel flow, hydraulic jumps and internal flows, wave attenuation in open channel flow, straight sediment stable channels, three-dimensional deep-water waves, estimating peak flows, hydrodynamics of laminar buoyant jets, impinging jets, hydrodynamics of confined coaxial jets, and turbulent mixing and diffusion of jets. Also addressed are: hydrodynamics of jets in cross flow, modelling turbulent jets in cross flow, batchwise jet mixing in tanks, stability of jets in liquid-liquid systems, jet mixing of fluids in vessels, mixing in loop reactors, backmixing in stirred vessels, industrial mixing equipment, pump classifications and design features, oscillating displacement pumps, fluid dynamics of inducers, hydrodynamics of outflow from vessels, and analysis of axial flow turbines.

  20. Fluid dynamics and noise in bacterial scattering

    NASA Astrophysics Data System (ADS)

    Dunkel, Jorn; Drescher, Knut; Cisneros, Luis; Ganguly, Sujoy; Goldstein, Raymond

    2011-03-01

    Bacterial communication through chemical and physical channels is permanently challenged by internal and external noise. While the role of stochastic fluctuations in quorum sensing has been widely studied both theoretically and experimentally, our understanding of hydrodynamic interactions between bacteria is limited by the absence of empirical data. Here, we report the first direct measurement of the fluid flow generated by an individual bacterium far away from and near to a wall. The experiments show that the micro-hydrodynamics of E. coli are considerably different from that of more complex eucaryotes as, for example, Chlamydomonas algae. We discuss the implications of our results for bacterial cell-cell and cell-wall interactions.

  1. Climate dynamics and fluid mechanics: Natural variability and related uncertainties

    NASA Astrophysics Data System (ADS)

    Ghil, Michael; Chekroun, Mickaël D.; Simonnet, Eric

    2008-08-01

    The purpose of this review-and-research paper is twofold: (i) to review the role played in climate dynamics by fluid-dynamical models; and (ii) to contribute to the understanding and reduction of the uncertainties in future climate-change projections. To illustrate the first point, we review recent theoretical advances in studying the wind-driven circulation of the oceans. In doing so, we concentrate on the large-scale, wind-driven flow of the mid-latitude oceans, which is dominated by the presence of a larger, anticyclonic and a smaller, cyclonic gyre. The two gyres share the eastward extension of western boundary currents, such as the Gulf Stream or Kuroshio, and are induced by the shear in the winds that cross the respective ocean basins. The boundary currents and eastward jets carry substantial amounts of heat and momentum, and thus contribute in a crucial way to Earth’s climate, and to changes therein. Changes in this double-gyre circulation occur from year to year and decade to decade. We study this low-frequency variability of the wind-driven, double-gyre circulation in mid-latitude ocean basins, via the bifurcation sequence that leads from steady states through periodic solutions and on to the chaotic, irregular flows documented in the observations. This sequence involves local, pitchfork and Hopf bifurcations, as well as global, homoclinic ones. The natural climate variability induced by the low-frequency variability of the ocean circulation is but one of the causes of uncertainties in climate projections. The range of these uncertainties has barely decreased, or even increased, over the last three decades. Another major cause of such uncertainties could reside in the structural instability-in the classical, topological sense-of the equations governing climate dynamics, including but not restricted to those of atmospheric and ocean dynamics. We propose a novel approach to understand, and possibly reduce, these uncertainties, based on the concepts and

  2. Parallel Domain Decomposition Preconditioning for Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Barth, Timothy J.; Chan, Tony F.; Tang, Wei-Pai; Kutler, Paul (Technical Monitor)

    1998-01-01

    This viewgraph presentation gives an overview of the parallel domain decomposition preconditioning for computational fluid dynamics. Details are given on some difficult fluid flow problems, stabilized spatial discretizations, and Newton's method for solving the discretized flow equations. Schur complement domain decomposition is described through basic formulation, simplifying strategies (including iterative subdomain and Schur complement solves, matrix element dropping, localized Schur complement computation, and supersparse computations), and performance evaluation.

  3. 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.

  4. Static and dynamic response of a fluid-fluid interface to electric point and line charge

    SciTech Connect

    Ellingsen, Simen A Brevik, Iver

    2012-12-15

    We consider the behavior of a dielectric fluid-fluid interface in the presence of a strong electric field from a point charge and line charge, respectively, both statically and, in the latter case, dynamically. The fluid surface is elevated above its undisturbed level until balance is reached between the electromagnetic lifting force, gravity and surface tension. We derive ordinary differential equations for the shape of the fluid-fluid interface which are solved numerically with standard means, demonstrating how the elevation depends on field strength and surface tension coefficient. In the dynamic case of a moving line charge, the surface of an inviscid liquid-liquid interface is left to oscillate behind the moving charge after it has been lifted against the force of gravity. We show how the wavelength of the oscillations depends on the relative strength of the forces of gravity and inertia, whereas the amplitude of the oscillations is a nontrivial function of the velocity at which the line charge moves. - Highlights: Black-Right-Pointing-Pointer Fluid surface elevation analyzed near a static point and line charge. Black-Right-Pointing-Pointer Elevation determined by interaction of gravity, dielectric force and surface tension. Black-Right-Pointing-Pointer Dynamic equation of motion for the moving line charge is derived. Black-Right-Pointing-Pointer Surface waves behind moving charge calculated and analysed for different velocities.

  5. Chemical Dynamics at the Advanced Light Source

    SciTech Connect

    Baer, T.; Berrah, N.; Fadley, C.; Moore, C.B.; Neumark, D.M.; Ng, C.Y.; Ruscic, B.; Smith, N.V.; Suits, A.G.; Wodtke, A.M.

    1999-02-02

    A day-long retreat was held January 15, 1999 to chart the future directions for chemical dynamics studies at the Advanced Light Source. This represents an important period for the Chemical Dynamics Beamline, as the hardware is well-developed, most of the initial experimental objectives have been realized and the mission is now to identify the future scientific priorities for the beamline and attract users of the highest caliber. To this end, we have developed a detailed scientific program for the near term; identified and prioritized the long range scientific opportunities, identified essential new hardware, and outlined an aggressive outreach program to involve the chemical physics community.

  6. 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.

  7. Fluid dynamic constraints on resource acquisition in small pelagic organisms

    NASA Astrophysics Data System (ADS)

    Kiørboe, T.

    2016-07-01

    Physicists have long examined the fluid dynamics of swimming at low Reynolds number, but the main scope has rarely been to understand the behavior and ecology of microorganisms. However, many ecological questions about the functioning of small aquatic organisms can only be addressed by the application of formal fluid physics. Here, I examine resource acquisition mechanisms in small aquatic organisms, ranging from uptake of dissolved molecules to feeding on suspended particulate prey, and examine how organism behaviors and morphologies may be shaped by the often non-intuitive small-scale fluid physics.

  8. Fluid-dynamic and aeroacoustic investigations of shrouded jets

    NASA Astrophysics Data System (ADS)

    Veerasamy, V.

    1980-08-01

    The fluid dynamic and aeroacoustic characteristics of a high subsonic jet discharging from a shrouded nozzle were investigated theoretically and experimentally to explore the possibility of jet noise reduction and thrust augmentation for STOL/VTOL aircraft. The preliminary design calculations of an adiabatic shrouded nozzle were performed by solving iteratively the one dimensional fluid dynamic equations governing the compressible flow. A two dimensional flow model, consisting of second order partial differential equations of a parabolic type, was used to find the effect of shroud length on the ejector performance. This model consists of the conservation laws with thin shear layer assumptions incorporating the Prandtl's mixing length hypothesis for turbulence closure. A numerical integration method was used to solve the governing fluid dynamic equations of motion. The aeroacoustic characteristics of the shrouded jet were analyzed based on the Lighthill's V(8) law.

  9. A Textbook for a First Course in Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Zingg, D. W.; Pulliam, T. H.; Nixon, David (Technical Monitor)

    1999-01-01

    This paper describes and discusses the textbook, Fundamentals of Computational Fluid Dynamics by Lomax, Pulliam, and Zingg, which is intended for a graduate level first course in computational fluid dynamics. This textbook emphasizes fundamental concepts in developing, analyzing, and understanding numerical methods for the partial differential equations governing the physics of fluid flow. Its underlying philosophy is that the theory of linear algebra and the attendant eigenanalysis of linear systems provides a mathematical framework to describe and unify most numerical methods in common use in the field of fluid dynamics. Two linear model equations, the linear convection and diffusion equations, are used to illustrate concepts throughout. Emphasis is on the semi-discrete approach, in which the governing partial differential equations (PDE's) are reduced to systems of ordinary differential equations (ODE's) through a discretization of the spatial derivatives. The ordinary differential equations are then reduced to ordinary difference equations (O(Delta)E's) using a time-marching method. This methodology, using the progression from PDE through ODE's to O(Delta)E's, together with the use of the eigensystems of tridiagonal matrices and the theory of O(Delta)E's, gives the book its distinctiveness and provides a sound basis for a deep understanding of fundamental concepts in computational fluid dynamics.

  10. Design patterns for training fluid dynamics experimentalists

    NASA Astrophysics Data System (ADS)

    Tagg, Randall

    2012-11-01

    What practical knowledge would your ideal lab student, technician or even postdoc possess? Borrowing the idea of design patterns from the fields of architecture and computer science, we claim that there are technical problems common to many investigations with often-used design solutions. These would form a useful repertoire that thoughtful practitioners can adapt. Creatively breaking the rules is also encouraged. We invite other ideas for fluid experiment design patterns towards the end of creating a web-based resource that helps new experimentalists get up to speed quickly. We are creating such a resource so that it also serves pre-college students invited into research experiences and inventive citizen scientists exploring new technologies.

  11. NACHOS2. Incompressible Viscous Fluid Dynamics

    SciTech Connect

    Gartling, D.K.

    1992-02-21

    NACHOS2 is a finite element program designed for the analysis of two-dimensional, incompressible viscous fluid flow problems. The basic flows considered may be isothermal, nonisothermal, or may involve other physical processes, such as mass transport. Both steady and transient flows may be analyzed. The class of problems treated are those described by the two-dimensional (plane or axisymmetric) incompressible form of the Navier-Stokes equations. An energy transport equation is included in the formulation for problems in which heat transfer effects are important. Two auxiliary transport equations can be added to describe other physical processes,e.g. mass transfer, chemical reactions. Among the specific types of flow problems treated are: isothermal flow; forced, free, or mixed convection; conjugate heat transfer; flow in saturated porous media with or without heat transfer; and inelastic, non-Newtonian flows with or without heat transfer. Other problem classes are possible depending on the specific definitions applied to the auxiliary transport equations.

  12. Dynamic characterization of extremely bidisperse magnetorheological fluids.

    PubMed

    Iglesias, G R; López-López, M T; Durán, J D G; González-Caballero, F; Delgado, A V

    2012-07-01

    In this work, we investigate the stability and redispersibility of magnetorheological fluids (MRFs). These are disperse systems where the solid is constituted by ferro- or ferri-magnetic microparticles. Upon the application of external magnetic field, they experience rapid and reversible increases in yield stress and viscosity. The problem considered here is first of all the determination of their stability against sedimentation, an essential issue in their practical application. Although this problem is typically faced through the addition of thixotropic agents to the liquid medium, in this work, we propose the investigation of the effect of magnetic nanoparticles addition, so that the dispersion medium is in reality a ferrofluid. It is found that a volume fraction of nanoparticles not higher than 3% is enough to provide a long-lasting stabilization to MRFs containing above 30% iron microparticles. In the, in fact unavoidable, event of settling, the important point is the ease of redispersion of the sediment. This is indirectly evaluated in the present investigation by measuring the penetration force in the suspension, using a standard hardness needle. Again, it is found that the nanoparticles addition produces soft sediments by avoiding short-range attractions between the large iron particles. Finally, the performance of the designed MRFs is evaluated by obtaining their steady-state rheograms for different volume fractions of magnetite and different magnetic field strengths. The yield stress is found to be strongly field-dependent, and it can achieve the high values expected in standard magnetorheological fluids but with improved stability and redispersibility. PMID:22520211

  13. Rate-dependent extensional "dynamic ligaments" using shear thickening fluids

    NASA Astrophysics Data System (ADS)

    Nenno, Paul T.; Wetzel, Eric D.

    2014-04-01

    A novel "dynamic ligament" smart material that exhibits a strongly rate-dependent response in extension is developed and characterized. The devices, based on elastomeric polymers and shear thickening fluids, exhibit low resistance to extension at rates below 10 mm/s, but when stretched at 100 mm/s or higher resist with up to 7 × higher force. A link between the shear thickening fluid's rheology and the dynamic ligament's tensile performance is presented to explain the rate-dependent response. Future recommendations for improving device performance are presented, along with a host of different potential application areas including safety equipment, adaptive braces, sporting goods, and military equipment.

  14. NASA Computational Fluid Dynamics Conference. Volume 1: Sessions 1-6

    NASA Technical Reports Server (NTRS)

    1989-01-01

    Presentations given at the NASA Computational Fluid Dynamics (CFD) Conference held at the NASA Ames Research Center, Moffett Field, California, March 7-9, 1989 are given. Topics covered include research facility overviews of CFD research and applications, validation programs, direct simulation of compressible turbulence, turbulence modeling, advances in Runge-Kutta schemes for solving 3-D Navier-Stokes equations, grid generation and invicid flow computation around aircraft geometries, numerical simulation of rotorcraft, and viscous drag prediction for rotor blades.

  15. Dynamical density functional theory for molecular and colloidal fluids: a microscopic approach to fluid mechanics.

    PubMed

    Archer, A J

    2009-01-01

    In recent years, a number of dynamical density functional theories (DDFTs) have been developed for describing the dynamics of the one-body density of both colloidal and atomic fluids. In the colloidal case, the particles are assumed to have stochastic equations of motion and theories exist for both the case when the particle motion is overdamped and also in the regime where inertial effects are relevant. In this paper, we extend the theory and explore the connections between the microscopic DDFT and the equations of motion from continuum fluid mechanics. In particular, starting from the Kramers equation, which governs the dynamics of the phase space probability distribution function for the system, we show that one may obtain an approximate DDFT that is a generalization of the Euler equation. This DDFT is capable of describing the dynamics of the fluid density profile down to the scale of the individual particles. As with previous DDFTs, the dynamical equations require as input the Helmholtz free energy functional from equilibrium density functional theory (DFT). For an equilibrium system, the theory predicts the same fluid one-body density profile as one would obtain from DFT. Making further approximations, we show that the theory may be used to obtain the mode coupling theory that is widely used for describing the transition from a liquid to a glassy state.

  16. Computational modeling of glow discharge-induced fluid dynamics

    NASA Astrophysics Data System (ADS)

    Jayaraman, Balaji

    Glow discharge at atmospheric pressure using a dielectric barrier discharge can induce fluid flow and operate as an actuator for flow control. The largely isothermal surface plasma generation realized above can modify the near-wall flow structure by means of Lorentzian collisions between the ionized fluid and the neutral fluid. Such an actuator has advantages of no moving parts, performance at atmospheric conditions and devising complex control strategies through the applied voltage. However, the mechanism of the momentum coupling between the plasma and the fluid flow is not yet adequately understood. In the present work, a modeling framework is presented to simulate athermal, non-equilibrium plasma discharges in conjunction with low Mach number fluid dynamics at atmospheric pressure. The plasma and fluid species are treated as a two-fluid system exhibiting a few decades of length and time scales. The effect of the plasma dynamics on the fluid dynamics is devised via a body force treatment in the Navier-Stokes equations. Two different approaches of different degrees of fidelity are presented for modeling the plasma dynamics. The first approach, a phenomenological model, is based on a linearized force distribution approximating the discharge structure, and utilizing experimental guidance to deduce the empirical constants. A high fidelity approach is to model the plasma dynamics in a self-consistent manner using a first principle-based hydrodynamic plasma model. The atmospheric pressure regime of interest here enables us to employ local equilibrium assumptions, signifying efficient collisional energy exchange as against thermal heating from inelastic collision processes. The time scale ratios between convection, diffusion, and reaction/ionization mechanisms are O(107), making the system computationally stiff. To handle the stiffness, a sequential finite-volume operator-splitting algorithm capable of conserving space charge is developed; the approach can handle time

  17. Equilibrium and nonequilibrium dynamics of soft sphere fluids.

    PubMed

    Ding, Yajun; Mittal, Jeetain

    2015-07-14

    We use computer simulations to test the freezing-point scaling relationship between equilibrium transport coefficients (self-diffusivity, viscosity) and thermodynamic parameters for soft sphere fluids. The fluid particles interact via the inverse-power potential (IPP), and the particle softness is changed by modifying the exponent of the distance-dependent potential term. In the case of IPP fluids, density and temperature are not independent variables and can be combined to obtain a coupling parameter to define the thermodynamic state of the system. We find that the rescaled coupling parameter, based on its value at the freezing point, can approximately collapse the diffusivity and viscosity data for IPP fluids over a wide range of particle softness. Even though the collapse is far from perfect, the freezing-point scaling relationship provides a convenient and effective way to compare the structure and dynamics of fluid systems with different particle softness. We further show that an alternate scaling relationship based on two-body excess entropy can provide an almost perfect collapse of the diffusivity and viscosity data below the freezing transition. Next, we perform nonequilibrium molecular dynamics simulations to calculate the shear-dependent viscosity and to identify the distinct role of particle softness in underlying structural changes associated with rheological properties. Qualitatively, we find a similar shear-thinning behavior for IPP fluids with different particle softness, though softer particles exhibit stronger shear-thinning tendency. By investigating the distance and angle-dependent pair correlation functions in these systems, we find different structural features in the case of IPP fluids with hard-sphere like and softer particle interactions. Interestingly, shear-thinning in hard-sphere like fluids is accompanied by enhanced translational order, whereas softer fluids exhibit loss of order with shear. Our results provide a systematic evaluation

  18. Green Algae as Model Organisms for Biological Fluid Dynamics*

    PubMed Central

    Goldstein, Raymond E.

    2015-01-01

    In the past decade the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimetres), their geometric regularity, the ease with which they can be cultured and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms. PMID:26594068

  19. Green Algae as Model Organisms for Biological Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Goldstein, Raymond E.

    2015-01-01

    In the past decade, the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimeters), their geometric regularity, the ease with which they can be cultured, and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms.

  20. Nonlinear dynamics of fluid-structure systems. Annual technical report

    SciTech Connect

    Moon, F.C.; Muntean, G.

    1994-01-01

    We are investigating the nonlinear dynamics of a row of cylindrical tubes excited by the cross flow of fluid. Both experimental and analytical/numerical studies have been conducted. The goal of this research is to look for low dimensional dynamic models in flow- induced vibrations using modern methods of dynamical systems and chaos theory. The experimental study uses a 25 cm {times} 25 cm wind tunnel with flow velocity in the range of 15 m/sec. The use of a wind tunnel to explore dynamic phenomenon compliments the work of Chen at Argonne National Laboratory who also is conducting experiments with a water tunnel. The principal nonlinearities studies are impact constraints due to gaps in the cylinder supports and nonlinear fluid forces.

  1. Cerebrospinal Fluid Mechanics and Its Coupling to Cerebrovascular Dynamics

    NASA Astrophysics Data System (ADS)

    Linninger, Andreas A.; Tangen, Kevin; Hsu, Chih-Yang; Frim, David

    2016-01-01

    Cerebrospinal fluid (CSF) is not stagnant but displays fascinating oscillatory flow patterns inside the ventricular system and reversing fluid exchange between the cranial vault and spinal compartment. This review provides an overview of the current knowledge of pulsatile CSF motion. Observations contradicting classical views about its bulk production and clearance are highlighted. A clinical account of diseases of abnormal CSF flow dynamics, including hydrocephalus, syringomyelia, Chiari malformation type 1, and pseudotumor cerebri, is also given. We survey medical imaging modalities used to observe intracranial dynamics in vivo. Additionally, we assess the state of the art in predictive models of CSF dynamics. The discussion addresses open questions regarding CSF dynamics as they relate to the understanding and management of diseases.

  2. Fluid dynamics of aortic valve stenosis

    NASA Astrophysics Data System (ADS)

    Keshavarz-Motamed, Zahra; Maftoon, Nima

    2009-11-01

    Aortic valve stenosis, which causes considerable constriction of the flow passage, is one of the most frequent cardiovascular diseases and is the most common cause of the valvular replacements which take place for around 100,000 per year in North America. Furthermore, it is considered as the most frequent cardiac disease after arterial hypertension and coronary artery disease. The objective of this study is to develop an analytical model considering the coupling effect between fluid flow and elastic deformation with reasonable boundary conditions to describe the effect of AS on the left ventricle and the aorta. The pulsatile and Newtonian blood flow through aortic stenosis with vascular wall deformability is analyzed and its effects are discussed in terms of flow parameters such as velocity, resistance to flow, shear stress distribution and pressure loss. Meanwhile we developed analytical expressions to improve the comprehension of the transvalvular hemodynamics and the aortic stenosis hemodynamics which is of great interest because of one main reason. To medical scientists, an accurate knowledge of the mechanical properties of whole blood flow in the aorta can suggest a new diagnostic tool.

  3. Fluid dynamics of double diffusive systems

    SciTech Connect

    Koseff, J.R.

    1990-04-03

    The major accomplishments of our initial research period (August 1, 1987, to March 1, 1990) are as follows; we completed construction of the experimental facility. Originally, it had been our intent to modify an existing facility in our laboratory. When this became impractical we constructed a new stand-alone facility. Modified an existing three-dimensional numerical code developed in our laboratory, SEAFLOS1, by incorporating a salinity transport equation. Developed experimental and analytical techniques, and performed both physical and numerical experiments for a wide range of initial and boundary conditions. Focused our overall research effort to answer the following four questions pertaining to the formation of convective intrusions due to lateral temperature gradients established by sidewall heating. (1) What is the internal structure of the convective intrusions as a function of the initial stratification and sidewall heating rates (2) What is the correct scaling for the initial vertical dimension of the intrusions (3) How does the merging process vary as a function of initial stratification and sidewall heating rate (4) Is the sidewall heating critical for continued propagation of the intrusions, or is it merely a trigger which releases the internal instability in the fluid

  4. Fluid dynamics of double diffusive systems

    SciTech Connect

    Koseff, J.R.

    1989-04-07

    A study of mixing processes in doubly diffusive systems is being conducted. Continuous gradients of two diffusing components (heat and salinity in our case) are being used as initial conditions, and forcing is introduced by lateral heating and surface shear. The goals of the proposed work include: (1) quantification of the effects of finite amplitude disturbances on stable, double diffusive systems, particularly with respect to lateral heating, (2) development of an improved understanding of the physical phenomena present in wind-driven shear flows in double diffusive stratified environments, (3) increasing our knowledge-base on turbulent flow in stratified environments and how to represent it, and (4) formulation of a numerical code for such flows. The work is being carried out in an experimental facility which is located in the Stanford Environmental Fluid Mechanics Laboratory, and on laboratory minicomputers and CRAY computers. In particular we are focusing on the following key issues: (1) the formation and propagation of double diffusive intrusions away from a heated wall and the effects of lateral heating on the double diffusive system; (2) the interaction between the double diffusively influenced fluxes and the turbulence induced fluxes; (3) the measurement of heat and mass fluxes; and (4) the influence of double diffusive gradients on mixed layer deepening. 1 fig.

  5. Molecular Dynamics Simulation of Binary Fluid in a Nanochannel

    SciTech Connect

    Mullick, Shanta; Ahluwalia, P. K.; Pathania, Y.

    2011-12-12

    This paper presents the results from a molecular dynamics simulation of binary fluid (mixture of argon and krypton) in the nanochannel flow. The computational software LAMMPS is used for carrying out the molecular dynamics simulations. Binary fluids of argon and krypton with varying concentration of atom species were taken for two densities 0.65 and 0.45. The fluid flow takes place between two parallel plates and is bounded by horizontal walls in one direction and periodic boundary conditions are imposed in the other two directions. To drive the flow, a constant force is applied in one direction. Each fluid atom interacts with other fluid atoms and wall atoms through Week-Chandler-Anderson (WCA) potential. The velocity profile has been looked at for three nanochannel widths i.e for 12{sigma}, 14{sigma} and 16{sigma} and also for the different concentration of two species. The velocity profile of the binary fluid predicted by the simulations agrees with the quadratic shape of the analytical solution of a Poiseuille flow in continuum theory.

  6. Silverton Conference on Applications of the Zero Gravity Space Shuttle Environment to Problems in Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Eisner, M. (Editor)

    1974-01-01

    The possible utilization of the zero gravity resource for studies in a variety of fluid dynamics and fluid-dynamic related problems was investigated. A group of experiments are discussed and described in detail; these include experiments in the areas of geophysical fluid models, fluid dynamics, mass transfer processes, electrokinetic separation of large particles, and biophysical and physiological areas.

  7. Optimization of Fluid Front Dynamics in Porous Media Using Rate Control: I. Equal Mobility Fluids

    SciTech Connect

    Sundaryanto, Bagus; Yortsos, Yanis C.

    1999-10-18

    In applications involving this injection of a fluid in a porous medium to displace another fluid, a main objective is the maximization of the displacement efficiency. For a fixed arrangement of injection and production points (sources and sinks), such optimization is possible by controlling the injection rate policy. Despite its practical relevance, however, this aspect has received scant attention in the literature. In this paper, a fundamental approach based on optimal control theory, for the case when the fluids are miscible, of equal viscosity and in the absence of dispersion and gravity effects. Both homogeneous and heterogeneous porous media are considered. From a fluid dynamics viewpoint, this is a problem in the deformation of material lines in porous media, as a function of time-varying injection rates.

  8. Cytoskeletal dynamics and lung fluid balance.

    PubMed

    Vogel, Stephen M; Malik, Asrar B

    2012-01-01

    This article examines the role of the endothelial cytoskeleton in the lung's ability to restrict fluid and protein to vascular space at normal vascular pressures and thereby to protect lung alveoli from lethal flooding. The barrier properties of microvascular endothelium are dependent on endothelial cell contact with other vessel-wall lining cells and with the underlying extracellular matrix (ECM). Focal adhesion complexes are essential for attachment of endothelium to ECM. In quiescent endothelial cells, the thick cortical actin rim helps determine cell shape and stabilize endothelial adherens junctions and focal adhesions through protein bridges to actin cytoskeleton. Permeability-increasing agonists signal activation of "small GTPases" of the Rho family to reorganize the actin cytoskeleton, leading to endothelial cell shape change, disassembly of cortical actin rim, and redistribution of actin into cytoplasmic stress fibers. In association with calcium- and Src-regulated myosin light chain kinase (MLCK), stress fibers become actinomyosin-mediated contractile units. Permeability-increasing agonists stimulate calcium entry and induce tyrosine phosphorylation of VE-cadherin (vascular endothelial cadherin) and β-catenins to weaken or pull apart endothelial adherens junctions. Some permeability agonists cause latent activation of the small GTPases, Cdc42 and Rac1, which facilitate endothelial barrier recovery and eliminate interendothelial gaps. Under the influence of Cdc42 and Rac1, filopodia and lamellipodia are generated by rearrangements of actin cytoskeleton. These motile evaginations extend endothelial cell borders across interendothelial gaps, and may initiate reannealing of endothelial junctions. Endogenous barrier protective substances, such as sphingosine-1-phosphate, play an important role in maintaining a restrictive endothelial barrier and counteracting the effects of permeability-increasing agonists.

  9. A Computational Fluid Dynamics Algorithm on a Massively Parallel Computer

    NASA Technical Reports Server (NTRS)

    Jespersen, Dennis C.; Levit, Creon

    1989-01-01

    The discipline of computational fluid dynamics is demanding ever-increasing computational power to deal with complex fluid flow problems. We investigate the performance of a finite-difference computational fluid dynamics algorithm on a massively parallel computer, the Connection Machine. Of special interest is an implicit time-stepping algorithm; to obtain maximum performance from the Connection Machine, it is necessary to use a nonstandard algorithm to solve the linear systems that arise in the implicit algorithm. We find that the Connection Machine ran achieve very high computation rates on both explicit and implicit algorithms. The performance of the Connection Machine puts it in the same class as today's most powerful conventional supercomputers.

  10. Aerodynamic design optimization with sensitivity analysis and computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Baysal, Oktay

    1995-01-01

    An investigation was conducted from October 1, 1990 to May 31, 1994 on the development of methodologies to improve the designs (more specifically, the shape) of aerodynamic surfaces of coupling optimization algorithms (OA) with Computational Fluid Dynamics (CFD) algorithms via sensitivity analyses (SA). The study produced several promising methodologies and their proof-of-concept cases, which have been reported in the open literature.

  11. Recent applications of spectral methods in fluid dynamics

    NASA Technical Reports Server (NTRS)

    Zang, T. A.; Hussaini, M. Y.

    1985-01-01

    Origins of spectral methods, especially their relation to the method of weighted residuals, are surveyed. Basic Fourier and Chebyshev spectral concepts are reviewed and demonstrated through application to simple model problems. Both collocation and tau methods are considered. These techniques are then applied to a number of difficult, nonlinear problems of hyperbolic, parabolic, elliptic and mixzed type. Fluid dynamical applications are emphasized.

  12. Current capabilities and future directions in computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    1986-01-01

    A summary of significant findings is given, followed by specific recommendations for future directions of emphasis for computational fluid dynamics development. The discussion is organized into three application areas: external aerodynamics, hypersonics, and propulsion - and followed by a turbulence modeling synopsis.

  13. Multiscale Behavior of Viscous Fluids Dynamics: Experimental Observations

    NASA Astrophysics Data System (ADS)

    Arciniega-Ceballos, Alejandra; Spina, Laura; Scheu, Bettina; Dingwell, Donald B.

    2016-04-01

    The dynamics of Newtonian fluids with viscosities of mafic to intermediate silicate melts (10-1000 Pa s) during slow decompression present multi-time scale processes. To observe these processes we have performed several experiments on silicon oil saturated with Argon gas for 72 hours, in a Plexiglas autoclave. The slow decompression, dropping from 10 MPa to ambient pressure, acting as the excitation mechanism, triggered several processes with their own distinct timescales. These processes generate complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit flanked by high-speed video recordings. The analysis in time and frequency of these time series and their correlation with the associated high-speed imaging enables the characterization of distinct phases and the extraction of the individual processes during the evolution of decompression of these viscous fluids. We have observed fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution along the conduit. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the conduit system. Our observations point to the great potential of this experimental approach in the understanding of volcanic conduit dynamics and volcanic seismicity.

  14. Fluid Dynamical Profiles and Constants of Motionfrom d-Branes

    NASA Astrophysics Data System (ADS)

    Jackiw, R.; Polychronakos, A. P.

    Various fluid mechanical systems enjoy a hidden, higher-dimensional dynamical Poincaré symmetry, which arises owing to their descent from a Nambu-Goto action. Also, for the same reason, there are equivalence transformations between different models. These interconnections, summarized by the diagram below, are discussed in our paper.

  15. Nonlinear Dynamic Models in Advanced Life Support

    NASA Technical Reports Server (NTRS)

    Jones, Harry

    2002-01-01

    To facilitate analysis, ALS systems are often assumed to be linear and time invariant, but they usually have important nonlinear and dynamic aspects. Nonlinear dynamic behavior can be caused by time varying inputs, changes in system parameters, nonlinear system functions, closed loop feedback delays, and limits on buffer storage or processing rates. Dynamic models are usually cataloged according to the number of state variables. The simplest dynamic models are linear, using only integration, multiplication, addition, and subtraction of the state variables. A general linear model with only two state variables can produce all the possible dynamic behavior of linear systems with many state variables, including stability, oscillation, or exponential growth and decay. Linear systems can be described using mathematical analysis. Nonlinear dynamics can be fully explored only by computer simulations of models. Unexpected behavior is produced by simple models having only two or three state variables with simple mathematical relations between them. Closed loop feedback delays are a major source of system instability. Exceeding limits on buffer storage or processing rates forces systems to change operating mode. Different equilibrium points may be reached from different initial conditions. Instead of one stable equilibrium point, the system may have several equilibrium points, oscillate at different frequencies, or even behave chaotically, depending on the system inputs and initial conditions. The frequency spectrum of an output oscillation may contain harmonics and the sums and differences of input frequencies, but it may also contain a stable limit cycle oscillation not related to input frequencies. We must investigate the nonlinear dynamic aspects of advanced life support systems to understand and counter undesirable behavior.

  16. The Effective Field Theory Approach to Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Endlich, Solomon George Shamsuddin Osman

    In this thesis we initiate a systematic study of fluid dynamics using the effective field theory (EFT) program. We consider the canonical quantization of an ordinary fluid in an attempt to discover if there is some kind of quantum mechanical inconsistency with ordinary fluids at zero temperature. The system exhibits a number of peculiarities associated with the vortex degrees of freedom. We also study the dynamics of a nearly incompressible fluid via (classical) effective field theory. In the kinematical regime corresponding to near incompressibility (small fluid velocities and accelerations), compressional modes are, by definition, difficult to excite, and can be dealt with perturbatively. We systematically outline the corresponding perturbative expansion, which can be thought of as an expansion in the ratio of fluid velocity and speed of sound. This perturbation theory allows us to compute many interesting quantities associated with sound-flow interactions. Additionally, we also improve on the so-called vortex filament model, by providing a local field theory describing the dynamics of vortex-line systems and their interaction with sound, to all orders in perturbation theory. Next, we develop a cosmological model where primordial inflation is driven by a 'solid'. The low energy EFT describing such a system is just a less symmetric version of the action of a fluid---it lacks the volume preserving diffeomorphism. The symmetry breaking pattern of this system differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations. And finally, we introduce dissipative effects in the effective field theory of hydrodynamics. We do this in a model-independent fashion by coupling the long-distance degrees of freedom explicitly kept in the effective field theory

  17. Computational fluid dynamics modeling for emergency preparedness & response

    SciTech Connect

    Lee, R.L.; Albritton, J.R.; Ermak, D.L.; Kim, J.

    1995-07-01

    Computational fluid dynamics (CFD) has played an increasing role in the improvement of atmospheric dispersion modeling. This is because many dispersion models are now driven by meteorological fields generated from CFD models or, in numerical weather prediction`s terminology, prognostic models. Whereas most dispersion models typically involve one or a few scalar, uncoupled equations, the prognostic equations are a set of highly-coupled, nonlinear equations whose solution requires a significant level of computational power. Until recently, such computer power could be found only in CRAY-class supercomputers. Recent advances in computer hardware and software have enabled modestly-priced, high performance, workstations to exhibit the equivalent computation power of some mainframes. Thus desktop-class machines that were limited to performing dispersion calculations driven by diagnostic wind fields may now be used to calculate complex flows using prognostic CFD models. The Atmospheric Release and Advisory Capability (ARAC) program at Lawrence Livermore National Laboratory (LLNL) has, for the past several years, taken advantage of the improvements in hardware technology to develop a national emergency response capability based on executing diagnostic models on workstations. Diagnostic models that provide wind fields are, in general, simple to implement, robust and require minimal time for execution. Such models have been the cornerstones of the ARAC operational system for the past ten years. Kamada (1992) provides a review of diagnostic models and their applications to dispersion problems. However, because these models typically contain little physics beyond mass-conservation, their performance is extremely sensitive to the quantity and quality of input meteorological data and, in spite of their utility, can be applied with confidence to only modestly complex flows.

  18. Computational fluid dynamics modeling for emergency preparedness and response

    SciTech Connect

    Lee, R.L.; Albritton, J.R.; Ermak, D.L.; Kim, J.

    1995-02-01

    Computational fluid dynamics (CFD) has (CFD) has played an increasing in the improvement of atmospheric dispersion modeling. This is because many dispersion models are now driven by meteorological fields generated from CFD models or, in numerical weather prediction`s terminology, prognostic models. Whereas most dispersion models typically involve one or a few scalar, uncoupled equations, the prognostic equations are a set of highly-couple equations whose solution requires a significant level of computational power. Recent advances in computer hardware and software have enabled modestly-priced, high performance, workstations to exhibit the equivalent computation power of some mainframes. Thus desktop-class machines that were limited to performing dispersion calculations driven by diagnostic wind fields may now be used to calculate complex flows using prognostic CFD models. The Release and Advisory Capability (ARAC) program at Lawrence Livermore National Laboratory (LLNL) has, for the past several years, taken advantage of the improvements in hardware technology to develop a national emergency response capability based on executing diagnostic models on workstations. Diagnostic models that provide wind fields are, in general, simple to implement, robust and require minimal time for execution. Because these models typically contain little physics beyond mass-conservation, their performance is extremely sensitive to the quantity and quality of input meteorological data and, in spite of their utility, can be applied with confidence to only modestly complex flows. We are now embarking on a development program to incorporate prognostic models to generate, in real-time, the meteorological fields for the dispersion models. In contrast to diagnostic models, prognostic models are physically-based and are capable of incorporating many physical processes to treat highly complex flow scenarios.

  19. The aerospace plane design challenge - Credible computational fluid dynamics results

    NASA Technical Reports Server (NTRS)

    Mehta, Unmeel B.

    1990-01-01

    In order to establish the credibility of CFD results utilized in aerospace plane design, the following topics are discussed: CFD validation in relation to 'measureable' fluid dynamics (MFD) validation, credibility requirements, responsibility for credibility, and a guide for establishing credibility. What is of paramount concern for fluid dynamic design is not CFD code validation but qualification of CFD unknowns so that their magnitude is greatly reduced and that these uncertainties are employed for designing with margin. The designers must be trained to properly use CFD if they are to produce good designs. In approximately 70 percent of the flight envelopes of SSTO aerospace planes with supersonic combustion, CFD will be necessary to determine dynamics performance and specifications.

  20. Sandia National Laboratories Environmental Fluid Dynamics Code V. 1 0.0 (Beta)

    2015-10-20

    The DOE has funded Sandia National Labs (SNL) to develop an open-source modeling tool to guide the design and layout of marine hydrokinetic (MHK) arrays to maximize power production while minimizing environmental effects. This modeling framework simulates flows through and around MHK arrays while quantifying environmental responses. As an augmented version of US EPA's Environmental Fluid Dynamics Code (EFDC), SNL-EFDC includes: (1) a new module that simulates energy conversion (momentum withdrawal) by MHK devices withmore » commensurate changes in the turbulent kinetic energy and its dissipation rate, (2) new, advanced sediment dynamics routines, and (3) augmented water quality modules.« less

  1. Sandia National Laboratories Environmental Fluid Dynamics Code V. 1 0.0 (Beta)

    SciTech Connect

    2015-10-20

    The DOE has funded Sandia National Labs (SNL) to develop an open-source modeling tool to guide the design and layout of marine hydrokinetic (MHK) arrays to maximize power production while minimizing environmental effects. This modeling framework simulates flows through and around MHK arrays while quantifying environmental responses. As an augmented version of US EPA's Environmental Fluid Dynamics Code (EFDC), SNL-EFDC includes: (1) a new module that simulates energy conversion (momentum withdrawal) by MHK devices with commensurate changes in the turbulent kinetic energy and its dissipation rate, (2) new, advanced sediment dynamics routines, and (3) augmented water quality modules.

  2. Two-dimensional dynamic fluid bowtie attenuators.

    PubMed

    Hermus, James R; Szczykutowicz, Timothy P

    2016-01-01

    Fluence field modulated (FFM) CT allows for improvements in image quality and dose reduction. To date, only one-dimensional modulators have been proposed, as the extension to two-dimensional (2-D) modulation is difficult with solid-metal attenuation-based fluence field modulated designs. This work proposes to use liquid and gas to attenuate the x-ray beam, as unlike solids, these materials can be arranged allowing for 2-D fluence modulation. The thickness of liquid and the pressure for a given path length of gas were determined that provided the same attenuation as 30 cm of soft tissue at 80, 100, 120, and 140 kV. Liquid iodine, zinc chloride, cerium chloride, erbium oxide, iron oxide, and gadolinium chloride were studied. Gaseous xenon, uranium hexafluoride, tungsten hexafluoride, and nickel tetracarbonyl were also studied. Additionally, we performed a proof-of-concept experiment using a 96 cell array in which the liquid thickness in each cell was adjusted manually. Liquid thickness varied as a function of kV and chemical composition, with erbium oxide allowing for the smallest thickness. For the gases, tungsten hexaflouride required the smallest pressure to compensate for 30 cm of soft tissue. The 96 cell iodine attenuator allowed for a reduction in both dynamic range to the detector and scatter-to-primary ratio. For both liquids and gases, when k-edges were located within the diagnostic energy range used for imaging, the mean beam energy exhibited the smallest change with compensation amount. The thickness of liquids and the gas pressure seem logistically implementable within the space constraints of C-arm-based cone beam CT (CBCT) and diagnostic CT systems. The gas pressures also seem logistically implementable within the space and tube loading constraints of CBCT and diagnostic CT systems. PMID:26835499

  3. Advanced tomographic flow diagnostics for opaque multiphase fluids

    SciTech Connect

    Torczynski, J.R.; O`Hern, T.J.; Adkins, D.R.; Jackson, N.B.; Shollenberger, K.A.

    1997-05-01

    This report documents the work performed for the ``Advanced Tomographic Flow Diagnostics for Opaque Multiphase Fluids`` LDRD (Laboratory-Directed Research and Development) project and is presented as the fulfillment of the LDRD reporting requirement. Dispersed multiphase flows, particularly gas-liquid flows, are industrially important to the chemical and applied-energy industries, where bubble-column reactors are employed for chemical synthesis and waste treatment. Due to the large range of length scales (10{sup {minus}6}-10{sup 1}m) inherent in real systems, direct numerical simulation is not possible at present, so computational simulations are forced to use models of subgrid-scale processes, the accuracy of which strongly impacts simulation fidelity. The development and validation of such subgrid-scale models requires data sets at representative conditions. The ideal measurement techniques would provide spatially and temporally resolved full-field measurements of the distributions of all phases, their velocity fields, and additional associated quantities such as pressure and temperature. No technique or set of techniques is known that satisfies this requirement. In this study, efforts are focused on characterizing the spatial distribution of the phases in two-phase gas-liquid flow and in three-phase gas-liquid-solid flow. Due to its industrial importance, the bubble-column geometry is selected for diagnostics development and assessment. Two bubble-column testbeds are utilized: one at laboratory scale and one close to industrial scale. Several techniques for measuring the phase distributions at conditions of industrial interest are examined: level-rise measurements, differential-pressure measurements, bulk electrical impedance measurements, electrical bubble probes, x-ray tomography, gamma-densitometry tomography, and electrical impedance tomography.

  4. Enhanced Fluid Mixing in Nanochannels: A Molecular Dynamics Study

    NASA Astrophysics Data System (ADS)

    Oliver, Eric C. J.; Slater, Gary W.

    2006-03-01

    The efficient mixing of fluids is of paramount importance in several applications such as lab-on-a-chip and microfluidic devices. The main limitation to efficiency is that on small scales where the Reynolds number of the flow is low, mixing is dominated by diffusion. Purely diffusive motion is very slow and is an inefficient mixing mechanism unless the channel width is extremely small. Starting with the basic result for diffusive mixing of a binary fluid in a Poiseuille flow we explore methods to enhance the level of mixing between the two fluid species. We simulate the system using Molecular Dynamics and model the fluids as assemblies of Lennard-Jones beads. In order to increase the rate of mixing we have forced lateral motion in the fluid using configurations of mid-stream posts. Specifically, posts set in a prism-like structure have proven to be extremely well suited to reducing the channel length required to achieve complete mixing. In order to measure efficiency we have proposed a mathematical function that quantifies the level mixing associated with a fluid element. Furthermore, we have developed a basic theory for the position of the mixing front in a flow with spatially dependent velocity and diffusion coefficient.

  5. The dynamical regime of fluid flow at the core surface

    NASA Astrophysics Data System (ADS)

    Bloxham, Jeremy

    1988-06-01

    An alternative method for determining the fluid motion immediately beneath the core-mantle boundary is presented which is based on solving the full nonlinear core motions problem. This method is used to examine three dynamical hypotheses about the flow: (1) the steady motions hypothesis; (2) the geostrophic hypothesis; and (3) the toroidal flow hypothesis. Better fits to the field are obtained with the toroidal flows than with geostrophic flows, casting considerable doubt on the validity of the geostrophic hypothesis. Additionally, some indication is found that failure of the frozen-flux approximation, a concomitant assumption, may be a serious obstacle to obtaining reliable maps of the core fluid flow.

  6. Cellular Biotechnology Operations Support System Fluid Dynamics Investigation

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Aboard the International Space Station (ISS), the Tissue Culture Medium (TCM) is the bioreactor vessel in which cell cultures are grown. With its two syringe ports, it is much like a bag used to administer intravenous fluid, except it allows gas exchange needed for life. The TCM contains cell culture medium, and when frozen cells are flown to the ISS, they are thawed and introduced to the TCM through the syringe ports. In the Cellular Biotechnology Operations Support System-Fluid Dynamics Investigation (CBOSS-FDI) experiment, several mixing procedures are being assessed to determine which method achieves the most uniform mixing of growing cells and culture medium.

  7. Particle hopping vs. fluid-dynamical models for traffic flow

    SciTech Connect

    Nagel, K.

    1995-12-31

    Although particle hopping models have been introduced into traffic science in the 19509, their systematic use has only started recently. Two reasons for this are, that they are advantageous on modem computers, and that recent theoretical developments allow analytical understanding of their properties and therefore more confidence for their use. In principle, particle hopping models fit between microscopic models for driving and fluiddynamical models for traffic flow. In this sense, they also help closing the conceptual gap between these two. This paper shows connections between particle hopping models and traffic flow theory. It shows that the hydrodynamical limits of certain particle hopping models correspond to the Lighthill-Whitham theory for traffic flow, and that only slightly more complex particle hopping models produce already the correct traffic jam dynamics, consistent with recent fluid-dynamical models for traffic flow. By doing so, this paper establishes that, on the macroscopic level, particle hopping models are at least as good as fluid-dynamical models. Yet, particle hopping models have at least two advantages over fluid-dynamical models: they straightforwardly allow microscopic simulations, and they include stochasticity.

  8. 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. PMID:25618456

  9. Superfluid-like dynamics in active vortex fluids

    NASA Astrophysics Data System (ADS)

    Slomka, Jonasz; Dunkel, Jorn

    Active biological fluids exhibit rich non-equilibrium dynamics and share striking similarities with quantum fluids, from vortex formation and magnetic ordering to superfluid-like behavior. Building on universality ideas, we have recently proposed a generalization of the Navier-Stokes equations that captures qualitatively the active bulk flow structures observed in bacterial suspensions. Here, we present new numerical simulations that explicitly account for boundary and shear effects. The theory successfully reproduces recent experimental observations of bacterial suspensions, including a superfluid-like regime of nearly vanishing shear viscosity. Our simulations further predict a geometry-induced 'quantization' of viscosity and the existence of excited states capable of performing mechanical work. It is plausible that these results generalize to a broad a class of fluids that are subject to an active scale selection mechanism.

  10. 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.

  11. Measurement of interstage fluid-annulus dynamical properties

    NASA Technical Reports Server (NTRS)

    Adams, M. L.; Makay, E.; Diaz-Tous, I. A.

    1982-01-01

    The work described in this paper is part of an Electric Power Research Institute sponsored effort to improve rotor vibrational performance on power plant feed water pumps. A major objective of this effort is to reduce vibration levels by devising inter-stage sealing configurations with optimized damping capacity, realizing that the typical multi-stage centrifugal pump has several ore inter-stage fluid annuli than it has journal bearings. Also, the fluid annuli are distributed between the journal bearings where vibration levels are highest and can therefore be 'exercised' more as dampers than can the bearings. Described in this paper is a test apparatus which has been built to experimentally determine fluid-annulus dynamical coefficients for various configurations of inter-stage sealing geometry.

  12. Inertial Effects and Interface Dynamics during Rapid Fluid Reconfigurations

    NASA Astrophysics Data System (ADS)

    Lunati, I.; Ferrari, A.

    2014-12-01

    Inertial effects are generally neglected when modeling flow through porous media owing to the low flow rate. In case of multiphase flow, however, the presence of interfaces greatly complicates the dynamics of fluid displacement, leading to abrupt and spontaneous fluid redistribution (e.g., Haines jumps). We use numerical simulations (based on the solution of the Navier Stokes equation and on the Volume-Of-Fluid method) to investigate the role of inertia during these events and assess their impact on macroscopic quantities. We demonstrate that the characteristic velocity of the reconfiguration events is in general unaffected by the injection rate: it is solely determined by the released amount of surface energy. Local velocities largely exceed typical injection velocity. We performed an energy-based analysis of this process and we demonstrate that inertia dominates the reconfiguration dynamics, leading to damped oscillations with their own timescale. In complex media, the oscillations are so frequent and so persistent that they affect the fluid distribution and, consequently, the work done by the external forces, which is related to macroscopic quantities such as relative and unsaturated permeabilities.

  13. Sedimentation dynamics of disks in a linearly stratified fluid

    NASA Astrophysics Data System (ADS)

    Mercier, Matthieu; Pemeja, Justin; Ern, Patricia

    2014-11-01

    The settling dynamics of small objects in a stratified fluid is important to understand the fate of the biomass in lakes or oceanic environments, for industrial applications such as waste-water disposal for instance. Recent numerical and theoretical studies dedicated to freely falling (or rising) bodies in stratified environments have shown some important differences compared to the same problem in a homogeneous fluid. Experimental results are still needed for validation, especially at low and moderate values of the Reynolds number, Re = Ud / ν <= 100 , with U the instantaneous vertical velocity of the object, d its characteristic length, and ν the kinematic velocity of the fluid. We present original experimental results of freely falling disks of finite thickness in a linearly stratified fluid. Three-dimensional trajectories and the wake of the object are obtained using a pair of cameras visualizing two perpendicular planes, revealing a strong influence of the stratification on the dynamics of the object. In particular, the stratification enhances the steady drag experienced by the disks when falling broadside; and generates a change of stability for the disk orientation (from horizontal to vertical) when the Re number decreases below a threshold value.

  14. Development of computational fluid dynamics at NASA Ames Research Center

    NASA Technical Reports Server (NTRS)

    Inouye, M.

    1984-01-01

    Ames Research Center has the lead role among NASA centers to conduct research in computational fluid dynamics. The past, the present, and the future prospects in this field are reviewed. Past accomplishments include pioneering computer simulations of fluid dynamics problems that have made computers valuable in complementing wind tunnels for aerodynamic research. The present facilities include the most powerful computers built in the United States. Three examples of viscous flow simulations are presented: an afterbody with an exhaust plume, a blunt fin mounted on a flat plate, and the Space Shuttle. The future prospects include implementation of the Numerical Aerodynamic Simulation Processing System that will provide the capability for solving the viscous flow field around an aircraft in a matter of minutes.

  15. Dynamics of rotating fluids described by scalar potentials

    NASA Astrophysics Data System (ADS)

    Seyed-Mahmoud, Behnam; Rochester, Michael

    2006-06-01

    The oscillatory dynamics of a rotating, self-gravitating, stratified, compressible, inviscid fluid body is simplified by an exact description in terms of three scalar fields which are constructed from the dilatation, and the perturbations in pressure and gravitational potential [Seyed-Mahmoud, B., 1994. Wobble/nutation of a rotating ellipsoidal Earth with liquid core: implementation of a new set of equations describing dynamics of rotating fluids M.Sc. Thesis, Memorial University of Newfoundland]. We test the method by applying it to compressible, but neutrally-stratified, models of the Earth's liquid core, including a solid inner core, and compute the frequencies of some of the inertial modes. We conclude the method should be further exploited for astrophysical and geophysical normal mode computations.

  16. Streaming potential-modulated capillary filling dynamics of immiscible fluids.

    PubMed

    Bandopadhyay, Aditya; Mandal, Shubhadeep; Chakraborty, Suman

    2016-02-21

    The pressure driven transport of two immiscible electrolytes in a narrow channel with prescribed surface potential (zeta potential) is considered under the influence of a flow-induced electric field. The latter consideration is non-trivially and fundamentally different from the problem of electric field-driven motion (electroosmosis) of two immiscible electrolytes in a channel in a sense that in the former case, the genesis of the induced electric field, termed as streaming potential, is the advection of ions in the absence of any external electric field. As the flow occurs, one fluid displaces the other. Consequently, in cases where the conductivities of the two fluids differ, imbibition dynamically alters the net conductivity of the channel. We emphasize, through numerical simulations, that the alteration in the net conductivity has a significant impact on the contact line dynamics and the concomitant induced streaming potential. The results presented herein are expected to shed light on multiphase electrokinetics devices.

  17. Dynamic fluid-loss characteristics of CO/sub 2/ foam fracturing fluids

    SciTech Connect

    Harris, P.C.

    1984-09-01

    High quality carbon dioxide foam fracturing has become a very popular new stimulation tool in the past two years. Dynamic fluid loss measurements were performed on a broad range of core samples to measure the effect of several parameters on CO/sub 2/ foam fluid loss coefficients. The parameters tested were core permeability, foam quality, gelling agent concentration in the aqueous phase, and core temperature. Measurements were performed in a recirculating fluid flow test loop. A variation of one order of magnitude in Cw for two orders of magnitude change in permeability was observed from 0.02 to 10 md. For permeability below 1 md, there was no effect due to quality. Fluid loss control improved as gelling agent concentration in the liquid phase increased. Cw increased with increasing temperature due to temperature thinning of the aqueous phase. Passage of CO/sub 2/ foams through porous media caused a significant modification in quality from the input to the effluent fluid. The ratio of liquid to gas passing through the core was measured as a function of core permeability, quality and gelling agent concentration. In low permeability cores flow proceeded as separate phases; whereas, in higher permeability cores, the foam structure remained more nearly intact. CO/sub 2/ foams were found to be very similar to N/sub 2/ foams with respect to the above parameters.

  18. Synovial fluid dynamics with small disc perforation in temporomandibular joint.

    PubMed

    Xu, Y; Zhan, J; Zheng, Y; Han, Y; Zhang, Z; Xi, Y; Zhu, P

    2012-10-01

    The articular disc plays an important role as a stress absorber in joint movement, resulting in stress reduction and redistribution in the temporomandibular joint (TMJ). The flow of synovial fluid in the TMJ may follow a regular pattern during movement of the jaw. We hypothesised that the regular pattern is disrupted when the TMJ disc is perforated. By computed tomography arthrography, we studied the upper TMJ compartment in patients with small disc perforation during jaw opening-closing at positions from 0 to 3 cm. Finite element fluid dynamic modelling was accomplished to analyse the pattern of fluid flow and pressure distribution during the movements. The results showed that the fluid flow in the upper compartment generally formed an anticlockwise circulation but with local vortexes with the jaw opening up to 2 cm. However, when the jaw opening-closing reached 3 cm, an abnormal flow field and the fluid pressure change associated with the perforation may increase the risk of perforation expansion or rupture and is unfavourable for self-repair of the perforated disc. PMID:22582815

  19. Fluid dynamics following flow shut-off in bottle filling

    NASA Astrophysics Data System (ADS)

    Thete, Sumeet; Appathurai, Santosh; Gao, Haijing; Basaran, Osman

    2012-11-01

    Bottle filling is ubiquitous in industry. Examples include filling of bottles with shampoos and cleaners, engine oil and pharmaceuticals. In these examples, fluid flows out of a nozzle to fill bottles in an assembly line. Once the required volume of fluid has flowed out of the nozzle, the flow is shut off. However, an evolving fluid thread or string may remain suspended from the nozzle following flow shut-off and persist. This stringing phenomenon can be detrimental to a bottle filling operation because it can adversely affect line speed and filling accuracy by causing uncertainty in fill volume, product loss and undesirable marring of the bottles' exterior surfaces. The dynamics of stringing are studied numerically primarily by using the 1D, slender-jet approximation of the flow equations. A novel feature entails development and use of a new boundary condition downstream of the nozzle exit to expedite the computations. While the emphasis is on stringing of Newtonian fluids and use of 1D approximations, results will also be presented for situations where (a) the fluids are non-Newtonian and (b) the full set of equations are solved without invoking the 1D approximation. Phase diagrams will be presented that identify conditions for which stringing can be problematic.

  20. Dynamics of flexible molecules in thinning fluid filaments

    NASA Astrophysics Data System (ADS)

    Arratia, Paulo E.; Juarez, Gabriel

    2011-11-01

    Newtonian liquids that contain small amounts (~ppm) of flexible polymers can exhibit viscoelastic behavior in extensional flows. In this talk, we report the results of experiments on the thinning and breakup of polymeric fluids in a simple microfluidic device. We aim to understand the stretching dynamics of flexible polymers by direct visualization of fluorescent DNA molecules, a model polymer. A Boger fluid, composed of 100 ppm polyacrylamide and 85% w/w glycerol, is seeded with stained lambdaâDNA molecules (<10% v/v) imaged by high speed epifluorescence microscopy. We observe that the strong flow in the thinning fluid threads provide sufficient forces to stretch the DNA molecules away from their equilibrium coiled state. The distribution of stretch lengths, however, is very heterogeneous due to molecular individualism and initial conditions. Once the molecules are stretched to their full length and aligned with the flow, they translate along the fluid thread as rigid rods until the point of pinch off. After pinch off, both the fluid and molecules return to a relaxed state.

  1. Introduction to finite-difference methods for numerical fluid dynamics

    SciTech Connect

    Scannapieco, E.; Harlow, F.H.

    1995-09-01

    This work is intended to be a beginner`s exercise book for the study of basic finite-difference techniques in computational fluid dynamics. It is written for a student level ranging from high-school senior to university senior. Equations are derived from basic principles using algebra. Some discussion of partial-differential equations is included, but knowledge of calculus is not essential. The student is expected, however, to have some familiarity with the FORTRAN computer language, as the syntax of the computer codes themselves is not discussed. Topics examined in this work include: one-dimensional heat flow, one-dimensional compressible fluid flow, two-dimensional compressible fluid flow, and two-dimensional incompressible fluid flow with additions of the equations of heat flow and the {Kappa}-{epsilon} model for turbulence transport. Emphasis is placed on numerical instabilities and methods by which they can be avoided, techniques that can be used to evaluate the accuracy of finite-difference approximations, and the writing of the finite-difference codes themselves. Concepts introduced in this work include: flux and conservation, implicit and explicit methods, Lagrangian and Eulerian methods, shocks and rarefactions, donor-cell and cell-centered advective fluxes, compressible and incompressible fluids, the Boussinesq approximation for heat flow, Cartesian tensor notation, the Boussinesq approximation for the Reynolds stress tensor, and the modeling of transport equations. A glossary is provided which defines these and other terms.

  2. Fluid dynamics and solidification of levitated drops and shells

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.

    1990-01-01

    The fluid dynamic investigaton of simple free liquid drops is described based on ground-based and low-gravity experimental results. The behavior of compound drops and liquid shells as described in recent theoretical and experimental studies is discussed. Experimental investigations using both levitation devices and drop tubes are considered in the case of 1-g laboratory investigations, highlighting the advantages and drawbacks of both techniques.

  3. Attractors of equations of non-Newtonian fluid dynamics

    NASA Astrophysics Data System (ADS)

    Zvyagin, V. G.; Kondrat'ev, S. K.

    2014-10-01

    This survey describes a version of the trajectory-attractor method, which is applied to study the limit asymptotic behaviour of solutions of equations of non-Newtonian fluid dynamics. The trajectory-attractor method emerged in papers of the Russian mathematicians Vishik and Chepyzhov and the American mathematician Sell under the condition that the corresponding trajectory spaces be invariant under the translation semigroup. The need for such an approach was caused by the fact that for many equations of mathematical physics for which the Cauchy initial-value problem has a global (weak) solution with respect to the time, the uniqueness of such a solution has either not been established or does not hold. In particular, this is the case for equations of fluid dynamics. At the same time, trajectory spaces invariant under the translation semigroup could not be constructed for many equations of non-Newtonian fluid dynamics. In this connection, a different approach to the construction of trajectory attractors for dissipative systems was proposed in papers of Zvyagin and Vorotnikov without using invariance of trajectory spaces under the translation semigroup and is based on the topological lemma of Shura-Bura. This paper presents examples of equations of non-Newtonian fluid dynamics (the Jeffreys system describing movement of the Earth's crust, the model of motion of weak aqueous solutions of polymers, a system with memory) for which the aforementioned construction is used to prove the existence of attractors in both the autonomous and the non-autonomous cases. At the beginning of the paper there is also a brief exposition of the results of Ladyzhenskaya on the existence of attractors of the two-dimensional Navier-Stokes system and the result of Vishik and Chepyzhov for the case of attractors of the three-dimensional Navier-Stokes system. Bibliography: 34 titles.

  4. Circular Couette cell for two-dimensional fluid dynamics experiments

    NASA Astrophysics Data System (ADS)

    Fontana, P. W.; Kearney-Fischer, M.; Rogers, S.; Ulmen, J. V.; Windell, S.

    2007-03-01

    A novel experiment to investigate fluid dynamics in quasi-two-dimensional flows has been built. A soap film is suspended horizontally in an annular channel with a rotating outer boundary, providing mean flow shear, and a vortex array is forced electromagnetically. The experiment will investigate sheared flow stability and the effect of mean flow shear on local vorticity and coherent structures. Particle image velocimetry measurements demonstrate the production of mean flow shear and induced vortices.

  5. Computational Fluid Dynamics. [numerical methods and algorithm development

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This collection of papers was presented at the Computational Fluid Dynamics (CFD) Conference held at Ames Research Center in California on March 12 through 14, 1991. It is an overview of CFD activities at NASA Lewis Research Center. The main thrust of computational work at Lewis is aimed at propulsion systems. Specific issues related to propulsion CFD and associated modeling will also be presented. Examples of results obtained with the most recent algorithm development will also be presented.

  6. Least-squares finite element method for fluid dynamics

    NASA Technical Reports Server (NTRS)

    Jiang, Bo-Nan; Povinelli, Louis A.

    1989-01-01

    An overview is given of new developments of the least squares finite element method (LSFEM) in fluid dynamics. Special emphasis is placed on the universality of LSFEM; the symmetry and positiveness of the algebraic systems obtained from LSFEM; the accommodation of LSFEM to equal order interpolations for incompressible viscous flows; and the natural numerical dissipation of LSFEM for convective transport problems and high speed compressible flows. The performance of LSFEM is illustrated by numerical examples.

  7. Dynamics and electrorheology of sheared immiscible fluid mixtures.

    PubMed

    Sakaue, Takahiro; Shitara, Kyohei; Ohta, Takao

    2014-05-01

    We analyze the electrorheological effect in immiscible fluid mixtures with dielectric mismatch. By taking the electric field effect into account, which couples to the dynamics of domain morphology under flow, we propose a set of electrorheological constitutive equations valid under the condition where the relative magnitude of the flow field is stronger than that of the electric field. Through comparison with recent experiments, we point out a unique dynamical stress response inherent in situations where the cross-coupling between different fields is essential.

  8. A numerical model for dynamic crustal-scale fluid flow

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Fluid flow in the crust is often envisaged and modeled as continuous, yet minimal flow, which occurs over large geological times. This is a suitable approximation for flow as long as it is solely controlled by the matrix permeability of rocks, which in turn is controlled by viscous compaction of the pore space. However, strong evidence (hydrothermal veins and ore deposits) exists that a significant part of fluid flow in the crust occurs strongly localized in both space and time, controlled by the opening and sealing of hydrofractures. We developed, tested and applied a novel computer code, which considers this dynamic behavior and couples it with steady, Darcian flow controlled by the matrix permeability. In this dual-porosity model, fractures open depending on the fluid pressure relative to the solid pressure. Fractures form when matrix permeability is insufficient to accommodate fluid flow resulting from compaction, decompression (Staude et al. 2009) or metamorphic dehydration reactions (Weisheit et al. 2013). Open fractures can close when the contained fluid either seeps into the matrix or escapes by fracture propagation: mobile hydrofractures (Bons, 2001). In the model, closing and sealing of fractures is controlled by a time-dependent viscous law, which is based on the effective stress and on either Newtonian or non-Newtonian viscosity. Our simulations indicate that the bulk of crustal fluid flow in the middle to lower upper crust is intermittent, highly self-organized, and occurs as mobile hydrofractures. This is due to the low matrix porosity and permeability, combined with a low matrix viscosity and, hence, fast sealing of fractures. Stable fracture networks, generated by fluid overpressure, are restricted to the uppermost crust. Semi-stable fracture networks can develop in an intermediate zone, if a critical overpressure is reached. Flow rates in mobile hydrofractures exceed those in the matrix porosity and fracture networks by orders of magnitude

  9. Hypersonic Magneto-Fluid-Dynamic Compression in Cylindrical Inlet

    NASA Technical Reports Server (NTRS)

    Shang, Joseph S.; Chang, Chau-Lyan

    2007-01-01

    Hypersonic magneto-fluid-dynamic interaction has been successfully performed as a virtual leading-edge strake and a virtual cowl of a cylindrical inlet. In a side-by-side experimental and computational study, the magnitude of the induced compression was found to be depended on configuration and electrode placement. To better understand the interacting phenomenon the present investigation is focused on a direct current discharge at the leading edge of a cylindrical inlet for which validating experimental data is available. The present computational result is obtained by solving the magneto-fluid-dynamics equations at the low magnetic Reynolds number limit and using a nonequilibrium weakly ionized gas model based on the drift-diffusion theory. The numerical simulation provides a detailed description of the intriguing physics. After validation with experimental measurements, the computed results further quantify the effectiveness of a magnet-fluid-dynamic compression for a hypersonic cylindrical inlet. At a minuscule power input to a direct current surface discharge of 8.14 watts per square centimeter of electrode area produces an additional compression of 6.7 percent for a constant cross-section cylindrical inlet.

  10. Renewable fluid dynamic energy derived from aquatic animal locomotion.

    PubMed

    Dabiri, John O

    2007-09-01

    Aquatic animals swimming in isolation and in groups are known to extract energy from the vortices in environmental flows, significantly reducing muscle activity required for locomotion. A model for the vortex dynamics associated with this phenomenon is developed, showing that the energy extraction mechanism can be described by simple criteria governing the kinematics of the vortices relative to the body in the flow. In this way, we need not make direct appeal to the fluid dynamics, which can be more difficult to evaluate than the kinematics. Examples of these principles as exhibited in swimming fish and existing energy conversion devices are described. A benefit of the developed framework is that the potentially infinite-dimensional parameter space of the fluid-structure interaction is reduced to a maximum of eight combinations of three parameters. The model may potentially aid in the design and evaluation of unsteady aero- and hydrodynamic energy conversion systems that surpass the Betz efficiency limit of steady fluid dynamic energy conversion systems.

  11. Two-fluid cleaning technology for advanced photomask

    NASA Astrophysics Data System (ADS)

    Kikuchi, Tsutomu; Kobayashi, Nobuo; Kurokawa, Yoshiaki; Hirose, Harumichi; Nonaka, Mikio

    2009-04-01

    Along with the increased miniaturization of electronic devices, two-fluid cleaning technology is garnering the spotlight as a solution for the manufacturing process of Photomask. This is because it is now known that implementing energy control of the particles that are sprayed on the substrate allows cleaning of miniature patterns. However, it is not yet clear just how miniature of a pattern is cleanable with two-fluid cleaning technology. This study discusses mechanisms to miniaturize the droplets created by a two-fluid nozzle. In addition, this study also considers the impact of droplet size on pattern damage to the Photomask and speaks on the potential for applying two-fluid cleaning technology in the future.

  12. Study of critical dynamics in fluids via molecular dynamics in canonical ensemble.

    PubMed

    Roy, Sutapa; Das, Subir K

    2015-12-01

    With the objective of understanding the usefulness of thermostats in the study of dynamic critical phenomena in fluids, we present results for transport properties in a binary Lennard-Jones fluid that exhibits liquid-liquid phase transition. Various collective transport properties, calculated from the molecular dynamics (MD) simulations in canonical ensemble, with different thermostats, are compared with those obtained from MD simulations in microcanonical ensemble. It is observed that the Nosé-Hoover and dissipative particle dynamics thermostats are useful for the calculations of mutual diffusivity and shear viscosity. The Nosé-Hoover thermostat, however, as opposed to the latter, appears inadequate for the study of bulk viscosity. PMID:26687057

  13. Assessment of extracellular fluid volume and fluid status in hemodialysis patients: current status and technical advances.

    PubMed

    Dou, Yanna; Zhu, Fansan; Kotanko, Peter

    2012-07-01

    The assessment of extracellular fluid volume (ECV) and fluid status is both important and challenging in hemodialysis patients. Extracellular fluid is distributed in two major sub-compartments: interstitial fluid and plasma. A variety of methods are used to assess the ECV, with tracer dilution techniques considered gold standard. However, ECV defined as the distribution space of bromide, sodium, chloride, and ferrocyanide appears to be larger than the distribution volume of inulin and sucrose, suggesting a partial distribution into the intracellular volume. Relative blood volume monitoring, measurement of inferior vena cava diameter by ultrasound and biochemical markers are indirect methods, which do not reflect the ECV and fluid status accurately. Bioimpedance spectroscopy (BIS) techniques enable assessment of ECV and intracellular volume. Currently, BIS appears to be the most practical method for assessing ECV volume and fluid status in dialysis patients.

  14. Cytoskeletal Dynamics and Fluid Flow in Drosophila Oocytes

    NASA Astrophysics Data System (ADS)

    de Canio, Gabriele; Goldstein, Raymond; Lauga, Eric

    2015-11-01

    The biological world includes a broad range of phenomena in which transport in a fluid plays a central role. Among these is the fundamental issue of cell polarity arising during development, studied historically using the model organism Drosophila melanogaster. The polarity of the oocyte is known to be induced by the translocation of mRNAs by kinesin motor proteins along a dense microtubule cytoskeleton, a process which also induces cytoplasmic streaming. Recent experimental observations have revealed the remarkable fluid-structure interactions that occur as the streaming flows back-react on the microtubules. In this work we use a combination of theory and simulations to address the interplay between the fluid flow and the configuration of cytoskeletal filaments leading to the directed motion inside the oocyte. We show in particular that the mechanical coupling between the fluid motion and the orientation of the microtubules can lead to a transition to coherent motion within the oocyte, as observed. Supported by EPSRC and ERC Advanced Investigator Grant 247333.

  15. PREFACE: Complex dynamics of fluids in disordered and crowded environments Complex dynamics of fluids in disordered and crowded environments

    NASA Astrophysics Data System (ADS)

    Coslovich, Daniele; Kahl, Gerhard; Krakoviack, Vincent

    2011-06-01

    Over the past two decades, the dynamics of fluids under nanoscale confinement has attracted much attention. Motivation for this rapidly increasing interest is based on both practical and fundamental reasons. On the practical and rather applied side, problems in a wide range of scientific topics, such as polymer and colloidal sciences, rheology, geology, or biophysics, benefit from a profound understanding of the dynamical behaviour of confined fluids. Further, effects similar to those observed in confinement are expected in fluids whose constituents have strong size or mass asymmetry, and in biological systems where crowding and obstruction phenomena in the cytosol are responsible for clear separations of time scales for macromolecular transport in the cell. In fundamental research, on the other hand, the interest focuses on the complex interplay between confinement and structural relaxation, which is responsible for the emergence of new phenomena in the dynamics of the system: in confinement, geometric constraints associated with the pore shape are imposed to the adsorbed fluids and an additional characteristic length scale, i.e. the pore size, comes into play. For many years, the topic has been mostly experimentally driven. Indeed, a broad spectrum of systems has been investigated by sophisticated experimental techniques, while theoretical and simulation studies were rather scarce due to conceptual and computational issues. In the past few years, however, theory and simulations could largely catch up with experiments. On one side, new theories have been put forward that duly take into account the porosity, the connectivity, and the randomness of the confinement. On the other side, the ever increasing available computational power now allows investigations that were far out of reach a few years ago. Nowadays, instead of isolated state points, systematic investigations on the dynamics of confined fluids, covering a wide range of system parameters, can be realized

  16. Computational Fluid Dynamics Simulation of Dual Bell Nozzle Film Cooling

    NASA Technical Reports Server (NTRS)

    Braman, Kalen; Garcia, Christian; Ruf, Joseph; Bui, Trong

    2015-01-01

    Marshall Space Flight Center (MSFC) and Armstrong Flight Research Center (AFRC) are working together to advance the technology readiness level (TRL) of the dual bell nozzle concept. Dual bell nozzles are a form of altitude compensating nozzle that consists of two connecting bell contours. At low altitude the nozzle flows fully in the first, relatively lower area ratio, nozzle. The nozzle flow separates from the wall at the inflection point which joins the two bell contours. This relatively low expansion results in higher nozzle efficiency during the low altitude portion of the launch. As ambient pressure decreases with increasing altitude, the nozzle flow will expand to fill the relatively large area ratio second nozzle. The larger area ratio of the second bell enables higher Isp during the high altitude and vacuum portions of the launch. Despite a long history of theoretical consideration and promise towards improving rocket performance, dual bell nozzles have yet to be developed for practical use and have seen only limited testing. One barrier to use of dual bell nozzles is the lack of control over the nozzle flow transition from the first bell to the second bell during operation. A method that this team is pursuing to enhance the controllability of the nozzle flow transition is manipulation of the film coolant that is injected near the inflection between the two bell contours. Computational fluid dynamics (CFD) analysis is being run to assess the degree of control over nozzle flow transition generated via manipulation of the film injection. A cold flow dual bell nozzle, without film coolant, was tested over a range of simulated altitudes in 2004 in MSFC's nozzle test facility. Both NASA centers have performed a series of simulations of that dual bell to validate their computational models. Those CFD results are compared to the experimental results within this paper. MSFC then proceeded to add film injection to the CFD grid of the dual bell nozzle. A series of

  17. Computational Fluid Dynamic simulations of pipe elbow flow.

    SciTech Connect

    Homicz, Gregory Francis

    2004-08-01

    One problem facing today's nuclear power industry is flow-accelerated corrosion and erosion in pipe elbows. The Korean Atomic Energy Research Institute (KAERI) is performing experiments in their Flow-Accelerated Corrosion (FAC) test loop to better characterize these phenomena, and develop advanced sensor technologies for the condition monitoring of critical elbows on a continuous basis. In parallel with these experiments, Sandia National Laboratories is performing Computational Fluid Dynamic (CFD) simulations of the flow in one elbow of the FAC test loop. The simulations are being performed using the FLUENT commercial software developed and marketed by Fluent, Inc. The model geometry and mesh were created using the GAMBIT software, also from Fluent, Inc. This report documents the results of the simulations that have been made to date; baseline results employing the RNG k-e turbulence model are presented. The predicted value for the diametrical pressure coefficient is in reasonably good agreement with published correlations. Plots of the velocities, pressure field, wall shear stress, and turbulent kinetic energy adjacent to the wall are shown within the elbow section. Somewhat to our surprise, these indicate that the maximum values of both wall shear stress and turbulent kinetic energy occur near the elbow entrance, on the inner radius of the bend. Additional simulations were performed for the same conditions, but with the RNG k-e model replaced by either the standard k-{var_epsilon}, or the realizable k-{var_epsilon} turbulence model. The predictions using the standard k-{var_epsilon} model are quite similar to those obtained in the baseline simulation. However, with the realizable k-{var_epsilon} model, more significant differences are evident. The maximums in both wall shear stress and turbulent kinetic energy now appear on the outer radius, near the elbow exit, and are {approx}11% and 14% greater, respectively, than those predicted in the baseline calculation

  18. Dynamics of multicomponent vesicles in a viscous fluid

    SciTech Connect

    Sohn, Jin Sun Tseng, Y-H Li Shuwang Voigt, Axel Lowengrub, John S.

    2010-01-01

    We develop and investigate numerically a thermodynamically consistent model of two-dimensional multicomponent vesicles in an incompressible viscous fluid. The model is derived using an energy variation approach that accounts for different lipid surface phases, the excess energy (line energy) associated with surface phase domain boundaries, bending energy, spontaneous curvature, local inextensibility and fluid flow via the Stokes equations. The equations are high-order (fourth order) nonlinear and nonlocal due to incompressibility of the fluid and the local inextensibility of the vesicle membrane. To solve the equations numerically, we develop a nonstiff, pseudo-spectral boundary integral method that relies on an analysis of the equations at small scales. The algorithm is closely related to that developed very recently by Veerapaneni et al. [81] for homogeneous vesicles although we use a different and more efficient time stepping algorithm and a reformulation of the inextensibility equation. We present simulations of multicomponent vesicles in an initially quiescent fluid and investigate the effect of varying the average surface concentration of an initially unstable mixture of lipid phases. The phases then redistribute and alter the morphology of the vesicle and its dynamics. When an applied shear is introduced, an initially elliptical vesicle tank-treads and attains a steady shape and surface phase distribution. A sufficiently elongated vesicle tumbles and the presence of different surface phases with different bending stiffnesses and spontaneous curvatures yields a complex evolution of the vesicle morphology as the vesicle bends in regions where the bending stiffness and spontaneous curvature are small.

  19. The gas dynamics of fluids of high specific heat

    NASA Astrophysics Data System (ADS)

    Meier, Gerd E. A.; Mueller, E.-A.

    1987-12-01

    Effects in the gas dynamics of real fluids other than those in ideal substances are reviewed. Complete adiabatic liquefaction and evaporation are possible for substances whose specific heat exceeds a limit of 20 gas constants. These fluids, consisting of large molecules, have so much internal energy storage capacity in their vibrational degrees of freedom that the heat of evaporation can be supplied or also stored in the case of condensation. Thus liquefaction shock waves, which transform a gas completely or partly into a liquid, are possible. In compression waves and the expansion waves, wave bifurcations which are caused by the splitting of isentropes at the phase boundaries can be observed. In steady flow in nozzles and free jets, Mach number discontinuities arise because of phase transition. The discontinuities are not accompanied by a pressure jump and are characterized by a jump in the sound velocity of the fluid. This is part of the wave bifurcation, which means for steady flow a separation of the waves of different speeds at different locations of the flow nozzle or the jet. In the case of free jets of supersaturated fluids flowing out of a nozzle, the explosion-like disintegration of the jet by propagation of the evaporation wave in three dimensions and the extremely large jet angles are noted.

  20. Issues in computational fluid dynamics code verification and validation

    SciTech Connect

    Oberkampf, W.L.; Blottner, F.G.

    1997-09-01

    A broad range of mathematical modeling errors of fluid flow physics and numerical approximation errors are addressed in computational fluid dynamics (CFD). It is strongly believed that if CFD is to have a major impact on the design of engineering hardware and flight systems, the level of confidence in complex simulations must substantially improve. To better understand the present limitations of CFD simulations, a wide variety of physical modeling, discretization, and solution errors are identified and discussed. Here, discretization and solution errors refer to all errors caused by conversion of the original partial differential, or integral, conservation equations representing the physical process, to algebraic equations and their solution on a computer. The impact of boundary conditions on the solution of the partial differential equations and their discrete representation will also be discussed. Throughout the article, clear distinctions are made between the analytical mathematical models of fluid dynamics and the numerical models. Lax`s Equivalence Theorem and its frailties in practical CFD solutions are pointed out. Distinctions are also made between the existence and uniqueness of solutions to the partial differential equations as opposed to the discrete equations. Two techniques are briefly discussed for the detection and quantification of certain types of discretization and grid resolution errors.

  1. Development of a theoretical framework for analyzing cerebrospinal fluid dynamics

    PubMed Central

    Cohen, Benjamin; Voorhees, Abram; Vedel, Søren; Wei, Timothy

    2009-01-01

    Background To date hydrocephalus researchers acknowledge the need for rigorous but utilitarian fluid mechanics understanding and methodologies in studying normal and hydrocephalic intracranial dynamics. Pressure volume models and electric circuit analogs introduced pressure into volume conservation; but control volume analysis enforces independent conditions on pressure and volume. Previously, utilization of clinical measurements has been limited to understanding of the relative amplitude and timing of flow, volume and pressure waveforms; qualitative approaches without a clear framework for meaningful quantitative comparison. Methods Control volume analysis is presented to introduce the reader to the theoretical background of this foundational fluid mechanics technique for application to general control volumes. This approach is able to directly incorporate the diverse measurements obtained by clinicians to better elucidate intracranial dynamics and progression to disorder. Results Several examples of meaningful intracranial control volumes and the particular measurement sets needed for the analysis are discussed. Conclusion Control volume analysis provides a framework to guide the type and location of measurements and also a way to interpret the resulting data within a fundamental fluid physics analysis. PMID:19772652

  2. Computational fluid dynamics modeling of coal gasification in a pressurized spout-fluid bed

    SciTech Connect

    Zhongyi Deng; Rui Xiao; Baosheng Jin; He Huang; Laihong Shen; Qilei Song; Qianjun Li

    2008-05-15

    Computational fluid dynamics (CFD) modeling, which has recently proven to be an effective means of analysis and optimization of energy-conversion processes, has been extended to coal gasification in this paper. A 3D mathematical model has been developed to simulate the coal gasification process in a pressurized spout-fluid bed. This CFD model is composed of gas-solid hydrodynamics, coal pyrolysis, char gasification, and gas phase reaction submodels. The rates of heterogeneous reactions are determined by combining Arrhenius rate and diffusion rate. The homogeneous reactions of gas phase can be treated as secondary reactions. A comparison of the calculated and experimental data shows that most gasification performance parameters can be predicted accurately. This good agreement indicates that CFD modeling can be used for complex fluidized beds coal gasification processes. 37 refs., 7 figs., 5 tabs.

  3. Considerations of blood properties, outlet boundary conditions and energy loss approaches in computational fluid dynamics modeling.

    PubMed

    Moon, Ji Young; Suh, Dae Chul; Lee, Yong Sang; Kim, Young Woo; Lee, Joon Sang

    2014-02-01

    Despite recent development of computational fluid dynamics (CFD) research, analysis of computational fluid dynamics of cerebral vessels has several limitations. Although blood is a non-Newtonian fluid, velocity and pressure fields were computed under the assumptions of incompressible, laminar, steady-state flows and Newtonian fluid dynamics. The pulsatile nature of blood flow is not properly applied in inlet and outlet boundaries. Therefore, we present these technical limitations and discuss the possible solution by comparing the theoretical and computational studies. PMID:24642855

  4. Fluid-solid boundary conditions for multiparticle collision dynamics.

    PubMed

    Whitmer, Jonathan K; Luijten, Erik

    2010-03-17

    The simulation of colloidal particles suspended in solvent requires an accurate representation of the interactions between the colloids and the solvent molecules. Using the multiparticle collision dynamics method, we examine several proposals for stick boundary conditions, studying their properties in both plane Poiseuille flow (where fluid interacts with the boundary of a stationary macroscopic solid) and particle-based colloid simulations (where the boundaries are thermally affected and in motion). In addition, our simulations compare various collision rules designed to remove spurious slip near solid surfaces, and the effects of these rules on the thermal motion of colloidal particles. Furthermore, we demonstrate that stochastic reflection of the fluid at solid boundaries fails to faithfully represent stick boundary conditions, and conclude that bounce-back conditions should be applied at both mobile and stationary surfaces. Finally, we generalize these ideas to create partial slip boundary conditions at both stationary and mobile surfaces.

  5. 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.

  6. Conducting fluid dynamics experiments with vertically falling soap films

    NASA Astrophysics Data System (ADS)

    Rutgers, M. A.; Wu, X. L.; Daniel, W. B.

    2001-07-01

    This article gives a detailed description of an apparatus in which flowing soap films are used to perform two dimensional fluid dynamics experiments. We have previously reported scientific findings made with the apparatus, but never carefully described the technique, or its full potential. A brief introduction is given on the nature of soap films as fluids and then all the details necessary for creating robust flowing films are listed. Typical parameters for the system are: flow speeds from 0.5 to 4 m/s, film thickness between 1 and 10 μm, and typical film sizes are 3 m tall and 10 cm wide although films of 20 m tall and 4 m wide have also been made. A vacuum apparatus is also described in which the air drag on the film can be reduced by a factor of 5-10. Finally, a large number of techniques for measuring flow and thickness are outlined and referenced.

  7. Characterising the structure of photosynthetic biofilms using fluid dynamic gauging.

    PubMed

    Salley, B; Gordon, P W; McCormick, A J; Fisher, A C; Wilson, D I

    2012-01-01

    A new configuration of the fluid dynamic gauging technique for measuring soft layers on surfaces was used to monitor the growth of a cyanobacterium, Synechococcus sp. WH 5701, on stainless steel (SS), glass and an indium tin oxide (ITO) on a polyethylene terephthalate (PET) substratum. The biofilm thickness increased steadily over 4 weeks and exhibited noticeable changes in microstructure and strength. The biofilms all exhibited a two-layer structure, with a compact layer next to the substratum and a loose layer above. Biofilms on ITO or SS exhibited cohesive failure when removed by fluid shear whereas those on glass exhibited adhesive failure. The technique is able to elucidate various aspects of biofilm behaviour, as illustrated by the action of a biocide (NaOCl) on a mature biofilm. PMID:22329680

  8. 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.

  9. Quantum molecular dynamics simulations of thermophysical properties of fluid ethane

    NASA Astrophysics Data System (ADS)

    Zhang, Yujuan; Wang, Cong; Zheng, Fawei; Zhang, Ping

    2012-12-01

    We have performed first-principles molecular-dynamics simulations based on density-functional theory to study the thermophysical properties of ethane under extreme conditions. We present results for the equation of state of fluid ethane in the warm dense region. The optical conductivity is calculated via the Kubo-Greenwood formula from which the dc conductivity and optical reflectivity are derived. The close correlation between the nonmetal-metal transition of ethane and its decomposition, that ethane dissociates significantly into molecular and/or atomic hydrogen and some long alkane chains, has been systematically studied by analyzing the optical conductivity spectra, pair correlation functions, electronic density of states, and charge density distribution of fluid ethane.

  10. Emergent geometries and nonlinear-wave dynamics in photon fluids.

    PubMed

    Marino, F; Maitland, C; Vocke, D; Ortolan, A; Faccio, D

    2016-03-22

    Nonlinear waves in defocusing media are investigated in the framework of the hydrodynamic description of light as a photon fluid. The observations are interpreted in terms of an emergent curved spacetime generated by the waves themselves, which fully determines their dynamics. The spacetime geometry emerges naturally as a result of the nonlinear interaction between the waves and the self-induced background flow. In particular, as observed in real fluids, different points of the wave profile propagate at different velocities leading to the self-steepening of the wave front and to the formation of a shock. This phenomenon can be associated to a curvature singularity of the emergent metric. Our analysis offers an alternative insight into the problem of shock formation and provides a demonstration of an analogue gravity model that goes beyond the kinematic level.

  11. 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 capabilties 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.

  12. 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.

  13. Distributed interactive graphics applications in computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Rogers, Stuart E.; Buning, Pieter G.; Merritt, Fergus J.

    1988-01-01

    Implementation of two interactive, distributed graphics programs used in Computational Fluid Dynamics is discussed. Both programs run on a Cray 2 supercomputer and use a Silicon Graphics Iris workstation as the graphics front-end machine. The hardware and supporting software is from the Numerical Aerodynamic Simulation project. Using this configuration, the supercomputer does all of the numerically intensive work and the workstation allows the user to perform real-time interactive transformations on the displayed data. The first program was written originally as a distributed program which computes particle traces for fluid flow solutions existing on the supercomputer. The second is an older post-processing and plotting program which was modified to run in a distributed mode. Both programs have realized a large increase in capability as a distributed process. Some graphical results are presented.

  14. Computational Fluid Dynamics at NASA Ames Research Center

    NASA Technical Reports Server (NTRS)

    Kutler, Paul

    1994-01-01

    Computational fluid dynamics (CFD) is beginning to play a major role in the aircraft industry of the United States because of the realization that CFD can be a new and effective design tool and thus could provide a company with a competitive advantage. It is also playing a significant role in research institutions, both governmental and academic, as a tool for researching new fluid physics, as well as supplementing and complementing experimental testing. In this presentation, some of the progress made to date in CFD at NASA Ames will be reviewed. The presentation addresses the status of CFD in terms of methods, examples of CFD solutions, and computer technology. In addition, the role CFD will play in supporting the revolutionary goals set forth by the Aeronautical Policy Review Committee established by the Office of Science and Technology Policy is noted. The need for validated CFD tools is also briefly discussed.

  15. 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.

  16. Emergent geometries and nonlinear-wave dynamics in photon fluids

    PubMed Central

    Marino, F.; Maitland, C.; Vocke, D.; Ortolan, A.; Faccio, D.

    2016-01-01

    Nonlinear waves in defocusing media are investigated in the framework of the hydrodynamic description of light as a photon fluid. The observations are interpreted in terms of an emergent curved spacetime generated by the waves themselves, which fully determines their dynamics. The spacetime geometry emerges naturally as a result of the nonlinear interaction between the waves and the self-induced background flow. In particular, as observed in real fluids, different points of the wave profile propagate at different velocities leading to the self-steepening of the wave front and to the formation of a shock. This phenomenon can be associated to a curvature singularity of the emergent metric. Our analysis offers an alternative insight into the problem of shock formation and provides a demonstration of an analogue gravity model that goes beyond the kinematic level. PMID:27001128

  17. Emergent geometries and nonlinear-wave dynamics in photon fluids.

    PubMed

    Marino, F; Maitland, C; Vocke, D; Ortolan, A; Faccio, D

    2016-01-01

    Nonlinear waves in defocusing media are investigated in the framework of the hydrodynamic description of light as a photon fluid. The observations are interpreted in terms of an emergent curved spacetime generated by the waves themselves, which fully determines their dynamics. The spacetime geometry emerges naturally as a result of the nonlinear interaction between the waves and the self-induced background flow. In particular, as observed in real fluids, different points of the wave profile propagate at different velocities leading to the self-steepening of the wave front and to the formation of a shock. This phenomenon can be associated to a curvature singularity of the emergent metric. Our analysis offers an alternative insight into the problem of shock formation and provides a demonstration of an analogue gravity model that goes beyond the kinematic level. PMID:27001128

  18. PREFACE: FLUIDOS 2010: XI Meeting on Recent Advances in the Physics of Fluids and their Applications

    NASA Astrophysics Data System (ADS)

    Bove, Italo; Cabeza, Cecilia; Martí, Arturo C.; Sarasúa, Gustavo

    2011-04-01

    The papers published in this volume of the Journal of Physics: Conference Series were selected from the manuscripts submitted to the XI Meeting on Recent Advances in the Physics of Fluids and their Applications (FLUIDOS2010), which was held in Colonia del Sacramento, Uruguay, 3-5 November 2010. FLUIDOS takes place every two years, usually in November, with the aim of gathering together researchers from all areas of the Physics of Fluids, to update themselves on the latest technical developments and applications, share knowledge and stimulate new ideas. This 11th meeting continues the successful experience of the previous ones which were held in different Argentinian cities. For the first time, the meeting was celebrated in Uruguay, more specifically, in the peaceful town of Colonia del Sacramento, designated a World Heritage Site by UNESCO. The conference presented an outstanding program of papers covering the most recent advances in Physics of Fluids in the following areas: General Fluid Dynamics General and non-Newtonian Flows Magnetohydrodynamics Electrohydrodynamics and Plasmas Hydraulics, Thermohydraulics and Multiple Phase Flows A website with full details of the conference program, abstracts and other information can be found at http://fluidos2010.fisica.edu.uy. We would like to thank all the participants, especially those who contributed with talks, posters and manuscripts, for making FLUDOS2010 such a successful conference. Our thanks also go to our colleagues for their support and encouragement, particularly in the refereeing of papers. We would like to acknowledge additional financial support from Comisión Sectorial de Investigación Científica (Universidad de la República, Uruguay), Programa de Desarrollo de las Ciencias Básicas (Uruguay) and the Centro Latinoamericano de Física (CLAF). Our thanks are extended to the local government of Colonia del Sacramento. The next FLUIDOS conference will be held in November 2013, in Buenos Aires, Argentina. We

  19. Integration of Virtual Reality with Computational Fluid Dynamics for Process Optimization

    NASA Astrophysics Data System (ADS)

    Wu, B.; Chen, G. H.; Fu, D.; Moreland, John; Zhou, Chenn Q.

    2010-03-01

    Computational Fluid Dynamics (CFD) has become a powerful simulation technology used in many industrial applications for process design and optimization to save energy, improve environment, and reduce costs. In order to better understand CFD results and more easily communicate with non-CFD experts, advanced virtual reality (VR) visualization is desired for CFD post-processing. Efforts have recently been made at Purdue University Calumet to integrate VR with CFD to visualize complex data in three dimensions in an interactive, virtual environment. The virtual engineering environment greatly enhances the value of CFD simulations and allows engineers to gain much needed process insights for the design and optimization of industrial processes.

  20. Computational fluid dynamics in ventilation. 4: Commercial application of CFD in ventilation

    NASA Astrophysics Data System (ADS)

    Nielsen, Peter V.

    In considering the commercial applications of Computational Fluid Dynamics (CFD) in ventilation, the following are addressed: typical markets (airport centers, large theaters, atria, shopping malls, etc.); typical problems to be solved (energy flow, draft, ventilation effectiveness, pressure distribution, etc.); and high priority areas, activities and quantities (fast preprocessing, effective visualization software, etc.). It is stated that the commercial application of CFD may be looked upon as an advanced 'zonal' model. The 'zonal' model concept is outlined and CFD with large control volumes is considered. An illustrated example of air flow simulation in a theater is given.

  1. Fluid dynamics of ventricular filling in the embryonic heart.

    PubMed

    Miller, Laura A

    2011-09-01

    The vertebrate embryonic heart first forms as a valveless tube that pumps blood using waves of contraction. As the heart develops, the atrium and ventricle bulge out from the heart tube, and valves begin to form through the expansion of the endocardial cushions. As a result of changes in geometry, conduction velocities, and material properties of the heart wall, the fluid dynamics and resulting spatial patterns of shear stress and transmural pressure change dramatically. Recent work suggests that these transitions are significant because fluid forces acting on the cardiac walls, as well as the activity of myocardial cells that drive the flow, are necessary for correct chamber and valve morphogenesis. In this article, computational fluid dynamics was used to explore how spatial distributions of the normal forces acting on the heart wall change as the endocardial cushions grow and as the cardiac wall increases in stiffness. The immersed boundary method was used to simulate the fluid-moving boundary problem of the cardiac wall driving the motion of the blood in a simplified model of a two-dimensional heart. The normal forces acting on the heart walls increased during the period of one atrial contraction because inertial forces are negligible and the ventricular walls must be stretched during filling. Furthermore, the force required to fill the ventricle increased as the stiffness of the ventricular wall was increased. Increased endocardial cushion height also drastically increased the force necessary to contract the ventricle. Finally, flow in the moving boundary model was compared to flow through immobile rigid chambers, and the forces acting normal to the walls were substantially different. PMID:21336589

  2. The stochastic dynamics of tethered microcantilevers in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Robbins, Brian A.; Radiom, Milad; Ducker, William A.; Walz, John Y.; Paul, Mark R.

    2014-10-01

    We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.

  3. The stochastic dynamics of tethered microcantilevers in a viscous fluid

    SciTech Connect

    Robbins, Brian A.; Paul, Mark R.; Radiom, Milad; Ducker, William A.; Walz, John Y.

    2014-10-28

    We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.

  4. PREFACE: Complex dynamics of fluids in disordered and crowded environments Complex dynamics of fluids in disordered and crowded environments

    NASA Astrophysics Data System (ADS)

    Coslovich, Daniele; Kahl, Gerhard; Krakoviack, Vincent

    2011-06-01

    Over the past two decades, the dynamics of fluids under nanoscale confinement has attracted much attention. Motivation for this rapidly increasing interest is based on both practical and fundamental reasons. On the practical and rather applied side, problems in a wide range of scientific topics, such as polymer and colloidal sciences, rheology, geology, or biophysics, benefit from a profound understanding of the dynamical behaviour of confined fluids. Further, effects similar to those observed in confinement are expected in fluids whose constituents have strong size or mass asymmetry, and in biological systems where crowding and obstruction phenomena in the cytosol are responsible for clear separations of time scales for macromolecular transport in the cell. In fundamental research, on the other hand, the interest focuses on the complex interplay between confinement and structural relaxation, which is responsible for the emergence of new phenomena in the dynamics of the system: in confinement, geometric constraints associated with the pore shape are imposed to the adsorbed fluids and an additional characteristic length scale, i.e. the pore size, comes into play. For many years, the topic has been mostly experimentally driven. Indeed, a broad spectrum of systems has been investigated by sophisticated experimental techniques, while theoretical and simulation studies were rather scarce due to conceptual and computational issues. In the past few years, however, theory and simulations could largely catch up with experiments. On one side, new theories have been put forward that duly take into account the porosity, the connectivity, and the randomness of the confinement. On the other side, the ever increasing available computational power now allows investigations that were far out of reach a few years ago. Nowadays, instead of isolated state points, systematic investigations on the dynamics of confined fluids, covering a wide range of system parameters, can be realized

  5. Fluid dynamics and noise emission associated with supersonic jets

    NASA Technical Reports Server (NTRS)

    Seiner, John M.

    1992-01-01

    Methods have long been sought to find an efficient means for reduction of jet noise using either active or passive turbulence control measures. Progress in this area is limited by unclear understanding of the physical supersonic jet noise source mechanisms as they relate to the jet plume turbulence structure. These mechanisms have been extensively studied using round jets. This paper shows that jets with nonround jet exit geometry can provide beneficial noise reduction relative to round jets. Both the fluid dynamic structure and noise of several nonround jets are examined in the paper.

  6. Multitasking the code ARC3D. [for computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Barton, John T.; Hsiung, Christopher C.

    1986-01-01

    The CRAY multitasking system was developed in order to utilize all four processors and sharply reduce the wall clock run time. This paper describes the techniques used to modify the computational fluid dynamics code ARC3D for this run and analyzes the achieved speedup. The ARC3D code solves either the Euler or thin-layer N-S equations using an implicit approximate factorization scheme. Results indicate that multitask processing can be used to achieve wall clock speedup factors of over three times, depending on the nature of the program code being used. Multitasking appears to be particularly advantageous for large-memory problems running on multiple CPU computers.

  7. Application of Krylov exponential propagation to fluid dynamics equations

    NASA Technical Reports Server (NTRS)

    Saad, Y.; Semeraro, B. D.

    1991-01-01

    This paper presents an application of matrix exponentiation via Krylov subspace projection, to the solution of fluid dynamics problems. The main idea is to approximate the operation exp(A)v by means of a projection-like process onto a Krylov subspace. This results in a computation of an exponential matrix vector product similar to the one above but of a much smaller size. Time integration schemes can then be devised to exploit this basic computational kernel. The motivation of this approach is to provide time-integration schemes that are essentially of an explicit nature but which have good stability properties.

  8. Application of Krylov exponential propagation to fluid dynamics equations

    NASA Technical Reports Server (NTRS)

    Saad, Youcef; Semeraro, David

    1991-01-01

    An application of matrix exponentiation via Krylov subspace projection to the solution of fluid dynamics problems is presented. The main idea is to approximate the operation exp(A)v by means of a projection-like process onto a krylov subspace. This results in a computation of an exponential matrix vector product similar to the one above but of a much smaller size. Time integration schemes can then be devised to exploit this basic computational kernel. The motivation of this approach is to provide time-integration schemes that are essentially of an explicit nature but which have good stability properties.

  9. New Challenges in Visualization of Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Gerald-Yamasaki, Michael; Chancellor, Marisa K. (Technical Monitor)

    1997-01-01

    The development of visualization systems for analyzing computational fluid dynamics data has been driven by increasing size and complexity of the data. New extensions to the system domain into analysis of data from multiple sources, parameter space studies, and multidisciplinary studies in support of integrated aeronautical design systems provide new g challenges for the visualization system developer. Recent work at NASA Ames Research Center in visualization systems, automatic flow feature detection, unsteady flow visualization techniques, and a new area, data exploitation, will be discussed in the context of NASA information technology initiatives.

  10. Executive Summary: Special Section on Credible Computational Fluid Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Mehta, Unmeel B.

    1998-01-01

    This summary presents the motivation for the Special Section on the credibility of computational fluid dynamics (CFD) simulations, its objective, its background and context, its content, and its major conclusions. Verification and validation (V&V) are the processes for establishing the credibility of CFD simulations. Validation assesses whether correct things are performed and verification assesses whether they are performed correctly. Various aspects of V&V are discussed. Progress is made in verification of simulation models. Considerable effort is still needed for developing a systematic validation method that can assess the credibility of simulated reality.

  11. 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.

  12. 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.

  13. Continuing Validation of Computational Fluid Dynamics for Supersonic Retropropulsion

    NASA Technical Reports Server (NTRS)

    Schauerhamer, Daniel Guy; Trumble, Kerry A.; Kleb, Bil; Carlson, Jan-Renee; Edquist, Karl T.

    2011-01-01

    A large step in the validation of Computational Fluid Dynamics (CFD) for Supersonic Retropropulsion (SRP) is shown through the comparison of three Navier-Stokes solvers (DPLR, FUN3D, and OVERFLOW) and wind tunnel test results. The test was designed specifically for CFD validation and was conducted in the Langley supersonic 4 x4 Unitary Plan Wind Tunnel and includes variations in the number of nozzles, Mach and Reynolds numbers, thrust coefficient, and angles of orientation. Code-to-code and code-to-test comparisons are encouraging and possible error sources are discussed.

  14. Fluid dynamics on ultrastatic spacetimes and dual black holes

    NASA Astrophysics Data System (ADS)

    Klemm, Dietmar; Maiorana, Andrea

    2014-07-01

    We show that the classification of shearless and incompressible stationary fluid flows on ultrastatic manifolds is equivalent to classifying the isometries of the spatial sections (Σ, ). For a flow on the closed Einstein static universe ℝ × S2 this leaves only one possibility, since on the 2-sphere all Killing fields are conjugate to each other, and it is well-known that the gravity dual of such a (conformal) fluid is the spherical Kerr- Newman-AdS4 black hole. On the other hand, in the open Einstein static universe ℝ × H2 the situation is more complicated, since the isometry group SL(2, ℝ) of H2 admits elliptic, parabolic and hyperbolic elements. One might thus ask what the gravity duals of the flows corresponding to these three different cases are. Answering this question is one of the scopes of this paper. In particular we identify the black hole dual to a fluid that is purely translating on the hyperbolic plane. Although this lies within the Carter-Plebanski class, it has never been studied in the literature before, and represents thus in principle a new black hole solution in AdS4. For a rigidly rotating fluid in ℝ × H2 (holographically dual to the hyperbolic KNAdS4 solution), there is a certain radius where the velocity reaches the speed of light, and thus the fluid can cover only the region within this radius. Quite remarkably, it turns out that the boundary of the hyperbolic KNAdS4 black hole is conformal to exactly that part of ℝ × H2 in which the fluid velocity does not exceed the speed of light. Thus, the correspondence between AdS gravity and hydrodynamics automatically eliminates the unphysical region. We extend these results to establish a precise mapping between possible flows on ultrastatic spacetimes (with constant curvature spatial sections) and the parameter space of the Carter-Plebanski solution to Einstein-Maxwell-AdS gravity. Finally, we show that the alternative description of the hyperbolic KNAdS4 black hole in terms of fluid

  15. Computational Fluid Dynamics Simulation of Fluidized Bed Polymerization Reactors

    SciTech Connect

    Fan, Rong

    2006-01-01

    Fluidized beds (FB) reactors are widely used in the polymerization industry due to their superior heat- and mass-transfer characteristics. Nevertheless, problems associated with local overheating of polymer particles and excessive agglomeration leading to FB reactors defluidization still persist and limit the range of operating temperatures that can be safely achieved in plant-scale reactors. Many people have been worked on the modeling of FB polymerization reactors, and quite a few models are available in the open literature, such as the well-mixed model developed by McAuley, Talbot, and Harris (1994), the constant bubble size model (Choi and Ray, 1985) and the heterogeneous three phase model (Fernandes and Lona, 2002). Most these research works focus on the kinetic aspects, but from industrial viewpoint, the behavior of FB reactors should be modeled by considering the particle and fluid dynamics in the reactor. Computational fluid dynamics (CFD) is a powerful tool for understanding the effect of fluid dynamics on chemical reactor performance. For single-phase flows, CFD models for turbulent reacting flows are now well understood and routinely applied to investigate complex flows with detailed chemistry. For multiphase flows, the state-of-the-art in CFD models is changing rapidly and it is now possible to predict reasonably well the flow characteristics of gas-solid FB reactors with mono-dispersed, non-cohesive solids. This thesis is organized into seven chapters. In Chapter 2, an overview of fluidized bed polymerization reactors is given, and a simplified two-site kinetic mechanism are discussed. Some basic theories used in our work are given in detail in Chapter 3. First, the governing equations and other constitutive equations for the multi-fluid model are summarized, and the kinetic theory for describing the solid stress tensor is discussed. The detailed derivation of DQMOM for the population balance equation is given as the second section. In this section

  16. Polymer dynamics and fluid flow in microfabricated devices

    NASA Astrophysics Data System (ADS)

    Bakajin, Olgica B.; Brody, James P.; Chou, Jeff; Chan, Shirley S.; Duke, Thomas A. J.; Knight, James; Sohn, Lydia L.; Vishwanath, Ashvin; Austin, Robert H.; Cox, E. C.

    1998-03-01

    We will discuss two recent directions of our work: (1) The influence of submicron length scales on polymer dynamics, (2) Ultra-rapid mixing via sub-micron hydrodynamic focusing. (1) Polymer dynamics at sub-micron length scales. We have explored the changes in the dynamics of long polymers as the thickness of the quasi-2 dimensional space is varied from 0.09 microns to 10 microns. We will show how the thickness of this space, scaled with the persistence length of the polymer, changes the dynamics of the polymer. The consequences of this qualitative change in polymer dynamics is quite important, since it controls the elongation of the polymer at a given force field and hence the ability of he array to fractionate the polymer. (2) Mixing at the sub- micron length scale cannot be tubulent but only diffusive in nature. We will show how it is possible using hydrodynamics to produce liquid jets of width under 20 nanometers which can mix fluids in under 1 microsecond times.

  17. Phase portrait methods for verifying fluid dynamic simulations

    SciTech Connect

    Stewart, H.B.

    1989-01-01

    As computing resources become more powerful and accessible, engineers more frequently face the difficult and challenging engineering problem of accurately simulating nonlinear dynamic phenomena. Although mathematical models are usually available, in the form of initial value problems for differential equations, the behavior of the solutions of nonlinear models is often poorly understood. A notable example is fluid dynamics: while the Navier-Stokes equations are believed to correctly describe turbulent flow, no exact mathematical solution of these equations in the turbulent regime is known. Differential equations can of course be solved numerically, but how are we to assess numerical solutions of complex phenomena without some understanding of the mathematical problem and its solutions to guide us

  18. Application of Control Volume Analysis to Cerebrospinal Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Wei, Timothy; Cohen, Benjamin; Anor, Tomer; Madsen, Joseph

    2011-11-01

    Hydrocephalus is among the most common birth defects and may not be prevented nor cured. Afflicted individuals face serious issues, which at present are too complicated and not well enough understood to treat via systematic therapies. This talk outlines the framework and application of a control volume methodology to clinical Phase Contrast MRI data. Specifically, integral control volume analysis utilizes a fundamental, fluid dynamics methodology to quantify intracranial dynamics within a precise, direct, and physically meaningful framework. A chronically shunted, hydrocephalic patient in need of a revision procedure was used as an in vivo case study. Magnetic resonance velocity measurements within the patient's aqueduct were obtained in four biomedical state and were analyzed using the methods presented in this dissertation. Pressure force estimates were obtained, showing distinct differences in amplitude, phase, and waveform shape for different intracranial states within the same individual. Thoughts on the physiological and diagnostic research and development implications/opportunities will be presented.

  19. Computational Fluid Dynamics Analysis of Canadian Supercritical Water Reactor (SCWR)

    NASA Astrophysics Data System (ADS)

    Movassat, Mohammad; Bailey, Joanne; Yetisir, Metin

    2015-11-01

    A Computational Fluid Dynamics (CFD) simulation was performed on the proposed design for the Canadian SuperCritical Water Reactor (SCWR). The proposed Canadian SCWR is a 1200 MW(e) supercritical light-water cooled nuclear reactor with pressurized fuel channels. The reactor concept uses an inlet plenum that all fuel channels are attached to and an outlet header nested inside the inlet plenum. The coolant enters the inlet plenum at 350 C and exits the outlet header at 625 C. The operating pressure is approximately 26 MPa. The high pressure and high temperature outlet conditions result in a higher electric conversion efficiency as compared to existing light water reactors. In this work, CFD simulations were performed to model fluid flow and heat transfer in the inlet plenum, outlet header, and various parts of the fuel assembly. The ANSYS Fluent solver was used for simulations. Results showed that mass flow rate distribution in fuel channels varies radially and the inner channels achieve higher outlet temperatures. At the outlet header, zones with rotational flow were formed as the fluid from 336 fuel channels merged. Results also suggested that insulation of the outlet header should be considered to reduce the thermal stresses caused by the large temperature gradients.

  20. The Dynamics of Miscible Fluids: A Space Flight Experiment (MIDAS)

    NASA Technical Reports Server (NTRS)

    Maxworthy, T.; Meiburg, E.; Balasubramaniam, R.; Rashidnia, N.; Lauver, R.

    2001-01-01

    We propose a space flight experiment to study the dynamics of miscible interfaces. A less viscous fluid displaces one of higher viscosity within a tube. The two fluids are miscible in all proportions. An intruding "finger" forms that occupies a fraction of the tube. As time progresses diffusion at the interface combined with flow induced straining between the two fluids modifies the concentration and velocity distributions within the whole tube. Also, under such circumstances it has been proposed that the interfacial stresses could depend on the local concentration gradients (Korteweg stresses) and that the divergence of the velocity need not be zero, even though the flow is incompressible. We have obtained reasonable agreement for the tip velocity between numerical simulations (that ignored the Korteweg stress and divergence effects) and physical experiments only at high Peelet Numbers. However at moderate to low Pe agreement was poor. As one possibility we attributed this lack of agreement to the disregard of these effects. We propose a space experiment to measure the finger shape, tip velocity, and the velocity and concentration fields. From intercomparisons between the experiment and the calculations we can then extract values for the coefficients of the Korteweg stress terms and confirm or deny the importance of these stresses.

  1. The Dynamics of Miscible Fluids: A Space Flight Experiment (MIDAS)

    NASA Technical Reports Server (NTRS)

    Maxworthy, T.; Meiburg, E.; Balasubramaniam, R.; Rashidnia, N.; Lauver, R.

    2001-01-01

    We propose a space flight experiment to study the dynamics of miscible interfaces. A less viscous fluid displaces one of higher viscosity within a tube. The two fluids are miscible in all proportions. An intruding "finger" forms that occupies a fraction of the tube. As time progresses diffusion at the interface combined with flow induced straining between the two fluids modifies the concentration and velocity distributions within the whole tube. Also, under such circumstances it has been proposed that the interfacial stresses could depend on the local concentration gradients (Korteweg stresses) and that the divergence of the velocity need not be zero, even though the flow is incompressible. We have obtained reasonable agreement for the tip velocity between numerical simulations (that ignored the Korteweg stress and divergence effects) and physical experiments only at high Peclet Numbers. However at moderate to low Pe agreement was poor. As one possibility we attributed this lack of agreement to the disregard of these effects. We propose a space experiment to measure the finger shape, tip velocity, and the velocity and concentration fields. From intercomparisons between the experiment and the calculations we can then extract values for the coefficients of the Korteweg stress terms and confirm or deny the importance of these stresses.

  2. Relativistic Fluid Dynamics: Physics for Many Different Scales

    NASA Astrophysics Data System (ADS)

    Andersson, Nils; Comer, Gregory L.

    2007-01-01

    The relativistic fluid is a highly successful model used to describe the dynamics of many-particle, relativistic systems. It takes as input basic physics from microscopic scales and yields as output predictions of bulk, macroscopic motion. By inverting the process, an understanding of bulk features can lead to insight into physics on the microscopic scale. Relativistic fluids have been used to model systems as ``small'' as heavy ions in collisions, and as large as the Universe itself, with ``intermediate'' sized objects like neutron stars being considered along the way. The purpose of this review is to discuss the mathematical and theoretical physics underpinnings of the relativistic (multiple) fluid model. We focus on the variational principle approach championed by Brandon Carter and his collaborators, in which a crucial element is to distinguish the momenta that are conjugate to the particle number density currents. This approach differs from the ``standard'' text-book! derivation of the equations of motion from the divergence of the stress-energy tensor in that one explicitly obtains the relativistic Euler equation as an ``integrability'' condition on the relativistic vorticity. We discuss the conservation laws and the equations of motion in detail, and provide a number of (in our opinion) interesting and relevant applications of the general theory.

  3. State-of-the-art review of computational fluid dynamics modeling for fluid-solids systems

    NASA Astrophysics Data System (ADS)

    Lyczkowski, R. W.; Bouillard, J. X.; Ding, J.; Chang, S. L.; Burge, S. W.

    1994-05-01

    As the result of 15 years of research (50 staff years of effort) Argonne National Laboratory (ANL), through its involvement in fluidized-bed combustion, magnetohydrodynamics, and a variety of environmental programs, has produced extensive computational fluid dynamics (CFD) software and models to predict the multiphase hydrodynamic and reactive behavior of fluid-solids motions and interactions in complex fluidized-bed reactors (FBR's) and slurry systems. This has resulted in the FLUFIX, IRF, and SLUFIX computer programs. These programs are based on fluid-solids hydrodynamic models and can predict information important to the designer of atmospheric or pressurized bubbling and circulating FBR, fluid catalytic cracking (FCC) and slurry units to guarantee optimum efficiency with minimum release of pollutants into the environment. This latter issue will become of paramount importance with the enactment of the Clean Air Act Amendment (CAAA) of 1995. Solids motion is also the key to understanding erosion processes. Erosion rates in FBR's and pneumatic and slurry components are computed by ANL's EROSION code to predict the potential metal wastage of FBR walls, intervals, feed distributors, and cyclones. Only the FLUFIX and IRF codes will be reviewed in the paper together with highlights of the validations because of length limitations. It is envisioned that one day, these codes with user-friendly pre- and post-processor software and tailored for massively parallel multiprocessor shared memory computational platforms will be used by industry and researchers to assist in reducing and/or eliminating the environmental and economic barriers which limit full consideration of coal, shale, and biomass as energy sources; to retain energy security; and to remediate waste and ecological problems.

  4. State-of-the-art review of computational fluid dynamics modeling for fluid-solids systems

    SciTech Connect

    Lyczkowski, R.W.; Bouillard, J.X.; Ding, J.; Chang, S.L.; Burge, S.W.

    1994-05-12

    As the result of 15 years of research (50 staff years of effort) Argonne National Laboratory (ANL), through its involvement in fluidized-bed combustion, magnetohydrodynamics, and a variety of environmental programs, has produced extensive computational fluid dynamics (CFD) software and models to predict the multiphase hydrodynamic and reactive behavior of fluid-solids motions and interactions in complex fluidized-bed reactors (FBRS) and slurry systems. This has resulted in the FLUFIX, IRF, and SLUFIX computer programs. These programs are based on fluid-solids hydrodynamic models and can predict information important to the designer of atmospheric or pressurized bubbling and circulating FBR, fluid catalytic cracking (FCC) and slurry units to guarantee optimum efficiency with minimum release of pollutants into the environment. This latter issue will become of paramount importance with the enactment of the Clean Air Act Amendment (CAAA) of 1995. Solids motion is also the key to understanding erosion processes. Erosion rates in FBRs and pneumatic and slurry components are computed by ANL`s EROSION code to predict the potential metal wastage of FBR walls, intervals, feed distributors, and cyclones. Only the FLUFIX and IRF codes will be reviewed in the paper together with highlights of the validations because of length limitations. It is envisioned that one day, these codes with user-friendly pre and post-processor software and tailored for massively parallel multiprocessor shared memory computational platforms will be used by industry and researchers to assist in reducing and/or eliminating the environmental and economic barriers which limit full consideration of coal, shale and biomass as energy sources, to retain energy security, and to remediate waste and ecological problems.

  5. Fluid dynamics in airway bifurcations: I. Primary flows.

    PubMed

    Martonen, T B; Guan, X; Schreck, R M

    2001-04-01

    The subject of fluid dynamics within human airways is of great importance for the risk assessment of air pollutants (inhalation toxicology) and the targeted delivery of inhaled pharmacologic drugs (aerosol therapy). As cited herein, experimental investigations of flow patterns have been performed on airway models and casts by a number of investigators. We have simulated flow patterns in human lung bifurcations and compared the results with the experimental data of Schreck (1972). The theoretical analyses were performed using a third-party software package, FIDAP, on the Cray T90 supercomputer. This effort is part of a systematic investigation where the effects of inlet conditions, Reynolds numbers, and dimensions and orientations of airways were addressed. This article focuses on primary flows using convective motion and isovelocity contour formats to describe fluid dynamics; subsequent articles in this issue consider secondary currents (Part II) and localized conditions (Part III). The agreement between calculated and measured results, for laminar flows with either parabolic or blunt inlet conditions to the bifurcations, was very good. To our knowledge, this work is the first to present such detailed comparisons of theoretical and experimental flow patterns in airway bifurcations. The agreement suggests that the methodologies can be employed to study factors affecting airflow patterns and particle behavior in human lungs.

  6. Some anticipated contributions to core fluid dynamics from the GRM

    NASA Technical Reports Server (NTRS)

    Vanvorhies, C.

    1985-01-01

    It is broadly maintained that the secular variation (SV) of the large scale geomagnetic field contains information on the fluid dynamics of Earth's electrically conducting outer core. The electromagnetic theory appropriate to a simple Earth model has recently been combined with reduced geomagnetic data in order to extract some of this information and ascertain its significance. The simple Earth model consists of a rigid, electrically insulating mantle surrounding a spherical, inviscid, and perfectly conducting liquid outer core. This model was tested against seismology by using truncated spherical harmonic models of the observed geomagnetic field to locate Earth's core-mantle boundary, CMB. Further electromagnetic theory has been developed and applied to the problem of estimating the horizontal fluid motion just beneath CMB. Of particular geophysical interest are the hypotheses that these motions: (1) include appreciable surface divergence indicative of vertical motion at depth, and (2) are steady for time intervals of a decade or more. In addition to the extended testing of the basic Earth model, the proposed GRM provides a unique opportunity to test these dynamical hypotheses.

  7. Applying uncertainty quantification to multiphase flow computational fluid dynamics

    SciTech Connect

    Gel, A; Garg, R; Tong, C; Shahnam, M; Guenther, C

    2013-07-01

    Multiphase computational fluid dynamics plays a major role in design and optimization of fossil fuel based reactors. There is a growing interest in accounting for the influence of uncertainties associated with physical systems to increase the reliability of computational simulation based engineering analysis. The U.S. Department of Energy's National Energy Technology Laboratory (NETL) has recently undertaken an initiative to characterize uncertainties associated with computer simulation of reacting multiphase flows encountered in energy producing systems such as a coal gasifier. The current work presents the preliminary results in applying non-intrusive parametric uncertainty quantification and propagation techniques with NETL's open-source multiphase computational fluid dynamics software MFIX. For this purpose an open-source uncertainty quantification toolkit, PSUADE developed at the Lawrence Livermore National Laboratory (LLNL) has been interfaced with MFIX software. In this study, the sources of uncertainty associated with numerical approximation and model form have been neglected, and only the model input parametric uncertainty with forward propagation has been investigated by constructing a surrogate model based on data-fitted response surface for a multiphase flow demonstration problem. Monte Carlo simulation was employed for forward propagation of the aleatory type input uncertainties. Several insights gained based on the outcome of these simulations are presented such as how inadequate characterization of uncertainties can affect the reliability of the prediction results. Also a global sensitivity study using Sobol' indices was performed to better understand the contribution of input parameters to the variability observed in response variable.

  8. Dynamic polarizability of rotating particles in electrorheological fluids.

    PubMed

    Xiao, J J; Huang, J P; Yu, K W

    2008-06-01

    A rotating particle in electrorheological (ER) fluid leads to a displacement of its polarization charges on the surface which relax toward the external applied field E0, resulting in a steady-state polarization at an angle with respect to E0. This dynamic effect has shown to affect the ER fluid properties dramatically. In this paper, we develop a dynamic effective medium theory (EMT) for a system containing rotating particles of finite volume fraction. This is a generalization of established EMT to account for the interactions between many rotating particles. While the theory is valid for three dimensions, the results in a special two-dimensional configuration show that the system exhibits an off-diagonal polarization response in addition to a diagonal polarization response, which resembles the classic Hall effect. The diagonal response monotonically decreases with increasing rotational speed, whereas the off-diagonal response exhibits a maximum at a reduced rotational angular velocity omega0, compared to the case of isolated rotating particles. This implies a way of measurement on the interacting relaxation time. The dependencies of the diagonal and off-diagonal responses on various factors, such as omega0, the volume fraction, and the dielectric contrast, are discussed.

  9. The aerospace plane design challenge: Credible computational fluid dynamics results

    NASA Technical Reports Server (NTRS)

    Mehta, Unmeel B.

    1990-01-01

    Computational fluid dynamics (CFD) is necessary in the design processes of all current aerospace plane programs. Single-stage-to-orbit (STTO) aerospace planes with air-breathing supersonic combustion are going to be largely designed by means of CFD. The challenge of the aerospace plane design is to provide credible CFD results to work from, to assess the risk associated with the use of those results, and to certify CFD codes that produce credible results. To establish the credibility of CFD results used in design, the following topics are discussed: CFD validation vis-a-vis measurable fluid dynamics (MFD) validation; responsibility for credibility; credibility requirement; and a guide for establishing credibility. Quantification of CFD uncertainties helps to assess success risk and safety risks, and the development of CFD as a design tool requires code certification. This challenge is managed by designing the designers to use CFD effectively, by ensuring quality control, and by balancing the design process. For designing the designers, the following topics are discussed: how CFD design technology is developed; the reasons Japanese companies, by and large, produce goods of higher quality than the U.S. counterparts; teamwork as a new way of doing business; and how ideas, quality, and teaming can be brought together. Quality control for reducing the loss imparted to the society begins with the quality of the CFD results used in the design process, and balancing the design process means using a judicious balance of CFD and MFD.

  10. Dynamic Studies of Lung Fluid Clearance with Phase Contrast Imaging

    SciTech Connect

    Kitchen, Marcus J.; Williams, Ivan; Irvine, Sarah C.; Morgan, Michael J.; Paganin, David M.; Lewis, Rob A.; Pavlov, Konstantin; Hooper, Stuart B.; Wallace, Megan J.; Siu, Karen K. W.; Yagi, Naoto; Uesugi, Kentaro

    2007-01-19

    Clearance of liquid from the airways at birth is a poorly understood process, partly due to the difficulties of observing and measuring the distribution of air within the lung. Imaging dynamic processes within the lung in vivo with high contrast and spatial resolution is therefore a major challenge. However, phase contrast X-ray imaging is able to exploit inhaled air as a contrast agent, rendering the lungs of small animals visible due to the large changes in the refractive index at air/tissue interfaces. In concert with the high spatial resolution afforded by X-ray imaging systems (<100 {mu}m), propagation-based phase contrast imaging is ideal for studying lung development. To this end we have utilized intense, monochromatic synchrotron radiation, together with a fast readout CCD camera, to study fluid clearance from the lungs of rabbit pups at birth. Local rates of fluid clearance have been measured from the dynamic sequences using a single image phase retrieval algorithm.

  11. Dynamic hysteresis in the rheology of complex fluids.

    PubMed

    Puisto, Antti; Mohtaschemi, Mikael; Alava, Mikko J; Illa, Xavier

    2015-04-01

    Recently, rheological hysteresis has been studied systematically in a wide range of complex fluids combining global rheology and time-resolved velocimetry. In this paper we present an analysis of the roles of the three most fundamental mechanisms in simple-yield-stress fluids: structure dynamics, viscoelastic response, and spatial flow heterogeneities, i.e., time-dependent shear bands. Dynamical hysteresis simulations are done analogously to rheological ramp-up and -down experiments on a coupled model which incorporates viscoelasticity and time-dependent structure evolution. Based on experimental data, a coupling between hysteresis measured from the local velocity profiles and that measured from the global flow curve has been suggested. According to the present model, even if transient shear banding appears during the shear ramps, in typical narrow-gap devices, only a small part of the hysteretic response can be attributed to heterogeneous flow. This results in decoupling of the hysteresis measured from the local velocity profiles and the global flow curve, demonstrating that for an arbitrary time-dependent rheological response this proposed coupling can be very weak.

  12. High-performance holographic technologies for fluid-dynamics experiments

    PubMed Central

    Orlov, Sergei S.; Abarzhi, Snezhana I.; Oh, Se Baek; Barbastathis, George; Sreenivasan, Katepalli R.

    2010-01-01

    Modern technologies offer new opportunities for experimentalists in a variety of research areas of fluid dynamics. Improvements are now possible in the state-of-the-art in precision, dynamic range, reproducibility, motion-control accuracy, data-acquisition rate and information capacity. These improvements are required for understanding complex turbulent flows under realistic conditions, and for allowing unambiguous comparisons to be made with new theoretical approaches and large-scale numerical simulations. One of the new technologies is high-performance digital holography. State-of-the-art motion control, electronics and optical imaging allow for the realization of turbulent flows with very high Reynolds number (more than 107) on a relatively small laboratory scale, and quantification of their properties with high space–time resolutions and bandwidth. In-line digital holographic technology can provide complete three-dimensional mapping of the flow velocity and density fields at high data rates (over 1000 frames per second) over a relatively large spatial area with high spatial (1–10 μm) and temporal (better than a few nanoseconds) resolution, and can give accurate quantitative description of the fluid flows, including those of multi-phase and unsteady conditions. This technology can be applied in a variety of problems to study fundamental properties of flow–particle interactions, rotating flows, non-canonical boundary layers and Rayleigh–Taylor mixing. Some of these examples are discussed briefly. PMID:20211881

  13. Respiratory mechanics and fluid dynamics after lung resection surgery.

    PubMed

    Miserocchi, Giuseppe; Beretta, Egidio; Rivolta, Ilaria

    2010-08-01

    Thoracic surgery that requires resection of a portion of lung or of a whole lung profoundly alters the mechanical and fluid dynamic setting of the lung-chest wall coupling, as well as the water balance in the pleural space and in the remaining lung. The most frequent postoperative complications are of a respiratory nature, and their incidence increases the more the preoperative respiratory condition seems compromised. There is an obvious need to identify risk factors concerning mainly the respiratory function, without neglecting the importance of other comorbidities, such as coronary disease. At present, however, a satisfactory predictor of postoperative cardiopulmonary complications is lacking; postoperative morbidity and mortality have remained unchanged in the last 10 years. The aim of this review is to provide a pathophysiologic interpretation of the main respiratory complications of a respiratory nature by relying on new concepts relating to lung fluid dynamics and mechanics. New parameters are proposed to improve evaluation of respiratory function from pre- to the early postoperative period when most of the complications occur.

  14. Bridging fluctuating hydrodynamics and molecular dynamics simulations of fluids.

    PubMed

    Voulgarakis, Nikolaos K; Chu, Jhih-Wei

    2009-04-01

    A new multiscale coarse-graining (CG) methodology is developed to bridge molecular and hydrodynamic models of a fluid. The hydrodynamic representation considered in this work is based on the equations of fluctuating hydrodynamics (FH). The essence of this method is a mapping from the position and velocity vectors of a snapshot of a molecular dynamics (MD) simulation to the field variables on Eulerian cells of a hydrodynamic representation. By explicit consideration of the effective lengthscale d(mol) that characterizes the volume of a molecule, the computed density fluctuations from MD via our mapping procedure have volume dependence that corresponds to a grand canonical ensemble of a cold liquid even when a small cell length (5-10 A) is used in a hydrodynamic representation. For TIP3P water at 300 K and 1 atm, d(mol) is found to be 2.4 A, corresponding to the excluded radius of a water molecule as revealed by its center-of-mass radial distribution function. By matching the density fluctuations and autocorrelation functions of momentum fields computed from solving the FH equations with those computed from MD simulation, the sound velocity and shear and bulk viscosities of a CG hydrodynamic model can be determined directly from MD. Furthermore, a novel staggered discretization scheme is developed for solving the FH equations of an isothermal compressive fluid in a three dimensional space with a central difference method. This scheme demonstrates high accuracy in satisfying the fluctuation-dissipation theorem. Since the causative relationship between field variables and fluxes is captured, we demonstrate that the staggered discretization scheme also predicts correct physical behaviors in simulating transient fluid flows. The techniques presented in this work may also be employed to design multiscale strategies for modeling complex fluids and macromolecules in solution. PMID:19355721

  15. Computational fluid dynamic modeling of fluidized-bed polymerization reactors

    SciTech Connect

    Rokkam, Ram

    2012-01-01

    Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.

  16. Dynamic high pressure: why it makes metallic fluid hydrogen

    NASA Astrophysics Data System (ADS)

    Nellis, William

    2015-06-01

    Metallic fluid H (MFH) was made by dynamic compression decades after Wigner and Huntington (WH) predicted it in 1935. The density of MFH is within a few percent of the density predicted by WH. MFH was made by multiple-shock compression of liquid H2, which process is quasi-isentropic and thermally equilibrated. The compressions were isentropic but produced enough dissipation as temperature T and entropy S to drive the crossover from insulating H2 to metallic H at 9-fold compressed atomic H density. T and S were tuned by temporally shaping the applied pressure pulse such that H2 dissociated to H at sufficiently high density to make a highly degenerate metal. The basic ideas of dynamic compression, also known as supersonic, adiabatic, nonlinear hydrodynamics, were developed in the last half of the Nineteenth Century. Our purposes are to (i) present a brief review of dynamic compression and its affects on materials, (ii) review considerations that led to the sample holder designed specifically to make MFH, and (iii) present a inter-comparison of dynamic and static methods relative to their prospects for making metallic H.

  17. Slow and long-ranged dynamical heterogeneities in dissipative fluids.

    PubMed

    Avila, Karina E; Castillo, Horacio E; Vollmayr-Lee, Katharina; Zippelius, Annette

    2016-06-28

    A two-dimensional bidisperse granular fluid is shown to exhibit pronounced long-ranged dynamical heterogeneities as dynamical arrest is approached. Here we focus on the most direct approach to study these heterogeneities: we identify clusters of slow particles and determine their size, Nc, and their radius of gyration, RG. We show that , providing direct evidence that the most immobile particles arrange in fractal objects with a fractal dimension, df, that is observed to increase with packing fraction ϕ. The cluster size distribution obeys scaling, approaching an algebraic decay in the limit of structural arrest, i.e., ϕ→ϕc. Alternatively, dynamical heterogeneities are analyzed via the four-point structure factor S4(q,t) and the dynamical susceptibility χ4(t). S4(q,t) is shown to obey scaling in the full range of packing fractions, 0.6 ≤ϕ≤ 0.805, and to become increasingly long-ranged as ϕ→ϕc. Finite size scaling of χ4(t) provides a consistency check for the previously analyzed divergences of χ4(t) ∝ (ϕ-ϕc)(-γχ) and the correlation length ξ∝ (ϕ-ϕc)(-γξ). We check the robustness of our results with respect to our definition of mobility. The divergences and the scaling for ϕ→ϕc suggest a non-equilibrium glass transition which seems qualitatively independent of the coefficient of restitution. PMID:27230572

  18. Slow and long-ranged dynamical heterogeneities in dissipative fluids.

    PubMed

    Avila, Karina E; Castillo, Horacio E; Vollmayr-Lee, Katharina; Zippelius, Annette

    2016-06-28

    A two-dimensional bidisperse granular fluid is shown to exhibit pronounced long-ranged dynamical heterogeneities as dynamical arrest is approached. Here we focus on the most direct approach to study these heterogeneities: we identify clusters of slow particles and determine their size, Nc, and their radius of gyration, RG. We show that , providing direct evidence that the most immobile particles arrange in fractal objects with a fractal dimension, df, that is observed to increase with packing fraction ϕ. The cluster size distribution obeys scaling, approaching an algebraic decay in the limit of structural arrest, i.e., ϕ→ϕc. Alternatively, dynamical heterogeneities are analyzed via the four-point structure factor S4(q,t) and the dynamical susceptibility χ4(t). S4(q,t) is shown to obey scaling in the full range of packing fractions, 0.6 ≤ϕ≤ 0.805, and to become increasingly long-ranged as ϕ→ϕc. Finite size scaling of χ4(t) provides a consistency check for the previously analyzed divergences of χ4(t) ∝ (ϕ-ϕc)(-γχ) and the correlation length ξ∝ (ϕ-ϕc)(-γξ). We check the robustness of our results with respect to our definition of mobility. The divergences and the scaling for ϕ→ϕc suggest a non-equilibrium glass transition which seems qualitatively independent of the coefficient of restitution.

  19. Recent developments in the dynamics of advanced rotor systems

    NASA Technical Reports Server (NTRS)

    Johnson, W.

    1985-01-01

    The problems that were encountered in the dynamics of advanced rotor systems are described. The methods for analyzing these problems are discussed, as are past solutions of the problems. To begin, the basic dynamic problems of rotors are discussed: aeroelastic stability, rotor and airframe loads, and aircraft vibration. Next, advanced topics that are the subject of current research are described: vibration control, dynamic upflow, finite element analyses, and composite materials. Finally, the dynamics of various rotorcraft configurations are considered: hingeless rotors, bearingless rotors, rotors with circulation control, coupled rotor/engine dynamics, articulated rotors, and tilting proprotor aircraft.

  20. Dynamic and thermodynamic stability of relativistic, perfect fluid stars

    NASA Astrophysics Data System (ADS)

    Green, Stephen R.; Schiffrin, Joshua S.; Wald, Robert M.

    2014-02-01

    We consider perfect fluid bodies (‘stars’) in general relativity, with the local state of the fluid specified by its 4-velocity, ua, its ‘particle number density’, n, and its ‘entropy per particle’, s. A star is said to be in dynamic equilibrium if it is a stationary, axisymmetric solution to the Einstein-fluid equations with circular flow. A star is said to be in thermodynamic equilibrium if it is in dynamic equilibrium and its total entropy, S, is an extremum for all variations of initial data that satisfy the Einstein constraint equations and have fixed total mass, M, particle number, N, and angular momentum, J. We prove that for a star in dynamic equilibrium, the necessary and sufficient condition for thermodynamic equilibrium is constancy of angular velocity, Ω, redshifted temperature, \\widetilde{T}, and redshifted chemical potential, \\widetilde{\\mu }. A star in dynamic equilibrium is said to be linearly dynamically stable if all physical, gauge invariant quantities associated with linear perturbations of the star remain bounded in time; it is said to be mode stable if there are no exponentially growing solutions that are not pure gauge. A star in thermodynamic equilibrium is said to be linearly thermodynamically stable if δ2S < 0 for all variations at fixed M, N, and J; equivalently, a star in thermodynamic equilibrium is linearly thermodynamically stable if \\delta ^2 M - \\widetilde{T} \\delta ^2 S -\\widetilde{\\mu } \\delta ^2 N - \\Omega \\delta ^2 J > 0 for all variations that, to first order, satisfy δM = δN = δJ = 0 (and, hence, δS = 0). Friedman previously identified positivity of canonical energy, {E}, as a criterion for dynamic stability and argued that all rotating stars are dynamically unstable to sufficiently non-axisymmetric perturbations (the CFS instability), so our main focus is on axisymmetric stability (although we develop our formalism and prove many results for non-axisymmetric perturbations as well). We show that

  1. Flight Simulation of Taketombo Based on Computational Fluid Dynamics and Computational Flight Dynamics

    NASA Astrophysics Data System (ADS)

    Kawamura, Kohei; Ueno, Yosuke; Nakamura, Yoshiaki

    In the present study we have developed a numerical method to simulate the flight dynamics of a small flying body with unsteady motion, where both aerodynamics and flight dynamics are fully considered. A key point of this numerical code is to use computational fluid dynamics and computational flight dynamics at the same time, which is referred to as CFD2, or double CFDs, where several new ideas are adopted in the governing equations, the method to make each quantity nondimensional, and the coupling method between aerodynamics and flight dynamics. This numerical code can be applied to simulate the unsteady motion of small vehicles such as micro air vehicles (MAV). As a sample calculation, we take up Taketombo, or a bamboo dragonfly, and its free flight in the air is demonstrated. The eventual aim of this research is to virtually fly an aircraft with arbitrary motion to obtain aerodynamic and flight dynamic data, which cannot be taken in the conventional wind tunnel.

  2. Fundamentals of Trapped Ion Mobility Spectrometry Part II: Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Silveira, Joshua A.; Michelmann, Karsten; Ridgeway, Mark E.; Park, Melvin A.

    2016-04-01

    Trapped ion mobility spectrometry (TIMS) is a new high resolution (R up to ~300) separation technique that utilizes an electric field to hold ions stationary against a moving gas. Recently, an analytical model for TIMS was derived and, in part, experimentally verified. A central, but not yet fully explored, component of the model involves the fluid dynamics at work. The present study characterizes the fluid dynamics in TIMS using simulations and ion mobility experiments. Results indicate that subsonic laminar flow develops in the analyzer, with pressure-dependent gas velocities between ~120 and 170 m/s measured at the position of ion elution. One of the key philosophical questions addressed is: how can mobility be measured in a dynamic system wherein the gas is expanding and its velocity is changing? We noted previously that the analytically useful work is primarily done on ions as they traverse the electric field gradient plateau in the analyzer. In the present work, we show that the position-dependent change in gas velocity on the plateau is balanced by a change in pressure and temperature, ultimately resulting in near position-independent drag force. That the drag force, and related variables, are nearly constant allows for the use of relatively simple equations to describe TIMS behavior. Nonetheless, we derive a more comprehensive model, which accounts for the spatial dependence of the flow variables. Experimental resolving power trends were found to be in close agreement with the theoretical dependence of the drag force, thus validating another principal component of TIMS theory.

  3. Apparatus for characterizing the temporo-spatial properties of a dynamic fluid front and method thereof

    DOEpatents

    Battiste, Richard L

    2013-12-31

    Methods and apparatus are described for characterizing the temporal-spatial properties of a dynamic fluid front within a mold space while the mold space is being filled with fluid. A method includes providing a mold defining a mold space and having one or more openings into the mold space; heating a plurality of temperature sensors that extend into the mold space; injecting a fluid into th emold space through the openings, the fluid experiencing a dynamic fluid front while filling the mold space with a fluid; and characterizing temporal-spatial properties of the dynamic fluid front by monitoring a termperature of each of the plurality of heated temperature sensors while the mold space is being filled with the fluid. An apparatus includes a mold defining a mold space; one or more openings for introducing a fluid into th emold space and filling the mold space with the fluid, the fluid experiencing a dynamic fluid front while filling the mold space; a plurality of heated temperature sensors extending into the mold space; and a computer coupled to the plurality of heated temperature sensors for characterizing the temporal-spatial properties of the dynamic fluid front.

  4. Apparatus for characterizing the temporo-spatial properties of a dynamic fluid front and method thereof

    DOEpatents

    Battiste, Richard L.

    2007-12-25

    Methods and apparatus are described for characterizing the temporal-spatial properties of a dynamic fluid front within a mold space while the mold space is being filled with fluid. A method includes providing a mold defining a mold space and having one or more openings into the mold space; heating a plurality of temperature sensors that extend into the mold space; injecting a fluid into the mold space through the openings, the fluid experiencing a dynamic fluid front while filling the mold space with the fluid; and characterizing temporal-spatial properties of the dynamic fluid front by monitoring a temperature of each of the plurality of heated temperature sensors while the mold space is being filled with the fluid. An apparatus includes a mold defining a mold space; one or more openings for introducing a fluid into the mold space and filling the mold space with the fluid, the fluid experiencing a dynamic fluid front while filling the mold space; a plurality of heated temperature sensors extending into the mold space; and a computer coupled to the plurality of heated temperature sensors for characterizing the temporal-spatial properties of the dynamic fluid front.

  5. Fluid Dynamics of Carbon Dioxide Disposal into Saline Aquifers

    SciTech Connect

    Garcia, Julio Enrique

    2003-12-18

    Injection of carbon dioxide (CO{sub 2}) into saline aquifers has been proposed as a means to reduce greenhouse gas emissions (geological carbon sequestration). Large-scale injection of CO{sub 2} will induce a variety of coupled physical and chemical processes, including multiphase fluid flow, fluid pressurization and changes in effective stress, solute transport, and chemical reactions between fluids and formation minerals. This work addresses some of these issues with special emphasis given to the physics of fluid flow in brine formations. An investigation of the thermophysical properties of pure carbon dioxide, water and aqueous solutions of CO{sub 2} and NaCl has been conducted. As a result, accurate representations and models for predicting the overall thermophysical behavior of the system CO{sub 2}-H{sub 2}O-NaCl are proposed and incorporated into the numerical simulator TOUGH2/ECO{sub 2}. The basic problem of CO{sub 2} injection into a radially symmetric brine aquifer is used to validate the results of TOUGH2/ECO2. The numerical simulator has been applied to more complex flow problem including the CO{sub 2} injection project at the Sleipner Vest Field in the Norwegian sector of the North Sea and the evaluation of fluid flow dynamics effects of CO{sub 2} injection into aquifers. Numerical simulation results show that the transport at Sleipner is dominated by buoyancy effects and that shale layers control vertical migration of CO{sub 2}. These results are in good qualitative agreement with time lapse surveys performed at the site. High-resolution numerical simulation experiments have been conducted to study the onset of instabilities (viscous fingering) during injection of CO{sub 2} into saline aquifers. The injection process can be classified as immiscible displacement of an aqueous phase by a less dense and less viscous gas phase. Under disposal conditions (supercritical CO{sub 2}) the viscosity of carbon dioxide can be less than the viscosity of the aqueous

  6. Magnetic resonance measurement of fluid dynamics and transport in tube flow of a near-critical fluid

    NASA Astrophysics Data System (ADS)

    Bray, Joshua M.; Rassi, Erik M.; Seymour, Joseph D.; Codd, Sarah L.

    2014-07-01

    An ability to predict fluid dynamics and transport in supercritical fluids is essential for optimization of applications such as carbon sequestration, enhanced oil recovery, "green" solvents, and supercritical coolant systems. While much has been done to model supercritical velocity distributions, experimental characterization is sparse, owing in part to a high sensitivity to perturbation by measurement probes. Magnetic resonance (MR) techniques, however, detect signal noninvasively from the fluid molecules and thereby overcome this obstacle to measurement. MR velocity maps and propagators (i.e., probability density functions of displacement) were acquired of a flowing fluid in several regimes about the critical point, providing quantitative data on the transport and fluid dynamics in the system. Hexafluoroethane (C2F6) was pumped at 0.5 ml/min in a cylindrical tube through an MR system, and propagators as well as velocity maps were measured at temperatures and pressures below, near, and above the critical values. It was observed that flow of C2F6 with thermodynamic properties far above or below the critical point had the Poiseuille flow distribution of an incompressible Newtonian fluid. Flows with thermodynamic properties near the critical point exhibit complex flow distributions impacted by buoyancy and viscous forces. The approach to steady state was also observed and found to take the longest near the critical point, but once it was reached, the dynamics were stable and reproducible. These data provide insight into the interplay between the critical phase transition thermodynamics and the fluid dynamics, which control transport processes.

  7. Fluid mechanics of dynamic stall. I - Unsteady flow concepts

    NASA Technical Reports Server (NTRS)

    Ericsson, L. E.; Reding, J. P.

    1988-01-01

    Advanced military aircraft 'supermaneuverability' requirements entail the sustained operation of airfoils at stalled flow conditions. The present work addresses the effects of separated flow on vehicle dynamics; an analytic method is presented which employs static experimental data to predict the separated flow effect on incompressible unsteady aerodynamics. The key parameters in the analytic relationship between steady and nonsteady aerodynamics are the time-lag before a change of flow conditions can affect the separation-induced aerodynamic loads, the accelerated flow effect, and the moving wall effect.

  8. Computational fluid dynamics studies of nuclear rocket performance

    SciTech Connect

    Stubbs, R.M.; Kim, S.C.; Benson, T.J.

    1994-06-01

    A CFD analysis of a low pressure nuclear rocket concept is presented with the use of an advanced chemical kinetics, Navier-Stokes code. The computations describe the flow field in detail, including gas dynamic, thermodynamic and chemical properties, as well as global performance quantities such as specific impulse. Computational studies of several rocket nozzle shapes are conducted in an attempt to maximize hydrogen recombination. These Navier-Stokes calculations, which include real gas and viscous effects, predict lower performance values than have been reported heretofore.

  9. Computational fluid dynamics studies of nuclear rocket performance

    NASA Technical Reports Server (NTRS)

    Stubbs, Robert M.; Kim, Suk C.; Benson, Thomas J.

    1994-01-01

    A CFD analysis of a low pressure nuclear rocket concept is presented with the use of an advanced chemical kinetics, Navier-Stokes code. The computations describe the flow field in detail, including gas dynamic, thermodynamic and chemical properties, as well as global performance quantities such as specific impulse. Computational studies of several rocket nozzle shapes are conducted in an attempt to maximize hydrogen recombination. These Navier-Stokes calculations, which include real gas and viscous effects, predict lower performance values than have been reported heretofore.

  10. Computational fluid dynamics framework for aerodynamic model assessment

    NASA Astrophysics Data System (ADS)

    Vallespin, D.; Badcock, K. J.; Da Ronch, A.; White, M. D.; Perfect, P.; Ghoreyshi, M.

    2012-07-01

    This paper reviews the work carried out at the University of Liverpool to assess the use of CFD methods for aircraft flight dynamics applications. Three test cases are discussed in the paper, namely, the Standard Dynamic Model, the Ranger 2000 jet trainer and the Stability and Control Unmanned Combat Air Vehicle. For each of these, a tabular aerodynamic model based on CFD predictions is generated along with validation against wind tunnel experiments and flight test measurements. The main purpose of the paper is to assess the validity of the tables of aerodynamic data for the force and moment prediction of realistic aircraft manoeuvres. This is done by generating a manoeuvre based on the tables of aerodynamic data, and then replaying the motion through a time-accurate computational fluid dynamics calculation. The resulting forces and moments from these simulations were compared with predictions from the tables. As the latter are based on a set of steady-state predictions, the comparisons showed perfect agreement for slow manoeuvres. As manoeuvres became more aggressive some disagreement was seen, particularly during periods of large rates of change in attitudes. Finally, the Ranger 2000 model was used on a flight simulator.

  11. 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.

  12. A numerical method to study the dynamics of capillary fluid systems

    NASA Astrophysics Data System (ADS)

    Herrada, M. A.; Montanero, J. M.

    2016-02-01

    We propose a numerical approach to study both the nonlinear dynamics and linear stability of capillary fluid systems. In the nonlinear analysis, the time-dependent fluid region is mapped onto a fixed numerical domain through a coordinate transformation. The hydrodynamic equations are spatially discretized with the Chebyshev spectral collocation technique, while an implicit time advancement is performed using second-order backward finite differences. The resulting algebraic equations are solved with the iterative Newton-Raphson technique. The most novel aspect of the method is the fact that the elements of the Jacobian of the discretized system of equations are symbolic functions calculated before running the simulation. These functions are evaluated numerically in the Newton-Raphson iterations to find the solution at each time step, which reduces considerably the computing time. Besides, this numerical procedure can be easily adapted to solve the eigenvalue problem which determines the linear global modes of the capillary system. Therefore, both the nonlinear dynamics and the linear stability analysis can be conducted with essentially the same algorithm. We validate this numerical approach by studying the dynamics of a liquid bridge close to its minimum volume stability limit. The results are virtually the same as those obtained with other methods. The proposed approach proves to be much more computationally efficient than those other methods. Finally, we show the versatility of the method by calculating the linear global modes of a gravitational jet.

  13. Computational fluid dynamics investigation of turbulence models for non-newtonian fluid flow in anaerobic digesters.

    PubMed

    Wu, Binxin

    2010-12-01

    In this paper, 12 turbulence models for single-phase non-newtonian fluid flow in a pipe are evaluated by comparing the frictional pressure drops obtained from computational fluid dynamics (CFD) with those from three friction factor correlations. The turbulence models studied are (1) three high-Reynolds-number k-ε models, (2) six low-Reynolds-number k-ε models, (3) two k-ω models, and (4) the Reynolds stress model. The simulation results indicate that the Chang-Hsieh-Chen version of the low-Reynolds-number k-ε model performs better than the other models in predicting the frictional pressure drops while the standard k-ω model has an acceptable accuracy and a low computing cost. In the model applications, CFD simulation of mixing in a full-scale anaerobic digester with pumped circulation is performed to propose an improvement in the effective mixing standards recommended by the U.S. EPA based on the effect of rheology on the flow fields. Characterization of the velocity gradient is conducted to quantify the growth or breakage of an assumed floc size. Placement of two discharge nozzles in the digester is analyzed to show that spacing two nozzles 180° apart with each one discharging at an angle of 45° off the wall is the most efficient. Moreover, the similarity rules of geometry and mixing energy are checked for scaling up the digester.

  14. Vortical Flows Research Program of the Fluid Dynamics Research Branch

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The research interests of the staff of the Fluid Dynamics Research Branch in the general area of vortex flows are summarized. A major factor in the development of enchanced maneuverability and reduced drag by aerodynamic means is the use of effective vortex control devices. The key to control is the use of emerging computational tools for predicting viscous fluid flow in close coordination with fundamental experiments. In fact, the extremely complex flow fields resulting from numerical solutions to boundary value problems based on the Navier-Stokes equations requires an intimate relationship between computation and experiment. The field of vortex flows is important in so many practical areas that a concerted effort in this area is justified. A brief background of the research activity undertaken is presented, including a proposed classification of the research areas. The classification makes a distinction between issues related to vortex formation and structure, and work on vortex interactions and evolution. Examples of current research results are provided, along with references where available. Based upon the current status of research and planning, speculation on future research directions of the group is also given.

  15. Transcapillary fluid dynamics during ovarian stimulation for in vitro fertilization.

    PubMed

    Tollan, A; Holst, N; Forsdahl, F; Fadnes, H O; Oian, P; Maltau, J M

    1990-02-01

    Transcapillary fluid dynamics were studied in 10 women during ovarian stimulation for in vitro fertilization. The examinations were done on the first day of stimulation (day 3 of the menstrual cycle, mean serum estradiol concentration 0.2 nmol/L), and the day before oocyte aspiration (day 10 to 12, mean serum estradiol concentration 6.8 nmol/L). Interstitial colloid osmotic pressure was measured on the thorax at heart level by the "wick" method, and interstitial hydrostatic pressure by the "wick-in-needle" method. Plasma colloid osmotic pressure decreased (mean, 2.0 mm Hg; p less than 0.002) and interstitial colloid osmotic pressure increased (mean, 1.0 mm Hg; p less than 0.02) during hormonal stimulation. This implies a reduced transcapillary colloid osmotic gradient (plasma colloid osmotic pressure--interstitial colloid osmotic pressure), probably because of increased capillary permeability to plasma proteins. Hemoglobin and hematocrit were significantly reduced, and body weight and foot volume significantly increased. These results demonstrate that during ovarian stimulation there are both water retention and augmented filtration of fluid from the vascular to the interstitial compartment. This may be of significance for the pathophysiologic condition in the ovarian hyperstimulation syndrome.

  16. Czech cryogenic fluid dynamics inspired by Russ Donnelly

    NASA Astrophysics Data System (ADS)

    Skrbek, Ladislav

    2015-11-01

    Following nearly five years of work along with Russ in Eugene on cryogenic turbulent convection and quantum grid turbulence, two laboratories in Prague and in Brno have been established to continue experimental research in cryogenic fluid dynamics using all three forms of cryogenic 4He - cold helium gas, normal liquid He I and superfluid He - as excellent multi-purpose working fluids. We review some of our investigations of very high Rayleigh number cryogenic thermal convection and classical and quantum turbulence in liquid helium. In particular, we discuss heat transfer efficiency of turbulent Rayleigh-Benard convection and the role of non-Oberbeck-Boussinesq conditions on possible transition to its ultimate regime; our second sound attenuation experiments probing both steady state and decaying coflow, counterflow and pure superflow of He II through channels of square cross-section including the concept of effective kinematic viscosity. We then introduce visualization experiments of classical and quantum flows of liquid helium using micron-size hydogen/deuterium particles and our recent results on transition to quantum turbulence based on the revisited experiments with a torsionally oscillating disc. Supported by GACR P203/11/0442 and 203/14/02005S.

  17. High-Performance Java Codes for Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Riley, Christopher; Chatterjee, Siddhartha; Biswas, Rupak; Biegel, Bryan (Technical Monitor)

    2001-01-01

    The computational science community is reluctant to write large-scale computationally -intensive applications in Java due to concerns over Java's poor performance, despite the claimed software engineering advantages of its object-oriented features. Naive Java implementations of numerical algorithms can perform poorly compared to corresponding Fortran or C implementations. To achieve high performance, Java applications must be designed with good performance as a primary goal. This paper presents the object-oriented design and implementation of two real-world applications from the field of Computational Fluid Dynamics (CFD): a finite-volume fluid flow solver (LAURA, from NASA Langley Research Center), and an unstructured mesh adaptation algorithm (2D_TAG, from NASA Ames Research Center). This work builds on our previous experience with the design of high-performance numerical libraries in Java. We examine the performance of the applications using the currently available Java infrastructure and show that the Java version of the flow solver LAURA performs almost within a factor of 2 of the original procedural version. Our Java version of the mesh adaptation algorithm 2D_TAG performs within a factor of 1.5 of its original procedural version on certain platforms. Our results demonstrate that object-oriented software design principles are not necessarily inimical to high performance.

  18. Application of a distributed network in computational fluid dynamic simulations

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    A general-purpose 3-D, incompressible Navier-Stokes algorithm is implemented on a network of concurrently operating workstations using parallel virtual machine (PVM) and compared with its performance on a CRAY Y-MP and on an Intel iPSC/860. The problem is relatively computationally intensive, and has a communication structure based primarily on nearest-neighbor communication, making it ideally suited to message passing. Such problems are frequently encountered in computational fluid dynamics (CDF), and their solution is increasingly in demand. The communication structure is explicitly coded in the implementation to fully exploit the regularity in message passing in order to produce a near-optimal solution. Results are presented for various grid sizes using up to eight processors.

  19. Fluid dynamics of forward swimming and turning for jellyfish

    NASA Astrophysics Data System (ADS)

    Miller, Laura

    2012-11-01

    Jellyfish propel themselves through the water through periodic contractions of their elastic bells. Some jellyfish, such as the box jellyfish Tripedalia cystophora and the upside down jellyfish Cassiopea xamachana, can perform turns via asymmetric contractions of the bell and by generating asymmetries in the outflow opening of the bell. The fluid dynamics of jellyfish forward propulsion and turning is explored here using the immersed boundary method. The 2D and 3D Navier-Stokes equations are coupled to the motion of a simplified jellyfish represented by an elastic boundary. An adaptive and parallelized version of the immersed boundary method (IBAMR) is used to resolve the detailed structure of the vortex wake. The asymmetric contraction and structure of the jellyfish generates asymmetries in the starting and stopping vortices. This creates a diagonal jet and a net torque acting on the jellyfish.

  20. Computational fluid dynamics for defect control in semiconductor processing

    NASA Astrophysics Data System (ADS)

    Kempka, S. N.; Geller, A. S.

    Finite element simulations of mixed convection flow (Re less than 100, Gr less than 10(exp 6)) are presented for two gas flow reactors characteristic of those used in the manufacture of microchips. The simulations demonstrate the usefulness of FIDAP (a finite element, Navier-Stokes code developed by Fluid Dynamics International, Inc.) as a tool to design new reactors and to assess the effects of varying operating conditions in present reactors. The calculations predict the existence of thermal plumes and recirculation regions within reactors. These flow nonuniformities are important since they can result in fatal defects in microchips. Comparisons between solutions obtained using a Boussinesq model and FIDAP's variable density model are presented. The FIDAP calculations agree with previous simulations using more detailed models, supporting the use of FIDAP as a design tool in the semiconductor industry.

  1. Fluid dynamics in airway bifurcations: III. Localized flow conditions.

    PubMed

    Martonen, T B; Guan, X; Schreck, R M

    2001-04-01

    Localized flow conditions (e.g., backflows) in transition regions between parent and daughter airways of bifurcations were investigated using a computational fluid dynamics software code (FIDAP) with a Cray T90 supercomputer. The configurations of the bifurcations were based on Schreck s (1972) laboratory models. The flow intensities and spatial regions of reversed motion were simulated for different conditions. The effects of inlet velocity profiles, Reynolds numbers, and dimensions and orientations of airways were addressed. The computational results showed that backflow was increased for parabolic inlet conditions, larger Reynolds numbers, and larger daughter-to-parent diameter ratios. This article is the third in a systematic series addressed in this issue; the first addressed primary velocity patterns and the second discussed secondary currents.

  2. Modeling of a continuous pretreatment reactor using computational fluid dynamics.

    PubMed

    Berson, R Eric; Dasari, Rajesh K; Hanley, Thomas R

    2006-01-01

    Computational fluid dynamic simulations are employed to predict flow characteristics in a continuous auger driven reactor designed for the dilute acid pretreatment of biomass. Slurry containing a high concentration of biomass solids exhibits a high viscosity, which poses unique mixing issues within the reactor. The viscosity increases significantly with a small increase in solids concentration and also varies with temperature. A well-mixed slurry is desirable to evenly distribute acid on biomass, prevent buildup on the walls of the reactor, and provides an uniform final product. Simulations provide flow patterns obtained over a wide range of viscosities and pressure distributions, which may affect reaction rates. Results provide a tool for analyzing sources of inconsistencies in product quality and insight into future design and operating parameters.

  3. Wind tunnel requirements for computational fluid dynamics code verification

    NASA Technical Reports Server (NTRS)

    Marvin, Joseph G.

    1987-01-01

    The role of experiment in the development of Computational Fluid Dynamics (CFD) for aerodynamic flow field prediction is discussed. Requirements for code verification from two sources that pace the development of CFD are described for: (1) development of adequate flow modeling, and (2) establishment of confidence in the use of CFD to predict complex flows. The types of data needed and their accuracy differs in detail and scope and leads to definite wind tunnel requirements. Examples of testing to assess and develop turbulence models, and to verify code development, are used to establish future wind tunnel testing requirements. Versatility, appropriate scale and speed range, accessibility for nonintrusive instrumentation, computerized data systems, and dedicated use for verification were among the more important requirements identified.

  4. Simulation of Tailrace Hydrodynamics Using Computational Fluid Dynamics Models

    SciTech Connect

    Cook, Christopher B.; Richmond, Marshall C.

    2001-05-01

    This report investigates the feasibility of using computational fluid dynamics (CFD) tools to investigate hydrodynamic flow fields surrounding the tailrace zone below large hydraulic structures. Previous and ongoing studies using CFD tools to simulate gradually varied flow with multiple constituents and forebay/intake hydrodynamics have shown that CFD tools can provide valuable information for hydraulic and biological evaluation of fish passage near hydraulic structures. These studies however are incapable of simulating the rapidly varying flow fields that involving breakup of the free-surface, such as those through and below high flow outfalls and spillways. Although the use of CFD tools for these types of flow are still an active area of research, initial applications discussed in this report show that these tools are capable of simulating the primary features of these highly transient flow fields.

  5. Dynamics of dissolved gas in a cavitating fluid

    NASA Astrophysics Data System (ADS)

    Mastikhin, Igor V.; Newling, Benedict

    2008-12-01

    A strong acoustic field in a liquid separates the liquid and dissolved gases by the formation of bubbles (cavitation). Bubble growth and collapse is the result of active exchange of gas and vapor through the bubble walls with the surrounding liquid. This paper details a new approach to the study of cavitation, not as an evolution of discrete bubbles, but as the dynamics of molecules constituting both the bubbles and the fluid. We show, by direct, independent measurement of the liquid and the dissolved gas, that the motions of dissolved gas (freon-22, CHClF2 ) and liquid (water) can be quite different during acoustic cavitation and are strongly affected by filtration or previous cavitation of the solvent. Our observations suggest that bubbles can completely refresh their content within two acoustic cycles and that long-lived (˜minutes) microbubbles act as nucleation sites for cavitation. This technique is complementary to the traditional optical and acoustical techniques.

  6. Parallel Computational Fluid Dynamics: Current Status and Future Requirements

    NASA Technical Reports Server (NTRS)

    Simon, Horst D.; VanDalsem, William R.; Dagum, Leonardo; Kutler, Paul (Technical Monitor)

    1994-01-01

    One or the key objectives of the Applied Research Branch in the Numerical Aerodynamic Simulation (NAS) Systems Division at NASA Allies Research Center is the accelerated introduction of highly parallel machines into a full operational environment. In this report we discuss the performance results obtained from the implementation of some computational fluid dynamics (CFD) applications on the Connection Machine CM-2 and the Intel iPSC/860. We summarize some of the experiences made so far with the parallel testbed machines at the NAS Applied Research Branch. Then we discuss the long term computational requirements for accomplishing some of the grand challenge problems in computational aerosciences. We argue that only massively parallel machines will be able to meet these grand challenge requirements, and we outline the computer science and algorithm research challenges ahead.

  7. Computational fluid dynamic analysis of hybrid rocket combustor flowfields

    NASA Technical Reports Server (NTRS)

    Venkateswaran, S.; Merkle, C. L.

    1995-01-01

    Computational fluid dynamic analyses of the Navier-Stokes equations coupled with solid-phase pyrolysis, gas-phase combustion, turbulence and radiation are performed to study hybrid rocket combustor flowfields. The computational study is closely co-ordinated with a companion experimental program using a planar slab burner configuration with HTPB as fuel and gaseous oxygen. Computational predictions agree reasonably well with measurement data of fuel regression rates and surface temperatures. Additionally, most of the parametric trends predicted by the model are in general agreement with experimental trends. The computational model is applied to extend the results from the lab-scale to a full-scale axisymmetric configuration. The numerical predictions indicate that the full-scale configuration burns at a slower rate than the lab-scale combustor under identical specific flow rate conditions. The results demonstrate that detailed CFD analyses can play a useful role in the design of hybrid combustors.

  8. Mapping flow distortion on oceanographic platforms using computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    O'Sullivan, N.; Landwehr, S.; Ward, B.

    2013-10-01

    Wind speed measurements over the ocean on ships or buoys are affected by flow distortion from the platform and by the anemometer itself. This can lead to errors in direct measurements and the derived parametrisations. Here we computational fluid dynamics (CFD) to simulate the errors in wind speed measurements caused by flow distortion on the RV Celtic Explorer. Numerical measurements were obtained from the finite-volume CFD code OpenFOAM, which was used to simulate the velocity fields. This was done over a range of orientations in the test domain from -60 to +60° in increments of 10°. The simulation was also set up for a range of velocities, ranging from 5 to 25 m s-1 in increments of 0.5 m s-1. The numerical analysis showed close agreement to experimental measurements.

  9. Dynamic response of shear thickening fluid under laser induced shock

    SciTech Connect

    Wu, Xianqian Yin, Qiuyun; Huang, Chenguang; Zhong, Fachun

    2015-02-16

    The dynamic response of the 57 vol./vol. % dense spherical silica particle-polyethylene glycol suspension at high pressure was investigated through short pulsed laser induced shock experiments. The measured back free surface velocities by a photonic Doppler velocimetry showed that the shock and the particle velocities decreased while the shock wave transmitted in the shear thickening fluid (STF), from which an equation of state for the STF was obtained. In addition, the peak stress decreased and the absorbed energy increased rapidly with increasing the thickness for a thin layer of the STF, which should be attributed to the impact-jammed behavior through compression of particle matrix, the deformation or crack of the hard-sphere particles, and the volume compression of the particles and the polyethylene glycol.

  10. Knowledge-based zonal grid generation for computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Andrews, Alison E.

    1988-01-01

    Automation of flow field zoning in two dimensions is an important step towards reducing the difficulty of three-dimensional grid generation in computational fluid dynamics. Using a knowledge-based approach makes sense, but problems arise which are caused by aspects of zoning involving perception, lack of expert consensus, and design processes. These obstacles are overcome by means of a simple shape and configuration language, a tunable zoning archetype, and a method of assembling plans from selected, predefined subplans. A demonstration system for knowledge-based two-dimensional flow field zoning has been successfully implemented and tested on representative aerodynamic configurations. The results show that this approach can produce flow field zonings that are acceptable to experts with differing evaluation criteria.

  11. Dynamics of nanoparticles in fluids and at interfaces

    NASA Astrophysics Data System (ADS)

    Chen, Weikang

    In this thesis, we use molecular dynamics simulation to study three basic behaviors or properties of nanoparticles: deposition during droplets evaporation, slip boundary condition and Brownian motion. These three problems address the need for an in-depth understanding of the dynamics of nanoparticles in fluids and at interfaces. In the first problem, evaporation of the droplets dispersed with particles, we investigated the distribution of evaporative flux, inner flow field, density and temperature. And we use these numerical experiments to check on our hydrodynamic theory of the "coffee ring" phenomenon. The simulations reveal the connection between the particle interactions and the deposit structure, and indicate some limitations in continuum modeling. In the second problem, we explore the slip boundary conditions for curved surfaces, which is one of the desired information in modeling the hydrodynamics of micro-fluidic objects. The conclusion we draw is strong: the slip length, defined in a consistent tensorial manner, depends only on the physical properties of the solid and fluid involved and does not vary with the flow configuration. The final part is devoted to the Brownian motion of Janus particle, where we use a simple model to explain the increase of diffusivity of self-propelling Janus particles. We also show that the hydrodynamic image could be used to account for the self-aligning phenomenon at liquid-solid interfaces. The coupling between the translation and rotation is investigated by Brownian simulation, where we modify the standard Langevin equation with coupling terms which derive from the hydrodynamic interaction with the liquid-solid interfaces. The resultant individual trajectories and their diffusivities are consistent with both the laboratory observations and theoretical calculations.

  12. Computational and Spectroscopic Investigations of the Molecular Scale Structure and Dynamics of Geologically Important Fluids and Mineral-Fluid Interfaces

    SciTech Connect

    R. James Kirkpatrick; Andrey G. Kalinichev

    2008-11-25

    Research supported by this grant focuses on molecular scale understanding of central issues related to the structure and dynamics of geochemically important fluids, fluid-mineral interfaces, and confined fluids using computational modeling and experimental methods. Molecular scale knowledge about fluid structure and dynamics, how these are affected by mineral surfaces and molecular-scale (nano-) confinement, and how water molecules and dissolved species interact with surfaces is essential to understanding the fundamental chemistry of a wide range of low-temperature geochemical processes, including sorption and geochemical transport. Our principal efforts are devoted to continued development of relevant computational approaches, application of these approaches to important geochemical questions, relevant NMR and other experimental studies, and application of computational modeling methods to understanding the experimental results. The combination of computational modeling and experimental approaches is proving highly effective in addressing otherwise intractable problems. In 2006-2007 we have significantly advanced in new, highly promising research directions along with completion of on-going projects and final publication of work completed in previous years. New computational directions are focusing on modeling proton exchange reactions in aqueous solutions using ab initio molecular dynamics (AIMD), metadynamics (MTD), and empirical valence bond (EVB) approaches. Proton exchange is critical to understanding the structure, dynamics, and reactivity at mineral-water interfaces and for oxy-ions in solution, but has traditionally been difficult to model with molecular dynamics (MD). Our ultimate objective is to develop this capability, because MD is much less computationally demanding than quantum-chemical approaches. We have also extended our previous MD simulations of metal binding to natural organic matter (NOM) to a much longer time scale (up to 10 ns) for

  13. Studying microstructural dynamics of complex fluids with particle tracking microrheology

    NASA Astrophysics Data System (ADS)

    Breedveld, Victor

    2004-11-01

    Over the last decade, particle tracking microrheology has matured as a new tool for complex fluids research. The main advantages of microrheology over traditional macroscopic rheometry are: the required sample size is extremely small ( ˜ 1 microliter); local viscoelastic properties in a sample can be probed with high spatial resolution ( ˜1-10 micrometer); and the sample is not disturbed by moving rheometer parts. I will present two examples of recent work in my group that highlight how these characteristics can be exploited to acquire unique information about the microstructure of complex fluids. First, we have studied protein unfolding. Traditionally, protein unfolding is studied with spectroscopic techniques (circular dichroism, NMR, fluorescence). Although viscosity has been listed in textbooks as a suitable technique, few -if any- quantitative rheological studies of unfolding have been reported, mainly due to technical difficulties. With microrheology, we have been able to quantify the size of the folded and unfolded protein, as well as the Gibbs free energy of unfolding, for aqueous bovine serum albumine solutions upon addition of urea as a denaturant. The results are in excellent agreement with literature data. Secondly, we have developed new technology for studying the microstructural dynamics of solvent-responsive complex fluids. In macroscopic rheometry it is virtually impossible to change solvent composition and measure the rheological response of a sample. By integrating microfluidics and microrheology we have been able to overcome this barrier: due to the micrometer lengthscales in microfluidiv devices, diffusive timescales in a dialysis set-up become short enough to achieve rapid and reversible changes in sample composition, without affecting the concentration of macromolecular components. Our dialysis cell for microrheology is a unique tool for studying the dynamics of structural and rheological changes induced by solvent composition. I will

  14. CCM Continuity Constraint Method: A finite-element computational fluid dynamics algorithm for incompressible Navier-Stokes fluid flows

    SciTech Connect

    Williams, P.T.

    1993-09-01

    As the field of computational fluid dynamics (CFD) continues to mature, algorithms are required to exploit the most recent advances in approximation theory, numerical mathematics, computing architectures, and hardware. Meeting this requirement is particularly challenging in incompressible fluid mechanics, where primitive-variable CFD formulations that are robust, while also accurate and efficient in three dimensions, remain an elusive goal. This dissertation asserts that one key to accomplishing this goal is recognition of the dual role assumed by the pressure, i.e., a mechanism for instantaneously enforcing conservation of mass and a force in the mechanical balance law for conservation of momentum. Proving this assertion has motivated the development of a new, primitive-variable, incompressible, CFD algorithm called the Continuity Constraint Method (CCM). The theoretical basis for the CCM consists of a finite-element spatial semi-discretization of a Galerkin weak statement, equal-order interpolation for all state-variables, a 0-implicit time-integration scheme, and a quasi-Newton iterative procedure extended by a Taylor Weak Statement (TWS) formulation for dispersion error control. Original contributions to algorithmic theory include: (a) formulation of the unsteady evolution of the divergence error, (b) investigation of the role of non-smoothness in the discretized continuity-constraint function, (c) development of a uniformly H{sup 1} Galerkin weak statement for the Reynolds-averaged Navier-Stokes pressure Poisson equation, (d) derivation of physically and numerically well-posed boundary conditions, and (e) investigation of sparse data structures and iterative methods for solving the matrix algebra statements generated by the algorithm.

  15. APS presents prizes in fluid dynamics and plasma physics

    SciTech Connect

    Not Available

    1992-12-01

    This article reviews the presentation of the American Physical Society awards in fluid dynamics and plasma physics. The recipient of the plasma physics James Clerk Maxwell Prize was John M. Green for contributions to the theory of magnetohydrodynamics equilibria and ideal and resistive instabilities, for discovering the inverse scattering transform leading to soliton solutions of many nonlinear partial differential equations and for inventing the residue method of determining the transition to global chaos. The excellence in Plasma Physics Research Award was presented to Nathaniel A. Fisch for theoretical investigations of noninductive current generation in toroidally confined plasma. Wim Pieter Leemans received the Simon Ramo Award for experimental and simulational contributions to laser-plasma physics. William R. Sears was given the 1992 Fuid Dynamics Prize for contributions to the study of steady and unsteady aerodynamics, aeroacoustics, magnetoaerodynamics,and wind tunnel design. William C. Reynolds received the Otto Laporte Award for experimental, theoretical, and computational work in turbulence modeling and control and leadership in direct numerical simulation and large eddy simulation.

  16. Molecular dynamics simulations: advances and applications

    PubMed Central

    Hospital, Adam; Goñi, Josep Ramon; Orozco, Modesto; Gelpí, Josep L

    2015-01-01

    Molecular dynamics simulations have evolved into a mature technique that can be used effectively to understand macromolecular structure-to-function relationships. Present simulation times are close to biologically relevant ones. Information gathered about the dynamic properties of macromolecules is rich enough to shift the usual paradigm of structural bioinformatics from studying single structures to analyze conformational ensembles. Here, we describe the foundations of molecular dynamics and the improvements made in the direction of getting such ensemble. Specific application of the technique to three main issues (allosteric regulation, docking, and structure refinement) is discussed. PMID:26604800

  17. Molecular dynamics simulations: advances and applications

    PubMed Central

    Hospital, Adam; Goñi, Josep Ramon; Orozco, Modesto; Gelpí, Josep L

    2015-01-01

    Molecular dynamics simulations have evolved into a mature technique that can be used effectively to understand macromolecular structure-to-function relationships. Present simulation times are close to biologically relevant ones. Information gathered about the dynamic properties of macromolecules is rich enough to shift the usual paradigm of structural bioinformatics from studying single structures to analyze conformational ensembles. Here, we describe the foundations of molecular dynamics and the improvements made in the direction of getting such ensemble. Specific application of the technique to three main issues (allosteric regulation, docking, and structure refinement) is discussed.

  18. A Combined Geometric Approach for Computational Fluid Dynamics on Dynamic Grids

    NASA Technical Reports Server (NTRS)

    Slater, John W.

    1995-01-01

    A combined geometric approach for computational fluid dynamics is presented for the analysis of unsteady flow about mechanisms in which its components are in moderate relative motion. For a CFD analysis, the total dynamics problem involves the dynamics of the aspects of geometry modeling, grid generation, and flow modeling. The interrelationships between these three aspects allow for a more natural formulation of the problem and the sharing of information which can be advantageous to the computation of the dynamics. The approach is applied to planar geometries with the use of an efficient multi-block, structured grid generation method to compute unsteady, two-dimensional and axisymmetric flow. The applications presented include the computation of the unsteady, inviscid flow about a hinged-flap with flap deflections and a high-speed inlet with centerbody motion as part of the unstart / restart operation.

  19. Dynamic Inlet Distortion Prediction with a Combined Computational Fluid Dynamics and Distortion Synthesis Approach

    NASA Technical Reports Server (NTRS)

    Norby, W. P.; Ladd, J. A.; Yuhas, A. J.

    1996-01-01

    A procedure has been developed for predicting peak dynamic inlet distortion. This procedure combines Computational Fluid Dynamics (CFD) and distortion synthesis analysis to obtain a prediction of peak dynamic distortion intensity and the associated instantaneous total pressure pattern. A prediction of the steady state total pressure pattern at the Aerodynamic Interface Plane is first obtained using an appropriate CFD flow solver. A corresponding inlet turbulence pattern is obtained from the CFD solution via a correlation linking root mean square (RMS) inlet turbulence to a formulation of several CFD parameters representative of flow turbulence intensity. This correlation was derived using flight data obtained from the NASA High Alpha Research Vehicle flight test program and several CFD solutions at conditions matching the flight test data. A distortion synthesis analysis is then performed on the predicted steady state total pressure and RMS turbulence patterns to yield a predicted value of dynamic distortion intensity and the associated instantaneous total pressure pattern.

  20. High Order Approximations for Compressible Fluid Dynamics on Unstructured and Cartesian Meshes

    NASA Technical Reports Server (NTRS)

    Barth, Timothy (Editor); Deconinck, Herman (Editor)

    1999-01-01

    The development of high-order accurate numerical discretization techniques for irregular domains and meshes is often cited as one of the remaining challenges facing the field of computational fluid dynamics. In structural mechanics, the advantages of high-order finite element approximation are widely recognized. This is especially true when high-order element approximation is combined with element refinement (h-p refinement). In computational fluid dynamics, high-order discretization methods are infrequently used in the computation of compressible fluid flow. The hyperbolic nature of the governing equations and the presence of solution discontinuities makes high-order accuracy difficult to achieve. Consequently, second-order accurate methods are still predominately used in industrial applications even though evidence suggests that high-order methods may offer a way to significantly improve the resolution and accuracy for these calculations. To address this important topic, a special course was jointly organized by the Applied Vehicle Technology Panel of NATO's Research and Technology Organization (RTO), the von Karman Institute for Fluid Dynamics, and the Numerical Aerospace Simulation Division at the NASA Ames Research Center. The NATO RTO sponsored course entitled "Higher Order Discretization Methods in Computational Fluid Dynamics" was held September 14-18, 1998 at the von Karman Institute for Fluid Dynamics in Belgium and September 21-25, 1998 at the NASA Ames Research Center in the United States. During this special course, lecturers from Europe and the United States gave a series of comprehensive lectures on advanced topics related to the high-order numerical discretization of partial differential equations with primary emphasis given to computational fluid dynamics (CFD). Additional consideration was given to topics in computational physics such as the high-order discretization of the Hamilton-Jacobi, Helmholtz, and elasticity equations. This volume consists

  1. Dynamics of a fluid flow on Mars: Lava or mud?

    NASA Astrophysics Data System (ADS)

    Wilson, Lionel; Mouginis-Mark, Peter J.

    2014-05-01

    A distinctive flow deposit southwest of Cerberus Fossae on Mars is analyzed. The flow source is a ∼20 m deep, ∼12 × 1.5 km wide depression within a yardang associated with the Medusae Fossae Formation. The flow traveled for ∼40 km following topographic lows to leave a deposit on average 3-4 km wide. The surface morphology of the deposit suggests that it was produced by the emplacement of a fluid flowing in a laminar fashion and possessing a finite yield strength. We use topographic data from a digital elevation model (DEM) to model the dynamics of the motion and infer that the fluid had a Bingham rheology with a plastic viscosity of ∼1 Pa s and a yield strength of ∼185 Pa. Although the low viscosity is consistent with the properties of komatiite-like lava, the combination of values of viscosity and yield strength, as well as the surface morphology of the flow, suggests that this was a mud flow. Comparison with published experimental data implies a solids content close to 60% by volume and a grain size dominated by silt-size particles. Comparison of the ∼1.5 km3 deposit volume with the ∼0.03 km3 volume of the source depression implies that ∼98% of the flow material was derived from depth in the crust. There are similarities between the deposit studied here, which we infer to be mud, and other flow deposits on Mars currently widely held to be lavas. This suggests that a re-appraisal of many of these deposits is now in order.

  2. Code Verification of the HIGRAD Computational Fluid Dynamics Solver

    SciTech Connect

    Van Buren, Kendra L.; Canfield, Jesse M.; Hemez, Francois M.; Sauer, Jeremy A.

    2012-05-04

    The purpose of this report is to outline code and solution verification activities applied to HIGRAD, a Computational Fluid Dynamics (CFD) solver of the compressible Navier-Stokes equations developed at the Los Alamos National Laboratory, and used to simulate various phenomena such as the propagation of wildfires and atmospheric hydrodynamics. Code verification efforts, as described in this report, are an important first step to establish the credibility of numerical simulations. They provide evidence that the mathematical formulation is properly implemented without significant mistakes that would adversely impact the application of interest. Highly accurate analytical solutions are derived for four code verification test problems that exercise different aspects of the code. These test problems are referred to as: (i) the quiet start, (ii) the passive advection, (iii) the passive diffusion, and (iv) the piston-like problem. These problems are simulated using HIGRAD with different levels of mesh discretization and the numerical solutions are compared to their analytical counterparts. In addition, the rates of convergence are estimated to verify the numerical performance of the solver. The first three test problems produce numerical approximations as expected. The fourth test problem (piston-like) indicates the extent to which the code is able to simulate a 'mild' discontinuity, which is a condition that would typically be better handled by a Lagrangian formulation. The current investigation concludes that the numerical implementation of the solver performs as expected. The quality of solutions is sufficient to provide credible simulations of fluid flows around wind turbines. The main caveat associated to these findings is the low coverage provided by these four problems, and somewhat limited verification activities. A more comprehensive evaluation of HIGRAD may be beneficial for future studies.

  3. A Finite Element Method for Free-Surface Flows of Incompressible Fluids in Three Dimensions, Part II: Dynamic Wetting Lines

    SciTech Connect

    Baer, T.A.; Cairncross, R.A.; Rao, R.R.; Sackinger, P.A.; Schunk, P.R.

    1999-01-29

    To date, few researchers have solved three-dimensional free-surface problems with dynamic wetting lines. This paper extends the free-surface finite element method described in a companion paper [Cairncross, R.A., P.R. Schunk, T.A. Baer, P.A. Sackinger, R.R. Rao, "A finite element method for free surface flows of incompressible fluid in three dimensions, Part I: Boundary-Fitted mesh motion.", to be published (1998)] to handle dynamic wetting. A generalization of the technique used in two dimensional modeling to circumvent double-valued velocities at the wetting line, the so-called kinematic paradox, is presented for a wetting line in three dimensions. This approach requires the fluid velocity normal to the contact line to be zero, the fluid velocity tangent to the contact line to be equal to the tangential component of web velocity, and the fluid velocity into the web to be zero. In addition, slip is allowed in a narrow strip along the substrate surface near the dynamic contact line. For realistic wetting-line motion, a contact angle which varies with wetting speed is required because contact lines in three dimensions typically advance or recede a different rates depending upon location and/or have both advancing and receding portions. The theory is applied to capillary rise of static fluid in a corner, the initial motion of a Newtonian droplet down an inclined plane, and extrusion of a Newtonian fluid from a nozzle onto a moving substrate. The extrusion results are compared to experimental visualization. Subject Categories

  4. Recent advances in symmetric and network dynamics.

    PubMed

    Golubitsky, Martin; Stewart, Ian

    2015-09-01

    We summarize some of the main results discovered over the past three decades concerning symmetric dynamical systems and networks of dynamical systems, with a focus on pattern formation. In both of these contexts, extra constraints on the dynamical system are imposed, and the generic phenomena can change. The main areas discussed are time-periodic states, mode interactions, and non-compact symmetry groups such as the Euclidean group. We consider both dynamics and bifurcations. We summarize applications of these ideas to pattern formation in a variety of physical and biological systems, and explain how the methods were motivated by transferring to new contexts René Thom's general viewpoint, one version of which became known as "catastrophe theory." We emphasize the role of symmetry-breaking in the creation of patterns. Topics include equivariant Hopf bifurcation, which gives conditions for a periodic state to bifurcate from an equilibrium, and the H/K theorem, which classifies the pairs of setwise and pointwise symmetries of periodic states in equivariant dynamics. We discuss mode interactions, which organize multiple bifurcations into a single degenerate bifurcation, and systems with non-compact symmetry groups, where new technical issues arise. We transfer many of the ideas to the context of networks of coupled dynamical systems, and interpret synchrony and phase relations in network dynamics as a type of pattern, in which space is discretized into finitely many nodes, while time remains continuous. We also describe a variety of applications including animal locomotion, Couette-Taylor flow, flames, the Belousov-Zhabotinskii reaction, binocular rivalry, and a nonlinear filter based on anomalous growth rates for the amplitude of periodic oscillations in a feed-forward network. PMID:26428565

  5. Recent advances in symmetric and network dynamics

    NASA Astrophysics Data System (ADS)

    Golubitsky, Martin; Stewart, Ian

    2015-09-01

    We summarize some of the main results discovered over the past three decades concerning symmetric dynamical systems and networks of dynamical systems, with a focus on pattern formation. In both of these contexts, extra constraints on the dynamical system are imposed, and the generic phenomena can change. The main areas discussed are time-periodic states, mode interactions, and non-compact symmetry groups such as the Euclidean group. We consider both dynamics and bifurcations. We summarize applications of these ideas to pattern formation in a variety of physical and biological systems, and explain how the methods were motivated by transferring to new contexts René Thom's general viewpoint, one version of which became known as "catastrophe theory." We emphasize the role of symmetry-breaking in the creation of patterns. Topics include equivariant Hopf bifurcation, which gives conditions for a periodic state to bifurcate from an equilibrium, and the H/K theorem, which classifies the pairs of setwise and pointwise symmetries of periodic states in equivariant dynamics. We discuss mode interactions, which organize multiple bifurcations into a single degenerate bifurcation, and systems with non-compact symmetry groups, where new technical issues arise. We transfer many of the ideas to the context of networks of coupled dynamical systems, and interpret synchrony and phase relations in network dynamics as a type of pattern, in which space is discretized into finitely many nodes, while time remains continuous. We also describe a variety of applications including animal locomotion, Couette-Taylor flow, flames, the Belousov-Zhabotinskii reaction, binocular rivalry, and a nonlinear filter based on anomalous growth rates for the amplitude of periodic oscillations in a feed-forward network.

  6. Fluid and deformation regime of an advancing subduction system at Marlborough, New Zealand.

    PubMed

    Wannamaker, Philip E; Caldwell, T Grant; Jiracek, George R; Maris, Virginie; Hill, Graham J; Ogawa, Yasuo; Bibby, Hugh M; Bennie, Stewart L; Heise, Wiebke

    2009-08-01

    Newly forming subduction zones on Earth can provide insights into the evolution of major fault zone geometries from shallow levels to deep in the lithosphere and into the role of fluids in element transport and in promoting rock failure by several modes. The transpressional subduction regime of New Zealand, which is advancing laterally to the southwest below the Marlborough strike-slip fault system of the northern South Island, is an ideal setting in which to investigate these processes. Here we acquired a dense, high-quality transect of magnetotelluric soundings across the system, yielding an electrical resistivity cross-section to depths beyond 100 km. Our data imply three distinct processes connecting fluid generation along the upper mantle plate interface to rock deformation in the crust as the subduction zone develops. Massive fluid release just inland of the trench induces fault-fracture meshes through the crust above that undoubtedly weaken it as regional shear initiates. Narrow strike-slip faults in the shallow brittle regime of interior Marlborough diffuse in width upon entering the deeper ductile domain aided by fluids and do not project as narrow deformation zones. Deep subduction-generated fluids rise from 100 km or more and invade upper crustal seismogenic zones that have exhibited historic great earthquakes on high-angle thrusts that are poorly oriented for failure under dry conditions. The fluid-deformation connections described in our work emphasize the need to include metamorphic and fluid transport processes in geodynamic models. PMID:19661914

  7. Fluid and deformation regime of an advancing subduction system at Marlborough, New Zealand.

    PubMed

    Wannamaker, Philip E; Caldwell, T Grant; Jiracek, George R; Maris, Virginie; Hill, Graham J; Ogawa, Yasuo; Bibby, Hugh M; Bennie, Stewart L; Heise, Wiebke

    2009-08-01

    Newly forming subduction zones on Earth can provide insights into the evolution of major fault zone geometries from shallow levels to deep in the lithosphere and into the role of fluids in element transport and in promoting rock failure by several modes. The transpressional subduction regime of New Zealand, which is advancing laterally to the southwest below the Marlborough strike-slip fault system of the northern South Island, is an ideal setting in which to investigate these processes. Here we acquired a dense, high-quality transect of magnetotelluric soundings across the system, yielding an electrical resistivity cross-section to depths beyond 100 km. Our data imply three distinct processes connecting fluid generation along the upper mantle plate interface to rock deformation in the crust as the subduction zone develops. Massive fluid release just inland of the trench induces fault-fracture meshes through the crust above that undoubtedly weaken it as regional shear initiates. Narrow strike-slip faults in the shallow brittle regime of interior Marlborough diffuse in width upon entering the deeper ductile domain aided by fluids and do not project as narrow deformation zones. Deep subduction-generated fluids rise from 100 km or more and invade upper crustal seismogenic zones that have exhibited historic great earthquakes on high-angle thrusts that are poorly oriented for failure under dry conditions. The fluid-deformation connections described in our work emphasize the need to include metamorphic and fluid transport processes in geodynamic models.

  8. 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.

  9. 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.

  10. [Role of computational fluid dynamics in thoracic aortic diseases research: technical superiority and application prospect].

    PubMed

    Li, Weihao; Shen, Chenyang; Zhang, Xiaoming; Zhang, Tao

    2015-08-01

    Computational fluid dynamics (CFD) technology has the potential to simulate normal or pathologic aortic blood flow changes of mechanical properties and flow field, thereby helping researchers understand and reveal the occurrence, development and prognosis of aortic disease. In aortic diseases research, the initial conditions of CFD numerical simulation has experienced a developed process from idealization (forward engineering), rigid vessel wall, uniform cross-sections, laminar flow and stable blood flow towards personalization (reverse engineering), elastic vessel wall (fluid-solid coupling technique), cone-shaped diminishing cross-sections, turbulent flow, pulsatile blood flow. In this review, the research status, the technical superiority and application prospect of CFD technology were discussed with examples in following three major application areas: (1) dynamics characteristic and mechanical properties in normal thoracic aorta; (2) occurrence, advance and disruptive risk predicting in thoracic aortic aneurysm; (3) therapeutic effect and aneurysmal dilatation simulation in thoracic aortic dissection. For the future, the CFD technology may profoundly put an influence on the awareness to aortic diseases and treatment strategies.

  11. 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.

  12. Advances in fluorescence labeling strategies for dynamic cellular imaging

    PubMed Central

    Dean, Kevin M; Palmer, Amy E

    2014-01-01

    Synergistic advances in optical physics, probe design, molecular biology, labeling techniques and computational analysis have propelled fluorescence imaging into new realms of spatiotemporal resolution and sensitivity. This review aims to discuss advances in fluorescent probes and live-cell labeling strategies, two areas that remain pivotal for future advances in imaging technology. Fluorescent protein– and bio-orthogonal–based methods for protein and RNA imaging are discussed as well as emerging bioengineering techniques that enable their expression at specific genomic loci (for example, CRISPR and TALENs). Important attributes that contribute to the success of each technique are emphasized, providing a guideline for future advances in dynamic live-cell imaging. PMID:24937069

  13. 3D quantification of dynamic fluid-fluid interfaces in porous media with fast x-ray microtomography: A comparison with quasi-equilibrium methods

    NASA Astrophysics Data System (ADS)

    Meisenheimer, D.; Brueck, C. L.; Wildenschild, D.

    2015-12-01

    X-ray microtomography imaging of fluid-fluid interfaces in three-dimensional porous media allows for the testing of thermodynamically derived predictions that seek a unique relationship between capillary pressure, fluid saturation, and specific interfacial area (Pc-Sw-Anw). Previous experimental studies sought to test this functional dependence under quasi-equilibrium conditions (assumed static on the imaging time-scale); however, applying predictive models developed under static conditions for dynamic scenarios can lead to substantial flaws in predicted outcomes. Theory and models developed using dynamic data can be verified using fast x-ray microtomography which allows for the unprecedented measurement of developing interfacial areas, curvatures, and trapping behaviors of fluid phases in three-dimensional systems. We will present results of drainage and imbibition experiments of air and water within a mixture of glass beads. The experiments were performed under both quasi-equilibrium and dynamic conditions at the Advanced Photon Source (APS) at Argonne National Laboratory. Fast x-ray microtomography was achieved by utilizing the high brilliance of the x-ray beam at the APS under pink-beam conditions where the white beam is modified with a 4 mm Al absorber and a 0.8 mrad Pt-coated mirror to eliminate low and high-energy photons, respectively. We present a comparison of the results from the quasi-equilibrium and dynamic experiments in an effort to determine if the Pc-Sw-Anw relationship is comparable under either experimental condition and to add to the discussion on whether the Pc-Sw-Anw relationship is unique as hypothesized by existing theory.

  14. NMR imaging of fluid dynamics in reservoir core.

    PubMed

    Baldwin, B A; Yamanashi, W S

    1988-01-01

    A medical NMR imaging instrument has been modified to image water and oil in reservoir rocks by the construction of a new receiving coil. Both oil and water inside the core produced readily detectable proton NMR signals, while the rock matrix produced no signal. Because of similar T2 NMR relaxation times, the water was doped with a paramagnetic ion, Mn+2, to reduce its T2 relaxation time. This procedure enhanced the separation between the oil and water phases in the resulting images. Sequential measurements, as water imbibed into one end and oil was expelled from the other end of a core plug, produced a series of images which showed the dynamics of the fluids. For water-wet Berea Sandstone a flood front was readily observed, but some of the oil was apparently left behind in small, isolated pockets which were larger than individual pores. After several additional pore volumes of water flowed through the plug the NMR image indicated a homogeneous distribution of oil. The amount of residual oil, as determined from the ratio of NMR intensities, closely approximated the residual oil saturation of fully flooded Berea samples measured by Dean-Stark extraction. A Berea sandstone core treated to make it partially oil-wet, did not show a definitive flood front, but appeared to channel the water around the perimeter of the core plug. The relative ease with which these images were made indicates that NMR imaging can be a useful technique to follow the dynamics of oil and water through a core plug for a variety of production processes.

  15. The Fluid Dynamic Process of Large-scale Mineralization in the Lanping Basin, Yunnan, SW China: Evidence from Fluid Inclusions and Basin Fluid Modeling

    NASA Astrophysics Data System (ADS)

    XUE, Chunji; CHI, Guoxiang; CHEN, Yuchuan; ZENG, Rong; GAO, Yongbao; QING, Hairuo

    The Lanping basin, Yunnan, SW China, is known for the giant Jinding Zn-Pb deposit and the newly-discovered Baiyangping Cu-Co-Ag super-large deposit. With a reserve of ˜ 200 Mt ore grading 6.08% Zn and 1.29% Pb (i.e., a metal reserve of ˜ 15 Mt) hosted in Cretaceous and Tertiary terrestrial rocks, the Jinding deposit is the largest Zn-Pb deposit in China, and also the youngest sediment-hosted and the only continental sediment-hosted super-large Zn-Pb deposit in the world. Differing from the known major types of sediment-hosted Zn-Pb deposits in the world, including SST, MVT and Sedex, the Jinding deposit represents a new type of sediment-hosted Zn-Pb deposits. Most previous studies assumed that the mineralizing fluids were derived from within the basin and the fluid flow was driven by topographic relief under a hydrostatic regime. However, the observations of hydraulic fractures and fluid inclusion data indicate that the mineralizing fluid system was strongly over-pressured. The study of fluid inclusions in sphalerites and associated gangue minerals (quartz, celestite, calcite, and gypsum) shows that homogenization temperatures cluster around 110-150°C, with salinities of 1.6-18.0 wt% NaCl equivalent. The fluid temperature increases with the decrease of salinities during the main ore stages, and there is a systematic westward decrease in temperature and increase in salinity in the Jinding ore district. Fluid pressures as high as (513-1364) × 10 5 Pa are indicated by CO 2-rich fluid inclusions. The basin fluid dynamic modeling results indicate that the overpressures could not have been produced by normal sediment compaction, and the overpressure related to the thrusting may not be enough to explain the high fluid pressures indicated by fluid inclusions. The injection of mantle-derived fluids is likely responsible for the building-up of the high overpressures. The mixing of two types of fluids in a structural-lithologic trap may have been the key dynamic process

  16. 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.

  17. Brownian dynamics simulations of DNA in fluid flow

    NASA Astrophysics Data System (ADS)

    Larson, Ronald

    2002-03-01

    Recent advances in single-molecule imaging methods applied to DNA molecules in flow (Smith and Chu 1998) and advances in computer speed have allowed detailed comparisons to be made between observed and predicted behavior of polymeric DNA molecules in simple flows. These have shown that the conformations and rheology of DNA molecules in bulk solution can be predicted with high accuracy by Brownian dynamics simulations using bead-spring or bead-rod course-grained models (Larson et al. 1999; Hur et al. 2000). A logical next step is to extend these methods to the interactions of flowing DNA polymers with surfaces, which are of importance in the development of microfluidic devices for processing of DNA and other large molecules for genomics, bio-assays, combinatorial polymer science, etc. Using single-molecule experiments and Brownian dynamics simulations we consider isolated DNA molecules near adsorbing and non-adsorbing walls in the presence of a simple shearing flow and in an evaporating droplet. The former flow is predicted to produce highly stretched adsorbed molecules due to the prevalence of end-sticking, following by regular unraveling from one end to the other and laying down of the molecule onto the surface. In the drying-droplet flow, this process is inhibited by the downward convection, which drives the molecule towards the surface, resulting in complete adhesion before unraveling is complete. Experimental studies using surfaces treated with APTES (3-aminopropyltriethoxysilane) to produce strong sticking of DNA confirm the Brownian dynamics predictions for the drying flow containing DNA. In simple shearing flow, an unusual, and unexplained, interaction of DNA with the surface inhibits stretching, at distances as great as 20 microns from the surface. 1) Hur, J.S., Shaqfeh, E.S.G., and Larson, R.G., J. Rheol., 44:713 (2000). 2) Larson, R.G., Hu, H., Smith, D.E., and Chu, S. J. Rheol., 43:267 (1999). 3) Smith, D.E., and Chu, S., Science, 281:1335 (1998).

  18. Air Dispersion Characteristics and Thermal Comparison of Traditional and Fabric Ductwork using Computational Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Andreopoulou, Areti

    This thesis research compares the air dispersion and thermal comfort characteristics of conventional diffuser and fabric-based ductwork systems. Heating, ventilation, and air-conditioning (HVAC) systems in buildings produce and regulate airflow traveling through ductwork. The performance characteristics of conventional ductwork are compared with recent advancements in fabric-based ductwork. Using computational fluid dynamics (CFD) analysis, thermal and air distribution flow patterns are compared between the two types of ductwork and preliminary thermal comfort and efficiency conclusions are drawn. Results of the Air Distribution Performance Index (ADPI) for both ducting systems reflect that, under the given test conditions, the fabric duct system is approximately 23% more comfortable than the traditional diffuser system in terms of air speed flow uniformity into the space, while staying within the Effective Draft Temperature comfort zone of -3 to +2°F.

  19. PArallel Reacting Multiphase FLOw Computational Fluid Dynamic Analysis

    2002-06-01

    PARMFLO is a parallel multiphase reacting flow computational fluid dynamics (CFD) code. It can perform steady or unsteady simulations in three space dimensions. It is intended for use in engineering CFD analysis of industrial flow system components. Its parallel processing capabilities allow it to be applied to problems that use at least an order of magnitude more computational cells than the number that can be used on a typical single processor workstation (about 106 cellsmore » in parallel processing mode versus about io cells in serial processing mode). Alternately, by spreading the work of a CFD problem that could be run on a single workstation over a group of computers on a network, it can bring the runtime down by an order of magnitude or more (typically from many days to less than one day). The software was implemented using the industry standard Message-Passing Interface (MPI) and domain decomposition in one spatial direction. The phases of a flow problem may include an ideal gas mixture with an arbitrary number of chemical species, and dispersed droplet and particle phases. Regions of porous media may also be included within the domain. The porous media may be packed beds, foams, or monolith catalyst supports. With these features, the code is especially suited to analysis of mixing of reactants in the inlet chamber of catalytic reactors coupled to computation of product yields that result from the flow of the mixture through the catalyst coaled support structure.« less

  20. Fluid dynamics at transition regions of enhanced heat transfer channels

    NASA Astrophysics Data System (ADS)

    Case, Jennifer C.; Pohlman, Nicholas A.

    2012-11-01

    Helical wire coil inserts are used to enhance heat transfer in high heat flux cooling channels. Past research using temperature probes has sufficiently proven that wire coils increase heat transfer by factors of three to five through the disruption of the boundary layer in the channels. The coils are passive devices that are inexpensive to manufacture and easily integrate into existing heat exchangers given the limited pressure drop they produce. Most of the fluid mechanics research in flow over helical coils has focused on the dynamics and vortex structure in fully developed regions rather than the short transition region where the enhanced heat transfer is often expected. Understanding how the development of the flow occurs over the axial length of the cooling channel will determine minimum dimensions necessary for enhanced heat transfer. Results of particle-shadow velocimetry (PSV) measurements report on the flow velocities and turbulence that occurs in the transition regions at the beginning of wire coil inserts. The ability to relate parameters such as flow rate, wire diameter, coil pitch, and the total tube length will increase fundamental knowledge and will allow for more efficient heat exchanger designs. Funding provided by NIU's Undergraduate Special Opportunities in Artistry & Research grant program.

  1. Development of new flux splitting schemes. [computational fluid dynamics algorithms

    NASA Technical Reports Server (NTRS)

    Liou, Meng-Sing; Steffen, Christopher J., Jr.

    1992-01-01

    Maximizing both accuracy and efficiency has been the primary objective in designing a numerical algorithm for computational fluid dynamics (CFD). This is especially important for solutions of complex three dimensional systems of Navier-Stokes equations which often include turbulence modeling and chemistry effects. Recently, upwind schemes have been well received for their capability in resolving discontinuities. With this in mind, presented are two new flux splitting techniques for upwind differencing. The first method is based on High-Order Polynomial Expansions (HOPE) of the mass flux vector. The second new flux splitting is based on the Advection Upwind Splitting Method (AUSM). The calculation of the hypersonic conical flow demonstrates the accuracy of the splitting in resolving the flow in the presence of strong gradients. A second series of tests involving the two dimensional inviscid flow over a NACA 0012 airfoil demonstrates the ability of the AUSM to resolve the shock discontinuity at transonic speed. A third case calculates a series of supersonic flows over a circular cylinder. Finally, the fourth case deals with tests of a two dimensional shock wave/boundary layer interaction.

  2. Computational fluid dynamic design of rocket engine pump components

    NASA Technical Reports Server (NTRS)

    Chen, Wei-Chung; Prueger, George H.; Chan, Daniel C.; Eastland, Anthony H.

    1992-01-01

    Integration of computational fluid dynamics (CFD) for design and analysis of turbomachinery components is needed as the requirements of pump performance and reliability become more stringent for the new generation of rocket engine. A fast grid generator, designed specially for centrifugal pump impeller, which allows a turbomachinery designer to use CFD to optimize the component design will be presented. The CFD grid is directly generated from the impeller blade G-H blade coordinates. The grid points are first generated on the meridional plane with the desired clustering near the end walls. This is followed by the marching of grid points from the pressure side of one blade to the suction side of a neighboring blade. This fast grid generator has been used to optimize the consortium pump impeller design. A grid dependency study has been conducted for the consortium pump impeller. Two different grid sizes, one with 10,000 grid points and one with 80,000 grid points were used for the grid dependency study. The effects of grid resolution on the turnaround time, including the grid generation and completion of the CFD analysis, is discussed. The impeller overall mass average performance is compared for different designs. Optimum design is achieved through systematic change of the design parameters. In conclusion, it is demonstrated that CFD can be effectively used not only for flow analysis but also for design and optimization of turbomachinery components.

  3. A hybrid numerical fluid dynamics code for resistive magnetohydrodynamics

    SciTech Connect

    Johnson, Jeffrey

    2006-04-01

    Spasmos is a computational fluid dynamics code that uses two numerical methods to solve the equations of resistive magnetohydrodynamic (MHD) flows in compressible, inviscid, conducting media[1]. The code is implemented as a set of libraries for the Python programming language[2]. It represents conducting and non-conducting gases and materials with uncomplicated (analytic) equations of state. It supports calculations in 1D, 2D, and 3D geometry, though only the 1D configuation has received significant testing to date. Because it uses the Python interpreter as a front end, users can easily write test programs to model systems with a variety of different numerical and physical parameters. Currently, the code includes 1D test programs for hydrodynamics (linear acoustic waves, the Sod weak shock[3], the Noh strong shock[4], the Sedov explosion[5], magnetic diffusion (decay of a magnetic pulse[6], a driven oscillatory "wine-cellar" problem[7], magnetic equilibrium), and magnetohydrodynamics (an advected magnetic pulse[8], linear MHD waves, a magnetized shock tube[9]). Spasmos current runs only in a serial configuration. In the future, it will use MPI for parallel computation.

  4. Computational fluid dynamics modeling of proton exchange membrane fuel cells

    SciTech Connect

    UM,SUKKEE; WANG,C.Y.; CHEN,KEN S.

    2000-02-11

    A transient, multi-dimensional model has been developed to simulate proton exchange membrane (PEM) fuel cells. The model accounts simultaneously for electrochemical kinetics, current distribution, hydrodynamics and multi-component transport. A single set of conservation equations valid for flow channels, gas-diffusion electrodes, catalyst layers and the membrane region are developed and numerically solved using a finite-volume-based computational fluid dynamics (CFD) technique. The numerical model is validated against published experimental data with good agreement. Subsequently, the model is applied to explore hydrogen dilution effects in the anode feed. The predicted polarization cubes under hydrogen dilution conditions are found to be in qualitative agreement with recent experiments reported in the literature. The detailed two-dimensional electrochemical and flow/transport simulations further reveal that in the presence of hydrogen dilution in the fuel stream, hydrogen is depleted at the reaction surface resulting in substantial kinetic polarization and hence a lower current density that is limited by hydrogen transport from the fuel stream to the reaction site.

  5. High-order computational fluid dynamics tools for aircraft design.

    PubMed

    Wang, Z J

    2014-08-13

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items. PMID:25024419

  6. High-order computational fluid dynamics tools for aircraft design.

    PubMed

    Wang, Z J

    2014-08-13

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items.

  7. High-order computational fluid dynamics tools for aircraft design

    PubMed Central

    Wang, Z. J.

    2014-01-01

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items. PMID:25024419

  8. Computational Fluid Dynamics Framework for Turbine Biological Performance Assessment

    SciTech Connect

    Richmond, Marshall C.; Serkowski, John A.; Carlson, Thomas J.; Ebner, Laurie L.; Sick, Mirjam; Cada, G. F.

    2011-05-04

    In this paper, a method for turbine biological performance assessment is introduced to bridge the gap between field and laboratory studies on fish injury and turbine design. Using this method, a suite of biological performance indicators is computed based on simulated data from a computational fluid dynamics (CFD) model of a proposed turbine design. Each performance indicator is a measure of the probability of exposure to a certain dose of an injury mechanism. If the relationship between the dose of an injury mechanism and frequency of injury (dose-response) is known from laboratory or field studies, the likelihood of fish injury for a turbine design can be computed from the performance indicator. By comparing the values of the indicators from various turbine designs, the engineer can identify the more-promising designs. Discussion here is focused on Kaplan-type turbines, although the method could be extended to other designs. Following the description of the general methodology, we will present sample risk assessment calculations based on CFD data from a model of the John Day Dam on the Columbia River in the USA.

  9. Computational Fluid Dynamics Analysis of Flexible Duct Junction Box Design

    SciTech Connect

    Beach, Robert; Prahl, Duncan; Lange, Rich

    2013-12-01

    IBACOS explored the relationships between pressure and physical configurations of flexible duct junction boxes by using computational fluid dynamics (CFD) simulations to predict individual box parameters and total system pressure, thereby ensuring improved HVAC performance. Current Air Conditioning Contractors of America (ACCA) guidance (Group 11, Appendix 3, ACCA Manual D, Rutkowski 2009) allows for unconstrained variation in the number of takeoffs, box sizes, and takeoff locations. The only variables currently used in selecting an equivalent length (EL) are velocity of air in the duct and friction rate, given the first takeoff is located at least twice its diameter away from the inlet. This condition does not account for other factors impacting pressure loss across these types of fittings. For each simulation, the IBACOS team converted pressure loss within a box to an EL to compare variation in ACCA Manual D guidance to the simulated variation. IBACOS chose cases to represent flows reasonably correlating to flows typically encountered in the field and analyzed differences in total pressure due to increases in number and location of takeoffs, box dimensions, and velocity of air, and whether an entrance fitting is included. The team also calculated additional balancing losses for all cases due to discrepancies between intended outlet flows and natural flow splits created by the fitting. In certain asymmetrical cases, the balancing losses were significantly higher than symmetrical cases where the natural splits were close to the targets. Thus, IBACOS has shown additional design constraints that can ensure better system performance.

  10. Numerical simulation of landfill aeration using computational fluid dynamics.

    PubMed

    Fytanidis, Dimitrios K; Voudrias, Evangelos A

    2014-04-01

    The present study is an application of Computational Fluid Dynamics (CFD) to the numerical simulation of landfill aeration systems. Specifically, the CFD algorithms provided by the commercial solver ANSYS Fluent 14.0, combined with an in-house source code developed to modify the main solver, were used. The unsaturated multiphase flow of air and liquid phases and the biochemical processes for aerobic biodegradation of the organic fraction of municipal solid waste were simulated taking into consideration their temporal and spatial evolution, as well as complex effects, such as oxygen mass transfer across phases, unsaturated flow effects (capillary suction and unsaturated hydraulic conductivity), temperature variations due to biochemical processes and environmental correction factors for the applied kinetics (Monod and 1st order kinetics). The developed model results were compared with literature experimental data. Also, pilot scale simulations and sensitivity analysis were implemented. Moreover, simulation results of a hypothetical single aeration well were shown, while its zone of influence was estimated using both the pressure and oxygen distribution. Finally, a case study was simulated for a hypothetical landfill aeration system. Both a static (steadily positive or negative relative pressure with time) and a hybrid (following a square wave pattern of positive and negative values of relative pressure with time) scenarios for the aeration wells were examined. The results showed that the present model is capable of simulating landfill aeration and the obtained results were in good agreement with corresponding previous experimental and numerical investigations.

  11. Computational fluid dynamics for turbomachinery internal air systems.

    PubMed

    Chew, John W; Hills, Nicholas J

    2007-10-15

    Considerable progress in development and application of computational fluid dynamics (CFD) for aeroengine internal flow systems has been made in recent years. CFD is regularly used in industry for assessment of air systems, and the performance of CFD for basic axisymmetric rotor/rotor and stator/rotor disc cavities with radial throughflow is largely understood and documented. Incorporation of three-dimensional geometrical features and calculation of unsteady flows are becoming commonplace. Automation of CFD, coupling with thermal models of the solid components, and extension of CFD models to include both air system and main gas path flows are current areas of development. CFD is also being used as a research tool to investigate a number of flow phenomena that are not yet fully understood. These include buoyancy-affected flows in rotating cavities, rim seal flows and mixed air/oil flows. Large eddy simulation has shown considerable promise for the buoyancy-driven flows and its use for air system flows is expected to expand in the future.

  12. Design of airborne wind turbine and computational fluid dynamics analysis

    NASA Astrophysics Data System (ADS)

    Anbreen, Faiqa

    Wind energy is a promising alternative to the depleting non-renewable sources. The height of the wind turbines becomes a constraint to their efficiency. Airborne wind turbine can reach much higher altitudes and produce higher power due to high wind velocity and energy density. The focus of this thesis is to design a shrouded airborne wind turbine, capable to generate 70 kW to propel a leisure boat with a capacity of 8-10 passengers. The idea of designing an airborne turbine is to take the advantage of higher velocities in the atmosphere. The Solidworks model has been analyzed numerically using Computational Fluid Dynamics (CFD) software StarCCM+. The Unsteady Reynolds Averaged Navier Stokes Simulation (URANS) with K-epsilon turbulence model has been selected, to study the physical properties of the flow, with emphasis on the performance of the turbine and the increase in air velocity at the throat. The analysis has been done using two ambient velocities of 12 m/s and 6 m/s. At 12 m/s inlet velocity, the velocity of air at the turbine has been recorded as 16 m/s. The power generated by the turbine is 61 kW. At inlet velocity of 6 m/s, the velocity of air at turbine increased to 10 m/s. The power generated by turbine is 25 kW.

  13. Benchmarking computational fluid dynamics models for lava flow simulation

    NASA Astrophysics Data System (ADS)

    Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi

    2016-04-01

    Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, and COMSOL. Using the new benchmark scenarios defined in Cordonnier et al. (Geol Soc SP, 2015) as a guide, we model viscous, cooling, and solidifying flows over horizontal and sloping surfaces, topographic obstacles, and digital elevation models of natural topography. We compare model results to analytical theory, analogue and molten basalt experiments, and measurements from natural lava flows. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We can apply these models to reconstruct past lava flows in Hawai'i and Saudi Arabia using parameters assembled from morphology, textural analysis, and eruption observations as natural test cases. Our study highlights the strengths and weaknesses of each code, including accuracy and computational costs, and provides insights regarding code selection.

  14. Experimental methodology for computational fluid dynamics code validation

    SciTech Connect

    Aeschliman, D.P.; Oberkampf, W.L.

    1997-09-01

    Validation of Computational Fluid Dynamics (CFD) codes is an essential element of the code development process. Typically, CFD code validation is accomplished through comparison of computed results to previously published experimental data that were obtained for some other purpose, unrelated to code validation. As a result, it is a near certainty that not all of the information required by the code, particularly the boundary conditions, will be available. The common approach is therefore unsatisfactory, and a different method is required. This paper describes a methodology developed specifically for experimental validation of CFD codes. The methodology requires teamwork and cooperation between code developers and experimentalists throughout the validation process, and takes advantage of certain synergisms between CFD and experiment. The methodology employs a novel uncertainty analysis technique which helps to define the experimental plan for code validation wind tunnel experiments, and to distinguish between and quantify various types of experimental error. The methodology is demonstrated with an example of surface pressure measurements over a model of varying geometrical complexity in laminar, hypersonic, near perfect gas, 3-dimensional flow.

  15. Methodology for computational fluid dynamics code verification/validation

    SciTech Connect

    Oberkampf, W.L.; Blottner, F.G.; Aeschliman, D.P.

    1995-07-01

    The issues of verification, calibration, and validation of computational fluid dynamics (CFD) codes has been receiving increasing levels of attention in the research literature and in engineering technology. Both CFD researchers and users of CFD codes are asking more critical and detailed questions concerning the accuracy, range of applicability, reliability and robustness of CFD codes and their predictions. This is a welcomed trend because it demonstrates that CFD is maturing from a research tool to the world of impacting engineering hardware and system design. In this environment, the broad issue of code quality assurance becomes paramount. However, the philosophy and methodology of building confidence in CFD code predictions has proven to be more difficult than many expected. A wide variety of physical modeling errors and discretization errors are discussed. Here, discretization errors refer to all errors caused by conversion of the original partial differential equations to algebraic equations, and their solution. Boundary conditions for both the partial differential equations and the discretized equations will be discussed. Contrasts are drawn between the assumptions and actual use of numerical method consistency and stability. Comments are also made concerning the existence and uniqueness of solutions for both the partial differential equations and the discrete equations. Various techniques are suggested for the detection and estimation of errors caused by physical modeling and discretization of the partial differential equations.

  16. Fluid dynamic characteristics of monopivot magnetic suspension blood pumps.

    PubMed

    Yamane, T; Nishida, M; Asztalos, B; Tsutsui, T; Jikuya, T

    1997-01-01

    A monopivot magnetic suspension blood pump is a centrifugal pump under development with a magnetic suspension and a ceramic pivot to support the impeller with minimum contact. The pump size has been reduced by implementing a direct impeller drive mechanism in place of a magnetic coupling and motor. Flow visualization studies revealed that high shear, which seems to be closely related to hemolysis, concentrates in boundary layers near the walls. This implies that fluid dynamic shear can be reduced not by widening the gap, but by reducing the impeller velocity. Therefore, compared with the results of the previous semi-open curved vane impeller model, impeller velocity was reduced by 30% with a closed impeller having radial straight vanes, and smaller impeller/housing gaps. The volute shape around the impeller tip was also changed such that the outflow from the impeller enters along the center plane of the volute. To examine the effect of the improvements, hemolysis testing was conducted and found that the newly developed closed impeller model generated a lower level of hemolysis than the previous semi-open impeller model. PMID:9360122

  17. Fluid Dynamics of Competitive Swimming: A Computational Study

    NASA Astrophysics Data System (ADS)

    Mittal, Rajat; Loebbeck, Alfred; Singh, Hersh; Mark, Russell; Wei, Timothy

    2004-11-01

    The dolphin kick is an important component in competitive swimming and is used extensively by swimmers immediately following the starting dive as well as after turns. In this stroke, the swimmer swims about three feet under the water surface and the stroke is executed by performing an undulating wave-like motion of the body that is quite similar to the anguilliform propulsion mode in fish. Despite the relatively simple kinematics of this stoke, considerable variability in style and performance is observed even among Olympic level swimmers. Motivated by this, a joint experimental-numerical study has been initiated to examine the fluid-dynamics of this stroke. The current presentation will describe the computational portion of this study. The computations employ a sharp interface immersed boundary method (IBM) which allows us to simulate flows with complex moving boudnaries on stationary Cartesian grids. 3D body scans of male and female Olympic swimmers have been obtained and these are used in conjuction with high speed videos to recreate a realistic dolphin kick for the IBM solver. Preliminary results from these computations will be presented.

  18. Effect of order fluid models on flue gas streamer dynamics

    NASA Astrophysics Data System (ADS)

    Eichwald, O.; Ducasse, O.; Merbahi, N.; Yousfi, M.; Dubois, D.

    2006-01-01

    The present paper shows that in the case of a micro-discharge modelling using the hydrodynamics assumption, the second order fluid model involving the complete electron momentum conservation equation must be used in order to better quantify the radical formation in a micro-discharge applied to air pollution control. The present results show large differences in the micro-discharge parameters (such as velocity and electron density) between the three tested hydrodynamics models: the classical first order model using the local electric field approximation and two second order models using the local energy approximation with or without the drift-diffusion approximation. The tests have been carried out in the case of a wire-to-plane corona reactor filled with a typical flue gas (76% N2, 12% CO2, 6% O2, 6% H2O) at atmospheric pressure and ambient temperature. The simulation of the micro-discharge dynamics is performed using a 1.5D numerical streamer model coupled with a simple chemical kinetics model involving 31 species (charged and neutral particles in their fundamental or metastable state) reacting following 29 selected chemical reactions.

  19. Introducing Computational Fluid Dynamics Simulation into Olfactory Display

    NASA Astrophysics Data System (ADS)

    Ishida, Hiroshi; Yoshida, Hitoshi; Nakamoto, Takamichi

    An olfactory display is a device that delivers various odors to the user's nose. It can be used to add special effects to movies and games by releasing odors relevant to the scenes shown on the screen. In order to provide high-presence olfactory stimuli to the users, the display must be able to generate realistic odors with appropriate concentrations in a timely manner together with visual and audio playbacks. In this paper, we propose to use computational fluid dynamics (CFD) simulations in conjunction with the olfactory display. Odor molecules released from their source are transported mainly by turbulent flow, and their behavior can be extremely complicated even in a simple indoor environment. In the proposed system, a CFD solver is employed to calculate the airflow field and the odor dispersal in the given environment. An odor blender is used to generate the odor with the concentration determined based on the calculated odor distribution. Experimental results on presenting odor stimuli synchronously with movie clips show the effectiveness of the proposed system.

  20. Fluid dynamics of the freeboard in a fluidized bed reactor

    NASA Astrophysics Data System (ADS)

    Verloop, Willem Cornelis

    1994-05-01

    The present study focuses on the fluid dynamics of the gas-particle freeboard flow, whereas a subsequent study will cover the chemistry. The objective of the present thesis is to increase the insight in the physical processes that govern the freeboard particle flow. Special attention has to be paid to the lateral transport of particles and the often observed phenomenon of a downflowing wall layer of solids, which has not been explained satisfactorily up to now. In order to achieve this, detailed experiments have to be performed which provide data on the local flow structure. In addition, the freeboard flow has to be modeled at least two-dimensionally, incorporating the essential physical processes. The resulting model of the freeboard flow should firstly be capable of predicting the local properties of both the gas flow and the particle flow. This prediction has to serve as a basis for the subsequent modeling of the freeboard chemistry. Secondly, the model should serve as a basis for studying the consequences of the scaling up a fluidized bed installation from lab scale to industrial size.

  1. Fluid Dynamics of a High Aspect-Ratio Jet

    NASA Technical Reports Server (NTRS)

    Munro, Scott E.; Ahuja, K. K.

    2003-01-01

    Circulation control wings are a type of pneumatic high-lift device that have been extensively researched as to their aerodynamic benefits. However, there has been little research into the possible airframe noise reduction benefits of a circulation control wing. The key element of noise is the jet noise associated with the jet sheet emitted from the blowing slot. High aspect-ratio jet acoustic results (aspect-ratios from 100 to 3,000) from a related study showed that the jet noise of this type of jet was proportional to the slot height to the 3/2 power and slot width to the 1/2 power. Fluid dynamic experiments were performed in the present study on the high aspect-ratio nozzle to gain understanding of the flow characteristics in an effort to relate the acoustic results to flow parameters. Single hot-wire experiments indicated that the jet exhaust from the high aspect-ratio nozzle was similar to a 2-d turbulent jet. Two-wire space-correlation measurements were performed to attempt to find a relationship between the slot height of the jet and the length-scale of the flow noise generating turbulence structure. The turbulent eddy convection velocity was also calculated, and was found to vary with the local centerline velocity, and also as a function of the frequency of the eddy.

  2. Fully Threaded Tree for Adaptive Refinement Fluid Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Khokhlov, A. M.

    1997-01-01

    A fully threaded tree (FTT) for adaptive refinement of regular meshes is described. By using a tree threaded at all levels, tree traversals for finding nearest neighbors are avoided. All operations on a tree including tree modifications are O(N), where N is a number of cells, and are performed in parallel. An efficient implementation of the tree is described that requires 2N words of memory. A filtering algorithm for removing high frequency noise during mesh refinement is described. A FTT can be used in various numerical applications. In this paper, it is applied to the integration of the Euler equations of fluid dynamics. An adaptive mesh time stepping algorithm is described in which different time steps are used at different l evels of the tree. Time stepping and mesh refinement are interleaved to avoid extensive buffer layers of fine mesh which were otherwise required ahead of moving shocks. Test examples are presented, and the FTT performance is evaluated. The three dimensional simulation of the interaction of a shock wave and a spherical bubble is carried out that shows the development of azimuthal perturbations on the bubble surface.

  3. The role of computational fluid dynamics (CFD) in hair science.

    PubMed

    Spicka, Peter; Grald, Eric

    2004-01-01

    The use of computational fluid dynamics (CFD) as a virtual prototyping tool is widespread in the consumer packaged goods industry. CFD refers to the calculation on a computer of the velocity, pressure, and temperature and chemical species concentrations within a flowing liquid or gas. Because the performance of manufacturing equipment and product designs can be simulated on the computer, the benefit of using CFD is significant time and cost savings when compared to traditional physical testing methods. CFD has been used to design, scale-up and troubleshoot mixing tanks, spray dryers, heat exchangers and other process equipment. Recently, computer models of the capillary wicking process inside fibrous structures have been added to CFD software. These models have been used to gain a better understanding of the absorbent performance of diapers and feminine protection products. The same models can also be used to represent the movement of shampoo, conditioner, colorants and other products through the hair and scalp. In this paper, we provide an introduction to CFD and show some examples of its application to the manufacture of consumer products. We also provide sonic examples to show the potential of CFD for understanding the performance of products applied to the hair and scalp. PMID:15645102

  4. A hybrid numerical fluid dynamics code for resistive magnetohydrodynamics

    2006-04-01

    Spasmos is a computational fluid dynamics code that uses two numerical methods to solve the equations of resistive magnetohydrodynamic (MHD) flows in compressible, inviscid, conducting media[1]. The code is implemented as a set of libraries for the Python programming language[2]. It represents conducting and non-conducting gases and materials with uncomplicated (analytic) equations of state. It supports calculations in 1D, 2D, and 3D geometry, though only the 1D configuation has received significant testing to date. Becausemore » it uses the Python interpreter as a front end, users can easily write test programs to model systems with a variety of different numerical and physical parameters. Currently, the code includes 1D test programs for hydrodynamics (linear acoustic waves, the Sod weak shock[3], the Noh strong shock[4], the Sedov explosion[5], magnetic diffusion (decay of a magnetic pulse[6], a driven oscillatory "wine-cellar" problem[7], magnetic equilibrium), and magnetohydrodynamics (an advected magnetic pulse[8], linear MHD waves, a magnetized shock tube[9]). Spasmos current runs only in a serial configuration. In the future, it will use MPI for parallel computation.« less

  5. A parallel computational fluid dynamics unstructured grid generator

    NASA Astrophysics Data System (ADS)

    Davis, Deborah E.

    1993-12-01

    This research addressed the development of a parallel computational fluid dynamics unstructured grid generator using Delaunay triangulation. The generator is applied to simple elliptical and cylindrical two-dimensional bodies. The methodologies used included Watson's point insertion algorithm, Holmes and Snyder's point creation algorithm, a discretized surface definition, Anderson's clustering function, and a Laplacian smoother. The first version of the software involved a processor boundary exchange at the end of each iteration with no inter-processor communications during the iterations. The second version used inter-processor communication during each iteration instead of the boundary exchange. Version 1 demonstrated a speedup of 1.8 for some portions of the code, but proved to be unscalable for more than two nodes due to the interdependency of the triangular elements. The results of Version 2 were similar. Two distribution methodologies, a simple 360-degree distribution and recursive spectral bisection (RSB), were examined. For the initial grid distribution, the distribution generated by the RSB code would be similar to the distribution generated by the 360-degree methodology and would require significantly more time to execute.

  6. In-vitro interferometric characterization of dynamic fluid layers on contact lenses

    NASA Astrophysics Data System (ADS)

    Primeau, Brian C.; Greivenkamp, John E.; Sullivan, John J.

    2011-08-01

    The anterior refracting surface of the eye when wearing a contact lens is the thin fluid layer that forms on the surface of the contact lens. Under normal conditions, this fluid layer is less than 10 microns thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens, and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed using a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. The fluid behavior on the contact lens surface is measured, allowing quantitative analysis beyond what typical contact angle or visual inspection methods provide. The interferometer system has measured the formation and break up of fluid layers. Different fluid and contact lens material combinations have been used, and significant fluid layer properties have been observed in some cases. The interferometer is capable of identifying features in the fluid layer less than a micron in depth with a spatial resolution of about ten microns. An area on the contact lens approximately 6 mm wide can be measured with the system. This paper will discuss the interferometer design and analysis methods used. Measurement results of different material and fluid combinations are presented.

  7. Proceedings of the 1985 pressure vessels and piping conference. Volume PVP-98-7. Fluid-structure dynamics

    SciTech Connect

    Ma, D.C.; Moody, F.J.

    1985-01-01

    Fluid-structure dynamics is an important subject in various fields such as nuclear power, petrochemical, offshore, and aerospace industries. The term ''fluid-structure dynamics'' covers the structural response, fluid transients and their interactions (fluid-structure interactions) of fluid-structure systems can be either: (1) fluid contained within structures; or (2) structures surrounded by fluid. Examples of (1) are pressure waves in piping and seismic response of liquid-storage tanks. Examples of (2) are fluid-induced vibration and dynamic response of submerged components. The response of fluid-structure systems can be either vibrational in nature or highly transient depending on the characteristics of external loadings. The aim of this volume is to provide a forum for bringing together recent research activities in various areas of fluid-structure dynamics. It is hoped that this volume will be beneficial for future research and upgrade the current analysis and design methodology of fluid-structure systems under dynamic loadings.

  8. Experience revising an advanced-undergraduate/beginning-graduate fluid mechanics textbook

    NASA Astrophysics Data System (ADS)

    Dowling, David

    2012-11-01

    In the fall of 2009, Elsevier Inc. approached me about taking over as the lead author of the fluid mechanics textbook by P. K. Kundu and I. M. Cohen. I subsequently agreed and this presentation provides the story of the process and the approach taken to revising this fluid mechanics textbook which has been in print for approximately 15 years. The goal of the revision was to produce an excellent textbook for second courses in fluid mechanics taken by advanced undergraduate and beginning graduate students while maintaining the book's appeal to instructors who used prior editions. Thus, I sought to maintain or expand the text's fluid mechanics content, while adjusting the text's tone so that this content might be more readily reached by students who may have had only one prior course in fluid mechanics, or who may not specialize in fluid mechanics but do possess appropriate mathematical skills. The entire revision process involved seven steps: (i) formulating a revision plan that was independently reviewed, (ii) agreeing to a formal contract with deadlines, (iii) revising the text, figures, and front matter, (iv) proof reading and correcting copy-edited text, (v) correcting page proofs, (vi) generating the solutions manual, and (vii) tabulating errata. Formulating and executing the

  9. PREFACE: X Meeting on Recent Advances in the Physics of Fluids and their Applications

    NASA Astrophysics Data System (ADS)

    Saita, Fernando Adolfo; Giavedoni, María Delia

    2009-07-01

    The X Meeting on Recent Advances in Physics of Fluids and Related Applications (Fluids 2008) was held in Santa Fe, Argentina, on 19-21 November 2008. It belongs to a series of meetings that started in 1989 and has continued - except for just one occasion - every other year. Thus, the first meeting took place in the city of Tandil in 1989 followed by three events in the city of La Plata (1991-93-95), Tunuyán (Mendoza) in 1997, Paraná (Entre Rios) in 1999, Buenos Aires in 2001, Tandil in 2003 and Mendoza in 2006. These meetings gather together most of the people working in Fluid Mechanics and related problems in Argentina. The objective of the meetings is to provide a forum to facilitate the interactions between participants in a friendly academic atmosphere. This goal is achieved by means of lectures and technical presentations on different subjects and from different points of view, the only constraint being the current academic/technical interest. Applications usually deal with problems of local interest. In the present meeting a variety of lecture topics were presented, among them we might mention Capillary Hydrodynamics, Wetting, Density Currents, Instabilities, Elastic-Dynamics, Flows in Porous Media, Sediment Transport, Plasma Dynamics, etc. In particular, we would like to highlight the specially invited lectures given by Dr Ramon Cerro (Chemical and Material Engineering Department University of Alabama in Huntsville, USA), Dr David Quéré (Physique et Mécanique des Milieux Hétérogènes ESPCI, FRANCE), Dr Marcelo García (College of Engineering University of Illinois at Urbana-Champaign) and Dr Víctor Calo (Earth and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST) and Institute for Computational Engineering and Sciences (ICES), University of Texas at Austin). In addition, we had 18 invited talks and more than fifty contributions that were presented in poster sessions. On behalf of both the Honorary

  10. Efficient Parallel Kernel Solvers for Computational Fluid Dynamics Applications

    NASA Technical Reports Server (NTRS)

    Sun, Xian-He

    1997-01-01

    Distributed-memory parallel computers dominate today's parallel computing arena. These machines, such as Intel Paragon, IBM SP2, and Cray Origin2OO, have successfully delivered high performance computing power for solving some of the so-called "grand-challenge" problems. Despite initial success, parallel machines have not been widely accepted in production engineering environments due to the complexity of parallel programming. On a parallel computing system, a task has to be partitioned and distributed appropriately among processors to reduce communication cost and to attain load balance. More importantly, even with careful partitioning and mapping, the performance of an algorithm may still be unsatisfactory, since conventional sequential algorithms may be serial in nature and may not be implemented efficiently on parallel machines. In many cases, new algorithms have to be introduced to increase parallel performance. In order to achieve optimal performance, in addition to partitioning and mapping, a careful performance study should be conducted for a given application to find a good algorithm-machine combination. This process, however, is usually painful and elusive. The goal of this project is to design and develop efficient parallel algorithms for highly accurate Computational Fluid Dynamics (CFD) simulations and other engineering applications. The work plan is 1) developing highly accurate parallel numerical algorithms, 2) conduct preliminary testing to verify the effectiveness and potential of these algorithms, 3) incorporate newly developed algorithms into actual simulation packages. The work plan has well achieved. Two highly accurate, efficient Poisson solvers have been developed and tested based on two different approaches: (1) Adopting a mathematical geometry which has a better capacity to describe the fluid, (2) Using compact scheme to gain high order accuracy in numerical discretization. The previously developed Parallel Diagonal Dominant (PDD) algorithm

  11. Workshop on Critical Issues in Microgravity Fluids, Transport, and Reaction Processes in Advanced Human Support Technology

    NASA Technical Reports Server (NTRS)

    Chiaramonte, Francis P.; Joshi, Jitendra A.

    2004-01-01

    This workshop was designed to bring the experts from the Advanced Human Support Technologies communities together to identify the most pressing and fruitful areas of research where success hinges on collaborative research between the two communities. Thus an effort was made to bring together experts in both advanced human support technologies and microgravity fluids, transport and reaction processes. Expertise was drawn from academia, national laboratories, and the federal government. The intent was to bring about a thorough exchange of ideas and develop recommendations to address the significant open design and operation issues for human support systems that are affected by fluid physics, transport and reaction processes. This report provides a summary of key discussions, findings, and recommendations.

  12. Benefits of advanced working fluids for DHC (district heating and cooling) systems

    SciTech Connect

    Choi, U.S.; Kasza, K.E.

    1988-09-01

    DHC projects have positive economic and community development rewards. Today the US DHC industry has moved beyond a market consisting of institutional and military-base systems to community energy systems which cover the central business district and adjoining high density areas as well as communities that need revitalization and new development. One day DHC may be a national industry when DHC is married to electric utilities by recovering waste heat from nuclear or coal power plants (rather than wasting it causing thermal pollution) and supplying heat to customers through the DHC loop as is done in several European countries. These cogenerative DHC systems will make a significant impact on energy conservation and create the most reliable and efficient electric utility systems. The objectives of this paper, are to review the benefits and barriers of conventional DHC technology, introduce the concepts of advanced working fluids and consider the potential benefits of these advanced working fluids for DHC systems. 5 refs.

  13. Subretinal Fluid Drainage and Vitrectomy Are Helpful in Diagnosing and Treating Eyes with Advanced Coats' Disease.

    PubMed

    Imaizumi, Ayako; Kusaka, Shunji; Takaesu, Sugie; Sawaguchi, Shoichi; Shimomura, Yoshikazu

    2016-01-01

    Severe forms of Coats' disease are often associated with total retinal detachment, and a differential diagnosis from retinoblastoma is critically important. In such eyes, laser- and/or cryoablation is often ineffective or sometimes impossible to perform. We report a case of advanced Coats' disease in which a rapid pathological examination of subretinal fluid was effective for the diagnosis, and external subretinal drainage combined with vitrectomy was effective in preserving the eye. PMID:27462247

  14. Subretinal Fluid Drainage and Vitrectomy Are Helpful in Diagnosing and Treating Eyes with Advanced Coats' Disease

    PubMed Central

    Imaizumi, Ayako; Kusaka, Shunji; Takaesu, Sugie; Sawaguchi, Shoichi; Shimomura, Yoshikazu

    2016-01-01

    Severe forms of Coats' disease are often associated with total retinal detachment, and a differential diagnosis from retinoblastoma is critically important. In such eyes, laser- and/or cryoablation is often ineffective or sometimes impossible to perform. We report a case of advanced Coats' disease in which a rapid pathological examination of subretinal fluid was effective for the diagnosis, and external subretinal drainage combined with vitrectomy was effective in preserving the eye. PMID:27462247

  15. Numerical Evaluation of Fluid Mixing Phenomena in Boiling Water Reactor Using Advanced Interface Tracking Method

    NASA Astrophysics Data System (ADS)

    Yoshida, Hiroyuki; Takase, Kazuyuki

    Thermal-hydraulic design of the current boiling water reactor (BWR) is performed with the subchannel analysis codes which incorporated the correlations based on empirical results including actual-size tests. Then, for the Innovative Water Reactor for Flexible Fuel Cycle (FLWR) core, an actual size test of an embodiment of its design is required to confirm or modify such correlations. In this situation, development of a method that enables the thermal-hydraulic design of nuclear reactors without these actual size tests is desired, because these tests take a long time and entail great cost. For this reason, we developed an advanced thermal-hydraulic design method for FLWRs using innovative two-phase flow simulation technology. In this study, a detailed Two-Phase Flow simulation code using advanced Interface Tracking method: TPFIT is developed to calculate the detailed information of the two-phase flow. In this paper, firstly, we tried to verify the TPFIT code by comparing it with the existing 2-channel air-water mixing experimental results. Secondary, the TPFIT code was applied to simulation of steam-water two-phase flow in a model of two subchannels of a current BWRs and FLWRs rod bundle. The fluid mixing was observed at a gap between the subchannels. The existing two-phase flow correlation for fluid mixing is evaluated using detailed numerical simulation data. This data indicates that pressure difference between fluid channels is responsible for the fluid mixing, and thus the effects of the time average pressure difference and fluctuations must be incorporated in the two-phase flow correlation for fluid mixing. When inlet quality ratio of subchannels is relatively large, it is understood that evaluation precision of the existing two-phase flow correlations for fluid mixing are relatively low.

  16. Computational Fluid Dynamics Model for Saltstone Vault 4 Vapor Sapce

    SciTech Connect

    Lee, Si Young

    2005-06-27

    Computational fluid dynamics (CFD) methods have been used to estimate the flow patterns for vapor space inside the Saltstone Vault No.4 under different operating scenarios. The purpose of this work is to examine the gas motions inside the vapor space under the current vault configurations. A CFD model took three-dimensional transient momentum-energy coupled approach for the vapor space domain of the vault. The modeling calculations were based on prototypic vault geometry and expected normal operating conditions as defined by Waste Solidification Engineering. The modeling analysis was focused on the air flow patterns near the ventilated corner zones of the vapor space inside the Saltstone vault. The turbulence behavior and natural convection mechanism used in the present model were benchmarked against the literature information and theoretical results. The verified model was applied to the Saltstone vault geometry for the transient assessment of the air flow patterns inside the vapor space of the vault region using the boundary conditions as provided by the customer. The present model considered two cases for the estimations of the flow patterns within the vapor space. One is the reference baseline case. The other is for the negative temperature gradient between the roof inner and top grout surface temperatures intended for the potential bounding condition. The flow patterns of the vapor space calculated by the CFD model demonstrate that the ambient air comes into the vapor space of the vault through the lower-end ventilation hole, and it gets heated up by the Benard-cell type circulation before leaving the vault via the higher-end ventilation hole. The calculated results are consistent with the literature information.

  17. The Fluid Dynamics of Secondary Cooling Air-Mist Jets

    NASA Astrophysics Data System (ADS)

    Hernández C., I.; Acosta G., F. A.; Castillejos E., A. H.; Minchaca M., J. I.

    2008-10-01

    For the conditions of thin-slab continuous casting, air-mist secondary cooling occurs in the transition-boiling regime, possibly as a result of an enhanced intermittent contact of high- momentum water drops with the hot metallic surface. The dynamics of the intermittent contact or wetting/dewetting process should be primarily dependent on the drop size, drop impact-velocity and -angle and water-impact flux, which results from the nozzle design and the interaction of the drops with the conveying and entrained air stream. The aim of this article was to develop a model for predicting the last three parameters based on the design and operating characteristics of air-mist nozzles and on experimentally determined drop-size distributions. To do this, the Eulerian fluid-flow field of the air in three dimensions and steady state and the Lagrangian velocities and trajectories of water drops were computed by solving the turbulent Navier Stokes equation for the air coupled to the motion equation for the water drops. In setting this model, it was particularly important to specify appropriately the air-velocity profile at the nozzle orifice, as well as, the water-flux distribution, and the velocities (magnitude and angle) and exit positions of drops with the different sizes generated, hence special attention was given to these aspects. The computed drop velocities, water-impact flux distributions, and air-mist impact-pressure fields compared well with detailed laboratory measurements carried out at ambient temperature. The results indicate that under practical nozzle-operating conditions, the impinging-droplet Weber numbers are high, over most of the water footprint, suggesting that the droplets should establish an intimate contact with the solid surface. However, the associated high mean-droplet fluxes hint that this contact may be obstructed by drop interference at the surface, which would undermine the heat-extraction effectiveness of the impinging mist. The model also points

  18. Fluid dynamic and thermodynamic analysis of a model pertaining to cryogenic fluid management in low gravity environments for a system with dynamically induced settling

    NASA Technical Reports Server (NTRS)

    Rios, J.

    1982-01-01

    The settling behavior of the liquid and gaseous phases of a fluid in a propellant and in a zero-g environment, when such settling is induced through the use of a dynamic device, in this particular case, a helical screw was studied. Particular emphasis was given to: (1) the description of a fluid mechanics model which seems applicable to the system under consideration, (2) a First Law of Thermodynamics analysis of the system, and (3) a discussion of applicable scaling rules.

  19. Fluid-Rock Dynamic Interaction in Magmatic Conduits: Modelling Transients Using an Analytical Solution

    NASA Astrophysics Data System (ADS)

    Arciniega-Ceballos, Alejandra; Scheu, Bettina; Sanchez-Sesma, Francisco; Dingwell, Donald

    2014-05-01

    We compute transients fluid-rock dynamic interaction in a fluid driven axisymmetric conduit embedded in an infinite, homogeneous elastic space. Both fluid and solid are dynamically coupled fulfilling continuity of velocities and radial stresses at the conduit's wall. The calculation model considers the viscosity as a key parameter leading to non-linear scheme. A pressure transient at a point of the conduit, that perturbs a steady flow of incompressible viscous fluid, produces the interaction between the fluid and motion at the conduit's walls. The fluid motion induces the elastic response of the conduit forcing it to oscillate radially. The fluid-filled conduit dynamics is governed by three second-order, ordinary non-linear differential equations, which are solved numerically by applying a fifth-order Runge-Kutta scheme. Boundary conditions satisfy the Bernoulli's principle allowing coupling several pipe segments which may present smooth variation in fluid properties. The nature of the source involves different pressure excitations functions including those measuring during simulations of gas burst and fragmentation of volcanic rocks under controlled laboratory conditions. Far-field velocity synthetics radiated by motion of the conduit's walls and fluid flows ascending to the surface, display characteristic waveforms and frequency content that are similar to those of long-period signals and tremor observed at active volcanoes. Results suggest that transient fluid flow induced oscillations may explain long-period and tremor signals. Advantages and limitations of this approach are discussed.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Multidimensional wave packet dynamics within the fluid dynamical formulation of the Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Dey, Bijoy K.; Askar, Attila; Rabitz, H.

    1998-11-01

    This paper explores the quantum fluid dynamical (QFD) representation of the time-dependent Schrödinger equation for the motion of a wave packet in a high dimensional space. A novel alternating direction technique is utilized to single out each of the many dimensions in the QFD equations. This technique is used to solve the continuity equation for the density and the equation for the convection of the flux for the quantum particle. The ability of the present scheme to efficiently and accurately describe the dynamics of a quantum particle is demonstrated in four dimensions where analytical results are known. We also apply the technique to the photodissociation of NOCl and NO2 where the systems are reduced to two coordinates by freezing the angular variable at its equilibrium value.

  5. Dynamic response and stability of a flapping foil in a dense and viscous fluid

    NASA Astrophysics Data System (ADS)

    Chae, Eun Jung; Akcabay, Deniz Tolga; Young, Yin Lu

    2013-10-01

    It is important to understand and accurately predict the static and dynamic response and stability of flexible hydro/aero lifting bodies to ensure their structural safety, to facilitate the design/optimization of new/existing concepts, and to test the feasibility of using advanced materials. The present study investigates the influence of solid-to-fluid added mass ratio (sqrt{μ _b}) and viscous effects on the fluid-structure interaction (FSI) response and stability of a flapping foil in incompressible and turbulent flows using a recently presented efficient and stable numerical algorithm in time-domain, which couples an unsteady Reynolds Average Navier-Stokes solver with a two degrees-of freedom structural model. The new numerical coupling method is able to stably and accurately simulate the FSI behavior of light foils in dense fluids: a limit which is known to be numerically difficult to study with classical FSI coupling methods. The studied FSI responses include static/dynamic divergence and flutter instabilities, which are compared with inviscid, linear potential theory predictions obtained with both time and frequency domain formulations, as well as with several published experimental data. In general, the results show that the critical reduced flutter velocities and reduced divergence velocities both decrease as sqrt{μ _b} decreases, and are captured with good accuracy using the viscous FSI solver for a wide range of relative mass ratios that are typical to air/hydrofoils. The comparative analyses showed that the classic frequency-domain linear potential theory is severely unconservative for predicting the flutter velocity for cases with sqrt{μ _b}<3: this includes the typical operating conditions of most marine and biomedical lifting devices, where the fluid forces are comparable to the solid forces, and strong nonlinear interactions may develop. In addition, the viscous FSI solver is shown to correctly predict the experimentally reported critical

  6. Incorporating geometrically complex vegetation in a computational fluid dynamic framework

    NASA Astrophysics Data System (ADS)

    Boothroyd, Richard; Hardy, Richard; Warburton, Jeff; Rosser, Nick

    2015-04-01

    Vegetation is known to have a significant influence on the hydraulic, geomorphological, and ecological functioning of river systems. Vegetation acts as a blockage to flow, thereby causing additional flow resistance and influencing flow dynamics, in particular flow conveyance. These processes need to be incorporated into flood models to improve predictions used in river management. However, the current practice in representing vegetation in hydraulic models is either through roughness parameterisation or process understanding derived experimentally from flow through highly simplified configurations of fixed, rigid cylinders. It is suggested that such simplifications inadequately describe the geometric complexity that characterises vegetation, and therefore the modelled flow dynamics may be oversimplified. This paper addresses this issue by using an approach combining field and numerical modelling techniques. Terrestrial Laser Scanning (TLS) with waveform processing has been applied to collect a sub-mm, 3-dimensional representation of Prunus laurocerasus, an invasive species to the UK that has been increasingly recorded in riparian zones. Multiple scan perspectives produce a highly detailed point cloud (>5,000,000 individual data points) which is reduced in post processing using an octree-based voxelisation technique. The method retains the geometric complexity of the vegetation by subdividing the point cloud into 0.01 m3 cubic voxels. The voxelised representation is subsequently read into a computational fluid dynamic (CFD) model using a Mass Flux Scaling Algorithm, allowing the vegetation to be directly represented in the modelling framework. Results demonstrate the development of a complex flow field around the vegetation. The downstream velocity profile is characterised by two distinct inflection points. A high velocity zone in the near-bed (plant-stem) region is apparent due to the lack of significant near-bed foliage. Above this, a zone of reduced velocity is

  7. Advanced Ultrasonic Measurement Methodology for Non-Invasive Interrogation and Identification of Fluids in Sealed Containers

    SciTech Connect

    Tucker, Brian J.; Diaz, Aaron A.; Eckenrode, Brian A.

    2006-03-16

    The Hazardous Materials Response Unit (HMRU) and the Counterterrorism and Forensic Science Research Unit (CTFSRU), Laboratory Division, Federal Bureau of Investigation (FBI) have been mandated to develop and establish a wide range of unprecedented capabilities for providing scientific and technical forensic services to investigations involving hazardous chemical, biological, and radiological materials, including extremely dangerous chemical and biological warfare agents. Pacific Northwest National Laboratory (PNNL) has developed a portable, hand-held, hazardous materials acoustic inspection device (HAZAID) that provides noninvasive container interrogation and material identification capabilities using nondestructive ultrasonic velocity and attenuation measurements. Due to the wide variety of fluids as well as container sizes and materials, the need for high measurement sensitivity and advanced ultrasonic measurement techniques were identified. The HAZAID prototype was developed using a versatile electronics platform, advanced ultrasonic wave propagation methods, and advanced signal processing techniques. This paper primarily focuses on the ultrasonic measurement methods and signal processing techniques incorporated into the HAZAID prototype. High bandwidth ultrasonic transducers combined with the advanced pulse compression technique allowed researchers to 1) impart large amounts of energy, 2) obtain high signal-to-noise ratios, and 3) obtain accurate and consistent time-of-flight (TOF) measurements through a variety of highly attenuative containers and fluid media. Results of this feasibility study demonstrated that the HAZAID experimental measurement technique also provided information regarding container properties, which will be utilized in future container-independent measurements of hidden liquids.

  8. Advanced ultrasonic measurement methodology for non-invasive interrogation and identification of fluids in sealed containers

    NASA Astrophysics Data System (ADS)

    Tucker, Brian J.; Diaz, Aaron A.; Eckenrode, Brian A.

    2006-03-01

    Government agencies and homeland security related organizations have identified the need to develop and establish a wide range of unprecedented capabilities for providing scientific and technical forensic services to investigations involving hazardous chemical, biological, and radiological materials, including extremely dangerous chemical and biological warfare agents. Pacific Northwest National Laboratory (PNNL) has developed a prototype portable, hand-held, hazardous materials acoustic inspection prototype that provides noninvasive container interrogation and material identification capabilities using nondestructive ultrasonic velocity and attenuation measurements. Due to the wide variety of fluids as well as container sizes and materials encountered in various law enforcement inspection activities, the need for high measurement sensitivity and advanced ultrasonic measurement techniques were identified. The prototype was developed using a versatile electronics platform, advanced ultrasonic wave propagation methods, and advanced signal processing techniques. This paper primarily focuses on the ultrasonic measurement methods and signal processing techniques incorporated into the prototype. High bandwidth ultrasonic transducers combined with an advanced pulse compression technique allowed researchers to 1) obtain high signal-to-noise ratios and 2) obtain accurate and consistent time-of-flight (TOF) measurements through a variety of highly attenuative containers and fluid media. Results of work conducted in the laboratory have demonstrated that the prototype experimental measurement technique also provided information regarding container properties, which will be utilized in future container-independent measurements of hidden liquids.

  9. Major advances in fresh milk and milk products: fluid milk products and frozen desserts.

    PubMed

    Goff, H D; Griffiths, M W

    2006-04-01

    Major technological advances in the fluid milk processing industry in the last 25 yr include significant improvements in all the unit operations of separation, standardization, pasteurization, homogenization, and packaging. Many advancements have been directed toward production capacity, automation, and hygienic operation. Extended shelf-life milks are produced by high heat treatment, sometimes coupled with microfiltration or centrifugation. Other nonthermal methods have also been investigated. Flavored milk beverages have increased in popularity, as have milk beverages packaged in single-service, closeable plastic containers. Likewise, the frozen dairy processing industry has seen the development of large-capacity, automated processing equipment for a wide range of products designed to gain market share. Significant advancements in product quality have been made, many of these arising from improved knowledge of the functional properties of ingredients and their impact on structure and texture. Incidents of foodborne disease associated with dairy products continue to occur, necessitating even greater diligence in the control of pathogen transmission. Analytical techniques for the rapid detection of specific types of microorganisms have been developed and greatly improved during this time. Despite tremendous technological advancements for processors and a greater diversity of products for consumers, per capita consumption of fluid milk has declined and consumption of frozen dairy desserts has been steady during this 25-yr period.

  10. Advanced ultrasonic measurement methodology for non-invasive interrogation and identification of fluids in sealed containers

    SciTech Connect

    Tucker, Brian J.; Diaz, Aaron A.; Eckenrode, Brian A.

    2006-05-01

    Government agencies and homeland security related organizations have identified the need to develop and establish a wide range of unprecedented capabilities for providing scientific and technical forensic services to investigations involving hazardous chemical, biological, and radiological materials, including extremely dangerous chemical and biological warfare agents. Pacific Northwest National Laboratory (PNNL) has developed a prototype portable, hand-held, hazardous materials acoustic inspection prototype that provides noninvasive container interrogation and material identification capabilities using nondestructive ultrasonic velocity and attenuation measurements. Due to the wide variety of fluids as well as container sizes and materials encountered in various law enforcement inspection activities, the need for high measurement sensitivity and advanced ultrasonic measurement techniques were identified. The prototype was developed using a versatile electronics platform, advanced ultrasonic wave propagation methods, and advanced signal processing techniques. This paper primarily focuses on the ultrasonic measurement methods and signal processing techniques incorporated into the prototype. High bandwidth ultrasonic transducers combined with an advanced pulse compression technique allowed researchers to 1) obtain high signal-to-noise ratios and 2) obtain accurate and consistent time-of-flight (TOF) measurements through a variety of highly attenuative containers and fluid media. Results of work conducted in the laboratory have demonstrated that the prototype experimental measurement technique also provided information regarding container properties, which will be utilized in future container-independent measurements of hidden liquids.

  11. Noncommutative fluid dynamics in the Kähler parametrization

    NASA Astrophysics Data System (ADS)

    Holender, L.; Santos, M. A.; Orlando, M. T. D.; Vancea, I. V.

    2011-11-01

    In this paper, we propose a first-order action functional for a large class of systems that generalize the relativistic perfect fluids in the Kähler parametrization to noncommutative spacetimes. The noncommutative action is parametrized by two arbitrary functions K(z,z¯) and f(-j2) that depend on the fluid potentials and represent the generalization of the Kähler potential of the complex surface parametrized by z and z¯, respectively, and the characteristic function of each model. We calculate the equations of motion for the fluid potentials and the energy-momentum tensor in the first order in the noncommutative parameter. The density current does not receive any noncommutative corrections and it is conserved under the action of the commutative generators Pμ but the energy-momentum tensor is not. Therefore, we determine the set of constraints under which the energy-momentum tensor is divergenceless. Another set of constraints on the fluid potentials is obtained from the requirement of the invariance of the action under the generalization of the volume preserving transformations of the noncommutative spacetime. We show that the proposed action describes noncommutative fluid models by casting the energy-momentum tensor in the familiar fluid form and identifying the corresponding energy and momentum densities. In the commutative limit, they are identical to the corresponding quantities of the relativistic perfect fluids. The energy-momentum tensor contains a dissipative term that is due to the noncommutative spacetime and vanishes in the commutative limit. Finally, we particularize the theory to the case when the complex fluid potentials are characterized by a function K(z,z¯) that is a deformation of the complex plane and show that this model has important common features with the commutative fluid such as infinitely many conserved currents and a conserved axial current that in the commutative case is associated to the topologically conserved linking number.

  12. Anomalous structure and dynamics of the Gaussian-core fluid.

    PubMed

    Krekelberg, William P; Kumar, Tanuj; Mittal, Jeetain; Errington, Jeffrey R; Truskett, Thomas M

    2009-03-01

    It is known that there are thermodynamic states for which the Gaussian-core fluid displays anomalous properties such as expansion upon isobaric cooling (density anomaly) and increased single-particle mobility upon isothermal compression (self-diffusivity anomaly). Here, we investigate how temperature and density affect its short-range translational structural order, as characterized by the two-body excess entropy. We find that there is a wide range of conditions for which the short-range translational order of the Gaussian-core fluid decreases upon isothermal compression (structural order anomaly). As we show, the origin of the structural anomaly is qualitatively similar to that of other anomalous fluids (e.g., water or colloids with short-range attractions) and is connected to how compression affects static correlations at different length scales. Interestingly, we find that the self-diffusivity of the Gaussian-core fluid obeys a scaling relationship with the two-body excess entropy that is very similar to the one observed for a variety of simple liquids. One consequence of this relationship is that the state points for which structural, self-diffusivity, and density anomalies of the Gaussian-core fluid occur appear as cascading regions on the temperature-density plane; a phenomenon observed earlier for models of waterlike fluids. There are, however, key differences between the anomalies of Gaussian-core and waterlike fluids, and we discuss how those can be qualitatively understood by considering the respective interparticle potentials of these models. Finally, we note that the self-diffusivity of the Gaussian-core fluid obeys different scaling laws depending on whether the two-body or total excess entropy is considered. This finding, which deserves more comprehensive future study, appears to underscore the significance of higher-body correlations for the behavior of fluids with bounded interactions. PMID:19391927

  13. Flow study in channel with the use computational fluid dynamics (CFD)

    NASA Astrophysics Data System (ADS)

    Oliveira, W. D.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.

    2016-08-01

    The Computational Fluid Dynamics (CFD) is a tool used to numerically simulate fluid flow behavior, and all the laws that govern the study of fluids is the mass transfer and energy, chemical reactions, hydraulic behaviors, among others applications. This tool mathematical equation solves the problem in a specific manner over a region of interest, with predetermined boundary conditions on this region. This work is to study the flow channel through the CFD technique.

  14. The pathophysiological mechanism of fluid retention in advanced cancer patients treated with docetaxel, but not receiving corticosteroid comedication

    PubMed Central

    Béhar, A.; Pujade-Lauraine, E.; Maurel, A.; Brun, M. D.; Lagrue, G.; Feuilhade De Chauvin, F.; Oulid-Aissa, D.; Hille, D.

    1997-01-01

    Aims Fluid retention is a phenomenon associated with taxoids. The principal objective of this study was to investigate the pathophysiological mechanism of docetaxel-induced fluid retention in advanced cancer patients. Methods Docetaxel was administered as a 1 h intravenous infusion every 3 weeks, for at least 4–6 consecutive cycles, to patients with advanced breast (n=21) or ovarian (n=3) carcinoma, who had received previous chemotherapy, 21 for advanced disease. Phase II clinical trials have shown that 5 day corticosteroid comedication, starting 1 day before docetaxel infusion, significantly reduces the incidence and severity of fluid retention. This prophylactic corticosteroid regimen is currently recommended for patients receiving docetaxel but was not permitted in this study because of its possible interference with the underlying pathophysiology of the fluid retention. Results Fluid retention occurred in 21 of the 24 patients but was mainly mild to moderate, with only five patients experiencing severe fluid retention. Eighteen patients received symptomatic flavonoid treatment, commonly prescribed after the last cycle. Specific investigations for fluid retention confirmed a relationship between cumulative docetaxel dose and development of fluid retention. Capillary filtration test analysis showed a two-step process for fluid retention generation, with progressive congestion of the interstitial space by proteins and water starting between the second and the fourth cycle, followed by insufficient lymphatic drainage. Conclusions A vascular protector such as micronized diosmine hesperidine with recommended corticosteroid premedication and benzopyrones may be useful in preventing and treating docetaxel-induced fluid retention. PMID:9205828

  15. Lessons Learned From Dynamic Simulations of Advanced Fuel Cycles

    SciTech Connect

    Steven J. Piet; Brent W. Dixon; Jacob J. Jacobson; Gretchen E. Matthern; David E. Shropshire

    2009-04-01

    Years of performing dynamic simulations of advanced nuclear fuel cycle options provide insights into how they could work and how one might transition from the current once-through fuel cycle. This paper summarizes those insights from the context of the 2005 objectives and goals of the Advanced Fuel Cycle Initiative (AFCI). Our intent is not to compare options, assess options versus those objectives and goals, nor recommend changes to those objectives and goals. Rather, we organize what we have learned from dynamic simulations in the context of the AFCI objectives for waste management, proliferation resistance, uranium utilization, and economics. Thus, we do not merely describe “lessons learned” from dynamic simulations but attempt to answer the “so what” question by using this context. The analyses have been performed using the Verifiable Fuel Cycle Simulation of Nuclear Fuel Cycle Dynamics (VISION). We observe that the 2005 objectives and goals do not address many of the inherently dynamic discriminators among advanced fuel cycle options and transitions thereof.

  16. Dynamics of non-minimally coupled perfect fluids

    NASA Astrophysics Data System (ADS)

    Bettoni, Dario; Liberati, Stefano

    2015-08-01

    We present a general formulation of the theory for a non-minimally coupled perfect fluid in which both conformal and disformal couplings are present. We discuss how such non-minimal coupling is compatible with the assumptions of a perfect fluid and derive both the Einstein and the fluid equations for such model. We found that, while the Euler equation is significantly modified with the introduction of an extra force related to the local gradients of the curvature, the continuity equation is unaltered, thus allowing for the definition of conserved quantities along the fluid flow. As an application to cosmology and astrophysics we compute the effects of the non-minimal coupling on a Friedmann-Lemaȋtre-Robertson-Walker metric at both background and linear perturbation level and on the Newtonian limit of our theory.

  17. Dynamic response of viscous compressible fluids in rigid tubes

    NASA Technical Reports Server (NTRS)

    Goldschmied, F. R.

    1971-01-01

    Data on experimental verification of Iberall's analysis applies to such problems as pressure sensing, pneumatic control circuits with bellows, measuring irregular shaped volumes, and transmitting fluid power by pulsating flow.

  18. Explosive Vessel for Dynamic Experiments at Advanced Light Sources

    NASA Astrophysics Data System (ADS)

    Owens, Charles; Sorensen, Christian; Armstrong, Christopher; Sanchez, Nathaniel; Jensen, Brian

    2015-06-01

    There has been significant effort in coupling dynamic loading platforms to advanced light sources such as the Advanced Photon Source (APS) to take advantage of X-ray diagnostics for examining material physics at extremes. Although the focus of these efforts has been on using gun systems for dynamic compression experiments, there are many experiments that require explosive loading capabilities including studies related to detonator dynamics, small angle X-ray scattering on explosives, and ejecta formation, for example. To this end, an explosive vessel and positioning stage was designed specifically for use at a synchrotron with requirements to confine up to 15 grams of explosives, couple the vessel to the X-ray beam line, and reliably position samples in the X-ray beam remotely with micrometer spatial accuracy. In this work, a description of the system will be provided along with explosive testing results for the robust, reusable positioning system.

  19. Evaluation of Aircraft Platforms for SOFIA by Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Klotz, S. P.; Srinivasan, G. R.; VanDalsem, William (Technical Monitor)

    1995-01-01

    The selection of an airborne platform for the Stratospheric Observatory for Infrared Astronomy (SOFIA) is based not only on economic cost, but technical criteria, as well. Technical issues include aircraft fatigue, resonant characteristics of the cavity-port shear layer, aircraft stability, the drag penalty of the open telescope bay, and telescope performance. Recently, two versions of the Boeing 747 aircraft, viz., the -SP and -200 configurations, were evaluated by computational fluid dynamics (CFD) for their suitability as SOFIA platforms. In each configuration the telescope was mounted behind the wings in an open bay with nearly circular aperture. The geometry of the cavity, cavity aperture, and telescope was identical in both platforms. The aperture was located on the port side of the aircraft and the elevation angle of the telescope, measured with respect to the vertical axis, was 500. The unsteady, viscous, three-dimensional, aerodynamic and acoustic flow fields in the vicinity of SOFIA were simulated by an implicit, finite-difference Navier-Stokes flow solver (OVERFLOW) on a Chimera, overset grid system. The computational domain was discretized by structured grids. Computations were performed at wind-tunnel and flight Reynolds numbers corresponding to one free-stream flow condition (M = 0.85, angle of attack alpha = 2.50, and sideslip angle beta = 0 degrees). The computational domains consisted of twenty-nine(29) overset grids in the wind-tunnel simulations and forty-five(45) grids in the simulations run at cruise flight conditions. The maximum number of grid points in the simulations was approximately 4 x 10(exp 6). Issues considered in the evaluation study included analysis of the unsteady flow field in the cavity, the influence of the cavity on the flow across empennage surfaces, the drag penalty caused by the open telescope bay, and the noise radiating from cavity surfaces and the cavity-port shear layer. Wind-tunnel data were also available to compare

  20. Textbook Multigrid Efficiency for Computational Fluid Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Brandt, Achi; Thomas, James L.; Diskin, Boris

    2001-01-01

    Considerable progress over the past thirty years has been made in the development of large-scale computational fluid dynamics (CFD) solvers for the Euler and Navier-Stokes equations. Computations are used routinely to design the cruise shapes of transport aircraft through complex-geometry simulations involving the solution of 25-100 million equations; in this arena the number of wind-tunnel tests for a new design has been substantially reduced. However, simulations of the entire flight envelope of the vehicle, including maximum lift, buffet onset, flutter, and control effectiveness have not been as successful in eliminating the reliance on wind-tunnel testing. These simulations involve unsteady flows with more separation and stronger shock waves than at cruise. The main reasons limiting further inroads of CFD into the design process are: (1) the reliability of turbulence models; and (2) the time and expense of the numerical simulation. Because of the prohibitive resolution requirements of direct simulations at high Reynolds numbers, transition and turbulence modeling is expected to remain an issue for the near term. The focus of this paper addresses the latter problem by attempting to attain optimal efficiencies in solving the governing equations. Typically current CFD codes based on the use of multigrid acceleration techniques and multistage Runge-Kutta time-stepping schemes are able to converge lift and drag values for cruise configurations within approximately 1000 residual evaluations. An optimally convergent method is defined as having textbook multigrid efficiency (TME), meaning the solutions to the governing system of equations are attained in a computational work which is a small (less than 10) multiple of the operation count in the discretized system of equations (residual equations). In this paper, a distributed relaxation approach to achieving TME for Reynolds-averaged Navier-Stokes (RNAS) equations are discussed along with the foundations that form the

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

    EPA Science Inventory

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

  2. ADDRESSING HUMAN EXPOSURES TO AIR POLLUTANTS AROUND BUILDINGS IN URBAN AREAS WITH COMPUTATIONAL FLUID DYNAMICS MODELS

    EPA Science Inventory

    This paper discusses the status and application of Computational Fluid Dynamics (CFD) models to address challenges for modeling human exposures to air pollutants around urban building microenvironments. There are challenges for more detailed understanding of air pollutant sour...

  3. Fluid Dynamic Experiments Bearing on the Filling of Silicic Segregations in Basaltic Sills.

    NASA Astrophysics Data System (ADS)

    Zavala, K.; Marsh, B. D.

    2002-05-01

    Silicic segregations are present only in the upper parts of large diabase sills, lava lakes, and gabbroic intrusions. The segregations often have sharp upper contacts and diffuse lower contacts that grade into the host rock texture. Segregation compositions correspond to interstitial liquids present at crystallinities of 59 to 63% and temperatures of 1135 to 1115° . We have analyzed over 100 segregation samples from the Ferrar Dolerites of the McMurdo Dry Valleys, Antarctica, to investigate the nature of the segregation infilling process. Stratigraphic, spatial, textural, and chemical relations indicate that silicic segregations are generated by physical tearing of the upper Solidification Front due to gravitational instability. Previous work (Zavala & Marsh, 2001) shows that large, texturally inhomogeneous segregations with non-monotonic SiO2 profiles form by multiple infilling episodes. In contrast, smaller segregations with homogeneous textural and chemical profiles form during single, continuous filling episodes. We have experimentally simulated this process by examining the dynamics of fluid flow through a porous disk as it is pressed downward through a series of viscously stratified fluids contained in a vertical cylinder (14 cm X 32 cm). The effect of permeability (Kd) can be gauged using a combination of superimposed discs with a set pattern of holes that varies in number and size. The rate of flow advance, as might be expected from Darcy's Equation, is governed by the net permeability, the viscosity, and the effective density contrast between the settling disk and the surrounding fluid. Density contrast can be adjusted by applying different loads to the piston of disks via a shaft down through the cylinder. At a critical amount of loading, for a high viscosity contrast between the fluid layers, the flow field is characterized by a series of finger-like plumes that penetrate upward into the overlying layer as the disk descends. When the load is below the

  4. Immersed Particle Dynamics in Fluctuating Fluids with Memory

    NASA Astrophysics Data System (ADS)

    Hohenegger, Christel; McKinley, Scott

    2014-11-01

    Multibead passive microrheology characterizes bulk fluid properties of viscoelastic liquids by connecting statistically measurable quantities (e.g. mean-square displacement, auto-correlation to mechanical fluid properties (loss and storage modulus). Understanding how these material properties relate to biological quantities (e.g. exit time, first passage time through a layer) is of crucial importance for many pharmaceutical and industrial applications. To correctly model the correlations due to the fluid's memory, it is necessary to include a thermally fluctuating stress in the Stokes equations (Landau and Lifschitz 1958). We present such a model for an immersed particle passively advected by a fluctuating Maxwellian fluid. We describe the resulting stochastic partial differential equations for the underlying non-Markovian, stationary fluid velocity process and we present a covariance based numerical method for generating particle paths. Finally, we apply standard experimental one and two-point microrheology protocol to recover bulk loss and storage modulus and quantify the resulting errors. Our approach can be applied to a Stokes fluid with memory created by a large suspension of active swimmers or to the diffusion of a particle in a crowded environment.

  5. Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model.

    PubMed

    Reid, Daniel A P; Hildenbrandt, H; Padding, J T; Hemelrijk, C K

    2012-02-01

    The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed analysis. Their insights may guide empirical work. Particularly the recently introduced multiparticle collision dynamics method may be suitable for the study of moving organisms because it is computationally fast, simple to implement, and has a continuous representation of space. As regards the study of hydrodynamics of moving organisms, the method has only been applied at low Reynolds numbers (below 120) for soft, permeable bodies, and static fishlike shapes. In the present paper we use it to study the hydrodynamics of an undulating fish at Reynolds numbers 1100-1500, after confirming its performance for a moving insect wing at Reynolds number 75. We measure (1) drag, thrust, and lift forces, (2) swimming efficiency and spatial structure of the wake, and (3) distribution of forces along the fish body. We confirm the resemblance between the simulated undulating fish and empirical data. In contrast to theoretical predictions, our model shows that for steadily undulating fish, thrust is produced by the rear 2/3 of the body and that the slip ratio U/V (with U the forward swimming speed and V the rearward speed of the body wave) correlates negatively (instead of positively) with the actual Froude efficiency of swimming. Besides, we show that the common practice of modeling individuals while constraining their sideways acceleration causes them to resemble unconstrained fish with a higher tailbeat frequency. PMID:22463238

  6. Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model

    NASA Astrophysics Data System (ADS)

    Reid, Daniel A. P.; Hildenbrandt, H.; Padding, J. T.; Hemelrijk, C. K.

    2012-02-01

    The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed analysis. Their insights may guide empirical work. Particularly the recently introduced multiparticle collision dynamics method may be suitable for the study of moving organisms because it is computationally fast, simple to implement, and has a continuous representation of space. As regards the study of hydrodynamics of moving organisms, the method has only been applied at low Reynolds numbers (below 120) for soft, permeable bodies, and static fishlike shapes. In the present paper we use it to study the hydrodynamics of an undulating fish at Reynolds numbers 1100-1500, after confirming its performance for a moving insect wing at Reynolds number 75. We measure (1) drag, thrust, and lift forces, (2) swimming efficiency and spatial structure of the wake, and (3) distribution of forces along the fish body. We confirm the resemblance between the simulated undulating fish and empirical data. In contrast to theoretical predictions, our model shows that for steadily undulating fish, thrust is produced by the rear 2/3 of the body and that the slip ratio U/V (with U the forward swimming speed and V the rearward speed of the body wave) correlates negatively (instead of positively) with the actual Froude efficiency of swimming. Besides, we show that the common practice of modeling individuals while constraining their sideways acceleration causes them to resemble unconstrained fish with a higher tailbeat frequency.

  7. Conceptual design for the Space Station Freedom fluid physics/dynamics facility

    NASA Technical Reports Server (NTRS)

    Thompson, Robert L.; Chucksa, Ronald J.; Omalley, Terence F.; Oeftering, Richard C.

    1993-01-01

    A study team at NASA's Lewis Research Center has been working on a definition study and conceptual design for a fluid physics and dynamics science facility that will be located in the Space Station Freedom's baseline U.S. Laboratory module. This modular, user-friendly facility, called the Fluid Physics/Dynamics Facility, will be available for use by industry, academic, and government research communities in the late 1990's. The Facility will support research experiments dealing with the study of fluid physics and dynamics phenomena. Because of the lack of gravity-induced convection, research into the mechanisms of fluids in the absence of gravity will help to provide a better understanding of the fundamentals of fluid processes. This document has been prepared as a final version of the handout for reviewers at the Fluid Physics/Dynamics Facility Assessment Workshop held at Lewis on January 24 and 25, 1990. It covers the background, current status, and future activities of the Lewis Project Study Team effort. It is a revised and updated version of a document entitled 'Status Report on the Conceptual Design for the Space Station Fluid Physics/Dynamics Facility', dated January 1990.

  8. Numerical Simulation of the Dynamic FSI Response and Stability of a Flapping Foil in a Dense Fluid

    NASA Astrophysics Data System (ADS)

    Chae, Eun Jung; Akcabay, Deniz Tolga; Young, Yin Lu

    2012-11-01

    To advance the understanding of fish locomotion, improve the design biological devices or marine propulsions or turbines, or to explore innovative ocean energy harvesting ideas, it is important to be able accurately predict the dynamic fluid structure interaction (FSI) response and stability of flexible structures in a dense fluid. The objectives of this research are to (1) present an efficient and stable algorithm for numerical modeling of the dynamic FSI response and stability of a flapping foil in dense fluid, and (2) investigate the influence of fluid-to-solid density ratio on the FSI response and stability of a flapping foil. The numerical model involves coupling an unsteady RANS solver with a 2DOF structural model using a new hybrid coupling approach. The results show that the new hybrid coupling approach converge much faster than traditional loosely and tightly coupled approaches, and is able to avoid numerical instability issues due to virtual added mass effects for light, flexible structures in incompressible flow. The influence of density ratio on the FSI response, divergence and flutter speeds are presented, along with comparisons between viscous and inviscid FSI computations.

  9. Program package FLUX for the simulation of fundamental and applied problems of fluid dynamics

    NASA Astrophysics Data System (ADS)

    Babakov, A. V.

    2016-06-01

    Based on parallel algorithms of a conservative numerical method, a software package for simulating fundamental and applied fluid dynamics problems in a wide range of parameters is developed. The software is implemented on a cluster computer system. Examples of the numerical simulation of three-dimensional problems in various fields of fluid dynamics are discussed, including problems of external flow around bodies, investigation of aerodynamic characteristics of flying vehicles, flows around a set of objects, flows in nozzles, and flows around underwater constructs.

  10. Fluid dynamics of pressurized, entrained coal gasifiers. Technical progress report, April 1, 1995--June 30, 1995

    SciTech Connect

    Louge, M.Y.

    1995-10-01

    A study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs) is being conducted. The idea is to simulate the flows in generic industrial PECGs using dimensional simulitude. A unique entrained gas-solid flow facility with the flexibility to recycle rather than discard gases other than air has been utilized. By matching five dimensionaless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-up on the fluid dynamics of PECGs.

  11. Development and Use of Engineering Standards for Computational Fluid Dynamics for Complex Aerospace Systems

    NASA Technical Reports Server (NTRS)

    Lee, Hyung B.; Ghia, Urmila; Bayyuk, Sami; Oberkampf, William L.; Roy, Christopher J.; Benek, John A.; Rumsey, Christopher L.; Powers, Joseph M.; Bush, Robert H.; Mani, Mortaza

    2016-01-01

    Computational fluid dynamics (CFD) and other advanced modeling and simulation (M&S) methods are increasingly relied on for predictive performance, reliability and safety of engineering systems. Analysts, designers, decision makers, and project managers, who must depend on simulation, need practical techniques and methods for assessing simulation credibility. The AIAA Guide for Verification and Validation of Computational Fluid Dynamics Simulations (AIAA G-077-1998 (2002)), originally published in 1998, was the first engineering standards document available to the engineering community for verification and validation (V&V) of simulations. Much progress has been made in these areas since 1998. The AIAA Committee on Standards for CFD is currently updating this Guide to incorporate in it the important developments that have taken place in V&V concepts, methods, and practices, particularly with regard to the broader context of predictive capability and uncertainty quantification (UQ) methods and approaches. This paper will provide an overview of the changes and extensions currently underway to update the AIAA Guide. Specifically, a framework for predictive capability will be described for incorporating a wide range of error and uncertainty sources identified during the modeling, verification, and validation processes, with the goal of estimating the total prediction uncertainty of the simulation. The Guide's goal is to provide a foundation for understanding and addressing major issues and concepts in predictive CFD. However, this Guide will not recommend specific approaches in these areas as the field is rapidly evolving. It is hoped that the guidelines provided in this paper, and explained in more detail in the Guide, will aid in the research, development, and use of CFD in engineering decision-making.

  12. The Use of Computational Fluid Dynamics in the Development of Ventricular Assist Devices

    PubMed Central

    Fraser, Katharine H.; Taskin, M. Ertan; Griffith, Bartley P.; Wu, Zhongjun J.

    2010-01-01

    Progress in the field of prosthetic cardiovascular devices has significantly contributed to the rapid advancements in cardiac therapy during the last four decades. The concept of mechanical circulatory assistance was established with the first successful clinical use of heart-lung machines for cardiopulmonary bypass. Since then a variety of devices have been developed to replace or assist diseased components of the cardiovascular system. Ventricular assist devices (VADs) are basically mechanical pumps designed to augment or replace the function of one or more chambers of the failing heart. Computational Fluid Dynamics (CFD) is an attractive tool in the development process of VADs, allowing numerous different designs to be characterized for their functional performance virtually, for a wide range of operating conditions, without the physical device being fabricated. However, VADs operate in a flow regime which is traditionally difficult to simulate; the transitional region at the boundary of laminar and turbulent flow. Hence different methods have been used and the best approach is debatable. In addition to these fundamental fluid dynamic issues, blood consists of biological cells. Device-induced biological complications are a serious consequence of VAD use. The complications include blood damage (haemolysis, blood cell activation), thrombosis and emboli. Patients are required to take anticoagulation medication constantly which may cause bleeding. Despite many efforts blood damage models have still not been implemented satisfactorily into numerical analysis of VADs, which severely undermines the full potential of CFD. This paper reviews the current state of the art CFD for analysis of blood pumps, including a practical critical review of the studies to date, which should help device designers choose the most appropriate methods; a summary of blood damage models and the difficulties in implementing them into CFD; and current gaps in knowledge and areas for future

  13. 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.

  14. Connecting Molecular Dynamics Simulations and Fluids Density Functional Theory of Block Copolymers

    NASA Astrophysics Data System (ADS)

    Hall, Lisa

    Increased understanding and precise control over the nanoscale structure and dynamics of microphase separated block copolymers would advance development of mechanically robust but conductive materials for battery electrolytes, among other applications. Both coarse-grained molecular dynamics (MD) simulations and fluids (classical) density functional theory (fDFT) can capture the microphase separation of block copolymers, using similar monomer-based chain models and including local packing effects. Equilibrium free energies of various microphases are readily accessible from fDFT, which allows us to efficiently determine the equilibrium nanostructure over a large parameter space. Meanwhile, MD allows us to visualize specific polymer conformations in 3D over time and to calculate dynamic properties. The fDFT density profiles are used to initialize the MD simulations; this ensures the MD proceeds in the appropriate microphase separated state rather than in a metastable structure (useful especially for nonlamellar structures). The simulations equilibrate more quickly than simulations initialized with a random state, which is significant especially for long chains. We apply these methods to study the interfacial behavior and microphase separated structure of diblock and tapered block copolymers. Tapered copolymers consist of pure A and B monomer blocks on the ends separated by a tapered region that smoothly varies from A to B (or from B to A for an inverse taper). Intuitively, tapering increases the segregation strength required for the material to microphase separate and increases the width of the interfacial region. Increasing normal taper length yields a lower domain spacing and increased polymer mobility, while larger inverse tapers correspond to even lower domain spacing but decreased mobility. Thus the changes in dynamics with tapering cannot be explained by mapping to a diblock system at an adjusted effective segregation strength. This material is based upon work

  15. Trends in cardiac dynamics : towards coupled models of intracavity fluid dynamics and deformable wall mechanics

    NASA Astrophysics Data System (ADS)

    Pelle, G.; Ohayon, J.; Oddou, C.

    1994-06-01

    We report here preliminary results in the development of a computational model in cardiac mechanics which takes into account the coupled effects of ventricular mechanics and intracardiac hemodynamics. In this first work, complex geometrical, architectural and rheological properties of the organ have been strongly simplified in order to propose a “quasi-analytical” model. We assume axisymmetrical geometry of the ventricle and myocardium material to be made of a sheath of a composite, collagenic, fibrous and active muscle medium inside which the blood dynamics is dominated by unsteady inertial effects. Moreover, we have made grossly simplifying assumptions concerning rather stringent and unusual functioning conditions about the mechanical behavior of the input and output valvular and vascular impedances as well as the biochemical action of the fiber. By imposing the time variation of the input and output flow rate and activation function, it is possible, assuming uniformity of the pressure stresses applied to the internal wall surface at every instant of the cardiac cycle, to calculate the overall distribution of fluid pressure and velocity inside the cavity as well as the distributions of stresses and strains inside the wall. It was shown that under the action of a given biochemical activation function, both kinematics of the wall and induced motion of the fluid are such that the boundary conditions concerning normal pressure stresses conservation was constantly satisfied. Moreover, the results concerning the dynamics of the blood flow, as viewed through the human clinical investigations using velocimetric technology based upon color doppler ultrasound, are in accordance with those obtained from such a model, at least during the ejection phase. In particular, contrarily to the filling phase processes, the ejection dynamics is such that the time evolution of the blood velocity measured along the cavity axis does not display any phase shift characterizing an

  16. Dynamics of Shells and Fluid-Loaded Plates.

    NASA Astrophysics Data System (ADS)

    Wang, Zhang

    This thesis is composed of two parts. The first part is concerned with wave propagation on elastic structures in vacuum. An asymptotic approximation is obtained for the dispersion relation of flexural waves propagating in an infinite, flat plate, with material and/or geometric properties periodic in one direction. A matrix approach is proposed to investigate waves in circular cylindrical thin shells joined with circular plates. Both the general propagator matrix and S-matrix formalisms are presented, with emphasis on the latter. The second part is devoted to structures with ambient fluid loading. The Green's function for a fluid-loaded plate under line loading is expressed as a sum of five fluid-loaded plate waves and an acoustic wave with magnitude given by an infinite integral, similar to a branch cut integral. A scattering matrix approach is presented to solve wave propagation problems on fluid-loaded plates with attached ribs. The low frequency asymptotic dispersion relation for a fluid-loaded plate with infinite number of equally spaced identical ribs is derived, from which an equation of motion for the plate is inferred which is valid also at low frequencies.

  17. Stable Small Animal Mechanical Ventilation for Dynamic Lung Imaging to Support Computational Fluid Dynamics Models

    SciTech Connect

    Jacob, Rick E.; Lamm, W. J.

    2011-11-08

    Pulmonary computational fluid dynamics models require 3D images to be acquired over multiple points in the dynamic breathing cycle, with no breath holds or changes in ventilatory mechanics. With small animals, these requirements result in long imaging times ({approx}90 minutes), over which lung mechanics, such as compliance, can gradually change if not carefully monitored and controlled. These changes, caused by derecruitment of parenchymal tissue, are manifested as an upward drift in peak inspiratory pressure or by changes in the pressure waveform and/or lung volume over the course of the experiment. We demonstrate highly repeatable mechanical ventilation in anesthetized rats over a long duration for pulmonary CT imaging throughout the dynamic breathing cycle. We describe significant updates to a basic commercial ventilator that was acquired for these experiments. Key to achieving consistent results was the implementation of periodic deep breaths, or sighs, of extended duration to maintain lung recruitment. In addition, continuous monitoring of breath-to-breath pressure and volume waveforms and long-term trends in peak inspiratory pressure and flow provide diagnostics of changes in breathing mechanics.

  18. Computational fluid dynamics '92; Proceedings of the European Computational Fluid Dynamics Conference, 1st, Brussels, Belgium, Sep. 7-11, 1992. Vols. 1 & 2

    NASA Technical Reports Server (NTRS)

    Hirsch, Charles (Editor); Periaux, J. (Editor); Kordulla, W. (Editor)

    1992-01-01

    A conference was held on Computational Fluid Dynamics (CFD) and produced related papers. Topics included CFD algorithms, transition and turbulent flow, hypersonic reacting flow, incompressible flow, two phase flow and combustion, internal flow, compressible flow, grid generation and adaption, boundary layers, environmental and industrial applications, and non-Newtonian flow.

  19. Advanced optical measuring systems for measuring the properties of fluids and structures

    NASA Technical Reports Server (NTRS)

    Decker, A. J.

    1986-01-01

    Four advanced optical models are reviewed for the measurement of visualization of flow and structural properties. Double-exposure, diffuse-illumination, holographic interferometry can be used for three-dimensional flow visualization. When this method is combined with optical heterodyning, precise measurements of structural displacements or fluid density are possible. Time-average holography is well known as a method for displaying vibrational mode shapes, but it also can be used for flow visualization and flow measurements. Deflectometry is used to measure or visualize the deflection of light rays from collimation. Said deflection occurs because of refraction in a fluid or because of reflection from a tilted surface. The moire technique for deflectometry, when combined with optical heterodyning, permits very precise measurements of these quantities. The rainbow schlieren method of deflectometry allows varying deflection angles to be encoded with colors for visualization.

  20. Isomorphic classical molecular dynamics model for an excess electronin a supercritical fluid

    SciTech Connect

    Miller III, Thomas F.

    2008-08-04

    Ring polymer molecular dynamics (RPMD) is used to directly simulate the dynamics of an excess electron in a supercritical fluid over a broad range of densities. The accuracy of the RPMD model is tested against numerically exact path integral statistics through the use of analytical continuation techniques. At low fluid densities, the RPMD model substantially underestimates the contribution of delocalized states to the dynamics of the excess electron. However, with increasing solvent density, the RPMD model improves, nearly satisfying analytical continuation constraints at densities approaching those of typical liquids. In the high density regime, quantum dispersion substantially decreases the self-diffusion of the solvated electron. In this regime where the dynamics of the electron is strongly coupled to the dynamics of the atoms in the fluid, trajectories that can reveal diffusive motion of the electron are long in comparison to {beta}{h_bar}.