Download or read book Nonequilibrium Hypersonic Aerothermodynamics Using the Direct Simulation Monte Carlo And Navier Stokes Models written by and published by . This book was released on 2008 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hypersonic flight vehicles are a current topic of interest in both civilian and military research. NASA is currently designing a Crew Transport Vehicle (CTV) [44, 69] and Crew Exploration Vehicle (CEV) [32] to replace the space shuttle; reentry vehicles are, by definition, hypersonic vehicles. Military requirements for reconnaissance and surveillance, as well as the mission of the United States Air Force to rapidly project power globally makes the design of a hypersonic plane that can quickly traverse the globe very attractive [102]. The design of hypersonic vehicles requires accurate prediction of the surface properties while in flight. These quantities are typically the heat flux, pressure and shear stress, from which the aerodynamic forces and moments can be calculated. These variables govern not only the aerodynamic performance of the vehicle, but also determine the selection and sizing of the thermal protection system (TPS), which protects the vehicle from the extreme temperatures encountered at hypersonic velocities. The geometry of a vehicle, and in particular, the nose and the leading edges of wings and other aerodynamic surfaces, is a critical consideration in a vehicle's design. Aerodynamic heating is inversely proportional to the square root of the 1 radius at the stagnation point; hence, historically most vehicles have had blunted noses and leading edges to reduce the thermal loads to acceptable levels. Recently, however, a class of materials, designated Ultra-High Temperature Ceramic (UHTC) composites, has been developed that can withstand temperatures as high as 3500 K [57, 78]. Materials such as these allow the use of much sharper leading edges.

Download or read book Consistent Modeling of Hypersonic Nonequilibrium Flows Using Direct Simulation Monte Carlo written by Chonglin Zhang and published by . This book was released on 2013 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theoretical Modelling of Aeroheating on Sharpened Noses Under Rarefied Gas Effects and Nonequilibrium Real Gas Effects written by Zhi-Hui Wang and published by Springer. This book was released on 2014-08-28 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical Modelling of Aeroheating on Sharpened Noses under Rarefied Gas Effects and Nonequilibrium Real Gas Effects employs a theoretical modeling method to study hypersonic flows and aeroheating on sharpened noses under rarefied gas effects and nonequilibrium real gas effects that are beyond the scope of traditional fluid mechanics. It reveals the nonlinear and nonequilibrium features, discusses the corresponding flow and heat transfer mechanisms, and ultimately establishes an analytical engineering theory framework for hypersonic rarefied and chemical nonequilibrium flows. The original analytical findings presented are not only of great academic significance, but also hold considerable potential for applications in engineering practice. The study explores a viable new approach, beyond the heavily relied-upon numerical methods and empirical formulas, to the present research field, which could be regarded as a successful implementation of the idea and methodology of the engineering sciences.

Download or read book Theoretical and Numerical Studies of Rarefied Hypersonic Flows written by Xionghui Huang and published by . This book was released on 2014 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation a comprehensive work on theoretical and numerical studies of rarefied hypersonic flows is presented. On the theoretical part, gaskinetic study and exact solutions are obtained for problems related with high speed collisionless round jet: expanding into a vacuum; impinging at a normally set, diffuse or specular reflective plate with finite radius. Several fundamental geometry-velocity relations are utilized in this study and they play crucial roles. These complete results include flowfield properties, and impingement properties at the plate surface. The final results include complex but accurate integrations involving geometry and specific speed ratio factors. Severals numerical simulations with the direct simulation Monte Carlo method validate these analytical exact results. In the numerical part, a multi-dimensional gas-dynamical computational scheme package GRASP-K ("Generalized Rarefied gAs Simulation Package - Kinetic") is presented. This implementation adopts a concept of simulation engine and it utilizes many Object-Oriented Programming features and software engineering design patterns. As a result, this implementation successfully resolves the problem of functionality and interface conflictions for multi-dimension Gas Kinetic Scheme implementations. The package has an open architecture which benefits further development and code maintenance. This package can utilize traditional structured, unstructured or hybrid grids to model multi-dimensional complex geometries and multi-species hypersonic thermo-chemically non equilibrium gas flows. A preliminary test case of a two-species hypersonic flow passing a cylinder and some preliminary results are obtained. The pressure distribution of the gas mixture along the cylinder wall is compared with those in previous works. A Navier-Stokes equations based computational fluid dynamics solver is also incorporated in the package to simulate hypersonic nonequilibrium flows. This solver includes comprehensive chemical reaction models and thermodynamics relations and the phenolic-silica ablation flow simulation is considered. Finite rate chemical reactions, multiple temperature relaxation processes, and ionization phenomena are modeled. Hence the package can be used to simulate multiple-dimensional, non-equilibrium gas flows with multiple species. Simulation results of several hypersonic gas flows over blunted bodies are presented and compared with results in the literature.

Download or read book Nonequilibrium Hypersonic Aerothermodynamics written by Chul Park and published by Wiley-Interscience. This book was released on 1990-03-01 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes the interaction between the fluid flow and the high temperature phenomena experienced in the hypersonic regime. Presents the principles of aerothermodynamics in nonequilibrium hypersonic flow regimes, covering theory, application and surface phenomena. Chapters 1 to 5 explain how to develop computational fluid dynamics (CFD) techniques for computing nonequilibrium, chemically reacting flows in the hypersonic regime. Chapters 6 to 8 examine the important physical phenomena that occur in hypersonic flows. The final chapter is devoted to the nonequilibrium kinetics at solid surfaces, which is useful in addressing the problems of the nonequilibrium gas-surface interactions that arise in hypersonic flight.

Download or read book Velocity Slip and Temperature Jump in Hypersonic Aerothermodynamics written by and published by . This book was released on 2007 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hypersonic vehicles experience different flow regimes during flight due to changes in atmospheric density. Computational Fluid Dynamics (CFD), while relatively computationally inexpensive, are not physically accurate in areas of highly non-equilibrium flows. The direct simulation Monte Carlo (DSMC) method, while physically accurate for all flow regimes, is relatively computationally expensive. A breakdown parameter can be used to determine where in the flow domain the CFD methods are valid. The current study investigates the effect of continuum breakdown on surface aerothermodynamic properties (pressure, shear stress and heat transfer rate) of a cylinder in Mach 10 and Mach 25 flows of argon gas for several different flow regimes, from the continuum to a rarefied gas. Several different velocity slip and temperature jump boundary conditions are examined for use with the CFD method. CFD and DSMC solutions are obtained at each condition. Total drag and peak heat transfer rate predictions by CFD remains within about 6% of the DSMC predictions for all regimes considered, with the generalized slip condition proposed by Gokcen giving the best results.

Download or read book Shock Wave Boundary Layer Interactions written by Holger Babinsky and published by Cambridge University Press. This book was released on 2011-09-12 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock wave-boundary-layer interaction (SBLI) is a fundamental phenomenon in gas dynamics that is observed in many practical situations, ranging from transonic aircraft wings to hypersonic vehicles and engines. SBLIs have the potential to pose serious problems in a flowfield; hence they often prove to be a critical - or even design limiting - issue for many aerospace applications. This is the first book devoted solely to a comprehensive, state-of-the-art explanation of this phenomenon. It includes a description of the basic fluid mechanics of SBLIs plus contributions from leading international experts who share their insight into their physics and the impact they have in practical flow situations. This book is for practitioners and graduate students in aerodynamics who wish to familiarize themselves with all aspects of SBLI flows. It is a valuable resource for specialists because it compiles experimental, computational and theoretical knowledge in one place.

Download or read book Monte Carlo Sensitivity Analyses of DSMC Parameters for Ionizing Hypersonic Flows written by Kyle J. Higdon and published by . This book was released on 2018 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work focuses on the development and sensitivity analyses of a direct simulation Monte Carlo (DSMC) code to understand the complex physical processes that occur during hypersonic entry into a rarefied atmosphere. Simulations are performed on 1-dimensional hypersonic shock scenarios that mimic the conditions of high altitude atmospheric entry to Earth and Saturn with the Computation of Hypersonic Ionizing Particles in Shocks (CHIPS) code. To model hypersonic entry problems accurately, the CHIPS code must resolve nonequilibrium flows and account for a number of complex gas dynamics processes at the molecular level. In this thesis, several high temperature models are added to the CHIPS code including charged particle models and electronic excitation. These models are refined using preliminary sensitivity analyses resulting in improved electronic excitation models and a new backward chemical reaction model. The CHIPS simulations completed in this work reproduce rarefied hypersonic shock tube experiments performed in the Electric Arc Shock Tube (EAST) at NASA Ames Research Center. The CHIPS results are post-processed by the NEQAIR line-by-line radiative solver to compare directly to spectra measured experimentally in EAST. The DSMC techniques used to model hypersonic phenomena require numerous experimentally calibrated parameters. Many of these parameters are inferred from lower temperature experiments, resulting in an unknown amount of uncertainty in the simulated results at the extreme conditions of hypersonic flow. A global Monte Carlo sensitivity analysis is performed by simultaneously varying the CHIPS input parameter values to understand the sensitivity of experimentally measured quantities simulated by the CHIPS and NEQAIR codes. The sensitivity of several of these output quantities is used to rank the input parameters, identifying the most important parameters for the simulation of the hypersonic scenario. It was concluded that experimentally measured radiation intensity is most sensitive to the following key processes: N+e−⇌N++e−+e−, NO+N+⇌N+NO+, N2+N⇌N+N+N, N+O⇌NO++e−, N+N⇌N2++e−, and Z [subscript elec] for N, O, and N2+. In the future, this ranking can be used to identify which input parameters should be experimentally investigated, where model improvements could be beneficial, and aid in reducing the parameter space for DSMC calibrations to experimental data.

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 850 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in an Open source Direct Simulation Monte Carlo Technique for Hypersonic Rarefied Gas Flows written by Abdul Ossman Ahmad and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hypersonic vehicles that travel through rarefied gas environments are very expensive to design through experimental methods. In the last few decades major work has been carried out in developing numerical methods to capture these types of flows to a certain degree of accuracy. This accuracy is increased using particle based numerical techniques as opposed to continuum computational fluid dynamics. However, one of the modern problems of particle based techniques is the high computational cost associated with it. This thesis presents an enhanced open-source particle based technique to capture high speed rarefied gas flows. This particle based technique is called dsmcFoam and is based on the direct simulation Monte Carlo technique. As a result of the author's work dsmcFoam has become more efficient and accurate. Benchmark studies of the standard dsmcFoam solver will be presented before introducing the main advances. The results of the benchmark investigations are compared with analytical solutions, other DSMC codes and experimental data available in the literature. And excellent agreement is found when good DSMC practice has been followed. The main advances of dsmcFoam discussed are a routine for selecting collision pairs called the transient adaptive sub-cell (TASC) method and a dynamic wall temperature model (DWTM). The DWTM relates the wall temperature to the heat flux. In addition, verification and validation studies are undertaken of the DWTM. Furthermore, the widely used conventional 8 sub-cell method used to select possible collision pairs becomes very cumbersome to employ properly. This is because many mesh refinement stages are required in order to obtain accurate data. Instead of mesh refinement the TASC technique automatically employs more sub-cells, and these sub-cells are based on the number of particles in a cell. Finally, parallel efficiency tests of dsmcFoam are presented in this thesis along with a new domain decomposition technique for parallel processing. This technique splits up the computational domain based on the number of particles, such that each processor has the same number of particles to work with.

Download or read book Nonequilibrium Gas Dynamics and Molecular Simulation written by Iain D. Boyd and published by Cambridge University Press. This book was released on 2017-03-23 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: 7.1 Introduction -- 7.2 Rotational Energy Exchange Models -- 7.2.1 Constant Collision Number -- 7.2.2 The Parker Model -- 7.2.3 Variable Probability Exchange Model of Boyd -- 7.2.4 Nonequilibrium Direction Dependent Model -- 7.2.5 Model Results -- 7.3 Vibrational Energy Exchange Models -- 7.3.1 Constant Collision Number -- 7.3.2 The Millikan-White Model -- 7.3.3 Quantized Treatment for Vibration -- 7.3.4 Model Results -- 7.4 Dissociation Chemical Reactions -- 7.4.1 Total Collision Energy Model -- 7.4.2 Redistribution of Energy Following a Dissociation Reaction -- 7.4.3 Vibrationally Favored Dissociation Model -- 7.5 General Chemical Reactions -- 7.5.1 Reaction Rates and Equilibrium Constant -- 7.5.2 Backward Reaction Rates in DSMC -- 7.5.3 Three-Body Recombination Reactions -- 7.5.4 Post-Reaction Energy Redistribution and General Implementation -- 7.5.5 DSMC Solutions for Reacting Flows -- 7.6 Summary -- Appendix A: Generating Particle Properties -- Appendix B: Collisional Quantities -- Appendix C: Determining Post-Collision Velocities -- Appendix D: Macroscopic Properties -- Appendix E: Common Integrals -- References -- Index

Download or read book Particle Simulation of Hypersonic Flow written by Donald Baganoff and published by . This book was released on 1993 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Studies of Low Density Two Dimensional Hypersonic Flows by Using the Navier Stokes and Burnett Equations with Nonequilibrium Real Gas Effects written by and published by . This book was released on 1997 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research is to study the laminar turbulent transition and other transient flow phenomena of 3-D chemically reacting hypersonic boundary layers by direct numerical simulation (DNS) and by linear stability analysis. The research in the report period was focused on developing new numerical methods for such studies and studying several fundamental transient hypersonic flow phenomena. First, several new efficient and high-order accurate numerical methods for DNS of 3-D hypersonic reacting boundary layers and for computing unsteady hypersonic flows with complex shock interactions were developed. These new methods were developed in order to overcome difficulties associated with the direct numerical simulation of hypersonic flows. Second, several studies on the stability phenomena of hypersonic boundary layers over blunt leading edges both by direct numerical simulation and by linear stability analyses were performed. Also completed were extensive numerical studies on real gas effects on a steady shock/boundary layer interaction and a self-sustained unsteady shock-shock interference heating flows. Third, the effects of using Burnett equations for rarefied hypersonic flow computations were investigated. With the completion of the bulk of work on the development of new numerical methods for complex hypersonic flow simulation, the DNS studies are currently being extended to 3-D hypersonic boundary layer transition over elliptic cross section cones.

Download or read book Hypersonic Nonequilibrium Flow Simulations Over a Blunt Body Using Bgk Simulations written by Sunny Jain and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been a continuous effort to unveil the physics of hypersonic flows both experimentally and numerically, in order to achieve an efficient hypersonic vehicle design. With the advent of the high speed computers, a lot of focus has been given on research pertaining to numerical approach to understand this physics. The features of such flows are quite different from those of subsonic, transonic and supersonic ones and thus normal CFD methodologies fail to capture the high speed flows efficiently. Such calculations are made even more challenging by the presence of nonequilibrium thermodynamic and chemical effects. Thus further research in the field of nonequilibrium thermodynamics is required for the accurate prediction of such high enthalpy flows. The objective of this thesis is to develop improved computational tools for hypersonic aerodynamics accounting for non-equilibrium effects. A survey of the fundamental theory and mathematical modeling pertaining to modeling high temperature flow physics is presented. The computational approaches and numerical methods pertaining to high speed flows are discussed. In the first part of this work, the fundamental theory and mathematical modeling pertaining to modeling high temperature flow physics is presented. Continuum based approach (Navier Stokes) and Boltzmann equation based approach (Gas Kinetic) are discussed. It is shown mathematically that unlike the most popular continuum based methods, Gas Kinetic method presented in this work satisfies the entropy condition. In the second part of this work, the computational approaches and numerical methods pertaining to high speed flows is discussed. In the continuum methods, the Steger Warming schemes and Roe's scheme are discussed. The kinetic approach discussed is the Boltzmann equation with Bhatnagar Gross Krook (BGK) collision operator. In the third part, the results from new computational fluid dynamics code developed are presented. A range of validation and verification test cases are presented. A comparison of the two common reconstruction techniques: Green Gauss gradient method and MUSCL scheme are discussed. Two of the most common failings of continuum based methods: excessive numerical dissipation and carbuncle phenomenon techniques, are investigated. It is found that for the blunt body problem, Boltzmann BGK method is free of these failings.

Download or read book Quantifying Non Equilibrium in Hypersonic Flows Using Entropy Generation written by and published by . This book was released on 2007 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: The constitutive relations traditionally used for finding shear stress and heat flux in a fluid become invalid in non-equilibrium flow. Their derivation from kinetic theory only demonstrates they are valid only for small deviations from equilibrium. Because it is fundamentally linked to non-equilibrium, entropy generation is used to investigate the limits of the continuum constitutive relations. However, the continuum equations are inherently limited to near equilibrium conditions due to the constitutive relations; thus kinetic theory must be used as a basis for comparison. Direct Simulation Monte Carlo (DSMC), a particle method alternative to continuum methods, is based on kinetic theory and is used to develop a flow solution free from equilibrium assumptions. Solutions were obtained for hypersonic flow over two axisymmetric geometries using both a continuum solver and DSMC. Formulations for entropy generation are presented for each method, and the two solutions are compared. The continuum solver fails to capture regions of non-equilibrium as evidenced by thicker shocks in the DSMC solution. To extend the useful range of the continuum constitutive relations, the Lennard-Jones model is offered as an alternative to Sutherland?s Law for calculating viscosity and thermal conductivity. The two are compared, and parameters offering a good fit for these flows are suggested for the Lennard-Jones model.

Download or read book Quantifying Non equilibrium in Hypersonic Flows Using Entropy Generation written by Ryan W. Carr and published by . This book was released on 2007 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Simulation of Hypersonic Transitional Flows Over Blunt Slender Bodies written by Vincent Cuda and published by . This book was released on 1987 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: