Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Simulation Of Supersonic Base Flows Numerical Investigations Using Dns Les And Urans
Download Simulation Of Supersonic Base Flows Numerical Investigations Using Dns Les And Urans full books in PDF, epub, and Kindle. Read online Simulation Of Supersonic Base Flows Numerical Investigations Using Dns Les And Urans ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Simulation of Supersonic Base Flows: Numerical Investigations Using DNS, LES, and URANS. by :
Download or read book Simulation of Supersonic Base Flows: Numerical Investigations Using DNS, LES, and URANS. written by and published by . This book was released on 2006 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transitional and turbulent supersonic axisymmetric wakes were investigated by conducting various numerical experiments. The main objective was to identify hydrodynamic instability mechanisms in the flow at Mach number M = 2.46 for several Reynolds numbers, and relating these to coherent structures that are found from various visualization techniques. The premise for this approach is the assumption that flow instabilities lead to the formation of coherent structures. The effect of these structures on the mean flow is of particular interest, as they strongly affect the base drag. Three high-order accurate compressible codes were developed in cylindrical coordinates for this research: A spatial Navier-Stokes (N-S) code to conduct Direct Numerical Simulations (DNS), a linearized N-S code for linear stability investigations using two-dimensional basic states, and a temporal N-S code for performing local stability analyses. The ability of numerical simulations to deliberately exclude physical effects is exploited. With this approach, the impact of structures associated with certain modes on the global wake-behavior can be scrutinized. It is concluded that azimuthal modes with low wavenumbers are responsible for a flat mean base-pressure distribution and that k=2 and k=4 are the dominant modes in the trailing wake, producing a four-lobe wake pattern. Circumstantial evidence is presented that absolutely unstable global modes within the recirculation region coexist with convectively unstable shear-layer modes. The flow is found to be absolutely unstable with respect to modes k>0 for Re-D> 5,000 and with respect to the axisymmetric mode for Re-D>100,000. Furthermore, it is investigated whether flow control measures designed to weaken the naturally most significant modes can decrease the base drag. Finally, the novel Flow Simulation Methodology (FSM), using state-of-the-art turbulence closures, was shown to reproduce DNS results at a fraction of the computational cost.
Book Synopsis Transition in High-Speed Boundary Layers: Numerical Investigations Using DNS and LES. by :
Download or read book Transition in High-Speed Boundary Layers: Numerical Investigations Using DNS and LES. written by and published by . This book was released on 2005 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct Numerical Simulations (DNS) of supersonic flow over a flat-plate with and without adverse pressure-gradient at Mach 3 were carried out in close collaboration with the experimental effort at Princeton University by G. Brown and co-workers. To confirm that simulations and experiments were based on the same "baseflow," the experimental baseflow profiles were compared with our Navier-Stokes results. The downstream development and the spatial growth rates of the disturbances obtained from the Navier-Stokes computations and from experimental measurements were compared as well. Overall, a remarkably good agreement was achieved. Towards the understanding of the nonlinear mechanisms, we investigated numerous nonlinear resonance and breakdown scenarios. Our simulations have shown that due to the stabilizing effects of compressibility for supersonic boundary layers, the transition process can be stretched significantly in the downstream direction and sometimes the transition process may even be aborted so that a turbulent boundary layer is never fully established. The extent of the transition process and the intensity of the temperature fluctuations, and the resulting heat load, depend strongly on the nonlinear mechanisms.
Book Synopsis Transition in High-Speed Boundary Layers: Numerical Investigations Using DNS and LES. by :
Download or read book Transition in High-Speed Boundary Layers: Numerical Investigations Using DNS and LES. written by and published by . This book was released on 2005 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct Numerical Simulations (DNS) of supersonic flow over a flat-plate with and without adverse pressure-gradient at Mach 3 were carried out in close collaboration with the experimental effort at Princeton University by G. Brown and co-workers. To confirm that simulations and experiments were based on the same "baseflow," the experimental baseflow profiles were compared with our Navier-Stokes results. The downstream development and the spatial growth rates of the disturbances obtained from the Navier-Stokes computations and from experimental measurements were compared as well. Overall, a remarkably good agreement was achieved. Towards the understanding of the nonlinear mechanisms, we investigated numerous nonlinear resonance and breakdown scenarios. Our simulations have shown that due to the stabilizing effects of compressibility for supersonic boundary layers, the transition process can be stretched significantly in the downstream direction and sometimes the transition process may even be aborted so that a turbulent boundary layer is never fully established. The extent of the transition process and the intensity of the temperature fluctuations, and the resulting heat load, depend strongly on the nonlinear mechanisms.
Book Synopsis Passive and Active Control of Supersonic Axisymmetric Base Flows: Direct Numerical Simulations and Large-Eddy Simulations by :
Download or read book Passive and Active Control of Supersonic Axisymmetric Base Flows: Direct Numerical Simulations and Large-Eddy Simulations written by and published by . This book was released on 2002 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new compressible Navier-Stokes code in cylindrical coordinates was developed for investigating axisymmetric wakes of bluff-based bodies in supersonic flows. In this code, high-order compact finite differences derived for non-equidistant grids are employed and a new stare-of-the-art axis treatment is incorporated. Additionally, the fully three-dimensional transport equations for turbulent kinetic energy and turbulent dissipation are implemented to enable (steady or unsteady) Reynolds Averaged Navier Stokes (RANS) simulations. Furthermore, a new "Flow Simulation Methodology" (FSM) was developed for computing complex compressible flows. The centerpiece of FSM) is a strategy to provide the proper amount of modeling of the subgrid scales. This is accomplished by a "contribution function" which locally and instantaneously compares the smallest relevant scales to the local grid size. The contribution function is designed such that it provides no modeling if the computation is locally well resolved so that the computation approaches a Direct Numerical Simulation (DNS) in the fine grid limit, or provides modeling of all scales in the coarse grid limit and thus approaches an unsteady PANS (URANS) calculation. In between these resolution limits, the contribution function adjusts the necessary modeling for the unresolved scales while the larger (resolved) scales are computed as in traditional Large Eddy Simulations (LES) . Preliminary results have shown that the new high- order code has great advantages for supersonic base flow simulations and that calculations, in particular together with FSM), will allow simulations of supersonic base flows at much higher Reynolds numbers than possible with conventional LES.
Book Synopsis Numerical Investigation of Supersonic Base Flow with Base Bleed by :
Download or read book Numerical Investigation of Supersonic Base Flow with Base Bleed written by and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A zonal, implicit, time-marching Navier-Stokes computational technique has been used to compute the turbulent supersonic base flow over a cylindrical afterbody with base bleed. A critical element of calculating such flows is the turbulence model. Two eddy viscosity turbulence models have been used in the base region flow computations. These models include an algebraic turbulence model and a two-equation k-e model. The k-e equations are solved using an implicit algorithm, and calculations with the k-e model are extended up to the wall. Flow field computations have been performed for a cylindrical afterbody at M approx. = 2.46 and at an angle of attack of a = 0. The results are compared to the experimental data for the same conditions and the same configuration. Details of the mean flow field as well as the turbulence quantities have been presented. In addition, the computed base pressure distribution has been compared with the experiment. In general, the k-e turbulence model performs better in the near wake than the algebraic model and predicts the base pressure much better.
Book Synopsis Numerical Investigation of Supersonic Base Flow with Base Bleed by :
Download or read book Numerical Investigation of Supersonic Base Flow with Base Bleed written by and published by . This book was released on 1995 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: A zonal, implicit, time-marching Navier-Stokes computational technique has been used to compute the turbulent supersonic base flow over a cylindrical afterbody with base bleed. A critical element of calculating such flows is the turbulence model. Two eddy viscosity turbulence models have been used in the base region flow computations. These models include an algebraic turbulence model and a two-equation k-e model. The k-e equations are solved using an implicit algorithm, and calculations with the k-e model are extended up to the wall. Flow field computations have been performed for a cylindrical afterbody at M approx. = 2.46 and at an angle of attack of a = 0. The results are compared to the experimental data for the same conditions and the same configuration. Details of the mean flow field as well as the turbulence quantities have been presented. In addition, the computed base pressure distribution has been compared with the experiment. In general, the k-e turbulence model performs better in the near wake than the algebraic model and predicts the base pressure much better.
Book Synopsis A Numerical Investigation of Subsonic and Supersonic Flow Around Axisymmetric Bodies by : George D. Catalano
Download or read book A Numerical Investigation of Subsonic and Supersonic Flow Around Axisymmetric Bodies written by George D. Catalano and published by . This book was released on 2001-09 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational fluid dynamics (CFD) approach to predicting high- speed aerodynamic flow fields of interest to the U.S. Army Research Laboratory (ARL) has been carried out The aerodynamic problems of particular interest are: (1) supersonic flow past the aftbody of projectiles with base mass injection, (2) supersonic flow past the M549 projectile, and (3) subsonic, transonic, and supersonic flow past an M864 projectile with base bleed and wake combustion. The commercially available FLUENT (Fluent, Inc. FLUENT. Version 5.1.1, Lebanon, NH, 1999.) CFD code was utilized. The computational effort supports an ongoing ARL- sponsored experimental investigation. Of particular interest in the present investigation is the careful characterization of the various turbulence models employed in the CFD code. Additionally, the ease of use and set-up as well as the computational time will be described. An experimental effort (Dutton, J. C., and A. L. Addy. 'Fluid Dynamic Mechanisms and Interactions Within Separated Flows'. U.S. Army Research Office Research Grant DAAH04-93-G-0226 and the Department of Mechanical and Industrial Engineering, University of illinois, Urbana-Champagne, Urbana, IL, August 1998.) consisting of detailed laser Doppler velocimeter (LDV), particle image velocimeter (PIV), and high-speed wall pressure measurements has been made in axisymmetric and planar subsonic and supersonic flows with embedded separated regions. The present work seeks to predict similar flow fields computationally and to address areas of agreement and disagreement.
Book Synopsis Numerical Investigation of Supersonic Base Flow with Tangential Injection by : Gary Alan Sullins
Download or read book Numerical Investigation of Supersonic Base Flow with Tangential Injection written by Gary Alan Sullins and published by . This book was released on 1981 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Computations of Supersonic Base Flow with Special Emphasis on Turbulence Modeling by :
Download or read book Numerical Computations of Supersonic Base Flow with Special Emphasis on Turbulence Modeling written by and published by . This book was released on 1994 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A zonal, implicit, time-marching Navier-Stokes computational technique has been used to compute the turbulent supersonic base flow over cylindrical afterbodies. A critical element of calculating such flows is the turbulence model. Various eddy viscosity turbulence models have been used in the base region flow computations. These models include two algebraic turbulence models and a two-equation k-epsilon model. The k-epsilon equations are developed in a general coordinate system and solved using an implicit algorithm. Calculations with the k-epsilon model are extended up to the wall. Flow field computations have been performed for a cylindrical afterbody at M = 2.46 and at angle of attack alpha = 0. The results are compared to the experimental data for the same conditions and the same configuration. Details of the mean flow field as well as the turbulence quantifies have been presented. In addition, the computed base pressure distribution has been compared with the experiment. In general, the k-epsilon turbulence model performs better in the near wake than the algebraic models and predicts the base pressure much better. Base flow, Base pressure, Turbulence models, Wake, Supersonic flow.
Book Synopsis Theatrum chemicum, praecipuos electorum auctorum tractatus de chemiae et lapidis philosophici antiquitate, veritate... continens... by :
Download or read book Theatrum chemicum, praecipuos electorum auctorum tractatus de chemiae et lapidis philosophici antiquitate, veritate... continens... written by and published by . This book was released on 1659 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Simulation of Supersonic Compression Corners and Hypersonic Inlet Flows Using the RPLUS2D Code by : Kamlesh Kapoor
Download or read book Numerical Simulation of Supersonic Compression Corners and Hypersonic Inlet Flows Using the RPLUS2D Code written by Kamlesh Kapoor and published by . This book was released on 1994 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Adm Nasa Publisher :Independently Published ISBN 13 :9781792705748 Total Pages :30 pages Book Rating :4.7/5 (57 download)
Book Synopsis Numerical Simulation of Supersonic Compression Corners and Hypersonic Inlet Flows Using the Rplus2d Code by : National Aeronautics and Space Adm Nasa
Download or read book Numerical Simulation of Supersonic Compression Corners and Hypersonic Inlet Flows Using the Rplus2d Code written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-12-29 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A two-dimensional computational code, PRLUS2D, which was developed for the reactive propulsive flows of ramjets and scramjets, was validated for two-dimensional shock-wave/turbulent-boundary-layer interactions. The problem of compression corners at supersonic speeds was solved using the RPLUS2D code. To validate the RPLUS2D code for hypersonic speeds, it was applied to a realistic hypersonic inlet geometry. Both the Baldwin-Lomax and the Chien two-equation turbulence models were used. Computational results showed that the RPLUS2D code compared very well with experimentally obtained data for supersonic compression corner flows, except in the case of large separated flows resulting from the interactions between the shock wave and turbulent boundary layer. The computational results compared well with the experiment results in a hypersonic NASA P8 inlet case, with the Chien two-equation turbulence model performing better than the Baldwin-Lomax model. Kapoor, Kamlesh and Anderson, Bernhard H. and Shaw, Robert J. Glenn Research Center NASA-TM-106580, E-8840, NAS 1.15:106580 RTOP 537-02-23...
Book Synopsis Numerical Investigations on the Solution of the Non-linear Equation of Supersonic Flow by Finite Difference Methods by : Gerhard Seegmüller
Download or read book Numerical Investigations on the Solution of the Non-linear Equation of Supersonic Flow by Finite Difference Methods written by Gerhard Seegmüller and published by . This book was released on 1961 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Investigation of Supersonic Gas Flows Into Nanochannels Using an Unstructured 3D Direct Simulation Monte Carlo Method by : Wael G. Al-Kouz
Download or read book Investigation of Supersonic Gas Flows Into Nanochannels Using an Unstructured 3D Direct Simulation Monte Carlo Method written by Wael G. Al-Kouz and published by . This book was released on 2009 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This dissertation is devoted to the computational investigation of supersonic gas flows in rectangular nanochannels with scales between 100 nm and 1000 nm, using an unstructured three-dimensional Direct Simulation Monte Carlo (U3DSMC) methodology. This dissertation also contributes to the computational mathematics background of the U3DSMC method with validations and verifications at the micronscale and nanoscale, as well as with the investigation of the statistical fluctuations and errors associated with U3DSMC simulations at the nanoscale. The U3DSMC code is validated by comparisons with previous two dimensional DSMC simulations of flows in micron-scale rectangular channels. The simulation involves the supersonic flow of nitrogen into a microchannel with height of 1.2 m and width of 6 m. The free stream conditions correspond to a pressure of 72,450 Pa, Mach number, Knudsen number and mean free path nm. The U3DSMC centerline temperature, heat flux to the wall, and mean velocity as a function of the transverse direction are in very good agreement with previous 2D results. Statistical fluctuations and errors in U3DSMC have added significance in nanoscale domains because the number of real particles can be very small inside a computational cell. The effect of the number of samples, the number of computational particles in a Delaunay cell, and the Mach number on the fractional errors of density, velocity and temperature are investigated for uniform and pressure-driven nanoscale flows. The uniform nanoflow is implemented by applying a and free stream boundary condition with m-3, K, nm in a domain that requires resolution of a characteristic length scale nm. The pressure-driven flows consider a nanochannel of 500 nm height, 100 nm width and 4 m length. Subsonic boundary conditions are applied with inlet pressure 101,325 Pa and outlet pressure of 10132.5 Pa. The analysis shows that U3DSMC simulations at nanoscales featuring 10-30 particles per Delaunay cell result in statistical errors that are consistent with theoretical estimates. The rarefied flow of nitrogen with speed ratio of 2, 5, and 10, pressure of 10.132 kPa into rectangular nanochannels with height of 100, 500 and 1000 nm is investigated using U3DSMC. The investigation considers rarefaction effects with =0.481, 0.962, 4.81, geometric effects with nanochannel aspect ratios of (L/H) from AR=1, 10, 100 and back-pressure effects with imposed pressures from 0 to 200 kPa. The computational domain features a buffer region upstream of the inlet and the nanochannel walls are assumed to be diffusively reflecting at the free stream temperature of 273 K. The analysis is based on the phase space distributions as well as macroscopic flow variables sampled in cells along the centerline. The phase space distributions show the formation of a disturbance region ahead of the inlet due to slow particles backstreaming through the inlet and the formation of a density enhancement with its maximum inside the nanochannel. The velocity phase-space distributions show a low-speed particle population generated inside the nanochannel due to wall collisions which is superimposed with the free stream high-speed population. The mean velocity decreases, while the number density increases in the buffer region. The translational temperature increases in the buffer region and reaches its maximum near the inlet. For AR=10 and 100 nanochannels the gas reaches near equilibrium with the wall temperature. The heat transfer rate is largest near the inlet region where non-equilibrium effects are dominant. For =0.481, 0.962, 4.81, vacuum back pressure, and AR=1, the nanoflow is supersonic throughout the nanochannel, while for AR=10 and 100, the nanoflow is subsonic at the inlet and becomes sonic at the outlet. For =0.962, AR=1, and imposed back pressure of 120 kPa and 200 kPa, the nanoflow becomes subsonic at the outlet. For =0.962 and AR=10, the outlet pressure nearly matches the imposed back pressure with the nanoflow becoming sonic at 40 kPa and subsonic at 100 kPa. Heat transfer rates at the inlet and mass flow rates at the outlet are in good agreement with those obtained from theoretical free-molecular models. The flows in these nanochannels share qualitative characteristics found in microchannels ad well as continuum compressible flows in channels with friction and heat loss. The rarefied flow of nitrogen with speed ratio of 2, 5, 10, at an atmospheric pressure of 101.32 kPa into rectangular nanochannels with height of 100 and 500 nm is investigated using U3DSMC. The investigation considers rarefaction effects with =0.0962 and 4.81, geometric effects with nanochannel aspect ratios of (L/H) of AR=1 and 10 and vacuum back-pressure. Phase plots and sample-averaged macroscopic parameters are used in the analysis. Under vacuum back pressure the centerline velocity decreases in the buffer region from its free stream value. For 0.481, 0.0962 and AR=1 the Mach number is supersonic at the inlet and remains supersonic throughout the nanochannel. For 0.481, 0.0962 and AR=10, the flow becomes subsonic at the inlet and shows a sharp increase in pressure. The Mach number, subsequently, increases and reaches the sonic point at the outlet. For 0.481, 0.0962 and AR=1 the translational temperature reaches a maximum near the inlet and decreases monotonically up to the outlet. For 0.481, 0.0962 and AR=10, the translational temperature reaches a maximum near the inlet and then decreases to come in near equilibration with the wall temperature of 273 K.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781722428426 Total Pages :40 pages Book Rating :4.4/5 (284 download)
Book Synopsis Numerical Simulation of Supersonic and Hypersonic Inlet Flow Fields by : National Aeronautics and Space Administration (NASA)
Download or read book Numerical Simulation of Supersonic and Hypersonic Inlet Flow Fields written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-09 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes the research performed by North Carolina State University and NASA Ames Research Center under Cooperative Agreement NCA2-719, 'Numerical Simulation of Supersonic and Hypersonic Inlet Flow Fields". Four distinct rotated upwind schemes were developed and investigated to determine accuracy and practicality. The scheme found to have the best combination of attributes, including reduction to grid alignment with no rotation, was the cell centered non-orthogonal (CCNO) scheme. In 2D, the CCNO scheme improved rotation when flux interpolation was extended to second order. In 3D, improvements were less dramatic in all cases, with second order flux interpolation showing the least improvement over grid aligned upwinding. The reduction in improvement is attributed to uncertainty in determining optimum rotation angle and difficulty in performing accurate and efficient interpolation of the angle in 3D. The CCNO rotational technique will prove very useful for increasing accuracy when second order interpolation is not appropriate and will materially improve inlet flow solutions. Mcrae, D. Scott and Kontinos, Dean A. Unspecified Center NCA2-719...
Book Synopsis Numerical Studies of Low-Density Two-Dimensional Hypersonic Flows by Using the Navier-Stokes and Burnett Equations with Nonequilibrium Real Gas Effects by :
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.
Book Synopsis Spurious Numerical Oscillations in Numerical Simulation of Supersonic Flows Using Shock Capturing Schemes by : Theodore K. Lee
Download or read book Spurious Numerical Oscillations in Numerical Simulation of Supersonic Flows Using Shock Capturing Schemes written by Theodore K. Lee and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
