Download or read book Three dimensional Simulations of Compressible Mixing Layers written by Laurine Joyce Leep and published by . This book was released on 1992 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Compressibility Effects of Three dimensional Mixing Layer by Numerical Simulation written by Itaru Hataue and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Physical and Numerical Study of Three Dimensional Skewed Mixing Layers written by and published by . This book was released on 1996 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of skewing the two freestreams on the development of a compressible mixing layer was studied. The results of stability analysis show that skewing has the simultaneous effect of increasing the effective velocity ratio, which is a destabilizing effect, and increasing the effective, convective Mach number, which is a stabilizing effect. Direct numerical simulations of a spatially evolving mixing layer with equal velocity magnitude but skewed in opposite directions were conducted to study the non-linear evolution. Three skewing angles were considered: 30, 60, and 90 deg. For the low skewing angle cases, the mixing layer rolls up and forms a pattern of streamwise vortices. For the 90 deg case, vortex breakdown was observed, which significantly enhances the mixing. For high Mach numbers, oblique waves are more unstable which form a pattern of streamwise vortices with increasing spanwise undulation. The skewing effect can be practically realized by adding swirl to a circular mixing layer. Results of stability analysis show that adding a small amount of swirl near the center of the mixing layer significantly enhances the maximum amplification rate, and the enhancement sustains under compressible conditions. The disturbance energy budget shows that a significant of disturbance energy is extracted from the shear in the swirl component.

Download or read book Advances in Compressible Turbulent Mixing written by and published by . This book was released on 1992 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Numerical Investigation of Skewed Mixing Layers written by Stanford University. Thermosciences Division. Thermosciences Division and published by . This book was released on 1995 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of a Hybrid RANS LES Method for Compressible Mixing Layer Simulations written by Nicholas J. Georgiadis and published by . This book was released on 2001 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comparison of Several Numerical Methods for Simulation of Compressible Shear Layers written by Christopher A. Kennedy and published by . This book was released on 1997 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct and Large Eddy Simulation I written by Peter R. Voke and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is a truism that turbulence is an unsolved problem, whether in scientific, engin eering or geophysical terms. It is strange that this remains largely the case even though we now know how to solve directly, with the help of sufficiently large and powerful computers, accurate approximations to the equations that govern tur bulent flows. The problem lies not with our numerical approximations but with the size of the computational task and the complexity of the solutions we gen erate, which match the complexity of real turbulence precisely in so far as the computations mimic the real flows. The fact that we can now solve some turbu lence in this limited sense is nevertheless an enormous step towards the goal of full understanding. Direct and large-eddy simulations are these numerical solutions of turbulence. They reproduce with remarkable fidelity the statistical, structural and dynamical properties of physical turbulent and transitional flows, though since the simula tions are necessarily time-dependent and three-dimensional they demand the most advanced computer resources at our disposal. The numerical techniques vary from accurate spectral methods and high-order finite differences to simple finite-volume algorithms derived on the principle of embedding fundamental conservation prop erties in the numerical operations. Genuine direct simulations resolve all the fluid motions fully, and require the highest practical accuracy in their numerical and temporal discretisation. Such simulations have the virtue of great fidelity when carried out carefully, and repre sent a most powerful tool for investigating the processes of transition to turbulence.

Download or read book Transition to Turbulence and Effect of Initial Conditions on 3D Compressible Mixing in Planar Blast wave driven Systems written by and published by . This book was released on 2004 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E.M. Campbell, Laser Part. Beams, 9(2), 209 (1991)] are presented. Using the multi-physics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L.H. Howell and J.A. Greenough, J. Comp. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pre-transition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernova are discussed.

Download or read book On the Turbulence generated Sound and Control of Compressible Mixing Layers written by Randall R. Kleinman and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A mixing layer is a common model used to study the noise generation and mixing characteristics of the near-nozzle region of jets. This work presents three separate but related studies that investigate sound generation and active control for noise mitigation and mixing enhancement of such mixing layers. High-fidelity direct numerical simulations of temporal and spatial mixing layers are used for this in two and three dimensions. The first study investigates the role of turbulence scales in generating the radiated far-field sound from temporally-developing, Mach 0.9 mixing layers. To do this, four mixing layers were simulated, starting from the same initial conditions but with Reynolds numbers that varied by a factor of twelve. Above a momentum thickness Reynolds number of 300, all the mixing layers radiate over 85 percent of the acoustic energy of the apparently asymptotically high-Reynolds-number value we are able to compute. Wavenumber spectra of turbulence energy and pressure show the expected Reynolds number dependence: the two highest Reynolds number simulations show evidence of an inertial range and Kolmogorov scaling at the highest wavenumbers. Far-field pressure spectra all decay much more rapidly with wavenumber than the corresponding near-field spectra and show significantly less sensitivity to Reynolds number. Low wavenumbers account for nearly all of the radiated acoustic energy. Implications of these results for jet noise large-eddy simulations are discussed. The second study uses direct numerical simulations of Mach 1.3 mixing layers to characterize the physical mechanisms of flow actuation by localized arc-filament plasma actuators. A validated numerical model of the actuator is devised and placed, as in corresponding experiments, in a cavity in the nozzle near its exit. A rapid Joule heating caused by the plasma is thought to be the root mechanism of flow actuation based upon experimental observation. Simulations show that in the confined space of the cavity, the actuator creates a rapid flow expansion, which transfers fluid mass upward and outward creating a synthetic-jet-like perturbation to the boundary layer. The actuation promotes vortex creation much closer to the nozzle than the baseline flow without actuation, increases the layer growth rate, and organizes the large flow structures. Placing the actuator in a cavity of half the original width increases the velocities responsible for the jet-like boundary layer perturbation and downstream mixing layer growth rate. An actuator model designed to produce the same pressure response without the rapid heating provides similar control authority. The final study implements an automatic optimization procedure based on the adjoint of the perturbed and linearized flow equations. An algorithm is formulated to provide optimized control actuation for noise reduction and mixing enhancement objectives. The method is demonstrated to be successful on several model problems in two and three dimensions, in cases both with an explicitly represented "splitter" plate and cases where an appropriate inflow condition is imposed in its place. Cost functionals for noise reduction and mixing enhancement based on cross-stream velocity and pressure are formulated. Two-dimensional mixing layers with near-wall control are presented with velocity- and pressure-based spreading enhancement cost functionals. Both controls are able to maximize their respective cost functionals by over 50% and increase mixing layer thickness by 10-15% over the optimization time horizon. A three-dimensional, turbulent (spatially-developing) mixing layer is simulated and optimized with a noise reduction cost functional. The control successfully reduces the noise on a target plane below the mixing layer by 28% after 4 line search iterations of the optimization scheme.

Download or read book Stability of the Compressible Reacting Mixing Layer written by Dongshin Shin and published by . This book was released on 1992 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulations of Compressible Mixing Layers with High order ENO shemes written by Tilo Lumpp and published by . This book was released on 1994 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct and Large Eddy Simulation IV written by Bernard Geurts and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of the 2001 DLES4 workshop. It describes and discusses state-of-the-art modeling and simulation approaches for complex flows. Fundamental turbulence and modeling issues but also elements from modern numerical analysis are at the heart of this field of interest.

Download or read book Spatial Stability of a Compressible Mixing Layer written by T. L. Jackson and published by . This book was released on 1988 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct and Large Eddy Simulation III written by Peter R. Voke and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: The practical importance of turbulence led the U.K. Royal Academy of Engineering to launch an Initiative on Turbulence, the most important outcome of which was the definition and agreement of the 1999 Newton Institute Research Programme on Turbulence. The main aim of the- month programme, held at the institute in Cambridge, was to bring together the mathematics and engineering communities involved in the turbulence area to address the many problems and to map out future strategy. As a part of the Research Programme, a Symposium on Direct and Large-Eddy Simulation was jointly organised with ERCOFfAC through their Large-Eddy Simulation Interest Group and took place in May 1999. Two previous ERCOFf AC Workshops had already taken place on these closely related varieties of turbulence simulation, at The University of Surrey in 1994 and at Universite Joseph Fourier, Grenoble in 1996. The Symposium at Cambridge was therefore the third in the ERCOFTAC series, enhanced by the presence of leading figures in the field from Europe and the USA who were resident at INI for that period of the Research Programme. Professors M. Germano, A. Leonard, J. Jimenez, R. Kerr and S. Sarkar gave the invited lectures, text versions of which will be found in this volume. As occurred at the previous two ERCOFT AC workshops, there were almost one hundred participants mostly from Europe but including some from Japan and the USA, including on this occasion resident scientists of the INI Research Programme.

Download or read book Direct and Large Eddy Simulation II written by Jean-Pierre Chollet and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress in the numerical simulation of turbulence has been rapid in the 1990s. New techniques both for the numerical approximation of the Navier-Stokes equations and for the subgrid-scale models used in large-eddy simulation have emerged and are being widely applied for both fundamental and applied engineering studies, along with novel ideas for the performance and use of simulation for compressible, chemically reacting and transitional flows. This collection of papers from the second ERCOFTAC Workshop on Direct and Large-Eddy Simulation, held in Grenoble in September 1996, presents the key research being undertaken in Europe and Japan on these topics. Describing in detail the ambitious use of DNS for fundamental studies and of LES for complex flows of potential and actual engineering importance, this volume will be of interest to all researchers active in the area.

Download or read book Direct and Large Eddy Simulation written by Bernard J. Geurts and published by Walter de Gruyter GmbH & Co KG. This book was released on 2022-12-05 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of the mathematics and physics behind the simulation of turbulent flows and discusses in detail (i) the phenomenology of turbulence in fluid dynamics, (ii) the role of direct and large-eddy simulation in predicting these dynamics, (iii) the multiple considerations underpinning subgrid modelling, and, (iv) the issue of validation and reliability resulting from interacting modelling and numerical errors.