Direct Numerical Simulation of Detonation-Turbulence Interaction PDF Download
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Author: Monika Chauhan Rai
Publisher:
ISBN: 9783659443152
Category :
Languages : en
Pages : 0
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Author: Monika Chauhan Rai
Publisher:
ISBN: 9783659443152
Category :
Languages : en
Pages : 0
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Author: Sarah Moussa Hussein
Publisher:
ISBN:
Category : Numerical analysis
Languages : en
Pages : 192
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Book Description
Turbulence has been a topic of scientific research for years. Characterized by unorganized chaotic motion and irregular fluctuations, it persists as one of the most challenging topics in fluid mechanics despite volumes of documented research and crucial findings. This begs the question: What is turbulence and why is it so challenging? Turbulence research studies cover a wide spectrum of branches from fundamental flow propagation to different turbulence interactions. This research project investigates the simplest class of turbulent flow studies, homogeneous isotropic turbulence. In a quest to advance the fundamental understanding of turbulence physics, a direct numerical simulation tool is developed. The tool generates a turbulent periodic cube with vortical fluctuations and three interaction case studies. The evolution of the velocity in time is derived from the Navier-Stokes equations. These governing equations are integrated, along with initial and boundary conditions, to formulate turbulence. Fully-developed turbulence is achieved when the Tavoularis (1978) criterion of axial velocity variation is met. Output data sets are collected for numerical analysis. The turbulence periodic cube geometry is assessed for its applicability in this study. The simplified structure is found to be efficient and facilitated. The interaction case studies of shock-turbulence and detonation-turbulence are compared to an unforced flow interaction. The case studies are statistically analyzed and visualized yielding important conclusions on the effects of the fluctuations, heat release, detonation inherent length scale, and detonation intrinsic instability on the flow behavior. A mutual interaction is found between the turbulence structures and the strong detonation wave. An extension of the long-standing Tavoularis velocity skewness factor is suggested. The proposed velocity skewness vector quantifies the variation of the three velocity components in the three Cartesian coordinates. This comprehensive expression highlights the contribution of the three-dimensional velocity fluctuations to the turbulence state.
Author: Sangsan Lee
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Monika Chauhan
Publisher:
ISBN:
Category :
Languages : en
Pages :
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A numerical study was performed to investigate the effect of preshock turbulence on detonation wave properties. A direct numerical simulation was performed on the chemically reactive Navier-Stokes equations using a Runge-Kutta scheme and a fifth-order WENO spatial discretization. A simple one-step chemical kinetics model was used in the study. The main objective of the research is to examine the behavior of the turbulence when subjected to a strong shock with heat release. The evolution of the turbulent Mach number, lengthscales (Taylor microscale and Kolmogorov scale), turbulent kinetic energy, Reynolds stress, auto-correlations with heat release and activation energy is examined. Shock-turbulence interaction have been the subject of research for over the decades but there is no significant study that has yet been made on Detonation-Turbulence interaction. This research is helpful in practical applications such as safe handling of the fuels, promoting detonations for detonation engines etc. The results show a marked influence of preshock perturbations on the postshock statistics. Detonation-Turbulence interaction resulted in higher amplifications of turbulence statistics and parameters like turbulent Mach number, turbulent length scales (i.e. Taylor microscale, Kolmogorov length scale etc.), turbulent kinetic energy, velocity fluctuations, auto-correlations etc. The detonation event triggers a self-excited instability, evidenced by the velocity fluctuations and further by spacetime correlation functions. Also, the alteration to the limit cycle structure supported by unstable waves close to their critical points is highlighted. The effect of reactivity and fluid acceleration in the postshock region are examined by comparison with the non-reactive analog. The possibility that significant forcing can lead to hot-spot formation is investigated by considering temperature probability distribution functions in the reaction zone. The separate effect of vortical and entropic fluctuations is considered.
Author:
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ISBN: 9783030447199
Category : Big data
Languages : en
Pages :
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This book presents methodologies for analysing large data sets produced by the direct numerical simulation (DNS) of turbulence and combustion. It describes the development of models that can be used to analyse large eddy simulations, and highlights both the most common techniques and newly emerging ones. The chapters, written by internationally respected experts, invite readers to consider DNS of turbulence and combustion from a formal, data-driven standpoint, rather than one led by experience and intuition. This perspective allows readers to recognise the shortcomings of existing models, with the ultimate goal of quantifying and reducing model-based uncertainty. In addition, recent advances in machine learning and statistical inferences offer new insights on the interpretation of DNS data. The book will especially benefit graduate-level students and researchers in mechanical and aerospace engineering, e.g. those with an interest in general fluid mechanics, applied mathematics, and the environmental and atmospheric sciences.
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Category :
Languages : en
Pages : 3
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Author: Jan Gerard Wissink
Publisher:
ISBN: 9789036705349
Category :
Languages : en
Pages : 135
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Author:
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ISBN:
Category :
Languages : en
Pages : 57
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The target of this SciDAC Science Application was to develop a new capability based on high-order and high-resolution schemes to simulate shock-turbulence interactions and multi-material mixing in planar and spherical geometries, and to study Rayleigh-Taylor and Richtmyer-Meshkov turbulent mixing. These fundamental problems have direct application in high-speed engineering flows, such as inertial confinement fusion (ICF) capsule implosions and scramjet combustion, and also in the natural occurrence of supernovae explosions. Another component of this project was the development of subgrid-scale (SGS) models for large-eddy simulations of flows involving shock-turbulence interaction and multi-material mixing, that were to be validated with the DNS databases generated during the program. The numerical codes developed are designed for massively-parallel computer architectures, ensuring good scaling performance. Their algorithms were validated by means of a sequence of benchmark problems. The original multi-stage plan for this five-year project included the following milestones: 1) refinement of numerical algorithms for application to the shock-turbulence interaction problem and multi-material mixing (years 1-2); 2) direct numerical simulations (DNS) of canonical shock-turbulence interaction (years 2-3), targeted at improving our understanding of the physics behind the combined two phenomena and also at guiding the development of SGS models; 3) large-eddy simulations (LES) of shock-turbulence interaction (years 3-5), improving SGS models based on the DNS obtained in the previous phase; 4) DNS of planar/spherical RM multi-material mixing (years 3-5), also with the two-fold objective of gaining insight into the relevant physics of this instability and aiding in devising new modeling strategies for multi-material mixing; 5) LES of planar/spherical RM mixing (years 4-5), integrating the improved SGS and multi-material models developed in stages 3 and 5. This final report is outlined as follows. Section 2 shows an assessment of numerical algorithms that are best suited for the numerical simulation of compressible flows involving turbulence and shock phenomena. Sections 3 and 4 deal with the canonical shock-turbulence interaction problem, from the DNS and LES perspectives, respectively. Section 5 considers the shock-turbulence inter-action in spherical geometry, in particular, the interaction of a converging shock with isotropic turbulence as well as the problem of the blast wave. Section 6 describes the study of shock-accelerated mixing through planar and spherical Richtmyer-Meshkov mixing as well as the shock-curtain interaction problem In section 7 we acknowledge the different interactions between Stanford and other institutions participating in this SciDAC project, as well as several external collaborations made possible through it. Section 8 presents a list of publications and presentations that have been generated during the course of this SciDAC project. Finally, section 9 concludes this report with the list of personnel at Stanford University funded by this SciDAC project.
Author: M.Y. Hussaini
Publisher: Springer
ISBN: 9780792330868
Category : Science
Languages : en
Pages : 372
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These two volumes are concerned with current technologically important issues of transition, turbulence and combustion. Topics covered in transition include linear and nonlinear stability, direct and large-eddy simulation and phenomenological modelling of the transition zone. In turbulence, interest was focused on second-order closures and the formulation of near-wall corrections to existing high Reynolds number models, and closure model development based on turbulent flow structures and RNG theory. Topics covered in combustion include counterflow diffusion flames, development of novel mixing enhancement techniques for non-premixed combustion, and methods of modelling the interaction between turbulence and chemical kinetics. This collection of papers from leading researchers represents as yet unpublished state-of-the-art research, resulting in a very valuable tool for scientists and students working in areas of turbulence, transition and combustion.
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Category :
Languages : en
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