Intermittency in Transitional Shear Flows

Intermittency in Transitional Shear Flows PDF

Author: Yohann Duguet

Publisher: MDPI

Published: 2021-08-31

Total Pages: 180

ISBN-13: 3036509429

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This book contains original peer-reviewed articles written by some of the most prominent international physicists active in the field of hydrodynamics. The topic is entirely devoted to the study of the transitional regimes of incompressible viscous flow found at the onset of turbulent flows. Nine articles written for this 2020 Special Issue of the journal Entropy (MDPI) have been gathered at the crossroads of fluid mechanics, statistical physics, complexity theory, and applied mathematics. They include experimental, analytic, and computational material of an academic level that has not been published anywhere else.

Intermittency in Transitional Shear Flows

Intermittency in Transitional Shear Flows PDF

Author: Yohann Duguet

Publisher:

Published: 2021

Total Pages: 180

ISBN-13: 9783036509433

DOWNLOAD EBOOK →

This book contains original peer-reviewed articles written by some of the most prominent international physicists active in the field of hydrodynamics. The topic is entirely devoted to the study of the transitional regimes of incompressible viscous flow found at the onset of turbulent flows. Nine articles written for this 2020 Special Issue of the journal Entropy (MDPI) have been gathered at the crossroads of fluid mechanics, statistical physics, complexity theory, and applied mathematics. They include experimental, analytic, and computational material of an academic level that has not been published anywhere else.

Physics of Transitional Shear Flows

Physics of Transitional Shear Flows PDF

Author: Andrey V. Boiko

Publisher: Springer Science & Business Media

Published: 2011-09-15

Total Pages: 286

ISBN-13: 9400724985

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Starting from fundamentals of classical stability theory, an overview is given of the transition phenomena in subsonic, wall-bounded shear flows. At first, the consideration focuses on elementary small-amplitude velocity perturbations of laminar shear layers, i.e. instability waves, in the simplest canonical configurations of a plane channel flow and a flat-plate boundary layer. Then the linear stability problem is expanded to include the effects of pressure gradients, flow curvature, boundary-layer separation, wall compliance, etc. related to applications. Beyond the amplification of instability waves is the non-modal growth of local stationary and non-stationary shear flow perturbations which are discussed as well. The volume continues with the key aspect of the transition process, that is, receptivity of convectively unstable shear layers to external perturbations, summarizing main paths of the excitation of laminar flow disturbances. The remainder of the book addresses the instability phenomena found at late stages of transition. These include secondary instabilities and nonlinear features of boundary-layer perturbations that lead to the final breakdown to turbulence. Thus, the reader is provided with a step-by-step approach that covers the milestones and recent advances in the laminar-turbulent transition. Special aspects of instability and transition are discussed through the book and are intended for research scientists, while the main target of the book is the student in the fundamentals of fluid mechanics. Computational guides, recommended exercises, and PowerPoint multimedia notes based on results of real scientific experiments supplement the monograph. These are especially helpful for the neophyte to obtain a solid foundation in hydrodynamic stability. To access the supplementary material go to extras.springer.com and type in the ISBN for this volume.

Subcritical Transition to Turbulence in Shear Flows

Subcritical Transition to Turbulence in Shear Flows PDF

Author:

Publisher:

Published: 2014

Total Pages: 100

ISBN-13:

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The theme of this thesis is transition to turbulence in linearly stable shear flows. Laminar-turbulent intermittency and hysteresis are typical feature of these flows at transitional Reynolds numbers, characterizing a subcritical scenario. Subcritical transition is a dynamically rich phenomenon in nature and has been scrutinized for over a century. The critical Reynolds number for the transition and its physical mechanisms are fundamental problems in fluid dynamics and are still not fully understood. These questions are addressed in this thesis by performing direct numerical simulations of...

Modeling of Flow Transition Using an Intermittency Transport Equation

Modeling of Flow Transition Using an Intermittency Transport Equation PDF

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-06-03

Total Pages: 34

ISBN-13: 9781720628866

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A new transport equation for intermittency factor is proposed to model transitional flows. The intermittent behavior of the transitional flows is incorporated into the computations by modifying the eddy viscosity, mu(sub t), obtainable from a turbulence model, with the intermittency factor, gamma: mu(sub t, sup *) = gamma.mu(sub t). In this paper, Menter's SST model (Menter, 1994) is employed to compute mu(sub t) and other turbulent quantities. The proposed intermittency transport equation can be considered as a blending of two models - Steelant and Dick (1996) and Cho and Chung (1992). The former was proposed for near-wall flows and was designed to reproduce the streamwise variation of the intermittency factor in the transition zone following Dhawan and Narasimha correlation (Dhawan and Narasimha, 1958) and the latter was proposed for free shear flows and was used to provide a realistic cross-stream variation of the intermittency profile. The new model was used to predict the T3 series experiments assembled by Savill (1993a, 1993b) including flows with different freestream turbulence intensities and two pressure-gradient cases. For all test cases good agreements between the computed results and the experimental data are observed.Suzen, Y. B. and Huang, P. G.Glenn Research CenterINTERMITTENCY; TRANSPORT THEORY; EDDY VISCOSITY; TURBULENT FLOW; TURBULENCE MODELS; NAVIER-STOKES EQUATION; PRESSURE GRADIENTS; SHEAR FLOW; WALL FLOW; TRANSITION FLOW

Intermittency Equation for Transitional Flow

Intermittency Equation for Transitional Flow PDF

Author: Ekachai Juntasaro

Publisher:

Published: 2022

Total Pages: 0

ISBN-13: 9783031039430

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This book provides the intermittency equation that is derived a priori. Since the intermittency equation is mathematically obtained, the resulting gamma transition model no longer requires any extra parameters and terms to explicitly account for free-stream turbulence and pressure gradient like the previous transition models. Instead, the present gamma transition model can naturally predict natural transition and effects of free-stream turbulence and pressure gradient on the transition process. Furthermore, the present gamma transition model requires much fewer model constants than the previous transition models. The book is beneficial for CFD researchers in industry and academia who confront modern complex applications involving simultaneously laminar, transitional and turbulent flow regimes, and ideally relevant to graduate students in applied physics, applied mathematics and engineering who are interested in the world of laminar-to-turbulent transition modeling in CFD, or would like to further advance more realistic transition models in the future.

Conditional Sampling and Detection Methods in Transitional Flow

Conditional Sampling and Detection Methods in Transitional Flow PDF

Author: Mohsen Jahanmiri

Publisher: Booktango

Published: 2013-09-13

Total Pages: 41

ISBN-13: 1468938258

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The separation of unsteadiness (or intermittency) and turbulence is the key to improve understanding of the statistical behavior of the transitional boundary layer flow. In this book an attempt is made to review the different methods used for the detection of turbulent and non-turbulent interface in transitional flows. In this regard, methods for generating the intermittency function, conditional averaging and sampling are discussed. The salient features of each technique is also explained. At the end few examples on interface detection in jet flows are added.