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A Priori Study Of Subgrid Scale Flux Of A Passive Scalar In Isotropic Homogeneous Turbulence
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Book Synopsis A Priori Study of Subgrid-scale Flux of a Passive Scalar in Isotropic Homogeneous Turbulence by :
Download or read book A Priori Study of Subgrid-scale Flux of a Passive Scalar in Isotropic Homogeneous Turbulence written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We perform a direct numerical simulation (DNS) of forced homogeneous isotropic turbulence with a passive scalar that is forced by mean gradient. The DNS data are used to study the properties of subgrid-scale flux of a passive scalar in the framework of large eddy simulation (LES), such as alignment trends between the flux, resolved, and subgrid-scale flow structures. It is shown that the direction of the flux is strongly coupled with the subgrid-scale stress axes rather than the resolved flow quantities such as strain, vorticity, or scalar gradient. We derive an approximate transport equation for the subgrid-scale flux of a scalar and look at the relative importance of the terms in the transport equation. A particular form of LES tensor-viscosity model for the scalar flux is investigated, which includes the subgrid-scale stress. Effect of different models for the subgrid-scale stress on the model for the subgrid-scale flux is studied.
Book Synopsis Experimental Studies of Homogeneous Passive Scalars in Grid-generated Turbulence by : Anuvat Sirivat
Download or read book Experimental Studies of Homogeneous Passive Scalars in Grid-generated Turbulence written by Anuvat Sirivat and published by . This book was released on 1983 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Data-driven and Nonlocal Approaches in Modeling, Analysis and Simulation of Turbulent Mixing Phenomena by : Ali Akhavan Safaei
Download or read book Data-driven and Nonlocal Approaches in Modeling, Analysis and Simulation of Turbulent Mixing Phenomena written by Ali Akhavan Safaei and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overreaching goal of this study is utilizing data-driven methods and sophisticated mathematical tools for modeling and simulation of turbulent transport of passive scalars. We focus on embedding the intrinsic nonlocal nature of the turbulence into our models. We study the nonlocal dynamics in the context of (i) subgrid-scale (SGS) modeling for largeeddy simulation (LES), and (ii) the turbulent cascade under large-scale anisotropic sources. Moreover, we implement stochastic modeling methodologies to systematically investigate the contributing mechanisms leading a high-speed hydrodynamic transport system into instability and chaos, as well as discovering the anomalies in the featured characteristics of the transport.First, we present a computational-statistical framework to obtain high-fidelity data for homogeneous isotropic turbulent (HIT) flow and passive scalar transport. A parallel implementation of the well-known pseudo-spectral method in addition to the comprehensive record of the statistical and small-scale quantities of the turbulent transport are offered for executing on distributed memory CPU-based supercomputers.Afterwards, we investigate the inherent nonlocal behavior of the SGS passive scalar flux through studying its two-point statistics obtained from the filtered direct numerical simulation (DNS) data for passive scalar transport in HIT flow. We propose a statistical model for microscopic SGS motions by considering the filtered Boltzmann transport equation (FBTE) for passive scalar. In FBTE, we approximate the filtered equilibrium distribution with an Îł-stable Levy distribution that incorporates a power-law behavior to resemble the observed nonlocal statistics of SGS scalar flux. Through generic ensemble-averaging of FBTE, we formulate a continuum-level closure model for the SGS scalar flux appearing in terms of a fractional-order Laplacian that is a nonlocal operator.Moreover, we revisit the spectral transfer model for the turbulent intensity in the passive scalar transport (under large-scale anisotropic forcing), and a subsequent modification to the scaling of scalar variance cascade is presented. Accordingly, we obtain a revised scalar transport model using fractional-order Laplacian operator that facilitates the robust inclusion of the nonlocal effects originated from large-scale anisotropy transferred across the multitude of scales in the turbulent cascade. We provide an a priori estimate for the nonlocal model, and examine the model through a new DNS. We conduct a detailed analysis on the evolution of the scalar variance, high-order statistics of scalar gradient, and two-point statistical metrics of the turbulent transport to compare the developed nonlocal model and its standard version.In another study, a deep learning surrogate model in the form of fully connected feedforward neural networks is developed to predict the SGS scalar flux in the context of large eddy simulation of turbulent transport. The deep neural network (DNN) model is trained and validated using filtered DNS dataset at P eλ = 240, Sc = 1 that includes the filtered scalar and velocity gradients as input features. Using the transfer learning concept, we generalize the performance of this trained model to turbulent scalar transport regimes with higher P eλ and Sc numbers with a relatively low amount of data and computations.Finally, in stochastic modeling of hydrodynamic transport, we study the flow dynamics inside a high-speed rotating cylinder after introducing strong symmetry-breaking disturbance factors at cylinder wall motion. We perform a statistical analysis on the fluctuating fields characterizing the fingerprints and measures of intense and rapidly evolving non-Gaussian behavior through space and time. Such non-Gaussian statistics essentially emerge and evolve due to an intensified presence of coherent vortical motions initially triggered by the flow instability due to symmetry-breaking rotation of the cylinder. We show that this mechanism causes significant memory effects in the flow so that noticeable anomaly in the time-scaling of enstrophy record is observed in the long run apart from the onset of instability.
Book Synopsis Mixing of a Passive Scalar in Isotropic and Sheared Homogeneous Turbulence by : E. Shirani
Download or read book Mixing of a Passive Scalar in Isotropic and Sheared Homogeneous Turbulence written by E. Shirani and published by . This book was released on 1981 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to calculate the velocity and passive scalar fields in homogeneous turbulent flows, the three-dimensional, time-dependent equations of motion and the diffusion equation have been solved numerically.
Book Synopsis Turbulent Premixed Flames by : Nedunchezhian Swaminathan
Download or read book Turbulent Premixed Flames written by Nedunchezhian Swaminathan and published by Cambridge University Press. This book was released on 2011-04-25 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: A work on turbulent premixed combustion is important because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made on this topic, and this cohesive volume contains contributions from international experts on various subtopics of the lean premixed flame problem.
Book Synopsis Investigation of Dynamic Subgrid-scale and Wall Models for Turbulent Boundary Layers by : Hyun Ji Bae
Download or read book Investigation of Dynamic Subgrid-scale and Wall Models for Turbulent Boundary Layers written by Hyun Ji Bae and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Most turbulent flows cannot be calculated by direct numerical simulation (DNS) of the Navier-Stokes equations because the range of scales of motions is so large that the computational cost becomes prohibitive. In large-eddy simulation (LES), only the large eddies are resolved and the effect of the small scales on the larger ones is modeled through a subgrid-scale (SGS) model. Given that accurate representation and prediction of turbulence is needed in many engineering and scientific applications, development of accurate yet computationally efficient SGS models is an important task. Additionally, wall models are necessary to overcome the prohibitive near-wall resolution requirements for the large scales in high-Reynolds-number turbulent flows. This study investigates a new SGS model, the anisotropic minimum-dissipation (AMD) model, which is constructed to provide the minimum eddy viscosity required to avoid energy pile-up in the smallest resolved scales. The AMD model is successfully applied in simulations of decaying grid turbulence for isotropic grids, and temporal mixing layer and turbulent channel flow for anisotropic grids. This model is more cost-effective than the dynamic Smagorinsky model (DSM) and appropriately switches off in laminar and transitional flows. The formulation of the AMD model is extended to the transport equation for scalar concentration to model the subfilter scalar flux. The performance of the model is tested in the simulation of high-Reynolds-number rough-wall boundary-layer flow with a constant and uniform surface scalar flux. The simulation results obtained from the scalar model show good agreement with well-established empirical correlations and theoretical predictions of the resolved flow statistics. The accuracy of the SGS models is tested by studying the convergence properties in the outer region of a channel flow at moderate to high Reynolds numbers. As LES requires scale separation of the resolved and subgrid scales, the convergence study must be conducted in high-Reynolds-number flows. However, the analysis shows that the errors from the near-wall region are dominant for SGS models in usual LES grid resolutions, where the grid is not refined in the wall-parallel directions. For evaluation of SGS models, in order to overcome the grid requirements imposed by the near-wall turbulent eddies as well as the errors accumulated near the wall, a possible solution is to isolate the outer region of wall-bounded flows. This is made possible by one of two ways: suppressing the near-wall dynamics through a modified wall, or supplying the correct mean stress at the wall with a wall model. Theoretical analysis of the error scaling of SGS models for the mean velocity profile, turbulence intensities, and energy spectra is performed. The numerical convergence studies of the DSM and AMD models show that both models are first-order accurate in terms of the mean velocity profile, which is consistent with the theoretical assessments. Lastly, a new dynamic wall model based on the slip boundary condition is proposed. The use of the slip boundary condition for wall-modeled LES is motivated through theoretical analysis and a priori study of DNS data. The effect of the slip boundary condition on the one-point statistics of the flow is investigated in LES of turbulent channel and flat-plate turbulent boundary layer. The slip boundary condition provides a framework to compensate for the deficit or excess of mean momentum at the wall. The requirements for the slip lengths to be used in conjunction with wall models are discussed, and the equation that connects the slip boundary condition with the stress at the wall is derived. A dynamic procedure based on the invariance of wall stress under test filtering is formulated for the slip condition, providing a dynamic slip wall model free of any a priori specified coefficients. The performance of the proposed dynamic wall model is tested in a series of LES of turbulent channel flow at varying Reynolds numbers, non-equilibrium three-dimensional transient channel flow, and zero-pressure-gradient flat-plate turbulent boundary layer. The results show that the dynamic wall model is able to accurately predict mean and turbulence intensities for various flow configurations, Reynolds numbers, and grid resolutions.
Book Synopsis On the Subgrid-scale Modeling of Compressible Turbulence by : C. G. Speziale
Download or read book On the Subgrid-scale Modeling of Compressible Turbulence written by C. G. Speziale and published by . This book was released on 1987 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mixing of a Passive Scalar in Isotropic and Sheared Homogeneous Turbulence by : Ebrahim Shirani-Chaharsughi
Download or read book Mixing of a Passive Scalar in Isotropic and Sheared Homogeneous Turbulence written by Ebrahim Shirani-Chaharsughi and published by . This book was released on 1981 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Structure and Dynamics of the Vorticity and Passive Scalar Fields at Small Scales in Homogeneous Isotropic Turbulence by : Gregory R. Ruetsch
Download or read book The Structure and Dynamics of the Vorticity and Passive Scalar Fields at Small Scales in Homogeneous Isotropic Turbulence written by Gregory R. Ruetsch and published by . This book was released on 1992 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advanced Turbulent Combustion Physics and Applications by : N. Swaminathan
Download or read book Advanced Turbulent Combustion Physics and Applications written by N. Swaminathan and published by Cambridge University Press. This book was released on 2022-01-06 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore a thorough overview of the current knowledge, developments and outstanding challenges in turbulent combustion and application.
Book Synopsis Large-Eddy Simulations of Turbulence by : M. Lesieur
Download or read book Large-Eddy Simulations of Turbulence written by M. Lesieur and published by Cambridge University Press. This book was released on 2005-08-22 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.
Book Synopsis Numerical Experiments in Homogeneous Turbulence by : Robert Sugden Rogallo
Download or read book Numerical Experiments in Homogeneous Turbulence written by Robert Sugden Rogallo and published by . This book was released on 1981 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Turbulence in the Atmosphere by : John C. Wyngaard
Download or read book Turbulence in the Atmosphere written by John C. Wyngaard and published by Cambridge University Press. This book was released on 2010-01-28 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on his over forty years of research and teaching, John C. Wyngaard's textbook is an excellent up-to-date introduction to turbulence in the atmosphere and in engineering flows for advanced students, and a reference work for researchers in the atmospheric sciences. Part I introduces the concepts and equations of turbulence. It includes a rigorous introduction to the principal types of numerical modeling of turbulent flows. Part II describes turbulence in the atmospheric boundary layer. Part III covers the foundations of the statistical representation of turbulence and includes illustrative examples of stochastic problems that can be solved analytically. The book treats atmospheric and engineering turbulence in a unified way, gives clear explanation of the fundamental concepts of modeling turbulence, and has an up-to-date treatment of turbulence in the atmospheric boundary layer. Student exercises are included at the ends of chapters, and worked solutions are available online for use by course instructors.
Book Synopsis Large Eddy Simulation of Complex Engineering and Geophysical Flows by : Boris Galperin
Download or read book Large Eddy Simulation of Complex Engineering and Geophysical Flows written by Boris Galperin and published by Cambridge University Press. This book was released on 1993-11-26 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: Originally published in 1993, this book was the first to offer a comprehensive review of large eddy simulations (LES) - the history, state of the art, and promising directions for research. Among topics covered are fundamentals of LES; LES of incompressible, compressible, and reacting flows; LES of atmospheric, oceanic, and environmental flows; and LES and massivelt parallel computing. The book grew out of an international workshop that, for the first time, brought together leading researchers in engineering and geophysics to discuss developments and applications of LES models in their respective fields. It will be of value to anyone with an interest in turbulence modelling.
Book Synopsis Turbulent Reactive Flows by : R. Borghi
Download or read book Turbulent Reactive Flows written by R. Borghi and published by Springer Science & Business Media. This book was released on 2013-03-08 with total page 958 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent reactive flows are of common occurrance in combustion engineering, chemical reactor technology and various types of engines producing power and thrust utilizing chemical and nuclear fuels. Pollutant formation and dispersion in the atmospheric environment and in rivers, lakes and ocean also involve interactions between turbulence, chemical reactivity and heat and mass transfer processes. Considerable advances have occurred over the past twenty years in the understanding, analysis, measurement, prediction and control of turbulent reactive flows. Two main contributors to such advances are improvements in instrumentation and spectacular growth in computation: hardware, sciences and skills and data processing software, each leading to developments in others. Turbulence presents several features that are situation-specific. Both for that reason and a number of others, it is yet difficult to visualize a so-called solution of the turbulence problem or even a generalized approach to the problem. It appears that recognition of patterns and structures in turbulent flow and their study based on considerations of stability, interactions, chaos and fractal character may be opening up an avenue of research that may be leading to a generalized approach to classification and analysis and, possibly, prediction of specific processes in the flowfield. Predictions for engineering use, on the other hand, can be foreseen for sometime to come to depend upon modeling of selected features of turbulence at various levels of sophistication dictated by perceived need and available capability.
Book Synopsis Analysis of the K-Epsilon Turbulence Model by : B. Mohammadi
Download or read book Analysis of the K-Epsilon Turbulence Model written by B. Mohammadi and published by . This book was released on 1994-09-06 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aimed at applied mathematicians interested in the numerical simulation of turbulent flows. Centered around the k-&epsis; model, it also deals with other models such as one equation models, subgrid scale models and Reynolds Stress models. Presents the k-&epsis; method for turbulence in a language familiar to applied mathematicians, but has none of the technicalities of turbulence theory.
Download or read book Turbulence written by Peter Davidson and published by Oxford University Press, USA. This book was released on 2015 with total page 647 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an advanced textbook on the subject of turbulence, and is suitable for engineers, physical scientists and applied mathematicians. The aim of the book is to bridge the gap between the elementary accounts of turbulence found in undergraduate texts, and the more rigorous monographs on the subject. Throughout, the book combines the maximum of physical insight with the minimum of mathematical detail. Chapters 1 to 5 may be appropriate as background material for an advanced undergraduate or introductory postgraduate course on turbulence, while chapters 6 to 10 may be suitable as background material for an advanced postgraduate course on turbulence, or act as a reference source for professional researchers. This second edition covers a decade of advancement in the field, streamlining the original content while updating the sections where the subject has moved on. The expanded content includes large-scale dynamics, stratified & rotating turbulence, the increased power of direct numerical simulation, two-dimensional turbulence, Magnetohydrodynamics, and turbulence in the core of the Earth
