A New Rough Wall Layer Modeling For Turbulent Flows Using The Brinkman Equation

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A New Rough Wall Layer Modeling for Turbulent Flows Using the Brinkman Equation

Author : Meng-Huang Lu
Publisher :
ISBN 13 :
Total Pages : 414 pages
Book Rating : 4.:/5 (367 download)

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Book Synopsis A New Rough Wall Layer Modeling for Turbulent Flows Using the Brinkman Equation by : Meng-Huang Lu

Download or read book A New Rough Wall Layer Modeling for Turbulent Flows Using the Brinkman Equation written by Meng-Huang Lu and published by . This book was released on 2008 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new flow physics-based modeling of surface roughness effect is developed for the Reynolds averaged Navier-Stokes equation numerical calculations of high-Reynolds-number turbulent flows over a wide range of rough surfaces. In light of the geometric and the dynamic similarities between the porous medium flow and the surface roughness flow, it is proposed herein to use the Brinkman equation to model the averaged flow in the surface roughness layer of the turbulent boundary layer flow. The averaged model equations for the mean flows are derived and turbulence transport equations are developed based on existing smooth wall turbulence closures. The roughness-related model parameters are also introduced. In the proposed approach, the fluid dynamics of the averaged flow in the near-wall rough layer is modeled by using the Brinkman equation. The porosity can be calculated based on the volumetric characteristics of the roughness and the permeability is modeled. The Reynolds averaged Navier-Stokes equations are solved numerically in the outer free flow region, which is above the near-wall rough layer, while a low-Reynolds-number [kappa-epsilon] model and a second-order Reynolds stress model are employed in all regions. The interface conditions are applied to enforce the continuity of velocity, pressure, and turbulence properties, and the stress jump at the interface between the near-wall rough layer and the free flow region. The computational results, including the skin friction coefficient, the log-law mean velocity, the roughness function, the turbulent kinetic energy, and the Reynolds stresses, are presented. The results show that the new rough wall layer modeling approach predicts well the skin friction coefficient, the log-law mean velocity, the roughness function, and the Reynolds shear stress. The results indicate that the developed rough wall layer modeling approach improves the current predictive capability of the roughness effects, and is applicable to a wider range of surface roughness.

Issues in Computation: 2011 Edition

Author :
Publisher : ScholarlyEditions
ISBN 13 : 146496453X
Total Pages : 1318 pages
Book Rating : 4.4/5 (649 download)

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Book Synopsis Issues in Computation: 2011 Edition by :

Download or read book Issues in Computation: 2011 Edition written by and published by ScholarlyEditions. This book was released on 2012-01-09 with total page 1318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in Computation / 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Computation. The editors have built Issues in Computation: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Computation in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Computation / 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.

Direct Numerical Simulation of Turbulent Mixing in a Rough-Wall Flow

Author : K. Tsujimoto
Publisher :
ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (742 download)

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Book Synopsis Direct Numerical Simulation of Turbulent Mixing in a Rough-Wall Flow by : K. Tsujimoto

Download or read book Direct Numerical Simulation of Turbulent Mixing in a Rough-Wall Flow written by K. Tsujimoto and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rough-wall turbulent flows are more common in engineering application than smooth-wall turbulent flows. Modification of mean flow and turbulence property have been established by enormous experiments. However, details of mechanism of rough-wall turbulence has been understood little because spatial resolution is limited in experiments. Meanwhile, Direct Numerical Simulation (DNS) of a rough-wall turbulent flows which is capable of giving high resolution data requires prohibitively heavy computer power and accordingly, no other DNS data are available than those published by the present authors (Miyake et al., 1999). Our first DNS considered sandgrain roughness whose effect was implemented by profile drag based on Stokes drag and could successfully reproduce experimentally established rough-wall turbulent flow such as downward shift of straight line of logarithmic mean velocity distribution and vanishing of viscous sublayer. It was confirmed that the layer adjacent to the wall up to several tens in wall unit where smooth-wall turbulence exhibits autonomous property independent on the layer above it, is taken over by the layer having property of logarithmic layer, in rough-wall turbulence. While quasi-streamwise vortices play major role to generate high turbulent shear stress in this near-wall layer in smooth-wall turbulent flow, roughness destroy this vortical system and consequently, different mixing system which replaces the role of quasi-streamwise vortices should be found in rough-wall layer. Present work intends to investigate the turbulent mixing in the layer close to the wall of rough-wall turbulence by a DNS of more sound numerical conditions, i.e., without using any model for roughness element.

Fundamentals Of Turbulence Modelling

Author : Ching Jen Chen
Publisher : CRC Press
ISBN 13 : 9781560324058
Total Pages : 312 pages
Book Rating : 4.3/5 (24 download)

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Book Synopsis Fundamentals Of Turbulence Modelling by : Ching Jen Chen

Download or read book Fundamentals Of Turbulence Modelling written by Ching Jen Chen and published by CRC Press. This book was released on 1997-12-01 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Focuses on the second-order turbulence-closure model and its applications to engineering problems. Topics include turbulent motion and the averaging process, near-wall turbulence, applications of turbulence models, and turbulent buoyant flows.

Turbulent Flow and Boundary Layer Theory: Selected Topics and Solved Problems

Author : Jafar Mehdi Hassan
Publisher : Bentham Science Publishers
ISBN 13 : 1681088126
Total Pages : 303 pages
Book Rating : 4.6/5 (81 download)

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Book Synopsis Turbulent Flow and Boundary Layer Theory: Selected Topics and Solved Problems by : Jafar Mehdi Hassan

Download or read book Turbulent Flow and Boundary Layer Theory: Selected Topics and Solved Problems written by Jafar Mehdi Hassan and published by Bentham Science Publishers. This book was released on 2021-08-11 with total page 303 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent Flow and Boundary Layer Theory: Selected Topics and Solved Problems explains fundamental concepts of turbulent flow with boundary layer analysis. A general introduction to turbulent flow familiarizes the reader with the mechanics of turbulence in fluid flow in both nature and engineering applications. The book also explains related concepts including transient flow, methods for controlling transients, turbulent models and dynamic equations for unsteady flow through closed conduits. The contents of the book are designed to help both students and teachers in carrying out turbulent flow analysis and solving problems in engineering and hydraulic applications. Key Features - all the basic concepts in turbulent flow are clearly identiﬁed and presented in a simple manner with illustrative and practical examples. - includes a self-contained approach to the subject, indicating prerequisite materials and information needed from courses. - each chapter also has a set of questions and problems to test the student’s power of comprehending the topics. - provides an exhaustive appendix on interesting examples Turbulent Flow and Boundary Layer Theory: Selected Topics and Solved Problems a useful textbook for students of engineering. It also serves as a quick reference for professionals, researchers and project consultants involved with processes that require turbulent flow and boundary layer methods analysis.

Measurements and Modeling of the Mean and Turbulent Flow Structure in High-Speed Rough-Wall Non-Equilibrium Boundary Layers

Author :
Publisher :
ISBN 13 :
Total Pages : 75 pages
Book Rating : 4.:/5 (61 download)

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Book Synopsis Measurements and Modeling of the Mean and Turbulent Flow Structure in High-Speed Rough-Wall Non-Equilibrium Boundary Layers by :

Download or read book Measurements and Modeling of the Mean and Turbulent Flow Structure in High-Speed Rough-Wall Non-Equilibrium Boundary Layers written by and published by . This book was released on 2010 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: The response of a supersonic high Reynolds number turbulent boundary layer flow subjected to mechanical distortions was experimentally examined. Local disturbances were introduced via small-scale wall patterns, and global distortions were induced through streamline curvature driven pressure gradients. Local surface topologies included k-type diamond and d-type square elements; a smooth wall was examined for comparison purposes. Three global distortions were studied with each of the three surface topologies. Measurements included planar contours of the mean and fluctuating velocity pressure sensitive paint and schlieren photography. The velocity data were acquired with sufficient resolution to characterize the mean and turbulent flow structure and to examine interactions between the local surface roughness distortions and the imposed pressure gradients on the turbulence production. A strong response to both the local and global distortions was observed with the diamond elements, where the effect of the elements extended into the outer-regions of the boundary layer. It was shown that the primary cause for the observed response was the result of local shock and expansion waves modifying the turbulence structure and production. By contrast, the square elements showed a less pronounced response to local flow distortions as the waves were significantly weaker. However, the frictional losses were higher for the blunter square roughness elements. Detailed quantitative characterizations of the turbulence flow structure and the associated production mechanisms are described herein. These experiments demonstrate fundamental differences between supersonic and subsonic rough-wall flows, and the new understanding of the underlying mechanisms provides a scientific basis to systematically modify the mean and turbulence flow structure all the way across supersonic boundary layers.

Analysis of Turbulent Boundary Layers

Author : Tuncer Cebeci
Publisher : Elsevier
ISBN 13 : 0323151051
Total Pages : 423 pages
Book Rating : 4.3/5 (231 download)

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Book Synopsis Analysis of Turbulent Boundary Layers by : Tuncer Cebeci

Download or read book Analysis of Turbulent Boundary Layers written by Tuncer Cebeci and published by Elsevier. This book was released on 2012-12-02 with total page 423 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analysis of Turbulent Boundary Layers focuses on turbulent flows meeting the requirements for the boundary-layer or thin-shear-layer approximations. Its approach is devising relatively fundamental, and often subtle, empirical engineering correlations, which are then introduced into various forms of describing equations for final solution. After introducing the topic on turbulence, the book examines the conservation equations for compressible turbulent flows, boundary-layer equations, and general behavior of turbulent boundary layers. The latter chapters describe the CS method for calculating two-dimensional and axisymmetric laminar and turbulent boundary layers. This book will be useful to readers who have advanced knowledge in fluid mechanics, especially to engineers who study the important problems of design.

Turbulence in Porous Media

Author : Marcelo J.S. de Lemos
Publisher : Elsevier
ISBN 13 : 0080982417
Total Pages : 411 pages
Book Rating : 4.0/5 (89 download)

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Book Synopsis Turbulence in Porous Media by : Marcelo J.S. de Lemos

Download or read book Turbulence in Porous Media written by Marcelo J.S. de Lemos and published by Elsevier. This book was released on 2012-06-25 with total page 411 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence in Porous Media introduces the reader to the characterisation of turbulent flow, heat and mass transfer in permeable media, including analytical data and a review of available experimental data. Such transport processes occurring a relatively high velocity in permeable media are present in a number of engineering and natural flows. This new edition features a completely updated text including two new chapters exploring Turbulent Combustion and Moving Porous Media. De Lemos has expertly brought together a text that compiles, details, compares and evaluates available methodologies for modelling and simulating flow, providing an essential tour for engineering students working within the field as well as those working in chemistry, physics, applied mathematics, and geological and environmental sciences. Brings together groundbreaking and complex research on turbulence in porous media Extends the original model to situations including reactive systems Now discusses movement of the porous matrix

The Thermal and Hydrodynamic Behavior of Thick, Rough-wall, Turbulent Boundary Layers

Author : P. M. Ligrani
Publisher :
ISBN 13 :
Total Pages : 272 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis The Thermal and Hydrodynamic Behavior of Thick, Rough-wall, Turbulent Boundary Layers by : P. M. Ligrani

Download or read book The Thermal and Hydrodynamic Behavior of Thick, Rough-wall, Turbulent Boundary Layers written by P. M. Ligrani and published by . This book was released on 1979 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thick, fully rough, and transitionally rough turbulent boundary layers were studied in order to investigate the differences between fully rough and transitionally rough behavior and to observe how downstream development affects these flows as the boundary layers become very thick. Measurements included Stanton numbers, skin friction coefficients, mean temperature and velocity profiles, Reynolds stress tensor component profiles, and spectra of the longitudinal velocity fluctuations. Predictions of wall heat transfer, wall shear, and mean profiles were made using a mixing-length and turbulent Prandtl number closure scheme which accounted for the effects of wall roughness in the boundary layer equations. The turbulent layers were artificially thickened using an array of solid obstacles which produced a two-dimensional equilibrium flow field with properties representative of natural bounday layers, at least up to the level of the turbulent correlations on a smooth wall, and to the level of the spectra of longitudinal velocity fluctuations on a rough wall. A rough-wall boundary layer environment was provided in which all measurements of lower order than the turbulence correlations could be discussed regarding the influence of roughness, and considered to have properties representative of natural behavior. (Author).

Applied Mechanics Reviews

Author :
Publisher :
ISBN 13 :
Total Pages : 384 pages
Book Rating : 4.3/5 (243 download)

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Book Synopsis Applied Mechanics Reviews by :

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1988 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Numerical Simulations of Rough-wall Turbulent Boundary Layers

Author :
Publisher :
ISBN 13 :
Total Pages : 302 pages
Book Rating : 4.:/5 (919 download)

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Book Synopsis Numerical Simulations of Rough-wall Turbulent Boundary Layers by :

Download or read book Numerical Simulations of Rough-wall Turbulent Boundary Layers written by and published by . This book was released on 2015 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: At sufficiently high Reynolds number, all surfaces are rough, and roughness affects most flows in engineering and the natural sciences. Examples range from atmospheric boundary layers over buildings and canopies, to engineering surfaces with erosion, deposits, etc. To study the roughness effects, we take a high-resolution approach to capture the flow around individual roughness elements using direct and large-eddy simulations (DNS and LES); the goal is to elucidate phenomena which have been difficult to access using physical experiments, and to help develop engineering correlations and models. First, most experiments and turbulence models are based on a standardized type of roughness, sand-grain roughness, which can be described using a single length scale. The relationship between the geometry of an arbitrary surface and the canonical one must be known, to predict critical flow parameters such as the drag, using either experimental correlations or turbulence models. Using numerical experiments, we relate this length-scale to the roughness geometry, and propose a guideline for its prediction in the industrial setting. Next, to explain the dependence of drag on the topographical details, we examine the role of the wake of the roughness elements in the drag generation of a rough surface. The wake field is found to promote vertical momentum transfer and near-wall instability; it might provide a link between geometry details and the engineering modeling of roughness effects. Lastly, we focus on a more realistic flow scenario -- the one with freestream accelerations -- and study the combined effects of roughness and acceleration, a phenomenon widely present in engineering flows over airfoils or complex landscapes. It is first shown, by comparing equilibrium accelerating flows obtained in the present study with the non-equilibrium flows in the literature, that the roughness and acceleration effects are interdependent and depend on the flow equilibrity. Then, using DNS data of a spatially developing flat-plate boundary layer, it is found that the effect coupling develops as the roughness affects the turbulence time scale and thus the flow susceptibility of the acceleration stabilization, while acceleration changes the wake velocity and ultimately the roughness destabilization level.

Pdf Modeling of Near-wall Turbulent Flows

Author : Thomas David Dreeben
Publisher :
ISBN 13 :
Total Pages : 294 pages
Book Rating : 4.E/5 ( download)

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Book Synopsis Pdf Modeling of Near-wall Turbulent Flows by : Thomas David Dreeben

Download or read book Pdf Modeling of Near-wall Turbulent Flows written by Thomas David Dreeben and published by . This book was released on 1997 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:

A Near-wall Two-equation Model for Compressible Turbulent Flows

Author : Institute for Computer Applications in Science and Engineering
Publisher :
ISBN 13 :
Total Pages : 44 pages
Book Rating : 4.:/5 (317 download)

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Book Synopsis A Near-wall Two-equation Model for Compressible Turbulent Flows by : Institute for Computer Applications in Science and Engineering

Download or read book A Near-wall Two-equation Model for Compressible Turbulent Flows written by Institute for Computer Applications in Science and Engineering and published by . This book was released on 1991 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Studies of Real Roughness Effects for Improved Modeling and Control of Practical Wall-Bounded Turbulent Flows

Author :
Publisher :
ISBN 13 :
Total Pages : 183 pages
Book Rating : 4.:/5 (318 download)

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Book Synopsis Studies of Real Roughness Effects for Improved Modeling and Control of Practical Wall-Bounded Turbulent Flows by :

Download or read book Studies of Real Roughness Effects for Improved Modeling and Control of Practical Wall-Bounded Turbulent Flows written by and published by . This book was released on 2008 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present effort investigates the effects of practical roughness replicated from a turbine blade damaged by deposition of foreign materials or statistical and structural characteristics of wall turbulence. Two-dimensional particle image velocimetry (PIV) measurements are performed in the streamwise-wall-normal plane of turbulent boundary layers at momentum Reynolds numbers of 8000 and 13000. The surface conditions include a smooth wall and two highly-irregular rough walls. These rough surfaces have the same roughness topography but differ in spatial scaling. The validity of Townsend's wall similarity hypothesis in the presence of practical roughness is assessed and the impact of this roughness on the spatial structure of the flow is investigated. In addition, stereoscopic PIV measurements are made in streamwise-spanwise planes of smooth- and rough-wall turbulent boundary layers both within and at the outer edge of the roughness sublayer. This data is used to explore the impact of dominant topographical features on the near-wall flow as well as the influence of practical roughness on the spatial organization of the flow. Understanding such effects provides a steppingstone toward efficient modeling and control of practical flows in the presence of roughness.

On the Generation of Wall Pressure Fluctuations for Turbulent Boundary Layers Over Rough Walls

Author : Thomas E. Burton
Publisher :
ISBN 13 :
Total Pages : 63 pages
Book Rating : 4.:/5 (18 download)

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Book Synopsis On the Generation of Wall Pressure Fluctuations for Turbulent Boundary Layers Over Rough Walls by : Thomas E. Burton

Download or read book On the Generation of Wall Pressure Fluctuations for Turbulent Boundary Layers Over Rough Walls written by Thomas E. Burton and published by . This book was released on 1971 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of pressure-velocity correlation in turbulent flow was extended to turbulent boundary layer flow over a roughened wall in the absence of a longitudinal pressure gradient. The results obtained are qualitatively similar to those previously measured over smooth walls. A theory is presented to partially explain the behavior of the measured correlations in both the smooth-wall and rough-wall cases.

Open Channel Turbulent Boundary Layers and Wall Jets on Rough Surfaces

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (654 download)

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Book Synopsis Open Channel Turbulent Boundary Layers and Wall Jets on Rough Surfaces by :

Download or read book Open Channel Turbulent Boundary Layers and Wall Jets on Rough Surfaces written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For many industrial and environmental flows, the momentum and convective heat transfer rates at the surface are determined by the turbulence structure in the near-wall region. Although many flows of practical interest occur on rough surfaces, our understanding and ability to predict rough wall turbulent flows lags far behind the corresponding technology for smooth surfaces. This provides reasonable grounds for additional refined rough wall measurements with the expectation of improving our physical understanding of practically relevant turbulent flows. This thesis reports an experimental investigation of wall roughness effects on the characteristics of turbulent boundary layers and wall jets. The measurements are obtained for smooth wall and three different roughness elements using a laser-Doppler anemometer. An insightful presentation of the results requires that the correct scaling laws must be used. In the case of the turbulent boundary layer, the appropriateness of the log law proposed by Millikan (1938) to model the overlap region of the mean flow and the power laws proposed by Barenblatt (1993) and George and Castillo (1997) is compared. The boundary layer results show that the theory proposed by George and Castillo (1997) has important advantages over the log law in modeling the mean velocity profiles as well as predicting the wall shear stress. The results also show that wall roughness increases the turbulence fluctuations and transport terms, which suggests that rough wall turbulence models must explicitly account for roughness effects in order to predict the mixing characteristics accurately. This promises to provide significant challenges to rough wall turbulence models. The wall jet results show that wall roughness increases the inner layer thickness but the jet half-width does not show any important sensitivity to surface roughness. The spread rates for the jet half-width are higher than the values obtained in earlier measurements. This may be attribute.

An Experimental Study of Turbulent Boundary Layer on Rough Walls

Author : C. K. Liu
Publisher :
ISBN 13 :
Total Pages : 171 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis An Experimental Study of Turbulent Boundary Layer on Rough Walls by : C. K. Liu

Download or read book An Experimental Study of Turbulent Boundary Layer on Rough Walls written by C. K. Liu and published by . This book was released on 1966 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental data are presented on flow structure, mean, and fluctuating velocities in turbulent boundary layers over a family of flat surfaces with transverse roughness elements made of square bars of variable spacing. All flows were incompressible and had zero streamwise pressure gradient. The flow structures are described for surfaces extending from hydraulically smooth to fully rough. A distinct flow pattern is observed in the wall region for each of four cases: smooth, skimming, wake-interference and isolated-roughness flow. Maximum roughness was observed with a ratio of gap to bar width of approximately 11. The most obvious effect of an increase in surface roughness is the distinct increase of turbulence production and the concomittant increase in the value of eddy viscosity. It is shown that this increase in eddy viscosity increases the total thickness of the layer in the same way that an increase in molecular viscosity would do in a laminar layer. The normalization of eddy viscosity for the outer portion of the layer as suggested by Clauser is found to apply to the rough surfaces studied. (Author).