Wall Modeling For Turbulent Flow Over Complex Roughness

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Wall Modeling for Turbulent Flow Over Complex Roughness

Author : Xiaowei Zhu (Mechanical engineer)
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (19 download)

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Book Synopsis Wall Modeling for Turbulent Flow Over Complex Roughness by : Xiaowei Zhu (Mechanical engineer)

Download or read book Wall Modeling for Turbulent Flow Over Complex Roughness written by Xiaowei Zhu (Mechanical engineer) and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent flow over complex rough surfaces is crucial in both engineering and boundary layer meteorology science. The surface morphology has significant effects on the flow, but it is computationally expensive to solve all the turbulent scales especially when the air flows over complex roughness. Large-eddy simulation (LES) with wall model is therefore employed in this situation. This dissertation focuses on the wall modeling of turbulent flow over complex roughness such as urban topography. As the wall effects can be accurately represented by the equilibrium logarithmic law via roughness length, z0, this dissertation aims to parameterize z0 over complex roughness. In this dissertation, two types of complex roughness are discussed: spatially heterogenous urban-like topography (Chapter 3) and multiscale fractal urban-like topography (Chapter 4). For the spatially heterogeneous urban-like topography, a priori prediction method for z0 based on the statistical moments of surface height is proposed especially for the boundarylayer turbulent flow. Using a posteriori LES results, we demonstrate that the skewness of surface height (as measures of the presence of the extreme value, or the “heavy tail” events) has non-negligible effects, which received less attention as topographic parameters in the past. This finding is reconciled with a model recently proposed by Flack and Schultz (2010) who demonstrate that z0 can be modeled with standard deviation and skewness, and two empirical coefficients (one for each moment). We find that the empirical coefficient related to skewness is not constant but exhibits a dependence on standard deviation over certain ranges. For idealized, quasi-uniform cubic topographies and complex, fully random urbanlike topographies, we demonstrate robust performance of the generalized Flack and Schultz model against contemporary roughness correlations. The multiscale fractal-like topographies pose a particular challenge to numerical simulation schemes since the large-scale elements are resolved, but the small-scale descendant elements cannot be resolved on the computational mesh grid. A local wall model representing the effects of unresolved sub-generation roughness is needed in such scenario. By virtue of selfsimilarity among scales, we develop a methodology and a roughness model for the unresolved scales by learning from the large-scale momentum fluxes. And then the roughness model for the unresolved scales via the equilibrium logarithmic law is established. The research shows that aerodynamic stress associated with descendant, sub-generation scale elements can be parameterized, thus that the turbulent flow over fractal-like geometry can be simulated with only the large generations resolved on the computational mesh grid. The key questions we ask in this dissertation are: How does the spatial heterogeneity affect the transport of the turbulent flow? How to model the sub-generation scales which are smaller than the mesh grid for a fractal topography? The results, and the modeling framework developed herein, have practical implications for the operation of numerical weather prediction models and the initialization of high-resolution solutions.

Simulation and Modeling of Compressible and Incompressible Turbulent Channel Flows Over Rough Walls

Author : Mostafa Aghaei Jouybari
Publisher :
ISBN 13 :
Total Pages : 144 pages
Book Rating : 4.5/5 (57 download)

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Book Synopsis Simulation and Modeling of Compressible and Incompressible Turbulent Channel Flows Over Rough Walls by : Mostafa Aghaei Jouybari

Download or read book Simulation and Modeling of Compressible and Incompressible Turbulent Channel Flows Over Rough Walls written by Mostafa Aghaei Jouybari and published by . This book was released on 2020 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of surface roughness on wall-bounded turbulent flows are important for fundamental turbulence research, and turbulence modeling and control, in both compressible and incompressible regimes. This dissertation studies these effects through statistical and structural analysis of turbulence, and provides practical insights for modeling of turbulence in the presence of roughness for incompressible flows. It also proposes an immersed boundary method to simulate compressible flows over rough walls with complex geometries, and studies the roughness effects on supersonic flows over wavy walls. Turbulence statistics in open channel flows over a smooth wall and three types of wall roughness: sand-grain, cube roughness and a realistic, multi-scale turbine-blade roughness, are examined using direct numerical simulations. Transport of the mean momentum, normal components of the Reynolds stress tensor, and normal components of the dispersive stress tensor are analyzed. The results show higher turbulence isotropy for the rough walls compared to the smooth wall. Wake production, the mechanism through which energy is transported from the wake field to the turbulence field (and vice versa), is strongly influenced by the kind of rough wall. For synthetic rough walls, the wake production has relatively large positive values, while it is negative with a smaller magnitude, for the turbine-blade surface. These results indicate a strong dependence of turbulence processes in the near wall regions on the roughness topography. Turbulent coherent motions in flows over rough walls are also analyzed. Two-point velocity correlations, length scales, inclination angles, and velocity spectra are studied. Results from linear stochastic estimation suggest that, near the wall, the quasi-streamwise vortices observed in smoothwall flow are present in the large-scale recessed regions of multi-scale roughness, whereas they are replaced by a pair of 'head-up, head-down' horseshoe structures in the sandgrain and cube roughnesses, similar to those observed in the previous studies. The configuration of conditional eddies near the wall suggests that the kinematic behavior of vortices differs for each kind of rough surfaces. Vortices over multiscale roughness are conjectured to obey a growth mechanism similar to those over smooth walls, while around the cube roughness the head-down horse-shoe vortices undergo a solid-body rotation on top of the element on account of the strong shear layer. This shortens the longitudinal extent of the near-wall structures and promotes turbulence production. Deep Neural Networks (DNN) and Gaussian Process Regression (GPR) are used to propose a high-fidelity prediction of the Nikuradse equivalent sandgrain height, (ks), which is frequently used in turbulence modeling of flows over rough walls. To provide a good database, 45 widely different surface geometries are generated and simulated at frictional Reynolds number of 1000, which are also accompanied by 15 fully rough experimental data. The designed DNN and GPR models predict ks with errrms

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.

Turbulent Flows

Author : Jean Piquet
Publisher : Springer Science & Business Media
ISBN 13 : 3662035596
Total Pages : 767 pages
Book Rating : 4.6/5 (62 download)

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Book Synopsis Turbulent Flows by : Jean Piquet

Download or read book Turbulent Flows written by Jean Piquet and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 767 pages. Available in PDF, EPUB and Kindle. Book excerpt: obtained are still severely limited to low Reynolds numbers (about only one decade better than direct numerical simulations), and the interpretation of such calculations for complex, curved geometries is still unclear. It is evident that a lot of work (and a very significant increase in available computing power) is required before such methods can be adopted in daily's engineering practice. I hope to l"Cport on all these topics in a near future. The book is divided into six chapters, each· chapter in subchapters, sections and subsections. The first part is introduced by Chapter 1 which summarizes the equations of fluid mechanies, it is developed in C~apters 2 to 4 devoted to the construction of turbulence models. What has been called "engineering methods" is considered in Chapter 2 where the Reynolds averaged equations al"C established and the closure problem studied (§1-3). A first detailed study of homogeneous turbulent flows follows (§4). It includes a review of available experimental data and their modeling. The eddy viscosity concept is analyzed in §5 with the l"Csulting ~alar-transport equation models such as the famous K-e model. Reynolds stl"Css models (Chapter 4) require a preliminary consideration of two-point turbulence concepts which are developed in Chapter 3 devoted to homogeneous turbulence. We review the two-point moments of velocity fields and their spectral transforms (§ 1), their general dynamics (§2) with the particular case of homogeneous, isotropie turbulence (§3) whel"C the so-called Kolmogorov's assumptions are discussed at length.

The Structure of Turbulent Shear Flow

Author : A. A. R. Townsend
Publisher : Cambridge University Press
ISBN 13 : 9780521298193
Total Pages : 450 pages
Book Rating : 4.2/5 (981 download)

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Book Synopsis The Structure of Turbulent Shear Flow by : A. A. R. Townsend

Download or read book The Structure of Turbulent Shear Flow written by A. A. R. Townsend and published by Cambridge University Press. This book was released on 1976 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: Develops a physical theory from the mass of experimental results, with revisions to reflect advances of recent years.

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.

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.

Experimental Investigation of the Problem of Surface Roughness

Author : H. Schlichting
Publisher :
ISBN 13 :
Total Pages : 604 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis Experimental Investigation of the Problem of Surface Roughness by : H. Schlichting

Download or read book Experimental Investigation of the Problem of Surface Roughness written by H. Schlichting and published by . This book was released on 1937 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on the universal laws of turbulent velocity distribution at rough and smooth walls, there is in the present work presented a method that allows surface roughness tests and in particular, measurements on the roughness of ship surfaces to be carried out in a much simpler manner. The types of roughness investigated were in the form of flat, rough plates installed in a square-section rectangular channel, the other three walls always being smooth. Twenty-one plates of various roughness were investigated, the roughness elements being the following: spheres of diameter 0.41 and 0.21, respectively, spherical segments, cones, and "short" and "long" angles.

Boundary-Layer Theory

Author : Hermann Schlichting (Deceased)
Publisher : Springer
ISBN 13 : 366252919X
Total Pages : 814 pages
Book Rating : 4.6/5 (625 download)

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Book Synopsis Boundary-Layer Theory by : Hermann Schlichting (Deceased)

Download or read book Boundary-Layer Theory written by Hermann Schlichting (Deceased) and published by Springer. This book was released on 2016-10-04 with total page 814 pages. Available in PDF, EPUB and Kindle. Book excerpt: This new edition of the near-legendary textbook by Schlichting and revised by Gersten presents a comprehensive overview of boundary-layer theory and its application to all areas of fluid mechanics, with particular emphasis on the flow past bodies (e.g. aircraft aerodynamics). The new edition features an updated reference list and over 100 additional changes throughout the book, reflecting the latest advances on the subject.

Advanced Approaches in Turbulence

Author : Paul Durbin
Publisher : Elsevier
ISBN 13 : 0128207744
Total Pages : 552 pages
Book Rating : 4.1/5 (282 download)

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Book Synopsis Advanced Approaches in Turbulence by : Paul Durbin

Download or read book Advanced Approaches in Turbulence written by Paul Durbin and published by Elsevier. This book was released on 2021-07-30 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Front Cover -- Advanced Approaches in Turbulence -- Copyright -- Contents -- Contributors -- Preface -- 1 Basics of turbulence -- 1.1 Introduction -- 1.2 Eddy diffusion -- 1.3 Scales of turbulence -- 1.3.1 Isotropic decay -- 1.3.2 Stretching and diffusion of vorticity -- 1.4 Spectral equations -- 1.4.1 Isotropic turbulence -- 1.4.2 Shear and streaks -- 1.5 Averaged equations -- 1.5.1 Jets -- 1.5.2 Boundary layer -- 1.6 The form of turbulence models -- 1.6.1 Two equation models -- 1.6.2 Reynolds stress transport -- 1.7 Conclusion -- References -- 2 Direct numerical and large-eddy simulation of complex turbulent flows -- 2.1 Introduction -- 2.2 Error as a function of scale -- 2.2.1 Modified wavenumber -- 2.2.2 Nonlinear sources of error -- 2.2.3 Time advancement error as a function of scale -- 2.3 Analysis of numerical errors in large-eddy simulation using statistical closure theory -- 2.3.1 EDQNM closure -- 2.3.2 EDQNM-LES and the inclusion of numerical error -- 2.3.3 EDQNM model -- 2.3.4 Relative magnitudes of error -- 2.4 Simulations in complex geometries -- 2.4.1 Decay of isotropic turbulence -- 2.4.2 Gas turbine combustor -- 2.5 Simulating the flow around moving bodies -- 2.5.1 Fluid phase -- 2.5.2 Solid phase -- 2.5.3 The effects of interpolation -- 2.5.4 Particles in a turbulent channel -- 2.6 What is a 'canonical' flow? -- 2.6.1 Jets in crossflow -- 2.6.2 DNS of turbulent channel flow over random rough surfaces -- 2.7 The analysis of 'big data' -- 2.7.1 DMD of large datasets and numerical error -- 2.7.2 Analysis of wall-pressure fluctuation sources in turbulent channel flow -- 2.8 Bridging the Reynolds number divide -- 2.9 Concluding remarks -- Acknowledgments -- References -- 3 Large-eddy simulations -- 3.1 Introduction -- 3.1.1 Motivation -- 3.2 Governing equations -- 3.2.1 Filtering.

Large-eddy Simulations of Fully Developed Turbulent Channel and Pipe Flows with Smooth and Rough Walls

Author : Namiko Saito
Publisher :
ISBN 13 :
Total Pages : 218 pages
Book Rating : 4.:/5 (874 download)

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Book Synopsis Large-eddy Simulations of Fully Developed Turbulent Channel and Pipe Flows with Smooth and Rough Walls by : Namiko Saito

Download or read book Large-eddy Simulations of Fully Developed Turbulent Channel and Pipe Flows with Smooth and Rough Walls written by Namiko Saito and published by . This book was released on 2014 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies in turbulence often focus on two flow conditions, both of which occur frequently in real-world flows and are sought-after for their value in advancing turbulence theory. These are the high Reynolds number regime and the effect of wall surface roughness. In this dissertation, a Large-Eddy Simulation (LES) recreates both conditions over a wide range of Reynolds numbers ReT = O(102)-O(108) and accounts for roughness by locally modeling the statistical effects of near-wall anisotropic fine scales in a thin layer immediately above the rough surface. A subgrid, roughness-corrected wall model is introduced to dynamically transmit this modeled information from the wall to the outer LES, which uses a stretched-vortex subgrid-scale model operating in the bulk of the flow. Of primary interest is the Reynolds number and roughness dependence of these flows in terms of first and second order statistics. The LES is first applied to a fully turbulent uniformly-smooth/rough channel flow to capture the flow dynamics over smooth, transitionally rough and fully rough regimes. Results include a Moody-like diagram for the wall averaged friction factor, believed to be the first of its kind obtained from LES. Confirmation is found for experimentally observed logarithmic behavior in the normalized stream-wise turbulent intensities. Tight logarithmic collapse, scaled on the wall friction velocity, is found for smooth-wall flows when ReT ≥ O(106) and in fully rough cases. Since the wall model operates locally and dynamically, the framework is used to investigate non-uniform roughness distribution cases in a channel, where the flow adjustments to sudden surface changes are investigated. Recovery of mean quantities and turbulent statistics after transitions are discussed qualitatively and quantitatively at various roughness and Reynolds number levels. The internal boundary layer, which is defined as the border between the flow affected by the new surface condition and the unaffected part, is computed, and a collapse of the profiles on a length scale containing the logarithm of friction Reynolds number is presented. Finally, we turn to the possibility of expanding the present framework to accommodate more general geometries. As a first step, the whole LES framework is modified for use in the curvilinear geometry of a fully-developed turbulent pipe flow, with implementation carried out in a spectral element solver capable of handling complex wall profiles. The friction factors have shown favorable agreement with the superpipe data, and the LES estimates of the Karman constant and additive constant of the log-law closely match values obtained from experiment.

YIP-Low-Order Representations of Irregular Surface Roughness and Their Impact on Wall Turbulence

Author :
Publisher :
ISBN 13 :
Total Pages : 44 pages
Book Rating : 4.:/5 (713 download)

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Book Synopsis YIP-Low-Order Representations of Irregular Surface Roughness and Their Impact on Wall Turbulence by :

Download or read book YIP-Low-Order Representations of Irregular Surface Roughness and Their Impact on Wall Turbulence written by and published by . This book was released on 2010 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: This effort explored the impact of topographical scales present within irregular surface roughness on a turbulent boundary layer. Low-order representations of a surface replicated from a turbine blade damaged by deposition of foreign materials were generated using singular value decomposition to decompose the complex topography into a set of basis functions of decreasing importance to the original ("full") surface. The low-order surface models were then formed by truncating the basis functions at the first 5 and 16 modes (containing 71 % and 95% of the full surface content, respectively), so that only the largest-scale topographical features were included. Physical replications of these surfaces were rapid prototyped and particle-image velocimetry was used to measure the flow over these surfaces in the streamwise-wall-normal plane and in a streamwise-spanwise plane deep within the roughness sublayer. A 16-mode model of the full surface faithfully reproduced most of the characteristics of flow over the full surface for both developing and developed flow conditions. However, both models failed to reproduce important details of the Reynolds-shear-stress-producing events within the roughness sublayer. The final report details these observations.

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.

Mathematics of Large Eddy Simulation of Turbulent Flows

Author : Luigi Carlo Berselli
Publisher : Springer Science & Business Media
ISBN 13 : 9783540263166
Total Pages : 378 pages
Book Rating : 4.2/5 (631 download)

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Book Synopsis Mathematics of Large Eddy Simulation of Turbulent Flows by : Luigi Carlo Berselli

Download or read book Mathematics of Large Eddy Simulation of Turbulent Flows written by Luigi Carlo Berselli and published by Springer Science & Business Media. This book was released on 2006 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: The LES-method is rapidly developing in many practical applications in engineering The mathematical background is presented here for the first time in book form by one of the leaders in the field

Direct Numerical Simulations (DNS) of Turbulent Flows in an Undulating Channel

Author : Luo Wang
Publisher :
ISBN 13 :
Total Pages : 300 pages
Book Rating : 4.:/5 (32 download)

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Book Synopsis Direct Numerical Simulations (DNS) of Turbulent Flows in an Undulating Channel by : Luo Wang

Download or read book Direct Numerical Simulations (DNS) of Turbulent Flows in an Undulating Channel written by Luo Wang and published by . This book was released on 2007 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: In summary, in this work we have developed and successfully tested all the necessary ingredients for a successful simulation of viscoelastic turbulent flow in a wavy channel. It is only a matter of time in future work to address the fine tuning of parameters such as the diffusivity, time integration scheme, etc. in order to successfully perform the very large scale simulations needed to reproduce viscoelastic turbulent flows in a wavy channel flow geometry.

Fluid Flow Phenomena

Author : Paolo Orlandi
Publisher : Springer Science & Business Media
ISBN 13 : 9401142815
Total Pages : 369 pages
Book Rating : 4.4/5 (11 download)

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Book Synopsis Fluid Flow Phenomena by : Paolo Orlandi

Download or read book Fluid Flow Phenomena written by Paolo Orlandi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with the simulation of the incompressible Navier-Stokes equations for laminar and turbulent flows. The book is limited to explaining and employing the finite difference method. It furnishes a large number of source codes which permit to play with the Navier-Stokes equations and to understand the complex physics related to fluid mechanics. Numerical simulations are useful tools to understand the complexity of the flows, which often is difficult to derive from laboratory experiments. This book, then, can be very useful to scholars doing laboratory experiments, since they often do not have extra time to study the large variety of numerical methods; furthermore they cannot spend more time in transferring one of the methods into a computer language. By means of numerical simulations, for example, insights into the vorticity field can be obtained which are difficult to obtain by measurements. This book can be used by graduate as well as undergraduate students while reading books on theoretical fluid mechanics; it teaches how to simulate the dynamics of flow fields on personal computers. This will provide a better way of understanding the theory. Two chapters on Large Eddy Simulations have been included, since this is a methodology that in the near future will allow more universal turbulence models for practical applications. The direct simulation of the Navier-Stokes equations (DNS) is simple by finite-differences, that are satisfactory to reproduce the dynamics of turbulent flows. A large part of the book is devoted to the study of homogeneous and wall turbulent flows. In the second chapter the elementary concept of finite difference is given to solve parabolic and elliptical partial differential equations. In successive chapters the 1D, 2D, and 3D Navier-Stokes equations are solved in Cartesian and cylindrical coordinates. Finally, Large Eddy Simulations are performed to check the importance of the subgrid scale models. Results for turbulent and laminar flows are discussed, with particular emphasis on vortex dynamics. This volume will be of interest to graduate students and researchers wanting to compare experiments and numerical simulations, and to workers in the mechanical and aeronautic industries.

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.