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Study Of Turbulent Boundary Layers Over Rough Surfaces With Emphasis On The Effects Of Roughness Character And Mach Number
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Book Synopsis Study of Turbulent Boundary Layers Over Rough Surfaces, with Emphasis on the Effects of Roughness Character and Mach Number by : M. L. Finson
Download or read book Study of Turbulent Boundary Layers Over Rough Surfaces, with Emphasis on the Effects of Roughness Character and Mach Number written by M. L. Finson and published by . This book was released on 1982 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Study of Turbulent Boundary Layers Over Rough Surfaces, with Emphasis on the Effects of Roughness Character and Mach Number by : M. L. Finson
Download or read book Study of Turbulent Boundary Layers Over Rough Surfaces, with Emphasis on the Effects of Roughness Character and Mach Number written by M. L. Finson and published by . This book was released on 1982 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Reynolds stress model for turbulent boundary layers on rough walls is used to investigate the effects of roughness character and compressibility. The flow around roughness elements is treated as form drag. A method is presented for deriving the required roughness shape and spacing from profilometer surface measurements. Calculations based on the model compare satisfactorily with low speed data on roughness character and hypersonic measurements with grit roughness. The computer model is exercised systematically over a wide range of parameters to derive a practical scaling law for the equivalent roughness. In contrast to previous correlations, for most roughness element shapes the effective roughness is not predicted to show a pronounced maximum as the element spacing decreases. The effect of roughness tends to be reduced with increasing edge mach number, primarily due to decreasing density in the vicinity of the roughness elements. It is further shown that the required roughness Reynolds number for fully rough behavior increases with increasing Mach number, explaining the small roughness effects observed in some hypersonic tests. (Author).
Book Synopsis Mixing-length Formulations for Turbulent Boundary Layers Over Arbitrarily Rough Surfaces by : Paul S. Granville
Download or read book Mixing-length Formulations for Turbulent Boundary Layers Over Arbitrarily Rough Surfaces written by Paul S. Granville and published by . This book was released on 1984 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Influence of Surface Roughness on Supersonic High Reynolds Number Turbulent Boundary Layer Flow by : Robert M. Latin
Download or read book The Influence of Surface Roughness on Supersonic High Reynolds Number Turbulent Boundary Layer Flow written by Robert M. Latin and published by . This book was released on 1998-03-01 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive study of rough-wall high speed (M=2.9) high Reynolds number (Re/m = 1.9. 10 to the 7th power) turbulent boundary layer flow was performed consisting of experimental, analytical, and numerical methods. Six wall topologies consisting of a smooth and five rough surfaces (two and three dimensional machined roughness plates; and 80, 36, and 20 grit sand-grain roughened plates) were studied. A confocal laser scan microscope was used to measure the topography of the sand grain roughnesses. The experimental measurement techniques included a convention Pitot pressure probe, laser Doppler velocimetry, hot wire anemometry; color schlieren and laser sheet Mie scattering images. Mean measurements included velocity, Mach number, density, and mass flux. Turbulent measurements included velocity and mass flux turbulence intensities, kinematic Reynolds shear stress, compressible Reynolds shear stress in two planes, and the traverse apparent mass flux. Kinematic turbulent flow statistical properties were found to scale by local mean quantities and displayed a weak dependence on surface roughness. Turbulent flow statistical properties with the explicit appearance of density did not scale by local mean quantities, and had a strong linear dependence on roughness. Surface roughness also had a significant effect on the flow structure size, angles, and energy spectra. A theoretical analysis was performed and a new integral method for the estimation of skin friction was developed. The skin friction estimates were within 4% of compressible semi-empirical relations. A numerical study was performed which used a parabolized Navier Stokes solver with two algebraic turbulence models and the Rotta model for surface roughness. A new method for the estimation of momentum loss improved the numerical flow predictability.
Book Synopsis Compressible Turbulent Skin Friction on Rough and Rough/wavy Walls in Adiabatic Flow by : Daniel C. Reda
Download or read book Compressible Turbulent Skin Friction on Rough and Rough/wavy Walls in Adiabatic Flow written by Daniel C. Reda and published by . This book was released on 1974 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental program was conducted to investigate effects of roughness, and roughness superimposed on single and/or multiple, shallow, periodic waveforms, on turbulent boundary-layer skin friction and velocity profile, in compressible, adiabatic flow. Test conditions were Mach number = 2.9 and Reynolds number/ft = 2 million to 8 million. The planar models included smooth, sand-grain, machined and molded surface finishes. Direct measurements of surface shear and Pitot/recovery temperature profiles were obtained. (Modified author abstract).
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1989 with total page 816 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
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.
Book Synopsis An Analytical Study of the Effects of Surface Roughness on a Compressible Turbulent Boundary Layer by :
Download or read book An Analytical Study of the Effects of Surface Roughness on a Compressible Turbulent Boundary Layer written by and published by . This book was released on 1983 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: A previous study on the effect of surface roughness on the turbulent boundary layer, using a Fortran code, ITRACT, solved for the characteristics of a laminar, transitional and turbulent boundary layer on smooth surfaces. The present study investigates the influence of surface roughness on a compressible turbulent boundary layer and then extends the usefulness of ITRACT by including in it the optional capability of rough-surface boundary-layer calculations. Surface roughness was represented by distributed sources and sinks in the appropriate governing equations. The most important term is a sink term in the mean momentum equation, representing the form drag due to the roughness element. Governing boundary-layer equations for continuity, momentum, and energy were derived in a form to account for blockage effects due to roughness elements. The modified governing equations were then transformed using Probstein-Elliott and Levy-Lees transformations. The resulting equations, with appropriate boundary conditions, were solved by finite-difference techniques to determine the nondimensional velocity components and temperature at a finite number of nodes in the boundary-layer flow field.
Download or read book Proceedings written by Jack E. Cermak and published by . This book was released on 1975 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Book Synopsis The Effects of Roughness on Turbulent Boundary Layers by : Fanxiao Meng
Download or read book The Effects of Roughness on Turbulent Boundary Layers written by Fanxiao Meng and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the effects of roughness on turbulent boundary layers are investigated by both the experimental and analytical methods. Two aspects of roughness are investigated, including the similarity between the smooth and rough turbulent boundary layers, and the characteristics of the flow over the step changes in roughness. Based on the data from the thesis of Akinlade (2005), the validity of three different kinds of outer scales is examined for the defect law in the context of smooth surface and three different types of rough surfaces. Furthermore, a mathematical relation is derived to further investigate the roughness effects. For the second topic, experiments were performed on a smooth-rough-smooth transition in a wind tunnel using a boundary layer Pitot tube. In addition, the growth rates of internal boundary layer thicknesses are determined using the method of Antonia and Luxton (1971, 1972), and the results are compared with the previous studies.
Book Synopsis Mechanics of Flow-Induced Sound and Vibration, Volume 2 by : William K. Blake
Download or read book Mechanics of Flow-Induced Sound and Vibration, Volume 2 written by William K. Blake and published by Academic Press. This book was released on 2017-08-14 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanics of Flow-Induced Sound and Vibration, Volume 2: Complex Flow-Structure Interactions, Second Edition, enables readers to fully understand flow-induced vibration and sound, unifying the disciplines of fluid dynamics, structural dynamics, vibration, acoustics, and statistics in order to classify and examine each of the leading sources of vibration and sound induced by various types of fluid motion. Starting from classical theories of aeroacoustics and hydroacoustics, a formalism of integral solutions valid for sources near boundaries is developed and then broadened to address different source types, including hydrodynamically induced cavitation and bubble noise, turbulent wall-pressure fluctuations, pipe and duct systems, lifting surface flow noise and vibration, and noise from rotating machinery. Each chapter is illustrated with comparisons of leading formulas and measured data. Combined with its companion book, Mechanics of Flow-Induced Sound and Vibration, Volume 1: General Concepts and Elementary Sources, the book covers everything an engineer needs to understand flow-induced sound and vibration. This book will be a vital source of information for postgraduate students, engineers and researchers with an interest in aerospace, ships and submarines, offshore structures, construction, and ventilation. Presents every important topic in flow-induced sound and vibration Covers all aspects of the topics addressed, from fundamental theory, to the analytical formulas used in practice Provides the building blocks of computer modeling for flow-induced sound and vibration
Book Synopsis Government Reports Annual Index by :
Download or read book Government Reports Annual Index written by and published by . This book was released on 1982 with total page 1008 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.
Download or read book Report written by and published by . This book was released on 1957 with total page 1180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Abstract Bulletin written by and published by . This book was released on 1982 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Government Reports Annual Index: Keyword A-L by :
Download or read book Government Reports Annual Index: Keyword A-L written by and published by . This book was released on 1982 with total page 1016 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Analysis of Turbulent Boundary-Layer Over Rough Surfaces with Application to Projectile Aerodynamics by : James E. Danberg
Download or read book Analysis of Turbulent Boundary-Layer Over Rough Surfaces with Application to Projectile Aerodynamics written by James E. Danberg and published by . This book was released on 1988 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new correlation of the roughness density effect on the intercept of the law of the wall and the equivalent sand roughness, has been developed. The data base used includes corrected results of Schlichting's rough channel experiment and those of twelve other studies. The roughness density parameter used is a product of the reference surface to the total frontal area ratio and a shape factor. For two dimensional roughness, the new parameter correlates data for circular wires with that of square bars. For three-dimensional roughnesses, it correlates results from all four types of roughness studied by Schlichting. The effect of three-dimensional roughness is a little smaller than that of two- dimensional roughness, having the same density parameter. A component build-up engineering analysis has been used to estimate the additional axial-force, due to grooves and threads, of projectiles. Comparison of this prediction technique and wind-tunnel data shows good agreement. Because the groove roughness, in the case considered here, is beyond the range of applicability of the new correlation, existing data are used to estimate an equivalent sand roughness. A turbulence model, based on that of Healzer and the equivalent sand roughness concept has been implemented in the Schiff and Steger PNS code. In order to numerically evaluate the conditions over a rough surface, a transition region between smooth and rough surfaces is introduced. This transition region allows the effect of the rough surface conditions to propagate into this viscous flow region in a realistic way. The predicted smooth body axial force coefficient, excluding the base drag, is five percent smaller than that measured in a wind tunnel test.
