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An Analytical Study Of The Effects Of Surface Roughness On A Compressible Turbulent Boundary Layer
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Book Synopsis An Analytical Study of the Effects of Surface Roughness on a Compressible Turbulent Boundary Layer by : Zakir H. Khan (SQDN LDR, Pakistani AF.)
Download or read book An Analytical Study of the Effects of Surface Roughness on a Compressible Turbulent Boundary Layer written by Zakir H. Khan (SQDN LDR, Pakistani AF.) and published by . This book was released on 1983 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Book Synopsis A Theoretical Analysis of the Effects of Surface Roughness on the Turbulent Boundary Layer in Compressible Flow with Zero Heat Transfer by : F. W. Fenter
Download or read book A Theoretical Analysis of the Effects of Surface Roughness on the Turbulent Boundary Layer in Compressible Flow with Zero Heat Transfer written by F. W. Fenter and published by . This book was released on 1955 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Analytical Study of the Effect of Surface Roughness on the Stability of a Heated Water Boundary Layer by : Michael A. Kosecoff
Download or read book An Analytical Study of the Effect of Surface Roughness on the Stability of a Heated Water Boundary Layer written by Michael A. Kosecoff and published by . This book was released on 1976 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: The onset of transition from laminar to turbulent flow in a high Reynolds number, water boundary layer was investigated with emphasis on predicting the global effects of distributed surface roughness on transition. The authors used the results of linear stability theory as an indicator of transition, but, this paper presents only comparisons of the stability results (not actual transition predictions). The effects of surface roughness on transition were induced by means of an existing phenomenological model for the effects of distributed roughness on the mean flow profiles. This model, originally developed for high Mach number, compressible boundary layers, was applied without change to the present incompressible, water boundary-layer environment, and identical values of the required empirical constants were used in both cases. One conclusion obtained from the numerical results is that the presence of favorable pressure gradients and/or surface heating make the boundary layer more susceptible to roughness, not only when compared in terms of the actual roughness height, but also when compared in terms of the roughness height to momentum thickness ratio. When the roughness is sufficiently large, its presence can change the effect of surface heat addition from a strongly stabilizing factor to a strongly destabilizing phenomena.
Download or read book משחקידע written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 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 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Influence of Roughness and Blowing on Compressible Turbulent Boundary Layer Flow by : Robert L. P. Voisinet
Download or read book Influence of Roughness and Blowing on Compressible Turbulent Boundary Layer Flow written by Robert L. P. Voisinet and published by . This book was released on 1979 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: The determination of the relative and combined effects of surface roughness and mass transfer on turbulent boundary-layer development, and in particular, on skin-friction drag was the prime objective of this study. Wind-tunnel tests were conducted in the NSWC Boundary-Layer Channel at a freestream Mach number of 2.9. The thick nozzle-wall boundary layer in the facility was subjected to a systematic variation of surface roughness and mass transfer conditions. Boundary-layer pressure and temperature surveys were obtained and skin friction was measured directly using a skin-friction balance which had a provision for active blowing through the floating drag element. Data comparisons with skin-friction theories and law-of-the-wall velocity profile correlations are presented. (Author).
Book Synopsis Receptivity and Transition to Turbulence of Supersonic Boundary Layers with Surface Roughness by : Nicola De Tullio
Download or read book Receptivity and Transition to Turbulence of Supersonic Boundary Layers with Surface Roughness written by Nicola De Tullio and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A deeper understanding of the different factors that influence the laminar-turbulent transition in supersonic boundary layers will help the design of efficient high-speed vehicles. In this work we study the effects of surface roughness on the stability and transition to turbulence of supersonic boundary layers. The investigation is carried out by direct numerical simulations (DNS) of the compressible Navier-Stokes equations and focuses on the modifications introduced in the transition process by localised roughness elements, for Mach numbers M∞ = 6.0 and M∞ = 2.5, and distributed slender pores at M∞ = 6.0. The first part of the investigation into the effects of localised roughness deals with the receptivity and initial exponential amplification of disturbances in boundary layers subjected to small external perturbations. Different transition scenarios are investigated by considering different free-stream disturbances and roughness elements with different heights. The results show that, for roughness heights approaching the local displacement thickness, transition is dominated by the growth of a number of instability modes in the roughness wake. These modes are damped by wall cooling and their receptivity is found to be more efficient in the case of free-stream disturbances dominated by sound. At M∞ = 6 the growth of Mack modes in the boundary layer is found to play a crucial role in the excitation of the most unstable wake modes. An investigation into the nonlinear stages of transition shows that the breakdown to turbulence starts with nonlinear interactions of the wake instability modes. This leads to the formation of a turbulent wedge behind the roughness element, which spreads laterally following mechanisms similar to those observed for the evolution of compressible turbulent spots. An oblique shock impinging on the transitional boundary layer significantly accelerates the breakdown process and leads to a wider turbulent wedge. The study ends with an analysis of porous walls as a passive method for transition control, which is carried out using a temporal DNS approach. The results show damping of both the primary, of second or Mack mode type, and secondary instabilities and indicate that, despite the high Mack number, first mode waves regain importance in this modified transition scenario.
Book Synopsis Air University Abstracts of Research Reports by :
Download or read book Air University Abstracts of Research Reports written by and published by . This book was released on 1984 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Government-wide Index to Federal Research & Development Reports by :
Download or read book Government-wide Index to Federal Research & Development Reports written by and published by . This book was released on 1967 with total page 690 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effects of Surface Roughness on the Flow Characteristics in a Turbulent Boundary Layer by :
Download or read book Effects of Surface Roughness on the Flow Characteristics in a Turbulent Boundary Layer written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1973 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 199? with total page 1316 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 with total page 908 pages. Available in PDF, EPUB and Kindle. Book excerpt:
