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Author: Takeshi Kawatani
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 284
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Author: Takeshi Kawatani
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 284
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Author: Junghwa Seo
Publisher:
ISBN:
Category :
Languages : en
Pages : 267
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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A comprehensive investigation of the influence of surface roughness on the mean and turbulent flow properties of a high-speed turbulent boundary layer flow was performed. Six wall topologies, including a smooth and five rough surfaces consisting of three random sand-grain plates and two uniformly machined plates (k = 0 - 1.7 mm), were tested at three high Reynolds number (Re/m = 2 x lO (exp 7) Mach numbers (0.22, 0.65 and 2.75) . Mean flow measurements included surveys of the velocity and density. Turbulence quantities included measurements of the kinematic velocity turbulence intensities, mass flux turbulence intensities, kinematic Reynolds shear stress, compressible Reynolds shear stress, density-transverse-velocity fluctuation correlation, velocity spectra, auto-correlations, micro- and integral-scales and turbulent structure angles. Numerical simulations included evaluating three algebraic turbulence models with a boundary layer program. A three-year program was performed.
Author: J. Leith Potter
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 166
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Condtions encountered in the high Mach number flow regime are show to profoundly affect the longitudinal extent of the boundary layer from beginning to end of transition, the distribution of fluctuation energy in the laminar layer, and effectiveness of surface roughness in promoting transition. A critical layer of intense local energy fluctuations was found at all Mach numbers studied. The existence of such a critical layer is predicted by stability theory. Hot-wire surveys of the laminar, transitional, and turbulent boundary layers are presented to illustrate the critical layer in laminar flow and subsequent development into the transition process. The relation between boundary layer transition on flat plates and cones in supersonic flow is explored and a process for correcting data to account for leading edge bluntness is devised. On the basis of a comparison of data corrected for the effects of leading edge geometry, it is shown that the Reynolds umber of transition on a cone is three times that on a vanishingly thin flate plate. Close agreement between data from various wind tunnels is demonstrated. Study of the effect of finite leading edges yields significant illustrations of the influence of unit Reynolds number on boundary layer transition. A correlation of the effects of surface roughness on transition is achieved. This treatment includes two- and three-dimensional roughness in both subsonic and supersonic streams. At this time only zero pressure gradients have been studied. The entire range of movement of transition from its position with no roughness up to its reaching the roughness element is describable by the procedure give. Examples of application of the correlation results show excellent agreement with experimental data from a variety of sources. Implications concerning tripping hypersonic boundary layers are discussed.
Author: Robert M. Latin
Publisher:
ISBN: 9781423562139
Category : Surface roughness
Languages : en
Pages : 362
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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.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309254671
Category : Science
Languages : en
Pages : 1024
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Book Description
"Vive la Revolution!" was the theme of the Twenty-Third Symposium on Naval Hydrodynamics held in Val de Reuil, France, from September 17-22, 2000 as more than 140 experts in ship design, construction, and operation came together to exchange naval research developments. The forum encouraged both formal and informal discussion of presented papers, and the occasion provides an opportunity for direct communication between international peers. This book includes sixty-three papers presented at the symposium which was organized jointly by the Office of Naval Research, the National Research Council (Naval Studies Board), and the Bassin d'Essais des Carènes. This book includes the ten topical areas discussed at the symposium: wave-induced motions and loads, hydrodynamics in ship design, propulsor hydrodynamics and hydroacoustics, CFD validation, viscous ship hydrodynamics, cavitation and bubbly flow, wave hydrodynamics, wake dynamics, shallow water hydrodynamics, and fluid dynamics in the naval context.
Author: Felix W. Fenter
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages :
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Author: James R. Hall
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 34
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Author: Felix W. Fenter
Publisher:
ISBN:
Category :
Languages : en
Pages : 63
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A theory is described which can be used to predict accurately the skin friction drag of surfaces with uniform grain-type roughness. The roughness does not necessarily have to extend to the leading edge of the surface for an accurate calculation to be made. Uniform surface roughness composed of spherical beads does not affect the boundary layer in a manner significantly different from grain-type roughness, provided that the grains and the spheres are bonded to the surface in a similar manner. Consequently, the theory accurately predicts the effects of spherical roughness elements on skin friction under these conditions. The effect of a given type of roughness on turbulent boundary layer characteristics is strongly dependent upon the density of distribution of the roughness elements. The effect of maximum density V-grooves on turbulent boundary layer characteristics is dependent upon the sweepback angle. The effect of increasing sweepback is to reduce the skin friction drag. (Author).
Author:
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 102
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