Vorticity and Drag Measurements in Rough-wall Turbulent Boundary Layers PDF Download
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Author: Alan Baker Folz
Publisher:
ISBN:
Category : Drag (Aerodynamics)
Languages : en
Pages : 354
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Book Description
Author: Alan Baker Folz
Publisher:
ISBN:
Category : Drag (Aerodynamics)
Languages : en
Pages : 354
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 16
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Book Description
The scientific goals of this work are to develop a complete physical model of turbulence in wall boundary layers and to develop means of describing and modeling surface roughness effect. We make use of recent developments in our understanding of the mechanistic structure of near wall turbulence for smooth walls at low Reynolds numbers to understand how large Reynolds number and wall roughness affect turbulence. We build upon experimental and computational evidence from smooth walls to extend the mechanistic picture of turbulence based on a paradigm of hierarchy of hairpin packets to high Reynolds number, when roughness effect increases in importance. Both experimental measurements of velocity field in smooth and rough walls and direct numerical simulations of evolution and interaction of hairpin vortices are used.
Author: W. Tillmann
Publisher:
ISBN:
Category : Drag (Aerodynamics)
Languages : en
Pages : 44
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Book Description
In connection with earlier measurements by K. Wieghardt the increase of the turbulent friction drag was determined for some additional types of common surface irregularities.
Author: Anthony Edward Perry
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 340
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Book Description
The paper describes a detailed experimental study of turbulent boundary layer development over rough walls in both zero and adverse pressure gradients. Skin friction was determined by pressure tapping the roughness elements and measuring their form drag. Two wall roughness geometries were chosen each giving a different law of behaviour. However, it has been found that results for both types of roughness correlate with a Reynolds number based on wall shear velocity and on the distance below the crests of the elements from which the logarithmic distribution of velocity is measured. One important implication of this is that a zero pressure gradient boundary layer with a cavity type rough wall conforms to Rotta's condition of precise self preserving flow. (Author).
Author: P. M. Ligrani
Publisher:
ISBN:
Category : Frictional resistance (Hydrodynamics)
Languages : en
Pages : 272
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Book Description
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).
Author: Paul S. Granville
Publisher:
ISBN:
Category : Turbulence
Languages : en
Pages : 52
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 87
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Book Description
Velocity and vorticity measurements have been obtained at two y+ values: 810 and 2,150, in the very high R(theta)(O 10(exp 6)) turbulent boundary layer at the SLTEST site, Dugway Proving Grounds, Utah. Detailed descriptions of the experimental procedures are reported in order to allow the processed results to be evaluated. The research focus is on the velocity-vorticity products that appear in the formal statement of the vertical gradient of the kinematic Reynolds stress. Statistical data for the velocity and vorticity fields are presented. The cospectra for v(omega)z and w(omega)y show the unexpected result that intermediate wave numbers provide the majority of the contributions to these products.
Author: Jinjun Wang
Publisher: Cambridge University Press
ISBN: 1107161568
Category : Science
Languages : en
Pages : 293
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Book Description
Master the theory, applications and control mechanisms of flow control techniques.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 836
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
