About turbulence statistics in the outer part of a boundary layer developing over two-dimensional surface roughness

2012 ◽  
Vol 24 (7) ◽  
pp. 075112 ◽  
Author(s):  
Per-Åge Krogstad ◽  
Vladislav Efros
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Outer Part ◽  
Two Dimensional ◽  
Turbulence Statistics ◽  
Dimensional Surface

Acoustic receptivity and evolution of two-dimensional and oblique disturbances in a Blasius boundary layer

2001 ◽  
Vol 432 ◽  
pp. 69-90 ◽  
Author(s):  
RUDOLPH A. KING ◽  
KENNETH S. BREUER
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Acoustic Wave ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Surface Waviness ◽  
S Wave ◽  
Boundary Layer Instability ◽  
Blasius Boundary Layer ◽  
Tollmien Schlichting

An experimental investigation was conducted to examine acoustic receptivity and subsequent boundary-layer instability evolution for a Blasius boundary layer formed on a flat plate in the presence of two-dimensional and oblique (three-dimensional) surface waviness. The effect of the non-localized surface roughness geometry and acoustic wave amplitude on the receptivity process was explored. The surface roughness had a well-defined wavenumber spectrum with fundamental wavenumber kw. A planar downstream-travelling acoustic wave was created to temporally excite the flow near the resonance frequency of an unstable eigenmode corresponding to kts = kw. The range of acoustic forcing levels, ε, and roughness heights, Δh, examined resulted in a linear dependence of receptivity coefficients; however, the larger values of the forcing combination εΔh resulted in subsequent nonlinear development of the Tollmien–Schlichting (T–S) wave. This study provides the first experimental evidence of a marked increase in the receptivity coefficient with increasing obliqueness of the surface waviness in excellent agreement with theory. Detuning of the two-dimensional and oblique disturbances was investigated by varying the streamwise wall-roughness wavenumber αw and measuring the T–S response. For the configuration where laminar-to-turbulent breakdown occurred, the breakdown process was found to be dominated by energy at the fundamental and harmonic frequencies, indicative of K-type breakdown.

On the effects of two-dimensional Reynolds roughness in hydrodynamic lubrication

1978 ◽  
Vol 364 (1716) ◽  
pp. 89-106 ◽  
Keyword(s):  
Surface Roughness ◽  
Numerical Computation ◽  
Autocorrelation Function ◽  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
The Other ◽  
Roughness Height ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Dimensional Surface

The hydrodynamic lubrication of rough surfaces is analysed with the Reynolds equation, whose application requires the roughness spacing to be large, and the roughness height to be small, compared with the thick­ness of the fluid film. The general two-dimensional surface roughness is considered, and results applicable to any roughness structure are obtained. It is revealed analytically that two types of term contribute to roughness effects: one depends on the shape of the autocorrelation function and the other does not. The former contribution was neglected by previous workers. The numerical computation of an example shows that these two contributions are comparable in magnitude.

Development of the Reattached Flow Behind Surface-Mounted Two-Dimensional Prisms

1988 ◽  
Vol 110 (2) ◽  
pp. 127-133 ◽  
Author(s):  
J. Antoniou ◽  
G. Bergeles
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Open Circuit ◽  
Two Dimensional ◽  
Blow Down ◽  
Length Scales ◽  
Turbulent Eddies ◽  
Flow Parameters ◽  
Varying Length ◽  
Dimensional Surface

Velocity and turbulence measurements are presented for the region after reattachment behind a two dimensional surface-mounted prism of varying length. The prism is mounted on the floor of an open circuit blow down wind tunnel and flow parameters for the developing boundary layer are deduced from the measurements; longitudinal integral time and length scales are estimated through autocorrelations. Reattchment on top of the prism, due to its increased length, affects the characteristics of the developing boundary layer; in this case the shear layer originating from the up-stream edge of the prism splits twice at reattachment points on top and behind the prism and the integral length scales of the turbulent eddies are found to be smaller due to the splitting.

scholarly journals Modeling of Turbulent Fluid Flow Over a Rough Wall With or Without Suction

2003 ◽  
Vol 125 (4) ◽  
pp. 636-642 ◽  
Author(s):  
G. Gre´goire ◽  
M. Favre-Marinet ◽  
F. Julien Saint Amand
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Fluid Flow ◽  
Rough Boundary ◽  
Two Dimensional ◽  
Turbulent Fluid Flow ◽  
Boundary Layer Suction ◽  
Zonal Model ◽  
Impermeable Wall ◽  
Logarithmic Law

The turbulent flow close to a wall with two-dimensional roughness is computed with a two-layer zonal model. For an impermeable wall, the classical logarithmic law compares well with the numerical results if the location of the fictitious wall modeling the surface is considered at the top of the rough boundary. The model developed by Wilcox for smooth walls is modified to account for the surface roughness and gives satisfactory results, especially for the friction coefficient, for the case of boundary layer suction.

An Investigation of two Turbulent Flows over Smooth and Rough Surfaces

1974 ◽  
Vol 16 (2) ◽  
pp. 71-78 ◽  
Author(s):  
W. K. Allan ◽  
V. Sharma
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Turbulent Boundary Layer ◽  
Turbulent Flows ◽  
Smooth Surface ◽  
Two Dimensional ◽  
Mean Velocity ◽  
Turbulent Boundary Layer Flow ◽  
Layer Flow

Experimental data for two-dimensional, low-speed, turbulent boundary layer flow has been used to verify the description of mean-velocity distributions proposed by Allan and to re-evaluate the entrainment function. The independence of pressure gradient and surface roughness as regards their effects on velocity profiles has been demonstrated. Boundary layer predictions agree with experimental data for a smooth surface, but further investigation is required for flow over a rough surface.

Sign in / Sign up

Export Citation Format

Share Document