scholarly journals THE DEVELOPMENT OF UNDULAR BORES WITH FRICTION

1970 ◽  
Vol 1 (12) ◽  
pp. 28
Author(s):  
O. Hawaleshka ◽  
S.B. Savage
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Wave Profile ◽  
Wall Friction ◽  
Slight Reduction ◽  
Initial Development ◽  
Theoretical Predictions ◽  
Wall Shear ◽  
Momentum Integral

A theoretical and experimental study of the initial development of undular bores in two-dimensional, rectangular channels with and without boundary friction was performed Equations similar to those of Boussmesq, but including higher order and wall friction terms are presented and solved numerically by an implicit finite difference method A Pohlhausentype boundary layer momentum integral method is used to obtain the wall shear stress distribution under a developing long wave from the consideration of the boundary layer underneath it The solution is performed in a quasi-iterative manner proceeding from the friction coefficient calculation for an initially assumed wave profile to the inclusion of this coefficient in the calculation of a new wave profile at an advanced time Comparisons of theoretical and experimental results are given For the initial development of the undular bore with which the present work is concerned, the measurements are found to be m reasonable agreement with the theoretical predictions The effect of the wall shear stress manifests itself mainly in a slight reduction of the wave amplitudes.

On the Effects of a Flexible Structure on Boundary Layer Stability and Transition

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Ashraf Al Musleh ◽  
Abdelkader Frendi
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Young Modulus ◽  
Boundary Layer Transition ◽  
Beam Equation ◽  
Flexible Structure ◽  
Boundary Layer Stability ◽  
Wall Shear ◽  
Fluid Wall Shear Stress

Delaying the onset of boundary layer transition has become a major research area in the last few years. This delay can be achieved by either active or passive control techniques. In the present paper, the effects of flexible or compliant structures on boundary layer stability and transition is studied. The Orr-Sommerfeld equation coupled to a beam equation representing the flexible structure is solved for a Blasius type boundary layer. A parametric study consisting of the beam thickness and material properties is carried out. In addition, the effect of fluid wall shear stress on boundary layer stability is analyzed. It is found that high density and high Young modulus materials behave like rigid structures and therefore do not alter the stability characteristic of the boundary layer. Whereas low density and low Young modulus materials are found to stabilize the boundary layer. High values of fluid wall shear stress are found to destabilize the boundary layer. Our results are in good agreement with those published in the literature.

A Superposition Analysis of the Turbulent Boundary Layer in an Adverse Pressure Gradient

1951 ◽  
Vol 18 (1) ◽  
pp. 95-100
Author(s):  
Donald Ross ◽  
J. M. Robertson
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Pressure Recovery ◽  
Stress Coefficient ◽  
Wall Shear

Abstract As an interim solution to the problem of the turbulent boundary layer in an adverse pressure gradient, a super-position method of analysis has been developed. In this method, the velocity profile is considered to be the result of two effects: the wall shear stress and the pressure recovery. These are superimposed, yielding an expression for the velocity profiles which approximate measured distributions. The theory also leads to a more reasonable expression for the wall shear-stress coefficient.

Direct Force Wall Shear Measurements in Pressure-Driven Three-Dimensional Turbulent Boundary Layers

1982 ◽  
Vol 104 (2) ◽  
pp. 150-155 ◽  
Author(s):  
J. E. McAllister ◽  
F. J. Pierce ◽  
M. H. Tennant
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Three Dimensional ◽  
Turbulent Boundary Layers ◽  
Direct Measurements ◽  
Stress Directions ◽  
Wall Flow ◽  
Wall Shear ◽  
Pressure Driven

Unique, simultaneous direct measurements of the magnitude and direction of the local wall shear stress in a pressure-driven three-dimensional turbulent boundary layer are presented. The flow is also described with an oil streak wall flow pattern, a map of the wall shear stress-wall pressure gradient orientations, a comparison of the wall shear stress directions relative to the directions of the nearest wall velocity as measured with a typical, small boundary layer directionally sensitive claw probe, as well as limiting wall streamline directions from the oil streak patterns, and a comparison of the freestream streamlines and the wall flow streamlines. A review of corrections for direct force sensing shear meters for two-dimensional flows is presented with a brief discussion of their applicability to three-dimensional devices.

Laminar boundary layer with constant wall shear stress.

AIAA Journal ◽  
1968 ◽  
Vol 6 (12) ◽  
pp. 2432-2434 ◽  
Author(s):  
VICTOR ZAKKAY ◽  
EDGAR ALZNER
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Laminar Boundary Layer ◽  
Wall Shear
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