The Role of Skin-Friction Measurements in Boundary Layers with Variable Pressure Gradients

2006 ◽  
pp. 231-240 ◽  
Author(s):  
Hans-Hermann Fernholz
Keyword(s):  
Skin Friction ◽  
Boundary Layers ◽  
Variable Pressure ◽  
Pressure Gradients ◽  
Friction Measurements

Low-Reynolds-Number Turbulent Boundary Layers in Zero and Favorable Pressure Gradients

1983 ◽  
Vol 27 (03) ◽  
pp. 147-157 ◽  
Author(s):  
A. J. Smits ◽  
N. Matheson ◽  
P. N. Joubert
Keyword(s):  
Friction Coefficient ◽  
Skin Friction ◽  
Boundary Layers ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Skin Friction Coefficient ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients ◽  
Mean Flow ◽  
Low Reynolds

This paper reports the results of an extensive experimental investigation into the mean flow properties of turbulent boundary layers with momentum-thickness Reynolds numbers less than 3000. Zero pressure gradient and favorable pressure gradients were studied. The velocity profiles displayed a logarithmic region even at very low Reynolds numbers (as low as Rθ = 261). The results were independent of the leading-edge shape, and the pin-type turbulent stimulators performed well. It was found that the shape and Clauser parameters were a little higher than the correlation proposed by Coles [10], and the skin friction coefficient was a little lower. The skin friction coefficient behavior could be fitted well by a simple power-law relationship in both zero and favorable pressure gradients.

An Instrument for Skin-Friction Measurements in Thin Boundary Layers

1971 ◽  
Vol 93 (4) ◽  
pp. 571-575 ◽  
Author(s):  
J. L. Nash-Webber ◽  
G. C. Oates
Keyword(s):  
Pressure Gradient ◽  
Skin Friction ◽  
Boundary Layers ◽  
Compressible Boundary Layers ◽  
Calibration Relation ◽  
Simple Instrument ◽  
Friction Measurements ◽  
Universal Calibration

A simple instrument for skin-friction measurements in adiabatic turbulent compressible boundary-layers is described. Its small size makes its use possible in very thin boundary layers. A universal calibration relation is given. A method of applying the instrument to obtain hitherto unavailable measurements of skin-friction in flows with finite pressure-gradient is proposed.

scholarly journals Skin-friction Measurements in Turbulent Boundary Layers

2020 ◽  
Vol 12 (1) ◽  
pp. 1-15
Author(s):  
Cristian Rendon Cardona ◽  
Zhoushun Ruan ◽  
Oscar Ruiz Salguero
Keyword(s):  
Skin Friction ◽  
Boundary Layers ◽  
Turbulent Boundary Layers ◽  
Friction Measurements

Evaluation of Turbulent Spot Production Rate in Boundary Layers Under Variable Pressure Gradients for Gas Turbine Applications

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
M. Dellacasagrande ◽  
D. Lengani ◽  
D. Simoni ◽  
M. Ubaldi ◽  
P. Zunino
Keyword(s):  
Production Rate ◽  
Boundary Layers ◽  
Turbulence Intensity ◽  
Separated Flow ◽  
Transition Process ◽  
Variable Pressure ◽  
Pressure Gradients ◽  
Turbulent Spot ◽  
Flow Parameters ◽  
Transition Length

Abstract The paper presents several results from an experimental data base on transitional boundary layers developing on a flat plate installed within a variable area opening endwall channel. Measurements have been carried out by means of time-resolved particle image velocimetry (PIV). The overall test matrix spans three Reynolds numbers, four freestream turbulence intensity levels, and four different flow pressure gradients. For each condition, 16,000 instantaneous flow fields have been acquired in order to obtain high statistical accuracy. The flow parameters have been varied in order to provide a gradual shift of the mode of transition from a by-pass process to separated flow transition. In order to quantify the influence of the flow parameter variation on the boundary layer transition process, the transition onset and end positions, and the turbulent spot production rate have been evaluated with a wavelet-based intermittency detection technique for every condition exhibiting a complete transition process. The by-pass transition mode has the longest transition length that decreases with increasing the Reynolds number. The transition length of the separated flow case is smaller than the by-pass one, and the variation of the flow parameters has a similar impact. The variation of the inlet turbulence intensity has a small influence on this parameter except for the condition at the highest turbulence intensity that always shows the lowest turbulent spot production rate because a by-pass type transition occurs. This large amount of data has been used to develop new correlations used to predict the spot production rate and the transition length in attached and separated flows.

Prediction of Transpired Turbulent Boundary Layers With Arbitrary Pressure Gradients

1997 ◽  
Vol 119 (3) ◽  
pp. 526-532 ◽  
Author(s):  
Miodrag Oljaca ◽  
James Sucec
Keyword(s):  
Experimental Data ◽  
Skin Friction ◽  
Boundary Layers ◽  
Integral Method ◽  
Skin Friction Coefficient ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients ◽  
Wide Range ◽  
Better Than ◽  
Good Agreement

An integral method, using Coles combined inner and outer law as the velocity profile, is developed for calculation of turbulent boundary layers with blowing or suction and pressure gradients. The resulting ordinary differential equations are solved numerically for the distribution of skin friction coefficient and integral thickness along the surface. Comparisons of predicted skin friction coefficients with experimental data are made for a wide range of blowing and suction rates and for various pressure gradients, including adverse, zero and a strong favorable gradient. In addition to good agreement with experimental data for constant blowing fractions F, the method is also successfully tested on cases where the blowing fraction is variable with position. Predictions, in general, exhibit satisfactory agreement with the data. The integral method predictions are comparable to, or better than, a number of finite difference procedures in a limited number of cases where comparisons were made.

Influence of the Wake Component on Turbulent Skin Friction at Subsonic and Supersonic Speeds

1979 ◽  
Vol 30 (4) ◽  
pp. 590-606 ◽  
Author(s):  
D.G. Mabey
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Velocity Profile ◽  
Skin Friction ◽  
Boundary Layers ◽  
Significant Influence ◽  
Turbulent Boundary Layers ◽  
Number Range ◽  
Reynolds Number Range ◽  
Friction Measurements

SummarySome velocity profile and skin friction measurements for turbulent boundary layers at subsonic and supersonic speeds are reviewed to derive the magnitude of the wake component and the effects of its variation with Reynolds number on predictions of skin friction. As Reynolds number increases the wake component increases rapidly, reaches a maximum and then decreases. The measurements considered suggest that this maximum may be higher at supersonic speeds than at subsonic speeds. This wake component variation has a significant influence on predictions of skin friction in the Reynolds number range of interest on wind tunnel models.

The measurement of skin friction in turbulent boundary layers with adverse pressure gradients

1969 ◽  
Vol 35 (4) ◽  
pp. 737-757 ◽  
Author(s):  
K. C. Brown ◽  
P. N. Joubert
Keyword(s):  
Shear Stress ◽  
Skin Friction ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients ◽  
Two Dimensional ◽  
Direct Measurements ◽  
Floating Element ◽  
Dimensional Boundary

This paper describes a floating-element skin friction meter which has been designed for use in adverse pressure gradients. The effects of secondary forces on the element, which arise from the pressure gradient, are examined in some detail. The limitations of various methods of measuring wall shear stress are discussed and the results from the floating element device are compared with measurements taken in a two-dimensional boundary layer using Preston tubes and velocity profiles. As it is planned to use the instrument later for direct measurements of the shear stress in three-dimensional boundary layers, the relevance of the instrument to this situation is also discussed.

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