Experimental determination of skin friction coefficient in a turbulent boundary layer with a longitudinal pressure gradient

1976 ◽  
Vol 30 (5) ◽  
pp. 527-533 ◽  
Author(s):  
E. U. Repik ◽  
V. K. Kuzenkov
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Experimental Determination ◽  
Skin Friction ◽  
Skin Friction Coefficient ◽  
Longitudinal Pressure Gradient

The skin-friction coefficient of a turbulent boundary layer modified by a large-eddy break-up device

2021 ◽  
Vol 33 (3) ◽  
pp. 035153
Author(s):  
I. C. Chan ◽  
R. Örlü ◽  
P. Schlatter ◽  
R. C. Chin
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Skin Friction Coefficient ◽  
Large Eddy ◽  
Break Up

scholarly journals Large-eddy simulation of the zero-pressure-gradient turbulent boundary layer up to Reθ = O(1012)

2011 ◽  
Vol 686 ◽  
pp. 507-533 ◽  
Author(s):  
M. Inoue ◽  
D. I. Pullin
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Pressure Gradient ◽  
Skin Friction Coefficient ◽  
Smooth Wall ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Near Wall

AbstractA near-wall subgrid-scale (SGS) model is used to perform large-eddy simulation (LES) of the developing, smooth-wall, zero-pressure-gradient flat-plate turbulent boundary layer. In this model, the stretched-vortex, SGS closure is utilized in conjunction with a tailored, near-wall model designed to incorporate anisotropic vorticity scales in the presence of the wall. Large-eddy simulations of the turbulent boundary layer are reported at Reynolds numbers ${\mathit{Re}}_{\theta } $ based on the free-stream velocity and the momentum thickness in the range ${\mathit{Re}}_{\theta } = 1{0}^{3} \text{{\ndash}} 1{0}^{12} $. Results include the inverse square-root skin-friction coefficient, $ \sqrt{2/ {C}_{f} } $, velocity profiles, the shape factor $H$, the von Kármán ‘constant’ and the Coles wake factor as functions of ${\mathit{Re}}_{\theta } $. Comparisons with some direct numerical simulation (DNS) and experiment are made including turbulent intensity data from atmospheric-layer measurements at ${\mathit{Re}}_{\theta } = O(1{0}^{6} )$. At extremely large ${\mathit{Re}}_{\theta } $, the empirical Coles–Fernholz relation for skin-friction coefficient provides a reasonable representation of the LES predictions. While the present LES methodology cannot probe the structure of the near-wall region, the present results show turbulence intensities that scale on the wall-friction velocity and on the Clauser length scale over almost all of the outer boundary layer. It is argued that LES is suggestive of the asymptotic, infinite Reynolds number limit for the smooth-wall turbulent boundary layer and different ways in which this limit can be approached are discussed. The maximum ${\mathit{Re}}_{\theta } $ of the present simulations appears to be limited by machine precision and it is speculated, but not demonstrated, that even larger ${\mathit{Re}}_{\theta } $ could be achieved with quad- or higher-precision arithmetic.

Experimental Investigation of Turbulent Boundary Layers Under Favorable Pressure Gradient

2010 ◽  
Author(s):  
Pranav Joshi ◽  
Joseph Katz
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Pressure Gradient ◽  
Skin Friction ◽  
Velocity Profiles ◽  
Skin Friction Coefficient ◽  
Mean Velocity ◽  
Freestream Velocity ◽  
Favorable Pressure Gradient ◽  
The Mean

The goal of this research is to study the effect of favorable pressure gradient (FPG) on the near wall structures of a turbulent boundary layer on a smooth wall. 2D-PIV measurements have been performed in a sink flow, initially at a coarse resolution, to characterize the development of the mean flow and (under resolved) Reynolds stresses. Lack of self-similarity of mean velocity profiles shows that the boundary layer does not attain the sink flow equilibrium. In the initial phase of acceleration, the acceleration parameter, K = v/U2dU/dx, increases from zero to 0.575×10−6, skin friction coefficient decreases and mean velocity profiles show a log region, but lack universality. Further downstream, K remains constant, skin friction coefficient increases and the mean velocity profiles show a second log region away from the wall. In the initial part of the FPG region, all the Reynolds stress components decrease over the entire boundary layer. In the latter phase, they continue to decrease in the middle of the boundary layer, and increase significantly close to the wall (below y∼0.15δ), where they collapse when normalized with the local freestream velocity. Turbulence production and wallnormal transport, scaled with outer units, show self-similar profiles close to the wall in the constant K region. Spanwise-streamwise plane data shows evidence of low speed streaks in the log layer, with widths scaling with the boundary layer thickness.

Measurement and Calculation of Fluid Dynamic Characteristics of Rough-Wall Turbulent Boundary-Layer Flows

1993 ◽  
Vol 115 (3) ◽  
pp. 383-388 ◽  
Author(s):  
M. H. Hosni ◽  
H. W. Coleman ◽  
R. P. Taylor
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Rough Surface ◽  
Skin Friction Coefficient ◽  
Rough Wall ◽  
Momentum Thickness ◽  
Boundary Layer Flows ◽  
Mean Velocity

Experimental measurements of profiles of mean velocity and distributions of boundary-layer thickness and skin friction coefficient from aerodynamically smooth, transitionally rough, and fully rough turbulent boundary-layer flows are presented for four surfaces—three rough and one smooth. The rough surfaces are composed of 1.27 mm diameter hemispheres spaced in staggered arrays 2, 4, and 10 base diameters apart, respectively, on otherwise smooth walls. The current incompressible turbulent boundary-layer rough-wall air flow data are compared with previously published results on another, similar rough surface. It is shown that fully rough mean velocity profiles collapse together when scaled as a function of momentum thickness, as was reported previously. However, this similarity cannot be used to distinguish roughness flow regimes, since a similar degree of collapse is observed in the transitionally rough data. Observation of the new data shows that scaling on the momentum thickness alone is not sufficient to produce similar velocity profiles for flows over surfaces of different roughness character. The skin friction coefficient data versus the ratio of the momentum thickness to roughness height collapse within the data uncertainty, irrespective of roughness flow regime, with the data for each rough surface collapsing to a different curve. Calculations made using the previously published discrete element prediction method are compared with data from the rough surfaces with well-defined roughness elements, and it is shown that the calculations are in good agreement with the data.

The Effect of Biofilms on Turbulent Boundary Layers

1999 ◽  
Vol 121 (1) ◽  
pp. 44-51 ◽  
Author(s):  
M. P. Schultz ◽  
G. W. Swain
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Layer Structure ◽  
Reynolds Shear Stress ◽  
Skin Friction Coefficient ◽  
Laser Doppler Velocimeter ◽  
Reynolds Stresses ◽  
The Mean

Materials exposed in the marine environment, including those protected by antifouling paints, may rapidly become colonized by microfouling. This may affect frictional resistance and turbulent boundary layer structure. This study compares the mean and turbulent boundary layer velocity characteristics of surfaces covered with a marine biofilm with those of a smooth surface. Measurements were made in a nominally zero pressure gradient, boundary layer flow with a two-component laser Doppler velocimeter at momentum thickness Reynolds numbers of 5600 to 19,000 in a recirculating water tunnel. Profiles of the mean and turbulence velocity components, including the Reynolds shear stress, were measured. An average increase in the skin friction coefficient of 33 to 187 percent was measured on the fouled specimens. The skin friction coefficient was found to be dependent on both biofilm thickness and morphology. The biofilms tested showed varying effect on the Reynolds stresses when those quantities were normalized with the friction velocity.

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