The Wall Shear Stress Signature of a Turbulent Spot: Direct Measurements and Momentum Integral Calculations

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.

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THE DEVELOPMENT OF UNDULAR BORES WITH FRICTION

Coastal Engineering Proceedings ◽

10.9753/icce.v12.28 ◽

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.

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Can We Ever Rely on Results from Wall-Bounded Turbulent Flows Without Direct Measurements of Wall Shear Stress?

24th AIAA Aerodynamic Measurement Technology and Ground Testing Conference ◽

10.2514/6.2004-2392 ◽

2004 ◽

Cited By ~ 20

Author(s):

Hassan Nagib ◽

Chris Christophorou ◽

Jean-Daniel Ruedi ◽

Peter Monkewitz ◽

Jens Osterlund ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Turbulent Flows ◽

Direct Measurements ◽

Wall Shear

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Wall Shear Stress Measurement on Curve Objects with PIV in Connection to Benthic Fauna in Regulated Rivers

Water ◽

10.3390/w11040650 ◽

2019 ◽

Vol 11 (4) ◽

pp. 650 ◽

Cited By ~ 3

Author(s):

S. M. Sayeed Bin Asad ◽

Tord Staffan Lundström ◽

Anders G. Andersson ◽

Johan Gunnar I. Hellström ◽

Kjell Leonardsson

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Stress Measurement ◽

Flow Characteristics ◽

Benthic Fauna ◽

Flow Speed ◽

Regulated Rivers ◽

Direct Measurements ◽

Stress Changes ◽

Wall Shear

The flow characteristics in the vicinity of a set of half-cylinders of different sizes simulating benthic objects were studied experimentally using particle image velocimetry (PIV). The cylinders were mounted on the bottom of an open channel, and the influence of the flow speed on the distribution of the shear stress along the bottom geometry was investigated. Of special interest was how the shear stress changes close to the wall as a function of the flow speed and cylinder arrangement. It was found that the shear stress varies significantly as a function of position. This implies habitat heterogeneity allowing benthic invertebrates with different shear stress tolerance exists when the bottom consists of differently sized stones. It was also shown that direct measurements of near wall velocity gradients are necessary to accurately calculate the wall shear stress for more complex geometries.

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