Evaluation of the time dependent surface shear stress in turbulent flows
Abstract
The time dependent surface shear stress has been evaluated using surface heat transfer measurements. For fully developed turbulent pipe and open channel water flows, and incompressible and compressible turbulent boundary layer air flows the measurements indicate the absolute magnitude of the surface shear stress fluctuations will be greater than two times the mean values. The rootmeansquare shear stress fluctuations were of the order of 0.2 to 0.4 times the mean surface shear values. Due to these large surface shear stress fluctuations and the nonlinear relation between heat transfer and shear stress, a special technique has been developed to evaluate the measurements. It was found that the nonlinear averaging errors for a hot filmsurface shear stress gauge in a fully developed pipe flow was of the order of 10 percent at low velocities. A hot wiresurface shear stress gauge was employed for measurements of turbulent boundary layers in air.
 Publication:

American Society of Mechanical Engineers
 Pub Date:
 December 1979
 Bibcode:
 1979asme.meetV....S
 Keywords:

 Heat Transfer;
 Shear Flow;
 Shear Stress;
 Surface Layers;
 Time Dependence;
 Turbulent Boundary Layer;
 Channel Flow;
 Flow Measurement;
 Nonlinear Equations;
 Pipe Flow;
 Pressure Gradients;
 Probability Distribution Functions;
 RootMeanSquare Errors;
 Water Flow;
 Fluid Mechanics and Heat Transfer