Study of unsteady turbulent boundary layers
Abstract
A turbulent boundary layer, subjected to a freestream velocity which changes sinusiodally in time under a zero time mean pressure gradient, is studied both experimentally and analytically. Using a twocomponent Laser Doppler Anemometer and a Heat Flux Gage, detailed and high quality information is obtained on the instantaneous velocity distribution and wall shear stress, respectively, at various stations. An asymptotic theory, for large Reynolds numbers, is developed for the oscillatory motion. It is valid for both boundary layers at arbitrary timemean pressure gradients and fully developed pipe and channel flow, and is successfully applied to the present and previous available experimental information. The theory identifies two frequency parameters, in terms of which four different frequency regimes are defined. Similarity laws are identified for each one of these frequency regimes. All the experimental data have been archived on magnetic tape.
 Publication:

Iowa University Progress Report
 Pub Date:
 December 1983
 Bibcode:
 1983iowa.reptR....M
 Keywords:

 Channel Flow;
 Pipe Flow;
 Turbulent Boundary Layer;
 Unsteady Flow;
 Data Acquisition;
 Doppler Effect;
 Frequencies;
 Heat Flux;
 Laser Anemometers;
 Mean;
 Oscillations;
 Periodic Variations;
 Pipes (Tubes);
 Pressure Gradients;
 Reynolds Number;
 Shear Stress;
 Time;
 Velocity;
 Walls;
 Fluid Mechanics and Heat Transfer