Accession Number : ADA138156

Title :   Study of Unsteady Turbulent Boundary Layers.

Descriptive Note : Interim technical rept. 1 Sep 80-31 Oct 83,

Corporate Author : IOWA INST OF HYDRAULIC RESEARCH IOWA CITY

Personal Author(s) : Menendez,A N ; Ramaprian,B R

PDF Url : ADA138156

Report Date : 31 Dec 1983

Pagination or Media Count : 222

Abstract : A turbulent boundary layer, subjected to a free-stream velocity which changes sinusiodally in time under a zero time mean pressure gradient, is studied both experimentally and analytically. Using a two-component 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 time-mean 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 All the experimental data have been archived on magnetic tape. (Author)

Descriptors :   *Turbulent boundary layer, *Unsteady flow, Pressure gradients, Oscillation, Periodic variations, Velocity, Free stream, Walls, Shear stresses, Time, Mean, Frequency, Reynolds number, Data acquisition, Laser anemometers, Doppler systems, Heat flux, Gages, Pipes, Channel flow

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE