Accession Number : AD0626298

Title :   THE INTERACTION OF TURBULENCE WITH RAPID UNIFORM SHEAR,

Corporate Author : STANFORD UNIV CALIF DEPT OF AERONAUTICS AND ASTRONAUTICS

Personal Author(s) : Moffatt,H. K.

Report Date : AUG 1965

Pagination or Media Count : 41

Abstract : The linear inviscid response of an initially weak random velocity perturbation to a uniform shearing motion is analysed, first in terms of the individual Fourier components of the perturbation field, then in terms of the development of its spectrum tensor. This analysis reveals that the dominant contribution, both to the disturbance energy and to the Reynolds stress generated, comes ultimately from eddies having a cylindrical structure, the axes of the cylinders being parallel to the shear force. The results are relevant to two aspects of turbulent shear flow: (1) the equilibrium structure of a small turbulent 'parcel' of fluid subjected to persistent almost uniform shear, and (2) the structure of the 'large eddies' which derive their energy directly from the shearing of the mean flow. Certain aspects of the distortion of turbulence by shear that is weakly non-uniform are also considered, and it is found that the gradient in the Reynolds stress generated tends to make the mean velocity profile propagate elastically as a shear wave, suggesting that in certain respects turbulent fluid behaves like a visco-elastic fluid in its response to shear, Finally, the relevance of these results to the phenomenon of the propagation of sharp turbulent-nonturbulent interfaces is discussed. (Author)

Descriptors :   (*TURBULENCE, SHEAR STRESSES), VELOCITY, PERTURBATION THEORY, FOURIER ANALYSIS, FLUID FLOW

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE