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Turbulence and Shear Flow Phenomena -1 First International Symposium

ISBN:
1-56700-135-1 (Print)

NEAR WALL BEHAVIOUR OF STATISTICAL PROPERTIES IN TURBULENT FLOWS

M. Fischer
Lehrstuhl fur Stromungsmechanik, University of Erlangen-Nurnberg, Cauerstr. 91058 Erlangen, Germany

Franz Durst
FMP TECHNOLOGY GMBH, Am Weichselgarten 34, 91058 Erlangen, Germany

Jovan Jovanovic
Institute of Fluid Mechanics Friedrich-Alexander University Erlangen-Nuremberg Cauerstrasse 4, D-91058 Erlangen, Germany

Abstract

The continuity and momentum equations do not imply a Reynolds number dependence of turbulence data when wall variables are used for normalization. The influence of the Reynolds number on turbulence quantities results from the imposed boundary conditions at the edge of a boundary layer or on the axis of a channel or a pipe flow. This has often been assumed not to affect the near wall region. However, experimental and numerical results show a Reynolds number dependence of turbulence intensity very close to the wall. It results from the behaviour of a sink term in the dissipation rate equation which shows a Reynolds number dependence in the limit of two-component two-dimensional turbulence as it exists close to walls. Away from the near-wall region the Reynolds number dependence originates from the streamwise pressure gradient which enters into the equations for the turbulent kinetic energy and turbulent dissipation rate through the gradient production processes. The low-Reynolds number effects in turbulent channel flow were investigated experimentally using the LDA measuring technique. A new method was applied to eliminate the influence of the limited spatial resolution of the measuring technique.