Abo Bibliothek: Guest
Fifth International Symposium on Turbulence and Shear Flow Phenomena
August, 27-29, 2007, Technische Universität München, Munich, Germany

DOI: 10.1615/TSFP5

COMPRESSIBLE TURBULENCE

pages 11-20
DOI: 10.1615/TSFP5.20
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ABSTRAKT

Density (temperature) variation and a dilatational velocity component are hallmarks of compressible turbulence. After an introduction to turbulent flow examples where compressibility is important, attention is restricted to high-speed flows. The turbulent Mach number, Mt, can be significantly smaller than unity even in supersonic flows. Different approaches of low-Mt asymptotic analysis of the velocity and thermodynamic fluctuations are discussed. Compressibility effects are discussed through a review of four specific flows: isotropic turbulence, uniform shear flow, mixing layer and supersonic channel flow. The first three do not have a mean gradient in density or temperature. The magnitude of the dilatational component in direct simulations of isotropic turbulence is dependent on both initial conditions and turbulent Mach number, Mt. An acoustic mode with equipartition between kinetic and potential energies is observed. Turbulence in uniform shear flow and the mixing layer is inhibited with increasing Mach number. The pressure fluctuations play a particularly important role in this stabilizing effect and the gradient Mach number, Mg, is the relevant parameter that determines this effect. Supersonic channel flow has large gradients in mean properties that affect the log law in mean velocity as well as inner and outer scalings of the turbulent stresses. Some of the effects can be captured by appropriate weighting with local values of mean density and viscosity. However, there is an additional effect of pressure fluctuations on the Reynolds stresses which cannot be represented by such weighting.

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