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Based on Patent application DE 198 22 125.8-52, we present a technical description of a new temporal and spatial high resolving anemometer for gas and liquid flows. The measurement principle is based on the technique of an atomic force microscope where microstructured cantilevers are used to detect extreme small forces. We show the sensor as a small compact unit and present first measurements and characterizations.

By using small deviations from the stationary solution of the Navier-Stokes equation, the problem of linear instability of a plane submerged subsonic jet is considered. In the approximation of weak divergence of the jet, this problem reduces to a linear not self-adjoint boundary value problem with a given behavior of the variables at large values of the transversal coordinate. The solution of this boundary value problem allow us to calculate the gain factor and the phase velocity of hydrodynamical waves as functions of frequency and of distance from the nozzle. We have found that the dependence of the gain factor on the frequency has a resonant character. As the distance from the nozzle increases, the dependence of the gain factor on the frequency becomes more narrow and the maximum of that shifts into the small frequency region. Hence, the hydrodynamical waves become more and more coherent. The obtained results are in good agreement with experimental data.

Direct numerical simulations (DNS) of turbulent Rayleigh-Bénard convection for a liquid metal with = 0.025 are used to perform statistical analysis, in particular to evaluate the turbulent diffusion term in the temperature variance equation. These results are compered with DNS based predictions by a standard model of the turbulent diffusion term in the temperature variance equation and by a model which was recently developed by the authors.

A short review of numerical simulation approaches for transitional and turbulent shear flows is presented. Some results using large-eddy simulation (LES) are for canonical turbulent and transitional flows obtained with different subgrid-scale (SGS) models such as a variant of the approximate deconvolution (ADM) and high-pass-filtered (HPF) eddy-viscosity model. Special focus is the LES of transition in incompressible flow.

It is well-known that heat transport in Rayleigh-Bénard convection, which can be expressed by the Nusselt number , scales with the Rayleigh number [1]–[2]. Chavanne compared numerous experimental results [3] and showed that the obtained scaling law vs. depends on the aspect ratio = / (where denotes the radius and — the height of the cylinder) and the Prandtl number = /. While most experiments were conducted in a cylindrical confinement for practical reasons, the majority of the so far performed numerical simulations were conducted for planar configurations

Probability density functions (PDF) present seducing features for modelling turbulent reactive flows: they carry a detailed one-point statistical information and allow to treat chemical source terms exactly. But to be able to take full advantage of those modelling abilities, it is first necessary to possess an efficient numerical method to solve PDF equations.

In this article, this issue is adressed in the frame of Eulerian Monte Carlo methods: stochastic partial differential equations which are stochastically equivalent to the PDF equations are proposed and applied to the calculation of the PDF of a reactive scalar.

Direct numerical simulations (DNS) of turbulent supersonic channel flow of air at Reynolds numbers ranging from = 180 to 560 and Mach numbers ranging from = 0.3 to 3.0 have been performed. The DNS data are used to explain the reduction of the pressure-correlation terms due to compressibility, using a Green’s function approach.