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Second Symposium on Turbulence and Shear Flow Phenomena
June, 27-29, 2001, KTH, Stockholm, Sweden

DOI: 10.1615/TSFP2

DIRECT NUMERICAL SIMULATION OF INTERACTIONS BETWEEN A MIXING LAYER AND A WAKE AROUND A CYLINDER

pages 125-130
DOI: 10.1615/TSFP2.1840
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摘要

Direct Numerical Simulation of turbulent flows around a cylinder are performed using the virtual boundary technique to modelize the presence of the obstacle. Such a method consists in the imposition of a no-slip boundary condition within the flow field by the use of a specific forcing term added to the momentum equation. In this paper, we consider the flow around a single cylinder with upstream conditions corresponding to a constant velocity flow or to a mixing layer flow. In the first case, the usual one, common features of the cylinder wake dynamics are recovered (three-dimensional vortex shedding) showing the ability of the virtual boundary technique (coupled to an accurate finite difference method) to take obstacles into account realistically despite the use of a simple Cartesian grid. The second case can be basically decomposed in three main flows : a low-speed wake, a high-speed wake and a mixing layer flow. It is found that interaction mechanisms between these three flows are predominant. The cylinder induces a strong distortion on the spatial development of the mixing layer. Analysis of the mean flow shows the presence of strong upward and downward streams respectively in front of and behind the cylinder. In the regions of slow/fast wakes, vortex shedding are found at frequencies which seem to be linked. Vortex dynamics analysis shows that large scale eddies are the key element of the interaction mechanisms.

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