Berlin 2012 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 22: Posters I

DY 22.23: Poster

Wednesday, March 28, 2012, 17:00–19:00, Poster A

DDES Simulation of the turbulent wake of a fractal square grid — Hannes Hochstein¹, Stefan Weytemeier¹, Bernhard Stoevesandt², and •Joachim Peinke¹ — ¹ForWind - Center for Wind Energy Research, Institute of Physics, University of Oldenburg — ²IWES - Fraunhofer Institute for Wind Energy and Energy Systems

The wake of the flow through a fractal square grid was simulated, using the open-source CFD code OpenFOAM. In 2007, Hurst published an article about fractal grids. Those grids produce turbulence on a range of different scales, which influent each other, and have very different properties than all previously documented turbulent flows and is even considered to define a new class of turbulence. This turbulence is able to keep its homogenity and isotropy further downstream than classical, one-scale-generated turbulence. This, and the fact that real wind energy converters are exposed to multi-scale turbulence, makes the fractal generated turbulence interesting as inflow boundary condition for a CFD simulation of a wind energy converter.

The simulation was carried out using the delayed detached eddy simulation (DDES) of OpenFOAM. The goal of the work was to simulate the governing anomalous turbulence properties qualitively, to maintain their good usability as a inflow boundary condition. The first results of the simulation were compared with similar wind tunnel experiment data, which showed a pretty good agreement of the main turbulence properties like turbulence intensity, skewness and flatness of the flow velocity.