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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

COMPUTATION OF FLOW AROUND A NACA 0015 AEROFOIL WITH ZNMF JET CONTROL: POTENTIAL SAVINGS OF AN UNSTRUCTURED MESH?

pages 1281-1286
DOI: 10.1615/TSFP6.2040
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摘要

The flow around a NACA 0015 aerofoil with a zero-net-mass-flux jets (ZNMF) located at the leading edge of the aerofoil is simulated using Large Eddy Simulation (LES). An incidence angle of 18° is used such that without flow control, the flow exhibits laminar separation from the tip of the aerofoil and an associated loss of lift. The oscillating ZNMF jet is designed to introduce small scale structures into the boundary layer at the mouth of the jet to breakup the larger, more stable low speed structures. These long thin structures are perturbed to the point that they become unstable and turbulent flow ensues, where higher momentum enables the flow to maintain attachment around the tip and suction surface of the aerofoil. This is a complex three dimensional flow which requires fine temporal and spatial resolution and in this paper, LES are undertaken using the Smagorinsky subgrid scale model on both structured and unstructured meshes of around 10M and 2M points respectively. It is found that while the structured mesh is able to capture correctly this flow control mechanism for some periods of the cycle, there appear to be difficulties, in spite of employing necessary resolution requirements. Several causal factors are identified for ongoing study. The same calculation run on an unstructured mesh of 80% fewer cells appears to be able to maintain the controlled state of the flow previously observed in experiment, but the computation on the unstructured mesh is in fact 'assisted' by the influence of numerical noise generated upstream of the aerofoil at the non-conformal interface of grid cells.

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