| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 107 === This study is aimed detecting the influence of an intrusive anemometer on cylindrical wake flow measurements by comparing the turbulence statistics between two computational domains, a domain with cylinder and a domain with a cylinder and an intrusive hot-wire anemometer (HWA). The numerical results of the domain with only the cylinder and the HWA experimental results are compared to verify the credibility of the numerical method. A numerical simulation is performed with the LES method and a sub-grid model of the dynamic Smagorinsky model (DSM) by imposing the measured boundary conditions, mainly for the near wake region for two cases, Re = 3856 and Re = 9959.
The strategy for setting the mesh size is dependent on the estimated Tylor micro scale obtained from the experimental results for the purpose of approaching the physical interpretation of the LES method. Based on the estimated Tylor micro scale, different mesh densities were set up in the shear-layer region for mesh identification, and the results for the recirculation bubble length using this method were found to be close to each mesh density in both cases. The numerical results of the domain with the cylinder were found to be in good agreement with the experimental results at x/d = 4 ~ 10.
The numerical results for the two different domains in terms of the stream-wise mean velocity value were obviously different. At the very near wake region(x/d = 2), the deviation in the value was 13.5% for Re = 3865 and 9.8% for Re = 9959. The deviation in the stream-wise velocity gradually decreased in the downstream region, where the deviation in stream-wise velocity value was 4.7% at x = 6d for Re = 3856.
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