| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 102 === SUMMARY
This paper examines experimentally the wake characteristics of a model wind turbine and a porous disk in turbulent boundary layers, respectively. The experiments simulating the atmospheric boundary layer flow condition were conducted in an environmental wind tunnel. Under the experimental condition, two boundary layers of different thickness, about 5.5D and 1.85D, where D denotes the diameter of model blade. The velocity measurements were based on the hot-wire anemometer. Hilbert Huang Transform had been used to analysis the turbulent characteristics. The result shows that velocity deficit was decrease in the thicker boundary layer, and had less turbulent-increase effect in the thicker boundary layer. The relationship between velocity deficit and turbulence intensity increase were in direct proportion, but porous disk shows they were in reverse proportion. The turbulent integral time scale shows large turbulent eddies dominated the turbulence in the thicker boundary layer, and small turbulent eddies dominated the turbulence in the thinner boundary layer. The strouhal number from the main turbulent frequency was consistent with the results of turbulent integral time scale. The wake flow development in the thicker boundary layer appear to be dominated by the large scale eddies in the boundary layer, whereas in the thinner boundary layer, the wake flow development relies on the turbulent eddies generated by the model.
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