| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 90 === ABSTRACT
Experimental Study of Ground Effect on Finite-Wing Wake Flow Development
Student: Miss Tzu-Wei Lee
Advisor: Prof. Fei-Bin Hsiao
This thesis studies the flowfield characteristics in finite wing wake flow under the ground effect. The wing mode having the NACA0012 airfoil section of AR=6 is used to investigate the ground effect by changing the height between the wing surface to the wind tunnel wall. The freestream velocity is operated at 20m/s with the corresponding Reynolds number of 8.9×104 based on the wing chord. The wing mode is maintained at AoA=12°throughout the experiments. The finite-wing wake development under the ground effect is obtained by streamwise and transverse information, which was measured by a cross-type hot wire anemometer. Experimental results indicate that flow development with the ground effect can be divided into two ranges. In the first range, the wake is descending with downstream which was caused due to the downwash effect from the wing model; while in the second range, the wake is strongly affected by the existence of the wall and the descending rate gets slower than that in the first range.
It is observed as well that the secondary vortex in the wake will interact with the tip-vortex and both will merge with each other into the wake region eventually. However, the wake development motion can be cleanly seen by means of the mean velocity contour with the downstream.
Moreover, an additional experiment of flow control was presented in this study. It was conducted by the original model with an attachment of trailing-edge free flap. The results of this experiment show that the free flap excitation at trailing edge can effectively destroy the wake structures and no clear shedding vortices were seen in the downstream of the wake flow.
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