| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 90 === The characteristics of the wake development of a finite wing under 3 different angles of attack were studied through experimental means. X-type hotwire anemometer was utilized to measure both the velocity of x and y direction of the three-dimensional wing-wake region. The aspect ratio of wing- model is 3. The results show that under the lift configuration, the wing-wake region can be divided into two regions in the spanwise direction. One is the two-dimensional wake region; the other is the tip-vortex affected region. In the two-dimension wake region, the wake centers of both α=50 and α=120 cases descend downstream under the effect of lifting surface downwash. The descend rates of both α=50 and α=120 are compared with theoretical values. Also the similarities that lie in mean velocity and r.m.s. velocity were observed. The development of maximum velocity defect Us was found to be proportional of x-1/2 which satisfies the evolution property of Us in turbulent plane wake.
In the tip-vortex affected region, the major velocity U was found to be 1.06 time of freestream velocity in the case of α=50 and 1.15 time of freestream velocity in the case of α=120. These phenomena are due to the suction effects of trailing vortex. In according to the downstream evolution of U contours, the development of trailing vortex could be divided into three stages: Growing, Saturation and Decaying.
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