| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 100 === The performance of a two-dimensional thrust-vectoring nozzle has been evaluated by the numerical simulation of its internal flow in the present study. The FLUENT software has been used in the numerical simulation, adopting the SST k-ω turbulent model. The numerical simulation has been validated by the available experimental results. The objective of the present study is to simulate the nozzle flow variation during the flapping process, and investigate the differences of the thrust and flap’s stress between the dynamic and steady-state operations. It has been found that the exhaust average velocity of the dynamic operation is lower than that of the steady-state one, reducing its thrust. When the pitch-flap swings up to 30 degrees, the dynamic stress of the upper flap reduces approximately by 27% and that of the nether flap decrease approximately by 14% in comparison to that of the steady-state operation by simplified two-dimensional simulation. However, for a complete three-dimensional analysis, the dynamic stress of the upper flap decreases approximately by 15%, and that of the nether flap decreases approximately by 9% in comparison to that of the steady-state operation. When the yaw-flap swings right to 15 degrees, the dynamic stress of the right flap decreases approximately by 23%, and that of the left flap decreases approximately by 2% in comparison to that of the steady-state operation. The present results show that the complete three-dimensional dynamic simulation is in better agreement with the actual situation than the steady simulation. The thrust efficiency is 83.41% before the flap swings. The thrust efficiency is down to 74.75%, when the pitch-flap swings up to 30 degrees. The thrust efficiency is down to 82.44% when the yaw-flap swings right to 15 degrees.
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