| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 98 === The NACA 0012 finite airfoils with various sweep angles were examined for exploring the effects of angle of attack, sweep angle and Reynolds number on the wing-junction flow. Furthermore, the influences of upstream-floor roughness and turbulence intensity (T.I.) on the wing-junction flow were included. The smoke-wire scheme was utilized to visualize the flow configurations at low Reynolds numbers. The smoke-streak flow patterns were classified into two characteristic modes — horseshoe-vortex mode and non-horseshoe-vortex mode. Moreover, the horseshoe-vortex patterns can be further categorized as the junction-vortex mode and non-junction-vortex mode. In addition, the particle-image velocimeter (PIV) was applied to measure the flow-velocity fields and calculate the flow vorticity. The experimental results reveals that the vortex length increased and the vorticity decreased with an increase of attack angle while the Reynolds numbers and sweep angles were fixed. However, the straight wing has the maximum vorticity while the Reynolds numbers and angle of attack are constant. In addition, a high vortex length induces a low vorticity for a swept-back wing and a low vortex length induces a low vorticity for a swept-forward wing. Specifically, various sandpapers and meshes were attached in the upstream of wing junction for probing their effects on flow structures. For a straight wing, the vorticity of unmeshed upstream flow (T.I. = 0.9%) is 37% lower than that of #3 meshed upstream flow (T.I. = 2.9%). Moreover, for the #4 meshed upstream flow (T.I. = 3.5%), the junction vortex disappears.
Keywords: wing-junction flow, vorticity contour, swept-back wing, swept-forward wing
|
|---|
