具匿蹤性能之飛行器低速高攻角氣動力特性之水洞試驗研究

本文利用匿蹤外型之飛行器模型設計方法，探討靜態與動態條件之水洞高攻角流場觀測及氣動力特性。鈍前緣匿蹤模型，無側滑角之靜態流場觀測發現，左右渦流潰散點為對稱位置，攻角α=20°，前機身渦漩分裂成雙流線。動態俯仰過程，低攻角時左右兩側渦流延遲崩散並位置呈不對稱搖滾現象。W型翼尾緣，發展向翼面上方第三維旋轉之剪力流層，較靜態時完整。動態俯仰速率變大，渦漩發生旋轉時間延後，崩散點往後移。尖前緣模型靜態流場觀測中，前機身並無分流產生。動態無側滑角之攻角上仰流場觀測，前機身渦流往翼面前緣移動趨勢，模型尾部無形成與機身之三維效應有關之尾流渦漩。動態測力試驗，鈍前緣模型之最大正向力係數和失速攻角，隨上仰速率提高而增加，證明渦流遲滯崩散現象，得氣動力特性較佳之論點。下俯過程降低攻角擺動速率，氣動力表現才接近靜態試驗。

關鍵字

匿蹤；水洞；俯仰過程；搖滾現象

並列摘要

Based on the concept of design for stealth, this paper tries to probe into flow visualization and aerodynamic characteristics of stealth craft models at high angles of attack under static and dynamic conditions in a water tunnel. For the models with blunt leading edges and a stealth shape, results of flow visualization under the static conditions show that the vortex breakdown points are symmetrical at 0° sideslip angle, and that the vortices over the forebody will be separated into two stream lines at the angle of attack α=20°. Under the dynamic condition, hysteretic breakdown of vortices occurs and the position of vortex breakdown is asymmetrical and wing rock to happen at low angles of attack. For models with W-shaped tails, the results show that the shear layers rotating in three dimensions over the wings are more complete then the static condition. Under the dynamic condition, vortices begin to rotate in later time and the breakdown points tend to move backward as the pitch frequencies increase. On static flow visualization, there is no flow separation over the forebody while the results of dynamic flow visualization for models with sharp leading edges show that the vortices over the forebody decrease and tend to move towards the leading edge of the wing as the angles of attack increase, if the sideslip angle is 0°. No wake vortices involving three-dimensional effect of the body are found over the tails. The results of dynamometric experiments show that for models with blunt leading edges, their maximum normal force coefficient and stalling angle of attack increase with pitch-up velocities, justifying the argument that there will be hysteresis in vortex breakdown and better aerodynamic characteristics. In the pitch-down process, the aerodynamic performance cannot approach that obtained in static experiments before the pitch angular velocities are reduced.

並列關鍵字

Stealth ； Water tunnel ； Pitch process ； Wing rock

國際替代計量

具匿蹤性能之飛行器低速高攻角氣動力特性之水洞試驗研究

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