- 學位論文
機翼釋放多個具鰭片彈體非黏滯流場數值模擬
Numerical Simulations of Inviscid Flows over Multiple Stores with Fins Released from a Wing
摘要
在飛機與彈體進行分離時，將彈體順利地擊中目標物雖然重要，但如果所釋放之彈體撞擊到母體本身而導致損壞這並不是我們想看到的，所以能將彈體順利分離也是值得關注的一環，因此本文使用商用軟體ESI CFD FASTRAN 研究非黏滯流通過機翼釋放多個具鰭片彈體之參數效應，在卡式座標下求解三維非穩態Euler方程式，採用多區塊Chimera網格系統，不同區塊網格系統重疊部分相互自動傳遞資訊，為驗證本文計算的正確性，單顆彈體重心瞬間軌跡與翻滾、俯仰、偏航角度、瞬間速度、角速度計算結果與實驗值比較後，趨勢分佈非常接近，進而增加彈體數量，並改變雙彈前施力倍增而後施力不變與雙彈前後施力倍增探討分離彈體非穩態物理現象。釋放三彈的中間彈體會使原本的中間彈體向後移動量與向翼尖移動量增加；翻滾角以駕駛者觀點來看先逆時針旋轉後轉順時針，最後逆時針旋轉，俯仰角度增加，偏航角最大值增加且出現時間提前；彈體向後速度、向翼尖移動速度增加；翻滾率、俯仰率與偏航率最大值增加，俯仰率最小值變小。
並列摘要
As for the release of store from the aircraft, it is important that the target is hit and destroyed by the stores. However, it will not be allowed and expected if the mother aircraft is hit and damaged by the store it releases. Consequently, smooth separation of store and aircraft is also concerned. In this article, the commercial software ESI CFD FASTRAN is applied to study the parametric effects of inviscid flows around multiple stores with fins released from a wing. The three-dimensional, unsteady Euler equations are solved in the Cartesian coordinate. The Chimera multi-block grid system is utilized, and grid communication among multiple blocks is automatically implemented. To evaluate the accuracy of the present calculation, the calculated one-store instantaneous trajectory of center of gravity of store, angles of roll, pitch and yaw, velocity and angular rate are compared with those of experimental data. The satisfactory agreement is achieved. Then, the number of store is increased. As far as the two-store is concerned, two parameters are carried out to investigate the unsteady phenomena of separated stores. The first one is to increase the forward ejector force and keep rearward ejector force invariant, while the other one is to increase not only the forward ejector force but also the rearward ejector force. Comparing the middle store of three-store calculation with that of original one-store calculation, both backward movement and movement toward wingtip are increased. According to the pilot's view, the middle store in rotated counterclockwise first and counterclockwise follow up. Eventually, it is re-rotated counterclockwise approaching the end of calculation. The angle of pitch of middle store is enlarged. The maximum angle of yaw is increased and its time is shortened. Both backward velocity and lateral velocity toward wingtip are increased. The maximum values of rolling rate, pitching rate and yawing rate are increased, whereas the minimum value of pitching rate is decreased.