飛機的失事原因大致可歸為三種因素：人為因素、機械因素及大氣因素。本文所要探討的積冰現象是大氣因素之一種，廣義的來說，積冰現象的成因，來自於空氣中之溫度低於冰點，而水滴以過冷水的型態出現，一旦撞擊到機翼，飛機即會逐漸產生結冰(積冰)的現象。面對飛機積冰的問題，吾人嘗試以計算流體力學來解決，可以分成三個步驟，第一步是網格點之生成，之後是流場解，最後是水滴軌跡方程式，根據流場解結果，以線性分析求解控制體積內流場之速度分布狀況，而水滴軌跡運動方程式是一時間與速度的函數，因此將可以預測若干時間後，水滴行進的方向與位置，並以此判斷出水滴是否撞擊機翼，俟積冰形成後，吾人再重新生成網格點、流場解與積冰，如此疊代運算，直到吾人所要求的時間為止。吾人之研究結果，積冰之成長趨勢相當符合，但是在部分區域，其積冰分佈與積冰厚度上有所誤差，而提出了改善之方法。 The three causes lead to Airplane crash that include human, mechanism,and the weather. Ice accretion, the topic we want to discuss in thisarticle, categorized into the weather. Broadly speaking, the reason ofice accretion was that temperature of air lower than freezing point,and droplet exist in supercooled water. When droplet impact onairfoil, it accretes. Bowyer's unstructured grids scheme is useful togenerated grids. It will generate grids automatically only by someinner or outer boundary points. It's easier to add or eliminatespecific grid, and thus more suitable for complex geometry, just likeice accretion shapes. The numerical scheme employed is the typicalRoe's scheme on Euler equations, and the 4th order Runge-Kutta timestepping method is also used to accelerate the convergence rate.Droplet motion equation and tell droplet if impact the airfoil or not,based on the results of solver. Apply ice accretion analysis, the iceaccretion shape come out. After that, the grids regenerate, so doflowfield and ice accretion. It lasted repeatly until the time we set.The ice accretion results show that the trend of ice accretion iscorrect, but ice accretion profile and ice accretion thickness is notas good as we expected. Several improvements have been presented.
