不穩定波對翼形轉移點之數值研究

Abstract

The purpose of the paper is stressed on the numerical method in solving the stability equation, and the prediction of the transition piont of airfoils by employing the e �� nmethod. The Euler Maclaurin formula is applied to formulate a high-accuracy numerical finite difference scheme for both nonsimilar boundary layer equations and the stability equations. The numerical results show that the location of the transition piont moves to the downstream as the thickness of the airfoil increases, and separating flow is easier to occur than the turbulent flow at high angles for the same airfoil. The transition point occurs closer to the leading edge at both higher disturbance frequency and higher Reynolds number. However, the further increase of the disturbance frequency reverses the trend and cause the transition point move toward the trailing edge. 本論文主要目的乃是以數值求解穩定方程式以得到流場不穩定波之位置成長率， 並引用 e �騍z論以為預估二維翼形轉移點位置。文中並概述如何以 Euler-Maclaurin 公式 建立一高準確度及高效率之四階準確度有限差分數值方法，以為求解非相似邊界層方程式及 穩定方程式。 本文計算結果顯示，轉移點位置隨著翼形厚度增加而有往翼後端移動趨勢，而同一翼形在高 攻角狀況，分離流場較紊流流場易發生：高干擾頻率及高雷諾數將使穩定界限點愈往翼前端 移動，導致轉移點位置隨著干擾頻率增大，及雷諾數增加而愈往翼前端點移動。然隨著干擾 頻率之繼續增大，轉移點位置有往翼後端迅移動趨勢。