基于自由尾迹分析的直升机旋翼下洗流场计算方法

A Calculating Method of Helicopter Rotor Downwash Flowfield Based on Free Wake Analysis

建立一个包含机身影响的旋翼自由尾迹分析模型,以用于实际直升机旋翼和机身组合时的旋翼诱导速度场计算,为火箭导弹发射提供一个旋翼下洗流场计算方法。在该模型中,使用一个卷起桨尖涡模拟尾迹的影响,采用二阶升力线理论代替桨叶的作用,并采用一个源面元模型计入机身对旋翼尾迹的诱导和堵塞等影响;分别以美国佐治亚理工学院和马里兰大学所采用的旋翼/机身组合模型为算例,对多种状态进行计算;将计算的旋翼流场定常和非定常速度与可得到的实验结果进行对比,表明了本方法的有效性。

A rotor free-wake model including fuselage effects was established to predict the rotor induced velocity flowfield of a real helicopter which has a combined rotor and fuselage configuration, and to provide a calculating method of the downwash flowfield for airborne rocket or missile fire. In this model, a rolled-up tip vortex model was used to simulate the effects of the wake on the flowfield, a second-order lifting line model was adopted to represent the effects of the blade on the flowfield and a source panel model was included to take into account the induced and obstructed effects of the fuselage on the rotor wake. Based upon the flee-wake model, numerical examples for a 4-blade combined rotor and fuselage configuration of University of Maryland and a 2-blade combined rotor and fuselage configuration of the Georgia Tech were given. The computations of steady and unsteady flow velocities were carried out. The comparison between calculated result and available experimental data shows the effectiveness of the method.