计入离心力影响的直升机旋翼翼型结冰数值模拟

Numerical simulation of ice accretion on rotor airfoil of helicopter considering effects of centrifugal force

建立了一套计入离心力影响的直升机旋翼翼型结冰的数值模拟方法.首先生成围绕翼型的贴体正交网格,然后用Navier-Stokes(N-S)方程求解黏性绕流流场.在此基础上,利用拉格朗日法建立水滴运动方程.其中,为提高计算效率,提出了结合位移矢量的水滴所处单元寻觅方法.最后,结合桨叶工作特点,发展了一种计入离心力影响的三维结冰模型.通过与桨叶结冰实验的对比,验证了本文结冰预测方法的可靠性.对比常规结冰模型,桨叶结冰量减少22.3%;若考虑桨叶的挥舞运动影响,桨叶结冰量进一步减少,表明了离心力及桨叶运动在结冰数值模拟中的重要性.通过不同剖面间的结冰量和冰形对比,分析并获得了桨叶结冰特征.结果表明离心力的影响程度随径向位移的增加而增加,下翼面结冰量随挥舞角的增加而减少.

Considering the effects of centrifugal force, a method of numerical simulation for ice accretion on rotor airfoil of helicopter was established. Firstly, the body-fitted and body-orthogonal grids around an airfoil were generated and the viscosity flowfield around rotor airfoil was solved by Navier-Stokes （N-S） equations. Based on the solution of flowfield and Lagrange method, the equations of water droplets motion were established. Then, in order to improve the computational efficiency in searching the position of the water droplet, the method combined with the displacement vector was presented. Finally, in combination with the characteristics of blade motion, a three-dimensional ice accretion model considering the effects of the centrifugal force was presented. The comparison between the calculated results and experimental data indicates that the current approach can effectively simulate the ice accretion on airfoil of blade. Compared with the results of conventional ice accretion model, the amount of ice accretion was reduced by 22.3G. Considering the blade flapping motion, the amount of ice accretion was reduced more. As a result, the importance of the centrifugal force and blade motion in blade numerical simulation of ice accretion was pointed out. Comparing the ice shape and amount of the different sections of blade, the ice accretion characteristics of blade were discussed and analyzed. The results show that the effects of the centrifugal force increase with the increasing radial displacement, and the amount of ice accretion on the rotor lower surface decreases with the increase of the flapping angle.