旋转部件复杂表面水滴撞击计算

为模拟旋转体结冰问题的过冷水滴运动及撞击过程，基于欧拉方法及单旋转坐标系模型，建立了三维旋转水滴运动模型，并提出了相应的数值求解方法。采用单旋转坐标系对空气及水滴两相流动过程进行处理，通过引入惯性力，将惯性系下的周期转动边界转换为定常流动边界；利用欧拉方法，使用单向耦合形式描述空气—水滴流场；在单旋转坐标系下，向控制方程内引入科里奥利加速度及牵连加速度，进行非惯性系下欧拉方程的修正，从而描述水滴运动过程；采用有限容积求解器对空气及水滴运动的控制方程组进行求解，通过引入源项定义单旋转坐标系下的惯性力，得到空气流场及水滴场的速度、体积分数分布，进而得到表面水滴撞击特性。采用上述方法对旋转帽罩与叶片模型进行算例分析，结果表明所建立的旋转水滴计算方法有效，对比静止状态表面的结果，旋转对帽罩的水滴撞击特性影响甚小，而对桨叶存在显著影响；由于帽罩具有中心对称的特性，因而旋转带来的切向速度变化对其水滴撞击特性影响不明显；桨叶表面水滴收集系数随旋转角速度增大而增大，同时收集系数在表面的分布会向迎风方向偏移，较大的角速度对应了更为显著的收集系数增幅与偏移现象。

Droplet impingement calculation on complex suface of rotating part

A three-dimensional water impingement model for rotating surface has been established and solved to simulate the process of supercooled water droplet impinging on ice protection surfaces,in which an Eularian method and a single rotating coordinate system were applied.With the single rotating coordinate system,the unsteady cyclically rotating boundary condition was simplified to a steady boundary by introducing the inertial forces;with the Eularian method,the air flow and water droplets flow field were depicted in a one-way coupled form;the Eularian control equations were adjusted in the non-inertial reference system by introducing the Coriolis acceleration and convected acceleration;then a finite volume solver was applied to solve the governing equations of air flow and droplet flow,in which the inertial forces were defined as the source terms of the momentum equation,and the results of velocity and volumetric fraction of air flow and droplet flow were obtained as well as the droplet collection efficiency.With the mentioned method,a rotating model of cowling and blades was simulated for a stationary case and at different rotational speeds.The results show that the rotation has significant influences on the water collection efficiency of the blades.The value of collection efficiency increases with increasing rotational velocity since droplet velocity normal to the surface increases due to the rotation,and the distribution curve shifts to the windward direction;the effect on the cowling is slight,and a distinguishable change of the impingement characteristic has not been caused by the change of the tangential velocity due to the axis-symmetric shape of the cowling.