热力学效应对水翼云空化非定常特性的影响

Influence of thermodynamic effects on cloud cavitation dynamics characteristics around 3D hydrofoil

为了探究热力学效应对绕翼型云状空化非定常特性的影响,应用数值模拟的方法,分别从翼型周围温度场、空泡半径、当地空化数的角度分析了不同水温下热力学效应对空化发展的影响.依据模型试验使用的物理模型建模,采用考虑热力学效应的空化模型和基于密度修正的湍流模型(DCM)对攻角α0=8°的水翼进行非定常云状空泡的数值求解,计算得到的空泡形态与试验结果吻合度较高.空化发生时,蒸发吸热使空泡内部温度降低,水体饱和蒸汽压力下降,空化的发展被抑制,最终附着空泡区域变小、变薄.同时,随着水温的升高,空泡半径减小,空泡扩散加剧,空化区域更加模糊.由于流场温度变化会导致流体物理性质的改变,因此采用考虑温度变化的当地空化数σ(T)可以更直观地反映流场温度变化对空化发展阶段的影响.

In order to investigate the thermodynamic effects on cloud cavitation dynamic characteristics,the accordance of numerical simulation with experiment was first validated,and then the thermodyna-mic effects on cavitation were investigated from aspects of temperature field,bubble radius and local cavitation number at different water temperatures.Based on the physical model of experiments,the simulation model was established,and the thermodynamic cavitation model and density corrected model(DCM)were applied to this cloud cavitation simulation around a hydrofoil with an angle attack of 8°.The results indicate that the calculated cavity structure coincides with the experimental results.Evaporation cooling leads to temperature drop inside the cavity,then saturation pressure decreases which suppresses the development of cavitation,and finally the attached cavity regions become smaller and thinner.Moreover,bubble radius decreases with the increase of free-stream temperature,which results in strong diffusion of bubbles and mistier cavity regions.Local cavitation number can directly reflect the effects of flow field temperature variation on the development stage of cavitation since the fluid physical properties change with temperatures.