结冰风洞中过冷大水滴云雾演化特性数值研究

为明晰结冰风洞中过冷大水滴（SLD）云雾演化特性，发展了基于欧拉法的SLD液滴运动、传热和传质耦合计算方法，针对3 m×2 m结冰风洞主试验段水平收缩构型，分析了SLD云雾沉降收缩特性、动量平衡特性和热平衡特性，探索了液滴变形破碎的影响，评估了构型出口处SLD液滴动量平衡和热平衡状态。研究结果表明：直径超过250 μm的SLD液滴在构型内会发生显著形变，液滴尺寸越大则变形程度越强，尤其在160 m/s工况下，当液滴直径超过750 μm后，SLD液滴甚至会发生破碎；液滴变形破碎效应会增大液滴加速度和液滴温度下降率，促使SLD液滴趋近动量平衡和热平衡状态；SLD云雾（最大液滴直径小于1 000 μm）在构型出口处会出现显著的粒径浓度分层、动量分层和热分层现象，其中直径小于100 μm的小尺寸液滴速度快、温度低且不断凝结，趋于平衡态，但直径超过500 μm的大尺寸SLD液滴速度慢、温度高且不断蒸发，则显著偏离平衡态；增大试验段气流速度尽管会减弱SLD云雾粒径浓度分层程度，但会增强动量分层和热分层程度，尤其在160 m/s工况下，SLD云雾会均匀分布在构型出口中心区域内（-0.75 m < Y < 0.75 m且-0.5 m < Z < 0.5 m），与其平衡态间的最大速度差和温度差将分别超过18 m/s和20℃。

Numerical study of supercooled large droplet cloud evolution characteristics in icing wind tunnel

In order to understand the Supercooled Large Droplet (SLD) cloud evolution characteristics in icing wind tunnels, a method based on Eulerian theory is developed to simulate SLD cloud flows coupling of momentum, mass and heat transfer. Using this method, the evolution of SLD cloud is investigated for the horizonal contraction configuration of the main section in a 3 m×2 m icing wind tunnel. The SLD cloud evolution characteristics, including cloud sinking and contraction, cloud momentum equilibrium and cloud thermal equilibrium, are analyzed. The effects of droplet deformation and breakup on the SLD mechanical equilibrium characteristic are explored. The states of cloud momentum equilibrium and thermal equilibrium in the main test section are evaluated. Results show that SLD droplets with diameter larger than 250 μm would experience significant deformation in the configuration. The increased droplet size could enhance the degree of deformation. Particularly at the test section velocity of 160 m/s, SLD droplets with the diameter larger than 750 μm would break up. Then the effects of droplet deformation and breakup could increase the rates of droplet acceleration and temperature reduction, so that the SLD droplets would approach the momentum and thermal equilibrium states. The SLD cloud with the maximum diameter of 1000 μm shows size and concentration stratification, momentum stratification and thermal stratification at the configuration outlet. In the SLD cloud, the small droplets with diameter smaller than 100 μm would reach the equilibrium states with higher speed, lower temperature and constant condensation. However, large SLD droplets with diameter larger than 500 μm would deviate from equilibrium states significantly with lower speed, higher temperature and constant evaporation. Increased test section velocity could reduce the degree of SLD cloud concentration stratification, but enhance the degree of momentum and thermal stratification. In particular, in the condition with the test section of 160 m/s, the SLD cloud will be uniform in the central area of the outlet (almost -0.75 m < Y < 0.75 m and -0.5 m < Z < 0.5 m), but the maximum velocity difference and temperature difference compared with the equilibrium states are higher than 18 m/s and 20 ℃, respectively.