Numerical simulation of droplet deformation in uniform airflow

Aircraft flying in icing conditions will encounter supercooled water droplets. These droplets can deform due to the interaction with the airflow, leading to the change of the droplet trajectory. The phase field method is applied to capture the droplet morphology during the droplet deformation and movement in a uniform airflow. Combined with the lattice Boltzmann flux solver, the flow field of the droplet-air two-phase flow is simulated. Time evolutions of the droplet aspect ratio and the accelerations under different We numbers, Oh numbers, and ambient temperatures are compared. Flow development in the wake region of the droplet is analyzed, and the dynamic behavior of the water droplet in the deformation process is revealed. A drag model of the droplet in the airflow is proposed, and the droplet impact characteristics are simulated and compared with experimental data to validate the accuracy of the drag model. It is found that, the droplet has the characteristics of alternating axial compression and radial compression, and the maximum aspect ratio in each axial compression decreases with time. When the water droplet is close to breakup, the edge is thicker while the center gradually becomes thinner until the breakup. Low ambient temperature affects the droplet deformation amplitude but has little effect on the movement of the droplet. Moreover, the proposed droplet drag model can achieve higher accuracy for the droplet impact characteristics calculation, which can provide a more accurate input condition for subsequent aircraft icing prediction.