Numerical simulation of airfoil aerodynamic performance under the coupling effects of heavy rain and ice accretion

It has been widely investigated before that both heavy rain and icing conditions can cause severe aerodynamic performance penalties to aircraft in flight; however, aircraft aerodynamics in the presence of both heavy rain and ice accretion has been little explored so far. In this article, a numerical simulation is performed to study the aerodynamic performance of an iced NACA 0012 airfoil in simulated heavy rain condition. A two-way momentum-coupled Eulerian-Lagrangian two-phase flow approach is developed to simulate raindrop trajectories in the airflow field. The analysis indicates that both rain and ice can separately cause severe aerodynamic performance degradation to the airfoil at most angles of attack of interest. In the presence of both ice and rain, a further severe aerodynamic penalty can be produced by rain based on the ice-induced aerodynamic performance degradation. Premature boundary-layer separation and boundary-layer momentum losses by splashed-back raindrops are also observed.