A Lagrangian-Eulerian scheme for flow around an airfoil in rain

In the interest of assessing airfoil performance in rain, a Lagrangian particle tracking algorithm for a general body-fitted co-ordinate system has been developed and linked with a thin layer incompressible Navier-Stokes code. Non-deforming spherical particles are tracked through the two-dimensional, incompressible air flow field surrounding a NACA 64-210 airfoil section. Each tracked particle represents a distribution of raindrops. Impacts on the airfoil surface and the resulting splashback are modeled, and the steady state fluid field and droplet distribution are determined utilizing an iterative, two-way momentum coupled approach. Details of the splashback effect on the boundary layer are examined. A 1-2° rain-induced decrease in stall angle of attack is predicted.