The Role of Atmospheric Turbulence on Cloud Droplet Distribution and Droplet Impaction on an Airfoil

Abstract We conduct turbulence-informed Euler–Lagrange simulations of droplet-laden flow to examine the effects of atmospheric turbulence on droplet impingement characteristics on a NACA 0012 airfoil. We implement statistical overloading, whereby we inject millions of droplets, ranging in diameter from 1 to 160 microns, upstream of the airfoil at an average streamwise velocity of 120 m/s. Within a fraction of a second, these droplets would have either impinged on the airfoil or continued downstream. While the incoming air flow is maintained uniform, droplet injection is informed by ambient turbulence, affecting both the droplet velocity distribution as well as the size-dependent preferential concentration (inertial clustering) of the droplets over space. The droplet injection location and velocity components are obtained from a separate high-fidelity, droplet-laden simulation of isotropic turbulence. We extract the droplet collection efficiency, impingement velocity magnitude, and impingement orientation along the airfoil surface and compare the results against a nonturbulent inflow, where droplet injection is uniform. The collection efficiency remains largely unaffected by turbulence across all droplet sizes. In contrast, impingement velocity is observed to increase for the larger droplets in a turbulent flow. The effect of ambient turbulence is also observed in the impingement angle statistics, with increasing influence for the larger droplets.