Collision Fluctuations of Lucky Droplets with Superdroplets

Abstract It was previously shown that the superdroplet algorithm for modeling collision–coalescence process can faithfully represent mean droplet growth in turbulent clouds. An open question is how accurately accounts fluctuations collisional aggregation process. Such are particularly important dilute suspensions. Even absence of turbulence, Poisson collision times suspensions may result substantial variations process, resulting a broad distribution to reach certain size. We quantify accuracy describing fluctuating history larger settles under effect gravity quiescent fluid and collides with suspension smaller droplets were initially randomly distributed space (“lucky model”). assess upon lucky compute cumulative times. The latter be sensitive enough detect subtle increase associated collisions between multiple droplets. incorporates two distinct ways: through random spatial superdroplets Monte Carlo involved. Using specifically designed numerical experiments, we show both on their own give an accurate representation fluctuations. conclude coagulation driven by gravity.