Aphros: High Performance Software for Multiphase Flows with Large Scale Bubble and Drop Clusters. We present the high performance implementation of a new algorithm for simulating multiphase flows with bubbles and drops that do not coalesce. The algorithm is more efficient than the standard multi-marker volume-of-fluid method since the number of required fields does not depend on the number of bubbles. The capabilities of our methods are demonstrated on simulations of a foaming waterfall where we analyze the effects of coalescence prevention on the bubble size distribution and show how rising bubbles cluster up as foam on the water surface. Our open-source implementation enables high throughput simulations of multiphase flow, supports distributed as well as hybrid execution modes and scales efficiently on large compute systems.