Effect of droplet loading on multiphase flow past a circular cylinder at low Mach numbers

The aerodynamic characteristics of droplet-laden flows past a circular cylinder are investigated using a compressible multiphase flow solver based on the six-equation model. The numerical framework is validated against benchmark cases for both multiphase and single-phase flows. Unlike prior studies that have primarily examined compressibility effects in single-phase flows or multiphase interactions at higher Reynolds numbers, this work is the first to systematically analyze the combined influence of compressibility and droplet–gas coupling in the low-Mach, laminar regime. The study explores the effects of droplet size, volume fraction, and Mach number on flow unsteadiness, droplet distribution, and aerodynamic forces. Results reveal that increasing the droplet volume fraction suppresses vortex shedding and promotes a transition to steady flow, primarily through enhanced interphase drag. Droplets preferentially accumulate in the front stagnation region, with minimal penetration into the wake, particularly under high inertial loading. The mean drag increases with droplet concentration, while the lift initially rises and then diminishes as unsteady behavior is suppressed, accompanied by a corresponding decrease in Strouhal number. At higher Mach numbers, smaller droplets contribute more significantly to drag due to stronger coupling with the compressible gas phase. Overall, the study provides new physical insights into the interplay between compressibility and multiphase dynamics in laminar flows, a regime that has remained largely unexplored.