Unveiling scaling laws, dispersal morphologies and phase diagrams in gas–particle systems under blast-supersonic flow coupling

In compressible gas–particle flows the dispersion of particle clouds driven by a blast is widely observed in extreme natural and engineering scenarios. Whereas prior research has primarily focused on planar shock or blast-driven configurations, this study investigates a gas–particle system combining a finite-source blast with supersonic inflow. Accordingly, the compressible multiphase particle-in-cell method is employed to simulate the flow. The resulting waves including main shock, contact surface and secondary shock are parametrically investigated, where the main shock radius follows an approximate power law to time. Driven primarily by the drag force, a simplified two-stage scaling law for spanwise leading particle dispersion is derived: a time-squared dependence during the blast-dominated stage and growth behaviour ranging from linear to logarithmic in the subsequent flow-impingement stage. Furthermore, four dispersion morphologies are identified: compressed, uniform, eroded and jetting, each explained by specific wave–particle interaction mechanisms. Finally, a phase diagram correlating these morphologies with the inflow Mach number, Stokes number and pressure ratio is constructed. These findings reveal the coupled mechanisms in gas–particle systems driven by a blast and supersonic inflow, providing a predictive basis for impulse effects and particle dispersion.