Role of dispersed particles on the dynamics of the umbrella cloud of a buoyant plume

Particle-laden buoyant plume is a common occurrence in geophysical flows. We quantitatively study the modification in the plume behavior under the influence of low particle volume fraction, $\phi_{v} $. Particles with mean diameter $d_{p} =$100$\mu $m, density, $\rho_{p} =$2500 kgm$^{\mathrm{-3}}$, and $\phi_{v} =$0-0.7{\%} were injected along with the lighter plume fluid. A particle trough, characterized by radius, R, and depth, $L_{p} $, was observed and could be attributed to the phenomenon of ``particle fall-out'' and ``particle re-entrainment''. The trough either sustains or collapses depending on the plume conditions at the source.