Role of particle volume fraction on particulate suspension droplet evolution, transition and Hysteresis

Abstract

We study the transitional dynamics of the non-Brownian particulate Newtonian liquid jet for different particle volume fractions ($\phi$). We focus on the influence of particle volume fraction on the critical inflow velocity at which the dripping-jetting (i.e., dripping to jetting and jetting to dripping) transition occurs for the ratio of the nozzle diameter to the particle diameter ($D_n/D_p$=20). The experiments were conducted by increasing (forward sweep) and decreasing (reverse sweep) the flow rate. These experiments were repeated for different volume fractions. We observe, with an increase in particle volume fraction, the transition from the dripping to the jetting regime occurs through a chaotic dripping regime. With an increase in the particle volume fraction, the jetting regime has occurred at early flow rates during dripping to jetting transition (in forward sweep), and the jetting to dripping transition (reverse sweep) occurred at a lower flow rate than the forward sweep. The particle volume fraction impacts the hysteresis observed for the Newtonian fluid. Due to the changes in the critical flow rate where transition occur, the widening of the hysteresis loop of flow rate with the pinchoff length is observed. The transition from dripping to jetting is observed to have the recurrent escape of the pinchoff mechanism as the jet length changes, influencing the droplet size distribution. The frequency of droplet pinchoff and droplet size have decreased as the particle volume fraction has increased. As the particle volume fraction increases, the size distribution between the dripping and jetting regimes decreases.