Measurement of the unsteady drag of shock-accelerated micro-droplets with uncertain diameter

To address a lack of targeted experimental data in unsteady flow conditions, we have been conducting a campaign of experiments, integrated with ongoing validation and modeling efforts, to measure the drag of shock-accelerated micro-droplets. The experiments are being conducted in the Horizontal Shock Tube facility to examine shock-accelerated liquid micro-particles in a dilute suspension at low Mach numbers. An eight-pulse particle tracking diagnostic measures individual particle positions, and a shadowgraph system measures shock location, with pressure transducers providing shock speed at the test section. These diagnostics give us detailed measurements of particle positions versus time for Mach 1.2, 1.3 and 1.4 experiments. Droplet sizes of 2, 6, and 8 μm were investigated, expanding on the 4 μm droplets presented previously. However, the particle diameter is not measured directly but is obtained from the input size distribution. To recover the empirical drag curve, many trajectories are averaged. Various approaches for performing the averaged will be discussed. Finally, the new droplet data shows drag approximately 20% above the standard drag curve, in agreement with previously presented 4 μm droplets.