Interaction of Liquid Droplets With Planar Shock Waves

Interactions and breakup processes of 1.50-mm-diameter ethyl alcohol droplets and 5.14-mm-diameter water bubbles with planar shock waves were observed using double-exposure holographic interferometry. Experiments were conducted in a 60 mm × 150 mm cross-sectional shock tube for shock Mach number 1.56 in air. The Weber numbers of droplets and liquid bubbles were 5.6 × 103 and 2.9 × 103, respectively, while the corresonding Reynolds numbers were 4.2 × 10 and 1.5 × 105. It is shown that the resulting holographic interferogram can eliminate the effect of the mists produced by the breakup of the droplets and clearly show the structure of a disintegrating droplet and its wake. This observation was impossible by conventional optical flow visualization. It is demonstrated that the time variation of the diameter of a breaking droplet measured by conventional optical techniques has been overestimated by up to 35 percent.