An Experimental Study on the Dynamics of Droplets Approaching a Solid Surface Driven by Shock/Blast Waves

This paper presents an experimental study on the transient behaviors of droplet approaching a solid surface driven by shock/blast waves. The experiments were conducted in the shock tube facility available at the City College of New York. A droplet injection system integrated at the top of the shock tube test section, together with a test plate mounted inside of the test section, with well-synchronized control of all sub-systems, enables us to reproduce the shock-droplet-surface interactions under various test conditions. Shock waves of different Mach numbers were created by using different diaphragm materials and thicknesses. Multiple droplet-releasing ports were designed and manufactured to offer variable distances between the surface and the droplet upon impact by the shock/blast waves. A high-speed Schlieren imaging system, consisting of a high-speed camera, a high-intensity LED point light source, and a series of optics, was used to visualize the complex shock-droplet-surface interactions. It was found that, the droplet deforms with a delayed response to the shock impact, followed by a catastrophic break-up and rapid vaporization process, transporting along with the post-shock flows. When rebounded by a second less intensive shock reflected from the test surface, the droplets cloud was found to be further obliterated, but ultimately remained transporting in the direction of the incident shockwave.