Four-dimensional Imaging of Supersonic Projectile and Rain Droplet Impact

The damage associated with high-speed rain weather encounters (hydrometeors) produce significant surface erosion and can limit vehicle flight performance. The raindrop deforms due to the leading vehicle shock before impinging on the surface. This coupled droplet interaction with the high-speed vehicle flow is inherently three-dimensional and complex. It needs to be characterized to predict the expected vehicle response in weather events. This study presents a novel MHz-optimized optical setup for four-dimensional (4D) imaging of high-speed hydrometeor interactions; the focus is characterizing the deformation and impact dynamics on blunt-faced projectiles. Four diffuse back-illuminated views are used to generate reconstructions of droplet deformation before and during the surface impingement. The projectile speed, droplet impact location, droplet deformation, and subsequent formation of radial jets are quantified.