Pressure and wall shear stress from high-speed droplet impact

We report on experimental and numerical results of the impact of millimeter sized droplet with high-speed projectile. The impact velocity $V_{imp}$ ranges between 70 m/s and 245 m/s and is sufficiently high that the compressibility of the liquid becomes important. High-speed images reveal non-axisymmetric lamella spreading, hydrodynamic and secondary cavitation and the ejection of a thin jet from the distal side of the droplet. The spreading velocity is supersonic for the impact velocities tested. Secondary cavitation at the distal side of the droplet is found for $V_{imp}\gtrsim$ 120 m/s. The experiments are compared and analyzed further with a CFD model based on a compressible volume of fluid (VoF) method. Excellent agreement of the early droplet and lamella dynamics is obtained with the experimental data. Additionally, we provide quantitative data for the pressure loading and the shear stress on the projectile using spatio-temporal maps.