Experimental and Theoretical Investigation of Impinging Droplet Solidification at Moderate Impact Velocities

Abstract Spreading of liquid drops on cold solid substrates is a complicated problem that involves heat transfer, fluid dynamics, and phase change physics combined with complex wetting behaviors at the contact-line. Understanding the physics behind the non-isothermal spreading of droplet is of utmost importance due to its broad applications in diverse areas of industry such as in additive manufacturing processes. This work mainly focuses on determining the important physical parameters involved in the non-isothermal spreading of droplets with low contact angle (less than 90 deg) as well as controlling the post-solidification geometry of impinging droplets with moderate impact velocity where spreading is driven by impact velocities, but fingerings or instabilities do not occur at the contact-line. Using analytical modeling, a possible explanation for contact-line arrest is produced that demonstrates that the final radius of droplets of moderate impacting velocity is independent of the initial conditions including the impact dynamics and temperature gradients. The predictive capacity of this model is confirmed with experimental results.