Splash threshold of a droplet impacting a moving substrate

The effect of ambient pressure on the corona splash resulting from a droplet impacting on a smooth dry moving substrate is investigated experimentally. As the ambient pressure is reduced the upstreamenhanced corona splash is initially suppressed to a prompt splash, and on further reduction of the ambient pressure prompt splash transitions to deposition. The splash threshold pressure is measured under different conditions including droplet diameter, droplet speed, substrate speed, and liquid viscosity. The splash and suppression mechanisms are explained based on aerodynamics. A model for the splash threshold pressure is presented that incorporates the substrate velocity into an existing model for droplet impingement on a stationary substrate. This new model approximately collapses the results from experiments with a multitude of variables onto a single curve.