Droplet-surface impact at high pressures

The present work is a study of dropletsurface collisions at high pressures. A technique adapted from Lagrangian particle tracking is presented. The tracking technique is a hybrid between traditional high-speed, high-resolution photography used for drop studies and particle tracking velocimetry. It is suitable for high pressure systems with very short relaxation distances and with a non-steady background fluid. Collisions of droplets towards dry and wet walls were studied for systems of liquid decane with CO(2) or N(2) as gas phase, and a single component, two phase pure CO(2) system at saturation. At low impact velocities, higher deposition efficiencies were observed for collisions against the dry wall compared to the wet wall. The events are described in terms of micro-scale mechanisms. Additionally, deposition efficiency maps are given, and it is shown how to use these in two different modelling frameworks. (C) 2010 Elsevier Ltd. All rights reserved.