An experimental study on jet impingement on a very high speed moving surface

Motivated by the need to improve transfer efficiencies of liquid coatings from jet impingement, an experimental investigation into jet impingement on very high speed moving surfaces is presented. Seven different Newtonian liquids with widely varying shear viscosities were made to impinge on a surface which could be made to move at speeds up to 350km/hr. Tests for the Newtonian liquids were done with several modified surfaces to study the effects of roughness and surface inconsistencies. Nozzle sizes and impingement angles were varied to interrogate their effects on the interaction of the impacting jet and moving surface while high speed photography was employed to capture these interactions. Spread radii and spread widths were measured for viscous fluids which deposited. While it was observed that stable jets of fluids with sufficiently high viscosities almost always deposited, tests with water indicate that the effects of the impingement angle as well as jet diameter significantly alter the locations of boundaries between deposition, spatter and lamella lift-off. Impingement angles that result in jet velocities with large components of velocity parallel to the surface velocity are prone to deposit. Jets of smaller diameters are also prone to deposit. It was observed that both the jet velocity and surface velocity are important determining factors in the likelihood of deposition. The deposition of viscous fluids demonstrated that it is possible to observe transitions from deposition to lift-off and vice versa through mechanisms that trigger random fluctuations in the lamella. The track distance covered before a transition from lift-off to deposition occurs is shown to be a Poisson Process.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat