Abstract

Impinging liquid jets are widely used for removing films or layers, either by distributing a solution which effects removal or by suppling hydraulic forces to push the layer out of the way or overcome its adhesion to the underlying substrate. Our work is this area comes from an interest in cleaning tanks, originally the ones used in the food and pharma sectors and on ships, but the results turn out to be applicable to the military variety. This presentation will describe work on the underlying fluid mechanics of the liquid films generated by impinging jets, which give high local shear stresses and lead to hydraulic jumps. We have found that the removal of viscoplastic soils and other complex fluids is dictated by the momentum in the film. A simple kinetic law was developed for this which gives a very good description of observed cleaning behaviour. Very recently we have found a phenomenological basis for this kinetic law, which will be presented. The presentation will feature demonstrations. Stuart Clarke will get wet.