EXPERIMENTAL INVESTIGATION INTO FLOW BEHAVIOR OF THIN WATER FILMS - EFFECT ON A COCURRENT AIR-FLOW OF MODERATE TO HIGH SUPERSONIC VELOCITIES - PRESSURE DISTRIBUTION AT SURFACE OF RIGID WAVY REFERENCE STRUCTURES

The first part of this paper reports on experimental investigations into the flow behaviour of thin water films and their effect on a cocurrent air flow of supersonic velocities ranging from moderate to high. Compared with an earlier paper by this author, this work covers an extended Mach number range (1. 2 less than M less than 2. 4). In addition, the gas boundary layer has been studied more thoroughly. With regard to the results for the subsonic case a report is given on the friction coefficient of wavy water films, mean film thickness, upper stability limit of the film flow (disturbance waves, droplet formation), temperature and velocity profiles of the cocurrent air flow. The second part of this paper is still in its teens. Since it is almost impossible to measure the pressure distribution at the interface of a wavy liquid film and a high velocity gas flow, the author measured the pressure distribution along rigid wavy structures imitating the wave structure of the film. Wave length and amplitude are small with respect to the boundary layer thickness of the air flow. As could have been expected, the pressure distribution is qualitatively the same for subsonic and supersonic boundary edge velocities. A quantitative applicability of these results to theoretical approaches to film stability is questionable.