This paper presents an experimental study of reverse transition occurred in the boundary layer flow along a flat plate placed at the center of two-dimensional symmetrical contraction. The experiments were carried out in the contractions of three kinds: Cheers, cosine and WITOSZYNSKI types. the reverse transition was examined based on the velocity profile, thickness and turbulence of the boundary layer along the flat plate. The results were discussed in comparison with those of existing in vestigations.

View full abstract

The configuration of the nozzle exit of the peripheral skirt of ACVs has hitherto been designed mainly in view of the hydrodynamic contact drag and the seaworthiness characteristics, and this has brought succesful results. At the present stage of development, however, it seems to be worthwhile to analize the nozzle configuration in view of the hovering performance of ACVs. The present study theoretically analizes the effect of the configuration of the nozzle exit on the hovering performance. The outer wall of the nozzle is fixed to be inclined at 135° measured clockwise from the horizon and the effects of varying the slope of the innerwall, of the relative location of the inner and outer nozzle and of the nozzle height on the cushion pressure, the volume flow rate and the air horse power are investigated. It is shown that the larger the slope of the inner wall α is, the higher the cushion pressure is and the parallel nozzle walls, which correspond to the conventional peripheral jet type nozzle, give the maxi-mum cushion pressure, that the minimum volume flow rate occurs at 20°-40° of the inner wall inclination, and that, as a combined effect of α on the cushion pressure and the volume flow rate, the required air horse power is little affected by α except the case of the larger nozzle height where the larger α gives a slightly better performance. It is then suggested that the determination of α shoud be made to bring such an optimum combination of the total pressure and volume flow rate that gives the best operating condition to the blower. In the range of small nozzle height, the effect on the hovering performance of the relative location of the inner and the outer walls is small in so far as the lower end of the inner wall is located over that of the outer while at larger nozzle height, the larger vertical gap between the inner and the outer wall brings a slightly better performances. The lower location of the inner wall than the outer always gives poor performance.

View full abstract