CHOKING OF STRUT-VENTILATED FOIL CAVITIES.
HYDRONAUTICS INC LAUREL MD
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Presented are the results of an investigation of the choking phenomenon in base vented strut cavities. In practice such base vented struts support a ventilated foil and provide the ventilation air for the foil through the strut cavity. An expression for the rate of air entrainment in ventilated cavities is derived. This expression fits previously reported experimental data except at low cavitation numbers, when free surface- solid boundary- and gravitational effects may become important. The shape of the cavity behind a strut, supporting a strut-ventilated foil, is analyzed. It is shown that the shortest section of the strut cavity is at the free surface, and that its length is controlled by the air flow through it. The choking phenomenon is analyzed by relating the air flow through the strut cavity to the air demand of the foil cavity. From this analysis a choking coefficient is defined. A series of experiments is described in which, for three strut-supported foils, the depth at choking was determined as a function of free stream velocity, angle of attack, and air pressure. Author
- Marine Engineering
- Fluid Mechanics