Experimental Study of Ventilated Cavities on Dynamic Test Model

Abstract

A series of experiments were conducted to examine ventilated cavity physics. Over two hundred test runs were performed. Tow tank tests were conducted to examine the stability of ventilated cavities. The tests were performed on three different models at speeds up to 55 feet per second. One 6.25-inch diameter model allowed body motion with 3 degrees of freedom. The model also employed a cavitator that could be pitched to +/- six degrees angle of attack. The models allowed the examinationbof ventilation data at a variety of length scales and for a number of cavitator shapes and sizes. Some tests also incorporated simulated rocket exhaust. High frequency solid-state pressure transducers were used to determine the stability of the cavities. The tests confirmed that the dominant cavity frequency was correlated with the cavity length and towing speed. Dynamic model motion and the rocket exhaust both tended to enhance overall cavity stability. The impact of free shear instability on cavity stability was negligible at these speeds.