An Experimental Study of Attenuation of Shock Waves in Three Mixtures
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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This study was performed to investigate experimentally the possibility of using porous material to defeat or significantly reduce the hydraulic ram effect. Two experiments were performed to determine how the addition of a gas to a fuel-foam mixture would affect the attenuation of shock waves and weaker pressure pulses. In the first experiment, water, water with reticulated open cell polyurethane foam, and water with Pneumacel a new Du Pont product composed of Freon inflated Dacron fibers pressed into a mat were each impacted by a flat aluminum disc to generate plane one dimensional shock waves in the mixtures. Four pressure transducers were located at specified distances below the surface and the attenuation of the pressure pulses in the different mixtures was measured. In the second experiment 12 in. spheres were fired into a tank containing, in turn, each of the three mixtures, and again the attenuation of the pressure pulses was determined. In each experiment there was an increase in attenuation noted when the reticulated foam was added to the water. However, a much greater increase was noted when the Pneumacel replaced the foam. Pressure dropped and remained below approximately 14 psi within a few inches of the surface in all tests with Pneumacel.