The erosion and cleaning effect of jets is enhanced when the degree of cavitation on or near the bottom of the hole is increased. Analyses indicate that self-excited, acoustically resonating nozzles, causing jets to be structured with large discrete vortex rings, should promote cavitation to depths several times greater than for conventional jets. The new nozzle designs are shown to be suitable for existing mechanical drill bits and may even effect hole cleaning in the absence of cavitation.

This study presents the advantages of pulsing a submerged j e t t o increase its erosion capability (particularly as caused by cavitation) in augmenting deep-hole drill bits, Various methods of accomplishing the pulsation are presented and discussed. are acoustic oscillators which passively accomplish pulsations in the flow at frequencies corresponding to a Strouhal number in the range of 0. 2 t o 1.0. Such passive oscillators are assessed to be feasible candidates for development into practical deep hole drill bit systems and a long range plan for this research and development is presented and discussed. The most attractive systems uncovered , Work performed undef Sandia National Laboratories Contract No.

Analyses of self-excited, resonating jets have been corroborated by laboratory experiments. These structured jets achieved cavitation at greater ambient pressures and showed enhanced erosivity in comparison to the nonstructured jets from conventional drill bit nozzles.

A serf-excited cavitating jet assembly is examined for possible use as an underwater noise generator. The principles of the system are based on matching the natural frequency of a submerged jet with that of a resonant chamber through a feedback mechanism. The case of an organ pipe resonant feed tube is thoroughly investigated• In this case, feedback is obtained by shaping the nozzle in order to optimize its interaction with instabilities in the shear layer of the jet. The performance of the noise generator is evaluated and its characteri.•tics analyzed, including the influence of the pressure drop across the nozzle, the cavitation number, and the organ pipe length. It is observed that the efficiency of STRATOJETs (self-resonating cavitating jets) is more than two orders of magnitude higher than that of a conventional cavitating jet. The knowledge developed in this study allows for selection of the amplitude and frequency of the emitted noise by proper dimensioning of the assembly and correct choice of the functioning conditions.

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