Observations on bubble dynamics at high pressures and bubble dynamics in stagnation flow

Development of a ruby laser light source permitted moving pictures of bubble growth and collapse to be made during a two-millisecond observation time at rates from 100,000 to 1,000,000 frames per second with exposure time of approximately 2x10 to the -8th power seconds. The coherent nature of the laser illumination revealed shock waves without need for Schlieren techniques. It was evident that bubble collapse microjets rather than shockwaves caused greater damage to fused quartz specimens. There also seemed to be damaging jets generated during bubble rebound. Sine possible use of cavitation to assist deep bore earth drilling has been proposed, experiments were conducted utilizing spark generated cavities in water and non-Newtonian solutions at ambient pressures up to 35 MPa (10,000 ft bore-hole depth). To facilitate analysis, single bubbles were generated in a flow normally impacting a solid wall. The bubbles assumed an elliptical shape near the stagnation region and relatively fine bubble jets were observed during both collapse and rebound. The dynamic behavior of spark generated cavitation bubbles in an experimental stagnation flow was studied with high speed cine photography.