William C. Moss
Lawrence Livermore Natl. Lab., L-200, P. O. Box 808, Livermore, CA 94550
Douglas B. Clarke
John W. White
David A. Young
Lawrence Livermore Natl. Lab., Livermore, CA 94550
Numerical hydrodynamic simulations of the growth and collapse of a 10-(mu)m air bubble in water were performed. Both the air and the water are treated as compressible fluids. The calculations show that the collapse is nearly isentropic until the final 10 ns, after which a strong spherically converging shock wave evolves and creates enormous temperatures and pressures in the inner 0.02 (mu)m of the bubble. The reflection of the shock from the center of the bubble produces a diverging shock wave that quenches the high temperatures (>30 eV) and pressures in less than 10 ps (FWHM). The picosecond pulse widths are due primarily to spherical convergence/divergence and nonlinear stiffening of the air equation of state that occurs at high pressures. The peak temperature at the center of the bubble is affected strongly by the ionization model used for the air. The results are consistent with recent measurements of sonoluminescence that had optical pulse widths less than 50 ps and 30-mW peak radiated power in the visible. [This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]