Numerical study of cavitation inception in the near field of an axisymmetric jet at high Reynolds number

Cavitation inception in the near field of high Reynolds number axisymmetric jets is analyzed using a simplified computational model. The model combine s a vorticity-stream-function finite-difference scheme for the simulation o f the unsteady flow field with a simplified representation for microscopic bubbles that are injected at the jet inlet. The motion of the bubbles is tr acked in a Lagrangian reference frame by integrating a semiempirical dynami cal equation which accounts for pressure, drag, and lift forces. The likeli hood of cavitation inception is estimated based on the distributions of pre ssure and microscopic bubbles. The computations are used to examine the rol e of jet slenderness ratio, Reynolds number, bubble size, and bubble inject ion location on the cavitation inception indices. The results indicate that , for all bubble sizes considered, the cavitation inception index increases as the jet slenderness ratio decreases. Larger bubbles entrain more rapidl y into the cores of concentrated vortices than smaller bubbles, and the cor responding inception indices are generally higher than those of smaller bub bles. The inception indices for larger bubbles are insensitive to the injec tion location, while the inception indices of smaller bubbles tend to incre ase when they are injected inside the shear layer near the nozzle lip. Alth ough it affects the bubble distributions, variation of the Reynolds number leads to insignificant changes in pressure minima and in the inception indi ces of larger bubbles, having noticeable effect only on the inception indic es of smaller bubbles. Computed results are consistent with, and provide pl ausible explanations for, several trends observed in recent jet cavitation experiments. (C) 2000 American Institute of Physics. [S1070-6631(00)00310-X ].