Bubbly Cavitating Flow Through a Converging Nozzle

Abstract

In the present work, the bubbly cavitating flow phenomena after passing through the converging nozzle is numerically investigated. The dynamic of the cavitating bubbles is modeled by the use of the mass and momentum phase's equations, which are coupled with the Rayleigh-Plesset equation of the N bubbles dynamics. However, assuming that the same initial conditions of all bubbles are identical and that all bubbles are equi-distant from each other simplifies the governing equations. Equation set is numerically resolved by the use of a fourth order Runge-Kutta scheme. The numerical resolution of the previous equations set let us found that the bubble radius distribution, fluid velocity and fluid pressure change dramatically with upstream void fraction and an instability appeared just after the passing the converging nozzle for both cases one bubble N=1 and two bubbles N=2. Indeed, for the case of one bubble N=1, the flashing flow phenomena occurs for an upstream void fraction α s =11.2x10 -3 , which corresponds to a critical bubble radius R c =1.8. Whereas, for bubble number N=2, the same phenomenon occurs for α s = 8.9x10 -3 , with R c =2. This difference is due to the bubble interaction. Also, we found that, the bubble number N strongly affect the bubble frequency. However, with increase the bubble number, the maximum size of the bubbles increases and bubble frequency oscillation decrease.