A dynamical study of a bubbly flows in a transversal varying section duct (Venturi), is modeled by the use of the mass and momentum phases equations, which are coupled with the Rayleigh-Plesset equation of the bubbles dynamics. The effects of the throat dimension and the upstream void fraction on flow parameters are investigated. The numerical resolution of the previous equations set let us found that the characteristics of the flow change dramatically with upstream void fraction. Two different flow regimes are obtained: a quasi-steady and a quasi-unsteady regimes. The former is characterized by a large spatial fluctuations downstream of the throat, which are induced by the pulsations of the cavitation bubbles. The quasi-unsteady regime corresponds to flashing flow in which occurs a bifurcation at the flow transition between these regimes. This transition occurs at Rc? 4.3 which corresponds to ?s? 4.710-3. An analytical expression for the critical bubble size at the flashing flow point is also obtained and compared with theoretical data.
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