Multiphase Flows

Multiphase Flows

Convergence tips for transient simulations with cavitation conditions

    • FAQFAQ
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      When running a multi-phase transient simulation with cavitation settings turned on, here are some tips to obtain better results and ensure convergence: •Solve the problem as a cavitation problem: use the Rayleigh-Plesset model •The Cavitation Vaporization Coefficient and the Cavitation Rate Under-Relaxation Factor can be used to control the cavitation rate. The Cavitation Rate Under-Relaxation Factor is the fraction of the instantaneous interphase mass transfer rate applied at the current time step. Reducing this factor to 0.1 is usually sufficient to limit vapor formation. •Ensure that the timestep is not overly large, as that may be a source of instability •If cavitation occurs close to an outlet and results in the flow being blocked, then extend the solution domain. Since the flow near an outlet has a large tangential component, the presence of cavitation may result in backflow. Therefore, for extreme cases, the cross-sectional area of the added slip-wall extension can be gradually decreased in order to increase the normal component of the flow to allow it to exit. This can be implemented in the form of an extended downstream section with slip walls. •Change the downstream boundary condition from outlet to opening