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JBS January 5, 2007 07:13

Cavitation and Compressible Liquid
 
I am trying to simulate a pressure pulse in an tube (L=250mm, D=2.5mm) filled with liquid. There is a dead end (wall) on one side of the tube, the other is an opening where a step function for Pressure is applied (100 to 75 bar). The Liquid is defined with pressure dependant density. Vapor is constant property gas. The Pressure is at least 2 orders of magnitude above the saturation pressure everywhere, so no cavitation is expected.

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1st Simulation Single Phase with Liquid only

2nd Simulation: Mass transfer Off, both Fluids present

3rd Simulation Mass transfer On, (Cavitation Model)

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Multiphase Options: Homogenious

Heat Transfer: Homogenious, Isothermal

Fluid Details: Continuous (both)

Interphase Transfer: None

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All three Simulations give different Pressure Plots for the Dead End location. During the first time steps the max Vapor Volume Fraction rises from its Initial Value of 1e-15 (Solver Limit) to a Value of Order 1E-5 in the second and 5E-5 in the third simulation.

How to conserve the behaviour of the pure liquid as long as there is no cavitation without swiching from a single to a multiphase simulation ?



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