programmer's documentation
Data setting for the cavitation module

Introduction

The cavitation module is based on a homogeneous mixture model. The physical properties (density and dynamic viscosity) of the mixture depends on a resolved void fraction and constant reference properties of the liquid phase and the gas phase. The void fraction is given by an advection equation with a vaporization/condensation source/sink term. This term is modeled by the Merkle's model. The module also integrates the eddy-viscosity correction of Reboud.

Activation of the module

The module can be activated in the usipph routine in cs_user_parameters.f90. The corresponding keyword is icavit in the Module for calculation options module. This keyword can take the values:

Cavitation module specific parameters.

When the module is activated, its specific input parameters should be set in the usipsu routine of cs_user_parameters.f90 file. An example is given in cs_user_parameters-cavitation.f90.

Homogeneous mixture physical properties

As soon as icavit $ \ge 0 $, the reference density, in $ kg/m^3$ , and molecular viscosity, $ kg/(m\cdot s)$, of the liquid phase and the gas phase should be set. For instance:

rol = 1.d3
mul = 1.d-3

for the liquid and:

rov = 1.d0
muv = 1.d-5

for the gas phase.

Model parameters of the vaporization term (Merkle model)

When icavit = 1, Merkle's model parameters should be set. The Merkle model is base on a barotropic law for the density (see cavitation.f90). In that way, its principal parameter is the saturation pressure of the fluid, in $ kg/(m\cdot s^2)$. For instance, the saturation pressure of the water at twenty celcius degrees is:

presat = 2.d3

Merkle's model also requires a reference length scale and velocity of the flow. For instance:

linf = 0.1d0
uinf = 1.d0

These scales are integral scales. For instance, considering the cavitating flow across a foil in a duct, the reference velocity should be the bulk velocity and the reference length scale should be the chord of the foil.

Interaction with turbulence

As soon as icavit $ \ge 0 $, the mixture eddy-viscosity correction proposed by Reboud can be accounted for:

icvevm = 1

If icvevm = 0, the Reboud correction is desactivated. Using an eddy-viscosity model (see turbulence options), this option is recommended, such that icvevm = 1 is the default setting. Of course, this option has no effect for second moment closure or large eddy simulations. Note that the the coefficent mcav of the reboud correction (see cavitation.f90) can also be adjust in the usipsu routine.

Numerical options

Advanced numerical parameters may also be set in this routine, if necessary. The concerned variables are listed in Numerical parameters.