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The viscosity field
In PHOENICS code, the density field can be calculated in SEM or in HOL methods as follows:
RHO = RHOG * (1-VFOL) + RHOL * VFOL (it's logical) G: for Gaz L: for Liquid VFOL: Volume Fraction of Liquid but why ? the viscosity field is calculated as follows: ENUL = ENULG * (1-VFOL) + ENULL * VFOL |

Re: The viscosity field
Look to the one-fluid formulation. To be prefectly correct the Indicator function (VFOL) is suppose to be a heavyside (step) function . so RHO is NOT a mixture but is EITHER a gas or liquid. this is also true for viscosity. Now we introduce our VOF, replace our step function with a volume intergral and people attempt to place some physics where we have averaged them all out.
so... ----------------------------------------------------- Q.. why ? the viscosity field is calculated as follows: A.. That is just what the final form of the equations came to when we put all of our assumptions.. ----------------------------------------------------- |

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