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[User Defined Scalar in the Eulerian Model

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Old   December 11, 2014, 10:28
Default [User Defined Scalar in the Eulerian Model
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Rafael Cerqueira
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Hello!

I am very used to the VOF model in Fluent.
However, in the past days I decided to simulate a few cases with the Eulerian model.

I'm planning to simulate some sort of bubble column reactor with mass transfer with the aid of two User Defined Scalar, one in the continuous phase and other in the dispersed phase. Something in the line of this work "Mass transfer in bubble columns".

Unfortunately, I had lots of problems with the user-defined scalars.
First, I am not sure how the "mass flow rate" flux function and the "default" unsteady function is modeled when the multiphase eulerian model is activated.
The source of this questioning lies in the fact that the scalar is being advected to cell regions where the phase volume fraction (VOF) is zero.

To illustrate my problem, I set up one-dimensional case to test a user-defined scalar, located in dispersed phase.
In this 1D case i did not added a source term to model the interfacial mass transfer and the spatial discretization used is the first order upwind.

The boundary conditions are:

west: velocity-inlet
- phase-1: u=0.1 m/s; VOF = 0.1; scalar = 1.0
- phase-2: u=0.0 m/s;

east: pressure-outlet

north: simmetry
south: simmetry

The results, from a certain time-step are:

userDefinedScalar_contour.jpg

dispersedPhase_contour.jpg

From the two illustrations is possible to see that the UDS scalar field is not being properly advected.

The case file and the 1d mesh are here:

1d_test.zip

Someone ever encountered this kind of problem?


Best Regards,
Rafael de Cerqueira
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