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24.3.1 Setup Procedure

The procedure for setting up a solidification/melting problem is described below. (Note that this procedure includes only those steps necessary for the solidification/melting model itself; you will need to set up other models, boundary conditions, etc. as usual.)

1.   To activate the solidification/melting model, turn on the Solidification/Melting option in the Solidification and Melting panel (Figure  24.3.1).

Define $\rightarrow$ Models $\rightarrow$ Solidification & Melting...

Figure 24.3.1: The Solidification and Melting Panel
figure

FLUENT will automatically enable the energy equation, so you do not have to visit the Energy panel before turning on the solidification/melting model.

2.   Under Parameters, specify the value of the Mushy Zone Constant ( $A_{\rm mush}$ in Equation  24.2-8).

Values between $10^4$ and $10^7$ are recommended for most computations. The higher the value of the Mushy Zone Constant, the steeper the damping curve becomes, and the faster the velocity drops to zero as the material solidifies. Very large values may cause the solution to oscillate as control volumes alternately solidify and melt with minor perturbations in liquid volume fraction.

3.   If you want to include the pull velocity in your simulation (as described in Sections  24.2.2 and 24.2.5), turn on the Include Pull Velocities option under Parameters.

4.   If you are including pull velocities and you want FLUENT to compute them (using Equation  24.2-15) based on the specified velocity boundary conditions, as described in Section  24.2.5, turn on the Compute Pull Velocities option and specify the number of Flow Iterations Per Pull Velocity Iteration.

figure   

It is not necessary to have FLUENT compute the pull velocities. See Section  24.3.2 for information about other approaches.

The default value of 1 for the Flow Iterations Per Pull Velocity Iteration indicates that the pull velocity equations will be solved after each iteration of the solver. If you increase this value, the pull velocity equations will be solved less frequently. You may want to increase the number of Flow Iterations Per Pull Velocity Iteration if the liquid fraction equation is almost converged (i.e., the position of the liquid-solid interface is not changing very much). This will speed up the calculation, although the residuals may jump when the pull velocities are updated.

5.   In the Materials panel, specify the Melting Heat ( $L$ in Equation  24.2-3), Solidus Temperature ( $T_{\rm solidus}$ in Equation  24.2-3), and Liquidus Temperature ( $T_{\rm liquidus}$ in Equation  24.2-3) for the material being used in your model.

Define $\rightarrow$ Materials...

If you are solving for species transport, you will also have to specify the Melting Temperature of pure solvent ( $T_{\rm melt}$ in Equations  24.2-5 and 24.2-6). The solvent is the last species material of the mixture material. For each solute, you will have to specify the slope of the liquidus surface ( Slope of Liquidus Line) with respect to the concentration of the solute ( $m_i$ in Equations  24.2-5 and 24.2-6), the Partition Coefficient ( $K_i$), and the rate of Diffusion in Solid. It is not necessary to specify $m_i$ and $K_i$ for the solvent.

6.   Set the boundary conditions.

Define $\rightarrow$ Boundary Conditions...

In addition to the usual boundary conditions, consider the following:

  • If you want to account for the presence of an air gap between a wall and an adjacent solidified region (as described in Section  24.2.6), specify a nonzero value, a profile, or a user-defined function for Contact Resistance ( $R_c$ in Equation  24.2-16) under Thermal Conditions in the Wall panel.

  • If you want to specify the gradient of the surface tension with respect to the temperature at a wall boundary, you can use the Marangoni Stress option for the wall Shear Condition. See Section  7.13.1 for details.

  • If you want FLUENT to compute the pull velocities during the calculation, note how your specified velocity conditions are used in this calculation (see Section  24.2.5).

Section  24.3.2 contains additional information about modeling continuous casting. See Sections  24.3.3 and 24.3.4 for information about solving a solidification/melting model and postprocessing the results.


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