Melting-Solidification Model Reference

Melting-Solidification Properties

Linearize Melting

When activated, the source term due to latent heat is linearized. This option is deactivated by default.

Under-Relaxation Factor

Governs the extent to which the newly computed solution supplants the old solution for each iteration.

Melting-Solidification Physics Models

When the Melting-Solidification model is activated, the following model becomes available under Optional Models in the Physics Model Selection dialog:

Melting-Solidification Flow Stop

Stops the fluid flow for cells where the accumulated volume fraction of non-flowable phases exceeds the specified Flow Stop Solid Fraction. To prevent a flow deflection in a non-stopped cell next to a stopped cell, the face area weighted average static pressure of all non-stopped cells next to a stopped cell is applied to the stopped cell.

When the Melting-Solidification Flow Stop model is activated, the following model becomes available under Optional Models in the Physics Model Selection dialog:

Flow Stop Mass Compensation

This model keeps the density constant in stopped cells, independently of the equation of state, for all phases and the mixture.

When the flow stop functionality is used in combination with a compressible equation of state (Polynomial Density or User Defined EOS), fluxes through the cell faces cannot compensate for the change in density in stopped cells. This effect causes the fluid mass in the respective cell to change proportional to the density change. Over the simulation time, this change can have a significant effect on the total mass of the solidifying phase.

Material Properties

The following material properties are available for each phase:

Fraction Solid Curve

The fraction solid curve defines the relative solid volume fraction variation with temperature (and absolute pressure for compressible simulations).

The available methods are Polynomial in T, Table(T), Table(T,P), and Linear. The Table(T,P) method applies only to compressible cases.

When you use the Polynomial in T, Table(T), or Table(T,P) method, you specify absolute temperature values. The solidus temperature and liquidus temperature are then assumed to be the minimum and maximum specified values. Both temperatures must exceed the Minimum Allowable Temperature that you set within the Reference Values for the physics continuum. The solid volume fraction is 1 for the solidus temperature, and 0 for the liquidus temperature.

When you use the Linear method, the solid volume fraction changes linearly with temperature between the solidus temperature and liquidus temperature, as specified in Eqn. (2712).

Latent Heat of Fusion

The specific latent heat of fusion $h_{\text{fusion}}$ is the amount of energy in the form of heat that a substance releases or absorbs during a change of state.

Liquidus Temperature

Solidus Temperature

Melting and solidification take place when the material temperature is between the solidus temperature and liquidus temperature. When the material temperature is above the liquidus temperature, the material is entirely in the liquid state. When the material temperature is below the solidus temperature, the material is entirely in the solid state. The solidus temperature and the liquidus temperature can have the same value for pure substances.

These material properties are available only when the Fraction Solid Curve material property uses the Linear method. When other methods are used, the solidus temperature and liquidus temperature are automatically computed as the lower and upper limits of the input that is provided for the respective method.

The liquidus temperature and solidus temperature must be within the Minimum Allowable Temperature and Maximum Allowable Temperature that you set within the Reference Values for the physics continuum.

When using the linear fraction solid curve method, the liquidus temperature must be greater or equal to the solidus temperature. A minimum difference of 0.002 K between both is automatically applied. For other methods, the liquidus temperature must be at least 0.002 K higher than the solidus temperature.

These values are specified as constants.

When the Melting-Solidification Flow Stop model is selected, the following material property is available for each phase:

Flowability Threshold

Defines the Relative Solid Volume Fraction at which the liquid phase loses its ability to flow (that is, sets the Flow Stop Flag of the phase to 1). This threshold depends only on the material. For a pure substance, the default value is 1.0.

However, the fluid flow is stopped in cells only where the accumulated volume fraction of non-flowable phases (that is, those phases that have their Flow Stop Flag set to 1) reaches the Flow Stop Solid Fraction that is specified in the corresponding region.

See Stopping the Flow.

Reference Values

The Reference Values for the physics continuum are:

Minimum Allowable Temperature

Maximum Allowable Temperature

Region Settings

When the Melting-Solidification Flow Stop model is selected, the following are available for Fluid Regions:

Physics Conditions

Flow Stop Option

Activates the Melting-Solidification Flow Stop model for the region.

Physics Values

Flow Stop Solid Fraction

Specifies the solid volume fraction at which the fluid flow is stopped in a cell. This value is a purely geometrical property. Valid values are from 0 through 1. A cell is blocked for flow only where the accumulated volume fraction of non-flowable phases exceeds the specified fraction.

This setting is a property of the continuum, so it depends on all of the phases that are present.

Field Functions

The following field functions become available:

Flow Stop Flag

Lets you visualize the flow stopped cells.

Flow Stop Flag of [phase]

Lets you visualize whether the phase is flowable.

The Flow Stop Flag for a phase gets a non-zero value whenever the relative solid volume fraction of that phase exceeds the threshold value that is specified for the Flowability Threshold property.

See Melting-Solidification Properties.

Relative Solid Volume Fraction of [phase]

Indicates how much of the phase is in the solid state, as defined by Eqn. (2712).

When the Temporary Storage Retained option is selected for the Segregated Flow solver, a number of field functions become available. Some examples are:

Ap Velocity, Apparent Pressure Gradient, Body Force, Density Limiter, Density Recon, d(rho)/d(p), Flow Work Energy Source, Pressure Limiter, Pressure Recon, Pressure-Correction, Rhie-Chow Unsteady Scale, Slip Velocity, Strain Rate Tensor Modulus, Velocity Divergence Imbalance, Velocity-X Correction, Vorticity Tensor Modulus, X-Momentum Residual.