Melting-Solidification Reference

Limits the time-step size to allow for an accurate prediction of the melting/solidification progress.

The Melting-Solidification time-step provider sets the time-step based on the propagation velocity of the melting-solidification interface. This time-step provider is available when the Melting-Solidification model is activated for a VOF phase.

The Melting-Solidification time-step provider carries out volume-weighted smoothing in the same way as the Free Surface CFL time-step provider. See Free Surface CFL Reference.

Table 1. Melting-Solidification Reference
Provided By	Right-click Continua > Physics 1 > Models > Adaptive Time-Step > Time-Step Providers and select New > Melting-Solidification
Example Node Path	Continua > Physics 1 > Models > Adaptive Time-Step > Time-Step Providers > Melting-Solidification
Requires	In the physics continuum: Time: Implicit Unsteady or PISO Unsteady Material: Multiphase Multiphase Models: Volume of Fluid (VOF) Optional Models: Segregated Multiphase Temperature In the Eulerian phase: Material: Liquid Optional Models: Melting-Solidification
Properties	Enable/Disable, Max Condition Limit, Smoothing Steps,Cut-off Percentage. See Melting-Solidification Properties.
Activates	Field Functions	Time Step Condition Melting-Solidification, Melting-Solidification Proposal See Field Functions.

Melting-Solidification Properties

Enable/Disable

See Adaptive Time-Step Provider Common Properties.

Max Condition Limit

The maximum value of the time-step condition. This value is $Φ_{m a x, l i m i t}$ that is used in Eqn. (95).

Smoothing Steps

The number of smoothing steps. This value specifies the number of times that the volume-weighted smoothing operation (Eqn. (94)) is performed.

Cut-off Percentage

Specifies a percentage $p$ of small/bad cells to be ignored by the Adaptive Time-Step model. The prescribed cut-off percentage is used to find the quantile $t_{q} (p)$ , such that for a given $p$ :

Figure 1. EQUATION_DISPLAY

\frac{# [c e l l s : Δ t_{c} \leq t_{q} (p)]}{# [a l l c e l l s]} \approx p %

(100)

The time-step is then set as $t_{q} (p)$ and any local time-steps that the provider proposes below this value are ignored by the model. The range for this property is 0 (default) to 100.

Field Functions

Time Step Condition Melting-Solidification

This value is $Φ = Δ α_{s} + \frac{q}{h_{l a t} m}$ where:

$Δ α_{s}$ is the difference between the current and the old time level value
$h_{l a t}$ is the latent heat of fusion
$m$ is the mass of the melting/solidifying material scaled up as if it occupied the whole control volume
$q$ is the heat conducted towards the phase change interface (for melting) or away from the phase change interface (for solidification).

This time-step condition is based on the assumption that all of the cells in the direction of solid-fluid interface propagation have the same volume as the current cell, and are completely filled with the solidifying phase that exists in the current cell. In this scenario, the current values of heat fluxes and latent heat of fusion give the rough prediction that the solid-fluid interface will propagate about $Φ$ cells.

Melting-Solidification Proposal: The local Melting-Solidification time-step proposal.