The Multi-purpose solver can be a great choice if one wants to perform multiphase simulations involving the time-dependent behavior of two fluids using the VOF (Volume of Fluid) method.
Animation 1: Water spillway in canal
The VOF solver employs a proprietary, higher-order reconstruction scheme for the interface modeling, along with a robust binary tree-based mesher, which helps in fast mesh generation of complicated geometries and stable convergence over a wide range of problems.
The following advantages make the Multi-purpose solver a great choice for multiphase simulations:
Fast multiphase analysis.
Real fluid properties.
Stable convergence for intricate geometries with automatic CFL adjustment.
Multiphase simulations are inherently transient. Hence, the Time dependency will switch to Transient when the Multiphase option is toggled on. One can also change the Time dependency to Transient first and then toggle on Multiphase. These can be done within the global settings for the Multi-purpose analysis.
Figure 1: Toggling on the Multiphase feature within the Multi-purpose solver in SimScale
The user needs to specify the number of phases involved in the multiphase simulation.
Initial conditions
Initial conditions define the values which the solutions fields will be initialized with. The phase fraction can be initialized globally or for a specific region as a subdomain for all the phases involved.
Figure 2: Phase fraction initialization inside a subdomain for multiphase simulations
Phase fraction sum
The solver will throw an error if the sum of the phase fractions does not add up to one. Please ensure the values of the associated phases add up to one under Initial conditions > Phase fractions > Subdomains.
View the following validation case to understand the setup in a multiphase simulation:
