The Subsonic 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 Subsonic 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 subsonic analysis.
Figure 1: Toggling on the Multiphase feature within the Subsonic 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.
Applications of Subsonic Multiphase
AEC and Hydraulic engineering
Assess dynamic forces and free surface wave patterns on hydraulic structures like radial gates, tunnel chutes & spillways
Hydraulic design of stormwater drainage culverts & irrigation systems
Dam break analysis
Assessing approach conditions on pump sumps & inlet geometry effects on reservoir mixing
Open channel flows
Animation 2: Flow visualization and forces on dam gates
Industrial equipment
3D flow patterns and mixing efficiency in industrial mixers
Separation efficiency and phase fraction distribution in fluid separation systems
Mixing and air flow rate analysis in aeration beds
Design of desalination equipment (water-brine simulations)
Fluid behavior in venturi scrubbers and gas mixers
Animation 3a: Mixing tank baffle design comparison: Without baffles
Animation 3b: Mixing tank baffle design comparison: With baffles
Rotating machinery
Performance analysis of hydraulic turbines
Mixing efficiency and flow behavior in Rushton turbines, industrial mixers & stirred tank reactors
Performance and flow analysis of liquid-gas flows through rotodynamic pumps in O&G, food processing, water transportation, etc.
Flow analysis and thrust computations for marine propellers
Animation 4: Purging water-primed pump with the working fluid, oil
Flow control
Pressure drops and hydraulic loss assessment through subsea piping systems
Flow capacity assessment of multiphase mixtures through different types of valves
Tank filling and surge tank analysis
Fuel injectors, coolant flows through HVAC systems and oil-air flows through engine chambers
Flow rate and range analysis of fire fighting equipment
Animation 5: Pressure and filling progress during the valve priming process
