## Solver: multiphaseInterFoam Description

multiphaseInterFoam is a solver designed for transient simulations involving two or more incompressible, isothermal, and immiscible fluids. It is based on interFoam and extends its capabilities to systems with three or more phases. The solver can handle both laminar and turbulent flows and is compatible with Newtonian and non-Newtonian fluids. Similar to its predecessor, it employs the Volume of Fluid (VoF) method to accurately capture the interface between the fluids.

The solver utilizes the **PIMPLE** algorithm, a combination of the **PISO** and **SIMPLE** methods, for pressure-momentum coupling. This algorithm integrates the strengths of both methods to ensure robust handling of transient flows with large time steps. Under-relaxation techniques are applied to enhance convergence stability. The **MULES** algorithm is used to ensure that phase fractions remain bounded and interfaces sharp. The solver also supports Multiple Reference Frame (**MRF**), porosity modeling and allows for the easy integration of passive scalar transport equations and source terms. It is capable of handling dynamic meshes.

The solver is particularly useful in scenarios requiring the simulation of three or more phases. Examples include environmental flows, where the transport of pollutants is a concern. In the oil industry, it can simulate the mixture of oil, water, and air encountered during extraction processes. Other applications include nuclear reactors and microfluidics.

## Solver: multiphaseInterFoam Features

**Transient****Incompressible****Multiphase - Volume of Fluid (VoF)**

- Multiple Immiscible Fluids
- Dynamic Mesh Motion

- Laminar and Turbulent (RANS, LES, DES)
- Newtonian and Non-Newtonian Fluid
- Pressure-Based Solver
- Rotating Objects:
- Multiple Reference Frames (MRF)
- Rotating Mesh Motion

- Passive Scalar
- Porosity Modeling
- Buoyancy
- Source Term (explicit/implicit)
- PIMPLE Algorithm
- MULES Algorithm
- Solution Limiters:
- Velocity Damping

## Solver: multiphaseInterFoam Application

**Environmental Flows**

- River Pollution - water, sediment and air phases
- Microreactors for Chemical Synthesis - Microfluidics

**Industrial Chemistry**

- Reactors Columns
- Mixing and Stirring Tanks

**Energy Industry**

- Nuclear Reactors
- Oil Extraction

## Solver: multiphaseInterFoam Multiphase - Free Surface (VoF) Solvers Comparison

Free Surface (VoF) Solvers In this group, we have included solvers implementing **Volume of Fluid (VoF)** approach to handle multiple immiscible and miscible fluids and interactions between them.

**Free Surface (VoF) - Immiscible**

- interFoam 2 immiscible fluids, DyM
- multiphaseInterFoam multiple immiscible fluids, DyM
- interIsoFoam* 2 immiscible fluids, isoAdvector* method, DyM

- overInterDyMFoam extension of interFoam with Overset, DyM
- compressibleInterFoam compressible version of interFoam with heat transfer
- compressibleInterDyMFoam compressible version of interFoam with heat transfer and DyM

**Free Surface (VoF) - Miscible**

- interMixingFoam 3 fluids (2 miscible and 1 immiscible), DyM
- twoLiquidMixingFoam** 2 miscible fluids

- * isoAdvector - an alternative approach for interface capturing, MULES method used in other VoF solvers
- ** Solver designed to handle mixtures consisting of multiple fluids within the same phase, such as two gases or two liquids

- VoF - Volume of Fluid
- DyM - Dynamic Mesh
- Overset - also known as Chimera Grid (Method)

## Solver: multiphaseInterFoam Alternative Solvers

In this section, we propose alternative solvers from different categories, distinct from the current solver. While they may fulfill similar purposes, they diverge significantly in approach and certain features.

- multiphaseEulerFoam multiple miscible fluids, Euler-Euler approach

## Solver: multiphaseInterFoam Tutorial

- Analysis involving 3-phase flow of immiscible fluid. The simulation models the movement of mud in water after the gate is opened, considering the presence of air above them.

## Solver: multiphaseInterFoam Results Fields

This solver provides the following results fields:

**Primary Results Fields**- quantities produced by the solver as default outputs**Derivative Results**- quantities that can be computed based on primary results and supplementary models. They are not initially produced by the solver as default outputs.

**Primary Results Fields**

Velocity | \(U\) [\(\frac{m}{s}\)] |

Phase Volume Fraction | \(\alpha\) [\(-\)] |

Hydrostatic Perturbation Pressure | \(p - \rho gh\) [\(Pa\)] |

**Hydrostatic Perturbation Pressure** This value represents the pressure without the hydrostatic component (minus gravitational potential). Read More: Hydrostatic Pressure Effects

**Derivative Results**

Pressure | \(P\) [\(Pa\)] |

Density | \(\rho\) [\(\frac{kg}{m^{3}}\)] |

Vorticity | \(\omega\) [\(\frac{1}{s}\)] |

Courant Number | \(Co\) [\(-\)] |

Peclet Number | \(Pe\) [\(-\)] |

Stream Function | \(\psi\) [\(\frac{m^2}{s}\)] |

Q Criterion | \(Q\) [\(-\)] |

Wall Functions (for RANS/LES turbulence) | \(y^+\) [\(-\)] |

Wall Shear Stress | \(WSS\) [\(Pa\)] |

Turbulent Fields (for RANS/LES turbulence) | \(k\) \(\epsilon\) \(\omega\) \(R\) \(L\) \(I\) \(\nu_t\) \(\alpha_t\) |

Volumetric Stream | \(\phi\) [\(\frac{m^{3}}{s}\)] |

Passive Scalar | \(scalar_i\) [\(-\)] |

Forces and Torque acting on the Boundary | \(F\) [\(N\)] \(M\) [\(-\)] |

Force Coefficients | \(C_l\) [\(-\)] \(C_d\) [\(-\)] \(C_m\) [\(-\)] |

Average, Minimum or Maximum in Volume from any Result Field | \(Avg\) \(Min\) \(Max\) |