## Solver: interIsoFoam Description

interIsoFoam is a solver designed for transient simulations of two incompressible, isothermal, and immiscible fluids. It handles both laminar and turbulent flows, accommodating Newtonian and non-Newtonian fluids. Similar to interFoam, which serves as the foundation for this solver, it employs the Volume of Fluid (VoF) approach to accurately capture the interface between fluids (e.g., water and air).

The solver uses the **isoAdvector** scheme for sharp interface reconstruction, replacing the interface compression technique with the MULES limiter implemented in interFoam. The **isoAdvector** scheme utilizes the concept of isosurfaces to calculate more accurate face fluxes for cells containing the interface, significantly reducing interface dissipation and offering improvements in turbulence modeling around the free surface.

For pressure-momentum coupling, the solver employs the **PIMPLE** algorithm (a merger of **PISO** and **SIMPLE** methods), which combines the strengths of both to ensure robust handling of transient flows with large time steps. This method is enhanced by under-relaxation techniques to maintain convergence stability and supports Multiple Reference Frame (**MRF**) and porosity modeling. It also allows for the easy integration of passive scalar transport equations and source terms, and is capable of handling dynamic meshes.

Applications for the solver are similar to those of interFoam, making it suitable for ship design and optimization in the marine industry, sloshing simulation, and mixing in stirring tanks for the transportation industry. Due to its significant improvements in interphase reconstruction, the solver is ideal for studying the detailed behavior of rising bubbles in low hold-up particle–liquid suspension systems (automotive industry) or multiphase processes in reactors (chemical industry). However, the computational cost might be higher than the standard algorithm used for interface reconstruction due to the complexity of the **isoAdvector** scheme.

## Solver: interIsoFoam Features

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

- 2 Immiscible Fluids
- Iso Advector method
- 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
- Solution Limiters:
- Velocity Damping

## Solver: interIsoFoam Application

**Marine Industry**

- Planing Ship Hulls & Ship Motion (e.g. Ship hull)
- Propeller Performance
- Sloshing in Tanks (e.g. Sloshing Tank)
- Ship Motion under Different Conditions with Dynamic Mesh Feature
- Offshore Structures Loads
- Calm-water Air Gap under Offshore Platform Decks
- Wave Loading on Profiles
- Floating Objects
- Wave Energy Absorbers
- Point Absorbers

**Dams & Spillways**

- Spillway Analysis
- Fishways Designing
- Weir Flows
- Dam Breaks Scenarios (e.g. Dam break)
- Hydro Plants
- Hydraulic Energy Losses Predictions
- Pipe and Channel Flows

**Automotive industry**

- Sloshing Effects in Tanks (e.g. Sloshing Tank)
- Fuel Level Indication with Moving Objects 6 DoF (Six Degree of Freedom) Model
- Low Hold-Up Particle–Liquid Suspension Systems

**Aerospace Industry**

- Sloshing Effects in Fuel Tanks

**Chemistry and Biotechnology**

- Active Mixers with Mechanical Devices to Facilitate Mixing (e.g. Mixing tank)
- Static Mixers
- Chemical Reactors

**Injection Molding**

- Simplified Injection Molding Process with non-Newtonian Fluids (e.g. Injection Molding)

**Rotating Machinery**

- Turbines, Industrial Mixers, Stirred Tank Reactors
- Pumps, Valves, Hydraulic Turbines
- Marine Propellers (e.g. Propeller)

## Solver: interIsoFoam 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: interIsoFoam 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 | \(Avg\) \(Min\) \(Max\) |