# interMixingFoam

Source: https://help.sim-flow.com/solvers/inter-mixing-foam
Last updated: 2026-10-14

## Description

interMixingFoam is a solver specifically designed for transient simulations involving three incompressible, isothermal fluids, with two of them being miscible. It accommodates both laminar and turbulent flows, handling a range of fluids, including both Newtonian and non-Newtonian ones. It utilizes the Volume of Fluid (VoF) approach for capturing the interface between the fluids accurately. The solver is suited to cases where the particular interest is in the behavior of the interface between two fluids (e.g. water and air). Therefore, it extends the capabilities of the [interFoam](https://help.sim-flow.com/solvers/inter-foam) solver. This solver is ideal for analyzing the mixing of two fluids in open tanks, and it is commonly utilized for analyzing the mixture of two phases, while omitting the presence of a third immiscible phase.

The solver uses the **PIMPLE** (merged **PISO-SIMPLE**) algorithm for pressure-momentum coupling. This algorithm leverages the strengths of both PISO and SIMPLE methods for pressure-velocity coupling, ensuring robustness in handling transient flows with large time steps. This approach is supplemented by under-relaxation techniques to secure convergence stability. It supports Multiple Reference Frames (MRF) and porosity modeling and allows easy integration of passive scalar transport equations and source terms. The solver handles dynamic meshes.

It is applicable for scenarios where three fluids are considered. An example can be environmental flows and silt water flow in rivers. In the chemical industry, it can be applied for stirring processes and open mixing tanks.

## Features

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

- 3 Fluids (2 Miscible and 1 Immiscible)
- Mixing
- Dynamic Mesh Motion

- Laminar and Turbulent (RANS, LES, DES)
- Multicomponent (mixture)
- 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

## Application

**Environmental**

- Silt Water in a River

**Chemical**

- Stirring Processes including Two Miscible Fluids
- Open Mixing Tanks

**Automotive**

- Mixing of Fuel Components in Engine

## Multiphase - Free Surface (VoF) Solvers

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

**Free Surface (VoF) - Immiscible**

- [interFoam](https://help.sim-flow.com/solvers/inter-foam) 2 immiscible fluids, DyM
- [multiphaseInterFoam](https://help.sim-flow.com/solvers/multiphase-inter-foam) multiple immiscible fluids, DyM
- [interIsoFoam*](https://help.sim-flow.com/solvers/inter-iso-foam) 2 immiscible fluids, isoAdvector* method, DyM

- [overInterDyMFoam](https://help.sim-flow.com/solvers/over-inter-dym-foam) extension of interFoam with Overset, DyM
- [compressibleInterFoam](https://help.sim-flow.com/solvers/compressible-inter-foam) compressible version of interFoam with heat transfer
- [compressibleInterDyMFoam](https://help.sim-flow.com/solvers/compressible-inter-dym-foam) compressible version of interFoam with heat transfer and DyM

**Free Surface (VoF) - Miscible**

- [interMixingFoam](https://help.sim-flow.com/solvers/inter-mixing-foam) 3 fluids (2 miscible and 1 immiscible), DyM
- [twoLiquidMixingFoam**](https://help.sim-flow.com/solvers/two-liquid-mixing-foam) 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)

## 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](https://doc.openfoam.com/2312/tools/processing/solvers/algorithm-p-rgh)

**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 | \(Avg\) \(Min\) \(Max\) |