## Solver: SRFPimpleFoam Description

srfPimpleFoam is a pressure-based solver designed for transient simulations of incompressible flow. It handles laminar and turbulent, single-phase flows under isothermal conditions, accommodating both Newtonian and non-Newtonian fluids within a Single Rotating Frame (**SRF**). It is an adaptation of the pimpleFoam solver, distinguished primarily by its ability to model fluid flow within a rotating reference frame.

**SRF** is a technique employed for simulating rotating machinery, such as fans, compressors, or turbines, within a fixed simulation domain. This method simplifies the simulation process by eliminating the need to physically rotate the mesh, thus conserving computational resources and time. In this approach, rotational effects are incorporated through boundary conditions and source terms in the governing equations, introducing two additional forces: the Coriolis force and the centrifugal force.

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 both Multiple Reference Frames (**MRF**) and porosity modeling and allows easy integration of passive scalar transport equations and source terms.

`srfPimpleFoam`

proves particularly beneficial for simulations in which the unsteady behavior of fluid is important. Its application is prevalent in the design and analysis of HVAC systems, turbo-machinery, and other rotating equipment, making it a valuable tool in these fields.

## Solver: SRFPimpleFoam Features

**Transient****Incompressible****Single-Phase**

- Low-Speed Flows
- PIMPLE Algorithm
- Subsonic Flow (Ma < 0.3)
- Single Rotating Frame (SRF)

- Laminar and Turbulent (RANS, LES, DES)
- Newtonian and Non-Newtonian Fluid
- Pressure-Based Solver
- Rotating Objects:
- Passive Scalar
- Porosity Modeling
- Source Term (explicit/implicit)
- Solution Limiters:
- Velocity Damping

## Solver: SRFPimpleFoam Application

**HVAC Industry**

- Fans and Blowers

**Turbomachinery**

- Blade Shape Optimization
- Centrifugal Pumps
- Fans
- Mixing Tanks

**Wind Turbines**

- Airflow around Rotating Blades

## Solver: SRFPimpleFoam Incompressible Solvers Comparison

Incompressible Solvers In this group, we have included single-phase, pressure-based solvers for **low-speed flows** with negligible variations in density, applicable for **external** and **internal aerodynamics** (**Ma < 0.3**) and **hydrodynamics**. These solvers use incompressibility features for stability and robustness.

**Incompressible, Stedy-State - Main Solvers**

- simpleFoam steady-state, SIMPLE algorithm
- overSimpleFoam extension of simpleFoam with Overset
- SRFSimpleFoam variant of simpleFoam resolved in SRF

**Incompressible, Transient - Main Solvers**

- pimpleFoam transient, PIMPLE algorithm, DyM
- overPimpleDyMFoam extension of pimpleFoam with Overset, DyM
- SRFPimpleFoam variant of pimpleFoam resolved in SRF

**Incompressible, Transient - Simplified Solvers***

- * Dedicated solvers for simplified scenarios, improve stability and computational efficiency
- ** The PISO algorithm is used for cases with a small Courant number Co < 1

- DyM - Dynamic Mesh
- MRF - Multiple Reference Frame
- SRF - Single Reference Frame
- Overset - also known as Chimera Grid (Method)
- SIMPLE - Semi-Implicit Method for Pressure-Linked Equations
- PIMPLE - merged PISO and SIMPLE
- PISO - Pressure-Implicit Split-Operator

## Solver: SRFPimpleFoam 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 | \(U\) [\(\frac{m}{s}\)] |

Kinematic Pressure \(p/\rho\) | \(p\) [\(\frac{m^{2}}{s^{2}}\)] |

**Kinematic Pressure** It is a pressure normalized by density. To obtain pressure in Pascals [Pa], multiply kinematic pressure by the fluid’s reference density. Read More: Kinematic Fluid Properties

**Derivative Results**

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

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