## Solver: buoyantPimpleFoam Description

buoyantPimpleFoam is a pressure-based solver designed for transient simulations of compressible flows. It handles laminar and turbulent, single-phase flows involving heat transfer, radiation, natural convection, and buoyancy-driven scenarios.

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 Frame (MRF) and porosity modeling and allows easy integration of passive scalar transport equations and source terms.

It finds extensive use across various industries, including HVAC (Heating, Ventilation, and Air Conditioning) system designs, and electronic devices where thermal management is of interest. In the energy sector, its application in analyzing natural convection in solar collectors and nuclear reactors contributes to the development of efficient and safe energy solutions.

## Solver: buoyantPimpleFoam Features

**Transient****Compressible****Single-Phase**

- Buoyancy-driven Flow
- Heat Transfer
- Heat Source
- Radiation

- Laminar and Turbulent (RANS, LES, DES)
- Equation of State Models
- Pressure-Based Solver
- Rotating Objects:
- Multiple Reference Frames (MRF)

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

## Solver: buoyantPimpleFoam Application

**HVAC**

- Ventilation
- Water Heating
- Room Heating
- Natural and Forced Convection

## Solver: buoyantPimpleFoam Heat Transfer Solvers Comparison

Heat Transfer Solvers In this group, we have included solvers that are designed to model: **Heat Transfer**, **Radiation**, **Natural** and **Forced Convection**, **Conjugate Heat Transfer (CHT)**.

**Heat Transfer, Single Fluid**

- buoyantSimpleFoam steady-state, compressible, buoyancy-driven flow
- buoyantPimpleFoam transient, compressible, buoyancy-driven flow

**Heat Transfer, Single Fluid - Boussinesq**

- buoyantBoussinesqSimpleFoam steady-state, incompressible, buoyancy using Boussinesq approximation
- buoyantBoussinesqPimpleFoam transient, incompressible, buoyancy using Boussinesq approximation

**Heat Transfer, Single Solid**

- laplacianFoam steady-state and transient, thermal conduction in solid
- overLaplacianDyMFoam extension of laplacianFoam with Overset

**CHT, Multiple Fluids / Solids**

- chtMultiRegionSimpleFoam steady-state, compressible, arbitrary fluid and solid regions
- chtMultiRegionFoam transient, compressible, arbitrary fluid and solid regions

- CHT - Conjugate Heat Transfer
- MRF - Multiple Reference Frame
- Overset - also known as Chimera Grid (Method)

## Solver: buoyantPimpleFoam 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.

- rhoPimpleFoam pressure-driven flow, negligible buoyancy

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

Temperature | \(T\) [\(K\)] |

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

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**

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

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

Mach Number | \(Ma\) [\(-\)] |

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 | \(WSS\) [\(Pa\)] |

Wall Heat Flux | \(\phi_q\) [\(W/m^2\)] |

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