PIMPLE Module

Load PIMPLE in the run control file:

loadModule: pimple

PIMPLE Algorithm

PIMPLE combines SIMPLE outer iterations with PISO pressure–momentum correctors. Each outer iteration solves the predictor equations and then runs the selected correctors, as shown below.

PIMPLE predictor and corrector sequence.

Control File Setup

The outer iteration repeats the predictor and all correctors. Use the standard outer convergence controls and maxIterationsPerTimeStep to bound its work. numCorrectorIterations selects the number of pressure–momentum correctors (default one, minimum one). Two correctors are recommended for cavitation.

Use explicitCorrectorEquations to select additional equations for the corrector step (default none):

numCorrectorIterations: 2
explicitCorrectorEquations: <cavitation, energy, turbulence>

cavitation includes the vapor and NCG mass-fraction equations. energy includes the temperature, total enthalpy, or total energy equation selected by form in energyEquationOptions. With species transport, total enthalpy and total energy correctors include species enthalpy diffusion unless energyEquationOptions contains noSpeciesEnthalpyDiffusion. Species composition remains fixed within the pressure–momentum correctors.

turbulence includes the k and omega equations for menterBSL, menterSST, and menterSST2003, including their _m, _V, _Vm, _KL, and _KLm variants. Explicit turbulence correction requires turbulent flow with viscous transport and Cartesian coordinates. It does not support rhok, crossDiffusion=implicit, or wallFunction boundaries. Omit turbulence to solve turbulence only in the outer predictor equations.

correctorVolumeFluxForm selects old or new volume flux in the corrector (default new).

Pressure stages are controlled separately by numStages in pressureCorrectionEquationOptions (default one). Each stage solves the same corrector pressure equation with an updated deferred geometric contribution. The final stage supplies the total correction applied to pressure, velocity, and face flux. Increasing numStages does not add momentum correctors.

pressureCorrectionEquationOptions: <linearSolver=HYPRE,numStages=2>

numStages must be at least one. The PIMPLE pressure corrector supports HYPRE, FSGS, LSGS, and PETSC; SGS is rejected. The optional correctorMaxLinearSolverIterations overrides the pressure linear-iteration limit inside correctors only; its default -1 uses the ordinary pressure option. Momentum-interpolation forms newest and Denner are not supported by the PIMPLE corrector; select old or new for the qualified forms.

With diagnostics: <nonlinearConvergence,linearSolverResidualRatio>, each corrector pressure solve also prints a PCRES line containing the physical cycle, outer iteration, corrector, pressure stage, RHS L1 norm, solved b-Ap L1 norm, and maximum absolute cell defect. The RHS norm measures the incoming pressure-equation imbalance; the solved defect measures linear-solver accuracy. These diagnostics do not change the outer convergence criteria.

If a poor initial pressure field causes instability, run several timesteps with SIMPLE before restarting with PIMPLE.