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SpectraSim Documentation
Parameter · 07 Run Settings

Pressure correctors

simulation_control.transient.n_correctors Step 07 · Run Settings

The number of pressure corrections (PISO correctors) the transient incompressible solver makes in each outer corrector of a time step.

Last updated

Theory

Within each outer corrector, the transient incompressible solver solves the momentum equation once and then the pressure equation NcorrN_{corr} times, each time correcting the velocity and the fluxes with the new pressure, equation (1) (OpenFOAM user guide, 2026). Each pressure solve is itself repeated for the non-orthogonal correction (Non-orthogonal correctors).

The PISO algorithm needs at least two correctors to make the velocity consistent with the pressure within a step. More correctors improve the pressure-velocity coupling at a cost of one pressure solve each.

Equations

U(m)=H(U(m−1))aP−∇p(m)aP,∇⋅(∇p(m)aP)=∇⋅(H(U(m−1))aP),m=1…Ncorr\mathbf{U}^{(m)} = \frac{\mathbf{H}(\mathbf{U}^{(m-1)})}{a_P} - \frac{\nabla p^{(m)}}{a_P}, \qquad \nabla\cdot\left(\frac{\nabla p^{(m)}}{a_P}\right) = \nabla\cdot\left(\frac{\mathbf{H}(\mathbf{U}^{(m-1)})}{a_P}\right), \qquad m = 1 \ldots N_{corr}
(1)
wheremeaningunit
U(m)\mathbf{U}^{(m)}Velocity after pressure corrector mmm/s
H\mathbf{H}Off-diagonal and source part of the discretised momentum equationm/s²
aPa_PDiagonal coefficient of the momentum matrix1/s
p(m)p^{(m)}Kinematic pressure of corrector mmm²/s²
NcorrN_{corr}Pressure correctors (this setting)-

Default and rule

Default
2
Rule

2.

Source

This is the program's default, the common PISO choice; other values have not been assessed in the program's validation runs. The PISO corrector sequence is described in (OpenFOAM user guide, 2026).

Valid range 1 to 6

Values

1 to 6. Each corrector costs one pressure solve per outer corrector.

References 1

  1. OpenCFD Ltd. (2026). OpenFOAM user guide. openfoam.com. Web page