The PISO (Pressure Implicit with Splitting of Operators) is an efficient method to solve the Navier-Stokes equations in unsteady problems. The main differences from the SIMPLE algorithm are the following[1]:
- No under-relaxation is applied.
- The momentum corrector step is performed more than once.
The algorithm can be summed up as follows:
- Set the boundary conditions.
- Solve the discretized momentum equation to compute an intermediate velocity field.
- Compute the mass fluxes at the cells faces.
- Solve the pressure equation.
- Correct the mass fluxes at the cell faces.
- Correct the velocities on the basis of the new pressure field.
- Update the boundary conditions.
- Repeat from 3 for the prescribed number of times.
- Increase the time step and repeat from 1.
As already seen for the SIMPLE algorithm, the steps 4 and 5 can be repeated for a prescribed number of time to correct for non-orthogonality.[1]
References
[1] The PISO algorithm in OpenFOAM. http://openfoamwiki.net/index.php/The_PISO_algorithm_in_OpenFOAM. MAY 2, 2011