Required field
Required field
Required field

# How to Set Up Simulation Control Parameters in a Steady State CFD Analysis?

## Simulation control

In Simulation control, the user can adjust global parameters that have a direct impact on the simulation.

Often times the user will have to change some of the inputs. So let’s go through each one of them.

## Simulation control parameters

### End Time & Delta T

End time and Delta t control the number iterations performed by the algorithm.

For steady-state, they do not hold a physical meaning. The number of iterations to be performed in the simulation is given by:

$$Iterations = {EndTime \over Delta t}$$

For simplicity, keep Delta t at 1. In this case, End time represents the number of iterations.

### Write Control & Write Interval

These two parameters are related to the number of data sets that will be written.

A normal approach is to set Write interval to be equal to End time. In this case, only the converged data set is saved.

Moreover, it is possible to change the write frequency by changing Write interval. But keep in mind that each data set will take memory from the machine.

### Number of Processors

Based on the job size, the algorithm automatically chooses the number of processors that will be used. Academic and professional plans allow the user to choose the number of processors.

### Maximum Runtime

Maximum runtime represents real clock time in seconds for the simulation to run. In case the iterations are not over yet, an error message appears:

When this error occurs, the user can resume the run by clicking on the double arrow icon above.

### Potential Foam Initialization

Potential foam is a function that initializes velocity and incompressible flux fields [1]. It is able to improve stabilization and convergence.

This function is valuable for cases where the user specifies velocity boundary conditions. Avoid using it for pressure-driven flows and convective heat transfer cases, as it can generate unphysical results.

### Decompose Algorithm

In order to run the case on multiple cores, the computational domain has to be decomposed. Scotch doesn’t require further parametrization and is default [2].

References

[1] https://www.openfoam.com/documentation/guides/latest/doc/guide-applications-solvers-basic-potentialFoam.html Date of access: 28/02/2020.

[2] https://www.simscale.com/docs/content/simulation/simulationControl/decompositionAlgorithm.html Date of access: 28/02/2020.

Last updated: July 18th, 2020