Encyclopaedia Index

## Explanatory notes for the post solver output file minires.htm

After the CFD solver has completed a run, a table will pop up. This table is known as "Minires", and it contains useful information about whether or not your solution has converged.

Determining whether a solution has converged can be difficult, and will depend on the nature of the simulation being performed. However, sometimes it is clear that a solution has not converged. Minires reports three key indicators, which will be flagged as yellow if their values are borderline, or red if their values are highly questionable.

The three key indicators are the residual error, the net balance sum, and the maximum correction:

• Residual error: This is the total sum of the error over all the cells for each given equation. This number should be as small as possible. Minires treats values above 1% as borderline, values above 5% as highly questionable. Momentum (U1, V1, W1) can afford to have slightly higher error margins
Variable Red Orange Yellow
P1 >2% 1%-2% 0.1% - 1%
U1, V1, W1 >5% 2%-5% 1% - 2%
TEM1/T3 >2% 1%-2% 0.1% - 1%
C1 >2% 1%-2% 0.1% - 1%
• Net Balance: This is the sum of all sources and sinks (of each variable) into the domain. We would expect the inflow of any variable to be roughly equal to its outflow, and so this value should be close to zero.
• Maximum Correction: For each iteration, the solver calculates new values for every cell in the grid. Large changes in values for a particular cell between subsequent iterations can destabilise the solver. At convergence, the change in value (i.e. the correction between iterations) should be a small fraction of the value in a cell. The maximum correction is the largest correction made for any cell in the final iteration. It should be small compared to the field value at the given location.
• Location: shows the cell containing the largest correction.