Residual Pressure
During the calculation, the diagram of the residual pressure is shown (see the Image 'Diagram of iterations and residual pressure'). It is a logarithmic chart which is also available for inspection after the calculation.
The residual pressure illustrates the progress of the applied pressure during the iterative simulation process. Starting from an initial value of the pressure, the simulation refines the residuals with every iteration, trying to reduce the imbalance of the pressure in the finite volume. The lower the residuals become, the more accurate the solution will be. The simulation terminates when the convergence criterion or the maximum number of iterations has been reached (note that no less than 300 iterations are always carried out). Thus, the residual pressure represents an important tool to judge the convergence of the simulation.
You can control the iterative calculation with the settings in the Simulation Parameters dialog box (see the Chapter 'Simulation Parameters').
To resize the Graph of residuals and iterations, move the window frames accordingly.
Use the [Print] button to print the diagram. The Windows Print dialog box appears where you can specify the printer and its settings.
When you click the [Edit] button, the Graph Settings dialog box is opened. There you can adjust the layout of the Curves, for example.
Note
If the Residual Pressure diagram reveals any problem concerning convergence, you should review the Simulation Parameters (mesh density, convergence criterion) and the Wind Tunnel. For the latter, the default size is set as small as possible to obtain short calculating times. If its length in X-direction is too short (especially the area behind the object), effects of divergence and, thus, oscillating values of residual pressure may arise. In that case, extend the wind tunnel accordingly. For more details, see the Chapter 'Troubelshooting'. In specific cases, however, osciallating results are correct when they are within a consistent bandwidth without increasing. This effect is illustrated in the simulation of a cylinder model at https://youtu.be/A4WaC2V-3uA and explained in FAQ 4731.