The CFD calculation process is iterative and is considered to have completed once ‘convergence’ has been achieved. The main indicator for convergence is the point at which the finite difference equations for all cells are satisfied by the current values of the appropriate dependent variables. However, it can be very useful in many cases to monitor the variation of the dependent variables at specific locations throughout the calculation domain in order to observe the point at which they stabilise. It may be acceptable, in many cases, to terminate a calculation as soon as the dependent variables have achieved adequate stability but before the residuals have arrived at their defined termination values
When a project is first created, a default central cell monitor point is automatically added to the domain. The Define CFD monitor points tool enables you to identify up to ten cells throughout the calculation domain at which you want to monitor the variation of the calculated variables.
After selecting the Define CFD monitor points tool, the cell monitor screen is displayed which includes the model view together with a cell selection frame, perpendicular to the currently selected axis. You can select a plane along the current axis by moving the mouse cursor across the model in the direction of the axis. To change the axis, click on the required axis on the axis selector tool, which is located at the top right of the screen:
After selecting the required axis, move the cell selection frame along the axis, and then click the mouse button to select a plane at the required distance along the axis. A cell selection grid is then displayed in the selected plane allowing you to move the mouse cursor to the required cell in that plane:
After moving the mouse cursor to the required cell, click the mouse button to display the cell monitor data panel at the bottom left of the screen.
The following settings are available on the cell monitor data panel:
This control is only active if you have selected a cell for which a monitor point has already been defined. The following options are available:
Enter a name for monitor point - this is used later when selecting data for the monitor point to be displayed on the CFD Calculation Options dialog.
After changing the required settings, click on the ‘Apply changes’ button to update the selected cell. You can cancel the Define CFD monitor points command by pressing the <Esc> key or by selecting another tool.