Welcome to the Getting Started with GeoStudio video series.
In this tutorial, we will be looking at tools to help view node convergence in the Results window.
To review the convergence settings of your analysis, click on the KeyIn Project button in the Define window.
In this analysis, we are conducting a water transfer process, so we will look at the water tab.
Here, we see the current convergence settings. In this case, we will keep the default settings for iteration and under relaxation criteria.
More information on these criteria is available in the Convergence and UR tutorial video.
We will use a low number of iterations at first.
Now we will start the Solve Manager for this analysis.
Once solved, we can see the resulting pore-water pressure contours for this analysis.
To ensure convergence, we will look at the convergence graph, under Draw graph.
As shown by the graph, the analysis has stopped at five iterations with 92 pressure head nodes that have not reached convergence.
Now in order to view which of the nodes in the mesh could not reach convergence, we will go to View preferences
and turn on the Node convergence option.
Now I can see red X's in grey circles painted on the mesh.
The red X's indicate nodes that have not converged because they did not meet the significant figure requirement.
As stated in the Convergence and UR video, the significant figure criteria determines if the primary variable, as in
this case the pressure head, from two successive iterations is the same within the specified tolerance.
The grey circles indicate nodes whose differences in the primary variable with iteration is less than the minimum difference,
which remember is used to filter out numerical noise.
Next we will use another tool available in the Results view that helps review node convergence. We will go to View
result information, which will open up a new window that will display result data for selected mesh components.
First, we will look at the result information for a converged node that has neither the red X nor the grey circle.
Here, we see the resulting pressure head delta value
is less than the minimum pressure head difference criteria
of 0.005 m.
Since this node converged, the significant digits value is not calculated
and a value of eight is automatically applied.
Next we will choose a node with a grey circle.
In this case, we see the pressure head delta information does not meet the minimum pressure head difference criteria of 0.005 m,
so the significant digits value is calculated, resulting in the value of 2.
This means that this node meets the significant digits value criteria.
Lastly, we will look at the result information for a node with a red X. Here, the pressure had delta did not meet the convergence criteria again, so the
significant digits value is calculated. In this case, however,
the significant digits criteria of two was not met, causing the red X to be painted on the node.
Now we will return to the Define view to change our convergence settings.
We will go back to KeyIn Project and the water tab
and increase our number of maximum iterations to 50.
Now we will restart the Solve Manager and rerun the analysis.
Once solved, we can see the pore-water pressure contours in the Results view, but this time there are no red X's present on the mesh.
To confirm that convergence was reached, we will return to the convergence graph under Draw graph.
As shown by the graph, the analysis was able to reach convergence based on the current convergence criteria after 10 iterations.
To summarize, the use of the node convergence option in the Results window can help the user
determine what area of the model domain is not meeting the convergence criteria.
Please refer to the Convergence and UR video for more information on convergence criteria.
Thank you for watching.