Setting Up Monitoring Plots
Create plots to monitor the progress of the simulation.
Since the simulation is starting with no boiling and with little vapor, the final residuals can be many orders of magnitude different from the initial levels.
To help determine when the simulation has converged, you can also monitor the progress of the following:
- maximum velocity
- maximum and minimum temperature
- maximum volume fraction
- mass balance
Any of these plots can be set up individually by applying the Create Monitor and Plot from Report action to selected groups of various reports operating on relevant fields or field functions.
For convenience, the complete set of monitoring plots for this tutorial can be set up by running a macro.
To set up the monitoring plots:
- Select .
- In the Open dialog, navigate to your working directory and select wb_setupMonitorPlots.java.
- Click Open to run the macro.
In this tutorial, the maximum and minimum plots are expected to confirm that the velocities and temperatures remain physically plausible throughout the convergence history. This result is due to the strategy of ramping up the power gradually as the flow field is established.
In more difficult or unfamiliar cases, maximum and minimum plots can be helpful to identify the first signs of when a simulation is starting to get out of hand and can need adjustments to relaxation factors.
The Mass Balance plot tracks three quantities, as follows:
-
LiquidMassFlow, which computes the mass outflow of liquid less the mass inflow of liquid.
-
VaporMassFlow, which computes the mass outflow of vapor less the mass inflow of vapor.
-
NetEvaporationRateReport, which is constructed from the expression $WallEvaporationRateReport + $BulkEvaporationRateReport - $BulkCondensationRateReport.
where:
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BulkCondensationRateReport is the volume integral of the positive part of the interior IPMT rate from the vapor phase to the liquid phase.
-
BulkEvaporationRateReport is the volume integral of the negative part of the interior IPMT rate from the vapor phase to the liquid phase.
-
WallEvaporationRateReport is the surface integral of minus the wall IPMT rate from the vapor phase to the liquid phase.
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The IPMT (Interphase Mass Transfer) rate is defined to be positive where mass is transferred from the second (dispersed) phase to the first (continuous) phase that is specified under the Eulerian Continuous-Dispersed phase interaction. For this tutorial, this definition means that a positive IPMT rate indicates condensation, and a negative value indicates evaporation.
On convergence, the mass balance is expected to be obeyed for each phase, at least to some finite precision:
- LiquidMassFlow + NetEvaporationRateReport = 0
- VaporMassFlow - NetEvaporationRateReport = 0