Use a Parametric Sweep (
) study to find the solution to a sequence of stationary or time-dependent problems that arise when you vary some parameters of interest. The parametric sweep can include multiple independent parameters directly for a full multiparameter sweep (solve for the first value of the first parameter combined with all values of the second parameter, then the second value of the first parameter combined with all values of the second parameter, and so on, or use a specified combination of parameter values). You can also add more than one
Parametric Sweep node to create nested parametric sweeps. The program then treats the parametric sweeps as a “nested for-loop” and indicates the nested structure using indentations of the
Parametric Sweep nodes’ names.
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See Table Surface for information about how to plot the variation of some quantity as a function of two parameters as a 2D surface plot where you vary two parameters and fix the others.
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The Settings window has the following sections:
Use the Sweep type list to specify the type of sweep to perform. The
Specified combinations type (the default) solves for a number of given combinations of values, while the
All combinations type solves for all combinations of values. Using all combinations can lead to a very large number of solutions.
Use the table with Parameter name,
Parameter value list, and (optional)
Parameter unit to specify parameter names, values, and units for the parametric solver. Use the
Add button (
) to add a row to the table. Each row has one parameter name, a corresponding parameter value list, and an optional unit. The unit becomes orange if the unit that you specify does not match the unit given for the parameter where it is defined. For the
Specified combinations sweep type, the list of values must have equal length. When you click in the
Parameter value list column to define the parameter values, you can click the
Range button (
) to define a range of parameter values. The parameter unit overrides the unit of the global parameter. If no parameter unit is given, parameter values without explicit dimensions are considered dimensionless.
If more than one parameter name have been specified, the lists of parameter values are interpreted as follows: Assume that the parameter names are p1 and
p2, and that
p1 has the list 1 3 and
p2 has the list 2 4. For the
Specified combinations sweep type, the solver first uses
p1 equal to
1 and
p2 equal to
2. Thereafter, it uses
p1 equal to
3 and
p2 equal to
4. And when the sweep type is
All combinations, the solver uses the following order for the parameter combinations: 1 2, 1 4, 3 2, and 3 4.
An alternative to specifying parameter names and values directly in the table is to specify them in a text file. Use the Load from File button (
) to browse to such a text file. The program appends the read names and values to the current table. The format of the text file must be such that the parameter names appear in the first column and the values for each parameter appear row-wise with a space separating the name and values, and a space separating the values. Click the
Save to File button (
) to save the contents of the table to a text file (or to a Microsoft Excel Workbook spreadsheet if the license includes LiveLink™
for Excel®).
Select the Plot check box to allow plotting of results while solving. Then select what to plot from the
Plot group list. The software plots the data set of the selected plot group as soon as the results become available.
Use the Probes list to select probes to update during the parametric sweep. The default is
All, which selects all probes for plotting and tabulation of probe data. Select
Manual to open a list with all available probes. Use the
Move Up (
),
Move Down (
),
Delete (
), and
Add (
) buttons to make the list contain the probes that you want to see results from while solving. Select
None to disable probe updating for parametric sweep. Note that the control of tables and plot windows is done using the probe settings.
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If a probe is updated on the Parametric Sweep level and also through another solution process (for example, a time-dependent simulation) this probe is not updated at the Parametric Sweep level. When the probes themselves (not the probe expression) depend on model parameters, the update of these probes is only correct for parameter sweeps that are done through outer parametric sweeps (not by a parametric solver). Outer parametric sweeps are performed by a Parametric node under Job Configurations. COMSOL Multiphysics currently does not autodetect model parameters in probes, so you might want to select Off from the Use parametric solver list in the Study Extensions section for the Parametric Sweep study node.
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Select the Accumulated probe table check box to activate the accumulation of probe updates for both the variation on the solver level (time, frequency, and so forth) and on the parametric sweep level. Use the
Output table to select where to put the data. Select the
Use all probes check box if all the model probes should be accumulated in the table. If not selected, the probes selected by the
Probes selector are used.
You can use the Memory settings for jobs and the
Keep solutions in memory list to control how to store the solutions from the individual parametric sweep solutions. Select
All to store all the parametric sweep solutions in memory, or select
Only last to store only the last solution from the parametric sweep. If you select
Only last and the parametric solver is used, all solutions are kept in memory. When only the last solution is stored, you can also select the
Save each solution as model file check box. It stores the separate parametric sweep solutions and their corresponding models in separate MPH-files. Enter a filename in the
Filename field or click
Browse to choose a name and location for the model files. You can also use probes to collect some solution values of interest during the sweep rather than storing all solutions, which can save memory and solution time.
From the Use parametric solver list, select one of the following options:
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Automatic (the default) to generate a Parametric job configuration, unless the problem and parameters are such that the parametric sweep can be realized through a Stationary Solver with a Parametric solver subnode ( ), which is more efficient.
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Off to always generate a Parametric job configuration.
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Stationary for information about the continuation parametric solver versus parametric sweeps.
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