COMSOL 6.2 - Stationary Source Sweep

Stationary Source Sweep

For the Electrostatics, the Electrostatics, Boundary Elements and the Electric Currents interfaces there is a special study step for efficient calculation of capacitance and resistance matrices respectively. The (

) identifies all terminals (domain or boundary) in the model and excites them one at a time using a fixed charge or current (overriding the settings on the features). While one Terminal is excited, the others will be floating with zero net charge/current.


	To get a proper matrix definition, at least one Ground node should be specified in the model. This is particularly important as the Stationary Source Sweep does not add any constraint on the electric potential.

Matrix Output

The resulting potential values at the terminals are used to extract one of the lumped matrices according to the following table.


physics	Base Lumped Parameter matrix
Electrostatics & Electrostatics, Boundary Elements	Inverse Maxwell capacitance matrix
Electric Currents	Resistance matrix

During postprocessing, other matrices can be produced via the . The settings for Global Matrix Evaluation has a section that allows for the output of the Maxwell capacitance matrix or the mutual capacitance matrix.


	If the Generate default plots check box on the Study node is enabled, default Global Matrix Evaluation nodes for matrix output are generated.

Solver Selection

The Stationary Source Sweep is optimized for solution speed. It works best with a direct solver as the LU decomposition has to be performed only once, followed by back substitution for the multiple source excitations (multiple right-hand sides). For 3D models, the Stationary Source Sweep generates both an iterative and a direct solver. The former will be selected if the model is having a large number of elements; that is, a number that is above a built-in threshold. For hardware with sufficiently large RAM, it is recommended to manually switch to the direct solver.


	For 3D models involving the Electrostatics, Boundary Elements physics, direct solvers scale poorly with problem size so some caution is recommended.

Voltage Output

With unit charge feeding the absolute value of the electric potential is difficult to predict. For this reason there is an auxiliary global variable — for example, es.VexcTerm — that represents the value of potential of the excited terminal. The default potential plots will typically show the electric potential scaled by this value.

Compatibility with Other Study Types

Combining the Stationary Source Sweep with the study node should only be done after careful consideration. If you need to perform more general parameter sweeps, it is often more appropriate to activate the manual terminal sweep in the settings of the main physics node and set up Parametric Sweeps manually. Other study nodes will work with Stationary Source Sweep as it was a standard Stationary (parametric) study. In particular, this is valid also for Optimization and Sensitivity studies.