Support Knowledge Base

Understanding the Fully Coupled vs. Segregated approach and Direct vs. Iterative linear solvers

Solution Number: 1258 Versions: All versions

How, and why, switch between a fully coupled and a segregated approach to solving a multiphysics model? How, and why, switch between the direct and iterative linear system solver? ## Fully Coupled versus Segregated ...

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Solving electromagnetic heating models with high-frequency loads

Solution Number: 1257 Versions: All versions

I am solving a Multiphysics problem involving electromagnetics and heat transfer. The electromagnetic fields are varying at a constant frequency, and the period is very short compared to the timespan over which the ...

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Reducing the amount of solution data stored in a model

Solution Number: 1255 Versions: All versions

My models contain a lot of solution data, and I do not want my file sizes to get too large, it takes a lot of disk space. What can I do to reduce file size? Will this reduce the time it takes to solve the model? File ...

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Controlling the Time Dependent solver timesteps

Solution Number: 1254 Versions: All versions

I am solving a transient model and changed the stepsize in the Times: field in the Study Settings, but the solver is still taking exactly the same timesteps. It seems the timesteps that the solver is taking are not ...

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Solving Wave-Type Problems with Step Changes in the Loads

Solution Number: 1244 Applies to: COMSOL Multiphysics Versions: All versions

I am solving a transient model and am expecting the solution to oscillate over time in response to step changes in the loads. How should I set up such a model? What solver changes should I make? Certain models will ...

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Running parametric sweeps, batch sweeps, and cluster sweeps from the command line

Solution Number: 1250 Versions: All versions

This solution describes how to launch a parametric sweep, a batch sweep, or a cluster sweep simulation in COMSOL Multiphysics® from the command line. ## Short Summary Model methods are presented as a concept to ...

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Solution number is out of range

Solution Number: 1249 Applies to: COMSOL Multiphysics Versions: 5.3a

You compute a distributed parametric sweep on a cluster. When processing the results some values are missing or you get errors such as "The solution number is invalid" or "Solution number is out of range". This issue ...

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Solving Models with Step Changes to Loads in Time

Solution Number: 1245 Versions: All versions

How should I model loads that change magnitude at a particular time? I am solving a transient model which has loads that change instantaneously in time, but the solver appears to be missing some of these changes in ...

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Manually Setting the Scaling of Variables

Solution Number: 1240 Versions: All versions

The default behavior of the software is to assume a different scaling for each set of variables in your model. These scale factors are by default automatically determined, but sometimes may need to be manually tuned. ...

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Manually setup the geometric multigrid solver

Solution Number: 1213 Versions: All versions

The geometric multigrid solver accelerates the convergence of the iterative solver by solving the finite element problem on a series of meshes rather than a single one. The multigrid algorithm starts with the initial ...

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