Solver

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 ...


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 ...


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 ...


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 ...


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 ...


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 ...


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 ...


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 ...


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. ...


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 ...