Solver

Improving Convergence of Nonlinear Stationary Models

Solution Number: 103 Versions: All versions

Stationary (time-invariant) models with nonlinearities may converge very slowly. A nonlinearity can be introduced into the model either in the governing equation, or by making any of the material properties, loads, or ...


Improving convergence in nonlinear time dependent models

Solution Number: 1127 Versions: All versions

When I look at the Solver Log of a time dependent model, I see that the NLFail column has non-zero entries: Step TimeStepsize Res JacSolOrderTfailNLfailLinErrLinRes 0 0-out 23208e-14 3.5e-15 ...


Structural Contact Modeling Guidelines

Solution Number: 1102 Applies to: MEMS Module, Structural Mechanics Module Versions: All versions

This article contains guidance for solving models that include structural contact, and the procedures that should be followed to achieve a converged solution. Background Structural contact modeling is a highly non ...


COMSOL and Multithreading

Solution Number: 1096 Versions: All versions

This solution describes how COMSOL takes advantage of multicore computers. COMSOL supports two mutual modes of parallel operation: shared-memory parallelism and distributed-memory parallelism (cluster support). Shared ...


BDF, Generalized Alpha, and Runge-Kutta Methods

Solution Number: 1062 Versions: All versions

What numerical methods are available when using a Time-Dependent Solver? What are their relative benefits and when should I use them? The Time-Dependent Solver offers three different time stepping methods: The ...


Error: "Out of memory"

Solution Number: 1030 Versions: All versions

I get an error message, that contains the words Out of memory, for example: Out of memory during LU factorization. or Out of memory during assembly # Background Before resolving this issue, you should go through ...


Running COMSOL® in parallel on clusters

Solution Number: 1001 Versions: All versions

This solution describes how you enable distributed parallelization (cluster jobs) in COMSOL Multiphysics®. COMSOL supports two mutual modes of parallel operation: shared-memory parallel operations and distributed ...


My flux calculation seems wrong

Solution Number: 973 Versions: All versions

I am solving a diffusion-like problem in COMSOL Multiphysics and discovered that boundaries that are defined with insulation/symmetry conditions have an integrated value of the normal component of the flux that is far ...


Error: Failed to find a solution. Returned solution is not converged

Solution Number: 964 Versions: All versions

I get this message: Failed to find a solution. The relative residual (0.28) is greater than the relative tolerance. Returned solution is not converged. Messages similar to this are returned for nonlinear problems ...


Avoiding negative concentrations

Solution Number: 952 Applies to: COMSOL Multiphysics, CFD Module, Chemical Reaction Engineering Module, Electrodeposition Module, Microfluidics Module, Subsurface Flow Module, Mixer Module, Corrosion Module, Electrochemistry Module Versions: All versions

Why do I get negative values of the concentration in my diffusion, convection and reaction model? Why do I see values that go below, or above, their lowest, or highest, possible values based upon the boundary ...