Física

Solving time dependent models with inconsistent initial values

Número da Solução: 1172 Versões: Todas as versões

A common mistake when setting up transient models is to have initial conditions that are inconsistent with the loads and boundary conditions. This occurs most often when running transient fluid flow studies, but the ...


Using symmetries in COMSOL Multiphysics

Número da Solução: 1038 Versões: Todas as versões

How do I take advantage of the symmetries in my COMSOL model? ##Using Symmetries to Reduce Model Size By using symmetries in a model you can reduce its size by one-half or more, making this an efficient tool for ...


Stabilization schemes in COMSOL

Número da Solução: 1104 Aplica-se a: CFD Module, Chemical Reaction Engineering Module Versões: Todas as versões

How can I see which stabilization schemes are used by COMSOL Multiphysics in transport physics interfaces such as Single-Phase Flow and Transport of Diluted species? Numerical solutions of transport equations can ...


My flux calculation seems wrong

Número da Solução: 973 Versões: Todas as versões

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 ...


Avoiding negative concentrations

Número da Solução: 952 Aplica-se a: COMSOL Multiphysics, CFD Module, Chemical Reaction Engineering Module, Electrodeposition Module, Microfluidics Module, Subsurface Flow Module, Mixer Module, Corrosion Module, Electrochemistry Module Versões: Todas as versões

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 ...


Computing Time and Space Integrals

Número da Solução: 913 Versões: Todas as versões

How do I compute integrals over space or time? What if I want to use the result of these integrals elsewhere in my model? The COMSOL Multiphysics architecture allows you to evaluate integrals in both space and time in ...


How does COMSOL Multiphysics handle complex-valued numbers and problems in the frequency domain?

Número da Solução: 878 Aplica-se a: AC/DC Module, Acoustics Module, COMSOL Multiphysics, MEMS Module, Plasma Module, RF Module, Semiconductor Module, Structural Mechanics Module, Wave Optics Module Versões: Todas as versões

How does COMSOL Multiphysics handle complex-valued numbers and problems in the frequency domain? Should I use the RMS, the peak, or the instantaneous value to specify sources in models being solved in the frequency ...


What does degrees of freedom (DOFs) mean in COMSOL Multiphysics?

Número da Solução: 875 Versões: Todas as versões

What does degrees of freedom (DOFs) mean in COMSOL Multiphysics? The solution time and memory requirements are strongly related to the number of degrees of freedom in the model. It is often desirable to be able to ...


How do I solve a PDE with space derivatives of order higher than two?

Número da Solução: 816 Versões: Todas as versões

How do I solve a PDE with space derivatives of order higher than two? For example, the equation for a function . Introduce names for the second derivatives of u, say . Then the equation can be written . ...


Modeling of step transitions

Número da Solução: 905 Versões: Todas as versões

You may want to define loads, material properties, or boundary conditions that vary abruptly with respect to the solution, or with respect to time. This can, however, lead to a solution which is discontinuous in space ...