Formerly FEMLAB, COMSOL is a finite element analysis software package for various engineering and physics applications, with special emphasis on coupled phenomena (multiphysics).

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What is numerical damping in the context of time-dependent FEM solvers?

Comsol Multiphysics (a popular FEM package) includes two time-stepping algorithms (IDA aka BDF, and Generalized-alpha), described in their documentation as follows (quoted here under Fair Use; ...
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COMSOL: String vibration modeling using Wave Equation PDE

I am learning comsol and already could make the vibration of a string in 1D (geometry used there was an interval) - I saw 2D plot and the string was vibrating, also I could do the same in 2D ...
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60 views

boundary condition in COMSOL

I deal with PDE module in COMSOL and I would like to simulate Poisson's equation. Actually I need to simulate the distribution of the electric filed created by the spherical probe in the material, ...
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COMSOL time dependent study

So I am trying to do an eddy current simulation to get the magnetic fields that result from eddy currents. Essentially I have two coils that are pulsed with current and there are copper bars around ...
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Importing port mode solution in Comsol

I'm using the wave optics module to simulate a strip waveguide. I thought I'd start by finding the modes in a 2D simulation before going to 3D. My question now is how can I import the mode solutions ...
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plot issue in Comsol Multiphysics

I'm dealing with an Axisymmetric 2D model in Comsol Multiphysics. In other words I working in cylindrical coordinate system. Now I need to build a graphic which represents a changing of some variable ...
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COMSOL - 2D box - get for every x an average value over y (line average apply for more lines) [closed]

I would like to ask you for your help. I have 2D box. I know how to do an 2D cut line and compute an average value of someting over this line. (in Results -> Data Sets -> Cut Line 2D and then ...
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118 views

Anyone knows why surface-to-ambient radiation is not applicable to interior boundaries in comsol?

I have a 2D model consisting of a square piece of electrical insulator and in the middle I have a thin rectangle acting as a wire. I'm running a current through it so I heat it up to 500 K. Clearly it ...
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Integrating an Ordinary Differential Equation over a domain in Finite Element Methods

I'm trying to get a deeper understanding of the Finite Element Method (FEM) to better understand what I do in COMSOL and FEniCS. The sketch below shows the problem that I want to solve in FEM. The ...
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285 views

COMSOL RF or Opitcs Circular Polarization

Anyone know how to model circularly polarized light in COMSOL 4.3? And also validate it! I thought this would be easy, the following being my solution. I'm using a frequency domain solution. I'm ...
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137 views

Calculating Divergence in COMSOL

Is it computationally safe and accurate to use the following equation in COMSOL to compute the divergence of the vector quantity J (instead of using its general built-in equations that have $\nabla$ ...
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166 views

How can I define Poisson’s equation in general and weak form in comsol

I want to simulate capacitor with Comsol by using Poisson's equation in genaral and weak form. How can I specify boundary condition for this case?
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How to solve global equation in Comsol only once?

Let's assume that I have a comsol model for solving time-dependent problem. In order to find initial value for one variable I need to solve simple algebraic equation before starting simulation, ...
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251 views

Basic Finite Element Method (FEM) question: assembly and re-assembly

I'm reading up on the Finite Element Method (in Zienkiewicz's Book) , so I understand better what I'm doing in FEniCS and COMSOL. Currently, I'm wondering about this: Using FEM to solve fluid flow ...
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398 views

Divergence in COMSOL

I'm trying to calculate the divergence of a vector quantity $L(L_x, L_y, L_z)$ in COMSOL. I calculate it using the built-in differentiation operator as follow: $$\nabla L = ...
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717 views

Stress due to the mismatch of thermal expansion coefficients of two different attached materials in COMSOL

I'm simulating the thermo-electro-mechanical behavior of a copper wire which is surrounded by silicon dioxide. In other words, the wire segments is under mechanical and thermal loads and at the same ...
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PDEs in their weak form in Comsol

If a physical model is not listed in the wizard, we can use Comsol's weak form to enter PDE's (governing equations of a system) in their weak form. How can it be done ? for example: 2 equations of ...
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Coupling Equations in COMSOL

I want to solve the following equations: $\frac{{\partial n_D(T)}}{\partial t } = \nabla. (D\nabla n_D(T) -vn_D(T) )=0$ where $D$ is the diffusion constant, $v$ is the velocity and $n_D(T$ is the ...
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Time stepping in comsol multiphysics

I would like to know which is the algorithm Comsol uses in order to correct the time step it uses. For example, when you try to solve an equation you've written in the PDE coefficient interface, and ...
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918 views

Stationary solution converge but time dependent doesn't

I've coupled a COMSOL model for fluid dynamics with a very simple pde that model the transport of humidity in air. When I solve it for the stationary case, the solution converge easily, but when I ...
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Can I use RANS to see the effect of mixed convection?

my question is: can I use a RANS simulation to see the effect of mixed/natural convection? Actually I have also a second question: I would like to do this in Comsol multiphysics, but it seems that it ...
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242 views

How to include parameters in plot title in comsol? [closed]

I have a comsol model. I want to draw a few plots for different values of a global parameter called plot_z, e.g. if plot_z can ...
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In Comsol Multiphysics, is there a way to change parameter values when something happens in the solution?

I'm beginning to learn Comsol Multiphysics as part of a modelling course in my masters degree. Currently, we are modelling a circuit with a spark gap, which presents some problems for me. I'm using ...
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COMSOL - Implementing Perfectly Matched Layers (3D)

If there are any COMSOL gurus here, I want to simulate a 3D RF system infinite in 1 direction. I realize I need to use PML's, but am unsure how to configure them. it seems that simply scaling them by ...
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559 views

COMSOL on Ubuntu (10.04 LTS and 11.04)

I am running into a problem with COMSOL 4.2.0.187 on Ubuntu (both 10.04 LTS and 11.04). When using the option -np x with x > 1, ...