Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [comsol]

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

0
votes
0answers
16 views

COMSOL Multiphysics. Set fixed constraint for a face in only one direction

I'm making a solid mechanics study for a steel plate (like a box). I'm applying a normal force on one face, and I'd like to fix the opposite face during the deformation. However, I need it to be fixed ...
0
votes
0answers
37 views

Mode analysis of a rectangular dielectric waveguide

I am currently doing a 'Mode analysis' study of an anisotropic dielectric rectangular waveguide (the cladding is air, the core is GaSe and boundary condition: PEC). I have two dispersion curves for ...
0
votes
1answer
49 views

Simulation of a complicated projectile motion

I'm trying to model a projectile motion, considering every detail such as projectile aerodynamics, effects of wind, air temperature etc. What is a good software to model it in with good graphics? I ...
0
votes
1answer
80 views

temperature profile on axial direction of a chamber

I have a task to plot average temperature profile at each cross-section in the axial direction of a combustion chamber. I have $x$, $y$, $z$ coordinates data in excel as well as the corresponding ...
1
vote
0answers
254 views

3D visualization of the results of a 2D simulation in COMSOL

Considering that COMSOL forum is dead and CFD-online is not responsive, I'm gonna try asking my question here: I have done a 2D simulation in COMSOL multiphysics. I have two independent variables x ...
1
vote
0answers
45 views

Computing dilogarithm

I'm measuring the integral of a quantity which, mathematically, requires the computation of a dilogarithm function. $$\operatorname{Li}_2(be^{ax})$$ where $b$ and $a$ (are real and) can be positive ...
8
votes
2answers
292 views

Mesh ordering algorithms used by COMSOL Multiphysics

Ordering of elements in an unstructured mesh is undoubtedly very important for the performance of computations. For example, it determines the structure of sparse matrices arising from PDE ...
1
vote
0answers
62 views

Modelling fracture flow in stress field in COMSOL [closed]

I am new to COMSOL and I want to model fluid flow in stress field. As starting point I want a simple 2D box having a fracture from right to left while pressure gradient vertically. I want to know the ...
1
vote
1answer
307 views

Flux boundary condition in solute transport

I have a pretty naive question, though imporant to me. Usually when solving the following PDE in solute transport: $\frac{{\partial C}}{\partial t } = \nabla. (D\nabla C -vC )=0$ one can be ask to ...
2
votes
1answer
101 views

Why FEM electric analysis gives only access to current density?

A Comsol study using frequency sweep on electric current physics yields only current density as accessible variables. I understand the underlying equation used is Ohm's law, i.e. $$\mathbf{J} = \...
1
vote
1answer
58 views

Perfectly matched layer simulation with two vibrating sources

I'm doing PML simulation, and while I was looking for correct geometry for my layers of propagation, I got question. My device, has two vibration sources, and this vibration will propagate through ...
0
votes
2answers
300 views

How does rigid body rotation affect resuts in a simulation?

I have been running a finite-element simulation where, for the sake of convergence, I chose to stay in small deformation hypothesis (in comsol, include non-linear geometry box not checked for who that ...
4
votes
3answers
1k views

Understanding Finite-Element Modal Analysis

I am teaching a basic course on computational physics and for the last part of the course I will introduce freshman physics undergraduates to finite-element modelling methods. I am preparing a COMSOL ...
1
vote
0answers
179 views

Implicit equation solving COMSOL [closed]

I want to solve a implicit equation in a domain in 1-D geometry. The equation looks like this: i=exp(phi1-phi2-U-i*R) phi1,phi2 are time and space dependent variables. R is a constant. I tried ...
0
votes
1answer
661 views

COMSOL: get list of eigenfrequencies [closed]

In COMSOL, is there a way to get it to export a txt file with all the eigenfrequencies found during an eigenfrequency analysis? I suppose that it could be done through the MATLAB interface or through ...
0
votes
1answer
45 views

Different Meshes Different Maximum velocities

I am working on a model in COMSOL and I am usin different meshes from coarse to fine keeping the other parameters constant. And, I got different maximum velocities for all the meshes. What can I do ...
1
vote
0answers
77 views

Representing a 3D system in 2D (Electromagnetic modelling)

Ok so I'm a complete beginner in computational modelling (I use analytical methods of physics typically) but I would like to model an anisotropic, aperiodic (but not random) finite array of metallic ...
0
votes
1answer
1k views

Solving coupled PDE in COMSOL [closed]

I have the system of equations \begin{align} &A \frac{\partial u_1}{\partial t} = 1 - u_1 B \frac{\partial u_2}{\partial y}\\ &\frac{\partial u_2}{\partial t} = \frac{\partial}{\partial y}\...
11
votes
4answers
268 views

How to make a good mesh in a biologically accurate model with very small domains

I have been trying to make a biologically accurate 2D spatial model of tissue layers, where different physiological processes happen. This includes mainly chemical reactions, diffusion and fluxes over ...
0
votes
2answers
183 views

3D Divergence-free Stokes equations

I would like to have a divergence-free formulation of the Navier-Stokes equations for creeping flow (a.k.a. Stokes equation, N.-S. without the inertial terms) in 3D, for purposes of tracking particle ...
10
votes
3answers
10k views

Alternatives to Comsol Multiphysics

This might be a question better suited for the Software Recommendations side of S.E., however I do believe that people who frequent this part of S.E. are more likely to be able to answer this question....
1
vote
0answers
337 views

infinite but non-periodic space with PMLs in Comsol [closed]

I have a problem with implementing proper boundary conditions on sides of my simulation (in RF or WaveOptics module of Comsol). I want to obtain an infinite but not periodic space (beacuse then I will ...
3
votes
0answers
2k views

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; ...
0
votes
1answer
2k 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, ...
1
vote
0answers
911 views

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 Results-...
3
votes
2answers
463 views

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 ...
1
vote
1answer
935 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 $\nabla$ ...
1
vote
1answer
727 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?
2
votes
0answers
580 views

How to solve global equation in Comsol only once? [closed]

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, ...
1
vote
1answer
556 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 ...
1
vote
1answer
1k 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 = d(L_x,x)+d(L_y,y)+d(L_z,z)$...
4
votes
1answer
3k 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 ...
2
votes
1answer
3k views

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 ...
3
votes
2answers
8k views

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 ...
1
vote
0answers
3k 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 ...
1
vote
0answers
60 views

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 ...
1
vote
1answer
638 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 ...
3
votes
1answer
4k views

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 ...
2
votes
0answers
3k views

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 ...
4
votes
2answers
709 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, ...