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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).

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Fermi level determination

Is there a semiconductor physics module in COMSOL which correctly describes the Fermi level position for any bandgap system ( especially under different doping concentration)?? If not what is solving ...
Mohsen's user avatar
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1 vote
0 answers
36 views

What is the physical quantities in the equations for linear elasitc materials in a frequency study in comsol

I am using comsol to model a linear elastic materials and perform a frequency domain study. I try to understand the equations it provided but all symbols are not explained. For example, How should or ...
lsdragon's user avatar
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3 votes
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93 views

Is there any book about fundamental FEM theory using similar terminology as Comsol MultiPhysics?

I am considering to solve complexed PDE systems, like in this post, using Comsol MultiPhysics. The PDEs are different from the General Form provided by Comsol. The Weak Form module may be worth a ...
Charles6's user avatar
2 votes
0 answers
108 views

Conceptual doubt regarding 2D conjugate heat transfer modelling (COMSOL and Mathemtica)

I have been dealing with some conceptual flaws in my understanding of modelling, which I will elaborate herein. I am modelling conjugate heat transfer of a reciprocating fluid, which flows with ...
Avrana's user avatar
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1 vote
2 answers
349 views

What is the difference between non-linear elastic simulation and linear elastic simulation with plasticity?

I'm learning how to do Finite Element calculations using Comsol Multiphysics. In Comsol, Linear Elastic Material and Nonlinear Elastic Material are available as material models: Using Linear Elastic ...
S. Rotos's user avatar
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2 votes
0 answers
139 views

switching boundary conditions to simulate a reciprocating flow in COMSOL

This is a re-posted question which was poorly defined earlier I have been trying to simulate reciprocating flow of a convective fluid through a heated channel in COMSOL-Multiphysics. The schematic of ...
Avrana's user avatar
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1 vote
0 answers
110 views

Weird "oscillatory" modes appearing in FEM simulations

I am using COMSOL to solve a mathematical model involving thermoelectric hydrodynamic (TEMHD) flow. I am running a very large parameter sweep and using the solutions obtained to make some plots. ...
epsilonD3LT4's user avatar
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52 views

Why does COMSOL treat a well as a rectangular cube?

I'm trying to learn COMSOL for a graduate research project and am struggling through a flow and transport in 3D tutorial. As such I'm walking through my boundary conditions and trying to figure out if ...
ldorchester12's user avatar
0 votes
1 answer
146 views

How to connect two cylinders to form a knee in Comsol Multiphysics?

I have this I want it to be single bended wire. How to accomplish?
Dims's user avatar
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1 vote
2 answers
380 views

Writing a single PDE from a gradient equation

I have a differential system like this, where $\Phi$ is a scalar valued unknown function: $$\nabla\Phi = \left(f_1(x, y), f_2(x,y)\right)^T$$ I'm trying to solve it in a FEM solver (COMSOL ...
VP06's user avatar
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0 answers
303 views

COMSOL Circularl polarization

I'm having some problems trying to implement circularly polarized light in COMSOL Muliphysics. For a isotropic homogenous media, I've obtained without problems the TE and TM reflectance curves. ...
Antonio Ganfornina Andrades's user avatar
2 votes
1 answer
267 views

Does mass balance hold in convective diffusion

I'm trying to understand how convection-diffusion equations are solved in pipe flow modules available in CFD solvers. $$ \frac{\partial C}{\partial t} + \nabla \cdot (\mathbf{v} C) = \nabla \cdot (D \...
Natasha's user avatar
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1 answer
209 views

A lot of identical staff in Comsol material database?

I got a lot of elements in Material Browser of Comsol Multiphysics of Optics section. ...
Dims's user avatar
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1 vote
0 answers
44 views

Fitting a multivariate PDE (using Java)

I'm doing simulations of 2 coupled PDE's with Comsol Multiphysics. I want to fit some data (using the Application method, whose language is Java) to those simulations. In order to answer my question ...
J.A's user avatar
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0 answers
105 views

Simulating flow in a branched pipe

I am trying to simulate 1D advection and convection of a solute in the following blood vessel segment. I would like to know if this system can be simulated in COMSOL or MATLAB. I have used pdepe ...
Natasha's user avatar
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1 vote
1 answer
535 views

For a determined (known) Space charge density, what are the conditions to obtain the Electric potential/field distribution? (COMSOL, MATLAB)

Theoretic part From the theory, in Electrostatics inside a real dielectric material between real conductors, in a simple 1D plane geometry between points $P1$ and $P2$, according to the current ...
Lucian Viorel's user avatar
2 votes
1 answer
403 views

Derivatives over a Finite Element mesh

I have a data extracted from Comsol on some node points and I know the coordinates of each node. Does anyone know how Comsol calculate the partial derivative from the values at each node and also ...
starhd's user avatar
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1 answer
667 views

How to set an initial guess for the iterative solver in Comsol?

How to set the initial guess for the iterative solver GMRES or FGMRES for linear problems (Helmholtz equation of RF module) in Comsol?
praveen kr's user avatar
3 votes
0 answers
128 views

Strain propagation from surface to bulk in COMSOL

I am trying to simulate strain propagation from the surface into the bulk. I have a rectangular semiconductor block (~2 μm thick) on top of which metal gates (~25 nm thick) are deposited as seen in ...
duncanidaho's user avatar
1 vote
0 answers
530 views

Changing geometry scale breaks simulation

I'm trying to find the capacitance matrix for a small array of metal boxes in air using Comsol 5.4. The geometry presented here is a simple geometry that recreates the problem I'm experiencing. ...
Matt's user avatar
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1 vote
0 answers
414 views

How to simulate water, falling under gravity, and impinging on a curved surface, which is kept/present in a domain, containing air?

TL;DR: How do I simulate a hole, at the bottom of a (full) water tank? I am attempting to simulate water, flowing out of a hole/slit, at the bottom of a tank (Water Domain) (under the influence of ...
P_0's user avatar
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1 answer
227 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 ...
Alireza's user avatar
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1 vote
1 answer
150 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 ...
Meesoto's user avatar
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1 vote
0 answers
1k 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 ...
Foad's user avatar
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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 ...
Ali Abbasinasab's user avatar
7 votes
2 answers
752 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 ...
Jakub Klinkovský's user avatar
1 vote
0 answers
97 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 ...
Ather Cheema's user avatar
1 vote
1 answer
1k views

Flux boundary condition in solute transport

I have a pretty naive question, though important 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 asked to ...
Daniel's user avatar
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2 votes
1 answer
236 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} = \...
AAI's user avatar
  • 123
1 vote
2 answers
1k 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 ...
Blue_Elephant's user avatar
3 votes
3 answers
3k 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 ...
Mike D.'s user avatar
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1 answer
1k 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 ...
Ru887321's user avatar
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0 votes
1 answer
56 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 ...
Abiodun O. Jegede's user avatar
1 vote
0 answers
103 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 ...
Tom's user avatar
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1 vote
1 answer
2k 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}\...
RAMANISH SINGH's user avatar
10 votes
4 answers
373 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 ...
Dandelion's user avatar
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0 votes
2 answers
371 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 ...
tkoencov's user avatar
14 votes
3 answers
19k 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....
V.Vocor's user avatar
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1 vote
0 answers
392 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 ...
Slav's user avatar
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7 votes
1 answer
6k 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; ...
Evgeni Sergeev's user avatar
0 votes
1 answer
3k 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, ...
Stepan Loginov's user avatar
1 vote
0 answers
1k 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-...
lisaPor's user avatar
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3 votes
2 answers
702 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 ...
seb's user avatar
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1 vote
1 answer
2k 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 $\nabla$ ...
Ali Abbasinasab's user avatar
1 vote
1 answer
968 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?
sima's user avatar
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2 votes
0 answers
770 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, ...
Stepan Loginov's user avatar
2 votes
1 answer
707 views

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

I'm reading up on the Finite Element Method (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 ...
seb's user avatar
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1 vote
1 answer
2k 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)$...
Ali Abbasinasab's user avatar
4 votes
1 answer
4k 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 ...
Ali Abbasinasab's user avatar
2 votes
1 answer
4k 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 ...
Ghartal's user avatar
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