Undefined value found in the equation residual vector.
I am trying to model a pem fuel cell. Although I have entered all parameters and values, i have some errors as follows; Undefined value found. - Detail: Undefined value found in the equation residual...
View Articletime dependent study
I am trying to model a countercurrent shell and tube heat exchanger like geometry that involves heat tranfer coupling and also reactions. I am getting the results for steady state simulation but when i...
View ArticleFinding impedance between two terminals?
Hi there, I have a simple coaxial structure with four electrodes placed in a line. I apply a voltage to the outer two terminals by: T1: 0.5*sin(2*pi*es.freq) *(outer left)* T2: -0.5*sin(2*pi*es.freq)...
View ArticleHeat Transfer Module - radiation calculations separation
Hi, I created a model in which I want to calculate steady-state temperatures of assembly of solids with given boundary temperature, heat dissipation and so on. And I managed to do that using Heat...
View ArticleInductance modelisation: matrix has zero on diagonal
Hi, I am trying to determine the resonance frequency of a racetrack inductor. I followed the 3d inductor tutorial from the AC/DC library. The stationary study works fine, obtained an inductance of...
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Advanced photonic bandgap (triangular lattice)
Hello, I'm trying to expand the photonic bandgap model (www.comsol.com/model/bandgap-a...ysis-of-a-photonic-crystal-798) to a slightly different structure, but since I'm new to photonic crystals, I'm...
View ArticleForced timestep size for transient simulation
Hi! I would like to know, whether it is possible at all to force COMSOL to use large timesteps? I do not care about accuracy right now, I want to test a setup and have direct control over the temporal...
View ArticleCoupling back and forth between physics nodes
Hey I'm creating a model where I want to couple back and forth between light diffusion (stationary Helmholtz equation) and bioheat transfer (time dependent). This to implement dynamic temperature...
View ArticleCorrosion modelling in reinforced concrete
I have been trying to model chloride induced corrosion in reinforced concrete. I am not clear with the physics part. How can we build our own set of equations?? Can someone please discuss the physics...
View ArticleHelp!! How to use the solution of ODE for the geometry in other component?
Hi, I am new to COMSOL. I tried to learn from many COMSOL example models available. Recently I run across this example "Interpolation between points using a COMSOL App" with this explanation...
View ArticleElectrode modeling - diffusion
Hi everybody, I am new to COMSOL and I need to model a 2D problem. I have two electrodes (a generator and a collector) immersed in a support electrolyte of 100mM of KCl in which there's a 1mM of...
View ArticleSkip unsolvable parameters in parametric sweep?
General question. I run a parametric sweep and occasionally one of the parameters causes a simulation that doesn't converge. e.g. the parameters are param = 1, 2, 3, 4, 5 meters and this simulation...
View ArticleSetting pressure
I want to study flow in pipe I want to set v = 0.05 m/s AND p = 5 atmat the inlet How to set them both? I mean, under laminar flow -> inlet -> boundary conditions I can choose one or the other,...
View Article"Include Geometric Nonlinearity" for Membrane
Greetings, I read through the manual for Membrane node and found that "Include Geometric Nonlinearity" is necessary to be checked in the Study Step. This is to include the prestress specified in...
View Articlemodifyin mesh didn't modify my results
Hi, I have modified my mesh in order to choose the appropriate one for my next simulations, however i have got the same result for extremely fine as for normal mesh. I'm looking for different values of...
View ArticleConvergence problem withtime dependent fluid flow with heat transfer
Hi, I am studying a three dimensional model in which the hot air flows through a pipe and the pipe is surrounded by a phase change material. As a result there are three domains: air domain (turbulent...
View ArticleHow to prevent fluid mesh from degradation in fluid - structure - interaction...
Hello community! I use (fsi) module for modelling of vocal fold vibrations in 2D. At certain conditions the solid (vocal fold) deforms the fluid mesh too much resulting in mesh collapsing /...
View ArticleModelling a Non linear Magnetic Material
Hi there, So I am currently trying to model a non linear magnetic material. The object is a plate of unknown material. The only information I have for the plate is a BH curve. The magnetic field is...
View ArticleSolving 3 PDEs simultaneously. Require help in defining the PDEs
I need to solve 3 PDEs simultaneously. I am facing problems designing those PDEs. Kindly help. I am attaching an excerpt of a paper which has all the info. I am trying to solve eqns 4,5,6 of the paper....
View ArticleVariable thickness
Hello helpers, Currently i working on a simulations of a wall section. In this case its simplified and only existing of a brick outside wall, insulation layer and gypsum on the inside. In order to full...
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