Hi,
I am trying to study a single sheet tester and need a sample model of one. Any help is greatly appreciated.
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Sample Model of a Single-Sheet Tester
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PDE is coupled with ODE
How can i solve a system of equation in which a PDE is coupled with ODE (as attachment file)?? this is a mass transfer with reaction by considering boundary interface. I am a bigginer in comsol, so i would appreciate if anybody can help me.
Thanks in advance,
Best regards, Mojtaba
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Stokes Equation
I want to simulate my problem using Stokes equation and convection diffusion equation. I want the Stokes equation to not have any transient term. But the creeping flow module has time dependency, as I am doing a time-dependent study and the convection diffusion equation has a transient term, which is required to see the species evolution. Both the modules are coupled, so I cannot do a separate study, i.e., stationary for Stokes and transient for convection diffusion equation.
A way around this problem would be modeling the Stokes equation using PDE module. But I am unable to create a Stokes equation, grad(p) = mu * laplacian(u), using the PDE module.
Any kind of suggestion would be appreciated.
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error: Curl operator only supported for vector components in the differentiation system. - Expression: ∇×Eb - Variable: curlEb - Provider: Background Field
I am using EM-frequency,
I got this error:
Error in multiphysics compilation. Curl operator only supported for vector components in the differentiation system. - Expression: ∇×Eb - Variable: curlEb - Provider: Background Field What possibly could the reason be?
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1D line plot in 2D axisymmetric geometry
Hi!
I have a model with a 2D axisymmetric geometry and now, for the postprocessing, I need a 1D plot line that goes from -r to r, instead of just 0 to r.
I used the 2D revolution, then "Cut Line" to define the line where I want to evaluate my results, and when I plot it it's ok, as long as I use "Arc Length" for my x-axis. When I change the expression to "r", it only plots my results from 0 to r. I tried to define a range for my x-axis using "range(-x,step,x)", but COMSOL doesn't accept that range as an expression.
I'm attaching a couple of figures so it's easier to understand what I mean. In both figures I used exactly the same data set (cut line), only changed the expression for x.
Can anyone help me with this?
Thanks!
Clarissa
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Successfully modelling gravel.
Hi all comsol wizards!
I'm trying trying to model gravel as isolation in a floor between apartments. As for now i have modelled the gravel isolation as a block in comsol 5.3a and if i now assign the block any certain material, it will have a stiffness matrix and take up bending stress and in other words behave as a solid.
How do i prevent this and create a non-solid object? Is it correct to define a new linear elastic material in the solid mechanics field and reduce its stiffness parameters to zero?
Thank you in advance!
Best regards, Mark
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Peristaltic axial tube- Walls of tube not closing
Hi,
I am currently trying to build a peristaltic tube in Comsol. The model consists of an outter wall which is axial rotated to form a tube and water flows through the tube. Boundary loads are then applied to the tube to simulate acutuators acting on the tube. Picture shown below. These two loads then move up the tube and (hopefully) generate presure head and then top. I based my model on standard the peristaltic pump model that you can find on the comsol website and my model uses all the same physics.
The issue is that i want the walls of the tube to close to the centre when the boundary force is applied. I can get the wall to reach about halfway by increasing the load, however if the load is increased passed a certain point then the model spits out errors and doesnt solve. It says that it may have reached a singularity and that it has not converged.
Does anyone have any insight into how i could get the walls of the tube to close fully?
Much appreciated,
Rory
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Errors of singularities on meshing after integrating the derivative of the solution
Hi,
We are calculating the optical force within metal scatterers in a PEC bounded structure 2D model. The model is bounded by PEC with PMLs on the left and right sides. We define the background field Eb = E0exp(-jk*x) in the y direction and solve for the scattered fields (Please see the attached mph file).
The problem here is that the size of the mesh element can have significant impact on the integral of the force density. Please see the attached jpeg file. The x-axis indicates the maximum mesh element size in the model, which is the wavelength (633nm) over a number # (You may change the parameter, mesh_d, in the mph to have the same figure). The surface integral 1 calculates the gradient term (integral of the derivative of the solutions) and the surface integral 2 gives the Poynting term. The total is equal to the sum of the gradient and Poynting terms. We can see that the gradient term switches from negative value to positive value when varying the maximum meshing size.
https://www.comsol.com/blogs/how-identify-resolve-singularities-model-meshing/
This article explains that some issues may happen when singularities exist. In the conclusion, point 3 says that it is acceptable when calculating the integral of some quantity including the derivative of the solutions. However, we still have significant errors when applying different meshing. We also removed the sharp corners by filleting the scatterers, but the problem remains, especially for the gradient term.
Do you have any solutions toward this issue? Thanks.
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Error Message: Error in sweep
I am simulating tutorial "Heat Recovery System for a Geothermal Heat Pum" from Application gallery (Application ID: 18529) I am geting error massage below. Please help me to debuge this error.
message : The following feature has encountered a problem: - Feature: Compile Equations: Time Dependent (sol3/st1) Unknown reinitialization variable comp1.t_stop.
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periodic boundary condition implementation in Comsol
Hi I have a rectangular domain where the opposite edges have same values.I am working with Darcy law module where there in no periodic BC available.May I know how I may implement?
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Power that is sent through a scattering boundary condition
Hey everyone!
I am trying to obtain a transmission vs wavelength plot using Wave Optics Module and using the model shown in the attached image ("Structure"), which represents a unit cell of a photonic crystal. I send a wave using a scattering boundary condition at the top of the structure (whose parameters can be seen in the attached image "Scattering boundary conditions"). There is a block PML on the bottom of the structure and Floquet periodic boundary conditions all around.
I measure the Power outflow, time average (W) using ewfd.nPoav on the top surface of the PML (bellow the photonic crystal structure; surface integral) and the results I obtain (in terms of the shape of the transmitted power vs wavelength) are exactly the same as the ones shown in several research papers on photonic crystals (obtained by FDTD). The problem is that I need to normalize such transmission power values by the inputted power in order to obtain the actual transmission (a value ranging from 0 to 1) - but I can't figure out how to know the power I am inputting.
I can't use ewfd.nPoav on surfaces above the structure because that will give me the reflected power.
Does anybody know how I should proceed?
Thank you so much! :)
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Structural Analysis with Thin Elastic Layers Example Model File
Hi,
I am trying to understand the Thin Elastic Layer.
I have seen this article [1], however the model Composite Piezoelectric Transducer [2] mentioned in the article does not have a Thin Elastic Layer.
Is there an example model file?
- https://www.comsol.com/blogs/structural-analysis-with-thin-elastic-layers/
- https://www.comsol.com/model/composite-piezoelectric-transducer-503
Thank you Best regards, Osman
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2D Pipe Flow
I have simulated a stationary 2D pipe flow in a 30 mm X 5 mm rectangular domain using the Creeping flow module to solve the incompressible Navier-Stokes equation. The boundary conditions are no-slip wall on top and bottom edge, inlet velocity = 5 mm/s and outlet pressure is 0. I have obtained the results with max. velocity = 7.56 mm/s and max. pressure = 0.52 Pa.
The same simulation was run using weak form instead of using predefined modules. I have constructed the weak form for both continuity and momentum equation. I obtained the same velocity but the pressure distribution was not correct. Maybe there is mistake in my boundary conditions.
What is the mistake I am doing?
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How to prescribe 2D deformation
Hi all,
I would like to study aquatic propulsion using 2D simulation. However, I get stuck in the first step: how to prescribe the model deformation?
I can find the example "The Virtual Aquarium: Simulations of Fish Swimming". However, things are a little bit different in my case. I would like to define the model deformation directly, instead of defining stress to bend the model.
Is there any method that I can prescribe the locomotion of the mesh vertex, therefore, to control the deformation of the model?
Thanks in advance!
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beam - 3D solid connection
Hi, I have modelled rail as beam and sleepers as 3D solid and I need to connect rail to sleepers. there is no option available in comsol to connect beam with 3D solid. I need any other alternative.
Regards Varsha
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Use Magnetic and Electric fields (mef) physics to calculate the capacitance
Hello everyone, I am just a beginner of COMSOL and this problem has troubled me for weeks.
Is it possible to use Magnetic and Electric fields (mef) physics to calculate the capacitance of a model？
If so, which equation can be applyed？ Because COMSOL just doesn't provide a capacitance option in global evaluation by using mef physics.
Any reply will be appericated!
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Time dependent Boundary Conditions in electrical potential.
Hi, I am trying to model a electrical potential in a metalic cavity with 4 electrodes inserting into the cavity. Now I want to try to vary the potential of electrodes with time, i.e., changing Dirichlet bcs. I am new to COMSOL, I cant find proper option for my condition. Should I change physics from static electircal field to something else?
Best,
Yiqi
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Jump boundary condition
Sir/Mam
I would like to give a rectangular wave temperature boundary condtion to the inner surface of an annular geometry. The maximum wave temperature is 663.15K and the minimum is 623.15K. Each temperature exists for about 3600s. The whole simulation is for 10800s.
I tried interpolation (in function - > Definition), but the temperature shift is not exactly at 3200s, 7200s as it should be since periodic. It happens near to it.
My table goes like 0s 663.15K, 3600s 663.15K, 3601s 623.15K, 7200s 623.15K, ... so on
I do not know how to use rectangle, step function though they seems to be more appropriate.
Kindly guide me. I shall be thankful to you for this. Harshal
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acoustic metamaterial
Hi. can anyone tell me please how to retreive bulk modulus and density on cosmol/acoustic module for acoustic memtamaterials ? specially how to find transmission and reflection coefficents,is it from time domain or frequency domain ?
Regard.
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solar cell
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