When I use comsol, the restarted computation is appeared even I do not use consistent initialization. I would like to know when the restarted computation will be applied?
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Restarted computation?
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Nusselt number for heat generating element
hello, recently i have been working on a paper where i faced the problem of defining Nusselt number for heat generating element in a square cavity.can anyone help ?
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Reinforced Concrete Beam (Eigen Frequency)
Hello, I am new to comsol and i am working on reinforced concrete beam to analyse the displacement of the beam for 100Hz and 200 HZz frequency. The concrete beam is of 10*12 with steel reinforced. The beam is clamped on right and left side and the bounday load is given at the bottom(2000N/m2). The eigen frequency analysis shows diplacement in meters actually my displacement should be in microns. changing the boundary load seems no change in the displacement. Can anyone help me out with this.
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Corona Discharge- Cold Plasma
Dear users and specialistics, my case study focuses on the optimization of corona discharge and therefore the presence of cold plasma with its specific chemistry. We are doing a first approximation in 1D. The present error that appears to me constantly is the following:
Deprecated behavior: Evaluation of the partial expression failed, which forced the full expression to be zero. Partial expression: comp1.plas.ne Full expression: down(comp1.plas.ne) Boundary: 1 Deprecated behavior: Evaluation of the partial expression failed, which forced the full expression to be zero. Partial expression: comp1.plas.ne Full expression: up(comp1.plas.ne) Boundary: 2
I try to add the variable ne (plas.ne=Ne) but still gives me the same error. Can anyone help with this comsol error? Thanks in advance.
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Refracturing in Shale
Has anyone did refracturing simulations in any rock or reservoir?
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The simulation of pm-motor in RMM physics--Identity boundary pair and magnetic insulation boundary
Dear all, I am simulating a pm-motor in rotating machinery magnetic(rmm) in comsol. In the process of my simulation, I have met the questions in the title. I have done with in 2 ways. Case one, I imported my entire model with the dxf file. In this way,I cannot created the identity boundary pairs but the magnetic insulation boundaries are correct. Case two, I draw the stator part and rotor part in a file. And I imported the file in comsol. The rest parts of my motor I drew in comsol. I successfully created the identity boundary pairs but the magnetic insulation boundaries are not corrected. The magnets were with the magnetic insulation,I tried defined another magnetic insulation boundaries to override the boundaries that automatically selected in comsol. When I computed,the the magntic flux density of magnets were nearly zero. Anyway, if you met the similar quetions, hope you can write down your opinions or share your ideas generously. I show my sincere thankfulness to you. I uploaded a picture that the physics, it cannot change the boundaries it automatically made. The units in the picture cannot make changes.
Regards Joey
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Multiphysics Organic Photovoltaic IV characteristic Simulation
Dear all,
I am currently working on a project relating to Organic Photovoltaic cell (using polymer). I would like to simulate the IV characteristic of the cell. However, I am unsure which physics model should I use. I am currently using Semiconductor Model. But I think it might not be right.
Please Help!
thanks
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Halbach Array Mandhala Polar Define magnetization directions
have a nice day. my name is Erhan. I want to model the 8-magnet double-sided halbach mandhala array. In physics, I chose 'magnetic field no curret'. I'd like to identify a neodymium magnet. I'm entering Br values. As it is known in the Halbach series, there must be 2 magnets opposite each other. One is N pole and the other is S pole. I don't know how to determine the polarity and magnetization directions. My joy if you help.
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Get the entity number of an edge using matlab
Hello
Do you have ever get the entity number of an edge using the start and end points of that edge? In fact, I have the coordinates (and definitely their entity numbers) of two specific points (for instance the point 1 and 2) then, I'm gonna find the entity number of that edge which is made by those points (it might be a curve or even more complicated edge)
I don't wanna use the "mphselectbox" or "mphselectcoords" because of this problem; according to the image that I've attached Imagine in 2D, you have two lines and 3 points and you create a box using "mphselectbox" and the coordinates of the "point1" and "point2" *to get the entity number of "line1". (actually,the entity number of “line1” is our goal) as you see in this image, the result of "mphselectbox" function is the entity number of "line1" and also "line2" !!!!!!!!!!!! because "poitn3" is in this box (which is the smallest box contains "point1" and "point2")
I have a complicated geometry with many points and edges in 3D and I'm gonna get the entity number of every edge using the start and end points of each edge.
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microphone directivity pattern
How to simulate omnidirectional and cardioid microphone and get them directivity patterns? And how to compare them?
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Backflow into inlets with multiple inlets
Hi everyone,
I am simulating laminar flow through a thin geometry with two inputs on one side and one outlet on the other side (see image for the geometry). When initializing the inputs via velocities I get the expected results - see the corresponding image (the upper inlet has 10x the velocity of the one below). But with pressure as inputs, the simulation results in a (back)flow between the two inputs.
Obviously I enabled "suppress backflow" for both inlets but this only seems to account for the "own" input and not the other one. I tried to add weak constraints but these can only be applied to a volume. Is there an option to define equations on a surface?
An option I found is to take fans as input and output but these require pressure curves and the system will not be fan-driven.
I also added the MPH file.
best regards Claus
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Identity Boundary Pairs And Magnetic Insulation Boundary
Dear all,
I am simulating a pm-motor in rotating machinery magnetic(rmm) in comsol. In the process of my simulation, I have met the questions in the title. I have done with in 2 ways. Case one, I imported my entire model with the dxf file. In this way,I cannot created the identity boundary pairs but the magnetic insulation boundaries are correct. Case two, I draw the stator part and rotor part in a file. And I imported the file in comsol. The rest parts of my motor I drew in comsol. I successfully created the identity boundary pairs but the magnetic insulation boundaries are not corrected. The magnets were with the magnetic insulation,I tried defined another magnetic insulation boundaries to override the boundaries that automatically selected in comsol. When I computed,the the magntic flux density of magnets were nearly zero. Anyway, if you met the similar quetions, hope you can write down your opinions or share your ideas generously. I show my sincere thankfulness to you. I uploaded a picture that the physics, it cannot change the boundaries it automatically made. The units in the picture cannot make changes.
Regards Joey
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How to use previous solution as a initial condition in time dependent PDE with parametric sweep
I want to run parametric sweep on a time dependent PDE problem. During each parameter I want to set previous solution as a initial condition. I did it as attached. But in that case I have to manually change the parameter and run the simulation again and again for different parameter. I want to automate the process and do it in a parametric sweep.How can I do that?
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Removing thermal insulation
I am new to Comsol I am trying to simulate a time dependent spark plasma sintering process using the Joules heating and thermal expansion in structural mechanics multi-physics module. I have a problem in removing the thermal insulation , free constraints in the model. Due to this I am not able to get correct results. In reality maximum temperature will occur between die-specimen, punch-specimen interface, but here I am getting maximum tempertaure between small spacer-punch interface. Can anyone help out in solving this I have attached the model and simulation file.
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Modelling a basic coil in COMSOL Multiphysics using the AC/DC module
Madam/Sir, I'm new to this software. I've went through the introduction videos posted in the website itself. I went through one of the blog written by Walter Frei which said about designing a single current carrying coil, in COMSOL. I want to start with the similar(and simple) example (attached with this post) to get to know the platform. Is there any step by step instructions as how to achieve the whole modelling and simulation processes?
P.S.- One of the figure is is attached with the discussion post. Please check the same.
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Different results are strange with same definitions but different physics
Dear all,
I am simulating a pm_motor that I defined the magnets with Ampere Law. I used the same value of remenant flux density. When I reached the result, the result in magnetic field is normal but in rmm field is zero. The magnetic insulation is in same condition. I uploaded the pictures of the results. Have you met this problem? How can I solve the problem. Thanks.
Regards Joey
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Simulation analysis of liquid placed in a container
For example, place water in a metal tray, how can i to simulate? What the model of fluid I need? I'm a beginner, please help me. Thank you very much.
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Unexpected behaviour of "intop" function
Hi all!
First of all I'd like to thank this forum, here I have found many answers I needed before. But now I couldn't find any at all.
Thing is, I have a quite complicated 2D model of a superconducting magnet. My model is a transversal section of the magnet where we can see all the conductors as "domains" and the electric current is perpendicular to the plane.
The electrical resistivity of the conductor is a function of the temperature and magnetic field. So I imported a table and COMSOL interpolates it to obtain the resistivity, that works fine.
Now I need to implement an electric current that follows
Where I0 and L are constants.
R is the resistivity (rho) integrated all over the conductor's domain, it reads:
I used "intop" to tackle this double integral over the conductor's domain, and the outer one is the length in the "z" direction.
COMSOL apparently does simulate with this setup, but the calculations are too too slow. It takes a lot of memory as well (plus than 80GB!) However, if I use I(t)=I0, it works nice and fast, so I'm sure there's a problem with the "intop" function.
So I ask you if there's something I am missing, or some suggestions to make the simulation faster.
Thanks in advance!
Lucas
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Heat Transfer - Liquid/Air
Hi,
the problem is, I have a hermetic area, which is filled with water and air. The water should have a higher initial value than the air, whereupon a heat transfer takes place from water to air. To model this, I selected two materials: Water & Air. For the Physics Interfaces I selected 'Nonisothermal Laminar Flow', which combines 'Heat Transfer in Fluids & Laminar Flow'. Trying to simulate it produces an error that it didn't converged. Which settings I have to set for the heat transfer between these materials?
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2D Plasma Simulation with Air Cooling on Dielectric/Coil Region - Error With Nonisothermal Flow
Hi,
I have not seen any tutorials or blogs of my particular problem so I'm at a loss of what to do. Here is what I expect to simulate:
I have an ICP plasma at 20 mTorr discharging a standard plasma of ~ 10^17 m-3 ne and ~ 3 eV. After some time, the plasma will heat up the dielectric and the heat will flow to the surrounding air and components. Air will flow from an inlet (due to a fan) and will cool the region via convection. The region will reach a steady state
I have "successfully" modelled the plasma as a heat source and have also included a boundary heat source between the plasma volume and the dielectric. The temperatures I am seeing after 1 hour of operation are similar to experimental results.
The problem is when I add in a turbulent flow module and I get this error:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
- Feature: Time-Dependent Solver 1 (sol1/t1) Undefined variable.
- Variable: comp1.nitf1.u_primez
- Geometry: geom1
- Domain: 4 Failed to evaluate Jacobian of expression.
- Expression: dvol_spatial(r(pi(2(comp1.ht2.d(-(comp1.ht2.res_prime((comp1.ht2.tau_primecomp1.ht2.rho)comp1.ht2.u_primez))))))) Failed to evaluate Jacobian of expression.
- Expression: (2comp1.ht2.streamlinepir)(dvol_spatial)
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
I'm not sure what "comp1.nitf1.u_primez" or what it has to do with the plasma (domain 4). I have not set any flows in Domain 4. All my flow and turbulence flow is in domain 10 (Air). The only clue to this problem that I can pick out is my Multiphysics module (Nonisothermal Flow 1) has Heat Transfer: Heat Transfer in Solids and Fluids 2(ht2) <- domain 4 (plasma) is calculated in that module for heat transfer. But the nonIsothermal Flow is trying to use it to calculate flow?
Basically I just want to simulate Air cooling to a steady state. How do I overcome this issue?
I have attached my model without solutions.
Any help is appreciated!
Kind regards,
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