Hi In case we want to simulate a heat transfer between two fluids and we anticipate to have a solid part added to the simulation later on, can we use the heat transfer in solids and fluids without having a solid domain? In fact, what is the difference between using two different physics for heat transfer in solids and heat transfer in fluids with having just one physic for heat transfer in solids and fluids? Thank you in advance for your answers.
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Differences between heat transfer in fluids and heat transfer in solids and fluids physics.
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Heat sink topology optimization study steps
Hey,
I'm trying to create an optimized heat sink topology using CFD and Heat Transfer physics, much like in www.comsol.com/paper/download/292201/haertel_paper.pdf . I have a 2D model where there's a design domain which is designated for Topology Optimization. Heat is generated in the domain with Heat Transfer interface and fluid flow past it is governed by Laminar Flow interface. Density Model is used to penalize fluid flow when density is present. I would like to use one-way coupling with the fluid flow mechanics and the heat transfer as is done in the paper I linked.
My problem is that the optimization solver seems to only update one solution step and just uses the first solution from preceding steps. In my case the initial fluid velocity field is used for all optimization iterations which is not what I want. I would like to solve the velocity field and the temperatures for each optimization iterations. How do I incorporate all the steps in to the optimization solution? I've attatched the model here.
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2D plot from a parametric sweep in 1D geometry
Hello I've performed a parametric sweep in 1D geometry and would like to plot some of the results as function of both the x coordinate and the parameter I'm changing. When I add a 2D plot group I can't choose any dataset to plot with. When I add 1D groups I can, so I suspect it's because the model geometry is lower than 2D... Any ideas how I could do this?
Thanks Eyal
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Unit syntax error with meshvol
In the variables section, I want to add meshvol into an equation of a variable. But (even if I only define a variable with the expression "meshvol") the error appears, and in the unit column it doesnt show me any unit.
When I solve my model, I can plot the meshvol as usual with the correct unit m^2.
How can I get the volume of each element as a variable to use it in an equation?
Thanks in advance, Peter.
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Dipole emission attenuation
Hi all,
I am working in Ray Optics where I'm modelling the rays emitted from a point source, an electic dipole. I have modelled it as an "Release from Point" where I determined the Total Source power per unit thickness to be 1 [W/m] and the emission to be spherical. The Ray Trajectories that are created by COMSOL seems to be correct geometry wise, but I get confused when I plot gop.I in the 2D Ray Trajectory plot. The intensity drops off immediately in a uniform way around the location of the dipole. This does not make sense since the material where the dipole is located in has no complex refractive index, so the intensity should not be decreasing so suddenly. Also when the rays hit a Material Discontinuouity their intensity remains unchanged, this also is not a correct representation of reality, right? With each reflection/refraction the intensity is supposed to change.
I attached an image to show how my ray trajectory plot looks right now, any help would be appreciated!!
Best, Karima
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PLANAR ELECTRODES IN COMSOL
HOW TO BUILD GEOMETRY OF NANOWIRE BETWEEN PLANAR OR POINTY ELECTRODES IN COMSOL
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Magnetic and Electric fields for coil coated with an electrically conductive material (two materials for coil)
Dear Comsol Community,
My objective is to observe the resonance for an inductor (coil thickness in range of micrometers) coated with a very thin electrically conductive material (1-2 um thick). I have generated a 2D axymmetric model for this purpose. I can easily simulate the resonance of the inductor alone (without the coating) with Magnetic and Electric fields (MEF) interface.
However, when I add another material on the surface of the inductor, an error is generated pertaining to the electric potential, an undefined variable - comp1.V. When I just use the Magnetic fields interface, there's no such error. As I see to it, the RLC coil group in the MEF interface computes the electric potential difference between the coil turns and assumes the potential to be the same across the coil cross-section, which isn't true in my case, as I have two materials associated on the coil domain. Is there any solution to modeling these thin domains surrounding the coils? I have attached the .mph file and generated error for your reference. Any help would be appreciated.
Cheers, Saoni
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How to have current continuity in different domains of my geometry?
Hi everyone, Some background: I am trying to find the magnetic field of this omega shaped wire inside a sphere. I used the Electromagentic Waves, frequency domain and I am doing a frequecy domain study. Some parameters to be exact I have a current at 1 [A/m] and a frequency of 2.97e9 [Hz]. I applied a surface current density of 1[A/m](exp(i2pi/(c_const/5freq))sys2.phisys2.r where my sys2 is the given cylindrical system in the definitions. Since, my structure is irregular and has 2 straights portion and one round portion, I want to have current equal and continous at both the 2 sraight parts and the round part. I am unable to find any help anywhere. So any help is appreciated, thank you. I am attaching my mph file and a picture of how I want the current.
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What is the difference between the two densities, that is, what is the difference between tpf1.rho2 and spf.rho?
From what I see both tpf1.rho2 and spf.rho are densities [kg / m ^ 3] and therefore the 1st expression of pressure units and the 2nd expression of force per unit volume [since z is the vertical coordinate and g_const is the acceleration of gravity]
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Can the current distribution shell physics interface be coupled with the transfer of dilute materials and the level set interface?
I want to study galvanic corrosion in the atmospheric environment and consider the influence of corrosion products on the corrosion process. Therefore, I want to combine the current distribution shell + transfer of dilute substances + level set. Is there any problem with this modeling idea? Can the level set only be used when the electrolyte area is drawn?
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the unit of reaction rate
Can the unit of reaction rate be customized in COMSOL?
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Porous Electrode vs Li metal half cell
Hello everyone, I am currently setting up a simulation of a half cell to evaluate the performance of a porous electrode material. I wanted to start from one of the application library examples, thought it would be straightforward to replace one of the porous electrodes in the 1D Li-ion baterry model for a surface electrode, but I couldn't get any results and keep getting lots of errors. Do you suggest I start from the 1D Li ion battery model or should I start from another one that already has a metal Li foil as a counter electrode? Or maybe I should build the model from scratch with PDEs? What would you recommend? Thank you in advance. Abigail
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Electric potential difference with respect to something
Hi,
I am using the electrochemistry module to model an electrode device in biological tissue in 3D. I can take a slice at x=0 of the yz-plane and plot the electrolyte potential as a surface plot. Is there a way of plotting the potential difference with respect to the potential at a particular height at say z=50um above the electrode surface.
Thanks emma
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How to do a parametric sweep with the Rayleigh number?
Hello, I've been doing some bouyancy simulation in a square cavity, specifically I've been following this tutorial:
https://www.comsol.com/model/buoyancy-flow-in-air-53441
Everything is okay, but I'd like to use a parametric sweep with the Rayleigh number, in the tutorial the Ra=1.1309E6, but I want to do some Ra=1E4 1E5 1E6 1E7, but how can I implement this?
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How to apply a travelling wave to a structure??
Hello, I am trying to design a stacked ring structure to which I want to apply a travelling voltage wave. Please help me out.
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wound rotor induction motor using rmm physics
Hi, I'm in need of a WRIM model on comsol cause i'm new to the software and i don't know all the settings i have to do before doing my study. Can you please help me ?
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3d analysis of inductively coupled plasma
Hi , we are performing a 3d analysis of inductively coupled plasma and have all the time same problem : Failed to find a solution. Divergence of the linear iterations. Returned solution is not converged. the file is in the attachment, Any ideas how I could fix this? Thanks for your help.
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Weird temperature jitters in my solutions
Hey comsolholics,
I'm currently running into a problem regarding the solutions of my additive manufacturing simulation. I expected values comparable to those of the last picture, which is a (much) older version of my current file.
Right now, while being a lot more accurate compared measured values, the simulation also spits out these jittery solutions. These jitters also seem to be random.
Could it be cpu load spikes throwing the simulation off?
Does anyone have any ideas as to why these effects occur? I'd be very grateful for your feedback.
Cheers,
Max
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Study settings
Hi,
I find different results for the same model while using different time range.
When I simulate the model with study (0,0.1,100) and simulate the same model with same study with range (0,0.1,200) I recieve different result and the simulation gives error due to singularity at around 63.
Why does this occur? Could anyone help me with this?
Thank you Nikhil
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Mesh warning (size): There is no feature using these settings
The below post is related to an archived discussion
[start here] Could someone please comment on this error? During my very first simulation, I have experienced such warning in the mesh module. Are we supposed to select a particular configuration for the element size (which is built-in) comsol itself? Please help me!! Thank you. -Nanda Kishore BM
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