Hi all, I'm making a model of u-tube inside a cylinder by using Pipe Flow Module. The model is symmetric along the cylinder and tube length, but I could not make the symmtry BC to include the pipe (because it is lines in 3D). Thanks for your help.
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Is it possible to have a symmetry along pipes when using Pipe Flow Module?
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Modelling nano particles in RFA of hepatic tumour
I am new to comsol. Facing problem to model nano particles in biotissue. Can anybody please tell me the approach to solve this problem.
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Changes in piezoelectric material parameters
Hello everyone, I am doing a simulation of piezoelectric materials. I want to know if the cutting angle of the piezoelectric material is set in the rotating coordinate system in COMSOL, will the piezoelectric material constant such as the elastic matrix and the piezoelectric matrix change?
Can anyone help me in this regard? It will be a great help for me.
Looking forward for your kind reply. Thanking you Sincerely .
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What is the differance between solving using modes and solving using input beam?
Hello, I have created 2D simulation of directional coupler, and I excite it using a beam from an input port. I know that in case of solving the problem using mode analisys - I am sepposed to get sinosodial oscilations of the power inside the each waveguide, as the mode "jumps" from one waveguide to the other. however, in my simulation (when the waveguides are exited using an input beam), I get the attached graph (power inside both waveguides vs coupler length). As can be seen, the amplitude of the oscilations changes. what is the different between solving with mode analisys and solving using input beam? why is my amplitode not constant?
I use port to input a gaussian beam, with total width of the entire coupler - so that both waveguides are exited simultanisly and equally. For bounderies I use Matched Boundary Condition.
Thank you for your help!
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How to prescribe displacement amplitude
Hi all
Is it possible to prescribe the displacement amplitude of a boundary in XYZ coordinate? For instance, in the attached file I try to change the amplitude by scaling the "Prescribed in y direction" by a factor of 1000 but the amplitude is still the same.
Derry
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Solving coefficient form of PDE and laminar flow for a heat transfer problem
Hi everyone,
I am trying to solve a multiphysics problem in a complicated 3D domain of fluid and and solid medium. Governing equations, solved for are Continuty, Momentum and a Modified Energy equation. Physics that I am using in COMSOL are Fluid flow and Coefficient form PDE. I am using Fully coupled direct linear time dependent solver. Degrees of freedom solved for=1758657, total mesh number of elements=1200134, avg element quality=.7399, min element qualiyy=1.02e-5
During simulation, after 0 time step, its showing "Inconsistent unidirectional constraints found. 1860 constraint force columns are merged/removed." And the solver is taking too long time to solve the problem. It takes 4 days already for just 20 sec study out of 650 sec in my model. I am using double processor(XEON) workstation with 64 gb RAM. 1758657
Can anyone help me in this, to know the reason behind it and how to reduce the solution time.
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Combustion of Rocket Propellant
I want to do combustion simulations of sandwich solid propellant. Previoulsy simulations are done in ANSYS Fluent, but for COMSOL I am wondering where to start. Can any one help me in this regard.
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Insolation analysis and temperature profile
Hi all, I'm new on this forum and I'm trying to figure out if COMSOL can help me in the study I'm doing.
I have to analyze how the heat propagates inside a boulder. For doing this I separetely created a mesh and I already calculated the insolation values for a certain time step. The output is tables with this values.
My question is: can I import in COMSOL these outputs? If yes, can I create a temperature profile starting from these values? Thanks for any answers.
Pamela
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LiveLink with Excel - extract data from an exiting Table
Hello,
I am trying to extract data from the results and show it in excel. I followed the following procedure:
- In COMSOL I was able to define a table and save its content on an excel file
- Saved the mph as VBA
- open excel and pates the VBA code into a new module
- run the script
Up to now everything was OK.
So I have a table (tbl1) with two columns (frequency and gain) Now I need to perform what in Matlab code would be
Gain = mphtable(model,'tbl1'); Freq=Gain.data(:,1); Gain_dB=Gain.data(:,2);
I could not find the VBA equivalent of these 3 MATLAB lines (and yes, I did looked into the LiveLink for Excel, but in the EXTRACTING DATA section I was not able to find what I was looking for, or misinterpreted)
Any ideas?
Thanks
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Graphing cut line of a solution divided by a point probe value
Good morning,
Thank you in advance for any help you can provide.
I have an EM simulation in which my region of interest is a cut line. I wish to plot to plot normE of the solution divided by the value of the normE at the origin (which I have from a probe). What is the easiest way to do this? I will describe what I have already tried down below.
Thanks!
Already tried: * I defined a point probe at the origin, then changed the expression to be es.normE. Directly trying es.normE/comp1.V works, es.normE/comp1.normE gives an error. * Next, I tried to use "Join"->"Explicit" to join the cut line and probe data points. Unfortunately, I keep getting the following error: "Operation cannot be performed on data set cpt1 (Cut point 3D); - Plot: previewplot1 (Line)"
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stationary study for a "Equilibrium Discharge Heat source" never converges
i tried a very simple model of "electric current" + "Heat transfer" in an argon medium, i added the "Equilibrium Discharge Heat source" to get the joule heating in the gas, the model boundaries are all defined and electric current density is applied at a small area represent the cathode tip and the ground is at another side to represent the anode, the time dependent study works without a problem, however just changing the study to stationary, the model just never converges with many meshes and the temperature blow up to 10s of billions at the very few iterations/steps. this only happen if i add the Equilibrium Discharge Heat source, without it the model converges perfectly. is there any solver modifications that can lead to a good stability of the solution, this is not a time dependent problem, and many authores solve it easily with the stationary methodes.
Thanks
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Large Deformations by concentration influx
I am trying to model expansion of a thin film due to concentration influx. I have coupled concentration to Solid Mechanics using analogous thermal strain (both are volumetric expansions) The problem I am facing is that everytime I tick the box - Include Geometric Non-Linearities, my solution does not converge or I get unreasonable output.
Any suggestions?
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Problem: Material, Boundary Conditions, etc. change during Parametric Sweep
Hello there
I try to make a Parametric Sweep over the width/depth of some material elements(rectangles in different materials). Unfortunately, the sweep stops all the time and everything has changed: The periodic boundary conditions have shifted to the inner edges, the materials have been swapped, the mesh settings of the different rectangles have swapped, etc. How can I avoid this?
I'm using Comsol 4.3, RF modul, Frequency Domain
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Evaluating Volume in Livelink
Hello
I am trying to use Livelink to create a geometry in Matlab which I will then run a model on later. To build my geometric sequence I need a way of accessing properties such as the total volume of the currently built geometry. Is there a way to do this in Matlab. I need basically information similar to what the measure function in COMSOL would give me or that I would get using a volume integral probe over all the domains but in Matlab.
The way I found of doing this so far seems rather convoluted, I created a probe, ran a blank study from Matlab, exported the probe table and loaded it back into Matlab to give me the volume.
Best wishes,
David
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Elasticity matrix and coupling matrix for polyamide
Hi,
I need Elasticity matrix and coupling matrix for polyamide. Will appreciate support
thanks
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Attempt to evaluate nonintegral power of negative number error message
Hello comsol community,
I am a bit struggling on this error message. I am relatively new to COMSOL. So not quite familiar with what went wrong. Any sort of comments and guidance will be much appreciated. I see the following error
"Feature: Stationary Solver 1 (sol1/s1) Attempt to evaluate nonintegral power of negative number. - Function: ^ Failed to evaluate variable. - Variable: comp1.i_0 - Defined as: (((k0F)(comp1.C_l_r^aA_ca))((C_s_max-comp1.C_s1)^aA_ca))(comp1.C_s1^aC_ca) Failed to evaluate variable. - Variable: comp1.i_n - Defined as: (comp1.i_0(exp(((FaA_ca)comp1.eta_act)/(RT))-exp((comp1.eta_act(F(-aC_ca)))/(RT))))/(unit_m_cf^2) Failed to evaluate expression. - Expression: comp1.i_n Failed to evaluate operator. - Operator: comp1.linext1 - Geometry: geom2 - Boundaries: 3, 6 Failed to evaluate expression. - Expression: comp1.linext1(comp1.i_n) Failed to evaluate expression. - Expression: d((-comp1.linext1(comp1.i_n)test(comp2.C_s)/F)(dvol_spatial),{test@1}) Failed to evaluate Jacobian of expression. - Expression: (-comp1.linext1(comp1.i_n)test(comp2.C_s)/F)*(dvol_spatial)"
I would like to focus on the first part which is - Attempt to evaluate nonintegral power of negative number. - Function: ^ Failed to evaluate variable.
Can someone please explain what is going on here ? Please let me know if the forum needs further info. Many thanks !
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Utilize the same Stationary solution multiple times.
Good day I want to use a stationary solution as the initial input for multiple time dependent steps, but I do not know how to. I'm actuallty confused by the options given.
I can use one stationary solution for a time study after the stationary step. But not for another time dependent step that comes after the first one. I want to test out different options and use the stationary study as the initial input.
Thanks in advance for any help.
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FLUX VARIABLES
Hi community,
I would to know the differents concepts of flux variables. For example, what is the difference between "normal total heat flux" (32.701 W/m) and "internal normal conductive heat flux, downside" (5.0 W/m)? And, aswell as "internal normal total energy flux, downside" (5.0 W/m) and "internal normal total flux, downside" (5.0 W/m)? In the diagram adjointed, the central part has an imput heated source of 5W and the lateral an input of 8W. Also, heat flux in the external laterals boundaries are considered and initial temperature conditions... The values in () are the obteneidte after the simulation. Considering Line Integration. The diagram is a consideration of an apparatus based on the norms ASTM C177 and ASTM C1073.
If you have similar works, please share with me! Best regards,
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Error when opening COMSOL
Hello, I recently encountered a problem while opening COMSOL multiphysics which gave me and error, stating that an unexpected error has occured and that I should look to the end of the log file.
Here's the log file generated by COMSOL:
'.', hexadecimal value 0x00, is an invalid character. at System.Xml.XmlEncodedRawTextWriter.InvalidXmlChar( Int32 ch, Char* pDst, Boolean entitize) at System.Xml.XmlEncodedRawTextWriter.WriteElementTex tBlock(Char* pSrc, Char* pSrcEnd) at System.Xml.XmlEncodedRawTextWriter.WriteString(Str ing text) at System.Xml.XmlWellFormedWriter.WriteString(String text) at System.Xml.Linq.ElementWriter.WriteElement(XElemen t e) at System.Xml.Linq.XElement.WriteTo(XmlWriter writer) at System.Xml.Linq.XNode.GetXmlString(SaveOptions o) at Comsol.Communication.ChannelBasedCommandManager.Se ndCommand(OutgoingCommandHandler commandHandler) at Comsol.Communication.BridgeCommandManager.Outgoing CommandHandler.Run() at Comsol.Communication.BridgeCommandManager.RunAndWa it(BridgeCommand command) at ComsolDesktop.MainWindow.StartJava(Boolean debug, Boolean devPlugins, NDisconnectInfo disconnectInfo, IBridgeCommandManager oldMgr) at ComsolDesktop.App.OnStartup(StartupEventArgs e) at System.Windows.Application.<.ctor>b__1_0(Object unused) at System.Windows.Threading.ExceptionWrapper.Internal RealCall(Delegate callback, Object args, Int32 numArgs) at System.Windows.Threading.ExceptionWrapper.TryCatch When(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
So if anyone has an idea as to where this might be stemming from, any help would be appreciated. thanks in advance.
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Plot new physical variables
Hi all,
I am new to COMSOL and just studied the Plasmonic Wire Grating tutorial using Wave Optics model.
The only variables plotted in the tutorial are the Electric field and the Transmittance, Absorbance and Reflectance. I want to plot other variables such as field intensity as a function of x, for example.
I have already been advised to use the "Replace Expression" feature, but I am unable to find it. I enabled "Equation View" where it shows variables like "Surface current density, x component" (see figure eq_view.png) but don't know how to plot it.
How can one see all functions COMSOL had by default and is there a tutorial about the syntax used by COMSOL to insert new functions?
Regards, Jorge
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