Latest Discussions - COMSOL Forums https://www.comsol.com/forum/ Most recent forum discussions Mon, 13 May 2024 12:47:26 +0000 COMSOL Forum: Latest Discussions https://www.comsol.com/shared/images/logos/comsol_logo.gif https://www.comsol.com/forum/ Temperature difference boundary condition https://www.comsol.com/forum/thread/339471/Temperature-difference-boundary-condition?last=2024-05-13T13:55:35Z <p>Hello everyone,</p> <p>I want to define a boundary condition in which there is a constant value for the temperature difference of two surfaces. How can I define such boundary condition?</p> Mon, 13 May 2024 12:47:26 +0000 4.2024-05-13 12:47:26.339471 MATLAB COMSOL LIVELINK taking too much time to simulate https://www.comsol.com/forum/thread/339461/MATLAB-COMSOL-LIVELINK-taking-too-much-time-to-simulate?last=2024-05-13T11:46:57Z <p>Dear all, I am simulating coil strands to know its AC resistance. i am using matlab comsol to automate this task. however, for 10 turns coil with 100 strands, the total simulation time goes to 5 hours while for 10 turns with 300 strands, the total simulation time goes 50+ hours. by profiler code checking, i found that *** model.sol('sol').runAll;*** is taking 95% of overall simulation time. can you please suggests me to reduce the time duration of simulations. I am using regular mesh with minimal complexity.</p> <pre><code>best regards thanks </code></pre> Mon, 13 May 2024 11:46:57 +0000 4.2024-05-13 11:46:57.339461 Problem with magnetic field, magnetostriction https://www.comsol.com/forum/thread/339451/Problem-with-magnetic-field-magnetostriction?last=2024-05-13T11:40:05Z <p>Hi,</p> <p>So Im trying to solve the core noise by magnetstriction in a three phase transformer. But Im having problems with the magnetic field. Directly when i try to solve it an An unexpected error occurred and its very hard to understand how to fix that anyone had same or any solutions?.</p> <p>Tried to build the magnetic field same as this https://www.comsol.com/model/nonlinear-magnetostrictive-transducer-6063 But same thing An unexpected error occurred. And when i open log file its impossible to understand anything.</p> <p>I would really need help on this problem.</p> <ol> <li>Coil Geometry Analysis</li> <li>Time dependent</li> </ol> Mon, 13 May 2024 11:40:05 +0000 4.2024-05-13 11:40:05.339451 Failed to Evaluate Variable Jacobian Error. Please help me! https://www.comsol.com/forum/thread/339441/Failed-to-Evaluate-Variable-Jacobian-Error-Please-help-me?last=2024-05-13T00:57:41Z <p>Hello everyone!</p> <p>I encounted this problem when I was trying to do a study(simulation) with Plasma module and Magnetic Fields Module in comsol. When I tried to include plasma domains to magnetic fields module, following error has happened. I attached my .mph file too!</p> <p>The error message is following:</p> <ul> <li>Feature: Time-Dependent Solver 1 (sol1/t1) Undefined variable. <ul> <li>Variable: comp1.mf.iomega</li> <li>Geometry: geom1</li> <li>Domains: 10-11, 13, 29, 32, 53 Failed to evaluate Jacobian of expression.</li> <li>Expression: dvol_spatial<em>(comp1.mf.d</em>comp1.mf.Jz) Failed to evaluate Jacobian of expression.</li> <li>Expression: (comp1.mf.d<em>(-comp1.mf.Hx</em>comp1.mf.testcurlAx-comp1.mf.Hy<em>comp1.mf.testcurlAy-comp1.mf.Hz</em>comp1.mf.testcurlAz+comp1.mf.Jx<em>var(comp1.mf.Adepx,comp1.A)+comp1.mf.Jy</em>var(comp1.mf.Adepy,comp1.A)+comp1.mf.Jz<em>var(comp1.mf.Adepz,comp1.A)))</em>(dvol_spatial)</li> </ul></li> </ul> Mon, 13 May 2024 00:57:41 +0000 4.2024-05-13 00:57:41.339441 My FRF study is not showing anything https://www.comsol.com/forum/thread/339431/My-FRF-study-is-not-showing-anything?last=2024-05-13T07:20:43Z <p>Hello! Please help me, when i do a study for frequency domain, in my results- nothing is showign? it is saying pressure, discplacement etc. is all zero, i dont understand why? I have chosen the entire geometry when performing the study. And when i perform an eigenfrequency study for the same construction, i get results but not when i perform an frequency domain study.</p> Sun, 12 May 2024 16:38:43 +0000 4.2024-05-12 16:38:43.339431 Transport of dilluted species and electrostatics https://www.comsol.com/forum/thread/339421/Transport-of-dilluted-species-and-electrostatics?last=2024-05-12T11:40:39Z <p>am studying the in fluence of suspended metallic dust particles in mineral oil under positive lightning impulse voltage . A cylidrical 1 litre point - plane test cell with a gap distance of 60 mm will be filled with mineral oil ( with and without contamination). The objective of the research is to determine the influence of suspended metallic dust particles on streamer velocity. A model has to be developed and simulation results have to be compared with experimental set results. How do l implement it using electrostatics and the transport of diluted species physics.</p> <p>Your help is appreciated. I have been struggling for the past 6 month.</p> <p>Regards</p> <p>Amos</p> Sun, 12 May 2024 11:40:39 +0000 4.2024-05-12 11:40:39.339421 Counting Particle Types at Outlet for Particle Tracing for Fluid Flow feature https://www.comsol.com/forum/thread/339411/Counting-Particle-Types-at-Outlet-for-Particle-Tracing-for-Fluid-Flow-feature?last=2024-05-11T16:25:33Z <p>Hi, I am simulating a microfluidic spiral channel. I have used the particle tracing feature and inputting 3 types of cells; Circulating Tumor Cells (CTC), Red Blood Cells (RBC) and White Blood Cells (RBC) according to their own particular size and density. CTC - 15 um - 1077 kg/m3 WBC - 10 um - 1080 kg/m3 RBC - 6 um - 1110 kg/m3</p> <p>The results are well, showing the particle separating and eventually CTCs are separated from the RBCs and WBCs. Majority of CTCs ending up in outlet 1 while RBCs and WBCs end up in outlet 2. However, is there a proper way for me to tabulate a graph showing the types of cells and number of cells at the outlet? I do not want to tabulate the graph showing total number of cells as I want to distinguish between the number of CTCs, RBCs and WBCs at both outlets.</p> <p>I have reviewed this blog: https://www.comsol.com/blogs/different-ways-to-count-particles-in-comsol-multiphysics/ But it shows methods to count total number of particles and not specifying the different particles.</p> Sat, 11 May 2024 16:25:33 +0000 4.2024-05-11 16:25:33.339411 Problem with RF Port Sweep https://www.comsol.com/forum/thread/339402/Problem-with-RF-Port-Sweep?last=2024-05-10T23:19:04Z <p>I am doing port sweep to export the SNP file. After the first port converges, for some reason the solver does switch to the next port. Please see the image attached. In a separate simulation file, I have activated each ports manually and the simulation works fine in that case.</p> Fri, 10 May 2024 23:19:04 +0000 4.2024-05-10 23:19:04.339402 Is it possible to use topology optimization to add additional material to a solid structure, rather than removing material? https://www.comsol.com/forum/thread/339392/Is-it-possible-to-use-topology-optimization-to-add-additional-material-to-a-solid-structure-rather-than-removing-material?last=2024-05-13T07:25:07Z <p>Hello,</p> <p>I'm trying to model a loudspeaker enclosure in 2D and use topology optimization to increase the low frequency response by adding additional material to the inside of the enclosure. My goal is a simplified version of this research article:</p> <p><a href="https://www.researchgate.net/publication/376153843_Loudspeaker_cabinet_design_by_topology_optimization">https://www.researchgate.net/publication/376153843_Loudspeaker_cabinet_design_by_topology_optimization</a></p> <p>I've already simulated the initial design, but am having trouble with the optimization step. All of the tutorials I've found on topology optimization involve removal of material, not adding any additional material.</p> <p>Attached are screenshots of my model and some of the results of the research paper for reference. I'm trying to add additional material to the orange fiberboard in the inner region which is occupied by air, similar to the paper. Any help or guidance would be much appreciated.</p> Fri, 10 May 2024 11:53:51 +0000 4.2024-05-10 11:53:51.339392 MUMPS error https://www.comsol.com/forum/thread/339391/MUMPS-error?last=2024-05-10T05:58:56Z <p>Dear sir/ma'am, I am getting a warning "MUMPS memory allocation factor increased to 1.4399999999999999." while running the model.What does it mean and how to resolve it? Shall I increase MUMPS allocation factor? What should be its upper limit? Thanks and Regards</p> Fri, 10 May 2024 05:58:56 +0000 4.2024-05-10 05:58:56.339391 Questions about background reduced field in COMSOL Magnetic field module? https://www.comsol.com/forum/thread/339383/Questions-about-background-reduced-field-in-COMSOL-Magnetic-field-module?last=2024-05-10T12:33:05Z <p>In the frequency domain research mode of COMSOL, we want to apply an AC magnetic field superimposed by a DC magnetic field, in which the AC field is applied through the coil. Can we regard it as a DC magnetic field by setting the background reduced field to a constant(In the two-dimensional axisymmetric model, the background field is set as the axial uniform magnetic flux density and is a constant) ? Or is the background reduced field a DC magnetic field or an AC magnetic field in the frequency domain? Thanks!</p> Fri, 10 May 2024 04:00:47 +0000 4.2024-05-10 04:00:47.339383 Ionic motion in dielectric substrate: structure alterations https://www.comsol.com/forum/thread/339382/Ionic-motion-in-dielectric-substrate-structure-alterations?last=2024-05-09T20:43:23Z <p>Hi, I am simulating ionic migration in dielectric substrates under electric field. I am using electrostatic and transport of diluted species. Everything is fine up to this point.</p> <p>When the positive ions move from the positive electrode to the negative, for glassy structures, I want to alter the structure left behind. Experimentally this is achieve by applying electric field and temperature. When the ions move, the structure changes in that region as one of the mechanisms of charge compensation.</p> <p>How can I simulate this changes in structure?!</p> <p>Thanks in advance!!!</p> Thu, 09 May 2024 20:43:23 +0000 4.2024-05-09 20:43:23.339382 CFD module https://www.comsol.com/forum/thread/339373/CFD-module?last=2024-05-09T18:01:48Z <p>What is the difference between "slip" and "Navier slip" in the "wall" condition of a "laminar flow" module? As we all know, in microchannels, surface tension, EDL and other factors will affect the flow rate. How to couple multiple factors into the flow rate? In the wall setting, only one of the factors such as slip type and electroosmotic speed can be selected. Can all of them be coupled into a microchannel model? Could you please provide me with a detailed procedure or case? Thank you.</p> Thu, 09 May 2024 14:49:51 +0000 4.2024-05-09 14:49:51.339373 Precipitation and Evaporation in Porous Media settings https://www.comsol.com/forum/thread/339353/Precipitation-and-Evaporation-in-Porous-Media-settings?last=2024-05-09T13:06:11Z <p>Hi!</p> <p>I am currently modeling a 2D Porous media simulation in a coastal settings.</p> <p>Here, I would like to simulate how salt content evolve overtime. I have the precipitation and evaporation data at the moment. However, I recall COMSOL does not allow inlet and outlet condition within one boundary (i.e., top soil layer).</p> <p>are there any suggestions on this matter?</p> Thu, 09 May 2024 13:06:11 +0000 4.2024-05-09 13:06:11.339353 How to Obtain a 2D Projection Averaging Concentration Along the Z Axis? https://www.comsol.com/forum/thread/339341/How-to-Obtain-a-2D-Projection-Averaging-Concentration-Along-the-Z-Axis?last=2024-05-09T12:50:33Z <p>Hello everyone,</p> <p>I'm currently working on a simulation involving the mixing of two products within a microfluidic chip using COMSOL Multiphysics. I have successfully completed the simulation, but now I'm trying to generate a 2D projection of the average concentration in the XY plane by averaging values along the Z axis. This way, I can directly compare the simulated results with my experimental data.</p> <ul> <li>The Challenges I'm Facing: I have tried using the Results section and the various Data Sets options, but I couldn't find a straightforward way to average the concentration data along the Z direction. I'm not sure how to set up a custom 2D Plot Group that can represent the average concentration.</li> <li>What I'm Looking For: A method to generate a 2D plot that shows the average concentration values in the XY plane, averaged along the Z direction. Suggestions or advice on how to export these results in a format that can be compared with my experimental data. I'd greatly appreciate any insights or recommendations you could provide to help me visualize and export this 2D projection properly.</li> </ul> <p>Thank you in advance for your help!</p> <p>Best regards, Francesc</p> Thu, 09 May 2024 11:11:08 +0000 4.2024-05-09 11:11:08.339341 How to calculate the co and cross polarized transmittance/reflectance in Comsol? https://www.comsol.com/forum/thread/339331/How-to-calculate-the-co-and-cross-polarized-transmittancereflectance-in-Comsol?last=2024-05-09T13:56:10Z <p>In Comsol, I want to calculate the Txx(transmittance to x polarized for incident x polarized), Txy(transmittance to x polarized for incident y polarized), Rxx, Rxy, and so on in comsol. S21/S11 never gives info about the particular polarization, it gives the overall transmittance and reflectance. But how to find these components in COMSOL?</p> Thu, 09 May 2024 04:27:11 +0000 4.2024-05-09 04:27:11.339331 Disabling variables in study step https://www.comsol.com/forum/thread/339322/Disabling-variables-in-study-step?last=2024-05-08T20:18:16Z <p>I am working on a heat transfer problem that requires me to calculate a variable (let's call it X, defined in "Variables 1") as the first step. X is defined as 2Y - 10, where Y is a state variable (defined in "State Variables 1") that is being updated after each timestep. In the second study step, I need to use the last computed value of the variable X in the physics and solve again. Which means that the variables should not be solved for in the second step.</p> <p>I am implementing a two study scheme, where in study 1, I run the physics while computing X and Y. In study 2, I am disabling "Variables 1" and "State Variables 1", and setting the values of the variables not computed for through the previous solution. When I run this, the first study runs successfully, but the second study throws an error saying variable X is not defined. I understand that this might be because I am disabling the variables in the study, but I am not sure how else to not solve for the variable and state variable in the second study, while still using the last stored values.</p> <p>Would be of great help if anyone can guide me to implement it properly.</p> <p>Thanks!</p> Wed, 08 May 2024 20:18:16 +0000 4.2024-05-08 20:18:16.339322 Failed to evaluate AWE expression. Not all parameter steps returned. https://www.comsol.com/forum/thread/339312/Failed-to-evaluate-AWE-expression-Not-all-parameter-steps-returned?last=2024-05-10T17:11:11Z <p>Hello,</p> <p>I am getting the error "Failed to evaluate AWE expression. Not all parameter steps returned." when running an Adaptive Frequency Sweep study for an Electromagnetic Waves, Frequency Domain physics. The model is a waveguide antenna with two lumped ports in a coaxial configuration. I run a "Frequency Domain Study" and it converges with no problem. But when I run "Adaptive Frequency Sweep" from 3 GHz to 4 GHz, in order to plot S11 parameters vs frequency, solution does not converge. I tried both Direct solving with MUMPs and Sugessted Iterative Solver, but they both did not converge. I am confused why this is the case since the "Frequency Domain" problem converges without a problem. Is it possible adaptive frequency sweep doesn't work properly when you have more than one excited lumped port?</p> <p>I can't attach my file as it is too large but I have attached a screen shot.</p> <p>Any information would be greatly appreciated.</p> Wed, 08 May 2024 20:05:33 +0000 4.2024-05-08 20:05:33.339312 Rapid solidification https://www.comsol.com/forum/thread/339302/Rapid-solidification?last=2024-05-08T19:16:08Z <p>Apologies, as I am fairly new to COMSOL.</p> <p>I am trying to simulate using a pulsed laser to melt and recrystallize silicon. Right now, I am just trying to model the rapid solidification after the melting has been done. I am doing a 2D simulation with a 10 um x 10 um piece of Si using heat transfer in solids and liquids with a time-dependent study. I am starting with a 100 nm thick layer of liquid Si at the top of the sample. For the sides, I have periodic boundary conditions, and the bottom is held at constant temperature. I also have surface-to-ambient radiation on the top surface. I give it an initial temperature distribution where the interface is at the melting point of Si, and then there is a linear temp distribution in the solid that goes from the melting temp to room temp. In the liquid layer, I set the top surface to be at a temperature higher than the melting temp and again use a linear temp distribution in that layer.</p> <p>What I am ultimately trying to get is the position of the liquid/solid interface as a function of time. Right now, it is working to the point that I can see the interface move towards the top surface with time, but the simulation gets an error at one point that is due to the mesh. Then it stops the simulation at that point, but it does give me all the data for the time points before that happens. I believe that when the liquid part is completely solidified, it has zero thickness, so when it tries to mesh, it can't make an appropriate mesh element, which is why it gives the error.</p> <p>I have two questions:</p> <ol> <li><p>Is there a way to tell the simulation to stop once the top layer is fully solidified so that I don't get this error?</p></li> <li><p>How can I extract the position of the interface as a function of time?</p></li> </ol> Wed, 08 May 2024 19:16:08 +0000 4.2024-05-08 19:16:08.339302 How to input a no rotation constraint https://www.comsol.com/forum/thread/339292/How-to-input-a-no-rotation-constraint-?last=2024-05-08T17:48:07Z <p>Im working on the same system I need to put a no rotation constrant on the top face of the lower flexure.</p> <p>I added the image of the location of the no rotation constrant and a pdf of the system. In addtion I attach the mph file of the system.</p> <p>What i did was I use a rigid connector at the location and constrant it rotation however I suspect it does not work correctly because in the first 2 mode the flexure is not bended correctly and the system was not rigid.</p> <p>If there an another way to put a no rotation constrant on the solid mechanics interface that will be perfect.</p> <p>Any help will be very useful.</p> Wed, 08 May 2024 17:47:45 +0000 4.2024-05-08 17:47:45.339292