Latest Discussions - COMSOL Forums Most recent forum discussions Sat, 19 Sep 2020 18:19:36 +0000 COMSOL Forum: Latest Discussions Laminar flow <p>Hi, I am new to comsol. In comsol I have to draw L-shape tube for laminar flow. How can i draw L-shape(edges should be in curve) tube with 2 cylinder in 3D.I tried to design. But i couldnt design with 2 cylinder. Can anyone tell me how to design ? Thanks Prisilla</p> Sat, 19 Sep 2020 18:19:36 +0000 4.2020-09-19 18:19:36.269191 SNR and S-parameter plotting help <p>Dear All,</p> <p>I am studying with Bioheat and Electromagnetic Waves, Frequency Domain on COMSOL. I want add Signal to Noise (SNR) counter results and S-parametric plots. Please anyone who can help me.</p> <p>Thank You, Amare A.</p> Sat, 19 Sep 2020 11:48:27 +0000 4.2020-09-19 11:48:27.269171 Transient analysis repeated error test failed <p>The original parameters of the material are used, and the transient analysis results normally. When a certain parameter of the material is modified and the solver uses the default settings, when the transient analysis is run again, the repeated error test fails, singularity may occur, and the last time step does not converge. . For this kind of error, how should I solve it.</p> Sat, 19 Sep 2020 11:30:00 +0000 4.2020-09-19 11:30:00.269163 Layered Shell impacted with a hemisphere <p>Hello Everyone, I am seeking some help and guidance to simulate a contact study where a layered shell (composite laminated) is impacted with a hemisphere using different impact energyies. I am new to Comsol environment, so I would like to know if this simulation can be done using comsol? Secondly, which physics and study are suitable? I have tried using structure mechanics (layered shell) --> contact pairs, but the simulation takes long time and sometimes I get an error (" no enough space"). Your help is much apperciated.</p> Sat, 19 Sep 2020 11:14:41 +0000 4.2020-09-19 11:14:41.269153 Negative index of refraction for Time Dependent Model <p>We have been working to model Chrenkov Radiation in COMSOL. To do this we have set up a charge density to move along a path as a gaussian function. Whenever we have the real part of the permitivity less then zero, for some reason this gives us a computational error for some reason in our outputs.</p> <p>Is there a problem running time dependent EMW with epsilon_r&lt;0?</p> Sat, 19 Sep 2020 01:22:56 +0000 4.2020-09-19 01:22:56.269112 What is the proper way to cite my comsol license on a paper? <p>What is the proper way to cite my comsol license on a paper?</p> <p>Do I have to cite my key license?</p> Fri, 18 Sep 2020 18:19:27 +0000 4.2020-09-18 18:19:27.269082 Second order acoustic pressure(p2) <p>hi guys,</p> <p>I'm new to acoustic module but I know the theory of acoustic. I need to find the contour of the second pressure(p2) which is calculated by perturbation method(p=p0+p1+p2) , but can't find it anywhere. does anyone have any idea how to calculate p2?</p> <p>kind regards</p> Fri, 18 Sep 2020 18:03:05 +0000 4.2020-09-18 18:03:05.269081 E-Field inside a metal slab with a spherical void <p>So, I have two electrodes in my structure. The structure is given in the attached file. Basically, it shows a copper anode (blue) on top and a copper cathode (blue) at the bottom -- at a distance of 200 Angstroms. The bottom cathode has a spherical cavity close to the surface. Cathode is grounded and anode voltage is 10 V, yielding an "average" field of 5e8 V/m. Since the cavity is close to the cathode surface, there is a very thin "covering" of copper.</p> <p>The sphere inside the copper cathode is of radius 10 angstroms and centered at (0,0,39.22) angstroms. The bottom surface of the cathode is at z = 0 angstroms and the top surface is at 54.22 angstroms. So, the center of sphere (hole) is at a depth of 39.22 A, and has a radius of 10 A ==> the top of the hole is at 49.22A. This leaves 54.22-49.22 = 5 A thin slab above the hole roughly. Process used to create spherical void/hole: I created the copper slab first, then the sphere and used the difference boolean operator to remove the sphere from the copper slab/block. (This is the correct process to create the void I hope?) In case of the space between the cathode and anode, I created another block between these and assigned its material to air.</p> <p>I find no field in the cathode. I was thinking that since the "cover" above the sphere is so small (Angstrom scale), some E-field penetration could be expected even if the cathode is a metal (Copper).</p> <p>I was wondering if my use of the built-in model or boundary conditions lead me to E=0 in the metal? Or is it real and the field should indeed be zero?</p> <p>Also, attaching my model herewith.</p> Fri, 18 Sep 2020 17:17:55 +0000 4.2020-09-18 17:17:55.269062 How to modify the Solver to increase the time-steps only around pulses? <p>I am trying to simulate the voltage of a primary battery cell by applying a pulsating current. The battery should be functional for more than 5 years with this current.</p> <p>Because the pulses are small (less than 8 seconds), the timestep should be very small. But having a 1-second time-step for 5 years exceeds COMSOL's capability, so I was wondering what is the best option for this. If I choose <strong>Strict Time Stepping</strong> and 1 s time-step, it works very nice for a shorter time range, but if I choose <strong>Free Time Stepping</strong>, the solver jumps over the pulses. However, the <strong>Strict</strong> option is limited by the maximum number of time steps allowed in COMSOL. My question is...</p> <p><em>Is it possible to modify the solver so that it will have a higher density of time-steps around the 8s pulses and coarser otherwise? The pulses are generated using an analytical function</em></p> <p>I have created a simplified model to illustrate this issue (see attachment).</p> <p>If one goes to:</p> <blockquote> <p>Study 1 > Solver Configurations > Solution 1 > Time-Dependent Solver 1 > Time Stepping Option</p> </blockquote> <p>and chooses <strong>Free</strong> in the "Time steps taken by the solver", one can see that the capacity (Q in the results) jumps over the pulses. If one chooses <strong>Strict</strong>, it will calculate the capacity without any issues, as expected.</p> <p>However, for simulating a 5-year range, for the second option, the time-steps should be minimum 100 s, which would jump the 8s pulses and will take a long time (sometimes COMSOL freezes if I use 100 s and 5 yr range).</p> Fri, 18 Sep 2020 16:23:28 +0000 4.2020-09-18 16:23:28.269052 AC current on food filled cell <p>Dear all,</p> <p>I want to simulate the electromagnetic heating generated by AC courrent passing througouth potateos food packed beetween 2 electrodes. I'm using "Electric Currents" and "Heat transfer in Solids" modules coupled by electromagnetic heating. I'm simulating with "frequency domain" (50Hz) for electric current and "time dependent" study for heat transfer. Is a good solution to simulate the illustrated problem or someone suggest me something better?</p> <p>Thanks, Francesco</p> Fri, 18 Sep 2020 14:11:09 +0000 4.2020-09-18 14:11:09.269051 What could be the issue with the analytic function? <p>Hi,</p> <p>I created an analytic function in the global space with the following expression and tried to plot it. However, it doesn't seem to give the expected graph(Please see the graph produced with Matlab). Could someone kindly explain me what I'm missing here?</p> <p>Expression: exp(-x^2/w^2)+ exp(-(x-d)^2/(w^2))+ exp(-(x+d)^2/(w^2))</p> Fri, 18 Sep 2020 10:13:03 +0000 4.2020-09-18 10:13:03.269042 Physics selection for biological cartilage <p>Hi, I am new to COMSOL. I need to design human Intervertebral disc ( cartilage) in Comsol. My Intervertebral disc design consists of three layer and by varying the nutrition concentration supplied to intervertebral disc, degeneration of disc is studied. I dont know what physics to be choosed to design my geometry. What physics has to be choosed for this study? Can you help me in this querry.</p> Fri, 18 Sep 2020 09:17:00 +0000 4.2020-09-18 09:17:00.269041 [mesh] reference and scale error <p>It is a file that can be interpreted normally I tried running the interpretation again after adjusting the reference->scale, but I am getting this error. I am curious about what error it is.</p> <hr /> <p>Problem setting up multigrid. Multiple problems occurred when building the mesh. - Features: Reference 1/Reference 1/map 1, Reference 1/Reference 1/map 2, Reference 1/Reference 1/swept mesh 1 Failed to create mapped mesh for face. - Face: 28 Failed to create matching edge discretizations. Error in multiphysics compilation.</p> Fri, 18 Sep 2020 06:46:35 +0000 4.2020-09-18 06:46:35.269033 engineering <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>[start hello iam student master degree and i want to measure stator current in comsol in single phase induction machine</p> Thu, 17 Sep 2020 21:49:50 +0000 4.2020-09-17 21:49:50.269011 Eigenfrequencies not changing after a load has been applied <p>Hello all,</p> <p>I am trying to perform a simulation wherein I study the Eigenfrequencies of an object that has been deformed using a predefined point load.</p> <p>I am using Solid mecahnics &lt; EigenFrequences, Prestressed module.</p> <p>The issue I currently keep having is that the compiler is only calculating the Eigenfrequencies from before the deformation and isn't taking the deformation into account. So, I end up with the same Eigenfrequencies irrespective of the load applied.</p> <p>Any help would be appreciated. Thanks!</p> Thu, 17 Sep 2020 17:00:25 +0000 4.2020-09-17 17:00:25.269002 defining Ionophore Material <p>Hi, Can I know how we can define a material like Ionophore in COMSOL 5.3a. I'm using a valinomycin Ionophore in my topic. And i want to know the physics required for that. Thank you.</p> Thu, 17 Sep 2020 16:34:12 +0000 4.2020-09-17 16:34:12.269001 Mesh information <p>Hi! I'm having problems retrieving the mesh data, using LiveLink with Matlab. Once the mesh is created, I get the data by using the function [stats, data] = mphmeshstats(model). I must use the nodes, the elements topology and the boundary elements topology of my tetrahedral mesh to pass them as input to another functions. The vertex are obtained by simply doing vtx = data.vertex. As I understand, the elements topology are obtained by: H = data.elem{2}' + 1 (+1 beacuse of the zero indexing), but I'm not sure how to recreate the boundaries elements topology from the data structure. Any idea? Thanks!</p> Thu, 17 Sep 2020 16:23:21 +0000 4.2020-09-17 16:23:21.268992 The Problem: the maximum gain is bigger than the maximum directivity. <p>Hi,</p> <p>In the attached file which is a microstrip antenna model, the value of <strong>maxGaindB</strong> is bigger than that of <strong>maxDdB</strong>. I couldn't find the reason. Do you have any idea?</p> <p>Thanks.</p> Thu, 17 Sep 2020 16:07:40 +0000 4.2020-09-17 16:07:40.268991 Phase Change Material modeling <p>hello, i was using comsol V5.2a for simulating a phase change material inside a solid domain, and it showed a ((nearly)) constant temperature during melting and soldification. now i'm using COMSOL v5.5 with the same old model but it dosen't show that constant temperatue during melting nor soldification. can anyone suggust what modification should i do ? thanks in advance.</p> Thu, 17 Sep 2020 07:20:57 +0000 4.2020-09-17 07:20:57.268982 Distance Between the Model and PML <p>Hi,</p> <p>Is there any rule of thumb or minimum value for the distance in wavelength between perfect matched layer (PML) and the model for antenna simulations? I experienced that the size of spherical PML has a considerable effect on S11 values. But I couldn't find a criteria for it in the documents and the Internet.</p> <p>Thanks</p> Thu, 17 Sep 2020 06:02:39 +0000 4.2020-09-17 06:02:39.268971