Latest Discussions - COMSOL Forums https://www.comsol.com/forum/ Most recent forum discussions Sun, 20 Jan 2019 12:39:26 +0000 COMSOL Forum: Latest Discussions https://www.comsol.com/shared/images/logos/comsol_logo.gif https://www.comsol.com/forum/ Skin effect simulation in tinned/covered coil https://www.comsol.com/forum/thread/226041/skin-effect-simulation-in-tinned-covered-coil?last=2019-01-20T12:39:26Z <p>Dear Comsol Comunnity,</p> <p>I have been using Comsol at my University a few times so my experience in this software is only scientific and quite general. Now I have a problem which is quite complex. Here is the potential problem abstract. I want to simulate the skin effect in tinned coil or coil covered by other material like kanthal, lead, nickel and constantan. This is the air coil 20mm diameter with 14 turns with 4mm separation between them covered by around 100 um to 300um different material. It should have estimated inducted around 1 or 2uH (the exact value is doesn't matter for now). I want to do frequency sweeping from single MHz to tens of GHz for chosen material and its thickness. For example copper cover by tin 100umthickness -> frequency sweeping, same 150um, kanthal 100um then 150um etc etc. My goal is to chose the configuration where the surface current density norm (A/m) is highest. Thing is that I'm not sure how to cover the copper with other material. What I have done is STP file with example coil model I wanted to examine (attachment). I have add the boundaries for all of the coil excluding the boundries that I want to define as Coil input and output in Coil geometry analysis. My question are: 1. Whether my thinking is correct? 2. If yes (1) is this the only way to make the material coverage? 3. If my thinking is correct: a) Whether all of the boundaries which covers the copper should be defined in Coil explicit additionally or whether they should be defined as second coil and mutual inductance between them ? b) How to generate the Mesh for that kind of problem ? 4. Maybe there are special material library for that kind of problems ?</p> <p>Best regards, Krzysztof Szybinski</p> Sun, 20 Jan 2019 12:39:26 +0000 4.2019-01-20 12:39:26.226041 Seawater freezing https://www.comsol.com/forum/thread/226031/seawater-freezing?last=2019-01-20T10:06:12Z <p>Hello, I'm trying to model seawater freezing as new comsol user and i have few Q's How can salt added to water with specific concentration for a specific domain ? during freezing the seawater salt should be sperated from the ice growth, which is the most suitable module to use ?</p> <p>thank you,</p> Sun, 20 Jan 2019 10:06:12 +0000 4.2019-01-20 10:06:12.226031 Infinite Domain (Half-Space) and Anisotropic Conductive Sheet (Electromagnetic Frequency Domain) https://www.comsol.com/forum/thread/226022/infinite-domain-half-space-and-anisotropic-conductive-sheet-electromagnetic-freq?last=2019-01-20T06:29:10Z <p>Hi,</p> <p>I am trying to study a scenario of infinite domain half-space that is separated by infinite anisotropic conductive sheet. The excitation is coming from a dipole. My problem is in defining the anisotropic conductive sheet. Can you suggest what is the best method for implmenting this?</p> <p>A picture is available in this link <a href="http://imgur.com/a/XewUfea">image</a></p> <p>Thanks</p> Sun, 20 Jan 2019 06:29:10 +0000 4.2019-01-20 06:29:10.226022 Why solution is different when using 1 or 3 Pressure Acoustics interfaces? https://www.comsol.com/forum/thread/226012/why-solution-is-different-when-using-1-or-3-pressure-acoustics-interfaces?last=2019-01-20T02:51:44Z <p>Hello everyone!</p> <p>I'm working on a transient model consisting of one piezoelectric emitter transducer, one receiver and a cylindrical short sample. My first approach was to use one single <em>Pressure Acoustics, Transient</em> interface branch to obtain the acoustic pressure field of the entire model (emitter + sample + receiver). My second approach was to use 3 simultaneous <em>Pressure Acoustics, Transient</em> interface branches, one for each component, and connect them with appropriate Pressure and Impedance boundary conditions on the contact faces.</p> <p>In the end, both methods provided different solutions. The first method (denoted as 1-P in the attached images) gave me a lossless periodic signal and the second method (denoted as 3-P in the attached images) gave me a periodic signal that asymptotically goes to zero as if I had inserted losses, which I didn't. Why both methods provide different solutions?</p> Sun, 20 Jan 2019 02:51:44 +0000 4.2019-01-20 02:51:44.226012 Sweeping a material parameter https://www.comsol.com/forum/thread/226002/sweeping-a-material-parameter?last=2019-01-18T18:24:02Z <p>I am looking at how a pressure wave interacts with a porous material, and I just want to sweep the porosity of the material. I am unsure how to do this, any help would be greatly appreciated.</p> Fri, 18 Jan 2019 18:24:02 +0000 4.2019-01-18 18:24:02.226002 Dynamic response of a plate under impact loading https://www.comsol.com/forum/thread/225992/dynamic-response-of-a-plate-under-impact-loading?last=2019-01-18T16:39:21Z <p>Dear All,</p> <p>I want to simulate impact of a ball on a plate. I was wondering if anybody knows which module is the right tool to do so. Thanks.</p> Fri, 18 Jan 2019 15:34:01 +0000 4.2019-01-18 15:34:01.225992 From Rhino to COMSOL https://www.comsol.com/forum/thread/225991/from-rhino-to-comsol?last=2019-01-18T11:30:13Z <p>Hi everyone,</p> <p>I need your support. I created a 3D model in Rhinoceros, that I saved in .3dm format. How can I import this in Comsol? Is it possible?</p> <p>Thanking you in advance, Maria</p> Fri, 18 Jan 2019 11:30:13 +0000 4.2019-01-18 11:30:13.225991 Find resonance peak with parameter sweep in vibration mount https://www.comsol.com/forum/thread/225963/find-resonance-peak-with-parameter-sweep-in-vibration-mount?last=2019-01-18T01:35:18Z <p>I'm simulating vibration isolation mount, and I can get the transmissibility function by getting the value of acceleration of mass and base, and by dividing them. Then I can successfully get the graph of mass-spring-damper system. The mount is just simply designed as block with some thickness, and I want to get the value of resonance frequency by sweeping the thickness of mount. I firstly tried eigenfrequency study, but it just shows strange complex number eigenfrequency, whose real part is 10^-4 scale.</p> <p>The algorithm that I want to realize is this : I set thickness with some value, and get the frequency response, find resonance frequency. I sweep the thickness, then I can get the graph of thickness-resonance graph</p> <p>How can I do this algorithm in COMSOL? I feel really gratitude to your help in advance.</p> Fri, 18 Jan 2019 01:35:18 +0000 4.2019-01-18 01:35:18.225963 Moving mesh https://www.comsol.com/forum/thread/225962/moving-mesh?last=2019-01-18T01:20:36Z <p>Hi,</p> <p>I am trying to follow the 'induced voltage moving magnet" example, and I made my own simple 3D geometry. The stationary solution works fine but the time dependent one causes errors:</p> <p><em>Failed to find consistent initial values. Matrix has zero on diagonal. Last time step is not converged.</em></p> <p>Any idea what is causing this error?</p> Fri, 18 Jan 2019 01:20:36 +0000 4.2019-01-18 01:20:36.225962 How can I import position-dependent variables into Comsol matlab code using livelink? https://www.comsol.com/forum/thread/225942/how-can-i-import-position-dependent-variables-into-comsol-matlab-code-using-live?last=2019-01-17T21:02:34Z <p>I am using Comsol with Matlab livelink. Please, find my attached Matlab code and mph file. Directly in Comsol matlab code, I computed phi0 which gives the initial values of variable phi on each of the nodes (line 134-156). I used the mesh discretization of 40 by 80 which gives a total nodes of 41*81. And the code runs completely.</p> <p>Now, using the same discretization, I computed phi0 with another code (line 8-42), which I assigned to phi3 (line 46 and 47). I inputed phi3 as phi0 in Comsol (line 157). I have the coordinates of each nodes and their corresponding phi3. I used num2str in line 157 to assigned phi3 as phi0 which includes the x and y coordinates of each node and their corresponding phi0 (line 46) but the code gave error. I also used line 47 which contains only phi3, without x and y coordinates. But the code also gave error. It also gave error when I exported phi0 from Comsol and I tried to plug the exported phi0 back into Comsol. Error message: Error in multiphysics compilation. Syntax error in expression. Please, help me. How can I use calculated phi0 ( position-dependent variable) obtained from external source on each of the nodes of a Comsol model directly from the Matlab code generated from the model? I have the x and y coordinates of each of the nodes and the corresponding phi0.</p> Thu, 17 Jan 2019 21:02:34 +0000 4.2019-01-17 21:02:34.225942 Lumped Port to Excite Induction Coil https://www.comsol.com/forum/thread/225932/lumped-port-to-excite-induction-coil?last=2019-01-17T20:33:29Z <p>Hello All,</p> <p>I have read a number of posts on how to properly use the lumped port feature but I am still having issues...</p> <p>I have a closed spiral induction coil that I am trying to excite with 100 A of current (please see the attached picture). I am using a user defined lumped port (the green area in the attached picture) in a fashion similar to the Dipole Antenna tutorial where the height is 0.1" and the width is the circumeference of this circular section with the terminal type set to "Current" at 100 A. However, based on the explanation of lumped ports in the discussion below, I am not sure if I am properly implementing it:</p> <p>https://www.comsol.com/forum/thread/46515/lumped-ports-confusion-what-are-they-supposed-to-be</p> <p>It seems like if I put 100 A in to the settings field, 100 A is not what is truly being put through the coil but rather some sort of current density calculated from this initial value. Additionally, after running several simulations with 100 A specified, the heating is far beyond what I have witnessed experimentally and I believe it has something to do with my lack of understanding of the lumped port feature.</p> <p>Any help is appreciated. Thanks!</p> <p>Matt</p> Thu, 17 Jan 2019 20:33:29 +0000 4.2019-01-17 20:33:29.225932 Transfer data from one module to another https://www.comsol.com/forum/thread/225931/transfer-data-from-one-module-to-another?last=2019-01-17T16:28:36Z <p>How I can transfer data from AC/DC module to wave-optics module?</p> Thu, 17 Jan 2019 16:28:36 +0000 4.2019-01-17 16:28:36.225931 How to vary the evaluation number during continuation approach for solving Topology Optimization problem? https://www.comsol.com/forum/thread/225923/how-to-vary-the-evaluation-number-during-continuation-approach-for-solving-topol?last=2019-01-18T04:22:46Z <p>Dear Mr./Mrs.,</p> <p>The latest released example "Bracket — Topology Optimization" demonstrate how to implement the continuation approach in topology optimization problem, please refer to the following website: https://cn.comsol.com/model/bracket-topology-optimization-69891</p> <p>My question is: In this "Bracket" demo example, the evaluation number for each continuation step remain the same which was set to 50 in this example. Is it possible to vary the eval numb for different steps? For example, the maximum evaluation number is set to 30, 40, 50 and 60 for continuation step 1, 2, 3 and 4, respectively.</p> <p>Kindly regards, Hao</p> Thu, 17 Jan 2019 15:27:47 +0000 4.2019-01-17 15:27:47.225923 Reaction Force https://www.comsol.com/forum/thread/225901/reaction-force?last=2019-01-17T16:19:21Z <p>Hi there,</p> <p>I am setting a prescribed displacement on a rigid body. How can I get the reaction force of prescribed displacement on this rigid body?</p> <p>Thanks in advance, Ke Wu</p> Thu, 17 Jan 2019 10:38:23 +0000 4.2019-01-17 10:38:23.225901 How to increase a load in a physical time https://www.comsol.com/forum/thread/225851/how-to-increase-a-load-in-a-physical-time?last=2019-01-17T18:13:40Z <p>Hi everyone, I started to realize a preliminary breast computational model with COMSOL: first have to study the gravitational effect on it, by increasing the gravity progressively from zero at initial stage to g in a physical time of 60 s. How can I do this? How can I increase progressively this load in 60 s? Thank you a lot,</p> <p>Maria</p> Thu, 17 Jan 2019 08:37:21 +0000 4.2019-01-17 08:37:21.225851 COMSOL simulation of plane wave https://www.comsol.com/forum/thread/225833/comsol-simulation-of-plane-wave?last=2019-01-17T07:14:30Z <p>Hello! In the comsol pressure acoustic module, I can simulate the diffusion of sound waves, then I want to simulate the absorption of sound waves in pure media. What module should I use?</p> <p>Thank you!</p> Thu, 17 Jan 2019 07:14:30 +0000 4.2019-01-17 07:14:30.225833 How to limit the range of dependent variable? https://www.comsol.com/forum/thread/225823/how-to-limit-the-range-of-dependent-variable?last=2019-01-17T09:31:52Z <p>I want to solve the PDE in comsol in the special range for dependent variable. For example, the dependent variable,i.e., the concentration c is limited to c&lt;=0.2 in the PDE, how to do?</p> Thu, 17 Jan 2019 03:13:30 +0000 4.2019-01-17 03:13:30.225823 How to change the range of values in the legend bar? https://www.comsol.com/forum/thread/225822/how-to-change-the-range-of-values-in-the-legend-bar?last=2019-01-17T01:43:05Z <p>Hello world,</p> <p>I am looking for a method to change the range of values on the legend bar.</p> <p>I did simulations of a mebrane deflection under different loads and computed for the von mises stress (also see the attached image). Looking into the results, each of them are reporting different range of stress which is quite natural. However, I want to make a big figure in which I put all of the simulations results with only one legend bar (to compare them together).</p> <p>I would appreciate any kind of idea/solutions. Thanks!</p> <p>Kind regards, Amin</p> Thu, 17 Jan 2019 01:43:05 +0000 4.2019-01-17 01:43:05.225822 Time Dependent Analysis of A Spiral PCB Coil https://www.comsol.com/forum/thread/225812/time-dependent-analysis-of-a-spiral-pcb-coil?last=2019-01-16T23:35:33Z <p>Hello, I am trying to model the magnetic field around a PCB coil during a tone burst excitation. I have modeled the PCB coil and the model runs correctly with a stationary study including a parametric sweep node which sweeps over time. I have been unable to run the model with a time-dependent study so far. It returns zero for all time steps. I am uploading my model file here.</p> <p>Since my major is not related to this field, any help would be highly appreciated.</p> <p>Regards</p> Wed, 16 Jan 2019 23:35:33 +0000 4.2019-01-16 23:35:33.225812 Tesla coil in comsol https://www.comsol.com/forum/thread/225802/tesla-coil-in-comsol?last=2019-01-16T13:38:50Z <p>hello, please I'm investigating how to transmit electrical power in the form of radio frequency from one coil to another, something like the tesla coil. radioactive and noninductive coupling. can you help me? (multi-turn coil, Bifilar coils, etc.)</p> Wed, 16 Jan 2019 13:38:50 +0000 4.2019-01-16 13:38:50.225802