Latest Discussions - COMSOL Forums Most recent forum discussions Wed, 23 Jan 2019 10:58:11 +0000 COMSOL Forum: Latest Discussions LMSTAT - finding number of licences in use <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>Hi,</p> <p>I've recently tried the advice given in the linked article to find out how many licences are in use on our system but I get this:</p> <p>glnxa64]$ lmstat -c /usr/local/software/comsol/5.4/license/license.dat -a -bash: ./lmstat: /lib64/ bad ELF interpreter: No such file or directory</p> <p>The system is running Centos 7, and the licence file at this location contains the following text (serial number and server name changed!)</p> <h1>SN=aabbccdd</h1> <p>SERVER ANY 1718 USE_SERVER</p> <p>Grateful for any input!</p> <p>Thank you.</p> Wed, 23 Jan 2019 10:58:11 +0000 4.2019-01-23 10:58:11.226201 arrhythmia model <p>I have developed a 2d cardiac model of the heart.I need to simulate an arrhythmia case study. What are the points to be noted?</p> Tue, 22 Jan 2019 15:19:37 +0000 4.2019-01-22 15:19:37.226172 What is the model for solving surface tension in COMSOL? <p>What is the model for solving surface tension in COMSOL?</p> Tue, 22 Jan 2019 13:13:59 +0000 4.2019-01-22 13:13:59.226163 Modeling cloth <p>Hi there,</p> <p>I have a problem modelling a piece of cloth in COMSOL. The key feature of cloth is that <strong>it has no bending stiffness or out-of-plane shear stiffness</strong>. Could you tell me how to set the right material for the cloth?</p> <p>Thanks so much, Ke Wu</p> Mon, 21 Jan 2019 15:37:27 +0000 4.2019-01-21 15:37:27.226121 Viscoplastic Creep Test <p>Hello,</p> <p>I am new to COMSOL and I am trying to simulate a VISCOPLASTIC creep/relaxation test on a simple 2D rectangular block. I would like to either have a constant boundary load or prescribed displacement for sometime and then the load is removed. The required results are attached below. I don't have a problem with the BC. I need help in setting up the physics and material properties to get the type of results required.</p> <p>NOTE - Any material can be used.</p> Mon, 21 Jan 2019 15:36:33 +0000 4.2019-01-21 15:36:33.226112 Fixed constraints properties <p>Dear all, I am doing a modal analysis of an unstable rock block to study its eigenfrequencies. One face of the limestome block was attached to the vertical cliff and therefore I set on it the FIXED CONTRAINT. However, this boundary condition is conceptually wrong since the "rock bridges" have their own stiffness. I would like therefore to set a boundary condition which take into account the Young's and Poisson's modulus of the rock compartment.</p> <p>Thanks a lot for your help, Marco</p> Mon, 21 Jan 2019 14:39:34 +0000 4.2019-01-21 14:39:34.226111 Modelling of thin layer <p>Hi;</p> <p>I am studying on thermo-mechanical simulation in Comsol 5.4 (licensed version). But I have some difficulty related to thin layer meshing and assigning solid boundary conditions especially. To make a true simulation, I have started with basic blocks. For example; assuming that there are three domains. The thicknesses of these three domains are 0.4 mm , 20 um and 0.4 mm, respectively. The domain with 20 um thickness is an adhesive layer and this adhesive layer bonds the other two domains to each other. Actually; I want to analyze mechanical behaviour of thin adhesive layer under temperature variations. The thin domain is a kind of adhesive (photopolymer). My study is time dependent, physics is thermal stress (multiphysics).</p> <p>My questions are firstly related to thin layer meshing and solid boundary conditions. Do you suggest any method to mesh thin layer effectively? I have made free tetrahedral and after that refined thin layer. It is true?</p> <p>For solid boundary conditions: the two boundaries of thin layer are “thin elastic layer”. In the settings, I have calculated only total spring constant. And I have made the bottom boundaries of other two domains “fixed constraint” to fix on a surface. Is that true?</p> <p>My model is actually more complex as I said, but firstly I want to start with basic blocks.</p> <p>Regards,</p> Mon, 21 Jan 2019 14:23:34 +0000 4.2019-01-21 14:23:34.226101 contour problem <p>my probleme is with the contour ploting problem* there is no triangulate from the data set in tecplot 2018 as in the older version to make our problem so much difficult</p> Mon, 21 Jan 2019 08:56:59 +0000 4.2019-01-21 08:56:59.226071 Skin effect simulation in tinned/covered coil <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 Infinite Domain (Half-Space) and Anisotropic Conductive Sheet (Electromagnetic Frequency Domain) <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="">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? <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 <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 <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 <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 <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 <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? <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 <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></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 <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? <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:</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