Latest Discussions - COMSOL Forums Most recent forum discussions Fri, 18 Jan 2019 18:24:02 +0000 COMSOL Forum: Latest Discussions 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 Reaction Force <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 <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 <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? <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? <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 <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 <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 using Prev operator <p>hello all,</p> <p>I am trying to create a condition were the solution of a present formula gets automatically added with the solution of the same formula from the previous time step. for this i used <em>Prev(exp,1)</em> operator but i am getting and error "Previous time step not stored". Any idea how to reslve this</p> <p>Thank you so much..:-)</p> <p>With regards Hari</p> Wed, 16 Jan 2019 11:47:29 +0000 4.2019-01-16 11:47:29.225771 Meshing techniques in comsol <p>I want to know if any there are any meshing techinques that can solve a complex domain consisting of extremely small and sensitive domain elements. (finer than extremely fine). I am using COMSOL Multiphysics with AC/DC module 5.3(a).</p> Wed, 16 Jan 2019 11:41:48 +0000 4.2019-01-16 11:41:48.225761 Can I use de Pipe Acoustics Module to study a pressure wave that came from explosion in a combustion motor <p>I want to study how a pressure wave travel a long a pipe. That pressure wave came from explosion in a combustion motor. I'm using the pipe acoustic module, but the results in my simulations were different of the results measured in real motor. So I'm in doubt if this pressure wave is a acoustic wave and if I can use the pipe acoustic module.</p> Wed, 16 Jan 2019 10:49:21 +0000 4.2019-01-16 10:49:21.225752 Heat source simulation <p>Hi, I'm a complete comsol newbie. I'm trying to run a simulation that seems to be quite simple yet somehow I keep getting errors upon computing (usually the error is "The Relative Residual (x) Is Greater Than The Relative Tolerance"). Basically I'm trying to get the temp on a simplified transformer model (which I'v imported from an .stp file if it matters), which consists of a ferrite core, copper windings and a surrounding block of air I've added, and calculate it based on known losses. I created a steady-state project with the heat transfer in solids physic. Each relevant component was assigned as a heat source with a total power of the given losses. I left all other settings as default. I also assigned each component with its material and added missing properties as instructed by the software. Your assistance would be highly appreciated as I keep feeling as if I'm missing some basic consepts, given the fact that I'm failing to do some things that seem quite trivial. I'm attaching my model here.</p> <p>Thank you</p> Wed, 16 Jan 2019 10:37:30 +0000 4.2019-01-16 10:37:30.225751