Latest Discussions - COMSOL Forums Most recent forum discussions Sun, 25 Aug 2019 03:22:46 +0000 COMSOL Forum: Latest Discussions The synthesis and decomposition of forces do not apply to dynamics in COMSOL? <p>Hi everyone.</p> <p>I have built three 2D plane strain models in COMSOL, each model was applied dynamic concentrated forces (1 MHz, last 10 microsecond), which are equivalent, at point A as shown in the figure named 'resultant decomposed force', and the results were the displacement of Rayleigh wave in the far field (at point B) on the free surface.</p> <p>Except for the forces are different, everything else for the three models are the same, the results should be the same since the forces are equivalent. However, the results are not the same, results of force 2 and 3 are the same, results of force 1 is different.</p> <p>The results for force 1, 2, 3 can be found in the attached pictures. I have no idea why the results are not the same. Does the synthesis and decomposition of forces not apply to dynamics?</p> <p>Would you please help me? Thank you a lot.</p> Sun, 25 Aug 2019 03:22:46 +0000 4.2019-08-25 03:22:46.241422 simulation consumes more time to complete <p>Hello</p> <p>I have found that the comsol modelling is consuming more time than usual. While I open the COMSOL it takes about 10 minutes to open a file. Similarly, to save a file too, it takes around 3-4 minutes. Some simulations which is expected to finish faster is taking about 10 hours.</p> <p>What are the possibilities that cause this trouble? Any recommendations or trouble shooting mehods to suggest?</p> <p>Thanks in advance</p> Sun, 25 Aug 2019 03:20:13 +0000 4.2019-08-25 03:20:13.241412 Composite resin <p>how to add resin in layerd composite analysis ??</p> Sat, 24 Aug 2019 04:38:24 +0000 4.2019-08-24 04:38:24.241411 COMSOL linked with parameter estimation and uncertainty software PEST <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>I would like to draw the attention of anyone who comes across the archived thread above to a software package that links COMSOL with PEST using the java interface.</p> <p>The paper: <a href=""></a></p> <p>The software: <a href=""></a></p> Fri, 23 Aug 2019 14:40:30 +0000 4.2019-08-23 14:40:30.241401 Material>Property Group>Local Properties <p>Hi all,</p> <p>I want to parameterize my material definition. The concept of "Local Properties" seems to be a nice concept. But whatever I define in the "Local Properties" table I cannot use to compute an output property (error message "Undefined variable").</p> <p>Can you provide me with a small working example for "Local Properties"?</p> <p>Thanks in advance.</p> <p>Best regardss</p> <p>Jens</p> Fri, 23 Aug 2019 06:58:24 +0000 4.2019-08-23 06:58:24.241361 [ERROR] Computed plastic multiplier is negative - Bending of shape memory alloy wires <p>Hello,</p> <p>I've a shape memory alloy wire, Flexinol, trained to bend upon heating. I'm trying to model this behavior in COMSOL Multiphysics 5.4 using the shape memory alloy material model of the nonlinear structural mechanics module in Structural mechanics physics. I'm doing a stationary study with custom mesh by having a transverse point load acting at the center. The wire is point constrained with fixed constraint and prescribed displacement at the end points. Such that one end is fixed and other end can move freely along an axis (y-axis). So that when the load is applied, the boundary surfaces can rotate about a point and one end can slide along y-axis thereby making a U shape. The load is applied and removed gradually with auxillary parameter sweep. Currently, I'm using the Lagoudas model with phase transformation properties, same as the one given in uniaxial loading of shape memory alloy tutorial. The model input temperature is user-defined so that T>T_Af (austenite finish temperature) in order to have superelastic behavior.</p> <p>The study works fine for small loads that causes stress to stay within the martensite start critical stress for that particular temperature thereby exhibiting elastic behaviour. The study FAILS when the material undergoes plastic deformation under loading or while it retrives the residual inelastic strain during unloading by throwing ERROR that computed plastic multiplier is negative.</p> <p>The model parameters works fine for uniaxial loading. Since the model has both tension and compression during bending, I'd like to know if the shape memory alloy model in Nonlinear structural material module is capable of calculating both tension and compression equation seperately for calculating the strain especially during phase transformation. I believe that Lagoudas model has two sets of equation for calculating strain in tension and compression.</p> <p>Thank you</p> <p>Regards, Ramprasad</p> Fri, 23 Aug 2019 05:03:37 +0000 4.2019-08-23 05:03:37.241352 Radius change in Phase Field <p>Hi, I am surrently working on a Three Phase simulation using the Phase Field interface in COMSOL. In the simulation, I observe a change in shape/profile of a phase. I want to plot this change in shape (r direction) vs the simulation time. How can i go about this?</p> <p>Any help is really appreciated. Thanks!</p> Fri, 23 Aug 2019 02:07:03 +0000 4.2019-08-23 02:07:03.241342 Reduced Order Modeling approach development request <p>Hello COMSOL community, I watched recently a webinar by Ansys developers about Reduced Order Modeling for creating a light weight model to be used for deplyoment of digital twin. I plea to the community to request similar functinoality/module in COSMOL.</p> <p></p> <p></p> Thu, 22 Aug 2019 17:11:26 +0000 4.2019-08-22 17:11:26.241302 Oscillations in streamer modelling at high voltage <p>Hi,</p> <p>I am trying to model a streamer discharge in 2D (axisymmetric configuration) between two parallel plane electrodes (inter lectrode distance = 1cm) at atmospheric pressure and high voltage (50kV) using Plasma Module. Here anode has voltage of 50 kV and cathode is grounded. A gaussian for electrons is placed initially at the anode (z=1cm). Wall BC is applied at anode (including migrative effects) and zero flux BC at both cathode and far boundary. (M+=>M) at both electrodes and (M-=>e+M) at anode are the surface reactions. However, oscillations start to appear right next to the anode as the streamer propagates from anode towards cathode as seen in the contour plot for electron density (files in attachment).</p> <p>Can somebody help me with finding the cause for these oscillations?</p> <p>Thanks,</p> <p>SJ</p> Thu, 22 Aug 2019 14:41:01 +0000 4.2019-08-22 14:41:01.241301 Image expored failed, anmation exporting <p>Dear all,</p> <p>I am simulating a 2D model of pm motor. I need to export the animation as a file. While I exported the animation, it showed the following error, which shows as the image upload 'error'.</p> <p>But, I have an assumption, in the Setting module (the upload image animation setting) , there is a browse button, I had change the path of the file, it still falied. Should I change the filename or other ways?</p> <p>How can I handle this problem? Hope you can share you idea with me.</p> <p>Best regards</p> <p>Joey</p> Thu, 22 Aug 2019 02:44:38 +0000 4.2019-08-22 02:44:38.241273 Getting quotient of 2 variables from two seperate studies <p>Hello, Im running two seperate studies and im trying to find the transmittance of the model. To do this i need to divide the total pressure of a SPECIFIED domain in each solution. Im able to easily extract the data i need using <strong>Derived Values -> Surface Integration</strong> then plugging in my pressure expression for the specified domain in each solution and finally exporting this data to microsoft excel and dividing column by column and plotting this. Is there a way to divide the data and plot it all in comsol 5.2? Any help would be greatly appreciated.</p> Thu, 22 Aug 2019 01:07:47 +0000 4.2019-08-22 01:07:47.241272 Switching boundary <p>Hello everyone...</p> <p>I am doing time dependent simulation on a falling film reactor. The study is basically on the mass transfer of gas into the liquid falling film. In my study the liquid film is flowing on the outerside of capillary at some constant flow rate and on the other hand the gas is stagnant. The liquid is constantly circulating within the reactor. The problem which I faced is: How I can coupled the outlet concentration to the inlet concentration. Actually I am simulating until the equilibrium pressure is obtained.</p> <p>Does anyone know how can I do this. Any help would be very appreciated !</p> <p>Thanks a lot.</p> <p>Haris Khan</p> Wed, 21 Aug 2019 22:34:42 +0000 4.2019-08-21 22:34:42.241271 Outlet to inlet switching <p>Hello everyone...</p> <p>I am doing time dependent simulation on a falling film reactor. The study is basically on the mass transfer of gas into the liquid falling film. In my study the liquid film is flowing on the outerside of capillary at some constant flow rate and on the other hand the gas is stagnant. The liquid is constantly circulating within the reactor. The problem which I faced is: <strong>How I can coupled the outlet concentration to the inlet concentration.</strong> Actually I am simulating until the equilibrium pressure is obtained.</p> <p>Does anyone know how can I do this. Any help would be very appreciated !</p> <p>Thanks a lot.</p> <p>Haris Khan</p> Wed, 21 Aug 2019 17:59:58 +0000 4.2019-08-21 17:59:58.241261 Convergence of COMSOL FSI problem for a splitter plate behind cylinder <p>Hello there, I am new to COMSOL. Whenever I try to run a FSI simulation of a splitter plate behind a cylinder, COMSOL somehow stops after certain number of iterations and in the convergence graph we can clearly see the deviation keeps on increasing only to stops with a message " <strong>Nonlinear solver did not converge. Maximum number of segregated iterations reached. Time : 0.98100000000000076 Last time step is not converged</strong>." and a warning "<strong>Inverted mesh element near coordinates (0.0500818, -0.0015782</strong>)."</p> <p>How can we ensure that the solution converges? What are the changes that we can do apart from mesh size changes and time stepping as I hace tried doing that with no substantial change in result. If someone could give some explanation of usage of the different solving techniques and their reflection on convergence then it would be very helpful.</p> <p>I am attaching the relevant screenshots.</p> <p>Thank You</p> Wed, 21 Aug 2019 15:48:51 +0000 4.2019-08-21 15:48:51.241251 An Issue on a quite simple model while doing Time Dependent Analysis by using LMS and MBD <p>Hello,</p> <p>This is a very simple model with only one block actually. But I have been struggling on this for quite a while.</p> <p>When I disabled the Damper C1, it can pass the test. However, with the damper actived it showed an Error:</p> <ul> <li>Feature: Time-Dependent Solver 1 (sol1/t1) Repeated error test failures. May have reached a singularity. Time : 0 Last time step is not converged.</li> </ul> <p>Can anyone help me on this? The two models with my idea is as attached. Thank you in advance.</p> Wed, 21 Aug 2019 15:07:44 +0000 4.2019-08-21 15:07:44.241241 Questions relating to object location and coordinate changes in Comsol. <p>Change the location of the 3D CAD file imported from import or Is there any way you can set the coordinates? Files drawn in Comsol can be co-ordinated, but I don't know how to import them. Please let me know.</p> Wed, 21 Aug 2019 14:26:56 +0000 4.2019-08-21 14:26:56.241233 Finding the value of X-axis (any variable) when Y-axis value is given? <p>I have the attached figure. This has been extracted from a simulation of COMSOL Multiphysics. I want to get the 27.6% of the maximum Maximum Electric field normal (shown in Y-axis) and as well as the corresponding Arc length value (shown in X-axis) at that point. It is manually possible to get both 27.6% of Maximum Electric field normal and the corresponding Arc length. But I want to do that automatically by the COMSOL software. Is it possible in COMSOL Multiphysics? Can anyone help me regarding this?</p> Wed, 21 Aug 2019 13:56:54 +0000 4.2019-08-21 13:56:54.241231 Radio absorption of honeycomb structure with frequency dependant materials <p>Dear all</p> <p>I have constructed a honeycomb structure of radio absorption in the range of 8.2-12.4 GHz, the permittivity and permeability of the material is frequency dependant, I have defined the frequency dependant material by interpolate function, how can I now sweep the frequency and study its absorption properties?</p> Wed, 21 Aug 2019 05:58:46 +0000 4.2019-08-21 05:58:46.241191 Using 2 variables from 2 different solutions to make a single plot. <p>Hello, I am running two simulations of a model that only slightly vary from one simulation to another, and i have a different <strong>study</strong> for each simulation. now I want to obtain the data for acosutic pressure from each simulation and use this data and plot them on one graph. i’ve tried using the join feature as well as manipulating variables/parameters and I keep getting errors. any help on this matter would be great thank you.</p> Tue, 20 Aug 2019 22:52:51 +0000 4.2019-08-20 22:52:51.241172 How to call an Application Method from another Application Method <p>I have been trying to create one main application method that instantiates and runs other Application methods that I have written. But everytime I try to instantiate another Application Method it says it can't be found.</p> <p><strong>How do I instantiate an instance of the class defined in an application method, and then call the <em>execute()</em> funciton?</strong></p> <p><strong>Example</strong>: I recorded and modified an application method called <em>FEAworkflow</em> that takes in a file name as a constructor argument, and then stores it as a member variable. The <em>execute()</em> function fot hat class reads that file, meshes it, and then applies a few loads, runs a simulation, and then stores the outputs in a CSV file.</p> <p>Now I created wrote another application method in which I have a for-loop that itterates over a list of all file-names, and calls <em>FEAworkflow</em> with the new file-name as an argument.</p> Tue, 20 Aug 2019 19:01:35 +0000 4.2019-08-20 19:01:35.241162