Latest Discussions - COMSOL Forums Most recent forum discussions Sat, 23 Mar 2019 07:18:14 +0000 COMSOL Forum: Latest Discussions Limo Service Seattle Airport Washington 98002 <p>Hire <strong><a href="">Limo Service Seattle Airport</a></strong> to get quality limousines while exploring Seattle. You can select your favorite limousine from the moment you arrive at the Seattle Airport and we will make sure that you do not get disappointed by any of the services that we offer. You can hire us for wine tours, city tours, and cruise tours.</p> Sat, 23 Mar 2019 07:18:14 +0000 4.2019-03-23 07:18:14.230503 Segregated group 2 Failed to evaluate variable. - Variable: material.mur13 <p>I'm simulating magnetic field in a current carrying conductor. I have a 3D model and the following are the sub-modules included: Ampere's law Magnetic Insulation initial Values and External Current Density -> this is inmported from the Jouls Heating module.</p> <p>Just the jouls heating works fine. but i have issue when I include heating. I get the following error I get: Segregated group 2 Failed to evaluate variable. - Variable: material.mur13 - Geometry: 1 - Domain: 1 Failed to evaluate variable. - Variable: - Defined as: material.mur13 Failed to evaluate variable. - Variable: - Defined as: (((<em></em><em>(</em><em>(</em><em>(</em><em>(</em><em>(</em><em>(</em></p> <p>Failed to evaluate variable. - Variable: - Defined as: (((<em></em><em> Failed to evaluate expression. - Expression: d((</em>(<em>test(mod1.curlAx)</em>test(mod1.curlAy)<em>test(mod1.curlAz)))</em>(dvol),{test@1})</p> <p>any light on this will be much appericiated.</p> <p>Thank you!</p> Fri, 22 Mar 2019 15:56:29 +0000 4.2019-03-22 15:56:29.230501 Multiturn Coil Voltage Excitation: Problem with Coil Current Results <p>Hello everyone</p> <p>I'm trying to simulate a multiturn coil with an iron core, with a certain BH curve. Simulations run well, but for the same applied voltage, but different coil resistances, it always gives me the same current.</p> <p>I've tried to use the electrical circuit physics as in the E-Core Transformer example, but the results are the same.</p> <p>Can anyone help? How is the coil current calculated?</p> <p>Thanks in advance</p> Fri, 22 Mar 2019 11:21:47 +0000 4.2019-03-22 11:21:47.230471 Frequency Response for a clamped beam with many vibration absorbers. <p>Hello all,</p> <p>I have a thin plate modeled as 3D in solid mechanics module. On the top of this plate, I have places a mass-spring resonator (vibration absorber) (please see the attached figure) where I have modeled it in COMSOL using the lumped mechanical system. The helix spring is just for schematic where the actual 3D plate is shown in second figure. I coupled the two systems using the “External Source” from the lumped mechanical system and I exert the reactions from this external source to the solid 3D plate. The eigenfrequencies obtained from the eigenfrequency study matched perfectly with the in-house FE code. However, now I am trying to study frequency response to a harmonic force of an amplitude 1 while changing its frequency. Since I am applying the reaction forces from the external source of the lumped mechanical system to the 3D solid plate, how can I apply the harmonic force?</p> <p>I tried to add something like this:</p> <p>“-lms.E136_f2 + linper(1)”</p> <p>where “-lms.E136_f2” is the reaction force from the external source and “linper(1)” is my harmonic force but still I could not succeed. I will be really appreciated if I can find an answer.</p> <p>Thank you</p> <p>Abdullah</p> Thu, 21 Mar 2019 17:03:39 +0000 4.2019-03-21 17:03:39.230441 View Factor Computation (?!) <p>Has anyone succesfully computed view factors in a 2D geometry yet? I have tried to follow this blog:, but when trying this within a square cavity, I get either errors or zeros with the used function from the blog.</p> <p>Sharing your succesful model or steps for implementation would be appreciated a lot!</p> <p>Kind regards,</p> <p>Marvin</p> Thu, 21 Mar 2019 15:08:03 +0000 4.2019-03-21 15:08:03.230421 Regarding Rosette configuration <p>Hello all,</p> <pre><code> How to make strain mesurement using Rosette Configuration in Comsol, If known please let me know the procedure. </code></pre> Thu, 21 Mar 2019 14:21:17 +0000 4.2019-03-21 14:21:17.230411 Create inner surface by heat transfer <p>Dear Users,</p> <p>I need your help with a hopefully simple thing. I have two geometric bodies. The problem is that the surface between them dont exist so I can´t create a thin layer to simulate the heat transfer from them. Do you have an answer as to how it is possible to create an inner surface or just divide one surface into two parts?</p> <p>Thank you for your help!</p> Thu, 21 Mar 2019 11:16:34 +0000 4.2019-03-21 11:16:34.230401 Question regarding the calculation of area <p>Hi all,</p> <p>I have a 3D geometry and I was trying to get the boundary area of certain portion as an input for the further calculation.</p> <p>As suggested, there are two ways to get the area value: 1. Use measure under the geometry tag to get the boundary area. 2. Use intergration function for this boundary (such as expression intop(1)) to get the area.</p> <p>However, I found the values from these two method are a bit different. For example, for a circular plane, from integration method it got 9.7193E-12 [m^2], but from the measure methode it showed 1.0169E-11 [m^2]</p> <p>Why there is a difference? And which one should I trust?</p> <p>Thank you</p> Thu, 21 Mar 2019 09:26:19 +0000 4.2019-03-21 09:26:19.230392 Thermo Hydro Mechanical Modeling of Porous media <p>Dear Users, I am working on the thermo-hydro-mechanical model of porous media. At the time of solving I am getting the problem under time dependent study. For the time period (i.e., in s) (0, 0.1, 1) is converging promisingly. But that will not be happening during the time period from minutes onwards (i.e., from minutes to hr). I need solve this problem for the 1000 days with 1 day time gap (i.e., from 0, 1, 1000). Please help in this regard. It will be very helpful to me for continuing my research in the COMSOL Multiphysics for the coupling of various physics and their application in the Petroleum industry.</p> <p>Herewith I am attaching the file that I need to simulate.</p> <p>Thanking you Regards Dr. Manojkumar Gudala Institute PostDoc Fellow Indian Institute of Technology-Madras.</p> Thu, 21 Mar 2019 07:52:27 +0000 4.2019-03-21 07:52:27.230391 Modal assurance criterion (MAC) calculation <p>Does COMSOL calculate MAC of mode shapes obtained by FEA and mode shapes derived from experimental modal analysis (EMA)?</p> <p>Is there a command for MAC?</p> <p>Thank you!</p> Thu, 21 Mar 2019 05:08:06 +0000 4.2019-03-21 05:08:06.230373 Error: Failed to generate mesh for domain, Intersecting face elements <p>Hello,</p> <p>I am attempting to simulate the electric field of an imported CAD geometry (attached below) that includes a wire readout plane. My naive approach of generating a physics-defined mesh yields a long list of errors, due to supposed intersecting face elements and faces/edges that are shorter than the specified minimum element size. Most of the issues seem to occur where the small wires are attached to the board.</p> <p>After going through some of the blogs and tutorials, I have made some attempts to separate the edges (using the Edge operation) and define an "Extremely fine" mesh for the wires, but I still run into the same issues down the road when I mesh the "Remaining" domains.</p> <p>Could anybody please give a recipe for how to best tackle these issues? Is this better solved at the level of the CAD file or can I work within COMSOL?</p> <p>Many thanks for any advice you can offer, Michael</p> Wed, 20 Mar 2019 17:43:11 +0000 4.2019-03-20 17:43:11.230361 ECM (Electro Chemical Machining) <p>if any one is working ecm process in 3d geomerty. please help me because i am also working on ecm</p> Wed, 20 Mar 2019 16:35:20 +0000 4.2019-03-20 16:35:20.230351 pipe-flow-and-surface-radiation-interaction <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>Hello Aaron Valle</p> <p>hope you are well. I see your issue now. do you solve your problem?</p> <p>Peiravi M. M.</p> Wed, 20 Mar 2019 14:47:54 +0000 4.2019-03-20 14:47:54.230341 magnetic_gear_2d_geometry_sequence.mph. <p>Hi I'm looking for magnetic_gear_2d_geometry_sequence.mph file I couldn't find it in the application library I'm following this pdf to practice</p> <p>please</p> Wed, 20 Mar 2019 11:54:03 +0000 4.2019-03-20 11:54:03.230331 Some problems with parameters in module post-processing <p>Simulations in acoustic modules and solid mechanics modules have been done recently. I would like to ask some questions about the parameters in the post-processing of these two modules. There are some misunderstandings in this regard, I hope help and support.</p> <p>Firstly, in the acoustic frequency domain, the sound pressure and sound intensity distribution on the whole model can be obtained by applying the sound pressure signal, but in the acoustic time domain interface, there is only the spatiotemporal distribution of sound pressure except sound intensity distribution. Why and how to solve this problem (maybe use the relationship between sound pressure and sound intensity to seek sound strength, is this correct? ie I=actd.p_t^2 /rho/c).</p> <p>Secondly, in the solid mechanics module, the load direction is applied along the z-axis in the time domain (two-dimensional axisymmetric), and the calculation model is obtained to obtain the distribution of stress and strain. When extracting the velocity distribution at a certain point, there are several Different speeds which are not very misleading. I don't know what the specific meanings are, such as solid_vel and solid_utz. Assuming that solid_disp represents the total displacement, which one represents the slope of the displacement?</p> Wed, 20 Mar 2019 11:28:37 +0000 4.2019-03-20 11:28:37.230323 Using a stationary solution for time-dempendent problem <p>Hello,</p> <p>I have solved a stationary model for a flow field and temperature distribution.</p> <p>In the next step I want to solve a time-dependent problem for mass transport. In the inlet there's a change from substance A to substance B. The substances are completly the same in their physical properties, the only thing that changes is its name. It's for calculating a residence time distribution.</p> <p>So my question is: Is it possible to solve only for the time-dependent mass transport, without solving for the flow field and temperature, because they a same as in the stationary solution? I think this should reduce the amount of time required for the solution....</p> <p>Thanks in advance! Till</p> Wed, 20 Mar 2019 10:51:54 +0000 4.2019-03-20 10:51:54.230321 Singularities in the shape <p>Hi all</p> <p>I am modelling a single cell passing through a microfludic device in 2D set up using fluid-solid interaction interface(FSI).</p> <p>I found that when the velocity of the fluid is extremely high in the channel, in my model there are some singularities, however the deformed shape from the experiment should be a rather smooth "bullet" shape.</p> <p>I used the creeping flow to simulate shear flow. For the material model, I used neo-hookean incompressible material model. Besides, I also added three boundary loads except default interfacial force.</p> <p>I attached the figures from the experiment and simulationIs. Is there any way to smooth the fluid-solid interface or get rid of the singularities?</p> Wed, 20 Mar 2019 10:24:09 +0000 4.2019-03-20 10:24:09.230291 The Pressure Acoustics Impedance coupling <p>I saw the introduction that in Pressure acoustic RCL model, we can coupling to an Electric circuit model (More advanced circuit models may be entered manually in the User defined option or by coupling to an Electric Circuit model (this requires the AC/DC Module). ), but how to do it, if I create a complex RLC circuit by AC/DC Module?</p> Wed, 20 Mar 2019 09:19:51 +0000 4.2019-03-20 09:19:51.230273 Problems of error in the plasticity hardening model: Lamda non positive for plastic points <p>Hello every experts and comsol users, I made a simulation of laser beam welding and added a temperature dependent plasticity. When the generated stress reaches the initial yield stress, I get the error "Error in elPlastic element. - Detail: Lambda non positive for plastic point". I have seen the same problems of others, but the problems are not solved. I have tried to decrease the tolerance, the size of the meshes and the time step, but it does not work. Are there any problems in my temperature dependent yield curving in attachment? I simply did the same as the example: The temperature of simulation is about 1000K and the Laser worded in the first 1.5 seconds and the temperature gradients are very big.</p> <p>Any help would be appreciated. Thanks in advance.</p> Tue, 19 Mar 2019 17:15:07 +0000 4.2019-03-19 17:15:07.230241 Simulation of LED (InGaN heterostructure) <p>Hi</p> <p>i am working on Light emitting diodes, recently i checked that we can also simulates LEDs with the help of COMSOL, and also from COMSOL official website download example related to heterostructure LED, in this example firstly select the GaN then replace their name in text field InGaN or AlGaN, and then from properties only change single property i,e band gap. but according to literature when Indium is added in to gallium then multiple properties are changed due to strain(polarization) produced in material, not only band gap reduced but also tilt produce in quantum wells. I have a question how we can add strain factor or other properties to make releavent to literature?? also share published paper related to LEDs in which COMSOL software utilize.</p> <p>Thank you.</p> Tue, 19 Mar 2019 16:58:12 +0000 4.2019-03-19 16:58:12.230231