Latest Discussions - COMSOL Forums Most recent forum discussions Tue, 07 Feb 2023 10:53:53 +0000 COMSOL Forum: Latest Discussions Graphene Oxide Material in COMSOL <p>I want to model a graphene oxide nanoparticle. However, graphene oxide is not available in material library. How to define graphene oxide material?</p> Tue, 07 Feb 2023 10:53:53 +0000 4.2023-02-07 10:53:53.319301 COMSOL crashes suddenly <p>Hi, I am running an RF simulation with ~8M elements on my desktop machine (16-core CPU and 64 GB RAM). After about 10 minutes COMSOL crashes and it closes suddenly, but when I run the same simulation on my laptop, it works properly. I tried to change to DirecX9 from OpenGl but it did not work. I would be grateful if anyone could help me with it.</p> <p>Thanks</p> Mon, 06 Feb 2023 18:06:01 +0000 4.2023-02-06 18:06:01.319292 Time-Dependent Temperature Piecewise Function Providing Unusual Result <p>Hello COMSOL community,</p> <p>I am attempting to model a time-dependent temperature boundary condition in COMSOL. For half the day, the temperature at this boundary is at a constant 280K, while for the other half of the day, the temperature is at a constant 22.5K.</p> <p>To test the validity of the piecewise function, I first created a piecewise function from t = 1h to t =12h in which the temperature was set at 280K, and then inputted this piecewise function as the boundary temperature. In other words, the piecewise function puts out a constant temperature value of 280K for hours 1 through 12. I then ran the simulation for 12 hours. To compare results, I then inputted "280K" as my boundary temperature value in place of the piecewise function.</p> <p>However, I obtained two different results, which shouldn't occur. Can anyone shed some light on what is occurring? Thank you.</p> Mon, 06 Feb 2023 17:15:22 +0000 4.2023-02-06 17:15:22.319282 installation problem <p>Hello.. I am unable to install the comsol multiphysic and it's showing for me "No connection could be made because the target machine actively refused it". Can you please tell me how to install the software properly.</p> Mon, 06 Feb 2023 15:47:34 +0000 4.2023-02-06 15:47:34.319271 Reading Volumetric Velocity at probe <p>Hello,</p> <p>My name is Bhavesh. I have difficult to read volumetric velocity at boundary probe in thermoviscous module. I am using <strong><em>ta.v_tz</em></strong> [m3sec-1] this expression for that and it is showing me it is unknown variable. why is it so? Can anybody help me with that?</p> <p>Thanks in advance.</p> Mon, 06 Feb 2023 11:20:12 +0000 4.2023-02-06 11:20:12.319261 Monitoring multiple convergence plots (or probes) in cluster sweep (distribute parametric sweep) <p>Hello, I'm COMSOL newbie working on cluster computing.</p> <p>I'm using distributed parametric sweep mode, in which each server node solves a single problem (ex. Node 1 - Inlet fluid velocity 1m/s, Node 2 - Inlet fluid velocity 2m/s etc...)</p> <p>In distributed parametric sweep mode, (1) I want to monitor multiple convergence plots since multiple problems are solving simultaneously. But I can only monitor a single convergence plot... Please give me an advice.</p> <p>(2) How can I monitor multiple probe plots (which is Probe parameter - Iteration number plots)? I can only monitor accumulated probe table, which is the final converged value. But I want to check the probe value trend with respect to iteration number.</p> <p>Thank you very much!!! Every comment is my energy please help me!</p> Mon, 06 Feb 2023 02:34:02 +0000 4.2023-02-06 02:34:02.319251 Bolt pretension unit not matching to bolt force unit. <p>All unit : Gravitaitoal IPS (on gloabl parameter) Bolt pretension : 1880 lbf Global evaluation, Bolt force : 422.64 lbf I expected that Bolt pretension and bolt force values have to be identical. But then, I changed Bolt force unit on globla evaluation to N, It showed me 1880.0 N. I was very confused with the result. becaue lbf value is the same as N.</p> <p>So I tried SI unit All unit : SI Bolt pretension : 1880 N Global evaluation, Bolt force : 1880 N I got what I expected.</p> <p>Am I missing something on here? Would anyone please explain what is happening?</p> <p>Thank you</p> Sat, 04 Feb 2023 19:58:07 +0000 4.2023-02-04 19:58:07.319242 Simulation of inertial and gas forces on a moving piston <p>Hello, the aim of my simulation is to investigate stresses generated within a piston of a reciprocating engine, due to inertial force and gas pressure. I have already computed position and gas pressure as a funtion of time, got them in a separate .csv file. I would like to simulate the piston alone, with no other components. I found some examples, but I am not really sure how to get results I am looking for. Could you please advise how to proceed with this simultion? Thank you.</p> Sat, 04 Feb 2023 17:41:49 +0000 4.2023-02-04 17:41:49.319241 How to model dissolution and/or erosion of a tablet/pill? <p>Hi,</p> <p>I want to model the dissolution and/or erosion of a pill with COMSOL. I'm interested to know how fast the radius of the pill changes over time as the pill dissolves in to an aqueous domain, and how the concentration of the main constituent of the pill changes from the center of the pill to a distance away from the center. What modules, physics, boundary conditions, and mesh strategies do you recommend?</p> <p>Kind regards,</p> <p>Ro G.F.</p> Fri, 03 Feb 2023 21:31:34 +0000 4.2023-02-03 21:31:34.319232 Supercritical CO2 in Comsol <p>Hi, I am interested in modelling coupled flow and heat exchange with supercritical CO2 as one of the fluids. If the CO2 material in base COMSOL is set to or above the critical pressure and temperature of CO2, will it simulate supercritical properties? or would it be necessary to import in a specific supercritical CO2 module Thanks</p> Fri, 03 Feb 2023 03:07:12 +0000 4.2023-02-03 03:07:12.319212 Geometric toolbar editing positions of points in 5.6 <p>I have imported some axiosymmetric models from 3.5 that have a large unusual polygon shaped domain. In Geometry, Edit Object mode I see the points of the domain. I can move single points with the mouse in the shape, but I cannot specify their positions in sort of window.</p> <p>If I use Sketch mode, I can specify for a *new *point, R, Z. but not in on activated points Draw Mode.</p> <p>How to do this?</p> <p>Dr. Cohen</p> Fri, 03 Feb 2023 00:51:54 +0000 4.2023-02-03 00:51:54.319202 Failed to find consistant initial values <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>[start here] The model Im working on has Turbulent SST, Moisture transport in the air and Heat transfer in moist air as physics, and Moisture flow, heat and moisture and NITF as multiphysics couplings. Problem is when I run time dependent, one way with Initialization NIFT, if the time range is (0,0.1,1)s it gives me a result. But when I run the same model for the range of (0,0.1,1)h it says failed to find consistent initial values. I need the study to be done for (9,30[min],16)h. Can someone give me any advice?</p> Thu, 02 Feb 2023 09:37:32 +0000 4.2023-02-02 09:37:32.319201 Hexahedral Mesh <p>Hello,</p> <p>I wish to get hexahedral elements from COMSOL to import it into another software. I try to save data as .txt file. Altghough I created hexahedral meshs (atacched file), in the text file, I got tetrahedra mesh with 4 number per line! How can I fix that?</p> Thu, 02 Feb 2023 00:24:17 +0000 4.2023-02-02 00:24:17.319193 Part does not take stress. <p>Hello</p> <p>Part 1 does not show on my result. the only stress I can see is from bolts and bolt contact area. My expectation was to see stress from part 1 as well as part 3.</p> <p>I have no clue about why I don't see any stress from part 1 and 3. Would anyone please help me with this?</p> <p>Thank you</p> Wed, 01 Feb 2023 20:10:36 +0000 4.2023-02-01 20:10:36.319192 How to define TE and TM mode for 3D simulation? <p>I want to use the 3D model of wave optics module to simulate a periodic structure. To excite my structure in my simulation, I intend to use both TE and TM polarization. I am using periodic port; could you please tell me how to define the TE and TM modes specifically?</p> <p>I have one more question about rectangular ports. I understand how to define TE and TM modes while using rectangular port, but can we use rectangular ports for Periodic Structure?</p> Wed, 01 Feb 2023 13:21:32 +0000 4.2023-02-01 13:21:32.319181 Impedance spectroscopy of two electrodes in medium with frequency-dependent conductivity and permittivity <p>Hello,</p> <p>I have created parameters and tried (in the material water,liquid) to replace the preset electrical conductivity and electrical permittivity with formulas to make them frequency dependent (because i want to simulate NaCl solution). This does not seem to have worked well, is there any other way in the program to account for the frequency dependence of the medium?</p> <p>I am currently using the electric currents setting but it is not giving me the results I want. I had hoped that the electroanalysis would give better results but I can't find a way to display the impedance between the two electrodes. I cannot use "Electrode surface" because my electrodes are in the medium. What settings do I need to make to get an impedance spectroscopy?</p> Tue, 31 Jan 2023 13:26:52 +0000 4.2023-01-31 13:26:52.319161 simulating the Multi-Mode Interference device (MMI) <p>Dear All</p> <p>I am simulating the power splitter based on Multi-Mode Interference with Grating (MMI), I have followed the existing geometry of the MMI device as shown in the attached photo, please find it.</p> <p>I have added the Wave Optic module to calculate the Electric field within the MMI stucture and the model has been solved without error. However, the result I got does not the same as the result published in the attached photo.</p> <p>Please note: I am attaching my model to this email. I have cleared the mesh to reduce the file size.</p> <p>What do you advise me to make the Electric field look like exactly the published paper, please?</p> <p>Best regards, Manal</p> Tue, 31 Jan 2023 12:07:18 +0000 4.2023-01-31 12:07:18.319151 using the Optimization Module <p>Hi everyone</p> <p>I am interested in using the optimization module. I have read its user manual and found the following points:</p> <ul> <li><p>You can use the control variables directly to parameterize any aspect of the physics that is controlled by an expression. This applies to material properties, boundary conditions, loads, and sources. However, control variables cannot be used directly in the geometry description. Instead, the model must be set up using a Deformed Geometry or Moving Mesh interface to control the shape of the geometry. Then use control variables to control the mesh movement, effectively parameterizing the geometry.</p></li> <li><p>The optimization module can be used for estimating modeling errors caused by uncertainties in material properties or for predicting the effect of a geometrical change.</p></li> </ul> <p>Does this mean that the optimization module can be used for optimization of actual material properties of the material itself (not only material parameters), please?</p> <p>Best regards, Manal</p> Tue, 31 Jan 2023 11:24:57 +0000 4.2023-01-31 11:24:57.319141 operations involving derived values <p>Hello, In the Results node, I would like to evaluate expressions and formulas involving derived values. For example, in a 2D problem, I need to divide a line averaged value (temperature, magnetic induction, it does not matter) obtained averaging on a select 1D element, by , for instance, a surface obtained by integration on a 2D (obviously) different element. I do not succeed to make simple operations (x,+,-,/) on derived values when they refer to different elements. Yes, I can do it later by hand but I would like Comsol to do these calculations for me, expecially in a parametric sweep. Thank you in advance.</p> Tue, 31 Jan 2023 11:10:41 +0000 4.2023-01-31 11:10:41.319131 Expression, Function and how it must work correctly? <p>Dear Colleauges now I in the process of transfer from Ansys to Comsol and i have 20 years expirience for numerical simulations because now Comsol is really friendly and powerfull instrument.</p> <p>I see the big possibilities for using Expression and Function for flexible define BC, matherial properties and etc, but with my huge expirience i have strange problem for my works with Espression in the Comsol. For example i want to define Piecewise function for radiative emisivity BC for walls, and i define hrad function with argument T is 0.1&#42;sigma_const&#42;(T^4 - 293^4) and interval for T. But Comsol not calculated the part of expression "-293^4" and results the same for "-293[K]^4" and etc, for example 0.1&#42;sigma_const*(T^4)- 0.1&#42;sigma_const&#42;(293^4). The plot graph for this function calculated only for T argement and absolutely ignored all other. Where i can see the principles (algorithm) for correct defining of expresions? Please help me. As well, becasue Expression field absolutely don't has contects help (For example Ansys CFX preprocessor has a prefect help for all variables and etc in the field for formula), I'm as a user not understand what i may to do in the Expression field. The help of Comsol in laptop version is too small and i want to find the all list of operations, variables and etc (include from results solutions) which i can to use in the expression field. Please help me. Give me please the links to webinars,papers and other Comsol web helps, where i can see it clear.</p> <p>My big respect for Comsol team, Evgeny</p> Tue, 31 Jan 2023 10:32:26 +0000 4.2023-01-31 10:32:26.319121