Latest Discussions - COMSOL Forums Most recent forum discussions Sat, 25 Sep 2021 15:29:14 +0000 COMSOL Forum: Latest Discussions Discrete Fracture Network <p>How can I made a discrete fracture Network in 2-D in Comsol. Is there any module in 2-D like Discrete fracture network -3D.</p> Sat, 25 Sep 2021 15:29:14 +0000 4.2021-09-25 15:29:14.297231 Derivative of the dependent variable relative to the parameter <p>Hi! I need to calculate the derivative of the dependent variable (temperature) with respect to the material parameters in Comsol. Can I enter ready-made equations or are there maybe some built-in functions for solving this problem? I am asking for tips on how to do this.</p> Sat, 25 Sep 2021 15:04:34 +0000 4.2021-09-25 15:04:34.297221 accuracy of weak solutions <p>Finite elements give weak solutions, that is, the solutions to a PDE are only correct in its integral form. Is it possible that in comsol, the solution differs a lot from the analytic one locally while it's only accurate in its integral form (globally)?</p> Sat, 25 Sep 2021 15:53:05 +0000 4.2021-09-25 15:53:05.297213 Inductance and capacitance values. <p>Hi I have found out the Inductance and capacitance matrix for a transformer model(turn and disc type). My doubt is weather the values obtained are in per m/mm or in H and F respectively. Same doubt in case of coil resistance also.</p> Fri, 24 Sep 2021 18:35:06 +0000 4.2021-09-24 18:35:06.297211 Error in Interpolation Function <p>Hello All,</p> <p>I am currently using an interpolation function, defined using a .txt file, as an time-dependent inlet temperature profile for the 'Heat Transfer in Pipes' interface.</p> <p>The model successfully calls the function, however, there is a small error in what is called by the input function and what can be measured in the Results section, using a Point Evaluation at the inlet. The error is typically small, fluctuating around plus/minus 0.03 C, except at the beginning and end of the time range where it can reach values of close to plus/minus 0.2 C.</p> <p>If anyone knows what may be causing this discrepancy, or how to minimize it, that would be greatly appreciated.</p> <p>Thank you! Andrew</p> Fri, 24 Sep 2021 17:10:28 +0000 4.2021-09-24 17:10:28.297202 Remesh per step during auxiliary sweep <p>Hi,</p> <p>I'm trying to run a rather simple study where I apply a prescribed displacement to the top boundary of a rectangular geometry (stationary, solid mechanics, 2D).</p> <p>I'm applying the displacement in steps through an auxiliary sweep. Is it possible to remesh the geometry per step in the sweep? Just with the same number of mesh elements, so no refinements?</p> <p>/Karen</p> Fri, 24 Sep 2021 10:56:21 +0000 4.2021-09-24 10:56:21.297201 Irradiation studies <p>Dear all, I simulated by Geant4 a positron beam hitting two targets. By Geant4 I got the deposited energy in each voxel of the targets and now I must do a temperature study.</p> <p>I draw the targets by COMSOL as you can see in the attachment and I tried to follow this tutorial Unfortunately, the tutorial just explain how to set the enviroment themperature but nothing about the targets temperature!</p> <p>I want: 1.The best should be to set the deposited energy density at center of targets (the beam has a spotsize 300um, then the deposited energy is all distributed along the z axis) to get the temperature in all the targets then to study irradiation 2. If it isnt' possible to set the energy density, at least to set the target temperature (we have other software to calculate the temperature rising by deposited energy) to study irradiation between the two targets</p> Fri, 24 Sep 2021 07:43:49 +0000 4.2021-09-24 07:43:49.297191 [Urgent] studying Quasi-static structural behavior for 2D system <p>Dear experts, Kindly help me to resolve the problem <strong>Situation:</strong> I have a cell(r=20um, gold particle or any thing optically absorbing) that absorbs thermal energy placed at centre of square domain (side 1mm,water), supplied heat energy placed at the edge of square using laser. I want to study quasi-static thermal expansion of that cell using time dependent study for pulsed laser of 10ns.</p> <p><strong>Problem:</strong> 1. I was unable to select the boundary of cell for quasi-static study case .Also, if we use extra node of normal accln of cell boundary with inertial structural behaviour setting in solid node, we get noisy oscillating expansion. But, If we use quasistatic then no expansion is observed, but this is desired. 2. Kindly suggest me, how to meet the requirement of given situation for quasi-static case and corresponding study settings needed.</p> <p>Any suggestion is welcomed. However, It would be best if you could provide the model, that you tested for quasistatic expansion case.</p> <p>Thanks Best regards V. K.</p> Fri, 24 Sep 2021 07:11:29 +0000 4.2021-09-24 07:11:29.297181 How to set continuous boundary conditions <p>Hello, I am a beginner of COMSOL. I would like to ask when modeling an infinitely large space, only a limited space (such as a cube) is selected for simulation. Then how to set continuous boundary conditions at the boundary of the cube?And the physical parameter inside the cube equals the physical parameter outside the cube. Thanks in adavance.</p> Fri, 24 Sep 2021 01:37:13 +0000 4.2021-09-24 01:37:13.297173 Difference between gain and maxgain units <p>Hello everyone,</p> <p>While I was working with my antenna array simulation, I have realized that emw.gaindBEfar expression is represented in dBi when emw.maxGaindB expression is represented in dB.</p> <p>Could someone please explain me what the difference is between these two and why is emw.maxGaindB expression represented in only dB? Shouldn't it display in dBi also?</p> <p>Thanks.</p> <p>Best Regards.</p> <p>Gülden Günay Bulut</p> Thu, 23 Sep 2021 10:04:06 +0000 4.2021-09-23 10:04:06.297131 Exporting image sequence, zoom to extents don't work <p>Hi</p> <p>i did a sparametric sweep simulation on a variable number n of conuctor, now i would like to export all the generated plot with the image sequence tool. I do check on zoom extents, but this genereta all the images zommed on the largest number of conductor only. like this: <img src="" alt="" /></p> Thu, 23 Sep 2021 09:30:50 +0000 4.2021-09-23 09:30:50.297121 Modeling ultrasound levitation with the acoustic-structure-interaction multiphysics <p>Dear all,</p> <p>I believe the title gives away the question.</p> <p>I was wondering if it is possible to use the acoustic-structure interaction multiphsics coupling to model acoustic levitation of a single rigid (in terms of structural mechanics) object in an acoustic field?</p> <p>If not, could anyone provide details about the reasons?</p> <p>As always, any help you can provide is greatly appreciated.</p> <p>Best regards, André</p> Thu, 23 Sep 2021 08:49:57 +0000 4.2021-09-23 08:49:57.297101 Working with a non-converged stationary solution <p>I'm simulating a time-dependent nonlinear electromagnetics problem, where I use a stationary solution as my intial value. Since I updated to COMSOL 5.6, the stationary problem no longer converges. I used to have the relative tolerance at 1e-12, and have tried several different values of the relative tolerance, without the stationary solution converging. (I've also tried some different settings as well but summarizing all of those would be a minor essay.)</p> <p>I can see on the convergence plot that COMSOL always finds a solutions which is almost reaching the convergence criterias, for all relative tolerances I've tried that are &lt;1e-10, see attached file. Is there someway I can retrieve that almost-finished solution and use as initial value in my time-dependent simulation?</p> <p>Other ideas on why the stationary solver is not converging is also welcome.</p> Thu, 23 Sep 2021 06:36:42 +0000 4.2021-09-23 06:36:42.297091 Flow mapping from 3D component to 2D component <p>How to map a section of a flow model in three-dimensional components into a two-dimensional components for coupling with acoustic.</p> Thu, 23 Sep 2021 03:29:28 +0000 4.2021-09-23 03:29:28.297053 Can Darcy's law model pseudo-steady and transient state? <p>Hi,</p> <p>Assuming I have a 1 meter long core. Assume permeability is 1 Darcy, and porosity is 0.2. My injection velocity is about 2 cm/s. The outlet has same pressure as atmosphere pressure. So, actually, for water starts from inlet to outlet, it needs about 1/0.02 =50 s to reach the outlet. I want to see how the fluid velocity change between 0-50 s. But COMSOL only gives me one number of velocity. I assume this velocity is the steady state velocity. How can I get the changes of velocity before it reaches to breakthrough?</p> <p>Another question is, can COMSOL simulate the skin effect near the wellbore by using Darcy's law?</p> <p>It's most likely I will not get response from this forum. But whoever reads this post and have similar issue as me, we can try to discuss together.</p> <p>Thanks in advance.</p> Wed, 22 Sep 2021 21:45:16 +0000 4.2021-09-22 21:45:16.297042 Static and Dynamic Eccentricity Modeling on DC Motor <p>I am modeling a brushless DC slotless motor. I want to study the behavior of the electromagnetic flux density in the airgap as well the electromagnetic forces in the airgap, first without considering an eccentricity, and secondly while considering both static and dynamic ones. I am using 2D modling and the Rotating Machinery, Magnetic (rmm) physics. I have setup the correct geometry configuration (Form Assembly and the idensity pairs). Now, my question is, how can I model both static and dynamic eccentricty in the 2D model? What do I need to change in the Moving Mesh node? And do I need to change anything in the Force Calculation; (Torque Axis, or Torque Rotation Point)? Is it Possible to see the effect of the Dynamic Eccentricity in the 2D model? I believe the 2D component and the rmm physics allow for modeling depth, which resemble 2.5D, is that correct?</p> <p>Screenshot 1 --> The goemtry represent (a zoomed in) quarter of the motor, the yellow is stator, red is enclourse (air) and blue is rotor.</p> Wed, 22 Sep 2021 18:57:24 +0000 4.2021-09-22 18:57:24.297041 Importing a well deviation survey into a geometry. <p>Hi,</p> <p>i have been building generic models for some time now but am now tasked with integrating actual well deviation surveys into a geological model. The well deviation survey is a table with depth, inclination and azimuth for each well segment as well as X/Y coordinates for each segment (segment meaning 10 m intervals).</p> <p>If i wanted to integrate such a well as cylinder into the model, how would l do that?</p> Wed, 22 Sep 2021 09:05:01 +0000 4.2021-09-22 09:05:01.297031 Manual Frequency Transient Study <p>Dear All,</p> <p>I am doing an acoustics-model, where a smal sphere falls due to gravity in an acoustic field. I want to couple the acoustic radiation force to the "falling sphere". To do that, I want to have a solver sequence: motion of sphere (with moving mesh/deformed domain and some global odes), then compute the acoustic field in the frequency domain and use the time averaged acoustic radiation force for the motion of the sphere and do all this in a loop until the defined simulation time is reached.</p> <p>To my understanding this could use the frequency-transient solver. However, these are to my knowledge only availabe in electromagnetic heating physics.</p> <p>So, is there any way to set up a solver sequence manually? If so, is this described in any of the reference manuals? I couldn't find it.</p> <p>Best regards, André</p> Wed, 22 Sep 2021 07:07:37 +0000 4.2021-09-22 07:07:37.297021 Adding enthalpy of melting and boiling temperature <p>Hi, I wanna define a specific material for heat transfer, now I need to add the boiling temperature and enthalpy of melting as well but couldnt find any useful tips or videos. I appreciate any kind of info and tips. best regards</p> Tue, 21 Sep 2021 17:10:41 +0000 4.2021-09-21 17:10:41.296991 Post processing graph <p>Hi all, In the proble table graph, I'd like to plot for a particular time interval (say: 2000 to 2200 sec). But in the comsol, the 'Probe plot' plots all the output times. Could you please tell me how to do this?</p> <p>Ps: I've attached the probe plot for the entire simulation.</p> <p>Thanks in advance.</p> Tue, 21 Sep 2021 14:21:57 +0000 4.2021-09-21 14:21:57.296981