Latest Discussions - COMSOL Forums Most recent forum discussions Mon, 18 Feb 2019 01:17:43 +0000 COMSOL Forum: Latest Discussions How to draw Polygon spirals <p>This might sound like a dumb question, but I need to draw structures to simulate some microdevices but I don't know how to draw them exactly. Is there any equations for drawing spirals like these?</p> <p></p> <p>The parameters that are given to methe width (W) and spacing (S). How do I relate them to the side lengths? Is there any equations for determining the side lengths?</p> Mon, 18 Feb 2019 01:17:43 +0000 4.2019-02-18 01:17:43.227712 Using output data from a study step as an input parameter for a following step <p>Hi,</p> <p>I have a study where the first step is an Eigenfrequency analysis and the second step is a time dependent structural analysis with a sinusoidal force who’s frequency is the lowest Eigenfrequency evaluated in the first step.</p> <p>I currently manually modify a global definition parameter to be the lowest eigenfrequency once the modal analysis has completed. That works fine, but I now want to do a batch sweep of the study, so need some automated mechanism to set a parameter to the lowest eigenfrequecy from step 1.</p> <p>Can I refer to the eigenfrequency results data structure in the global definition parameters ? If so, it is not obvious to me how to get any visibility of the names of variables in the modal data set.</p> <p>Many thanks for any help.</p> Sun, 17 Feb 2019 23:28:27 +0000 4.2019-02-17 23:28:27.227702 Computing multiple Surface integrals and collecting the data <p>I'm attempting to compute the shape factor for a single sphere between two walls. I've managed to get a value which looks decent. I am, however, attempting to calculate this value with many different values of a certain parameter and would like to avoid manually inputting a different value each time. Could I make use of something like a parametric sweep to do this?</p> Sun, 17 Feb 2019 17:49:05 +0000 4.2019-02-17 17:49:05.227692 Connecting Beam Element and Solid Element <p>Hi,</p> <p>I am trying to simulate four point bending load test on a beam. I modelled reinforcement as beam element instead of truss and concrete as solid elements. Can anyone suggest me how to define connection between beam and solid element.</p> Sun, 17 Feb 2019 05:25:08 +0000 4.2019-02-17 05:25:08.227681 MF homogeneity <p>How i can calculate the homogeneity of a magnetic field?</p> Sat, 16 Feb 2019 21:09:01 +0000 4.2019-02-16 21:09:01.227671 Element order of Gauss point data? How many integration point? <p>Dear all,</p> <p>I am going to use the Gauss point data to define a material properties. I am confused by the element order of the Gauss point data, say 0, 2, 4,6,8 ,10.... Does these number mean the integration point within an element? If not, how can I know the number of integration points?</p> <p>Another question is what principles I should follow to select the element order. Now, my PDE is discretized by linear shape function. So, which element order for the Gauss point should I select to define the material properties?</p> <p>Thank you so much for your help.</p> Sat, 16 Feb 2019 14:11:00 +0000 4.2019-02-16 14:11:00.227662 A very easy question?How can I control control the duration of the heat source? <p>I want to sim the thermal wave ndt progress, and i need the heatresource just continue 30s,but i dont know how to setup, hope you may help, thanks a lot</p> Sat, 16 Feb 2019 08:03:21 +0000 4.2019-02-16 08:03:21.227653 Inquiry of Module in COMSOL 5.4 <p>Hello</p> <p>I would like to model flow and heat transfer of nanofluid through a microchannel for a nanofluid concentration of 1-5%. I would like to calculate different forces like, drag, lift, brownian, thermophoresis etc.</p> <p>Could you suggest what module should I purchase?</p> Fri, 15 Feb 2019 17:38:57 +0000 4.2019-02-15 17:38:57.227641 Initial perturbation of displacement field <p>Hello, I try to solve a wrinkling problem of a membrane and i would like to provide initial random perturbation of displacement field. What is the proper way of defining my own initial solution?</p> <p>Thank you,</p> <p>Petr</p> Fri, 15 Feb 2019 14:12:09 +0000 4.2019-02-15 14:12:09.227631 How to define a prescribed initial guess for a topology optimization problem? <p>Dear Mr./Miss.,</p> <p>In topology optimization, different initial guess may result in different final topologies. In COMSOL “topology optimization node”, if initial value of the design variable theta==1, which means at the starting point, the value of theta within the entire design domain remains the same.</p> <p>My enquiry: Is it possible to start the optimization with a prescribed initial design?</p> <p>For instance, in fluid topology optimization problem, instead of being initiated with a uniform theta==1 (fluid), how could I use a traditional parallel channel as an initial guess? The parallel channel layout can be accessed in the attached figure, please kindly check the attachment.</p> <p>Best regards, Hao LI</p> Fri, 15 Feb 2019 08:22:09 +0000 4.2019-02-15 08:22:09.227613 Acoustics Perfectly Matched Layer <p>I am trying to use the acoustics module with the perfectly matched layers to absorb any signal interacting with the boundary. What I want is analagous to plane wave radiation, but I want to use the perfectly matched layers since I need to later impliment the poroelastic waves module. It seems like the perfectly matched layers is being overidden by sound hard wall boundary, and I'm not sure how to change that. Any help would be greatly apprciated.</p> Thu, 14 Feb 2019 21:26:24 +0000 4.2019-02-14 21:26:24.227602 Dipole Antenna Impedance and Far Field Basics <p>I am working with the App Library Dipole Antenna model. I am trying to understand Lumped Port Input Impedance and resulting far field gain of the antenna.</p> <p>Question 1: I understand the the Results>Derived Values>Global Evaluation>emw.Zport_1 gives the impedance of the port as it is influenced by the structure of the antenna. For me this number is (Zport = 120.21+28.489i). If I want to MATCH this impedance with the feedline how do I do it? By changing Lumped Port1>Characteristic impedance to Zref = 120 Ohm?</p> <p>Question 2: When I do change Zref to 120 Ohm my S11 drops, indicating better impedance matching. However, I am struggling to see the resuling gain in the far field when using emw.gaindBEfar or emw.EIRPdB. Why is this? I suspect I am using the far field calculations incorrectly.</p> <p>Question 3: Given the above confusion, is there a good functional reference for the various Far Field antenna calculations available within COMSOL?</p> <p>Thank you so much!</p> Thu, 14 Feb 2019 18:32:40 +0000 4.2019-02-14 18:32:40.227592 Modeling an ion-exchange packed-bed reactor <p>Hello Everyone!</p> <p>I want to model an ion-exchange packed bed reactor. I would like to know which physics modules I should use. I need to model a packed bed tubular reactor in which the bed contains an ion-exchange resin. The material that is entering the reactor contains the ion that will be exchanged by the one in the resin, so the material at the outlet of the reactor we will have the ion that was originally in the resin.</p> <p>I will really appreciate your help.</p> Thu, 14 Feb 2019 18:20:37 +0000 4.2019-02-14 18:20:37.227582 How to calculate the average contact pressure of the actual contact area? <p>Hello,</p> <p>Im simulating currently contact pressure. For that i want to know the average contact pressure for every time step. I know that you can calculate the surface average, but my contact area is much smaller than the boundary surface. So is there a way to calculate the average contact pressure for the actual contact area?</p> <p>thanks in advance.</p> <p>Greetings, Kant</p> Thu, 14 Feb 2019 13:33:19 +0000 4.2019-02-14 13:33:19.227581 Legends position <p>How can I change the legends position, I want to place it above the cross section view horizontally. <img src="http://" alt="" /></p> Thu, 14 Feb 2019 12:39:13 +0000 4.2019-02-14 12:39:13.227571 Magnetic anisotropy <p>Hi,</p> <p>I have a three phase induction motor model in comsol and for the measurements, we are energizing the rotor and the stator does not have any winding. This is just the background knowledge of my model.</p> <p>Does anybody know how to model magnetic anisotropy in induction machine in comsol? I know from the Comsol software that relative permeability can be defined as an anisotropic property. But, is it possible to fix the stator and rotate the rotor at an angle with respect to the stator and in this way maybe magnetic anisotropy can be incorporated into the model?</p> <p>Regards, Hassan</p> Thu, 14 Feb 2019 10:17:01 +0000 4.2019-02-14 10:17:01.227561 Set export window using java <p>Hi,</p> <p>I'm using the java API to build my 2Dmodel and I made a plot which has a high height-to-width ratio. When I try to create an animation using the java export function, I get a lot of white-space above and below the model since it fits the plot in the width direction. In the GUI this would be solved by resizing the plot window and simply exporting again. I can't find a java command to do this automatically.</p> <p>I would like to have some sort of java command which allows me to set an export window.</p> <p>(P.S. I am using Comsol for Linux so my only options are .gif and flash (.swf) and I'm not a big fan of .swf since I can't get it to work in my presentation.)</p> <p>Any help would be very much appreciated,</p> <p>With kind regards</p> Thu, 14 Feb 2019 08:36:20 +0000 4.2019-02-14 08:36:20.227551 How to simulate surface roughness in CFD simulation? <p>Dear Mr./Miss.,</p> <p>We manufactured a liquid cooled heat sink by 3DP, and we intend to experimentally and numerically study the thermal and flow performances of the heat sink. The problem is that the roughness of cooling channel surface is not perfectly smooth due to the uncertainty during 3DP process. Therefore, is it possible to use any boundary condition setup to simulate such kind of rough surface in CFD simulation?</p> <p>Kind regards, Hao LI</p> Thu, 14 Feb 2019 08:30:40 +0000 4.2019-02-14 08:30:40.227543 Making contour plot from a 2D geometry <p>Hello, I am modeling transport of diluted species in a 2D circle geometry, time dependent study. I want make a contour plot with Time on y-axis and arc length on x-axis, with colors representing different concentrations. I would appreciate any help on how to make this plot</p> <p>Thanks Claire</p> Thu, 14 Feb 2019 05:48:52 +0000 4.2019-02-14 05:48:52.227542 Problem with 'Remesh Deformed Configuration' <p>Hello all,</p> <p>I am tring to study the Optical mode shape using 'Electromagnetic Waves' with a deformed mechanical geometry. This geometry is the mode shape of a mechanical mode.</p> <p>First, I got the mode shape from 'Solid Mechanics - Study: Eigenfrequenices'. Then I try to use 'Remesh Deformed Configuration' to build a new mesh for optical mode analysis. However, there seems to be nothing happened in the mesh. Why?</p> <p>BTW: I have checked 'Include geometric nonlinearity'.</p> <p>Thanks for your reply.</p> Thu, 14 Feb 2019 05:43:05 +0000 4.2019-02-14 05:43:05.227533