Latest Discussions - COMSOL Forums Most recent forum discussions Wed, 21 Apr 2021 00:13:41 +0000 COMSOL Forum: Latest Discussions Metal particles inside a Helmholtz coil <p>Hello,</p> <p>How can i simulate the behaviour of metal particles (Magnetite Fe3O4) inside of helmholtz coil magnetic field? - I want to analise the alignment of the particles with the magnetic field when i increase the power of the magnetic field until saturation. At the beggining the metal particles are randomly oriented, and they get aligned with the increase of the magnetic field.</p> <p>TankĀ“s for the help.</p> Wed, 21 Apr 2021 00:13:41 +0000 4.2021-04-21 00:13:41.287191 Geometry Constraints in COMSOL 5.6 <p>Hi all,</p> <p>I am not sure where I can add constraints when building my geometry in the sketch feature? All of the tutorials I have looked at have the constraints option automatically showing up however that is not the case for me. Does anyone know how I can enable these constraints? I have attached an image of what my geometry tab looks like for reference.</p> <p>Thanks</p> Tue, 20 Apr 2021 23:29:07 +0000 4.2021-04-20 23:29:07.287182 Writing scripts for COMSOL <p>Hi everyone! I'm trying to automate my work with COMSOL. That is, I have a file with a model and I need to perform a large number of simulations with different parameters. How can I optimize my work by writing a program? It is very inconvenient to manually change parameters, start calculations and wait until they are finished to enter new parameters...</p> <p>Thanks.</p> Tue, 20 Apr 2021 20:34:01 +0000 4.2021-04-20 20:34:01.287181 Force Factor - Loud Speaker <p>Hi, I am performing a loudspeaker simulation in which I have to calculate the force factor (BL) at each frequency. I have used the expression " -2<em>pi</em>N0<em>aveop1(mf.Br</em>r)" in global evaluation. But the results are complex values. Like this: 0.22937-0.18392i.</p> <p>How to interpret this? Please help.</p> <p>Regards, Mithun FEA Mechanical Engineer</p> Tue, 20 Apr 2021 19:38:50 +0000 4.2021-04-20 19:38:50.287172 Multiple phases on a single 1D plot <p>In the Electromagnetic Frequency Domain I know how to plot a field component, say emw.Ex, versus distance (say x) on a 1D plot for a specific phase angle theta by plotting real(emw.Ex * exp(i * theta)) or by using "Solution at phase". It's a single curve. I also know how to create multiple 1D plots under a 1D plot group and show several curves on the same axes, each with a different phase.</p> <p>But it's tedious to create all those 1D plots if I want to see a combination of, say, 360 different phases. Is there a way to plot this collection as multiple curves superimposed on the same 1D group, with a theta parameter varying for each?</p> <p>I tried putting in a range() in the "Solution at phase" setting, no luck.</p> <p>So the question is, how to get a Parametric Sweep "like" behavior versus phase angle so I can make the 1D plots of real(emw.Ex * exp(i * theta)) on the same axes for many different thetas, like I can for ordinary Parametric Sweep parameters.</p> <p>It's probably simple, I'm just not seeing it.</p> <p>Thanks</p> <p>-- C</p> Tue, 20 Apr 2021 19:05:46 +0000 4.2021-04-20 19:05:46.287162 Ultrasonic phased array transducer simulation using symmetry <p>Hi,</p> <p>I'm trying to simulate a 2-dimensional ultrasonic phased array transducer using piezoelectric materials. My goal is to see how much acoustic pressure I can generate in the target medium (water) by using the phased array to focus the ultrasonic waves.</p> <p>I'm having a problem with the symmetry boundaries. Because I'm focusing the ultrasonic waves directly below my phased array, there are two symmetry planes that bisect my model, so I only need to simulate a quarter of the geometry. I'm assuming that if I simulate the model this way, and assign the apropriate symmetry boundaries in the pressure acoustics module, I can build a 2x2 array which will produce the focusing effect of a 4x4 array in the water, for example. Or in other words, the symmetry boundary essentially copies the model accross the symmetry boundary and I can get the focusing effect of my phased array for a fourth of the computation. The problem is I get the same pressure field in the water whether or not I assign symmetry boundaries. So it's obviously not doing what I think it should be doing. What am I missing?</p> <p>Thanks,</p> <p>Jace</p> Tue, 20 Apr 2021 15:30:59 +0000 4.2021-04-20 15:30:59.287152 Defining a radiating surface of the flame that is non-locally coupled to the radiating gas volume <p>In the user story gallery, Multiphysics Analysis of a Burning Candle, they define a radiating surface of the expanding gas volume. I was wondering how to approach this in a similar modelling setup, how do I define a surface that is non-locally coupled to the radiating gas volume? Is it in Definitions-> Nonlocal couplings?</p> <p>Thanks</p> Tue, 20 Apr 2021 14:49:31 +0000 4.2021-04-20 14:49:31.287151 Arc length method <p>Hi! I am modelling a snap-back behavior in a structural mechanics problem. I am wondering how I can implement the arc length method in COMSOL. Is there any built-in functionality in COMSOL that I can use or is there any way to make COMSOL compute interactively with Matlab? Thanks!</p> <p>Regards, Tianyu</p> Tue, 20 Apr 2021 13:30:49 +0000 4.2021-04-20 13:30:49.287143 Octagonal Microwave Oven <p>I following the tutorial microwave oven from comsol. I try to built the octagonal shape for microwave oven. when I simulate, the heat generated in the potato doesn't change. Even though I have followed all the steps in the microwave oven tutorial, the only difference is the shape of the microwave oven. what is the problem? Please guide me with necessary step. Thank you very much.</p> Tue, 20 Apr 2021 11:57:32 +0000 4.2021-04-20 11:57:32.287141 Multiple 2D plots <p>Hello,</p> <p>I am currently doing a lab report and I am meant to plot something like the figure I attached. I dont know how to plot more than 1 together or how to set a limit from 55degC to 80degC.</p> <p>Kind regards.</p> Tue, 20 Apr 2021 11:43:14 +0000 4.2021-04-20 11:43:14.287131 What's the difference between mesh time (TIME) and time (t)? <p>As the topic shows, what's the difference between mesh time (TIME) and time (t)?</p> <p>Are they equals? Does the mesh time only emerge in the moving mesh?</p> Tue, 20 Apr 2021 11:32:29 +0000 4.2021-04-20 11:32:29.287123 Unexpected unit of input <p>Hi everyone, I am having a trouble while defining material properties. I want to define material properties as function of temp. So I have created function for that and wrote expression for this property in table. So I get error unkowon varibale Emod(please refer image 2). When I use expression Emod(t), the error is Unexpected unit of input.(please refer image 3).</p> <p>Can anybody help me?</p> <p>Regards, Rohit</p> Tue, 20 Apr 2021 11:32:05 +0000 4.2021-04-20 11:32:05.287121 Export data over entire surface and use as BC in a DIFFERENT model? <p>Basically the title. I want to record the velocity over the entire outlet of a pipe and use it as a BC for the inlet of a series of pipes in a different model.</p> <p>How I can export the data over the entire surface, import and make it a function in a separate model, then use that function as a BC? I am pretty sure this is possible but I do not know how to go about it.</p> Tue, 20 Apr 2021 01:10:02 +0000 4.2021-04-20 01:10:02.287092 How can I export results from file and re-use it in another file? <p>Hello,</p> <p>I have built a model and I have results.. I want to export these results from this model because I want to re-use it in a new model with the same geometry..</p> <p>How can I do that? I work in 3D?</p> <p>my goal results that I menton above are Electric Filed distribution.</p> Tue, 20 Apr 2021 00:06:02 +0000 4.2021-04-20 00:06:02.287082 Particle Diameter (dp) Constraints <p>When running a laminar flow and particle tracing for fluid flow through a needle, how would one add constraints to the particle size so that if a particle is a certain size, it won't pass through the needle?</p> Mon, 19 Apr 2021 23:36:28 +0000 4.2021-04-19 23:36:28.287072 Joule Heating Mandatory Temperature Boundary and Power Input <p>Good Afternoon,</p> <p>I have been building a model for a while now involving a heated wire inside a bulk material. I have run into two major issues with respect to the model and I cannot figure out if it is a result of missing material properties or the way the internal formulas are working.</p> <p>The first is that while I have a current running through my wire (which generates heat) I am interested in the heat dissipation through the bulk material. I <em>would like</em> to have equal parts natural convection boundaries and thermal insulation boundaries, however the model will not run without at least one contant temperature boundary. The model already recognizes what my initial temperatures are at every boundary, but the fact that the constant temperature boundary is required skews the data I am searching for with this model. What is causing this to happen and is there anything that can be done?</p> <p>Second, while I am currently using a terminal and ground pair of boundaries for my electrical input, the model will not resolve if I try to set my terminal with a power input. It runs fine with a voltage or current input, but refuses to cooperate with a value in Watts. Similar to the above question, is this a function of the software that I have overlooked, or is there a missing piece?</p> <p>Thanks again,</p> Mon, 19 Apr 2021 20:10:01 +0000 4.2021-04-19 20:10:01.287052 Parameter Sweep Undoes Geometry <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>I created a geomtry then simulated a few times using EM wave solver in the frequency sweep and the parametric sweep. Then I saved a new version of the file and made an edit to the geometry (added a filet on some edges). I tried to run the parametric sweep again and I get the error that the filet applies to no edges, which it certainly does. In fact, the parametric sweep is undoing my geometry. The variables I am sweeping should not affect the filet in question.</p> <p>Apparently someone has had this issue before with a parametric sweep undoing geometry. Has anyone else encountered this bug?</p> Mon, 19 Apr 2021 18:27:14 +0000 4.2021-04-19 18:27:14.287042 Joining different boundary layer meshes <p>Dear forum,</p> <p>I have a question concerning boundary layer meshing. I have two surfaces, each one with a boundary layer mesh, that progressively approach each other and come really close. Is there a way to collapse the boundary layers of these two surfaces? If not, when coming together, some parts of the "non-boundary" mesh remain in between the two boundary layer meshes, creating elements with a very low quality.</p> <p>Thank you for your support, Eduardo</p> Mon, 19 Apr 2021 17:32:50 +0000 4.2021-04-19 17:32:50.287041 Geometry "Contour" Lines On Final Images <p>I have finished running a CFD simulation and am exporting images of the results. On these images there are black lines that follow the contour of the model breaking it up into multiple sections. I want to get rid of these lines so that they are not showing up in the images that I export.</p> Mon, 19 Apr 2021 17:22:21 +0000 4.2021-04-19 17:22:21.287032 Particle movement -3 studies combination <p>Hi,</p> <p>I have combined 3 studies (one frequency domain and 2 time dependent studies) to investigate particle movement and trapping in a rectangular water channel. However, when I combine the 3 studies and using the feature "inlet-outlet" in the particle tracing for fluid flow module, I do not get any results in the respective plot. However, replacing the "inlet-outlet" with the "Release" feature does give me some results.</p> <p>Anyone knows why does this happen?</p> <p>Thank you.</p> Mon, 19 Apr 2021 14:19:46 +0000 4.2021-04-19 14:19:46.287021