Latest Discussions - COMSOL Forums Most recent forum discussions Sun, 31 May 2020 21:37:02 +0000 COMSOL Forum: Latest Discussions Errors in simulating a glow discharge <p>Hello, Please can someone explain to me what this variable is?I don’t understand where the errors are</p> Sun, 31 May 2020 21:37:02 +0000 4.2020-05-31 21:37:02.260881 COMSOLE DOWNLOAD <p>Where can i get license for download comsole latest version?</p> Sun, 31 May 2020 14:12:19 +0000 4.2020-05-31 14:12:19.260871 Frequency domain vs wavelength domain <p>In the wave optics module (maybe also in the RF module), there is frequency domain study and wavelength domain study. Since there are simply relations between frequency and wavelength, what is the difference between these two study modes?</p> Sun, 31 May 2020 11:04:47 +0000 4.2020-05-31 11:04:47.260863 Internal error callback <p>Hi,</p> <p>Please let me know what is mean by internal error callback. Many times this error is coming for already solved models also.</p> <p>With Regards, Devaki</p> Sun, 31 May 2020 06:58:56 +0000 4.2020-05-31 06:58:56.260861 Cant install comsol <p>getting following error message. please help</p> Sun, 31 May 2020 06:32:06 +0000 4.2020-05-31 06:32:06.260851 Residence time in Free and Porous Media Flow <p>I am working on a project that requires me to find the residence time distribution of flow through a porous electrode. Due to the presence of other regions containing only fluid, I made the electrode geometry with the “Free and Porous Media Flow” module, and was able to find the fluid flow rates and streamlines. To find the RTD, I’ve tried to use both the “Transport of Dilute Species” and “Transport of Dilute Species in Porous Media” to mimic the effect of an injector used to find residence time, placing a probe at the outlet to monitor outflowing concentration.</p> <p>The problem I keep running into is that for some reason the concentrated region doesn’t move with the streamlines of the fp module. Increasing the time of the simulation or prescribing a higher flow rate does nothing, the concentrated region will not move and I can’t find the RTD. It just stays there at the opening. I’ve checked all the boundary conditions, made sure the velocity field is input from the fp module. I’m sure there’s something really simple I’m missing, but can’t find any tutorial combining these two modules.</p> <p>Can anyone help solve this problem, or suggest an easier way of finding the RTD using the flow field?</p> Sun, 31 May 2020 02:32:51 +0000 4.2020-05-31 02:32:51.260842 Large wavelength to feature size mismatch: Limitation of COMSOL simulations? <p>Is it possible to simulate the interaction of a ~ 3000 micron beam with an object with 1 micron smallest feature size (currently using Wave Optics module)?</p> <p>I read that there are limitations of conventional EM simulations when the mistmatch between the wavelength and feature size becomes very large. How can I determine when/if this is the case?</p> Sat, 30 May 2020 21:08:36 +0000 4.2020-05-30 21:08:36.260832 Particle size in Particle tracing module <p>Hello!</p> <p>I have a problem with the Particle Tracing in Fluid Flow (ver. 5.4). In particular, I want to set the diameters of the particles but changing the values (for example from 10^-9 m to 1m) I have the same situation. How I can solve this issue?</p> <p>Thank you so much in advance.</p> <p>Antonia</p> Sat, 30 May 2020 19:23:24 +0000 4.2020-05-30 19:23:24.260831 heterogeneous reaction - concentration of product decreasing <p>greetings,</p> <p>i am currently working on a model of the hydrogen evolution reaction using the interfaces transport of diluted species, chemistry, and surface reactions. The reaction mechanism i am modeling goes something like this</p> <p>H+ + e- + * => H*</p> <p>2H* => H2 + 2*</p> <p>where * denotes a surface site</p> <p>i would like to model the reaction with the initial condition that there is 1 monolayer of hydrogen adsorbed on the catalyst surface, so I have applied that condition in Surface Reactions.</p> <p>i am starting with 0 concentration of H2, and the rate of the second reaction is given by k[H*]^2, where k is a positive rate constant. i have applied a "surface reactions" condition in transport of diluted species to the boundary that I envision the catalyst is at.</p> <p>however, I have noticed that despite this reaction being the only "source/sink" of H2, the concentration of H2 initially increases near the boundary, then decreases. weirdly, when I change the initial condition so that initial hydrogen coverage is 0, H2 is increasing continually as expected.</p> <p>simplified version of the model attached below, any thoughts appreciated.</p> Sat, 30 May 2020 05:03:55 +0000 4.2020-05-30 05:03:55.260802 Modeling a Spiral Inductor Coil <p>Hello,</p> <p>Many of the blog posts refer to a toutorial on "Modeling a Spiral Inductor Coil", however, the link is not working,</p> <p>How i can get it?</p> Sat, 30 May 2020 04:11:07 +0000 4.2020-05-30 04:11:07.260792 Source and destination function in General Extrusion Operator <p>Hi All I want to define General Extrusin Coupling from a <em>curve</em> to a <em>region</em>. The source is a curve (PRQ) and destination is the region (ABC-PRQ). Can someone help to define Source fuction and destination function? The figure of the geometry is attached.</p> <p>Note: The co-ordinates of points A, B, C and P, Q, R are not fixed.</p> Fri, 29 May 2020 22:08:33 +0000 4.2020-05-29 22:08:33.260781 Restricting the domain Temperature <p>Hello, I was trying to develop a 2D heat source model for a Manufacturing process.Its observed that due to Pulsed heat source the Maximum temperature in the 2D rectangular domain crosses 30000K, which is impossible practically. I have also used the Phase change material option to take care of the melting of the metal. After it crosses the evaporation temperature the material has to be removed. 1) Is removal possible during the solving 2) If not ,How to restrict the Max temperature of the body to the Evaporation temperature?</p> <p>Gone through multiple discussions in forums but could not help,</p> <p>Thanks a lot, Stay safe.</p> Fri, 29 May 2020 18:53:45 +0000 4.2020-05-29 18:53:45.260771 Current density distribution on an electrode and cathode growth <p>Hi Everyone, I would like to look at current density distribution on electrodes in an electrochemical cell. I have the electrochemistry module. I have applied voltage boundary conditions on the top surface of the cathode and anode. Is it possible to get current density distribution by only applying voltage conditions only on the top surface or should we specify the surfaces of the electrodes? Also, can cathode growth be looked at by the electrochemistry module or do I need the electrodeposition module for that?</p> Fri, 29 May 2020 16:20:35 +0000 4.2020-05-29 16:20:35.260762 How to transfer quantities to another domain if two domains share a boudary <p>I have a porous solid and it is connected to the side of a pipe .<br /> The pipe will be defined by heat transfer in fluids and laminar flow The porous solid will be defined by heat transfer in porous media and darcy law(for pressure and velocity field).</p> <p>I would like the fluid (and heat) from pipe to enter the porous media. So I would like to know how to specify this as a boundary condition.</p> <p>Thanks</p> Fri, 29 May 2020 11:50:31 +0000 4.2020-05-29 11:50:31.260761 Simulation on Faraday rotation <p>Hello every one. It's Siyuan.</p> <p>I was trying to simulate the Faray rotation, using linearly polarized input light and asymmetric permitivity tensor with non-digonal components... However, there is always problem on the mesh and especially the boundary conditions...</p> <p>I attached the document in the google drive since it was a little bit bigger (6 MB) that the allowed file size (5 MB). (</p> <p>I will be very appreciated if you can help me and have a check!</p> <p>Sincerely Siyuan</p> Fri, 29 May 2020 11:01:14 +0000 4.2020-05-29 11:01:14.260753 void equations for Lagrange multiplier <p>Hello everyone, I am simulating with semiconductor interface and I am trying to specify a boundary condition using weak contribution. In fat, I am trying to connect an electric potential that I have calculated with electrostatic interface previusly and I want to use the electric potential in semiconductor interface (manully I am coupling physics). I tried using weak contribution and weak constraint for the boundary, but every time I want to compute, it says there are a number of void equations for lagrange multiplier, or there is an empty raw for matrix. Even when I want to set the electric potential to a simple number, this message shows up. I tried to set the initial value for the lagrange multiplier to a small number but it didn't work. Can someone help me? Thank you</p> Fri, 29 May 2020 08:37:49 +0000 4.2020-05-29 08:37:49.260751 Visualization of radiation pattern on geometry <p>Hello,</p> <p>Does anyone know how I can plot the radiation pattern of an antenna in combination with the geometry? The picture better explains what I mean... <img src="" alt="" /></p> Fri, 29 May 2020 08:18:23 +0000 4.2020-05-29 08:18:23.260741 Assigning permittivity dependent frequency <p>Hello. I am a new user of comsol multiphysics and I kindly want someone to help me concerning the below problem:</p> <p>I am trying to create a new(user defined ) material based on generated complex permittivity using Comsol 4.4. the data are arranged like this: f=(1,2,3,4) n=(0,5,10,15) k=(1,2,3,4). Where f, n, and k are the frequency, real part of refractive index and imaginary part of refractive index, respectively.</p> <p>how can I put those material properties in COMSOL ?</p> <p>Thank you</p> Fri, 29 May 2020 06:29:44 +0000 4.2020-05-29 06:29:44.260723 Full Field Formulation <p>Hello,</p> <p>When I use the full field solution in comsol for a two-mediums (Air/other_material) problem, I get oscillations in the magnitude of the electric field in air, which tells me that the plotted magnitude is the interaction of the incident and the reflected electric field. However, in the second interface, I do not get any oscillation, which tells me that it is only the transmitted field. Is this correct?</p> <p>Jose Santos</p> Fri, 29 May 2020 04:22:34 +0000 4.2020-05-29 04:22:34.260722 Difference of 2 between impedance and scattering BC <p>Hello,</p> <p>Does anybody know why there is a difference of 2 between an excitation with an impedance boundary condition compared to an excitation using scattering boundary condition. The scattering BC gives me twice the electric field than the impedance BC.</p> <p>Jose Santos.</p> Fri, 29 May 2020 04:18:41 +0000 4.2020-05-29 04:18:41.260712