Latest Discussions - COMSOL Forums Most recent forum discussions Mon, 01 Jun 2020 18:36:58 +0000 COMSOL Forum: Latest Discussions Repetitive nanosecond pulsed plasma <p>Hi,</p> <p>Can I model Repetitive nanosecond pulsed plasma with Comsol? If yes can you please introduce me some ood tutorials and materials?</p> <p>Thanks,</p> Mon, 01 Jun 2020 18:36:58 +0000 4.2020-06-01 18:36:58.260982 JH+HT+TS <p>Good afternoon. I ask you to suggest what is better to do in this situation I am trying to simulate the heating of a nichrome thread so that the heat that is released during the heating process is used to heat a bimetallic plate and to simulate the thermal expansion of this plate. I was able to simulate the Joule heating, but I can not use the heat of the filament to heat the plate. Thank!</p> Mon, 01 Jun 2020 16:54:29 +0000 4.2020-06-01 16:54:29.260981 Surface Roughness- B parameter <p>Hello, I am currently trying to simulate surface roughness on the walls in my microchannel, and have read on several forums that the B parameter in the Turbulent Flow k-epsilon physics in the CFD Module can achieve this.</p> <p>I have found that the default value is 5.2 corresponding to smooth walls, and was wondering what is the correlation between the B values and real-life measurements (cm,mm,nm etc)?</p> Mon, 01 Jun 2020 16:28:06 +0000 4.2020-06-01 16:28:06.260962 the problem of "the plot is empty" <p>Hello,</p> <p>I was designing few electrodes with applying few voltage and try to get the potential curve distribution. But aftering performing calculate, there is some thing wrong, the warning is "the plot is empty", does anyone know how to solve this?</p> Mon, 01 Jun 2020 15:24:12 +0000 4.2020-06-01 15:24:12.260953 Effect of magnetic field and ultrasound <p>Dear Professor,</p> <p>We are students from the University of Nizwa. We are currently working on a graduation project. The topic of the project talks about ( development of pyrolysis media based on integration of DND-jet plasma with physical induced effect )</p> <p>We conducted a study to expose a polymer piece to a plasma. It is generated within a specific area within the tube. We also used three types of models: - fluid flow - dilute species transfer<br /> - heat transfer Then, we obtained logical results using a series of interactions. Also, We have prepared an in-depth numerical study to find the effect of magnetic and Ultrasound fields on plasma interaction with the polymer. It is scientifically proven as indicated in a mechanism in (Plasma Decay in the Afterglow of High-Voltage Nanosecond Discharges in Unsaturated and Oxygenated Hydrocarbons).</p> <p>In addition, We develped the model utilizing the five modules as follows: 1)Fluid flow+Chamical Species+heat transfer modules are enabled 2) Fluid flow+Chamical +Magnetic+heat transfer modules are enabled 3)Fluid flow+Chamical Species+Ultrasound+heat transfer modules are enabled 4)Fluid flow+Chamical Species+Ultrasound+Magnetic+ heat transfer modules are enabled Unfortunately، We obtained similar results for the application case of the first three models. we have one small doubts and we hope you can help us to understand it better. "How to find the effect of Magnetic field and ultrasound on plasma-stimulating polymer reaction?</p> <p>Thank you for taking the time to answer our question and we look forward to hearing from you.</p> Mon, 01 Jun 2020 11:27:37 +0000 4.2020-06-01 11:27:37.260931 Port Boundary <p>Hello, all</p> <p>Does the port in <em>wave optics</em> <strong>absorbs</strong> all the incident power ?</p> <p>for example, I have two periodic ports. Port#1 is ON and port#2 is OFF. The <em>electric mode field amplitude</em> of the port#1 is (0,1,0). I want to read the Transmittance of power to port#2. So I want to read <strong>abs(ewfd.S21)^2</strong>.</p> <p>What <em>electric mode field amplitude</em> I should set to the port#2 ? Does it matter for the listener port (=port#2) ?</p> <p>Thanks !</p> Mon, 01 Jun 2020 10:03:23 +0000 4.2020-06-01 10:03:23.260921 I would like to solve an equation with the PDE interface in Comsol5.4.I use coefficient form and wonder if the coefficients can be dependent on the same varaible the equation is solving for? <p>Hello, I would like to solve an equation with the PDE interface in Comsol5.4.I use coefficient form and wonder if the coefficients can be dependent on the same varaible the equation is solving for?</p> <p>So, if the equation is solving for T, can I put the coefficients of the equation to be a function of T?</p> <p>Looking forward to your reply.</p> <p>Jin</p> Mon, 01 Jun 2020 00:28:37 +0000 4.2020-06-01 00:28:37.260883 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 COMSOL 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