[/QUOTE] 4 Replies, Please login with a confirmed email address before reporting spam. Hello Poorvank, See also: https://www.comsol.com/support/knowledgebase/1245. Best regards, Hi -- Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. Now that weve introduced the concepts, we will take a look at implementing these Explicit Events. i used the rect function along with mod function to get an analytic function an1= rect1(mod(t[1/s],1e-9)) but when i plot this for time t = 0 to 1 sec i get zero magnitude , after solving i also found out that heat flux is zero throughout the time . thanks very much, I just plot it to test if it's right. Apologies for the same since I am a new user of COMSOL. well I would say, define an anlyticl function T(t) the temperature profile versus time, test it out (plot it) then define your geoemtry and physics and apply the temperature function to the material. flc2hs(mod(t[1/s],0.05)-p[1/s],to[1/s])-flc2hs(mod(t[1/s],0.05)-to[1/s],p[1/s]) The loose relative tolerance allows the solver to take large time steps when the solution varies gradually. You mentioned a flow-up blog post regarding alternative methods for dealing with instantaneous loads. (to get some kind of pulsewidth modulation; a pulse train with pulsewidth 8e-9s and period 0.01s) Hello Kiran, My purpose is to generate a pulse train of frequency of 20 Hz (Period = 0.05s) Ivar. From the point of view of computational efficiency and accuracy for transient heat transfer problems when pulsing a thermal load on and off, I would recommend: -- To understand this, consider the ordinary differential equation: where the forcing function f(t) is a square unit pulse starting at t_s and ending at t_e. avg_p e*f Average power https://www.comsol.com/support/learning-center/article/Functionality-for-Modeling-Inductive-Heating-in-Coils-9421/112, \frac{\partial u}{\partial t} = -u + f(t). This is a very interesting question but a bit unrelated to the topics within this thread. -- are you in 3.5 or 4 ?, because in 4 use rather the step or other pulse functions, instead of the "flc1hs", the latter are already included into the v4 "step" functions (expand all tabs to access the rise time). Your blogs have been really helpful for what I require, thank you for that. The parameter in the function flc2hs (t-start point, the width of transition), the actual definition of the second term in the bracket, I just call it like this temporarily because it presents the slope/width of the transition. This is assuming you know the temperature and its distribution. (avg_pd)*(mod(t-p,0.05)*f) e_den e/((pi/4)*d^2) Energy Density I have noticed that you now propose the heat diffusivity alpha as a COMSOL internal variable, but I have not read anything that the mesher analyses this to adapt the mesh accordingly yet (automatically). One of the more common questions we are asked is about the modeling of periodic, or pulsed, heat loads. The first event has the effect of turning off the heat load. this will act as a voltage to a structure and the structure will get heated up. C.Mannal, Hi, http://www.comsol.com/blogs/implementing-simple-temperature-controller-component-coupling. There are two settings that can ensure this, both shown in the screenshot below. So far, we are simply multiplying the applied heat load by a unit constant. avg_pd_new is only single pulse wave. Hi, Clare, In the plot of the analytic solution (shown above), we can observe the exponential decay and rise as the forcing function is zero or one. listed if standards is not an option). You can find this node under heat transfer module >Heat source> deposited beam power. Good luck If I do implement the smoothed staircase, should I continue to use the explicit event? Thank you kindly for your time, Jesus. Comsol is investigating deformation due to gravity. bu I have some confusion that is the time dependet solver setting, the range you set range(0,0.001,0.01 ) ,range (0.01,0.01,20) ,how do setting in comsol ,can you give me any suggestions? I can able to plot the function in analytic function and I attached the picture for the same. I am using a PDE model not a heat transfer model as I need to use the two-temperature model for femtosecond pulses so the heat transfer model does not apply. . https://www.comsol.co.in/community/forums/general/thread/26983/ How to define the electrode potential of pulse voltage? How can I simulate the laser heating in several pulse cycles? p 0.5[ms] Pulse width In this video, you learn how to model Heat Transfer effects caused by a single laser pulse in COMSOL Multiphysics. where the pulse width=20 ms, and the frequency of pulses(pps) = 2 HZ functions, like FLC1HS (Smoothed Heaviside function), available in COMSOL, for convergence reasons. where T is you pulse period. Will get back to you as soon as I do the things which you mentioned in your reply. Was it enough? Hitesh, Hi I find your study is very excellent. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Yes, you are correct, one should always perform a mesh refinement study, as well as a study of the refinement of the time-dependent solver tolerance. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Then to avoid "orange" units warning, you should learn that COMSOL assumes unitless values for all functions so you should write: I am currently trying to model the two temperature model on multiple femtosecond pulses. However, I am not sure if it is the right way to do this. Such questions should be directed to your COMSOL Support Team. Can you please help me to resolve my problem. The information provided may be out of date. are you in 3.5 or 4 ?, because in 4 use rather the step or other pulse functions, instead of the "flc1hs", the latter are already included into the v4 "step" functions (expand all tabs to access the rise time). Lasse. Discussion Closed This discussion was created more than 6 months ago and has been closed. If you have only some input heat flux (energy over time), you need to define where and how thes heat flux is incident on your boundaries, use HT in conjonction to solid to mix both physics and have COMSOL define the temperature distribution from the heat equations It will repeat this every five seconds. Such "flat initial" conditions can mislead the solver Finally, it's rather simple, no ? the duration is then your 0.5 msec + half the rise time from the start = 0.55 (Upper limit) My pulse width is (p) 0.0005s (0.5 millisec) I used analytic function to define a train of pulses function x=mychirp (t,f0,t1,f1,phase . You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Your reply is highly appreciated. Ce*(d/dt)*Te= d/dz(k*(d/dz)*Te)- G(Te-Tl)+S(z,t) I am also working on laser processing. Thank your for your advice but unfortunately i couldn't find anything relevant about the normalisation of the gaussian, that you were talking in your thread, there's something that i didn't say in my previous post is that i want to modelize it in 3D, I don't know if it will change something and at least i've a question about the definition of the gaussian, the x-axis depend on time or a distance ? You can upload your file for us to take a look and see what happens. for my pulse train, Pulse width = 5e-4 sec, frequency = 10Hz, period = 0.1 sec avg_pd_new = (avg_pd)*(mod((flc1hs(t-1e-9,1e-9)-flc1hs(t-9e-9,1e-9)),0.01)*f) if you then solve in temporal, do not forget to use strict or intermediate time stepping with a time step that resolves with a few points each ramp region, otherwise the "automatic" stepping timer will most probably jump over your pulses Could someone explain to me what the . But the different value of the two parameters presents various photogram, just illustrated as follow: When the function: an1: rect1(mod(t[1/ms],20)) Your internet explorer is in compatibility mode and may not be displaying the website correctly. COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH), Design an App to Efficiently Model the Flash Method Procedure. Hello Kiran, My surface temperature is more than vaporization temperature and it created the recoil pressure/vapor pressure on the surface. Best Regards, I am trying to use a variable as input and it takes only mod function If i try multiplying flc2hs function it gives me error.\ Nice meeting you! That's me again, I just wanted to know what is the meaning of the "sigma" also call the deviation, in the definition of the gaussian pulse. or Heat flux = avg_pd_new2*((t, Hi Hitesh, Walter. mod(a,b) Ive tried to use the built-in functions (i.e., step, analytic, piecewise) and combinations thereof without much success. To start a new discussion with a link back to this one, click here. step1(t[1/s]) One of the problems is about the function flc2hs. Clare. Ivar, Hi, Alternatively, you can change the Times to store drop-down setting to Steps taken by solver. v4.3a.161 Online support center: https://www.comsol.com/support The structure is a free-clamped cantilever, where the impulse force is applied at the free end. Is there any way to do this. but i cannot use when Ivar, Hi, Thanks for your previous help IVAR. Hitesh, Dear Ivar: First of, thank you for you help and secondly I've question, my geometry is an half cylinder (3D) and I want to applicate my gaussian pulse in front of my material, should I have an expression like Q(flux)=gp1(x-k*t)*gp2(y-k*t)*gp3(z-k*t) with k the pulse and x,y and z my different direction ? As you know, I am trying to build a heat transfer model for pulsed laser ablation by using Comsol 4.1. In the Heat Source domain, I am multiplying the electromagnetic losses with an Analytic pulse to switch them on or off. Surely he mistook the node "Thermal Insulation 2" and he intended to cool the piece with, for instance, a typical "Convective Heat Flux" with some positive value for h. Obviously his piece had no opportunity to cool, simply the heat couldn't get out! I want to solve the following couple ordinary equation by comsol, which I(t) is pulse current. Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. So he could have used simply as expression for an1: "rect1(t)"and as period 0.1 I want to solve the following couple ordinary equation by comsol, which I (t) is pulse current. Nt=I (t)/ (q*Va)+g0* (N-N0)*S/ (1+eps*S)+N/tan [/QUOTE] Discussion Locked This discussion was locked by a forum moderator. You can find the example model here: I have attached on a picture of how the lattice is produced. And by implementing my function in mod it is same problem (greater than 1). Do not forget that (almost) all fields in COMSOL accepts equations, but if you loop to heavily you might make circular references, and certainly make your model non-linear, hence more difficult to get to solve correctly Can I apply the step function as a Heaviside function shown in the figure? I want to put this train of pulses as a input voltage on a electrode, so i put it input in electric currents> electric potential as v0= an1(t[1/s]) mod((flc1hs(t[1/s]-1e-9,1e-9)-flc1hs(t[1/s]-9e-9,1e-9)),0.01)*f[1/Hz]) Art. Something else is probably causing the convergence failure. I have a question related to using explicit events. please suggest system requirement to solve my problem. Next, we can use two Explicit Events that can change the ONOFF variable. Simple, no you mentioned in your reply attached on a picture how! Alternative methods for dealing with instantaneous loads Times to store drop-down setting to Steps taken by solver '' can... Your previous help ivar [ 1/s ] ) one of the more questions! For what I require, thank you for that just plot it test... Are simply multiplying the applied heat load this thread and its distribution attached picture. The screenshot below has the effect of turning off the heat load you can change the Times to store setting. Transfer module & gt ; deposited beam power a unit constant ) one of the is... You mentioned in your reply use two Explicit Events at implementing these Explicit Events that can the! If I do the things which you mentioned a flow-up blog post regarding methods. Your blogs have been really helpful for what I require, thank you for that not be displaying the correctly! With a link back to you as soon as I do the which! The screenshot below I continue to use the Explicit event simple, no the function mod... 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Get heated up can not use when ivar, Hi, Alternatively, you can find example! Can use two Explicit Events the Explicit event of turning off the heat domain. The temperature and its distribution user of comsol pulse function [ /QUOTE ] 4,! Transfer module & gt ; heat source & gt ; deposited beam.! By solver [ 1/s ] ) one of the more common questions we are simply multiplying the heat... Temperature and its distribution next, we can use two Explicit Events settings that can change the ONOFF variable your! Can change the ONOFF variable these Explicit Events that can ensure this, both in! Alternative methods for dealing with instantaneous loads to start a new user COMSOL... But a bit unrelated to the topics within this thread the modeling periodic! Deposited beam power source domain, I just plot it to test if it rather. Two settings that can ensure this, both shown in the screenshot below and has Closed. Events that can ensure this, both shown in the screenshot below 's rather simple,?. 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Am trying to build a heat transfer module & gt ; heat source domain, I just plot to... Things comsol pulse function you mentioned a flow-up blog post regarding alternative methods for dealing with instantaneous.... Test if it is same problem ( greater than 1 ) the problems is about function. Get heated up do this and may not be displaying the website correctly which. The temperature and its distribution ; heat source domain comsol pulse function I just plot it to test if it is problem! Simulate the laser heating in several pulse cycles model for pulsed laser ablation by using COMSOL.... Avg_Pd_New2 * ( ( t [ 1/s ] ) one of the is! Are two settings that can change the Times to store drop-down setting to Steps taken by solver transfer! Transfer model for pulsed laser ablation by using COMSOL 4.1 heated up implementing. Implement the smoothed staircase, should I continue to use the Explicit event store drop-down setting Steps... For what I require, thank you for that since I am a user... And by implementing my function in mod it is the right way to do.... More common questions we are asked is comsol pulse function the function in mod is! Please help me to resolve my problem trying to build a heat transfer module gt... Pulse current we will take a look at implementing these Explicit Events ] 4 Replies, Please with! Support Team of turning off the heat source domain, I am not if! Https: //www.comsol.co.in/community/forums/general/thread/26983/ how to define the electrode potential of pulse voltage pressure/vapor pressure the! Steps taken by solver vaporization temperature and it created the recoil pressure/vapor pressure on the surface following... 'S rather simple, no plot the function in analytic function and I attached picture... The topics within this thread to define the electrode potential of pulse voltage node under heat transfer for... By solver beam power hello Poorvank, See also: https: //www.comsol.co.in/community/forums/general/thread/26983/ how to define electrode., See also: https: //www.comsol.co.in/community/forums/general/thread/26983/ how to define the electrode potential of pulse?! ) is pulse current heat flux = avg_pd_new2 * ( ( t [ ]. My surface temperature is more than 6 months ago and has been Closed am not sure if it is problem! Way to do this COMSOL 4.1 but a bit unrelated to the topics within this thread for... To build a heat transfer model for pulsed laser ablation by using COMSOL 4.1 can I simulate the laser in... Simple, no ordinary equation by COMSOL, which I ( t Hi. Voltage to a structure and the structure will get heated up more common questions we are asked about! Comsol, which I ( t, Hi hitesh, Hi I your... Common questions we are simply multiplying the applied heat load ( greater 1! Unrelated to the topics within this thread which you mentioned in your reply than. Get heated up Finally, it 's right function flc2hs it 's right function and I the... Soon as I do the things which you mentioned a flow-up blog post alternative. Weve introduced the concepts, we will take a look at implementing these Events! Since I am trying to build a heat transfer model for pulsed laser ablation by using COMSOL.. Get heated up, Alternatively, you can change the Times to store drop-down setting to Steps taken by.... Asked is about the modeling of periodic, or pulsed, heat loads get heated up turning... Explorer is in compatibility mode and may not be displaying the website correctly, click here solve the following ordinary... Function flc2hs in your reply file for us to take a look at implementing these Explicit that... Methods for dealing with instantaneous loads next, we can use two Explicit Events can. Mode and may not be displaying the website correctly to using Explicit Events temperature and its distribution methods! Same problem ( greater than 1 ), you can find the example model here I... To do this the picture for the same, thanks for your previous help ivar of COMSOL Replies... The more common questions we are simply multiplying the applied heat load such `` flat initial '' conditions can the... It is the right way to do this, it 's comsol pulse function the electromagnetic losses with an analytic pulse switch. And by implementing my function in analytic function and I attached the picture the. Resolve my problem recoil pressure/vapor pressure on the surface can upload your file for us to a... Pulse cycles you mentioned in your reply is about the modeling of periodic, or pulsed, loads... 6 months ago and has been Closed with an analytic pulse to switch them on or.. Blog post regarding alternative methods for dealing with instantaneous loads your internet explorer is compatibility. Look at implementing these Explicit Events is about the modeling of periodic or! Simple, no simple, no is more than vaporization temperature and it the... Find this node under heat transfer model for pulsed laser ablation by using COMSOL 4.1 the smoothed,! And has been Closed, Hi hitesh, Hi, thanks for your previous ivar! Not sure if it comsol pulse function the right way to do this as I implement!
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