Discussion Forum

Rectangular pulse should be difficult, if not impossible. Try checking if they have heaviside functions in Comsol. But even then, I am unsure if you would be able to have high enough sampling to capture that jump discontinuity. I would rather suggest you to think along a ramp pulse which has the added advantage of being physically possible.

Providing sinusoidal signal is easy. Use sin(f0*t) by specifying the value of frequency f0. I would also suggest you to search this topic in forum's archive. There should be something interesting.

All the best.

Hi!

If I understood you correctly, you can define square pulse of duration 'pulse_width' and pulse period of 'pulse_period' just simply by the following variable
pulseON=(mod(t,pulse_period)<=pulse_width)

Then you just multiply your time-dependent variable with pulseON.
flow_pulsed = flow * pulseON

let's say
pulse_width = 1 s
pulse_period = 5 s

then for
t = 0.5 s pulseON = 1
t = 1 pulseON = 1
t = 3 pulseON = 0
t = 10.5 pulseON = 1
t = 22 pulseON = 0

Hope I got you right.

Hi,
I wonder if you manged to solve the problem

Dear Andriy:

I tried to use the suggestion given by you on the blog and also tried to implement different suggestions on the Comsol Forum , but I havenot achieved desired result.

My Objective: Pulse width = 0.5ms, frequency = 10Hz, period = 1/frequency = 0.1s. Heating for 1sec and cooling for 5 sec.

Baed on your suggestion, pulseON=(mod(t,pulse_period)<=pulse_width), which is writen in my model as follows

Heat flux = avg_pd_new1 = avg_pd*(mod(t,0.1)<=5e-4)

My problem is : Even if I get the plot of pulse train of frequecy 10Hz and pulse width 0.5 ms, which I can plot on analytic function (an1), but my output remains ON only for the first pulse and rest is OFF.

Also, I did tried several other suggestion, which is plot in analytic function as an2,an3

Please suggest me some solution. I am attaching my model for reference.

Regards,
Hitesh