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Hi

but you have already a predefine Gaussian "pulse funtion" in v4 (check under the Definitions node), the only thing to remember is that the input variable for functions must be made "dimensionless", hence use "t[1/s]", instead of just "t"

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Good luck
Ivar

Thanks Ivar.

The setup with the built in function is a little different from what I want.

I am very new to the program and wondering, is it alright to model the pulse like this:

Under Variables:

name: gauss_pulse
expression: v_max*exp((-(100-t[1/s])^2)/100)
units: [V]


and then plug this into the electromagnetic wave; under Port 1
E_0 = gauss_pulse[1/m]

This is put into the y portion, and the x and z are left at 0.

Thanks for the help,

John

I am wondering what the best way to model a simple gaussian pulse traveling through air and hitting water.

I am completely lost because whenever I try to do this in the transient electromagnetic module, the only option for port is LUMPED port. This is apparently only useful for metal interfaces. I also can't find the option for perfectly matched layers.

Online, all I can find are models and tutorials for constant sources in the steady state (such as joule heating through metal, etc). I am interested in the transient response to a short pulse, and am sure the solution is simple.

Any help is really, really appreciated.

-John

(I have attached my attempt in a module. I tried to label everything to make it as simple as possible).

I haven't worked with transient cases in version 4 but extensively tried in 3.5 series. But I suppose my knowledge of these simulations is not entirely outdated as there has been no mentioned updates to transient simulations in released notes of 4.x series.

The bad news for you is that Comsol does not have PMLs in transient simulations. The only source excitation and absorbing boundaries available are Scattering boundaries (that was until 3.5a). Now scattering boundaries, according to docs, are capable of absorbing plane wave reflections only. This really leaves the transient module extremely limited in application to realistic time domain simulations.

Thanks for the reply.

I will not worry about the PML for now.

All other things aside, I am just wondering how to create an electromagnetic wave with a gaussian profile and watch it propagate. Is this possible to do in COMSOL?

I am very lost but since this is the most basic part of my project I would really appreciate any help.

Thanks,

John

Well, I didn't try but why not? One little bit of round-about method is outlined in the following tutorial in 3.5a. You will have to guess how to export it to 4.x

www.comsol.com/showroom/gallery/956/