Discussion Forum

You just integrate the density.

Jean, where from do I have access to the "Integrate density" procedure?

You compute the integral of density using the same tools that you would use to integrate any other quantity, i.e. a model coupling (under Definnitions) of the integration type. If you've never used model couplings, you'll probably want to read on them in the User's Guide manual first.

I should add that if you are only interested in computing the mass as a postprocessing step (i.e. if you don't need to use that quantity in your model definition), then another, easier, approach consists in using Results>Derived Values to compute the integral.

Jean, thanks for taking the trouble to answer my question. I've tried to follow your advice and got a mass of zero (see attached file). Would you care to look at it, please?

From my posted questions it is easy to see that I'm not familiar with Cosmos yet, although I was keeping an eye on its development since it was just a PDE component of Matlab, then Femlab, etc.

In the engineering community we've been waiting for ages to get the flexibility Cosmos now offers. However, we need some easy to use basic tools for model verification, such as for mass, volume, inertia, etc., which I hope you guys are going to implement.

George

I am on vacation and without access to the software, but judging from your file name it looks like you might be dealing with a shell. In that case, you would want to perform an integration of the thickness times the density on the appropriate manifold.
If you need more further instructions regarding COMSOL, please contact COMSOL tech support.

Thank you.

Hi

1. In Comsol Definitions, select Integration.
2.In Geometric entity level, select Domain (specify the domains that you like compute)
3.copy the operator name, and paste in the variables expression, in my case intop1(acpz.rho), because I work with acoustic piezoelectric interaction (acpz)

Regards