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How to convert a wave equation with second-order time derivative into its weak form

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Hi, everybody:

I have a problem and wish to get help from you.

When I studied the example "a Vibrating Membrane" in the Model Library of Femlab 3.1, I wanted to convert the equation d^2u/dt^2-(uxx+uyy)=0 into the weak form. But in this equation there is a second-order time derivative, it means a problem to me and I ONLY can deal with fisrt-order time derivative.

So anybody can give me some suggestions or tell me how to convert it?


Great thanks.




0 Replies Last Post 2010年3月22日 GMT-4 09:31
COMSOL Moderator

Hello Wei Liu

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