Hello,

I am currently working with FreeFrem during my internship and I get an error which I don’t understand. You can find my code following the link bellow my message. I took the code (which works) already written in the study made by Emil Garnell, Olivier Doaré and Corinne Rouby on Coupled vibro-acoustic modeling of a dielectric elastomer loudspeaker published in the Journal of the Acoustical Society of America. Their code allows to get the pressure field created by a membrane which vibrates with the implementation of perfectly matched layers. The acceleration g of the membrane is settled at the beggining of the code. I try to implement the electro-mechanical coupling to represent a real loud-speaker taking to account the action of the pressure on the membrane.

To do so I have taken the original code and I have made some modifications. I start with creating the mesh, the finite element space and writing the variationnal formulation which change a little bit compared to the initial program. The linear system is then of the shape : AP=F. Then I add two rows and two columns corresponding the the electro-mechanical equations to the matrix A, the position X and the electric charge Q are now new unknown. I also add two rows in the F vector. When I try to get the solution of this problem : Pn=An^-1*Fn, FreeFem writes the following error message :

« error operator * <18Matrice_Creuse_invISt7complexIdEE>, <14Matrice_CreuseISt7complexIdEE> »

I understand that FreeFem does not allow to give An^-1 and Fn as an argument to the operator *. It could stems from the difficulty to reverse the matrix, I tried the program with the initial solver (sparsesolver) and I tried UMFPACK but without more success. It is possible to reverse the matrix An, Matlab managed to do it. Do you know what is wrong with my code ? Could you advocate a solver relevant in the problem I try to solve ?

Here is the link towards my code(piston_norayleigh_strongcoupling_forum.edp) and the original code (without electromechanical coupling : piston_norayleigh.edp) :

Best

Mathieu S