//  Fluid-structure interaction for a weighting beam sitting on a// square cavity filled with a fluid.int bottombeam = 2;border a(t=2,0)  { x=0; y=t ;label=1;};        //  left beamborder b(t=0,10) { x=t; y=0 ;label=bottombeam;};        //  bottom of beamborder c(t=0,2)  { x=10; y=t ;label=1;};       //  rigth beamborder d(t=0,10) { x=10-t; y=2; label=3;};     //  top beam real E = 21.5;real sigma = 0.29;real mu = E/(2*(1+sigma));real lambda = E*sigma/((1+sigma)*(1-2*sigma));real gravity = -0.05;mesh th = buildmesh( b(20)+c(5)+d(20)+a(5));fespace Vh(th,[P1,P1]);Vh [uu,vv], [w,s];cout << "lambda,mu,gravity ="<<lambda<< " " << mu << " " << gravity << endl;// deformation of a beam under its own weight // definition of 2 macro :real sqrt2=sqrt(2.);macro epsilon(u1,u2)  [dx(u1),dy(u2),(dy(u1)+dx(u2))/sqrt2] // EOMmacro div(u,v) ( dx(u)+dy(v) ) // EOMsolve bb([uu,vv],[w,s],solver=CG)=	int2d(th)(  		  lambda*div(w,s)*div(uu,vv)	                  +2.*mu*( epsilon(w,s)'*epsilon(uu,vv) )                  )  - int2d(th) (gravity*s)  + on(1,uu=0,vv=0)  ;//verbosity=100;plot([uu,vv],wait=1);plot([uu,vv],wait=1,bb=[[-0.5,2.5],[2.5,-0.5]]);mesh th1 = movemesh(th, [x+uu, y+vv]);plot(th1,wait=1);cout << " max deplacement = " << uu[].linfty << endl;