demo.edp

FreeFem++可以生成高质量的有限元网格。可以用于流体力学

border aaa(t=0,1){x=t;y=0;label=1;};
border bbb(t=0,0.5){x=1;y=t;label=2;};
border ccc(t=0,0.5){x=1-t;y=0.5;label=3;};
border ddd(t=0.5,1){x=0.5;y=t;label=4;};
border eee(t=0.5,1){x=1-t;y=1;label=5;};
border fff(t=0,1){x=0;y=1-t;label=6;};
mesh Th = buildmesh (aaa(6) + bbb(4) + ccc(4) +ddd(4) + eee(4) + fff(6));
mesh Th2 = movemesh(Th,[x+1.1,y]);
fespace Vh(Th,P1);
fespace Vh2(Th2,P2);
fespace Vh21(Th2,P1);

Vh u,v,zero;
Vh2 u2,v2;
Vh21 dxu2,dyu2;
u=0;
u2=0;
zero=0;
func f= 1;
func g= 0;
int i=0;
real error=0.1, coef= 0.1^(1./5.);
problem Probem1(u,v,solver=CG,init=i,eps=-1.0e-6) =
    int2d(Th)(  dx(u)*dx(v) + dy(u)*dy(v)) 
  + int2d(Th) ( v*f ) 
  + on(1,2,3,4,5,6,u=g)  ;
  
problem Probem2(u2,v2,solver=CG,init=i,eps=-1.0e-6) =
    int2d(Th2)(  dx(u2)*dx(v2) + dy(u2)*dy(v2)) 
  + int2d(Th2) ( v2*f ) 
  + on(1,2,3,4,5,6,u2=g)  ;
  
real cpu=clock();

for (i=0;i< 10;i++)
{ 
  
  real d = clock();
  Probem1; 
  Probem2; 
  plot(Th,u,Th2,u2,wait=1);
  Th=adaptmesh(Th,u,inquire=1,err=error);
  dxu2=dx(u2);
  dyu2=dy(u2);
  Th2=adaptmesh(Th2,dxu2,dyu2,inquire=1,err=error,ratio=1.5,hmin=1e-5);
  
  cout << " CPU = " << clock()-d << endl;
  error = error * coef;
} ;

 cout << " CPU = " << clock()-cpu << endl;