Hi everyone !

I am solving Navier-Stokes equations, on a [P2, P2, P1] space (velocity-velocity-pressure):

func PuPuPp=[P2, P2, P1];

fespace Uvvp(Th, PuPuPp);

Uvvp [ux,uy,up];

Moreover I define a space just for the velocity:

func PuPu=[P2, P2];

fespace Uvv(Th, PuPu);

Uvv [ffx,ffy];

I would like to define a prolongation matrix and a restriction matrix that could be used such that:

matrix projectionMatrix = ???;

matrix restrictionMatrix = ???;

ux[] = projectionMatrix * ffx[];

ffx[] = restrictionMatrix * ux[];

Can anyone, please, explain me how to define such matrices?

Best,

Lucas