Actually,

I just want to print the values of traction macros on the boundary of the domain. But it contains N.x and N.y unit outward vectors and it depends on u and p. how can I print out the values of traction vectors? Output of my problem is ux,uy, and p. I want to calculate traction(tx(u,p),ty(u,p)) on the boundary of domain.

/Problem

problem S ([ux, uy, p ],[vx, vy, q])

= int2d(Th)(Mu * (Gradient(ux)’ * Gradient(vx)

+ Gradient(uy)’ * Gradient(vy))

- p * Divergence(vx, vy)

- Divergence(ux, uy) * q)

-int1d(Th, Inlet, Outlet, Wall)(

-Mu*(traction(ux,uy)'*[vx,vy]))

+ on(Inlet, ux=uIn, uy=0.)

+ on(Wall, ux=0., uy=0.);

problem LinNS([ux1,uy1,dp],[vx,vy,q]) =

int2d(Th)(Mu*(Gradient(ux1)‘*Gradient(vx)*

+ Gradient(uy1)‘*Gradient(vy))*

+ UgradV(ux1,uy1, ux, uy)'[vx,vy]

+ UgradV(ux,uy,ux1,uy1)’[vx,vy]

- Divergence(ux1,uy1)*q - Divergence(vx,vy)**dp)*

-int2d(Th)(UgradV(ux,uy, ux, uy)'[vx,vy])

-int1d(Th, Inlet, Outlet, Wall)(

-Mu(traction1(ux1,uy1)’*[vx,vy]))

+on(Inlet, ux1=uIn, uy1=0.)

+on(Wall, ux1=0.,uy1=0.);