The relevant code-snippets I use is

def normal_grad(f,n):

return f.Diff(x)*n[0] + f.Diff(y)*n[1]

Vh = H1(mesh, order=order, dirichlet=[1,2,3,4],flags={“dgjumps”: True})

v = Vh.TestFunction()

nF = specialcf.normal(2)

vn = normal_grad(v,n)

vno = normal_grad(v.Other(),nF)

vnno = normal_grad(vno,nF)

vnn = normal_grad(vn,nF)

and I get error

NgException Traceback (most recent call last)

in

179 jump_u_2 = normal_grad(un,nF) - normal_grad(uno,nF)

180 vnno = normal_grad(vno,nF)

→ 181 vnn = normal_grad(vn,nF)

182 jump_v_2 = vnn-vnno

183

in normal_grad(f, n)

1 def normal_grad(f,n):

----> 2 return f.Diff(x)*n[0] + f.Diff(y)*n[1]

3

NgException: Deriv not implemented for CF N5ngfem23NormCoefficientFunctionE

Has anyone stumbled upon this error before? I find it weird since I can do the same thing for a TestFunction, and it works. I am trying to implement higher order directional derivatives.

Best regards,

Henrik