How to get u_x ,u _y instead of nabla_grad(u)

Question

I want only "u_x" or "u_y" instead of the vector "grad(u)" . Does someone know this ,thanks!

Answer 1

Hi, you can use

du_dxi = Dx(u, i)
du_dxi = u.dx(i)
du_dxi = grad(u)[i]

to get the derivative of scalar function or expression with respect to x_i. There is more about the differential operators in the UFL manual here.

Comments

Thanks a lot ! :-)