Dear all,

I hope I have not missed something obvious again but I'm looking to assign initial conditions for my variables \underline{u} , \rho and p.
Velocity, density and pressure respectively.

I have a mixed function space W,  and my first thought was to define initial variables by splitting a W function 

and then interpolating my expression for the exact solution for each variable
u_.sub(0).interpolate(exact_w)
r_.interpolate(exact_r)

but as I get the error