Facing problem to write curl in exact solution

Hi Everyone

This is the exact solution "y_exact = curl(sin(pixy)) ". How can I define it FeniCS in a 2d domain ?

First of all, you need to specify what version of fenics you are using, ie. Legacy dolfin or dolfinx + version number.
Secondly, what is the curl of a scalar value?

Fenics version: 2019.2.0.dev0

y_exact = curl(sin(pixy)) is a vector valued function or approximated with P2 Lagrange polnomial

You cannot take a curl of a scalar function. sin(pi*x*y) is a scalar value, and the curl(a) where a is a scalar value is not defined. Are you sure you mean the curl and not the gradient or divergence?

Sir I want to write the exact solution d in FeniCS as shown in the screenshot. Here d is a vector otherwise \phi is not well defined.

You would need to define what the curl operator is supposed to do on a scalar value, as I do not know a scalar function called curl. See: Curl (mathematics) - Wikipedia and: https://www.quora.com/What-is-the-curl-of-a-scalar