Singular matrix error

Hi,

I am new to Comsol. I have been trying to simulate flow over NACA4412 airfoil. I have been using circular domain.
My boundary conditions are 1. no slip on the airfoil surfaces 2. inlet velocity - 25 m/s and 3. outlet .
Every time I try to compute it says Singular matrix error, there are equations giving Nan/Inf in the matrix rows.I have attached the mph file.
Please help.

Thanks