Consider a solid circular domain defined by the set
$$\text{Circle}=\{(r \cos\theta, r \sin\theta)|r\in[0,1],\theta\in[0,2\pi]\}.$$
I want a simple algorithm for producing a quadrilateral finite element mesh over this domain. For a hollow circle, I can vividly see the idea of using the polar coordinates to create a mesh as below. However, for the case of a solid circle, using the same idea enforces the inclusion of triangular elements with one vertex at the center of the circle. I couldn't come up with a nice idea. Any suggestion is appreciated.
