You might be using the wrong output of the “curl” function to create the mesh plot. Calling “curl” with only one output argument gives you the curl angular velocity and not the curl z-component, which is what you need to get the mesh plot. You can refer to the documentation page for “ curl " for more information.
I suggest making the following changes:
>> [curlz, cav] = curl (x, y, Fx, Fy);
>> mesh (x, y, curlz)
I think this should resolve your issue.
