说明：  Karman-Trefftz airfoil is an intriguing airfoil for which a complete set of exact solutions can be computed. This solution has been used by many people to verify the accuracy of their inviscid code (incompressible limit). If you have not, use this code now to generate a (quadrilateral or triangular) grid, run your code on it, compute the error, and verify the accuracy of your code. Me? I have used it for my third-order multigrid Cauchy-Riemann solver