Post-projected Runge–Kutta methods for index-2 differential–algebraic equations Original Research Article

A new projection technique for Runge–Kutta methods applied to index-2 differential–algebraic equations is presented in which the numerical approximation is projected only as part of the output process. It is shown that for methods that are strictly stable at infinity, the order of convergence is unaffected compared to standard projected methods. Gauss methods, for which this technique is of special interest when some symmetry is to be preserved, are studied in more detail.