Trigonometrical fitting conditions for two derivative Runge-Kutta methods

Two derivative Runge-Kutta methods are Runge-Kutta methods for problems of the form y′ = f(y) that include the second derivative y″ = g(y) = f′(y)f(y) and were developed in the work of Chan and Tsai (Numer. Alg. 53, 171–194 2010). Explicit methods were considered and attention was given to the construction of methods that involve one evaluation of f and many evaluations of g per step. In this work, we consider trigonometrically fitted two derivative explicit Runge-Kutta methods of the general case that use several evaluations of f and g per step; trigonometrically fitting conditions for this general case are given. Attention is given to the construction of methods that involve several evaluations of f and one evaluation of g per step. We modify methods with stages up to four, with three f and one g evaluation and with four f and one g, evaluation based on the fourth and fifth order methods presented in Chan and Tsai (Numer. Alg. 53, 171–194 2010). We provide numerical results to demonstrate the efficiency of the new methods using four test problems.