Higher-order Simulations of a Compound Helicopter using Adaptive Mesh Refinement

Higher-order methods and adaptive mesh refinement (AMR) have demonstrated their added value to numerical simulation of a variety of aerodynamic problems, including rotorcraft flow. Within this paper, the implementation of a higher-order spatial WENO (Weighted Essentially Non-Oscillatory) method for flux reconstruction and an AMR method for grid refinement into a comprehensive and approved rotorcraft simulation framework is discussed. A significant increase in computational efficiency by factor 15 can be achieved using higher-order methods. AMR allows a considerable reduction of required overall grid cells, and thus computational effort, to represent the occurring flow phenomena with equivalent accuracy. The rotorcraft simulation framework is applied to simulate a highly complex compound helicopter geometry with a variety of challenging phenomena. Flight mechanic trim and elastic blades are taken into account for a physical representation of the flight state. The benefit of the AMR technique in combination with the higher-order methods for an isolated rotor in hover and a complete helicopter configuration in cruise flight is investigated. A robust application of the AMR implementation is demonstrated, which shows a reduction of computational cost by 50% at high advance ratio cases without a noticeable loss of accuracy.