Time-parallel trim solution of helicopter rotors with large-scale 3D structures

This paper presents the application of a Modified Harmonic Balance method — a scalable and parallel in time algorithm for large-scale three-dimensional periodic rotor dynamics. The method is integrated in a three-dimensional rotor aeroelastic solver X3D and applied to a UH-60A-like fully articulated rotor, and the NASA Tilt Rotor Aeroacoustic Model (TRAM) proprotor. The predicted airloads are validated with flight and wind tunnel test data at lowspeed transition with wake induced impulsive airloads. The new harmonic balance solver is implemented on a hybrid – shared and distributed memory architecture and tested for convergence, scalability, and efficiency. The new solver converges toward a time-accurate solution with an order of magnitude speed up, and a performance of nearly 1 teraFLOPS. The significance of this conclusion is that the barrier of computational time for using high-fidelity three-dimensional structures for efficient trim solution can be overcome with the modified harmonic balance method demonstrated in this paper.