关键词: 高速直升机, 共轴刚性旋翼, 高阶格式, IDDES, 非定常流动, 桨尖涡

Abstract: High-speed coaxial rotor systems generate complex, unsteady vortical flow structures and strong shock waves at forward flight, which significantly impact the aerodynamics, noise, and vibration characteristics of high-speed heli-copters. Capturing these flow phenomena with high resolution is one of the challenges in computational fluid dy-namics research for high-speed helicopters. To address this challenge, a dynamic overset grid system capable of load balancing in large-scale parallel computations has been developed. An efficient method for identifying overset relationships and an interpolation technique that maintains high-order accuracy at artificial boundaries have been proposed. A novel fifth-order WENO-K scheme with adaptively optimized spectral characteristics has been intro-duced to enhance the numerical resolution and preserve the structures of rotor tip vortices. Additionally, an im-proved Delayed Detached Eddy Simulation (IDDES) method has been combined to capture the smaller-scale vor-tex structures and their unsteady fluctuations in the wake region. High-accurate numerical simulations of unsteady vortical flow fields have been conducted for a simple four-blade coaxial rotor and an eight-blade coaxial rotor simi-lar to the X-2 configuration. This study focuses on the generation, development, evolution, and vortex interference mechanisms of blade tip vortices of high-speed rigid rotor. The computational results demonstrate that the high-order schemes, when combined with the IDDES method, effectively reduce numerical dissipation and enhance the resolution of multiscale turbulent structures. They successfully capture the rapid development and evolution of rotor tip vortices, as well as the blade-vortex interactions. The sophisticated horseshoe-shaped vortex surface structures formed at the trailing edge of the rotor blades are also discernible. These findings contribute to a deeper under-standing of the vortex interference mechanisms and aerodynamic noise in high-speed coaxial rotor flow fields.

Key words: High-speed helicopter, Coaxial rigid rotor, High-order scheme, IDDES, Unsteady flow, Blade-tip vortex