Numerical Research on the Unsteady Evolution Characteristics of Blade Tip Vortex for Helicopter Rotor in Forward Flight
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ORIGINAL PAPER
Numerical Research on the Unsteady Evolution Characteristics of Blade Tip Vortex for Helicopter Rotor in Forward Flight Zhou Ye1
· Fengjiang Zhan1 · Guohua Xu1
Received: 16 January 2019 / Revised: 16 January 2020 / Accepted: 30 January 2020 © The Korean Society for Aeronautical & Space Sciences 2020
Abstract A high-resolution numerical method is developed to simulate the generation and evolution progress of the blade tip vortex for helicopter rotor in forward flight. In the current method, the Navier–Stokes equation is adopted as the governing equation. Along with fifth order WENO scheme, the upwind Roe scheme is employed for the calculation of convective flux. A dual time-stepping scheme is utilized for time discretization, and the LU-SGS scheme is used for every pseudo time step. The Spalart–Allmaras model is selected as the turbulence model. To trim the rotor in forward flight, a high-efficiency trim method is introduced to the current solver. Results for cases in different forward flight conditions show that trimming process has a great influence on the evolution characteristics of the rotor tip vortex. Compared with the cases with different Mach numbers, the evolution characteristics of rotor tip vortex have larger difference for cases with different advance ratios. Keywords CFD · Rotor · Helicopter · Tip vortex · Forward flight
1 Introduction As one of the most important parts for the helicopter, the rotor endows helicopter with the capacity of hovering and vertical take-off and landing. However, the concentrated vortex is induced during the rotation of the rotor blade, and the vortex may interact with rotor blades and some other helicopter parts, which leads to severe problems in the aspects of vibration and aerodynamic noise [1, 2]. Therefore, researchers have made plenty of studies on the generation and evolution characteristics of the rotor blade tip vortex. Furthermore, the active and passive control methods [3, 4] for rotor blade tip vortex in hover have been investigated. Previously, due to the limitation of computer technology and numerical method, experimental methods were adopted to investigate the vortex characteristics [5, 6]. The movement of tip vortex can be observed visually by experiment, but the boundary flow at the tip of a rotor blade cannot be captured in detail. As a result, the essence of the vortex generation can be hardly revealed. However, with the fast development
B 1
Zhou Ye [email protected] Key Laboratory of Advanced Technology for Small and Medium-Sized UAV, Ministry of Industry and Information Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
of computer and CFD technologies, the numerical method is more and more popular in the research of the rotor blade tip vortex [7, 8]. In 2001, the numerical research of tip vortex for rotor in hover has been made by Liu [9], in which the vortex structure was captured and compared with experimental data. Employing an overset mesh system, the tip vortex of a single-bladed hovering
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