Flapwise Vibration Computations of Coupled Helicopter Rotor/Fuselage: Application of Multibody System Dynamics

Abstract

Natural vibration characteristics of rotating blades are of fundamental importance from the viewpoint of maneuvering, blade life, vibration levels, aeroelastic, and stability. Helicopters may have serious resonant vibration problems when the excitation frequencies are equal to some multiple of the rotational speed. To ensure that conditions susceptible to resonance do not exist within the range of operating speeds, it is necessary that the natural frequencies and mode shapes be determined accurately. On one hand, as the complexity of multibody systems and the methods used for their design and control increases, the need for more elegant formulations of the equations of motion becomes an issue of paramount importance. On the other hand, although processor speed has increased dramatically over the last decade, development of computationally efficient algorithms is still a major issue in multibody dynamics. The transfer matrix method for multibody systems (MSTMM) accounts for both aspects. Based on many advantages of MSTMM in studying multibody system dynamics, a scenario of dynamics coupling between the flexible twin blade rotor and flexible fuselage of a typical helicopter model is proposed. The dynamical model of the coupled system, its topological figure, the overall transfer equation, and the characteristics equation are developed. The flapwise vibrations characteristics are carried out to obtain uncoupled/coupled twin blade/fuselage system natural modes and frequencies as a function of rotor speed. Examples are performed to validate with those published in the literature and produced by Workbench ANSYS.

Multibody system transfer matrix method: The past, the present, and the future

“…The dynamics design and test levels, as well as dynamics performance of over 150 products, are improved substantially. MSTMM has been applied to various equipment systems, including spin tube gun, 83 self‐propelled artillery, 48 tank, 48 naval gun, 84 metal storm, 49 cannon on helicopter, 85 antiaircraft gun, 86 vehicular multiple launch rocket system, 47 tracked multiple launch rocket system, 87 airborne multiple launch rocket system, 88 shipborne multiple launch rocket system, 48 projectile, 89 feeding platform, 90 and parachute‐submissile 91 ; aeronautics and astronautics: wing, 92 helicopter, 93 aerospace aircraft, 94 launch vehicle, 95 vehicular missile system, 96 missile, 41 and inertial measurement unit system 52 ; ships: underwater towed system, 97 submarine, 98 and ship's antivibration system 99 ; vehicle: vehicle suspension, 100 truck car 101 ; machine tools: heavy duty machine tool, 102 fly‐cutting machine tool, 50 five‐axis CNC machine tool, 103 machine tool spindle, 104 and servo turret 105 ; various civil machineries: road roller, 106 screen vibration, 107 vibration compaction, 108 large‐scale rotary machine, 109 truck crane, 110 overhead crane, 63 mobile concrete truck, 111 buildings, and bridges: floating bridge, 112 super long stay cable, 113 composite Riser system, 114 reinforced thermoplastic pipe, 53 immersed tunnel, 115 earthquake‐resistant civil structures, 116 and high‐pressure gas well 117 ; various turbines: wind turbine, 118 wind turbine tower, 119 low‐pressure rotor of gas turbine, 120 diesel engine,…”

Improved incremental transfer matrix method for nonlinear rotor-bearing system

“…. Similar to general transfer matrix method for multibody system (MSTMM) [27][28][29], the state vector is adopted to describe the system. The difference here is that rather using the physical or modal coordinates as the state vector (as in MSTMM), the incremental of the Fourier series are used.…”

Free vibration analysis of a rotating double tapered beam with flexible root via differential quadrature method

“…One of the extensively studied topics is free vibration analysis or the computation of dynamic characteristics, which is a critical design and performance evaluation criteria designating the life of structure, operating limits and stability. Therefore, numerous numerical methods such as Adomian decomposition (Adair and Jaeger, 2018a, 2018b; Mao, 2014), differential transformation (Mei, 2008; Nourifar et al , 2018; Kaya, 2006; Kumar et al , 2019; Kurt and Kaya, 2019; Ozdemir and Kaya, 2006a, 2006b; Rajasekaran, 2013), differential quadrature (Bambill et al , 2010; Choi et al , 1999), dynamic stiffness (Banerjee et al , 2006; Banerjee and Kennedy, 2014), finite element (Abbas, 1986; Chung and Yoo, 2002; Hoa, 1979; Hodges and Rutkowski, 1981; Wang and Werely, 2004), Fourier series (Chen and Du, 2019), mesh free Galerkin (Panchore et al , 2018), power series (Adair and Jaeger, 2018a, 2018b; Huang et al , 2010), Rayleigh-Ritz (Oh and Yoo, 2016; Ramesh and Rao, 2014; Roy and Meguid, 2018), Ritz (Navazi et al , 2017), transfer matrix (Lee and Lee, 2018, 2020; Rui et al , 2018) and variational iteration (Chen et al , 2016) have been used to avoid possible resonance cases by computing the dynamic characteristics of rotating-beam structures more accurately.…”