Salini SIVADASAN Nair

Indian Institute of Technology Madras | IIT Madras · Department of Aerospace Engineering

Aeromechanical instabilities arising due to frequency coalescence of different modes of a helicopter rotor and fuselage system is investigated. The focus is on removing the small angle approximation typically used for ground resonance analysis and perform simulation of the resulting nonlinear model. The results reveal significantly different charac...

This paper studies aerodynamic effects of ground on regressive lag mode damping during ground resonance. The experimental investigation is performed on a scaled helicopter model built to simulate the ground resonance scenario. The study involves both stationary as well as dynamic (oscillating) ground conditions. Experiments are conducted by measuri...

A well-known phenomenon in rotorcraft, the ground effect, occurs when a rotor is at close proximity to the ground creating an obstruction to the trailing wake from the rotor. This results in an increase in thrust and a decreased inflow through the rotor disk, in turn affecting handling qualities. Until recently, analytical modelling of ground effec...

This paper addresses how dynamic inflow, while improving the correlation with ground-resonance measurements, could make the mode identification of the rotor-body-inflow system demanding. Specifically, the paper demonstrates dynamic inflow effects on the modes of two earlier tested configurations: configuration 1 with a nonmatched stiffness rotor (n...

Ground resonance is a type of aeromechanical instability that occurs when the helicopter is in contact with the ground. It may occur due to coalescence between frequencies of two modes of the system if damping is insufficient. In this paper, we analyze the phase relations between the fuselage states corresponding to the least damped mode (regressiv...

Dynamic inflow effects on stability and modes of a coupled rotor-fuselage system are investigated. Dynamic inflow effects are incorporated using Peters-He model. Characteristics of different modes associated with a coupled rotor-fuselage system are investigated. In addition to the magnitude of the states in the eigenvector (periodic eigenvector in...

The influence of rotor wake and ground effect on aeromechanical instabilities, specifically ground resonance is investigated. The analytical model considered has fuselage pitch, roll and blade flap, lag degrees of freedom. To analyze the system stability at different rotor rotational speeds, modal damping and frequency is computed using Floquet met...

The paper focuses on analysis of aeromechanical instabilities, specifically ground resonance in helicopters and active control methods for improving the existing stability margins. First, a simplified model of coupled rotor-fuselage system with translational fuselage degrees of freedom and blade lead-lag degree of freedom is considered. Anisotropy...