A discrete approach to modelling helicopter blade sailing.

摘要

Blade sailing is an aeroelastic phenomenon which can occur during the engage and disengage phases of shipboard operations. This phenomenon is characterized by large blade deflections which are known to occur mainly at low rotor rotational speeds in high wind and sea conditions. Proper examination of this phenomenon requires adequate modelling of many contributing factors, including system dynamics, ship motion, airwake modelling, and aerodynamics. The research encompassed in this thesis sought to achieve a greater understanding of the factors that affect the blade sailing phenomenon through numerical modelling of the system as a whole.;Novel models for system dynamics and ship airwake were developed under this research programme. The dynamic model is comprised of a series of rigid segments, which allows the analyst to completely define the parameters of the system, including number of blades and blade segments. The model also allows the inclusion of coupled stiffness terms, and a method for calculating the equivalent lumped stiffnesses from continuous coupled stiffness distributions. The numerical model was shown to capture non-linear, coupled, flexible beam bending behaviour through validation against published experimental data and analytical models.;The airwake model is based on experimental data, and incorporates changing mean and turbulent flow characteristics over the flight deck in space, time, and with ship deck roll angle. The experimental research showed that ship motion changes the airwake significantly. A novel approach to the modelling of spatially- and temporally-correlated turbulence was developed, which recreates the time history of turbulent velocity fluctuations as experienced by a specific point on the rotating blade.;Using these and previously developed models for ship motion and for blade aerodynamics, a comprehensive model of the system was developed and validated in combined blade sailing-like conditions through experiment. The results of the experiment support the claims that the developed numerical tools capture the important aspects of the blade sailing environment, and that the interplay between the contributors to blade sailing motion is very complex.;The goals of this research, to study the contributors to the blade sailing phenomenon, and to develop validated modelling tools for this purpose, were achieved through this research.