Computational modelling of helicopter high-frequency dynamics
Author(s)
Line, Andrew J.
Type
Thesis
Abstract
In order to improve the hover performance and maximum lift capabilities of the helicopter, modern rotor designs are incorporating high levels of blade twist - a design parameter which is known to have a significant effect on the aerodynamic loading and vibration levels of the rotor. The helicopter industry as a whole is currently unable to predict rotor vibration to acceptable levels of accuracy, nor is it able to capture the effects of blade twist on vibration levels - severely limiting its ability to exploit twist fully within new rotor designs. Recent literature has highlighted the potentially powerful effect that improved wake modelling could have on the prediction of vibrational loads. The primary aim of this research has been to assess the benefits of improved wake modelling, both in terms of the accuracy of predicted vibratory loads and in terms of sensitivity to blade twist. The Vorticity Transport Model (VTM). developed by Brown, is a grid-based computational fluid dynamic code which provides a comprehensive description of the generation and evaluation of helicopter wakes. Integration of the VTM with an industry-standard structural dynamics code? has allowed the benefits of improved wake modelling to be explored. The capabilities of the VTM itself have also been enhanced with the introduction of a new adaptive grid system and Fast Multipole algorithm for evaluating the velocity field throughout the computational domain. The predicted wake geometries, aerodynamic loading and rotor dynamics have been validated against experimental data for both hovering and forward flight. A detailed study of Harris' experimental work using the VTM has provided further insight into the primary physical mechanisms that control the evolution of rotor wakes in forward flight.
Version
Open Access
Date Awarded
2005
Advisor
Brown, Richard
Sponsor
Engineering and Physcial Sciences Research Council
Grant Number
No. 01305179
Publisher Department
Department of Aeronautics
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)