Aerodynamic analysis of groove based vortex trap configuration on the retreating helicopter blade

• Main Author: Yaakub, Mohd Fauzi
• Format: Thesis
• Language: English; English; English
• Published: 2019
• Subjects: TL Motor vehicles. Aeronautics. Astronautics
• Online Access: http://eprints.uthm.edu.my/30/1/24p%20MOHD%20FAUZI%20BIN%20YAAKUB.pdf; http://eprints.uthm.edu.my/30/2/MOHD%20FAUZI%20BIN%20YAAKUB%20COPYRIGHT%20DECLARATION.pdf; http://eprints.uthm.edu.my/30/3/MOHD%20FAUZI%20BIN%20YAAKUB%20WATERMARK.pdf; http://eprints.uthm.edu.my/30/
• Institution: Universiti Tun Hussein Onn Malaysia

The issue of high angle of attacks at the retreating blade receives attention from countless researchers because it is an important factor in the stability of the helicopter. The retreating blade stall will effect the stability of the helicopter due to the high angle of attacks. Prouty‟s helicopter data are used in this research to study the influence of the groove in the vortex trapped method on the helicopter stability. The method is implemented to control the flow of separation at the rotor blade on the retreating side of the rotor disc in forward flight conditions. One of the codes used to implement the method is the Blade Element Theory Code using Prouty‟s dataset. The code aids in the analysis of the aerodynamic characteristics of the helicopter main rotor blade. To validate the code, the angle of attack distribution along the main rotor blade in forward flight condition is compared to published data of Prouty‟s. Another approach is the use of Computational Fluid Dynamics to investigate the flow characteristics and aerodynamic parameters of the baseline helicopter aerofoil and modified helicopter aerofoil with the groove. The data obtained from both approaches are then combined in the analysis of the aerodynamic performance of both main rotor blades with or without the groove in forward flight condition. The influence of groove as a vortex trap is studied by means of the change in lift produced by the blade. The groove configuration is varied to determine its most suitable location, which is the critical sub-area at the retreating blade side, between 0.6R to 1.0R from the rotor hub, where R is the rotor disc radius. It is also found that the groove‟s location on the blade influences the choice of size. The best groove configuration is at 0.5c from the leading edge, with the size of 0.05c. The presence of groove affects the lift coefficient as simulated at 0° to 18° blade angle of attack. It is proven that the groove contributes significant aerodynamic capability in controlling the flow separation at high angle of attack. The important implication of this research is that the groove equipped helicopter blade offers an improvement in aerodynamic stability in which the load difference is 2.2% lower than that in the case of baseline blade. The blade also provides extra safety margin where the maximum angle of attack allowed is extra 6 degrees higher.