The Aerodynamics Investigation of Vortex Trap on Helicopter Blade
During helicopter forward flight, the retreating blade revolves at high angle of attack compared to advancing blade in order to balance the lift and also to stabilise the helicopter. However, due to the aerodynamics limitations of the retreating blade at forward flight, stall may occur at high angle of attack compared with the advancing blade. This phenomenon is dangerous for pilot when controlling and balancing the helicopter while flying against strong wind. This paper investigates the capabilities of introducing multiple vortex traps on the upper surface of the helicopter airfoil in order to delay the stall angle of retreating helicopter blade. Blade Element Theory (BET) was applied to scrutinize the lift force along the helicopter blade. Computational Fluid Dynamic (CFD) analyses using the Shear-Stress Transport (SST) turbulence model was carried out to investigate the effect of groove on delaying the stall and to predict the separation of flow over the airfoil. Based on the CFD analyses, the optimization of the groove was done by analyzing the numbers and locations of the grooves. Finally, the results from both BET and the CFD analyses were utilised to obtain the lift force achieved by the vortex trap. The study showed that the presence of multiple vortex traps has successfully increased the lift coefficient and most importantly, delaying the stall angle.
R. Varatharajoo, E. J. Abdullah, D. L. Majid, F. I. Romli, A. S. Mohd Rafie and K. A. Ahmad
M.F. Yaakub et al., "The Aerodynamics Investigation of Vortex Trap on Helicopter Blade", Applied Mechanics and Materials, Vol. 225, pp. 43-48, 2012