Effects of surface blowing/suction on the aerodynamics of helicopter rotor blade-vortex interactions (BVI) - A numerical simulation

Numerical simulations were conducted to investigate the effects of surface blowing and/or suction on the aerodynamics of the five-bladed MD-900 rotor in low speed descent flight, Special emphasis is placed on understanding the physics,associated with surface blowing/suction and the mechanisms which result in alleviating the aerodynamics of rotor blade-vortex interactions (BVI). Pertinent vortex wake parameters (e.g., spatial and temporal trajectories, strengths) were computed using the lifting-line rotor/helicopter trim code CAMRAD/JA. The results presented are based on the implicit finite-difference solutions to the unsteady three-dimensional full potential equation. Pn the potential solution, a surface transpiration condition was used to model vortex-induced effects as weal as the surface blowing/suction effects. An additional transpiration boundary condition was also imposed to emulate normal surface blowing and/or suction. Numerical results have indicated that surface blowing can be used as a viable technique to alleviate the temporally impulsive leading edge surface pressures known to be responsible for BVI noise. The effects of suction, on the other hand, are shown to have a detrimental effect ore BVI. Results for a model problem are presented to illustrate the similarities between the effects of blowing/suction, the combined use of blowing and suction and those which result from varying blade thickness and camber.