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 sur face blowing and/or suction on the aerodynamics of the five-bladed MD- 900 rotor in low speed descent flight, Special emphasis is placed on u nderstanding the physics,associated with surface blowing/suction and t he mechanisms which result in alleviating the aerodynamics of rotor bl ade-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 presen ted are based on the implicit finite-difference solutions to the unste ady three-dimensional full potential equation. Pn the potential soluti on, 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 s urface blowing and/or suction. Numerical results have indicated that s urface blowing can be used as a viable technique to alleviate the temp orally impulsive leading edge surface pressures known to be responsibl e 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 blowin g/suction, the combined use of blowing and suction and those which res ult from varying blade thickness and camber.