Aa. Hassan et al., EFFECTS OF LEADING AND TRAILING-EDGE FLAPS ON THE AERODYNAMICS OF AIRFOIL VORTEX INTERACTIONS/, Journal of the American Helicopter Society, 39(2), 1994, pp. 35-46
A numerical procedure has been developed for predicting the two-dimens
ional parallel interaction between a free convecting vortex and a NACA
0012 airfoil having leading and trailing edge integral-type flaps. Sp
ecial emphasis is placed on the unsteady flap motion effects which res
ult in alleviating the interactions at subcritical and supercritical o
nset flows. The numerical procedure described here is based on the imp
licit finite-difference solutions to the unsteady two-dimensional full
potential equation. Vortex-induced effects are computed using the Bio
t-Savart Law with allowance for a finite core radius. The vortex induc
ed velocities at the surface of the airfoil are incorporated into the
potential flow model via the use of the velocity ''transpiration'' app
roach. Flap motion effects are also modeled using the transpiration ap
proach. For subcritical interactions, our results indicate that traili
ng edge flaps can be used to alleviate the impulsive loads experienced
by the airfoil. For supercritical interactions, our results demonstra
te the necessity of using a leading edge flap, rather than a trailing
edge flap, to alleviate the interaction. Results for various time-depe
ndent flap motions and their effect on the predicted temporal sectiona
l loads, differential pressures, and the free vortex trajectories are
presented.