Gr. Srinivasan et Wj. Mccroskey, EULER CALCULATIONS OF UNSTEADY INTERACTION OF ADVANCING ROTOR WITH A LINE VORTEX, AIAA journal, 31(9), 1993, pp. 1659-1666
The unsteady, three-dimensional flowfield of a helicopter rotor blade
in forward night encountering a concentrated line vortex is calculated
using an implicit, finite difference numerical procedure for the solu
tion of Euler equations. A prescribed vortex method is adopted to pres
erve the structure of the interacting vortex. The test cases considere
d for computation correspond to the two-bladed model rotor experimenta
l conditions of Caradonna et al. and consist of parallel and oblique i
nteractions. Comparison of numerical results with the test data show g
ood agreement for the surface pressures for both parallel and oblique
interactions at subsonic and transonic flow conditions. The results in
dicate that the subsonic parallel blade-vortex interaction is nearly t
wo-dimensional-like and the unsteady time-lag effects appear to be neg
ligible. However, both the three-dimensional and unsteady time-lag eff
ects are found to be important under supercritical now conditions and
these effects are accentuated in the presence of transonic shocks. In
contrast, the oblique blade-vortex interaction is unsteady and three d
imensional at both the subsonic and transonic now conditions.