In recent experiments, it was observed that the tip vortices shed from a two-bladed rotor can interact significantly. The interaction consists of a turn of the tip-vortex from one blade rolling around a turn of the tip-vortex from the other blade. Visualized in a planar light sheet, the two vortices spiral around each other prior to merging into a single vortex. One complete cycle of the roll-up process takes about one and one-half rotor cycles. This behavior is analogous to the interaction which takes place between two ring vortices and the numerical calculations shown here demonstrate this similarity. It is observed that the pair of rings, placed initially parallel and of the same strength roll around each other, by alternate contraction and expansion of the ring radius. Numerical calculations show that the ring interaction is complicated when the rings are initially inclined with respect to one another. The experimental configuration of a two-bladed rotor in axial flight is considered next. A lifting-line theory is used to model each rotor blade and a fully unsteady computation of the motion of the tip-vortices is carried out using a fourth-order accurate Adams-Moulton method to advance the vortices. The modified Biot-Savart law is used to describe the vortex structure. It is shown that the tip-vortex interaction is periodic and deterministic and results for the tip-vortex paths are seen to be in good agreement with experimental results.
Interaction of tip-vortices in the wake of a two-bladed rotor in axial flight
Wechselwirkung der Spitzenwirbel im Nachstrom eines zweiblättrigen Hubschrauberrotors beim Horizontalflug
Journal of the American Helicopter Society ; 45 , 3 ; 157-164
2000
8 Seiten, 13 Bilder, 1 Tabelle, 22 Quellen
Aufsatz (Zeitschrift)
Englisch
Interaction of Tip-Vortices in the Wake of a Two-Bladed Rotor in Axial Flight
Online Contents | 2000
|BLADE TIP-VORTICES OF A FOUR-BLADED ROTOR WITH AXIAL INFLOW
British Library Conference Proceedings | 2019
|British Library Conference Proceedings | 2011
|