An Investigation of Drag Associated with the Upswept Rear Fuselage of a Helicopter

摘要

The effect of flow changes around the rear fuselage of typical helicopter configurations was studied using a one-fifth scale Westland Lynx model. Modifications were added to the rear fuselage in order to vary its geometry. The model was wind tunnel tested at a Reynolds number (based on the length of the fuselage body) of 3.5 million. Two basic fuselage configurations were tested, one with a parallel sided rear fuselage, the other with taper. The effect of upsweep angle and the incidence of the model on lift, drag, and pitching moment was studied. Pressure readings were taken on the rear upswept face and a series of flow visualization tests was also done. Dramatic changes in the flow pattern were found on the parallel sided fuselage configuration. A definite correlation between the pressure changes on the upswept surface associated with the changing flow pattern there and the sudden drag change was confirmed. It was found that rear fuselage taper effectively killed off the critical flow changes although the same types of flow were still present.