A survey of recent development in helicopter aerodynamics

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A survey of recent development in helicopter aerodynamics

Philippe, J.J. / Roesch, P. / Dequin, A.M. / Cler, A.

Helicopter fuselage aerodynamics will probably remain a subject of experimental investigation for years to come because of serious modelling difficulties associated with strong three-dimensional effects and large regions of separated flow to which the presence of the rotor hub adds further complexity. Flight tests are not very well suited to the detailed analysis of the flow situation and wind tunnel experimentation still remains the most appropriate and widely used method of investigation in spite of certain difficulties associated with the testing of small scale models which are recalled in the paper. Experimental data on fuselage drag is then analyzed and the effect of fuselage and rotor hub wake interference with the stabilizers is discussed. As regards theoretical work, the paper describes the major computational codes developed in the last decade. After a brief description of the different flow conditions encountered over the fuselage, the simple potential flow pannel methods are reviewed, followed by two-dimensional boundary layer methods which are applied along fuselage streamlines to the determination of the flow separation line. We then introduce various wake models based on the vortex sheet singularity concept. A critical analysis of the results predicted by these methods shows the necessity of using three-dimensional boundary layer calculations and more accurate but also more complex representations of the fuselage wake.