Unsteady flow around helicopter rotor blade sections in forward flight

The aerodynamic performance of aerofoils performing unsteady motions is imp ortant for the design of helicopter rotors. In this respect the study of ae rofoils undergoing in-plane oscillations (translation along the horizontal axis) provides useful insight into the flow physics associated with the adv ancing blade in forward flight. In this paper a numerical method is develop ed in which the unsteady thin layer Navier-Stokes equations an solved for a erofoils performing rigid body motions. The method has been applied to the calculation of the flowfield around a NACA 0012 aerofoil performing in-plan e motions representative of high-speed forward flight. Comparison of comput ed pressure data with experimental measurements is generally found to be go od. The quantitative differences observed between computations and experime nt are thought to have arisen mainly as a consequence of the low aspect rat io of the model rotor employed in the windtunnel tests.