AN ASSESSMENT TO THE DESIGN OF TAIL BOOM STRAKES BY CFD-TECHNIQUES

Single-rotor helicopters are exposed to asymmetric flow over the tail boom that causes an aerodynamic force in the sideward direction. Unfortunately, this side force is in an opposite direction to the tail rotor thrust and hence reduces the pedal margin. This problem could be overcome by a proper design of spoiler/strake on the suction side of the tail boom. Design of tail boom strakes is commonly done via intensive wind tunnel testing. In this paper, the author introduces an assessment to a less-costly and more-convenient alternative based upon one of the commercial CFD software in the market. A tail boom model of circular cross-section that was previously tested in the subsonic wind tunnel facility at NASA Langley has been adopted for this purpose. The Navier-Stokes equations with k-e turbulent model are solved over unstructured grid of triangular elements. The computational and experimental measurements of the force coefficients for the model without strakes were found in good agreement for a wide range of flow incidences. For the model with two strakes, this agreement was found limited to only a range of incidences of ±20°.