Crosswind Aerodynamic Analysis Using Quasi 3D Ducts

In this paper, we address the aerodynamics of the nacelle subjected to severe crosswinds. A series of numerical simulations are carried out on a Quasi 3D duct which has been extracted from a 3D axisymmetric nacelle. The operating characteristics of the Q3D duct, total pressure profiles at fan-face and isentropic Mach number distributions over the intake lip, are demonstrated to be in encouraging agreement with the experiments. Some of the strategies to predict two different types of hysteresis which are either observed at low mass flow rates or at lower operating pressures within the duct (and hence at low Reynolds numbers) are discussed. Contrasting trends in the turbulent kinetic energy predictions of k-ω and γ-Reθ models at low system pressures are observed, which indicate that the boundary layers on the windward side of the intake lip are transitional. Finally, we discuss the possibilities of improving the off-design nacelle performance using active plasma flow control. While a low-speed separation can be eliminated using plasma actuator, controlling high speed separation remains a challenging task.