Validation Of A Turbulent Boundary Layer Method For Fuselages Of Helicopters

Abstract

The flow field over a helicopter is exceedingly complex due to various aerodynamic phenomena occurring simultaneously. The precise calculation of the boundary layer in three-dimensional, viscous flow is an old und repeatedly sought-after goal in helicopter aerodynamics. Panel methods calculate frictionless flows including interference effects through potential flow assumption with good accuracy. Since viscous drag cannot be predicted with panel methods alone, the panel methods have to be coupled with a boundary layer method. This paper describes the newly implemented Truckenbrodt's boundary layer method for helicopter fuselages in DLR's unsteady 3D panel and free-wake code UPM, with the aim of improving friction forces and flow separation prediction accuracy. The focus of this paper is to validate the implementation with experimental wind tunnel results of the DLR-internal project Fast Rescue. As an application example, UPM is used to simulate the aerodynamics of a medical personnel deployment vehicle. The results show that the boundary layer method is able to provide reasonable force and moment coefficients and identify flow separation regions.