Studies on Tailplane Stall for a Generic Transport Aircraft Configuration

Abstract

A generic wind tunnel model for tailplane stall investigations was designed to establish an experimental database for code validation. The configuration is numerically optimised to obtain large Reynolds numbers at the horizontal tailplane in a wind tunnel of limited size. It consists of a fuselage, a detachable horizontal stabiliser and a tip-truncated wing, that mounts the model at the turntables of the closed test section. Fuselage and wing are used to create representative downwash conditions in the tailplane region inside the wind tunnel, compared to free-flight. The tests were conducted at a freestream Mach number of 0.16 and at a Reynolds number based upon the mean tailplane chord of 0.72 • 10 6. Tailplane stall with natural and fixed transition is visualised by tufts and oil-flow. In case of natural transition, pressure measurements and Particle Image Velocimetry in the area of turbulent trailing-edge separation provide qualitative data for the validation of numerical simulation approaches. First numerical simulations, using an unstructured Reynolds-averaged Navier Stokes Code, are in good agreement with the experiments. They show a separation of the boundary layer starting at the trailing edge with high crossflow velocities at the outer tailplane. Depending on the boundary-layer transition, the stall occurs abruptly for natural transition, initialised by a burst of a laminar separation bubble, or gradually for fixed transition. A deflected elevator shifts flow separation towards lower incidence angles of the tailplane without changing the process of flow separation.

DES of a Slingsby Firefly Aircraft: Unsteady Flow Feature Extraction Using POD and HODMD

“…Aircraft design is an evolving area and with the availability of advanced numerical techniques such as finite element methods and computational fluid dynamics (CFD), it is now possible to do an initial detailed design virtually (Raymer 1999;Okonkwo and Smith 2016;Rizzi et al 2010). A challenging area of any design is the prediction of aerodynamic coefficients during and beyond aircraft stall (Ciliberti et al 2017;Lutz et al 2015;Grote and Radespiel 2006;Teng et al 2015;Lutz et al 2016;Teng et al 2016). More specifically, the pitching moment and lift and drag coefficients have complex characteristics (Phillips 2010), which at high angles of attack may change significantly post-stall, in some cases leading to an autorotation and the development of a spin (Rao and Go 2019;Bennett and Lawson 2018).…”