Unsteady aerodynamics analysis and modelling of a Slingsby Firefly aircraft: Detached-Eddy Simulation model and flight test validation

This paper presents unsteady stall characteristics of a Slingsby T67M260 Fire y light aircraft from both a computational uid dynamics (CFD) half model and ight tests. Initial results from the steady CFD, based on a RANS k . ! SST turbulence model, established the critical angle of attack of the stall to be stall = 16 , with a maximum lift coe cient of CLmax = 1.2. Comparisons with straight and level ight test data were comparable up to = 12 { 14 , with the increasing deviation at higher attributed to the e ect of the propeller slipstream under these ight conditions. The RANS CFD model was then extended to an unsteady Detached-Eddy Simulation (DES) model for three angles of attack at pre-stall and stall condition ( = 14 , 16 , 18 ), with analysis of the vortex shedding frequency. Further comparisons were then made with ight test data taken using on-board accelerometers and wing tuft surface ow visualization, at a stalled condition at equivalent . These unsteady CFD data established a dominant shedding frequency ranging from 11.7 Hz { 8.74 Hz with increasing and a Strouhal number based on wing chord of St = 0.11, which when compared to flight test accelerometer spectra matched within 2.9% of the measured frequency