Some Tests of the NATO AVT-298 SWiFT Model at Low Reynolds Numbers

Tests were carried out in a university-type atmospheric wind tunnel on a NATO-designed Swept Wing Flow Test (SWiFT) model at incompressible Mach numbers and Reynolds numbers ([Formula: see text]) ranging from [Formula: see text] to [Formula: see text]. The initial purpose was to compare the current results with those obtained in the National Transonic Facility (NTF) to assess the significance of [Formula: see text] on the physics of the flow. Following the excellent agreement in force balance data, the investigation expanded to study the leading-edge vortex (LEV) that impacts the pitch dependence on incidence and the flow unsteadiness after its liftoff from the surface, potentially leading to buffet. Oil flow visualization identified the liftoff location and its effect on pitch, while smoke visualization revealed the unsteadiness of the process. Quantitative analysis using particle image velocimetry (PIV) and hot wire anemometry exposed large periodic oscillations contributing to a turbulence level that is much larger than is known in a typical turbulent boundary layer on the verge of separation. Proper orthogonal decomposition (POD) confirmed the unsteady behavior at incidence angles exceeding vortex liftoff that raised the significance of a convective length scale and Strouhal number on this type of blended-wing–body configuration.