TR-PIV Comparative Study of Vortical Systems Behind Leading-Edge Vortex Generators and Large Eddy Breakup Devices

Targeted modifications of properties of turbulent shear flows under the influence of: a) longitudinal Counter -Rotating Vortex Paired systems (CRVPs) generated by leading -edge tubercles on lifting surfaces, and b) multi -element devices for disrupting naturally formed large vortices in the outer region of the turbulent boundary layer , also called Large Eddy Breakup devices (LEBU) were studied using PIV measurement technology. An extensive parametric analysis of the influence of the geometric characteristics o f leading -edge tubercles, primarily their length, on the anisotropy of flow properties in the wake region immediately behind the tubercle and in the midplane between pairs of adjacent tubercles was conducted. It was shown that changes in leading -edge geometry have a significant impact on the wake parameters, and even tubercles as short as 2% of the wing model chord intensify the 3D structure of the shear flow, thereby increasing its stability against separation, while virtually maintaining aerodynamic drag at low angles of attack typical of cruise flight. As a physically interesting alternative, the properties of the turbulent boundary layer behind a structure of thin LEBU containing one to five blades are compared. The effects of both the influence of a single blade and the combined effect of the entire set of blades on the formation of the shear flow structure behind the multi -element LEBU system are demonstrated.