Structure and dynamics of a laminar separation bubble near a wing root: towards reconstructing the complete LSB topology on a finite wing

The influence of the wing root junction on laminar separation bubble forming suction surface a semispan NACA 0018 cantilevered from wind tunnel test section wall is studied using flow visualisations, particle image velocimetry and pressure measurements at chord Reynolds number 125 000 an angle attack 6 $^\circ$ . boundary layer upstream turbulent, spanwise extends well beyond thickness. Substantial three-dimensionality seen in flowfield near root, where earlier transition reduction thickness observed. In contrast with tip, length occurs root. Outside affected region, similar to bubbles two-dimensional geometries, displays mild waviness. process away end regions characterised by formation roll-up vortices that are shed nearly manner across span. analysis results shows that, increased level perturbations leads vortex contributes more rapid breakdown. region complemented data Toppings Yarusevych ( J. Fluid Mech. , vol. 929, 2021, A39) tip provide holistic outlook topology dynamics entire finite wing.