A wake-triggered double-secondary-vortex topology over a multi-element airfoil: A sensitized Reynolds stress model study

The flow over a 30P30N multi-element airfoil at a Reynolds number of Rec = 1.83 × 104 and an angle of incidence of α = 4° is investigated computationally by employing an eddy-resolving Reynolds stress model within the time accurate unsteady Reynolds-averaged Navier–Stokes framework. This scale-resolving model follows the scale-adaptive simulation concept and is capable of providing a reliable three-dimensional fluctuating flow field. The wake-triggered double-secondary vortices topology, reported in experiments but rarely discussed in numerical simulations, is successfully identified in the boundary layer of the main element. The downstream three-dimensional evolution of these double-secondary vortices and the related wake-induced bypass transition can be comprehensively mapped with the aid of the three-dimensional velocity databases obtained computationally. It is found, among other issues, that the specific topology of the wake-triggered double-secondary vortices is responsible for the unsteady aerodynamic lift.