Slat cove dynamics of multi-element airfoil at low Reynolds number

The flow around the slat cove of a two-dimensional 30P30N multi-element airfoil is investigated with time-resolved particle image velocimetry (TR-PIV) at low Reynolds number (Re_c = 2.41 × 10⁴ and 4.61 × 10⁴). The effects of angle of attack (α = 8°, 12°, and 16°) on the mean flow characteristics and vortex dynamics are discussed. The size of the recirculation within the slat cove and the intensity of the shed vortices originating from the slat cusp shear layer are found to generally decrease as the angle of attack increases. The joint time-frequency analyses show that disturbances of different frequencies exist in the slat cusp shear layer and they trigger the different vortex shedding patterns of the slat cusp shear layer. The self-sustained oscillation within the slat cove, normally observed at high Reynolds number (Re_c ~ 10⁶), is proved to be responsible for the disturbances of different frequencies and the related vortex dynamics in the current study.