Influence of Slip Length on Turbulence Propagation Along the Chord of NACA 64-618 Airfoil

This study investigates the effect of surface slip and angle of attack (α) on the aerodynamic characteristics and vortex dynamics around a NACA 64-618 airfoil at a Reynolds number of 1.3×106 using detached eddy simulation. A slip boundary condition, modeled to mimic a superhydrophobic coating was implemented on the walls of the airfoil to assess its impact on flow dynamics using a user-defined function. One slip length (Ls = 100μm) was examined at α = 0°, 12° and then compared to results from the no-slip condition at that same α. Major aerodynamic features and two-dimensional flow topology were investigated using qualitative and quantitative tools. At α = 0°, surface slip had minimal influence on the instantaneous and mean flow fields. However, at α = 12°, shear-layer instability was enhanced causing an early vortex rollup and greater acceleration in the wake lowering downstream velocity deficit. Surface slip also reduced pressure and skin friction drag by delaying flow transition and reducing the recirculation bubble. Frequency analysis conducted on the instantaneous velocities in the wake region revealed the migration of dominant frequencies to lower frequency range for the slip case.