Turbulent junction flow with an upstream ribbed surface

Results of experimental investigations of the effects of an upstream longitudinal triangular ribbed surface on a turbulent junction flow and downstream wake are presented. The ribbed plate was placed right upstream of the wing on the flat plate surface, covering a 10 × 38 cm2 area. The junction flow was developed using a NACA0012 airfoil mounted normal to a flat plate downstream of its leading edge. The experiments were carried out at a free stream mean velocity of 31 m/s. which corresponds to a unit Reynolds number of 1.8 × 106 and the airfoil chord length Reynolds number of 5.4 × 105. Measurements were carried out at four control planes of 50%, 100%, 133%, and 166% of the wing chord length. Results show that the riblets displace the location of the horseshoe vortex away from the corner and reduce its strength. There are significant reductions in mean streamwise circulation downstream at 133% and 166% planes.