Experimental investigation of turbulent boundary layer developing along a streamwise external corner (chine)

Turbulent viscous fluid flow is always accompanied by a secondary flow if the flow is not exactly two-dimensional or exactly axisymmetric. The classic example is duct flow, where counter-rotating pairs of vortices appear in each corner, distorting the isoaxialvelocity contours. The present investigation of the turbulent boundary-layer development along a streamwise external corner (chine) also shows distortion of the isoaxialvelocity contours which predicts the presence of a pair of counter-rotating vortices. These vortices or secondary flow are induced by inequality of Reynolds stresses around the corner. The direct effect of this corner flow is to increase the drag force. A series of experimental investigations at the University of Melbourne provided, in qualitative terms, the general behaviour expected from this class of flow as revealed by Elder [J. Fluid Mech. 9 (1960) 133] and Xu and Pollard [Phys. Fluids 13 (2001) 3321]. This flow is also expected to exhibit symmetry about the corner bisector. Our measurements indicate quasi-symmetry about the bisector all along the corner