Mean Velocities and Reynolds Stresses in the Juncture Flow and in the Shear Layer Downstream of an Appendage

Experimental measurements were carried out in an incompressible 3-dimensional turbulent shear layer at locations in the corner near the trailing edge and also downstream of an appendage mounted perpendicular to a flat plate. A fully developed turbulent boundary layer was growing on the plate. The symmetrical appendage had an elliptical nose and was aligned with the flow. Thickness of the boundary layer as it approached the appendage leading edge was 76 mm or 1.07 times the maximum thickness of the appendage. Shear layer thickness was small compared to the appendage span. As the oncoming boundary layer passed around the appendage, a strong secondary flow was formed which was dominated by a pair of streamwise vortices trailing downstream in the corner and into the shear layer behind the appendage. This secondary flow had major effect in redistributing both the mean flow and turbulence quantities throughout the shear layer, and this effect persisted to a significant degree up to at least 3 chord lengths behind the appendage leading edge. At the appendage trailing edge, the core of the vortex-like secondary flow was located at 8% of the shear layer thickness above the plate and 0.40 appendage thickness away from the trailing edge itself. At 3 chord lengths downstream of the appendage leading edge the core had moved away from the plate a distance corresponding to about 29% of the local shear layer thickness while simultaneously moving outboard to a distance of 0.80 appendage thickness from the plane of symmetry.