A horeshoe root vortex secondary flow forms at the junction of a flat plate and an appendage, creating a three dimensional, separated flow. Flow visualizations, pressure measurements on the flat plate, and three dimensional mean an fluctuating velocity measurements were made for two appendage shapes at zero angle of attack with a turbulent incoming boundary layer. The radius of curvature of the leading edge affects the strength of the secondary vortex flow. The vorticity is close to the wall, on the order of the momentum thickness of the incoming boundary layer, and has a flattened shape. The vortex breaks down and the vorticity is conserved as shear layers alongside of and in the wake of the appendage. Keywords: Separated flow; Turbulence; Three dimensional flow; Flow visualization; Hot film measurements.