Evolution of Wall-Bound Streamwise Vortices Formed by a Spanwise Array of Surface Jets in a Turbulent Boundary Layer

The interactions of spanwise arrays of 3-D surface wall jets with the inner layer of a flat plate turbulent boundary layer are investigated in wind tunnel experiments. Each wall jets issues out of spanwise-rectangular embedded orifice that can be yawed relative to the free stream and the jet adheres to the surface by a Coanda-like effect along the downstream edge of the orifice and remains within the wall layer over 100 equivalent orifice diameters. While the evolution of a single jet varies significantly with its yaw angle ( = 0 and 60o are compared) spanwise arrays of adjacent straight and yawed jets can effect reasonably uniform distributions of near-wall gain in streamwise momentum albeit by different mechanisms and at different downstream distances from the jet orifices. While the momentum gain by each straight rectangular jet remains very close to the surface, the gain effected by the yawed jets spreads more in the cross-stream direction, reaching an asymptotic level of about 50% of the momentum deficit of the base boundary layer flow. Another characteristic element of the yawed jet array is that its evolution can be tailored by the interactions of the jets within the array with the leading and trailing jets (relative to the free stream direction) at the array’s spanwise edges.