Excited turbulent flow behind a square rib

The effect of fundamental excitation on the reattaching shear layer developing behind a surface mounted square rib has been discussed. The individual contributions from the random and the coherent part of the turbulent fluctuations are calculated using the pattern recognition approach. Quadrant analysis is used to investigate the turbulent motion details, i.e. ejections, sweep, wallward interaction motions and outward interaction motions of the rib roughened shear layer. In doing so, an interesting and previously unreported behavior about the relationship between the ejection motions and non-Gaussian nature of the flow is observed. The large-scale ejection motions predominant in the outer edge of the shear layer contribute to the non-Gaussian higher order moments. With excitation, the shear layer reattachment moves upstream, and the X-momentum transport is enhanced in the near-wall region. The Reynolds stress correlation profile shows a distinct difference between the redeveloping boundary layer behind the rib and the flat plate boundary layer.