Statistical properties of attached and separated wall flows

The aim of this work is study study of the flow field by incompressible turbulent boundary layers overflowing a forwardfacing step (FFS). Preliminary to the study of the FFS flow, our attention is oriented to the characterization of incoming boundary layer at high Reynolds numbers (Reθ = 3940 and 7257). The study of the separated flow is focussed on the statistical characterization of the pressure fluctuations that are measured upstream and downstream of an instrumented FFS step model. Two-dimensional velocity fields are measured as well close to the step via 2D particle image velocimetry (PIV). The wall pressure statistics are analyzed in terms of several indicators, demonstrating that the most relevant flow structure is the unsteady recirculation bubble formed at the reattachment region downstream of the step. The simultaneous measurement of time-resolved PIV fields and wall pressure signals enabled us to compute the pressure/velocity cross correlations in the region downstream of the step and substantiated the relevant role played by the recirculation bubble.