Flow Control Downstream of a Backward Facing Step

A simple LEBU-like device aimed at controlling the separated flow field behind a backward facing step, with special attention on its unsteady properties, is described; the device advantage is that it requires very small design modifications and/or complications. Visualizations of the controlled field are presented along with wall hot-wire measurements. The latter measurements provided information about both the mean wall quantities (skin friction) and unsteady properties (wall shear stress fluctuations); RMS and spectra of these fluctuations are presented, showing how the distribution of fluctuation energy is influenced by the presence of the manipulator. In particular, specific positionings of the device allowed to reduce wall unsteadinesses. To summarize the outcomes of the work, although the research is in its early stages, the results presented here prove the viability of this way of controlling separated flows.