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Scaling and flow dependencies over forward-facing steps

Abstract : In the present paper, the structure of the mean separation bubbles upstream and downstream of a parametric forwardfacing step (Ffs) is experimentally studied over a Reynolds numbers range of Re h = 110670 − 412000, based on the step height and the free stream velocity. An array of 20 pressure sensors located on the front and on the top sides of the step were flush mounted for capturing the wall pressure fluctuations. Classical Piv was used to investigate the flow field topology and to extract key features. The main interest of this study is to discuss about the parameters affecting the reattachment length and the pressure statistics. A detailled analysis and comparison with the literature of the present study permitted to identify the most important flow quantities influencing the overall dynamics. Different sets of data with various Reynolds numbers, heights to boundary layer thicknesses h δ, and constriction ratios C R , have been compared and considered exhaustively. The wall pressures space-time correlations and convection velocities of the large-scale structures downstream the step are highlighted. A focus on the spectral behavior of the unsteady pressure footprint inside the recirculation region of he top side have also been investigated in order deeply understand the unsteady processes described in the litterature. Results demostrate the existance of a convective instability process and a flapping phenomenon of the shear-layer contributing to the separated flow arrangement.
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Submitted on : Thursday, January 27, 2022 - 12:47:48 PM
Last modification on : Tuesday, September 6, 2022 - 10:41:48 AM

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Anthony Graziani, Marc Lippert, David Uystepruyst, Laurent Keirsbulck. Scaling and flow dependencies over forward-facing steps. International Journal of Heat and Fluid Flow, Elsevier, 2017, 67, pp.220-229. ⟨10.1016/j.ijheatfluidflow.2017.08.009⟩. ⟨hal-03545610⟩

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