Acoustic Doppler velocimetry measurements of flow over a backward-facing step

The application of the acoustic Doppler velocimetry (ADV) technique to backward-facing step flows is very scarce in the literature. This work aims at investigating the applicability of the ADV technique to flows over a backward-facing step, at various Reynolds numbers to capture different flow regimes, and to provide reliable data which can be used to validate numerical models. The ADV $Vectrino+$ was used in a laboratory flume and a customized numerical code was developed, which implements a methodology to post-process the ADV records. The normalized mean streamwise velocity and turbulence profiles were compared with classical results measured using a laser Doppler velocimeter and a high correlation was found. The ADV measurements showed accurate results regarding the streamwise velocity profiles, the turbulent shear stress and the reattachment length. Thus, ADVs can be used to characterize separated flows with good accuracy providing that an adequate post-processing is made to the acquired data. The errors obtained by the uncertainty analysis were relatively low, in general.