The Dynamics of Bi-Directional Exchange Flows: Implications for Morphodynamic Change within Estuaries

An experimental study has been conducted at the CNRS Coriolis Rotating Platform at LEGI, Grenoble, in a trapezoidal cross section channel, to investigate uni and bi-directional exchange flows. Both rotating and non rotating experiments, with a non-erodible and erodible bed layer were considered. Experimental measurements focused on obtaining high-resolution velocity and density fields in different vertical planes spanning the width of the channel using 2D Particle Image Velocimetry, Laser Induced Fluorescence, ADV and micro-conductivity probes in several channel sections. Preliminary results from the study are presented herein and consider the exchange flow dynamics at the interface, with particular focus on the observed cross-channel variations in the counter-flowing water masses and layer thickness. Further analyses are ongoing to improve understanding of the interfacial mixing and entrainment/detrainment processes, along with the bed-morphological changes initiated by interaction mechanisms between the erodible bottom boundary and the uni- or bi-directional exchange flows.