Flow field in shallow reservoir with varying inlet and outlet position

Shallow reservoirs are used for multiple purposes, such as storm water retention and trapping of sediments. Reliable predictions of the flow fields are necessary to inform the design and operation of these structures. Using numerical simulations, we performed a systematic analysis of the influence of the location of the inlet and outlet on the flow fields developing in rectangular shallow reservoirs of various sizes. Depending on the relative location of the inlet and outlet with respect to the reservoir centreline, contrasting flow patterns are obtained, involving either no flow reattachment, or a jet reattached on either of the reservoir sidewalls. The results reveal also the occurrence of bi-stable flow configurations, i.e. different steady state flow fields are reached depending on the flow history. This is of high relevance for the design of shallow reservoirs as such configurations should certainly be avoided to achieve a robust hydraulic sizing of the reservoir.