We tested a radically different approach to predict turbulent flow in reservoirs

Shallow reservoirs are often used in hydraulic engineering as sediment traps or storage basins.

Previous studies have found different flow patterns in such reservoirs, depending on the shape of the reservoir (jet flowing straight from the inlet to the outlet, or jet reattachment to the sidewall of the reservoir).
an empirical geometric relation describing the switch between these two different
flow patterns. In this study, we demonstrate that this switch in flow pattern coincides with a maximization of
energy dissipation in the shear layer between the main jet and the recirculation zones. To show this we described
the power received from the jet by the recirculation zone as the product of a fluid-fluid friction coefficient and the
square of the velocity difference times the shear velocity of the recirculation zone. This power is balanced by the
bottom friction of the recirculation zone. Energy dissipation in the shear layer is then determined as the difference
between the power performed by the jet and the power received by the recirculation zone.
In this setup, energy dissipation is maximized by optimizing the friction coefficient. We show that for short
reservoir lengths, energy dissipation is higher in the case of a symmetric flow pattern, while for longer reservoir
the energy dissipation is higher for asymmetric flow patterns. The simulated switch between the two flow patterns
appears to be very close to the empirical relation. This suggests that the flow pattern adapts in order to maximize
energy dissipation between the jet and recirculation zones.
The strength of this approach lies in the fact that no detailed knowledge of small scale processes is needed, while
large scale structure formation can still be predicted