Transition from deep to shallow water layer: formation of vortex dipoles

In this paper we study the transition from a deep to a shallow water layer and the formation of quasi-two-dimensional vortex dynamics. Vortices are experimentally generated by a circular horizontal turbulent pulsed jet. The dimensional analysis gives two relevant dimensionless parameters: the jet Reynolds number $Re$ and a number $C$ which characterizes the vertical confinement. They are respectively defined by $Re=Q/\nu$ and $C=(Q/H^2)t_\text{inj}$ ($H$ is the water depth, $\nu$ is the kinematical viscosity, $Q$ the injected momentum flux and $t_\text{inj}$ the injection duration). Experimental results show a strong influence of $C$ on the flow: when $C2$ we observe the formation of large vortex dipoles. However these dipoles are not strictly two-dimensional because of the presence of a vertical circulation in the front of the dipole. Results are independent of the jet Reynolds number in the range $1000< Re< 1800$. In addition, a comparison between experimental shallow water dipoles and theoretical model is exposed