09/11/17 - Antoine Martin
Gravity currents (GC) are key processes that affect atmospheric, ocean and coastal circulation. Modeling of gravity currents mainly rely on classical studies made on horizontal or uniform sloping smooth bottom. Most of the gravity currents in nature occur over rough and/or mobile terrain.
In the past decade, a large effort was employed to find a better parametrization of entrainment in density currents but only the entrainment at the sheared interface between the current and the ambient fluid has been considered. The effect of complex terrain has often been neglected, whereas it acts as enhanced bottom friction and can contribute to the density variations through the suspension of sediment particles within the current. While laboratory experiments have successfully revealed global flow behavior, local mixing and entrainment of bottom sediments are still challenging tasks. Experiments are needed to correctly parametrize entrainment and turbulent fluxes under more complex bottom conditions.
During this presentation, the ongoing development of technique to measure simultaneously velocity field and suspended sediment concentration using (PIV) particles of different sizes is presented. Then a preliminary quantification of sediments entrainment and time-average GC characteristics is presented.