density currents; concentration measurements; averaging techniques; velocity measurementes; steady-state
VenuleoSara (2020), Continuously-fed density currents over impermeable and porous substrates
, EPFL, Lausanne, Switzerland.
Venuleo Sara, Pokrajac Dubravka, Schleiss Anton J., Franca Mário J. (2019), Continuously-fed gravity currents propagating over a finite porous substrate, in Physics of Fluids
, 31(12), 126601-126601.
VenuleoSara, SchleissAnton (2019), Experimental results of gravity currents travelling over a fissured bed, in E-proceedings of the 38th IAHR World Congress
, Panama City, PanamaIAHR, Madrid, Spain.
NomuraShun, SakaguchiHide, De CesareGiovanni, VenuleoSara, HitomiJumpei, MuraiYuichi, TasakaYuji (2018), Distinctive features of horizontal and vertical velocity profiles in turbidity and saline density currents, in Proc. of the 5th IAHR Europe Congress on New Challenges in Hydraulic Research and Engineering
, Trento, ItaliaIAHR, Madrid, Spain.
Pokrajac Dubravka, Venuleo Sara, Franca Mário J. (2017), Depth-averaged momentum equation for gravity currents with varying density: coefficient in pressure term, in Journal of Hydraulic Research
, 56(3), 424-430.
Density or gravity currents are geophysical flows driven by density differences between two contacting fluids with pertinence to engineering sciences. The release of pollutants into rivers, oil spillage in the ocean and desalination plant out flows are examples of anthropogenic density currents with negative environmental impacts. The loss of storage in reservoirs caused by the deposition of sediments transported by turbidity currents, and salinity intrusions like those verifed in the Rhine-Meuse delta (south Holland) when barrier gates operate, are examples of actual concerns to engineers and scientists. Density currents play also an ecological role in the transport of nutrients and re-oxygenation of water bodies.Although deriving typically from transitory processes, density currents found in nature may have a duration compatible with the assumption of a steady-state process after the passage of the front and a transitional region. More specifically, the time-scale of the development of density currents in nature is typically long enough to verify steadiness of temporal statistics before the current dumping and eventual extinguishing. Examples of steady (or quasi-steady) state currents found in nature are the saline under-flow from Mediterranean sea to the Atlantic ocean observed in the Gibraltar straight and the turbidity current observed when the river Rhone flows into lake Geneva.A proper understanding of the physical mechanisms intrinsic to density currents is the basis to produce adequate preventing and mitigating measures against their negative effects, as well as to understand their implications in the ecological processes in natural water bodies. Most of the research efforts in gravity currents concerns flows developing over smooth beds, few contributions having studied the effect of bed roughness in their dynamics. Moreover, developments on the mathematical formulation of bottom density currents are still needed in order to account for the presence of spatial and temporal varying lower and upper boundaries, with appropriate physical-meaningful terms.This work aims at characterizing experimentally the structure of the flow of turbulent steady-state bottom density currents, to assess the effect of bed roughness and slope on these, and to provide a new theoretical framework for density currents ensuing from averaging techniques recently applied to the description of other environmental flows. A theoretically-derived and empirically-supported conceptual model for dispersive-type fluxes in the lower and upper current boundaries will allow characterizing transfer processes and flow resistance.A research program is proposed where developments in the basic transport equations are complemented with laboratory work, to provide the first supporting empirical evidence. The proposed experimental program includes instantaneous velocities and concentration measurements on a continuously fed density current. Empirical data will be treated with upscaling techniques, where spatial and temporal intermittency is considered, allowing an analysis of the hydrodynamics variables present in the basic hydrodynamic equations and testing the envisaged theoretical framework.