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Entrainment in lock-release gravity currents propagating up a slope
Published in Wim Uijttewaal, Mário J. Franca, Daniel Valero, Victor Chavarrias, Clàudia Ylla Arbós, Ralph Schielen, Alessandra Crosato, River Flow 2020, 2020
M.C. De Falco, L. Ottolenghi, C. Adduce
Gravity currents are density-driven flows generated by a density difference between two fluids. This difference can be due to gradients of temperature, salinity or particles in suspension. These currents in nature generally develop over complex boundaries. For example, dense flows can interact with an upslope, as the salt wedges flowing up the riverbed and travelling upstream, along the channel’s bottom, for long distances. There, the circulation within the channel is strongly affected by the balance between the fresh water discharge, the tidal current of seawater and the inclination of the bottom riverbed. In addition, when internal solitary waves break at the continental shelf, upsloping gravity currents can occur (La Forgia et al. 2018a, b) and have an effect on the sediment transport (La Forgia et al. 2019,2020).
Experiment Execution
Published in Marian (Editor-in-Chief) Muste, Dennis A. Lyn, David M. Admiraal, Robert Ettema, Vladimir Nikora, Marcelo H. Garcia, Experimental Hydraulics: Methods, Instrumentation, Data Processing and Management, 2017
Marian (Editor-in-Chief) Muste, Dennis A. Lyn, David M. Admiraal, Robert Ettema, Vladimir Nikora, Marcelo H. Garcia
Gravity currents, also called density or buoyancy currents, are buoyancy-driven flows moving as a result of density differences primarily in the horizontal direction. The density difference between the involved fluids can be caused by temperature or by dissolved (salinity) or suspended material (turbidity currents, snow avalanches). Turbidity currents are a special type of gravity current with material exchange between current and bed, whereas density currents are characterized by no or negligible material exchange. Reviews of gravity currents have been given by Simpson (1997), Meiburg and Kneller (2010) and Ungarish (2010).
Depth-averaged momentum equation for gravity currents with varying density: coefficient in pressure term
Published in Journal of Hydraulic Research, 2018
Dubravka Pokrajac, Sara Venuleo, Mário J. Franca
Gravity currents are geophysical flows driven by density difference between two fluids caused by gradients in temperature, dissolved substances or particles in suspension. Velocity and density profiles typical for gravity currents are often non-uniform in the bed-normal direction, as reported by several experimental and numerical studies (Altinakar et al., 1996; Kneller et al., 1999; Parker et al., 1987; Sequeiros et al., 2010; Stagnaro & Bolla, 2014; Ottolenghi et al., 2016a, 2016b). Traditionally the depth-varying shape of the profiles is taken into account through multiplicative factors, often called shape factors, which appear in the shallow-water layer-integrated equations (SWEs) (Chu et al., 1979; Hogg & Pritchard, 2004; Parker et al., 1987; Sequeiros et al., 2010). In this note we refer to these multiplicative factors simply as coefficients. Particular coefficients are named after the SWE term where they appear, e.g. momentum coefficient and pressure coefficient. A coefficient in an SWE term is defined as the ratio of the value of the term obtained by integration over the current depth and the same term obtained from depth-averaged quantities.
Unconfined lock-exchange gravity currents with variable lock width: laboratory experiments and shallow-water simulations
Published in Journal of Hydraulic Research, 2018
Valentina Lombardi, Claudia Adduce, Michele La Rocca
Recently the lattice Boltzmann method has been successfully employed to solve multilayer shallow-water model for the simulation of lock-release gravity currents (La Rocca, Adduce, Lombardi, Sciortino, & Hinkelmann, 2012; La Rocca, Prestininzi, Adduce, Sciortino, & Hinkelmann, 2013; Prestininzi, Sciortino, & La Rocca, 2013, 2014). Most of the models used in literature to reproduce gravity currents are based on the shallow-water approximation. Indeed, as a natural gravity current mainly develops on the horizontal plane, the shallow-water theory is appropriate in reproducing its dynamics (see Adduce, Sciortino, & Proietti, 2012; La Rocca et al., 2008; Lombardi et al., 2015; Rottmann & Simpson, 1983; Shin, Dalziel, & Linden, 1999; Ungarish, 2009).
Effect of an obstacle on the depositional behaviour of turbidity currents
Published in Journal of Hydraulic Research, 2019
Ahmadreza Farizan, Sina Yaghoubi, Bahar Firoozabadi, Hossein Afshin
Density currents are generated due to the density difference between two fluids. These currents are also called gravity currents because the gravitational force drives the flow. Many gravity currents are formed in nature. Sea-breeze fronts, thunderstorm outflows, snow avalanches, pyroclastic flows and turbidity currents are examples of natural gravity currents (Simpson, 1982). Furthermore, these currents may arise from various man-made disasters such as the propagation of oil impurities in deep waters and accidental emissions of hazardous substances at chemical plants (Ermanyuk & Gavrilov, 2005a). Turbidity currents are density flows in which the density difference is due to the suspended sediments. Particle concentrations are often low in turbidity currents so that the fluid turbulence (rather than the particle–particle interaction) holds the particles in suspension (Meiburg & Kneller, 2010; Middleton, 1993). These currents are much more complicated than other gravity currents because the particle concentration changes with time and position along the flow (Bonnecaze, Huppert, & Lister, 1993), and therefore affects the structure and dynamics of the current. Turbidity currents can travel along the bed at high velocities (De Cesare, Schleiss, & Hermann, 2001) and consequently they are responsible for damage to submarine cables and seafloor equipment, erosion of underwater canyons and formation of tsunamis (Meiburg & Kneller, 2010; Simpson, 1982). In addition, deposits of turbidity currents may be hydrocarbon-rich and thus they can form good hydrocarbon reservoirs over long times (Mulder & Alexander, 2001). Therefore, accurate prediction of changes in deposit thickness is highly important.