Turbulence characteristics and mixing properties of gravity currents over complex topography

Abstract

Understanding gravity currents developing on complex topography, that involve turbulence and mixing processes on a wide range of spatial and temporal scales, is of importance for estimating near ground fluxes in oceanic and atmospheric circulation. We present experimental results, based on high resolution velocity and density measurements, of constant upstream buoyancy supply gravity currents flowing from a horizontal boundary onto a tangent hyperbolic shaped slope. The mean flow, the turbulence characteristics and mixing properties, the latter expressed in terms of mixing lengths and eddy coefficients, are determined, highlighting their dependency on topography. These mean flow and mixing characteristics are compared with the field measurements in katabatic winds of Charrondière et al. (2022), showing that the mean katabatic flow structure is substantially different from that of the upstream buoyancy supply gravity current. However interestingly, dimensionless mixing lengths and eddy coefficients compare well despite the difference in mean flow structure and a two order of magnitude difference in the Reynolds number.

Gravity currents moving over a sediment bed: suspension criteria and bed forms

“…4(b,c,d) displays the averaged Reynolds stresses ⟨u ′ w ′ ⟩, ⟨u ′ u ′ ⟩ and ⟨w ′ w ′ ⟩, respectively from the zoomed view. The vertical profiles of ⟨w ′ w ′ ⟩ and ⟨u ′ u ′ ⟩ appear different from those of a turbulent wall jet [38]. Near the wall…”

Field Observations Reveal How Plunging Mixing and Sediment Resuspension Affect the Pathway of a Dense River Inflow Into a Deep Stratified Lake

“…In an underflow of constant width, B (this case, for flow into a submerged canyon, is considered in the present paper), this amounts to $$$d{Q}_{u}/dx={E}_{w}\text{BU}$$$ and an underflow discharge that increases linearly. Laboratory and field experiments indicate that E w decreases with increasing Ri (Ashida & Egashira, 1975; Hebbert et al., 1979; Maggi et al., 2023; Parker et al., 1987). Wells and Wettlaufer (2005) and Wells and Dorrell (2021) summarized entrainment data from laboratory and field experiments and concluded that mixing in the underflow region is small and consistent with the proposed estimates of E w .…”

Effect of stratification on the propagation of a cylindrical gravity current

“…Planar release gravity currents in stratified (Maxworthy et al 2002;Ungarish & Huppert 2002;Birman et al 2007b;Longo et al 2016;Chiapponi et al 2018;Lam et al 2018b;la Forgia et al 2020;Ottolenghi et al 2020;Dai et al 2021;Zahtila et al 2024), and unstratified ambients (Rottman & Simpson 1983;Shin, Dalziel & Linden 2004;La Rocca et al 2008;Dai 2015;Pelmard, Norris & Friedrich 2018;Dai & Huang 2020;De Falco, Adduce & Maggi 2021;Maggi, Adduce & Negretti 2022, 2023aMaggi et al 2023b), as well as cylindrical release gravity currents in unstratified environment have been widely studied experimentally and numerically (Cantero et al 2007a,b;Zgheib, Bonometti & Balachandar 2014, 2015aDai & Huang 2016). However, experimental and numerical studies on stratified gravity currents with the cylindrical release are limited, and therefore we are interested in cylindrical gravity currents propagating into a linearly stratified ambient.…”

“…2008; Dai 2015; Pelmard, Norris & Friedrich 2018; Dai & Huang 2020; De Falco, Adduce & Maggi 2021; Maggi, Adduce & Negretti 2022, 2023 a ; Maggi et al. 2023 b ), as well as cylindrical release gravity currents in unstratified environment have been widely studied experimentally and numerically (Cantero et al. 2007 a , b ; Zgheib, Bonometti & Balachandar 2014, 2015 a ; Dai & Huang 2016).…”