TY - JOUR

T1 - Three-dimensional submerged wall jets and their transition to density flows

T2 - Morphodynamics and implications for the depositional record

AU - Lang, Jörg

AU - Fedele, Juan J.

AU - Hoyal, David C.J.D.

N1 - Funding Information: This study was funded by Leibniz Universit?t Hannover (?Wege in die Forschung? ? postdoc-funding scheme; Grant II-05-2014-05) and the German Research Foundation (DFG; Grant LA 4422/1-1). We are grateful for the support by ExxonMobil Upstream Research Company for providing access to the experimental facility and supplying the consumables for the experiments. J. Winsemann and the members of the ExxonMobil Upstream Research Company?s Process Stratigraphy team are thanked for discussion. Constructive reviews by F. Pohl and an anonymous reviewer are highly appreciated. The editorial team (A. Slootman, M. Cartigny, A. Normandeau, D. Ventra and S. Hubbard) of the Sedimentology special issue is thanked for inviting us to contribute this paper. Open access funding was provided by project DEAL. Funding Information: This study was funded by Leibniz Universität Hannover (‘Wege in die Forschung’ – postdoc‐funding scheme; Grant II‐05‐2014‐05) and the German Research Foundation (DFG; Grant LA 4422/1‐1). We are grateful for the support by ExxonMobil Upstream Research Company for providing access to the experimental facility and supplying the consumables for the experiments. J. Winsemann and the members of the ExxonMobil Upstream Research Company’s Process Stratigraphy team are thanked for discussion. Constructive reviews by F. Pohl and an anonymous reviewer are highly appreciated. The editorial team (A. Slootman, M. Cartigny, A. Normandeau, D. Ventra and S. Hubbard) of the special issue is thanked for inviting us to contribute this paper. Open access funding was provided by project DEAL. Sedimentology

PY - 2021/5/24

Y1 - 2021/5/24

N2 - Jets that expand from an orifice into an ambient water body represent a basic flow model for depositional environments related to expanding flows. Momentum-dominated jets evolve into gravity-dominated density flows. To understand this transition and its sedimentological relevance, three-dimensional tank experiments with submerged wall jets were conducted, systematically varying parameters such as the initial density difference, bed slope, grain size and sediment supply. Bedform successions could be subdivided into those related to the jet and those related to the density flow. Jet deposits included early-stage bedforms, scours and mouth bars. Early-stage bedforms are asymmetrical dunes that spread concentrically from the orifice. Sediment entrainment by eddies from the expanding jets led to the formation of scours and mouth bars. Flows with lesser initial density difference produced more elongate scours. Conversely, scours became deeper for denser incoming flows. Coarser-grained sediment caused the formation of higher and steeper mouth bars and vice versa. The transition from momentum-dominated jets to gravity-dominated density flows occurred approximately at the mouth-bar crest. Hydraulic jumps were absent in the expanding jet regions and at the transitions to density flows. Instead, complex flow patterns and circulations were inferred from the velocity measurements within the scour and at the mouth-bar crests. Bedform trains related to the density flow were controlled by the grain size and sediment supply. Coarse-grained sediment and high supply rates caused strong mouth-bar aggradation and flow splitting, leading to the formation of bedform trains laterally adjacent to the mouth bar. Fine-grained sediment and low supply rates caused the formation of bedform trains downflow of the mouth bar. The symmetrical bedforms deposited by the density flows always displayed an in-phase relationship with the flow, indicating that they were antidunes. The experimental jet deposits resemble successions known from subaqueous ice-contact fans and deep water channel-lobe transition zones.

AB - Jets that expand from an orifice into an ambient water body represent a basic flow model for depositional environments related to expanding flows. Momentum-dominated jets evolve into gravity-dominated density flows. To understand this transition and its sedimentological relevance, three-dimensional tank experiments with submerged wall jets were conducted, systematically varying parameters such as the initial density difference, bed slope, grain size and sediment supply. Bedform successions could be subdivided into those related to the jet and those related to the density flow. Jet deposits included early-stage bedforms, scours and mouth bars. Early-stage bedforms are asymmetrical dunes that spread concentrically from the orifice. Sediment entrainment by eddies from the expanding jets led to the formation of scours and mouth bars. Flows with lesser initial density difference produced more elongate scours. Conversely, scours became deeper for denser incoming flows. Coarser-grained sediment caused the formation of higher and steeper mouth bars and vice versa. The transition from momentum-dominated jets to gravity-dominated density flows occurred approximately at the mouth-bar crest. Hydraulic jumps were absent in the expanding jet regions and at the transitions to density flows. Instead, complex flow patterns and circulations were inferred from the velocity measurements within the scour and at the mouth-bar crests. Bedform trains related to the density flow were controlled by the grain size and sediment supply. Coarse-grained sediment and high supply rates caused strong mouth-bar aggradation and flow splitting, leading to the formation of bedform trains laterally adjacent to the mouth bar. Fine-grained sediment and low supply rates caused the formation of bedform trains downflow of the mouth bar. The symmetrical bedforms deposited by the density flows always displayed an in-phase relationship with the flow, indicating that they were antidunes. The experimental jet deposits resemble successions known from subaqueous ice-contact fans and deep water channel-lobe transition zones.

KW - Channel-lobe transition zone

KW - density flow

KW - hydraulic jump

KW - subaqueous ice-contact fan

KW - supercritical flow

KW - wall jet

UR - http://www.scopus.com/inward/record.url?scp=85104548104&partnerID=8YFLogxK

U2 - 10.1111/sed.12860

DO - 10.1111/sed.12860

M3 - Article

AN - SCOPUS:85104548104

VL - 68

SP - 1297

EP - 1327

JO - SEDIMENTOLOGY

JF - SEDIMENTOLOGY

SN - 0037-0746

IS - 4

ER -