The influence of scale,slope and channel geometry on the flow dynamics of submarine channels |
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| Institution: | 1. Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK;2. Departments of Geology and Geography, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA;1. University of Aberdeen, Department of Geology and Petroleum Geology, Aberdeen, AB24 3UE, UK;2. Statoil ASA, 4035 Stavanger, Norway;3. Statoil ASA, NO 1364 Oslo, Norway;4. Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche, Bologna, Italy;5. Deep Marine Ltd, 9 North Square, Aberdeen AB11 5DX, Scotland, United Kingdom;1. State Key Laboratory of Petroleum Resources and Prospecting (China University of Petroleum, Beijing), Beijing 102249, China;2. College of Geosciences, China University of Petroleum, Beijing 102249, China;3. Ocean college, Zhejiang University, Hangzhou, Zhejiang Province, 310058, China;4. China National Offshore Oil Corporation Ltd (CNOOC), Beijing 100010, China;5. CNOOC Research Center, Beijing 100027, China;6. Petroleum Exploration & Exploration Co., Ltd. Sinochem, Beijing 100031, China;1. South African Institute for Aquatic Biodiversity, Durban 4001, South Africa;2. Geological Sciences, University of KwaZulu-Natal, Durban 4001, South Africa;3. Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany;4. University of Bremen, Department of Geosciences, Klagenfurter Strasse 4, 28359 Bremen, Germany;1. Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, 572000, China;2. Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519080, China;3. University of Chinese Academy of Sciences, Beijing, 100049, China;4. State Key Laboratory of Natural Gas Hydrate; CNOOC Research Institute Co. Ltd., Beijing, 100027, China |
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| Abstract: | Submarine channels are major morphological features of the sea floor and are important in the transport of sediment to the deep ocean. Although much is known concerning the large-scale distribution of sediment within and surrounding submarine channels, there is little understanding of the fluid dynamic processes that control this sedimentation. Direct measurement of flow velocities and concentrations has proved to be extremely difficult within submarine channels, with the resultant paucity of direct observations making physical laboratory modelling a critical technique for examining the processes that operate in, and control, submarine channel development.Recent experimental and numerical studies have proposed a new model of secondary circulation within submarine channel bends, characterised by a reversal in the orientation of the secondary circulation cell relative to that found in meandering rivers. This new paradigm for submarine channels thus predicts basal flow from the inside to the outside of the bend at a bend apex, with an upper return flow directed towards the inner bend. The reversal in orientation of the secondary flow cell has been linked to the vertical distribution of downstream velocity and associated changes in centrifugal and pressure gradient forces. However, previous work has additionally proposed that shearing of the within-channel flow by overbank flow may also generate secondary flow reversal.This study assesses the applicability of the proposed submarine bend flow model against a range of key channel parameters. We demonstrate that the sense of secondary circulation is the same for all experimental conditions, strongly supporting the new model of secondary flow in submarine channels. Furthermore, investigation of overbank shear induced secondary circulation confirms for the first time that this mechanism can occur, and identifies the channel styles most likely to exhibit this effect. Such shear-induced circulation is, however, shown to be a secondary mechanism, with the vertical distribution of downstream velocity the principal mechanism. In certain channel configurations, the two mechanisms may act to augment one another. |
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