Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary
Abstract Understanding coastal plane jets which occur when a body of water discharges into an ocean or a lake through a channel or outlet is important, since they play a significant role in sediment, nutrient, and pollutant exchange. This study investigates the nearfield of initially shallow, neutra...
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| Format: | Article |
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Wiley
2024-04-01
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| Series: | Water Resources Research |
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| Online Access: | https://doi.org/10.1029/2023WR034826 |
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| author | H. Shi M. E. Negretti J. Chauchat K. Blanckaert U. Lemmin D. A. Barry |
| author_facet | H. Shi M. E. Negretti J. Chauchat K. Blanckaert U. Lemmin D. A. Barry |
| author_sort | H. Shi |
| collection | DOAJ |
| description | Abstract Understanding coastal plane jets which occur when a body of water discharges into an ocean or a lake through a channel or outlet is important, since they play a significant role in sediment, nutrient, and pollutant exchange. This study investigates the nearfield of initially shallow, neutrally buoyant plane jets, bounded by a free surface and a sloping bottom (Sloping Bottom Jet; SBJ) that issue into a laterally unconfined quiescent ambient both experimentally and numerically, and compares them with a plane jet flowing over a horizontal bottom (Horizontal Bottom Jet; HBJ). Results revealed that, different from the HBJ, the width and centerline velocity of SBJ decrease near the mouth. The SBJ width gradually increases after that as the transverse longitudinal velocity profile progressively transforms from a “top‐hat” into a Gaussian distribution. Once the Gaussian distribution is established, both jets diverge and centerline velocity decreases. Shear layers are generated on the sides of both jets with Kelvin Helmholtz‐type Coherent Structures (KHCS) developing inside. KHCS produce periodic velocity fluctuations with a Strouhal number of ∼0.079 and contribute significantly to momentum exchange and turbulent kinetic energy production. Since the thickness of the SBJ increases longitudinally, the vertical extent of KHCS also increases. When the two shear layers meet and merge at the centerline, they cause a flapping motion of the jet. This location is closer to the jet mouth for SBJs than for the HBJ. These findings demonstrate that a sloping bottom modifies the flow field from quasi‐2D for the HBJ to strongly 3D for SBJs. |
| format | Article |
| id | doaj-art-3bb34bc64e9740c5a0efd61c65f412a3 |
| institution | OA Journals |
| issn | 0043-1397 1944-7973 |
| language | English |
| publishDate | 2024-04-01 |
| publisher | Wiley |
| record_format | Article |
| series | Water Resources Research |
| spelling | doaj-art-3bb34bc64e9740c5a0efd61c65f412a32025-08-20T02:36:39ZengWileyWater Resources Research0043-13971944-79732024-04-01604n/an/a10.1029/2023WR034826Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom BoundaryH. Shi0M. E. Negretti1J. Chauchat2K. Blanckaert3U. Lemmin4D. A. Barry5Ecological Engineering Laboratory (ECOL) Faculty of Architecture, Civil and Environmental Engineering (ENAC) Environmental Engineering Institute (IIE) École Polytechnique Fédérale de Lausanne (EPFL) Lausanne SwitzerlandUniversité Grenoble Alpes CNRS Grenoble INP LEGI UMR 5519 Grenoble FranceUniversité Grenoble Alpes CNRS Grenoble INP LEGI UMR 5519 Grenoble FranceResearch Unit Hydraulic Engineering and Environmental Hydromechanics Institute of Hydraulic Engineering and Water Resources Management Technische Universität Wien Vienna AustriaEcological Engineering Laboratory (ECOL) Faculty of Architecture, Civil and Environmental Engineering (ENAC) Environmental Engineering Institute (IIE) École Polytechnique Fédérale de Lausanne (EPFL) Lausanne SwitzerlandEcological Engineering Laboratory (ECOL) Faculty of Architecture, Civil and Environmental Engineering (ENAC) Environmental Engineering Institute (IIE) École Polytechnique Fédérale de Lausanne (EPFL) Lausanne SwitzerlandAbstract Understanding coastal plane jets which occur when a body of water discharges into an ocean or a lake through a channel or outlet is important, since they play a significant role in sediment, nutrient, and pollutant exchange. This study investigates the nearfield of initially shallow, neutrally buoyant plane jets, bounded by a free surface and a sloping bottom (Sloping Bottom Jet; SBJ) that issue into a laterally unconfined quiescent ambient both experimentally and numerically, and compares them with a plane jet flowing over a horizontal bottom (Horizontal Bottom Jet; HBJ). Results revealed that, different from the HBJ, the width and centerline velocity of SBJ decrease near the mouth. The SBJ width gradually increases after that as the transverse longitudinal velocity profile progressively transforms from a “top‐hat” into a Gaussian distribution. Once the Gaussian distribution is established, both jets diverge and centerline velocity decreases. Shear layers are generated on the sides of both jets with Kelvin Helmholtz‐type Coherent Structures (KHCS) developing inside. KHCS produce periodic velocity fluctuations with a Strouhal number of ∼0.079 and contribute significantly to momentum exchange and turbulent kinetic energy production. Since the thickness of the SBJ increases longitudinally, the vertical extent of KHCS also increases. When the two shear layers meet and merge at the centerline, they cause a flapping motion of the jet. This location is closer to the jet mouth for SBJs than for the HBJ. These findings demonstrate that a sloping bottom modifies the flow field from quasi‐2D for the HBJ to strongly 3D for SBJs.https://doi.org/10.1029/2023WR034826sloping bottom jetshear layersKelvin Helmholtz coherent structuresjet flappingturbulent kinetic energy budget |
| spellingShingle | H. Shi M. E. Negretti J. Chauchat K. Blanckaert U. Lemmin D. A. Barry Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary Water Resources Research sloping bottom jet shear layers Kelvin Helmholtz coherent structures jet flapping turbulent kinetic energy budget |
| title | Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary |
| title_full | Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary |
| title_fullStr | Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary |
| title_full_unstemmed | Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary |
| title_short | Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary |
| title_sort | tracking the nearfield evolution of an initially shallow neutrally buoyant plane jet over a sloping bottom boundary |
| topic | sloping bottom jet shear layers Kelvin Helmholtz coherent structures jet flapping turbulent kinetic energy budget |
| url | https://doi.org/10.1029/2023WR034826 |
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