Influence of the turbulence closure scheme on the finite-element simulation of the upwelling in the wake of a shallow-water island
Blaise, S.; Deleersnijder, E.; White, L.; Remacle, J.-F. (2007). Influence of the turbulence closure scheme on the finite-element simulation of the upwelling in the wake of a shallow-water island. Cont. Shelf Res. 27(18): 2329-2345. dx.doi.org/10.1016/j.csr.2007.06.003
In: Continental Shelf Research. Pergamon Press: Oxford; New York. ISSN 0278-4343; e-ISSN 1873-6955, meer
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| Trefwoorden |
Analysis > Mathematical analysis > Numerical analysis > Finite element method
Motion > Water motion > Circulation > Water circulation > Shelf dynamics
Motion > Water motion > Lee eddies
Motion > Water motion > Vertical water movement > Upwelling > Coastal upwelling
Motion > Water motion > Water currents > Tidal currents
Turbulence
ISEW, Great Barrier Reef, Rattray I. [Marine Regions]
Marien/Kust |
| Author keywords |
finite element method; turbulence closure scheme; upwelling; Lee eddies; shelf dynamics; tidal currents; unstructured mesh; Australia; great barrier reef; Rattray island |
| Abstract |
A three-dimensional finite-element model is used to investigate the tidal flow around Rattray Island, Great Barrier Reef, Australia. Field measurements and visual observations show both stable eddies developing at rising and falling tide in the wake of the island. The water turbidity suggests intense upwelling able to carry bed sediments upwards. Based on previous numerical studies, it remains unclear at this point whether the most intense upwelling occurs near the centre of the eddies or off the island's tips, closer to the island. All these studies resorted to a very simple turbulence closure, with a zero-equation model whereby the coefficient of vertical viscosity is computed via an algebraic expression. In this work, we aim at studying the influence of the turbulence closure on model results, with emphasis on the prediction of vertical motions. The Mellor and Yamada level 2.5 closure scheme is used and an increase in the intensity of vertical transport is observed. This increase is partly explained by the fact that the Mellor and Yamada model takes into account the hysteresis effect in the time variation of turbulence variables. The influence of the advection of turbulence variables is estimated to be negligible. By a better representation of transient coastal phenomena, the Mellor and Yamada level 2.5 turbulence closure improves the model to a significant degree. |
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