Large-eddy simulation of the turbulent free-surface flow in an unbaffled stirred tank reactor

Lamarque, Nicolas; Zoppé, Béatrice; Lebaigue, Olivier; Dolias, Y.; Bertrand, Murielle; Ducros, F.

doi:10.1016/j.ces.2010.03.014

Cited by 46 publications

(29 citation statements)

References 54 publications

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“…This indicates a strong unsteadiness of the flow. Additional comparisons, at different heights can be found in a previous publication [28] which shows that most of the mean and fluctuating velocities are well described by our LES simulation. A more detailed analysis of the flow inside the vortex reactor can be provided by a spectral analysis.…”

Section: Comparison With Experimental Resultsmentioning

confidence: 92%

Mixing Study in an Unbaffled Stirred Precipitator Using LES Modelling

Bertrand

Parmentier

Lebaigue

et al. 2012

International Journal of Chemical Engineering

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This paper describes the CFD modelling of a reactor operating in the nuclear industry using LES approach. The reactor consists of an unbaffled stirred tank reactor in which plutonium precipitation reactions are carried out. The flow generated in such a precipitator is complex and there is very little information available in the literature about unbaffled reactors stirred with magnetic rod. That is why a hydrodynamic modelling has been developed using computational fluid dynamics (CFD) in order to get accurate description of mixing phenomena inside the precipitator and therefore to be able to predict the solid particle properties. Due to the strong turbulence anisotropy, the turbulence transport simulation is achieved by a large eddy simulation (LES) approach which gives unsteady solutions. The numerical simulations are performed in 3D using the Trio U code developed at the Commissariat a l'Énergie Atomique. The predictive performances of the modelling are analysed through a mixing phenomena study. Both experimental and numerical studies are performed. This work shows how hydrodynamics inside the reactor can have a noticeable effect on the precipitate properties and how LES modelling is a very effective tool for the process control.

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Section: Comparison With Experimental Resultsmentioning

confidence: 92%

Mixing Study in an Unbaffled Stirred Precipitator Using LES Modelling

Bertrand

Parmentier

Lebaigue

et al. 2012

International Journal of Chemical Engineering

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“…The dark grey and light grey dots from the edges of the dredging plume are found further away from the origin which means that the turbulence at the edges of the dredging plume is more anisotropic. For other mixing flows, like mixing inside a stirred tank also strong anisotropic turbulence was found with the two invariant values all over the Lumley triangle [54,55]. Because the turbulence inside the dredging plume is found to be strongly anisotropic, especially near the edges which are most interesting for the generation of a surface plume, it can be expected that RANS models which assume isotropic turbulence will not result in accurate surface plume predictions.…”

Section: Time Averaged Cross Sectionsmentioning

confidence: 89%

Influence of important near field processes on the source term of suspended sediments from a dredging plume caused by a trailing suction hopper dredger: the effect of dredging speed, propeller, overflow location and pulsing

2014

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Influence of important near field processes on the source term of suspended sediments from a dredging plume caused by a trailing suction hopper dredger: the effect of dredging speed, propeller, overflow location and pulsing Lynyrd de Wit · Cees van Rhee · Arno Talmon Abstract Detailed Large Eddy Simulation (LES) results are presented on near field mixing of overflow dredging plumes generated at a Trailing Suction Hopper Dredger (TSHD). Special attention is given to the generation of a surface plume. A surface plume is that part of the dredging plume which separates from the main plume body and ends up near the free surface. A surface plume can stay suspended for hours and during this time it can be transported to ecological sensitive areas around a dredging site. Hence, for a correct environmental impact assessment of a dredging project with TSHD's it is important to understand near field mixing and thus obtain a correct estimate for the source term of suspended sediments formed by the surface plume. The detailed LES are used to investigate systematically the influence of dredging speed, overflow location, propeller and pulsing frequency (caused by ship motions) on near field mixing of dredging plumes and the generation of a surface plume. LES results are validated with experimental results. The investigated variations have significant influence on the development of the dredging overflow plume in general and surface plume in particular. With normal dredging speed the surface plume varied between 0 and 2 % of the overflow flux with maximum time averaged prototype-SSC 42 Environ Fluid Mech (2015) 15:41-66 (suspended sediment concentration) levels of 1-31 mg/l at the free surface at a horizontal distance x/D = 100 (D is initial plume diameter). With high dredging speed the surface plume varied between 0.2 and 18 % with maximum time averaged prototype-SSC levels of 10-352 mg/l at the free surface. The large range in surface plume percentage indicates the importance of detailed near field modelling including all significant processes for a correct estimate of the source term of suspended sediment from a dredging plume. All results are obtained without influence of a bed, hence in shallow areas the amount of surface plume could be larger.

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“…The authors conclude that the EDC predictions could be improved by taking into account instantaneous concentrations instead of time-averaged concentrations [22]. More generally, in the literature, the studies clearly point out the advantages of the LES approach for predicting mixing phenomena [23][24][25][26], even as far as the mean flow is concerned. Especially, LES enables to capture macro-instabilities [27][28] which are known to have a strong influence on mixing and segregation.…”

Section: Les Modelling Of Micromixingmentioning

confidence: 98%