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Large eddy simulation of turbulent pulp flow in a channel
Journal of Non-Newtonian Fluid Mechanics ( IF 2.7 ) Pub Date : 2020-09-28 , DOI: 10.1016/j.jnnfm.2020.104409
Nima Fallah Jouybari , Birgitta Engberg , Johan Persson

Large eddy simulation (LES) of turbulent flow of concentrated fiber suspension or pulp is carried out to investigate the flow and turbulence structures in a channel. The simulations are carried out for the turbulent flow of Eucalyptus pulp suspension using OpenFOAM for three fiber concentrations (c = 1.5, 2.0 and 2.5) and six different Reynolds numbers (6 ≤Res≤ 16,600). It is observed that the variation in flow regime is similar in the two lower fiber concentrations while the flow regime is highly affected by fiber concentration for c = 2.5. Visualizations of vortical structures for different Reynolds numbers and fiber concentrations are used to investigate different flow regimes. Variation of apparent viscosity with Reynolds number and fiber concentration is also presented to show its effect on the turbulent properties of fiber suspension flow. It is shown that the deviation of turbulent velocity profile from that of a Newtonian flow increases with an increase in Reynolds number and fiber concentration. Also, the extend of buffer layer increases at higher Re. Using the calculated turbulent velocity profile, the values of constant in logarithmic velocity profile is proposed for fiber suspension. Finally, a discussion is presented on the variation of turbulent intensities and Reynolds stress with Reynolds number and fiber concentration.



中文翻译:

通道中纸浆湍流的大涡模拟

对浓缩纤维悬浮液或纸浆的湍流进行大涡模拟(LES),以研究通道中的流动和湍流结构。该仿真使用OpenFOAM桉树纸浆悬浮液的紊流三个纤维浓度(进行C ^  = 1.5,2.0和2.5)和6个不同的雷诺数(6≤Re小号≤16600)。可以观察到,在两种较低的纤维浓度下,流动状态的变化相似,而对于c,流动状态受纤维浓度的影响很大。 = 2.5。不同雷诺数和纤维浓度的涡旋结构的可视化用于研究不同的流态。还提出了表观粘度随雷诺数和纤维浓度的变化,以表明其对纤维悬浮液流动的湍流特性的影响。结果表明,随着雷诺数和纤维浓度的增加,湍流速度曲线与牛顿流速度的偏差增加。同样,缓冲层的延伸在较高的Re处增加。利用计算出的湍流速度分布图,提出了对数速度分布图常数用于纤维悬浮。最后,讨论了湍流强度和雷诺应力随雷诺数和纤维浓度的变化。

更新日期:2020-10-06
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