There are several configurations of fluidized beds commonly used in wastewater treatment units. Often their hydrodynamics is challenging to be evaluated experimentally, or too complex to be predicted accurately with empirical correlations only. In the present study, the computational fluid dynamics technique was applied to evaluate the hydrodynamic behavior of a liquid–solid fluidized bed in tapered bioreactors. The simulations were run with OpenFOAM, and they were based on a 3D, transient, Eulerian–Eulerian two-phase approach coupled with a turbulence model. Different tapered bioreactor angles were considered in the study, and the results showed a decrease in flow velocity along with the height of the device. Moreover, the distribution of the bioparticles within the fluidized bed was not found to be uniform, and it changed with the angle. It was also observed that bioparticle collisions caused large velocity fluctuations. Even though the bioreactor presented a square cross section, results also proved that the presence of the dead zone was negligible.

中文翻译：

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方形截面锥形生物反应器中生物颗粒流化床流体动力学的数值研究

废水处理装置中常用的流化床有几种配置。通常，它们的流体动力学很难通过实验进行评估，或者过于复杂而无法仅通过经验相关性进行准确预测。在本研究中，计算流体动力学技术被应用于评估锥形生物反应器中液固流化床的流体动力学行为。模拟使用 OpenFOAM 运行，它们基于 3D、瞬态、欧拉-欧拉两相方法以及湍流模型。在研究中考虑了不同的锥形生物反应器角度，结果显示流速随着装置的高度而降低。此外，发现流化床内生物颗粒的分布并不均匀，并且随角度而变化。还观察到生物粒子碰撞引起大的速度波动。即使生物反应器呈现方形横截面，结果也证明死区的存在可以忽略不计。