ABSTRACT

Hydrocyclones are widely used in industry and CFD has been used to compute them. Reynolds stress turbulence models (RSM), which are computationally costly and oftentimes hard to converge, are often recommended in these computations. The present work has selected a liquid-liquid separation hydrocyclone for which single-phase experimental tangential and axial velocity profiles are available. CFD has been employed to test simpler turbulence models than the RSM and results have been compared with experimental data. The turbulence models assessed in the present work were: standard k-ε, standard k-ε with a curvature correction term, RNG k-ε, realizable k-ε, k-ω, SST, a two-time-scale linear eddy viscosity model, nonlinear quadratic and cubic k-ε eddy viscosity models and the Gibson and Launder and LRR Reynolds stress models. Computations have been carried out with OpenFOAM${}^{\circledR }$ 2.2.2. Results using the Gibson and Launder turbulence model have been compared to some obtained with Ansys${}^{\circledR }$ Fluent and these were in agreement. Results have shown that all turbulence models, apart from the RSM, returned basically the same tangential velocity profiles as the standard $k-ϵ$ model. All turbulence models have failed in predicting axial velocity. Assessment of the Reynolds stresses has indicated that the internal flow field in hydrocyclones might be shear dominant and that the Reynolds shear stress component ${\tau }_{yz}^t$ is the most relevant to correctly predict tangential velocity. Geometric proportions of hydrocyclones may affect significantly the intensity of rotational and streamline curvature effects. Two-equation eddy-viscosity models are likely to be able to attend such condition, since appropriate levels of eddy viscosity are predicted at free and forced vortexes regions, however further investigation is still needed.

摘要

水力旋流器在工业中被广泛使用，并且CFD已被用于计算它们。在这些计算中通常建议使用雷诺应力湍流模型（RSM），该模型计算量大且通常难以收敛。目前的工作选择了一种液-液分离水力旋流器，可用于单相实验切向和轴向速度分布。CFD已被用来测试比RSM更简单的湍流模型，并将结果与​​实验数据进行了比较。在目前的工作中所评估的湍流模型是：标准ķ - ε，标准ķ - ε具有曲率校正项，RNG ķ - ε，可实现ķ -ε，k - ω，SST，二次尺度线性涡旋粘度模型，非线性二次方和三次k - ε涡旋粘度模型以及Gibson和Launder以及LRR雷诺应力模型。已经使用OpenFOAM进行了计算${}^{\circledR }$2.2.2。使用Gibson和Launder湍流模型的结果已与使用Ansys获得的结果进行了比较${}^{\circledR }$流利，他们同意。结果表明，除RSM外，所有湍流模型都返回了与标准湍流基本相同的切线速度分布$ķ-ϵ$模型。所有湍流模型都无法预测轴向速度。雷诺应力的评估表明，水力旋流器的内部流场可能是剪切主导的，并且雷诺剪切应力分量${\tau }_{ÿž}^{Ť}$与正确预测切向速度最相关。水力旋流器的几何比例可能会显着影响旋转和流线曲率效应的强度。两方程式涡流粘度模型很可能能够满足这种条件，因为在自由涡流和强制涡流区域预测了适当的涡流粘度水平，但是仍然需要进一步的研究。