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首页> 外文期刊>Chemical Engineering Science >Measurements and modelling of free-surface turbulent flows induced by a magnetic stirrer in an unbaffled stirred tank reactor
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Measurements and modelling of free-surface turbulent flows induced by a magnetic stirrer in an unbaffled stirred tank reactor

机译：电磁搅拌器在无挡板搅拌釜反应器中引起的自由表面湍流的测量和建模

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摘要

Measurements and numerical simulations of turbulent flows with free-surface vortex in an unbaffled reactor agitated by a cylindrical magnetic stirrer are presented. Measurements of the three mean and fluctuating components of the velocity vector are made using a laser Doppler velocimetry in order to characterise the flow field at different speeds of the stirrer. A homogeneous Eulerian-Eulerian multiphase flow model coupled with a volume-of-fluid method for interface capturing is applied to determine the vortex shape and to compute the turbulent flow field in the reactor. Turbulence is modelled using a second-moment differential Reynolds-stress transport (RST) model, but for some cases the k-epsilon/k-omega based shear-stress transport (SST) model is also used. The predictions obtained using the ANSYS CFX-5.7 computational fluid dynamics code are compared with the images of the vortex and the measured distributions of mean axial, radial and tangential velocities and turbulent kinetic energy. The predicted general shape of the liquid free-surface is in good agreement with measurements, but the vortex depth is underpredicted. The overall agreement between the measured and the predicted axial and tangential velocities obtained with the RST model is good. However, the radial velocity is significantly underpredicted. Predictions of the turbulent kinetic energy yield reasonably good agreement with measurements in the bulk flow region, but discrepancy exists near the reactor wall where this quantity is underpredicted. The SST model predictions are generally of the same quality as those of the RST model, with the latter model providing better predictions of the tangential velocity distribution.
机译：提出了在无挡板反应器中由圆柱磁力搅拌器搅拌的带有自由表面涡流的湍流的测量和数值模拟。使用激光多普勒测速仪对速度矢量的三个均值和波动分量进行测量，以表征搅拌器不同速度下的流场。将均质欧拉-欧拉多相流模型与用于界面捕获的流体体积方法相结合，以确定旋涡形状并计算反应堆中的湍流场。湍流是使用第二阶微分雷诺应力传递（RST）模型进行建模的，但在某些情况下，还使用基于kε/k-ω的剪应力传递（SST）模型。将使用ANSYS CFX-5.7计算流体动力学代码获得的预测结果与涡旋图像以及测得的平均轴向，径向和切向速度以及湍动能分布进行比较。液体自由表面的预测总体形状与测量值非常吻合，但涡旋深度却被预测不足。用RST模型获得的轴向和切向速度的测量值与预测值之间的总体一致性很好。但是，径向速度明显不足。湍流动能的预测与总体流量区域的测量值相当吻合，但在反应器壁附近存在差异，在此处该数量的预测不足。 SST模型的预测质量通常与RST模型的质量相同，后者的模型提供了切向速度分布的更好预测。

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