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Numerical investigations into the effect of turbulence on collision efficiency in flotation
Minerals Engineering ( IF 4.8 ) Pub Date : 2021-01-21 , DOI: 10.1016/j.mineng.2020.106744
S. Li , M.P. Schwarz , Y. Feng , P. Witt , C. Sun

At present, the theoretical understanding of the collisional interaction between particles and a single bubble under well-defined laminar flow conditions is relatively sound. However, there is a lack of experimental data and predictions on details of the interaction processes in stirred turbulent conditions, as exists in mineral flotation cells. This paper investigates the effect of turbulence on the efficiency of collision between particles and bubbles from a fundamental point of view. A computational fluid dynamics method is used to establish a bubble–particle collision efficiency model system for turbulent flow. The 3D model is used to systematically study the effect of fluid turbulence on bubble–particle collision efficiency. In order to isolate the phenomena caused by turbulent flow physics, the study is conducted in two parts: large-scale turbulence and small-scale turbulence, which are respectively larger and smaller than the bubble size. Large-scale turbulence is assumed to increase the speed of bubbles relative to the slurry, and in most cases, increase in the speed increases collision efficiency, though in some cases the gravitational effect can cause decrease in overall efficiency. Small-scale turbulence is treated through the effect of fluctuations on particle trajectories. Again, such turbulence increases collision efficiency when the turbulent particle Stokes number is less than or about unity, but has little effect for Stokes number much greater than unity. An equation for the increase in efficiency in the limit of small Stokes number is obtained from the simulations.



中文翻译:

湍流对浮选碰撞效率影响的数值研究

目前,在明确的层流条件下,对粒子与单个气泡之间的碰撞相互作用的理论理解还比较健全。然而,缺乏关于矿物浮选池中存在的搅拌湍流条件下相互作用过程细节的实验数据和预测。本文从基本的角度研究了湍流对粒子和气泡之间碰撞效率的影响。计算流体动力学方法用于建立湍流的气泡-颗粒碰撞效率模型系统。3D模型用于系统地研究流体湍流对气泡-颗粒碰撞效率的影响。为了隔离湍流物理学引起的现象,研究分两个部分进行:大湍流和小湍流分别大于和小于气泡尺寸。假定发生大的湍流会增加气泡相对于浆料的速度,并且在大多数情况下,速度的增加会提高碰撞效率,尽管在某些情况下,重力效应会导致整体效率降低。小尺度湍流通过波动对粒子轨迹的影响来处理。同样,当湍流粒子斯托克斯数小于或等于1时,这种湍流会提高碰撞效率,但是对于斯托克斯数远大于1的斯托克斯数几乎没有影响。从模拟中获得了在小斯托克斯数极限内效率增加的方程。分别大于和小于气泡大小。假定发生大的湍流会增加气泡相对于浆料的速度,并且在大多数情况下,速度的增加会提高碰撞效率,尽管在某些情况下,重力效应会导致整体效率降低。小尺度湍流通过波动对粒子轨迹的影响来处理。同样,当湍流粒子斯托克斯数小于或等于1时,这种湍流会提高碰撞效率,但对于斯托克斯数远大于1的影响很小。从模拟中获得了在小斯托克斯数极限内效率增加的方程。分别大于和小于气泡大小。假定发生大的湍流会增加气泡相对于浆料的速度,并且在大多数情况下,速度的增加会提高碰撞效率,尽管在某些情况下,重力效应会导致整体效率降低。小尺度湍流通过波动对粒子轨迹的影响来处理。同样,当湍流粒子斯托克斯数小于或等于1时,这种湍流会提高碰撞效率,但对于斯托克斯数远大于1的影响很小。从模拟中获得了在小斯托克斯数极限内效率增加的方程。速度的增加会提高碰撞效率,尽管在某些情况下重力效应会导致整体效率降低。小尺度湍流通过波动对粒子轨迹的影响来处理。同样,当湍流粒子斯托克斯数小于或等于1时,这种湍流会提高碰撞效率,但是对于斯托克斯数远大于1的斯托克斯数几乎没有影响。从模拟中获得了在小斯托克斯数极限内效率增加的方程。速度的增加会提高碰撞效率,尽管在某些情况下重力效应会导致整体效率降低。小尺度湍流通过波动对粒子轨迹的影响来处理。同样,当湍流粒子斯托克斯数小于或等于1时,这种湍流会提高碰撞效率,但对于斯托克斯数远大于1的影响很小。从模拟中获得了在小斯托克斯数极限内效率增加的方程。当湍流粒子斯托克斯数小于或等于1时,这种湍流会提高碰撞效率,但是对于斯托克斯数远大于1的斯托克斯数,则几乎没有影响。从模拟中获得了在小斯托克斯数极限内效率增加的方程。当湍流粒子斯托克斯数小于或等于1时,这种湍流会提高碰撞效率,但是对于斯托克斯数远大于1的斯托克斯数,则几乎没有影响。从模拟中获得了在小斯托克斯数极限内效率增加的方程。

更新日期:2021-01-22
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