湍流环境下颗粒与气泡黏附过程的数值模拟研究

Numerical simulation of the attachment process of particles and bubbles in a turbulent environment

  • 摘要: 研究湍流环境中颗粒与气泡的黏附过程对于探究浮选微观过程具有重要意义。基于EDEM的API(应用程序编程接口)二次开发模块,建立了颗粒与气泡黏附过程相互作用的三维离散元法(DEM)模型。在Fluent软件中通过构建规则格栅以激发各向同性的湍流,并将湍流环境通过计算流体力学−离散元(CFD−DEM)加入到EDEM软件中。模拟了颗粒粒径为0.10、0.15、0.20、0.25和0.30 mm,颗粒密度为1500、2000和2500 kg/m3,球形度为0.746 ~ 0.854的不规则颗粒,和气泡直径为1.00、1.20、1.60和2.00 mm,在气泡与格栅间距离为1.00、1.50、2.00和3.00 mm的湍流环境下颗粒与气泡的黏附过程。研究了颗粒、气泡、流场各参数对于颗粒与气泡黏附过程的影响。结果发现,无论规则颗粒还是不规则颗粒在湍流环境中与气泡的黏附均存在临界脱附流速(颗粒与气泡发生脱附的最小湍流流场流速)。密度大的颗粒和粒径大的颗粒与气泡黏附的临界脱附流速更小,表明粒径和密度大的颗粒与气泡难以稳定黏附。气泡的直径越大,颗粒与气泡稳定黏附的临界脱附流速越小,颗粒越难以稳定黏附。在相同的流速下,气泡与格栅间距离越小,则流场湍流强度越大,颗粒与气泡稳定黏附的临界脱附流速越小,表明湍流强度的增加不利于颗粒与气泡的稳定黏附。球形度小的颗粒与气泡稳定黏附的临界脱附流速也较小,表明球形度小的颗粒与气泡难以稳定黏附。

     

    Abstract: The study of the attachment process between particles and bubbles in a turbulent environment is essential for understanding the microscopic process of flotation. The interaction force model between particles and bubbles is developed based on the API (Application Programming Interface) secondary development module of EDEM. The model establishes a three-dimensional discrete element method (DEM) to simulate the interaction process between particles and bubbles. Isotropic turbulence is generated by constructing regular grids in the Fluent software. The turbulent environment is then incorporated into the EDEM software using the computational fluid dynamics discrete element (CFD-DEM). The simulation consists of regular particles with sizes ranging from 0.10 to 0.30 mm and densities of 1500, 2000 and 2500 kg/m3. Additionally, the irregular particles with sphericity values ranging from 0.746 to 0.854 are included. Bubble sizes are set at 1.00, 1.20, 1.60, and 2.00 mm. To study the attachment process between particles and bubbles, the distance between the grid and the bubble in the turbulent environment are set as 1.00, 1.50, 2.00, and 3.00 mm. The results demonstrate the existence of a critical detachment flow rate (the minimum turbulent flow velocity where particles and bubbles cannot achieve a stable attachment state) for both regular and irregular particles adhering to bubbles in a turbulent environment. It is found that the particles with larger density and diameter exhibit a smaller critical detachment flow velocity when adhering to bubbles, indicating that particles with larger diameter and density have difficulty in achieving stable attachment with bubbles. As the bubble diameter increases, the critical detachment flow velocity required for stable particle-bubble attachment decreases, making it more difficult for particles to achieve stable attachment. At the same flow velocity, a smaller distance between the bubbles and the grid results in a higher turbulent flow intensity, leading to a smaller critical detachment flow velocity for stable particle-bubble attachment, suggesting that an increase in turbulent intensity is detrimental to the stable attachment of particles and bubbles. Furthermore, the particles with lower sphericity also exhibit a smaller critical detachment flow velocity for stable attachment to bubbles, indicating that the particles with lower sphericity have difficulty in achieving stable attachment with bubbles.

     

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