Wet ball mill that has been extensively used to comminute the raw materials in various industries possesses the advantages of large production capacity,high grinding efficiency,low investment and so on.Wet mill is a t...Wet ball mill that has been extensively used to comminute the raw materials in various industries possesses the advantages of large production capacity,high grinding efficiency,low investment and so on.Wet mill is a typical gas-liquid-solid three-phase system,and the interaction between these three phases is quite complex,resulting in the difficulty to simulate the wet milling process.As a consequence,a numerical model by coupling computational fluid dynamics(CFD),discrete element method(DEM)and volume of fluid(VOF)is developed to accurately simulate the wet milling process.A novel scheme is also devised and incorporated into CFD-DEM-VOF model to treat the interphase coupling when the particles and CFD cells have the comparable size that will be encountered in simulating the wet milling process.The accuracy of the established CFD-DEM-VOF coupling model is then validated by several test cases,including the single particle sedimentation in air-liquid domain,water entry of particle assembly and three-phase flows in a lab-scale wet mill and an industrial-scale wet mill.Furthermore,the effects of CFD cell size(2.5,5 and 10 mm)and mill rotation speed(10,30 and 50 r/min)on the prediction accuracy are also explored by the test case of lab-scale mill.The results indicate that using the quite coarse CFD cells can deteriorate the simulation accuracy,and increasing the mill rotation speed will enhance this influence.Nevertheless,adopting the very fine CFD cells(e.g.,2.5 mm in this work)in our model is not necessary in terms of the accuracy in simulating the particle behaviors,and the reliable prediction of particle behaviors can still be obtained while using the relatively large CFD cells(e.g.,5 mm in this paper).展开更多
This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid(CFD-DEM-VOF)model to simulate the complex behavior of particle-laden flows w...This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid(CFD-DEM-VOF)model to simulate the complex behavior of particle-laden flows with free surfaces.The coupling between the fluid and particle phases is established through the implemented continuity,momentum,and alpha transport equation.The coupled particle forces such as drag,pressure gradient,dense virtual mass,viscous,and interface forces are also integrated,with drag and dense virtual mass forces being dependent on local porosity.The integrated conservative alpha transport equation ensures phase volume conservation during interactions between particles and water.Additionally,we have implemented a trilinear interpolation method designed to operate on unstructured hexahedral meshes.This method has been tested for its ability to properly resolve the coupling effects in the numerical simulations,particularly in cases with a relatively low cell-size ratio.The model is validated through three distinct test cases:single particle water entry,dam break with particles,and water entry of a group of particles case.The experimental setup is built to study the dynamics of the water entry of a group of particles,where three key flow features are analyzed:the evolution of average particle velocity,cavity shape,and particle dispersion cloud profiles in water.The tests involve four different scenarios,including two different water levels(16.1 and 20.1 cm)and two different particle densities(2650 and 4000 kg/m3).High-speed videometry and particle tracking velocimetry(using ImageJ/TrackMate)methods are employed for experimental data acquisition.It is demonstrated that numerical results are in excellent agreement with theoretical predictions and experimental data.The study highlights the significance of vortices in cavity shaping and particle dispersion.The validated CFD-DEM-VOF model constitutes a robust tool for simulating particle-laden flows,contributing valuable insights into the complex interplay between particles and fluids.展开更多
基金supported by National Natural Science Foundation of China(No.22078283)State Key Laboratory of Intelligent Optimized Manufacturing in Mining&Metallurgy Process(No.BGRIMM-KZSKL-2022-3).
文摘Wet ball mill that has been extensively used to comminute the raw materials in various industries possesses the advantages of large production capacity,high grinding efficiency,low investment and so on.Wet mill is a typical gas-liquid-solid three-phase system,and the interaction between these three phases is quite complex,resulting in the difficulty to simulate the wet milling process.As a consequence,a numerical model by coupling computational fluid dynamics(CFD),discrete element method(DEM)and volume of fluid(VOF)is developed to accurately simulate the wet milling process.A novel scheme is also devised and incorporated into CFD-DEM-VOF model to treat the interphase coupling when the particles and CFD cells have the comparable size that will be encountered in simulating the wet milling process.The accuracy of the established CFD-DEM-VOF coupling model is then validated by several test cases,including the single particle sedimentation in air-liquid domain,water entry of particle assembly and three-phase flows in a lab-scale wet mill and an industrial-scale wet mill.Furthermore,the effects of CFD cell size(2.5,5 and 10 mm)and mill rotation speed(10,30 and 50 r/min)on the prediction accuracy are also explored by the test case of lab-scale mill.The results indicate that using the quite coarse CFD cells can deteriorate the simulation accuracy,and increasing the mill rotation speed will enhance this influence.Nevertheless,adopting the very fine CFD cells(e.g.,2.5 mm in this work)in our model is not necessary in terms of the accuracy in simulating the particle behaviors,and the reliable prediction of particle behaviors can still be obtained while using the relatively large CFD cells(e.g.,5 mm in this paper).
基金Sepro Mineral Systems through the Mitacs Accelerate project No:IT12396.We would also like to express our appreciation to Compute Canada and UBC ARC for supporting PIME Lab by granting us access to their high-performance computing platforms.The simulations presented in this work were conducted using the Compute Canada Beluga and UBC ARC Sockeye clusters,both of which contributed equally to the computational resources utilized.
文摘This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid(CFD-DEM-VOF)model to simulate the complex behavior of particle-laden flows with free surfaces.The coupling between the fluid and particle phases is established through the implemented continuity,momentum,and alpha transport equation.The coupled particle forces such as drag,pressure gradient,dense virtual mass,viscous,and interface forces are also integrated,with drag and dense virtual mass forces being dependent on local porosity.The integrated conservative alpha transport equation ensures phase volume conservation during interactions between particles and water.Additionally,we have implemented a trilinear interpolation method designed to operate on unstructured hexahedral meshes.This method has been tested for its ability to properly resolve the coupling effects in the numerical simulations,particularly in cases with a relatively low cell-size ratio.The model is validated through three distinct test cases:single particle water entry,dam break with particles,and water entry of a group of particles case.The experimental setup is built to study the dynamics of the water entry of a group of particles,where three key flow features are analyzed:the evolution of average particle velocity,cavity shape,and particle dispersion cloud profiles in water.The tests involve four different scenarios,including two different water levels(16.1 and 20.1 cm)and two different particle densities(2650 and 4000 kg/m3).High-speed videometry and particle tracking velocimetry(using ImageJ/TrackMate)methods are employed for experimental data acquisition.It is demonstrated that numerical results are in excellent agreement with theoretical predictions and experimental data.The study highlights the significance of vortices in cavity shaping and particle dispersion.The validated CFD-DEM-VOF model constitutes a robust tool for simulating particle-laden flows,contributing valuable insights into the complex interplay between particles and fluids.
