Effect Of Inter-phase Drag Law In CFD Simulation Of Liquid Haracteristics In A Solid-liquid Stirred Tank

Solid-liquid flow, widely used in industrial processing, is consist ofcontinuous phase and dispersed phase, and with complicated interactionbetween each phase.Limited test conditions and methods result in insufficiently researchin two phase flow. Engineering design and reactor scaling-up problemsare still based on experiment and empirical data. Recently, apart fromexperiment research, scientific researchers are inclined to give insightinvestigation in computational simulation with mathematical model, withwhich much more details of flow characteristics are available to obtainedwith lower cost. Furthermore, partial differential equation model in twophase flow can be efficiently solved by numerical simulation, whichcould help to master mechanics process of two phase flow system.Drag force correlations are mostly based on the local force balance ofa particle in multiphase flow simulation. However, knowledge of particleswarm is obviously a key issue for understanding the underlyingmechanisms of heterogeneous flow in dense dispersed particulate flowsystem. Drag force is a dominant factor in interactions between twophases according to previous literature. Virtual mass force, lift force are regarded as magnitude when continuous phase density is more thandispersed particle density. Thus, only drag force is discussed in this paper.Obviously, comprehension of interactions between particle-liquid phasesin dense particulate flows relies on precise quantification of liquid dragacting on single particle.Effect of drag correlation is concerned in this paper. SchillerNaumann, Wen Yu and modified Hill-Koch-Ladd (HKL) drag law areconducted, and the solid concentration range is from0.2%to15%. It isobserved that HKL drag law simulation results in terms of velocityprofiles and turbulence dampening are in more reasonable agreementwith experimental data than that of Schiller Naumann and Wen Yu draglaws. HKL drag law performed most appropriate to predict the velocityprofile and dampening trend within the volumetric concentration5%v/vin the near wall region. The predictions of velocity distribution and decaycondition with high particle volumetric concentration of10%v/v and15%v/v were found to be in reasonable agreement with literatureexperimental data. The relationship between liquid axial velocity andparticle concentration could be described asv/v1.35tip (1in near wall7mm, andv/vt ip (12.49in near wall2mm. Velocity distribution anddampening trend in impeller and near wall region in cylinder stirred tankwith the diameter of0.476m were simulated in this paper, with thevolumetric concentration15%v/v and25%v/v. The predictions of axial velocity profile and decay trend with HKL drag law showed betteragreement with experimental data than that with Gidaspow drag law inboth impeller and near wall region.