Assessment of k–ε models using tetrahedral grids to describe the turbulent flow field of a PBT impeller and validation through the PIV technique  

作　　者：Victor X. Mendoza-Escamilla Alejandro Alonzo-Garcia Helvio R. Mollinedo Israel Gonzalez-Neria J. Antonio Yanez-Varela Sergio A. Martinez-Delgadillo 

机构地区：[1]Depto. Electronica, Universidad Autonoma Metropolitana Azcapotzalco, Av. San Pablo 180, Azcapotzalco CP 07740, Mexico D.F., Mexico [2]CONACyT-Centro de Ingenierfa y Desarrollo Industrial, Av. Piaya Pie de la Cuesta 702, Desarrollo San Pablo, 76125 Queretaro, Qro., Mexico [3]UPIITA, Instituto Politecnico Nacional, Av. IPN 2580, G.A. Madero CP 07340, Mexico D.F., Mexico [4]Depto. Ciencias Basicas, Universidad Autonoma Metropolitana Azcapotzalco, Av. San Pablo 180, Azcapotzalco CP 07740, Mexico D.F, Mexico

出　　处：《Chinese Journal of Chemical Engineering》2018年第5期942-956,共15页中国化学工程学报（英文版）

基　　金：the National Council of Science and Technology, Mexico CONACyT for the support provided for this research, through the Basic Science project CB-2011/ 169786

摘　　要：In turbulence modeling, the RNG and Realizable models have important improvements in the turbulent production and dissipation terms in comparison to the Standard. The selection of the appropriate turbulence model has an impact on the convergence and solution in STRs, and they are used in mixing, multiphase modeling or as starting solution of transient models as DES and LES. Although there are several studies with the pitched blade turbine(PBT) impeller, most of them used the Standard model as representative of all k–ε models, using structured hexahedral grids composed of low number of cells, and in some cases under axial symmetry assumptions.Accordingly, in this work the assessment of the Standard, RNG and Realizable models to describe the turbulent flow field of this impeller, using the Multiple Reference Frame(MRF) and Sliding Mesh(SM) approaches with tetrahedral domains in dense grids, is presented. This kind of cell elements is especially suitable to reproduce complex geometries. Flow velocities and turbulent parameters were verified experimentally by PIV and torque measurements. The three models were capable of predicting fairly the pumping number, the power number based on torque, and velocities. Although the RNG improved the predictions of the turbulent kinetic energy and dissipation rate, the Realizable model presented better performance for both approaches. All models failed in the prediction of the total dissipation rate, and a dependence of its value on the number of cells for the MRF was found.In turbulence modeling, the RNG and Realizable models have important improvements in the turbulent produc- tion and dissipation terms in comparison to the Standard. The selection of the appropriate turbulence model has an impact on the convergence and solution in STRs, and they are used in mixing, multiphase modeling or as starting solution of transient models as DES and LES. Although there are several studies with the pitched blade turbine （PBT） impeller, most of them used the Standard model as representative of all k-ε models, using struc- tured hexahedral grids composed of low number of cells, and in some cases under axial symmetry assumptions. Accordingly, in this work the assessment of the Standard, RNG and Realizable models to describe the turbulent flow field of this impeller, using the Multiple Reference Frame （MRF） and Sliding Mesh （SM） approaches with tetrahedral domains in dense grids, is presented. This kind of cell elements is especially suitable to reproduce complex geometries. Flow velocities and turbulent parameters were verified experimentally by PIV and torque measurements. The three models were capable of predicting fairly the pumping number, the power number based on torque, and velocities. Although the RNG improved the predictions of the turbulent kinetic energy and dissipation rate, the Realizable model presented better performance for both approaches. All models failed in the prediction of the total dissipation rate, and a dependence of its value on the number of cells for the MRF was found.

关 键 词：Tetrahedral grids PIV Turbulent flow k-ε models Stirred vessel 

分 类 号：O35[理学—流体力学] TL334[理学—力学]