Numerical simulation of grid-generated turbulent particulate flow by three-dimensional Reynolds stress/Dispersse vooluse voreturbulentsi arvmodelleerimine kolmemootmelise Reynoldsi pingete mudeliga

A three-dimensional (3D) Reynolds stress turbulence model based on 3D Reynolds-averaged Navier-Stokes equations has been elaborated for grid-generated turbulence in particulate downward flow arranged in the channel domain of the square cross section. The model presented considers both the enhancement and attenuation of turbulence by means of the additional terms of the transport equations of the normal Reynolds stress components. It allows us to carry out calculations covering the long distance of the channel length without using algebraic assumptions for various components of the Reynolds stress. The results obtained show the effects of particles and mesh size of the turbulence generating grids on turbulence modification. In particular, the presence of solid particles at the initial period of turbulence decay results in the pronounced enhancement of turbulence that diminishes appreciably downwards in the area of typical channel turbulent flow. As the results show, the character of modification of all three normal components of the Reynolds stress taking place at the initial period of turbulence decay are uniform almost all over the channel cross sections. The increase in the grid mesh size slows down the rate of the turbulence enhancement which is caused by particles. Key words: numerical simulation, Reynolds stress turbulence model, grid-generated turbulence, particulate channel flow. Kasutatud kolmemootmeline Reynoldsi pingete mudel baseerub keskmistatud kolmemootmelistel NavieriStokesi vorranditel ja seda rakendatakse ohktahkete osakeste ulalt alla suunatud vooluse voreturbulentsi analuusil ristkulikukujulises kanalis. Mudel voimaldab kirjeldada nii turbulentsi intensiivistumist kui ka sumbumist, kasutades taiendavaid liikmeid Reynoldsi pingete normaalkomponentide ulekandevorrandites. Mudel on kasutatav kanali pikal osal, ilma et oleks vaja rakendada algebralisi moondusi erinevatele Reynoldsi pingete komponentidele. Saadud tulemused kinnitavad tahkete osakeste ja turbuleeriva vore mootmete moju turbulentsi muutumise iseloomule. Seejuures kutsub tahkete osakeste olemasolu vooluses esile selgesti valjendunud turbulentsi intensiivistumise voreturbulentsi haabumise algstaadiumis ja turbulentsi olulise norgenemise allavoolu iseloomulikus turbulentse kanalvooluse tsoonis. Nagu tulemustest nahtub, on koigi kolme Reynoldsi pinge normaalkomponendi muutumise iseloom voreturbulentsi haabumise algosas samalaadne peaaegu kogu kanali ristloikel. Turbuleeriva vore si