COMPUTATIONAL SNAPSHOT OF FLOW GENERATED BY AXIAL IMPELLER IN BAFFLEDSTIRRED VESSELS

The ability to numerically simulate the flow in baffled, stirred vesse ls is fast becoming vital io their optimal design, Most of the past at tempts have adopted a black box treatment to the impeller swept region , requiring experimentally-based input. More recent effects are based on the computation of the full time varying flow held within and outsi de the impeller swept region. An intermediate approach has been develo ped here, in which a quasi-steady flow is computed for any momentary i mpeller position, The method proposed here raptures almost all the sig nificant details of the now both within and outside the impeller witho ut requiring any empirical input/adjustable parameter. The method was applied to the flow generated by an axial impeller which is the most w idely used impeller in the process industries. The case of a fully baf fled vessel with standard pitched blade turbine was simulated using a FLUENT code. The time-averaged momentum transport equations were solve d along with a turbulence model. The time derivative terms in the full transport equations were formulated in terms of spatial derivatives f or the impeller swept region. The impeller rotation tvas simulated in terms uf appropriate source terms at the blade surfaces, The model pre dictions were compared with the published experimental data obtained u sing the laser Doppler anemometer. It must be emphasized here again th at all the predictions were obtained by specifying just an impeller ge ometry, location and tip speed without requiring ally boundary conditi ons near the impeller, The influence of impeller clearance on the gene rated flow was also correctly simulated. The approach presented here c an be used as a general purpose design tool for screening various mixe r configurations and to evolve an optimum stirred vessel design.