Steady and unsteady computation of impeller‐stirred reactors

Harvey, Albert D.; Rogers, Stuart E.

doi:10.1002/aic.690421002

Cited by 71 publications

(29 citation statements)

References 10 publications

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“…flow. Several groups Harvey and Rogers, 1996;Ranade, 1997 have performed computational fluid dynamics analysis of baffled stirred tanks by computing a pseudosteady state solution that is really an instantaneous snapshot of a time-dependent Ž . three-dimensional 3-D flow.…”

Section: Figure 1 Three-rushton-turbine Stirred-tank Systemmentioning

confidence: 99%

Extensive validation of computed laminar flow in a stirred tank with three Rushton turbines

et al. 2001

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Section: Figure 1 Three-rushton-turbine Stirred-tank Systemmentioning

confidence: 99%

Extensive validation of computed laminar flow in a stirred tank with three Rushton turbines

et al. 2001

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“…Numerical simulation of such flows is far from trivial due, in part, to complex geometry. Recent advances on numerical algorithms and discretization methods have allowed the study of chaotic mixing in 3‐D flows with reasonable success 17–21. One advantage of numerical simulations is that, once a validated solution is obtained, they can provide a wealth of information that would be difficult to obtain experimentally.…”

Section: Introductionmentioning

confidence: 99%

Mixing of shear‐thinning fluids with yield stress in stirred tanks

et al. 2006

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“…In the present study, the geometry of the pitched-blade turbine was defined in the grid and the velocity profile near the impeller was calculated directly in the simulation. This approach has been validated by Harvey and Rogers (1996).…”

Section: Cfd Simulationsmentioning

confidence: 98%

CFD Simulations of Three‐dimensional Wall Jets in a Stirred Tank

Bhattacharya

Kresta

2002

Can J Chem Eng

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1C omputational fluid dynamics (CFD) is increasingly being used for the simulation of stirred tanks due to recent advances in computer speed and efficiency of numerical schemes. While simulations involving both steady state (Kresta and Wood, 1991;Fokema et al., 1994;Harvey et al., 1995; Ranade and Dommetti, 1996 and others) and time varying (Perng and Murthy, 1992; Derksen and Van den Akker, 1999) methods have been reported in the literature, emphasis has mainly been on the quantitative validation of flow close to the impeller. The main objective of this study is to extend the existing protocols for simulating time-averaged velocity fields to flow near the tank wall and in the bulk of the tank.Studies with axial impellers show that wall jets form in the region between the baffles and the tank wall and drive the bulk flow, imposing a single characteristic velocity scale on both the upflow at the wall and the recirculation in the center of the tank. Accuracy in prediction of the mean flow characteristics of the wall jets and the simulation of the bulk flow in the tank are therefore intimately linked. Moreover, Bittorf (2000) has shown that the velocities in the three-dimensional wall jets, in balance with the settling velocities of the solids, determine the cloud height of suspended solids at high solids concentration. The cloud height of the suspended solids along with the just suspended speed (N js ) of the impeller determines the uniformity of solids distribution in a stirred tank. While explicit relations between N js and the fluid/particle properties and the impeller type are available, the cloud height model proposed by Bittorf (2000) requires an accurate description of the effect of size, off-bottom clearance and speed of the impeller on the core velocity or source velocity of the jet. This study aims to address these issues by developing a low-cost CFD protocol which can be used to obtain geometry dependent parameters to the degree of accuracy required, without having to resort to scale model experiments.While a detailed description of the wall jets is available in Bittorf and Kresta (2001), the key results are restated here to facilitate comparison with CFD simulations in later sections. Figure 1a shows one of the wall jets formed between the baffle and the tank wall. The expansion of the jet and the decay of axial velocity in a vertical plane close to the baffle are shown for different axial positions in the tank. At any axial location, the axial velocity (U ) increases rapidly from the no slip condition at the wall to its maximum value (U m ), and then decreases with a smaller gradient. At y~ 1.7b, the axial velocity reverses direction due to recirculation and asymptotically approaches the recirculating velocity (U R ). The The flow near the tank wall in a stirred tank driven by a 45°pitched-blade turbine is simulated with Multiple Reference Frames, the k-e turbulence model and standard wall functions. The results are compared to the three-dimensional wall jet identified in a previous paper. The self-...

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Steady and unsteady computation of impeller‐stirred reactors

Cited by 71 publications

References 10 publications

Extensive validation of computed laminar flow in a stirred tank with three Rushton turbines

Extensive validation of computed laminar flow in a stirred tank with three Rushton turbines

Mixing of shear‐thinning fluids with yield stress in stirred tanks

CFD Simulations of Three‐dimensional Wall Jets in a Stirred Tank

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