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The performance of a coaxial mixer equipped with an anchor combined to either a radial or an axial impeller was investigated. The system was operated in both counter- and corotating modes in the laminar and transition flow regimes. Experimental and numerical data regarding power consumption, mixing time, tracer evolution, and flow characterization were collected and compared. On the basis of these mixing efficiency criteria, the corotating mode was found to be a better choice for both mixers in the investigated flow regimes. The axial impeller−anchor mixer was also found to be more efficient in terms of energy consumption and mixing energy compared to the Rushton−anchor configuration.

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SUMMARY A parallel sliding mesh algorithm for the finite element simulation of viscous fluid flows in agitated tanks is presented. Lagrange multipliers are used at the sliding interfaces to enforce the continuity between the fixed and moving subdomains. The novelty of the method consists of the coupled solution of the resulting velocity–pressure‐Lagrange multipliers system of equations by an ILU(0)‐QMR solver. A penalty parameter is introduced for both the interface and the incompressibility constraints to avoid pivoting problems in the ILU(0) algorithm. To handle the convective term, both the Newton–Raphson scheme and the semi‐implicit linearization are tested. A penalty parameter is introduced for both the interface and the incompressibility constraints to avoid the failure of the ILU(0) algorithm due to the lack of pivoting. Furthermore, this approach is versatile enough so that it allows partitioning of sliding and fixed subdomains if parallelization is required. Although the sliding mesh technique is fairly common in CFD, the main advantage of the proposed approach is its low computational cost due to the inexpensive and parallelizable calculations that involve preconditioned sparse iterative solvers. The method is validated for Couette and coaxial stirred tanks. Copyright © 2011 John Wiley & Sons, Ltd.

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