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Modelling of fluid flow with complex rheology

Niklas M., Asendrych D.

Systems : journal of transdisciplinary systems science

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2006

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Vol. 11, nr 1

63-73

EN

The paper concerns numerical modelling of the paper pulp flow of a non-Newtonian fluid with complex rheological properties. The work is aimed at optimisation of the performance of a hydropulper used for the recovered paper defibration in paper recycling technology. The phenomenon under consideration reveals high degree of complexity and its proper modelling requires to solve a number of particular problems related to duality of flow regimes (coexistence of turbulent and laminar regimes governed by different constitutive models), complicated geometry, presence of moving elements of machine, unsteady nature of phenomena and complex material properties of medium. So high degree of complexity enforced the necessity of the use of commercial code Fluent as a computational tool. Its effective use was however possible after code extension with additional procedures (the so called UDF - the user defined functions) allowing to meet the requirements of the rheology

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Numerical simulation of microchannel network with complex geometry

Niklas M., Favre-Marinet M., Asendrych D.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2005

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Vol. 53, nr 4

351-359

EN

The paper presents the results of a numerical study devoted to the hydraulic properties of a network of parallel triangular microchannels (hydraulic diameter Dh = 110 [mi]m). Previous experimental investigations had revealed that pressure drop through the microchannels system dramatically increases for the Reynolds number exceeding value of 10. The disagreement of the experimental findings with the estimations of flow resistance based on the assumption of fully developed flow were suspected to result tram the so-called scale effect. Numerical simulations were performed by using the classical system of flow equations (continuity and Navier-Stokes equations) in order to explain the observed discrepancies. The calculations showed a very good agreement with the experimental results proving that there is no scale effect for !he rnicrochannels considered, i.e. the relevance of the constitutive flow model applied was confirmed. It was also clearly indicated that the excessive pressure losses in the high Reynolds number range are due to the secondary flows and separations appearing in several regions of the microchannel system.

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Numerical modelling of flow in microchannels

Niklas M., Favre-Marinet M.

Turbulence : international journal

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2002

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Vol. 8-9

149-158

EN

The paper presents numerical study of the flow in the system of microchannels. The computations were based on the classical laws of hydraulics. Comparison of the numerical results with experimental ones showed that is the mjcrocharme! system considered no scale effects were observed.