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Metoda robnih elementov za dinamiko viskoelastične Maxwellove tekočine
Leopold Škerget, Matej Požarnik, 2002, original scientific article

Abstract: V prispevku je prikazan razvoj numerične sheme na osnovi metode robnih elementov (MRE) za modeliranje ravninskih tokov viskoelastične tekočine. Kot podlaga za razvoj je namenjena shema za modeliranje nestisljivih viskoznih tokov, ki smo jo razširili in ji dodali potrebne člene za zajemanje viskoelastičnosti nenewtonovskih tekočin. Posebno pozornost smo namenili integraciji ohranitvenih zakonov in reoloških modelov. Shema je zapisana za hitrostno-vrtinčno formulacijo vodilnih enačb. Kot testni primeri so predstavljeni tokovi nenewtonovske Maxwellove tekočine v kanalih različnih geometrijskih oblik.
Published: 10.07.2015; Views: 608; Downloads: 39
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Experimental Investigations of Flow and Mixing in Taylor-Couette Reactor using PIV and LIF Methods
Anna Racina, Matej Požarnik, Matthias Kind, 2005, original scientific article

Abstract: Modern laser-optical methods (Particle Image Velocimetry and Laser Induced Fluorescence) for flow characterization are implemented to study the mixing behavior in Taylor-Couette Reactor without axial flow. In this study, cylinders with a radius-ratio equal to 0.63 are taken into account, which results in a direct transition from laminar fluid flow regime to a turbulent one. During PIV measurements special attention is paid to the system settings at which the error vector fraction is minimized. Energy dissipation rate and the distribution of local micromixing times are calculated from PN data. The average dissipation rate has values in the order of magnitude of 1▫$^{-3}$▫- 1▫$0^{-1}$▫ W/kg depending on the rotation rate of inner cylinder. The corresponding micromixing times are from 50 down to 5 ms. For LIF experiments the calibration procedure and the image processing sequence are presented. LIF data are used to study macro- and mesomixing. Macromixing in axial direction is approximated using a one-parameter model of mixing (cascade of stirred vessels). The value of diffusion coefficient (3 1▫$0^{-5}$▫) m2/s) agrees well with values published in literature. The methodology of determining the segregation index and the local mesomixing times in the flow is introduced, followed by the presentation of selected results.
Keywords: fluid mechanics, mixing, laser induced flourescence method
Published: 01.06.2012; Views: 1123; Downloads: 40
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