Wyniki wyszukiwania - BazTech

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Numerical Analysis Of Mixing Under Low And High Frequency Pulsations At Serpentine Micromixers

Malecha Z. M., Malecha K.

Chemical and Process Engineering

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2014

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Vol. 35, nr 3

369--385

EN

The numerical investigation of the mixing process in complex geometry micromixers, as a function of various inlet conditions and various micromixer vibrations, was performed. The examined devices were two-dimensional (2D) and three-dimensional (3D) types of serpentine micromixers with two inlets. Entering fluids were perturbed with a wide range of the frequency (0 – 50 Hz) of pulsations. Additionally, mixing fluids also entered in the same or opposite phase of pulsations. The performed numerical calculations were 3D to capture the proximity of all the walls, which has a substantial influence on microchannel flow. The geometry of the 3D type serpentine micromixer corresponded to the physically existing device, characterised by excellent mixing properties but also a challenging production process (Malecha et al., 2009). It was shown that low-frequency perturbations could improve the average mixing efficiency of the 2D micromixer by only about 2% and additionally led to a disadvantageously non-uniform mixture quality in time. It was also shown that high-frequency mixing could level these fluctuations and more significantly improve the mixing quality. In the second part of the paper a faster and simplified method of evaluation of mixing quality was introduced. This method was based on calculating the length of the contact interface between mixing fluids. It was used to evaluate the 2D type serpentine micromixer performance under various types of vibrations and under a wide range of vibration frequencies.

2

Viscous flow modeling using the vortex particles method

Kudela H., Malecha Z. M.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2009

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Vol. 13, No 1-2

15-32

EN

The vortex particle method is an easy and attractive tool to analyze flow phenomena by investigating vorticity fields and the generation of vorticity at solid walls. The vorticity generation at the walls and its introduction to the flow is of fundamental significance for understanding such phenomena as transition to turbulence, boundary layer separation in an eruptive way, and Hortex structures regeneration. In the present study the vortex-in-cell usefulness of the method has been tested using a variety of simple test problems: the Poiseuille flow, the second Stokes problem, the cavity, the backward step flow, the vortex dipole interaction with the wall, and the flow past a square cylinder in the vicinity of a wall in order to illustrate the correctness and usefulness of the Hortex particle method.

3

Investigation of unsteady vorticity layer eruption induced by vortex patch using vortex particles method

Kudela H., Malecha Z. M.

Journal of Theoretical and Applied Mechanics

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2007

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Vol. 45 nr 4

785-800

EN

The study of eruption of the vortex boundary layer phenomenon due to motion of the patch of vorticity above the wall is presented here. The vortex particle method is chosen to investigate the phenomenon. It shows the eruptive character of the vortex induced boundary layer. Such visualization is possible through the use of the vortex particle method. Description of the numerical method is given. The obtained numerical results are confronted with the numerical and analytical data of other researchers, conforming to a great extent wit h the conclusions.

PL

W pracy przedstawiono wyniki badań numerycznych zjawiska erupcji warstwy wirowej wywołanej przejściem skoncentrowanej struktury wirowej w pobliżu ściany. Do badań wybrano metodę cząstek wirowych. Pokazano erupcyjny charakter warstwy przyściennej indukowanej przez łatę wirową. Przedstawiono dokładny opis prezentowanej metody numerycznej. Omówiono mechanizm formowania się osobliwości w warstwie przyściennej. Wyniki numeryczne skonfrontowano z wynikami badań analityczno-numerycznymi innych badaczy. Przedstawione wyniki numeryczne dobrze potwierdziły hipotezy dotyczące natury erupcji warstwy. Zweryfikowały tym samym niezwykłą przydatność do badania tego typu zjawisk metody cząstek wirowych.