Experiments on the Laminar/Turbulent Transition of Liquid Flows in Rectangular Microchannels

Wibel, Wolf; Ehrhard, Peter

doi:10.1080/01457630802293449

Cited by 31 publications

(9 citation statements)

References 17 publications

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“…Furthermore, secondary flows might occur at the edges of the rectangular channel. These processes might influence the velocity of volume elements near the interfaces and even lead to a transition from a laminar to a turbulent flow regime near the walls . Turbulence at the packed bed/liquid volume interface would increase mixing and mass transport to and from the reactive layer, reducing the boundary layer and creating a steeper velocity profile.…”

Section: Microreactor and Mathematical Modelmentioning

confidence: 99%

Evaluation of a Microreactor for Flow Biocatalysis by Combined Theory and Experiment

et al. 2020

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The operation of enzyme cascades in microfluidic devices is a current field of research that promises manifold applications in biocatalysis. For an optimization of flow biocatalysis systems it is desirable to model the reactor in silico in order to enable a better understanding and thus an economic optimization of the reaction systems. However, due to their high complexity, it is still difficult to simulate coupled enzyme reactions. We here describe a new model for a plug flow reactor consisting of a porous bed of compact uniform particles functionalized with an immobilized ketoreductase (Gre2) which is overflown by a mobile phase containing the enzymatic NADPH cofactor regeneration system based on glucose dehydrogenase (GDH). By studying different flow rates, lengths and layer thicknesses of the catalytic bed, we show that the synergy of experiment and mathematical modeling can optimize the space-time yields of the reaction system.

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Section: Microreactor and Mathematical Modelmentioning

confidence: 99%

Evaluation of a Microreactor for Flow Biocatalysis by Combined Theory and Experiment

et al. 2020

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“…They discuss profiles of the mean axial velocity, of the axial and transversal velocity fluctuations, and reported good agreement with findings known for macroscopic channels. Quite recently Wibel and Ehrhard [6] in their very careful microPIV study of velocity fluctuations confirmed that the laminar/turbulent transition in 133µm channels occurs in the range 1900 ≤ Re ≤ 2220, in reasonable agreement with macroscopic findings. Moreover, the profiles of the turbulent quantities are reported in good agreement with findings within macroscopic channels.…”

Section: Introductionsupporting

confidence: 56%

“…Only quite recently it appeared possible to acquire detailed information on the temporary velocity flow fields within micro channel. Time-dependent measurements of the velocity field within microchannels by means of the microPIV technique have been performed to access the laminar/turbulent transition range [5][6][7][8]. These measurements, in principle, are able to resolve not only the integral information on the laminar/turbulent transition, they can, moreover, provide local information on both mean and fluctuating velocity contributions.…”

Section: Introductionmentioning

confidence: 99%

“…The design and optimisation of microfluidic devices is usually based on our knowledge gained for macro scale hydrodynamics. However, it can be expected that small channel hydrodynamics has to be reconsidered in different contexts: relative large surface area can be responsible for delayed (or accelerated) laminar-turbulent transition [1][2][3][4][5][6][7][8]; wall roughness becomes elevated relative to small channel size and may influence laminar-turbulent transition [9]; appropriate wall corrugation can be used to activate flow instability and effectively diminish critical Reynolds number [10]. In spite of the existence of numerous experimental and theoretical investigations, a number of principal problems related to laminar-turbulent transition in micro scales are not fully resolved.…”

Section: Introductionmentioning

confidence: 99%

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Turbulence in Microchannels

Kowalewski¹,

Błoński²,

Pan³

SpringerReference

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ABSTRACT. Fluid mechanics in small channels, i.e. channels of micrometer size, is dominated by surface effects and often exhibits striking differences of flow characteristics when compared with macro scale. One of important microfluidic problems is flow destabilization and occurrence laminarturbulent transition. In this paper we describe our experimental and numerical attempts to understand growth of flow instabilities and development of turbulent structures in small channels. In the first configuration flow of water through 1mm long and 0.4mm high microchannel formed between two planes is investigated varying Reynolds number from 1000 to 6770. Fluorescent traces are used for flow visualization and microPIV acquisition of temporary velocity fields. The microPIV data are used to evaluate turbulent flow characteristics. Our experimental study shows that destabilization of flow in such a micro-channel does not necessarily occurs when it is usually expected. Nearly laminar flow structure is present within the channel even for the highest investigated flow Reynolds number. These findings are confirmed by numerical simulation performed using finite volume code. On the other hand it appears possible to achieve unstable flow pattern even for quite low Reynolds number flow regime by proper modification of the channel walls. In the second experimental and numerical study we demonstrate that appropriately chosen wall waviness of the micro-channel may lead to flow destabilization already at quite low flow Reynolds number (~100).

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“…Przykładowa siatka do wyznaczania współczynnika Coriolisa składająca się z 1000 trójkątów Na podstawie obliczeń numerycznych MEB oraz aproksymacji otrzymanych wyników wyznaczono wzór określający współczynnik Coriolisa w funkcji stosunku wysokości przewodu prostokątnego H do jego podstawy A: Na rysunku 5. przedstawiono graficzne porównanie funkcji współczynnika Coriolisa REC z rozwiązaniem metody brzegowych równań całkowych. Wzór (12) można również stosować w mikroprzepływach [12][13][14]…”

Section: Określenie Wzorów Opisujacych Współczynnik Coriolisa W Przewunclassified

Algorytm wyznaczania współczynnika Coriolisa przepły-wów laminarnych w kanałach prostokątnych metodą elementów brzegowych

Janusz¹

2012

ZNPRzBiIŚ

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W publikacji wyznaczono zależność współczynnika Coriolisa przepływów laminarnych w przewodach prostokątnych całkowicie wypełnionych płynem w zależności od stosunku wysokości do podstawy kanału. Pola prędkości zostały wyznaczone metodą elementów brzegowych (MEB). W celu wykonania symulacji napisano autorski program komputerowy LaminarFlow1D oraz przeprowadzono walidację metody na podstawie znanych rozwiązań teoretycznych.

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Experiments on the Laminar/Turbulent Transition of Liquid Flows in Rectangular Microchannels

Cited by 31 publications

References 17 publications

Evaluation of a Microreactor for Flow Biocatalysis by Combined Theory and Experiment

Evaluation of a Microreactor for Flow Biocatalysis by Combined Theory and Experiment

Turbulence in Microchannels

Algorytm wyznaczania współczynnika Coriolisa przepły-wów laminarnych w kanałach prostokątnych metodą elementów brzegowych

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