Characterization of Laminar Transient Flow Regimes and Mixing in T-shaped Micromixers

Dreher, Simon; Kockmann, Norbert; Woias, Peter

doi:10.1080/01457630802293480

Cited by 147 publications

(98 citation statements)

References 15 publications

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“…Finally, a mention should be made of a series of computational and experimental studies [32][33][34], where, in particular, some flow regimes in T-shaped microchannels were calculated. A number of characteristic flow regimes were found, and the flow structure in them were studied.…”

Section: Fluid Mixing At Moderate Reynolds Numbersmentioning

confidence: 99%

Modeling and Optimization of Y-Type Micromixers

Rudyak

Минаков

2014

Micromachines

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A trend in the global technological progress in the last few decades is the development of microsystem technology, microelectromechanical systems and corresponding technologies. Fluid mixing is an extremely important process widely used in various microfluidic devices (chemical microreactors, chemical and biological analyzers, drug delivery systems, etc.). To increase the mixing rate, it is necessary to use special devices: micromixers. This paper presents the results of a hydrodynamic simulation of Y-shaped micromixers. Flows are analyzed for both low and moderate Reynolds numbers. The passive and active mixers are considered. The dependence of the mixing efficiency on the Reynolds and Péclet numbers, as well as the possibility of using the hydrophobic and ultra-hydrophobic coatings is analyzed. Five different flow regimes were identified: (1) stationary vortex-free flow (Re < 5); (2) stationary symmetric vortex flow with two horseshoe vortices (5 < Re < 150); (3) stationary asymmetric vortex flow (150 < Re < 240); (4) non-stationary periodic flow (240 < Re < 400); and (5) stochastic flow (Re > 400). The maximum mixing efficiency was obtained for stationary asymmetric vortex flow.

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Section: Fluid Mixing At Moderate Reynolds Numbersmentioning

confidence: 99%

Modeling and Optimization of Y-Type Micromixers

Rudyak

Минаков

2014

Micromachines

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“…This clearly leads to a significantly larger mixing than in the previous regimes. If the Reynolds number is further increased, the flow may become unsteady (see, e.g., Bothe et al, 3 Dreher et al, 5 and Galletti et al 6 ). For instance, for square inlet pipes and an outflow pipe width (W o ) to height (H) ratio W o /H = 2 and for fully developed inlet velocity conditions, Engler et al 2 show that the flow is in stratified regime approximately for Re < 50 (based on the outflow hydraulic diameter and mean velocity), in vortex regime for 50 < Re < 150, engulfment starts at Re 150 and the flow is periodic for 240 < Re < 400.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the steady engulfment regime in a three-dimensional T-mixer

Fani¹,

Camarri²,

Salvetti³

2013

Physics of Fluids

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The steady engulfment regime in a fully three-dimensional micro T-mixer is investigated. This regime is of significant interest for applications since it implies high mixing between the flow streams entering the device. Direct numerical simulations are first used to characterize this regime. In particular, the main vortical structures typical of the engulfment regime and their effects on mixing are investigated. Threedimensional linear stability analysis is successively applied to the characterization of the instability leading to the engulfment regime. The critical Reynolds number and the global unstable mode are first computed for a configuration characterized by fully-developed inlet velocity conditions. The sensitivity of this instability to a generic modification of the base flow is then investigated, thanks to the computation of the mode adjoint to the direct unstable one. Finally, this kind of analysis is specialized to investigate the effect of a perturbation of the velocity distribution at the inlet of the T-mixer. Sensitivity analysis shows that non-fully developed inlet velocity conditions lead to an increase of the critical Reynolds number. More generally, the sensitivity maps can be used for the design of control strategies aimed at promoting or inhibiting the engulfment. An example is provided for a control based on blowing/suction through the mixer walls. C 2013 AIP Publishing LLC.

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“…Figure 1, left), three different stationary flow regimes can be observed up to a Reynolds number of about 240 at which time-periodic flow phenomena set in. 14,16 At Reynolds numbers below 40, strictly laminar flow behavior occurs without secondary flow. Then, for 40 \ Re \ 138, the so-called vortex flow regime exhibits secondary flow in form of a double vortex pair.…”

Section: Resultsmentioning

confidence: 99%

Computational analysis of an instantaneous chemical reaction in a T‐microreactor

2009

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in Wiley InterScience (www.interscience.wiley.com).We extend and apply a method for the numerical computation of convective and diffusive mixing in liquid systems with very fast irreversible chemical reaction to the case of unequal diffusivities. This approach circumvents the solution of stiff differential equations and, hence, facilitates the direct numerical simulation of reactive flows with quasi-instantaneous reactions. The method is validated by means of a neutralization reaction which is studied in a T-shaped micromixer and compared with existing experimental LIF-data. Because of their large are-to-volume ratio, microreactors are well suited for fast chemical reactions which are seriously affected by the slow diffusive transport in aqueous media. Numerical computations for different reactor dimensions reveal the fact that, in a dimensionless setting, the obtained conversion is independent of the reactor size, if the flow conditions are the same. This corresponds to an increase of space-time-yield proportional to the square of the inverse scale factor.

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Characterization of Laminar Transient Flow Regimes and Mixing in T-shaped Micromixers

Cited by 147 publications

References 15 publications

Modeling and Optimization of Y-Type Micromixers

Modeling and Optimization of Y-Type Micromixers

Investigation of the steady engulfment regime in a three-dimensional T-mixer

Computational analysis of an instantaneous chemical reaction in a T‐microreactor

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