CFD study on laminar mixing at a very low Reynolds number by pitching and heaving a square cylinder

Ortega-Casanova, J.; Chen, Lai

doi:10.1016/j.compfluid.2018.03.068

Cited by 18 publications

(7 citation statements)

References 23 publications

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“…The mixing cost and mixing energy cost were calculated for the chicanes micromixer at different volume flow rates (Table 1) [36][37][38][39]. The highest mixing cost was obtained at low volume flow rates.…”

Section: Pressure Dropmentioning

confidence: 99%

Numerical and Experimental Investigations of a Micromixer with Chicane Mixing Geometry

2018

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A micromixer is a new type of chemical engineering equipment used to intensify the mixing process. This article provides details on flow regimes in microchannels with a complex geometry, such as with chicane mixing geometry. Experiments involving water, ink, and a micro digital camera have determined both the micromixer’s initial mixing zone, and also the streamlines. Computational fluid dynamics (CFD) modelling helped identify the mechanism of stimulating effect; swirling and recirculation were identified as two special cases of the convective mixing process. To characterize the degree of mixing, a function of volume flow rate was proposed. A much higher degree of mixing in vortex flow compared to stratified flow was observed. The relationship between laminar flow and vortices shows a square-law dependence of pressure drop against the volume flow rate. The mixing cost and the mixing energy cost at Reynolds number of 50 are higher for the chicane micromixer than for micromixers without chicanes geometry.

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Section: Pressure Dropmentioning

confidence: 99%

Numerical and Experimental Investigations of a Micromixer with Chicane Mixing Geometry

2018

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“…For example, regarding pulsating flows, the following references, among others, could be referred to Ji et al (2008), Mulcahey et al (2013), Yu et al (2014), Krishnan et al (2016) and Martin et al (2018). Regarding prism motion, some relevant references are: Celik and Beskok (2009), Singh et al (2009), Reyes et al (2015), Kumar Chauhan et al (2016), Sastre and Velazquez (2017), Ortega-Casanova and Lai (2018), Clemente et al (2019) and Valeije et al (2020).…”

Section: Problem Descriptionmentioning

confidence: 99%

Comparison of three-dimensional flow mixing via pulsation and dynamical stirring: application to the mixing of parallel streams at different temperatures

Sastre

Martín

Velázquez

et al. 2021

HFF

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Purpose This paper aims to compare the performance of flow pulsation versus flow stirring in the context of mixing of a passive scalar at moderate Reynolds numbers in confined flows. This comparison has been undertaken in two limits: diffusion can be neglected as compared to convection (very large Peclet) and diffusion and convection effects are comparable. The comparison was performed both in terms of global parameters: pumping power and mixing efficiency and local flow topology. Design/methodology/approach The study has been addressed by setting up a common conceptual three-dimensional problem that consisted of the mixing of two parallel streams in a square section channel past a square section prism. Stirring and pulsation frequencies and amplitudes were changed and combined at an inlet Reynolds number of 200. The numerical model was solved using a finite volume formulation by adapting a series of open-source OpenFOAM computational fluid dynamic (CFD) libraries. For cases with flow pulsation, the icoFoam solver for laminar incompressible transient flows was used. For cases with stirring, the icoDyMFoam solver, which uses the arbitrary Lagrangian–Eulerian method for the description of the moving dynamical mesh, was used to model the prism motion. At the local flow topology level, a new method was proposed to analyze mixing. Time evolution of folding and wrinkling of sheets made up of virtual particles that travel along streak lines was quantified by generating lower rank projections of the sheets onto the spaces spanned by the main eigenvectors of an appropriate space-temporal data decomposition. Findings In the limit when convection is dominant, the results showed the superior performance of stirring versus flow pulsation both in terms of mixing and required pumping power. In the cases with finite Peclet, the mixing parameters by stirring and flow pulsation were comparable, but pulsation required larger pumping power than stirring. For some precise synchronization of stirring and pulsation, the mixing parameter reached its maximum, although at the expense of higher pumping power. At the local flow topology level, the new method proposed to quantify mixing has been found to correlate well with the global mixing parameter. Originality/value A new systematic comparative study of two methods, stirring and pulsation, to achieve mixing of passive scalars in the mini scale for confined flows has been presented. The main value, apart from the conclusions, is that both methods have been tested against the same flow configuration, which allows for a self-consistent comparison. Of particular interest is the fact that it has been found that accurate synchronization of both methods yields mixing parameters higher than those associated to both methods taken separately. This suggests that it is possible to synchronize mixing methods of a different nature to achieve optimum designs. The new theoretical method that has been proposed to understand the mixing performance at the local level has shown promising results, and it is the intention of the authors to test its validity in a broader range of flow parameters. All these findings could be taken as potential guidelines for the design of mixing processes in the mini scale in the process industry.

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“…Some researchers calculate the mixing energy cost (MEC) by combining the pressure load and the MP to check the effectiveness of a micromixer [26][27][28]:…”

Section: Governing Equations and Computational Proceduresmentioning

confidence: 99%

Effects of Channel Wall Twisting on the Mixing in a T-Shaped Micro-Channel

Kang

2019

Micromachines

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A new design scheme is proposed for twisting the walls of a microchannel, and its performance is demonstrated numerically. The numerical study was carried out for a T-shaped microchannel with twist angles in the range of 0 to 34π. The Reynolds number range was 0.15 to 6. The T-shaped microchannel consists of two inlet branches and an outlet branch. The mixing performance was analyzed in terms of the degree of mixing and relative mixing cost. All numerical results show that the twisting scheme is an effective way to enhance the mixing in a T-shaped microchannel. The mixing enhancement is realized by the swirling of two fluids in the cross section and is more prominent as the Reynolds number decreases. The twist angle was optimized to maximize the degree of mixing (DOM), which increases with the length of the outlet branch. The twist angle was also optimized in terms of the relative mixing cost (MC). The two optimum twisting angles are generally not coincident. The optimum twist angle shows a dependence on the length of the outlet branch but it is not affected much by the Reynolds number.

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CFD study on laminar mixing at a very low Reynolds number by pitching and heaving a square cylinder

Cited by 18 publications

References 23 publications

Numerical and Experimental Investigations of a Micromixer with Chicane Mixing Geometry

Numerical and Experimental Investigations of a Micromixer with Chicane Mixing Geometry

Comparison of three-dimensional flow mixing via pulsation and dynamical stirring: application to the mixing of parallel streams at different temperatures

Effects of Channel Wall Twisting on the Mixing in a T-Shaped Micro-Channel

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