Numerical investigation of multiscale lateral microstructures enhancing passive micromixing efficiency via secondary vortex flow

Abstract

Passive micromixing can efficiently mix laminar flows through molecular and convective diffusion. Microstructures are expected to be efficient, easily integrated into micromixers, and suitable for micromixers over a wide range of Re. This paper presents the enhancement effects of the multiscale lateral microstructures on the flow field characteristics and mixing efficiency through numerical simulations at Re = 0.01–50. Inspired by the regulation of lateral microstructures on the local flow field, cross-scale staggered baffles (CSBs) were established and applied in typical passive micromixers. For low- Re conditions, the paired trapezoidal microstructures (PTMs) of the CSBs improved the mixing effect by increasing the local streamline tortuosity. For high- Re conditions, the PTMs of CSBs increased the number of expanding vortices in the microchannel, which could increase the size of the fluid interfaces, and an optimal mixing index with relatively little pressure drop was achieved. Moreover, the CSBs were applied to the serpentine curved channel, which caused large expanding vortices on the inner side of the curved channel, and then the state of the Dean vortices on the cross section of the curved channel changed. Therefore, compared with the conventional micromixer channel structure, lateral microstructures regulate the local flow field through the enhancement of the streamlines and the secondary flow effects, and lateral microstructures have great potential to improve the mixing efficiency over a wide range of Re.

A Review of Pressure Drop and Mixing Characteristics in Passive Mixers Involving Miscible Liquids

“…Total Mesh Smallest Element, μm Chen et al [74] 155,794 5 Amar et al [77] 643,203 6 Mahmud et al [83] 7.54 × 10 5 20 Okuducu and Aral [78] 1.45 × 10 6 5 Tripathi et al (a) [84] 1,635,434 11 Niu et al [32] 62,207 20 Yuan et al [87] 3.87 × 10 6 5 nted from the literature data available in the tigations. However, the number of grid eledomain is crucial for a proper mixing predicelected for presenting the comparison of MI t grid elements were first tested based on the s that the grid resolutions for the Category 3 f the Category 2, except for Niu et al [32], in h coarser than the others. numerical studies by different authors.…”

“…Mahmud et al [83] (HCM); resented from the literature data available in the nvestigations. However, the number of grid eleatial domain is crucial for a proper mixing predicnts selected for presenting the comparison of MI erent grid elements were first tested based on the shows that the grid resolutions for the Category 3 se of the Category 2, except for Niu et al [32], in much coarser than the others. r the numerical studies by different authors.…”

“…Total Mesh Smallest Element, μm Chen et al [74] 155,794 5 Amar et al [77] 643,203 6 Mahmud et al [83] 7.54 × 10 5 20 Okuducu and Aral [78] 1.45 × 10 6 5 Tripathi et al (a) [84] 1,635,434 11 Niu et al [32] 62,207 20 Yuan et al [87] 3.87 × 10 6 5 In Table 6, MI values have been presented from the literature data available in the published literature from numerical investigations. However, the number of grid ele ments or grid resolutions across the spatial domain is crucial for a proper mixing predic tion (K Sommer [98]).…”

“…Total Mesh Smallest Element, μm Chen et al [74] 155,794 5 Amar et al [77] 643,203 6 Mahmud et al [83] 7.54 × 10 5 20 Okuducu and Aral [78] 1.45 × 10 6 5 Tripathi et al (a) [84] 1,635,434 11 Niu et al [32] 62,207 20 Yuan et al [87] 3.87 × 10 6 5…”

Mixing Performance Analysis and Optimal Design of a Novel Passive Baffle Micromixer

“…The single-channel micromixer has the advantages of a simple structure, low processing cost, and small pressure drop, and is most widely used in passive micromixers [5]. Commonly used single-channel micromixers include T-type [6], Y-type [7], sawtooth-type [8], square-wave-type [9], curved-channel-type [10,11], spiral-channel-type [12] and twisted-channel-type [13] etc. Because the T-type micromixer has a large number of baffles, the fluid flow path is longer, the vortex intensity is stronger, and it has a better mixing efficiency.…”