Investigation of Mixing Characteristics in Simple Fluid Flow Systems

Dr. Prahlad Singh

doi:10.71097/IJTAS.v8.i12.1287

Investigation of Mixing Characteristics in Simple Fluid Flow Systems

Author(s)	Dr. Prahlad Singh
Country	India
Abstract	Efficient fluid mixing is a key necessity in multiple engineering systems such as chemical reactors, heat exchangers, biomedical devices, microfluidic platforms, water treatment units, and process intensification equipment. In many such applications, full or near-full mixing is needed within limited residence times and without high energy demand. Active mixing methods operate by moving parts, external fields, and the use of periodic forcing, while passive mixing methods allow improved transport based only on geometric modification of the flow domain (i.e., only through some form of distortion). Passive techniques are attractive because they are compact, low cost, mechanically simple, and more manageable or easy to scale or insert into existing systems as required. This work is an attempt to investigate the improvement of the composition in fluid mixing of these systems by integrating passive flow structures such as baffles, ribs, staggered obstacles, staggered cylindrical posts, helical inserts, and groove-based surface perturbations. We propose a unified framework that examines how passive structures impact mixing efficiency, pressure drop, vortex formation, residence time distribution, and finally, scalar homogenization in such systems. This work investigates the processes through which passive structures modify flow forms, generate secondary flows, facilitate stretching and folding of fluid interfaces, and increase cross-stream migration. Because of the heterogeneity with Reynolds number limits, both laminar and transitional flow regimes are addressed. A two-dimensional and quasi-three-dimensional conceptual analysis is performed to compare representative simple channel configurations: one with a smooth straight channel, the other with a baffled channel, the last with staggered cylindrical posts, and the last with angled surface grooves or twisted inserts. Mixing is assessed by combining the concentration variance decay factor, the mixing index, and the qualitative flow topology analysis. The pressure penalties are considered together with the mixing gains according to the trade-off of the hydraulic efficiency to homogenization. The results showed that with passive structures mixing can be enhanced much more in otherwise weakly mixed simple flow systems. Among the geometries investigated, staggered and asymmetric geometries result in the largest enhancement since they disturb flow symmetry, generate recirculation regions, and systematically reorient scalar gradients. Groove-based and helical structures are most successful where continuous secondary motion can be generated, whereas blunt baffles are favorable for vigorous local mixing but can lose even more pressure. Passive flow structures, when controlled based on geometry, spacing, blockage ratio, and operating Reynolds number, are expected to be very effective in compact mixing enhancement. The proposed performance-based design approach seeks the optimal composition with the tradeoffs on mixing efficiency, manufacturability, fouling resistance, and pumping requirements. Results provide the basis for designing improved mixing flow systems on small scale and large scale.
Keywords	passive mixing, fluid dynamics, flow structures, baffles, microfluidics, channel flow, scalar transport, pressure drop, secondary flow, Reynolds number.
Published In	Volume 8, Issue 12, December 2017
Published On	2017-12-05
Cite This	Investigation of Mixing Characteristics in Simple Fluid Flow Systems - Dr. Prahlad Singh - IJTAS Volume 8, Issue 12, December 2017. DOI 10.71097/IJTAS.v8.i12.1287
DOI	https://doi.org/10.71097/IJTAS.v8.i12.1287
Short DOI	https://doi.org/hb2sjc

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Investigation of Mixing Characteristics in Simple Fluid Flow Systems

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