Use of Surface Corrugations for Energy-Efficient Chaotic Stirring in Low Reynolds Number Flows

Abstract

We demonstrate that an intensive stirring can be achieved in laminar channel flows in a passive manner by utilizing the recently discovered instability waves which lead to chaotic particle movements. The stirring is suitable for mixtures made of delicate constituents prone to mechanical damage, such as bacteria and DNA samples, as collisions between the stream and both the bounding walls as well as mechanical mixing devices are avoided. Debris accumulation is prevented as no stagnant fluid zones are formed. Groove symmetries can be used to limit stirring to selected parts of the flow domain. The energy cost of flows with such stirring is either smaller or marginally larger than the energy cost of flows through smooth channels.

On the use of transpiration patterns for reduction of pressure losses

“…If the maximum possible propulsive force has been achieved, the only way to improve the system performance is to expend energy on drag reduction. It is worth noting the recent emergence of a new direction of such research with the reduction of the energy cost associated with stirring being the main objective (Gepner & Floryan 2020).…”

“…It is known that short wavelength longitudinal grooves (riblets) can reduce drag by forcing the stream to lift above the grooves (Walsh 1980, 1983). It is also known that long wavelength longitudinal grooves can lead to drag reduction through changes in the distribution of the bulk flow (Szumbarski, Blonski & Kowalewski 2011, Moradi & Floryan 2013; Mohammadi & Floryan 2013 a , 2014, 2015; Mohammadi, Moradi & Floryan 2015, Chen et al. 2016; DeGroot, Wang & Floryan 2016; Raayai-Ardakani & McKinley 2017; Yadav, Gepner & Szumbarski 2017, 2018).…”

Time‐dependent flows in grooved non‐isothermal channels

“…The development of techniques for mixing intensification is a classical subject [1][2][3] which recently acquired a new direction, that is, intensification of stirring at a reduced energy cost. 4 Meeting this objective requires simultaneous consideration of drag reduction or, at the least, arresting any drag increases which may be potentially associated with intensification of stirring. The mixing of fluids is a two-stage process composed of diffusion overlaid on top of mechanical stirring (advection).…”

“…Stirring promotes mixing in the sense that it leads to stretching and folding of fluid interfaces, increasing concentration gradients and enabling the otherwise slow diffusion to act more rapidly and across shorter distances. To be successful, energy efficient stirring must take advantage of delicate instability processes and chaotic movements [4][5][6][7][8] whose analysis requires the development of very accurate algorithms capable of efficient simulations of flows in a multitude of complex geometric configurations with minimal user involvement. Such algorithms must be able to capture system bifurcations and predict the onset of the formation of secondary flow structures.…”

An algorithm for analysis of pressure losses in heated channels

“…This analysis is focused on the developments of methods suitable for the reduction of frictional drag using combination of groove and heating patterns. Recent results show that the same grooves can be used for generation of the energy‐efficient chaotic stirring 2 . While the interest is in the use of small‐amplitude grooves in order not to reduce the effective conduit cross‐sectional area, their presence brings in the pressure interaction drag.…”