Fouling Mitigation via Chaotic Advection in a Flat Membrane Module with a Patterned Surface

Abstract

Fouling mitigation using chaotic advection caused by herringbone-shaped grooves in a flat membrane module is numerically investigated. The feed flow is laminar with the Reynolds number (Re) ranging from 50 to 500. In addition, we assume a constant permeate flux on the membrane surface. Typical flow characteristics include two counter-rotating flows and downwelling flows, which are highly influenced by the groove depth at each Re. Poincaré sections are plotted to represent the dynamical systems of the flows and to analyze mixing. The flow systems become globally chaotic as the groove depth increases above a threshold value. Fouling mitigation via chaotic advection is demonstrated using the dimensionless average concentration (c¯w*) on the membrane and its growth rate. When the flow system is chaotic, the growth rate of c¯w* drops significantly compared to that predicted from the film theory, demonstrating that chaotic advection is an attractive hydrodynamic technique that mitigates membrane fouling. At each Re, there exists an optimal groove depth minimizing c¯w* and the growth rate of c¯w*. Under the optimum groove geometry, foulants near the membrane are transported back to the bulk flow via the downwelling flows, distributed uniformly in the entire channel via chaotic advection.

The Effect of the Rotating Disk Geometry on the Flow and Flux Enhancement in a Dynamic Filtration System

“…The performance of a rotary dynamic filtration system is closely related to a secondary flow, such as Taylor vortices created by a high-speed rotation of a rotor, reducing membrane fouling or concentration polarization [ 18 ]. Such a secondary flow in membrane filtration also leads to enhanced mixing and improved fouling resistance via back transport of foulants from the membrane to the bulk flow region [ 27 , 53 ]. In addition, Taylor vortices are also associated with the enhanced shear rate in a dynamic filtration module [ 61 ].…”

“…In fluids engineering applications, patterned surfaces are used as a means to add perturbations to a flow field or to guide a flow to a desired direction, where the detailed flows are affected by the topology and the geometrical parameters of a surface pattern [ 44 , 45 , 46 , 47 ]. In membrane filtration, a large number of studies on patterned solid surfaces or patterned membranes are being conducted to elucidate their influences on antifouling and flux enhancement in crossflow filtration [ 48 , 49 , 50 , 51 , 52 , 53 , 54 ]. Flow and mass transfer characteristics due to various engineered surface features [ 50 ] and bio-mimetic surface patterns [ 51 ] are main concerns of researchers.…”

“…Flow and mass transfer characteristics due to various engineered surface features [ 50 ] and bio-mimetic surface patterns [ 51 ] are main concerns of researchers. In particular, the relative size between a surface pattern and a filtration module plays a key role in mitigating membrane fouling or concentration polarization [ 53 , 54 ]. In a DF system, a rotating disk with specific surface structure, such as radial vanes or perforations used in [ 21 , 28 ], can be used to increase the wall shear rate on the membrane and the permeate flux.…”

Inducing Deep Sweeps and Vortex Ejections on Patterned Membrane Surfaces to Mitigate Surface Fouling

“…Jung et al [ 46 ] found that the particles they studied tended to deposit into the surface valleys and not at the peaks, indicating a conclusion later drawn by Jung and Ahn [ 47 ]: a patterned membrane surface can tremendously reduce surface fouling, given a judicious choice in Reynolds number and pattern depth relative to average particle size. Kim et al [ 48 ] recently offered further confirmation of these dependencies via an alternative approach (i.e., a herringbone-patterned mixer to induce chaotic advection in a flat sheet membrane module).…”