The Effect of Inertia on the Flow and Mixing Characteristics of a Chaotic Serpentine Mixer

Abstract

As an extension of our previous study, the flow and mixing characteristics of a serpentine mixer in non-creeping flow conditions are investigated numerically. A periodic velocity field is obtained for each spatially periodic channel with the Reynolds number (Re) ranging from 0.1 to 70 and the channel aspect ratio from 0.25 to one. The flow kinematics is visualized by plotting the manifold of the deforming interface between two fluids. The progress of mixing affected by the Reynolds number and the channel geometry is characterized by a measure of mixing, the intensity of segregation, calculated using the concentration distribution. A mixer with a lower aspect ratio, which is a poor mixer in the creeping flow regime, turns out to be an efficient one above a threshold value of the Reynolds number, Re = 50. This is due to the combined effect of the enhanced rotational motion of fluid particles and back flows near the bends of the channel driven by inertia. As for a mixer with a higher aspect ratio, the intensity of segregation has its maximum around Re = 30, implying that inertia does not always have a positive influence on mixing in this mixer.

An easily fabricated three-dimensional threaded lemniscate-shaped micromixer for a wide range of flow rates

“…Through this way, a chaotic flow is induced, which enhances the mixing efficiency. 40 In most of the previous passive mixers, where vortices play a key role in increasing the mixing efficiency, vortex regions were confined to a specific segment of the channel 43,44 while in the micromixers presented in this work, mixing process occurs throughout the structure. Moreover, in designs where the Dean vortices are responsible for increasing the efficiency, the channel length was normally limited due to the lack of fabrication space on a 2D plane.…”

Design Optimization for a Microfluidic Crossflow Filtration System Incorporating a Micromixer

“…Due to the apex location changing alternatingly in a periodic unit, two cross-sectional flow portraits are generated in the first and second half cycles and they intersect one another when projected onto the same plane. According to the linked twisted maps (LTM) framework [48], the two flow portraits satisfy the necessary condition for the creation of chaotic advection [49,50]. Figure 3 depicts cross-sectional velocity vectors projected onto planes normal to the z direction.…”

Computational Design and Experimental Validation of SAR Mixers

“…The time steps for each simulation are appropriately adjusted so as to limit the necessary number of calculation steps needed by the time-consuming transient simulations. For pulse tracer input method, E(t) is given by equation (6). When the mixing performance of flow systems of different sizes or flow conditions is to be compared, a normalized RTD function, E (θ), is used instead of E (t).…”

“…Micromixers can be classified into two categories, active and passive, depending on their mixing principle [5]. In active micromixers, active controls over the flow field are introduced to manipulate fluids to be mixed by using moving parts, acoustics waves or electro-magnetic fields or varying pressure gradient [6]. In the case of passive mixer, the mixing enhancement can be achieved by carefully designing the channel so as to create vortices and disturb the flow stability which, in turn, leads to the chaotic flow regime.…”