Experimental observations of flow instabilities and rapid mixing of two dissimilar viscoelastic liquids

Gan, Hiong Yap; Lam, Yee Cheong

doi:10.1063/1.4768667

Cited by 4 publications

(12 citation statements)

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“…Chaotic flows of viscoelastic, polymeric fluids were demonstrated in a micro-channel by exploiting their non-linear behavior through the introduction of curved streamlines 4 and sudden changes in geometry. 6 Viscoelastic chaotic flows are deterministic but not easily predictable; this is the hallmark of chaos, in the sense that minute differences in initial conditions would lead to significantly different flow states. Characterization of these non-linear complex flows requires chaos analysis.…”

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confidence: 99%

“…Nonetheless, noninertia driven chaotic flows can be induced in micro-channels by other forces such as acoustic forces, 1 interfacial tension 2,3 and viscoelastic forces. [4][5][6] With the addition of a trace amount of polymers, a fluid becomes viscoelastic, exhibiting both viscous and elastic characteristics. Chaotic flows of viscoelastic, polymeric fluids were demonstrated in a micro-channel by exploiting their non-linear behavior through the introduction of curved streamlines 4 and sudden changes in geometry.…”

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confidence: 99%

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Chaos analysis of viscoelastic chaotic flows of polymeric fluids in a micro-channel

2015

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Many fluids, including biological fluids such as mucus and blood, are viscoelastic. Through the introduction of chaotic flows in a micro-channel and the construction of maps of characteristic chaos parameters, differences in viscoelastic properties of these fluids can be measured. This is demonstrated by creating viscoelastic chaotic flows induced in an H-shaped micro-channel through the steady infusion of a polymeric fluid of polyethylene oxide (PEO) and another immiscible fluid (silicone oil). A protocol for chaos analysis was established and demonstrated for the analysis of the chaotic flows generated by two polymeric fluids of different molecular weight but with similar relaxation times. The flows were shown to be chaotic through the computation of their correlation dimension (D2) and the largest Lyapunov exponent (λ1), with D2 being fractional and λ1 being positive. Contour maps of D2 and λ1 of the respective fluids in the operating space, which is defined by the combination of polymeric fluids and silicone oil flow rates, were constructed to represent the characteristic of the chaotic flows generated. It was observed that, albeit being similar, the fluids have generally distinct characteristic maps with some similar trends. The differences in the D2 and λ1 maps are indicative of the difference in the molecular weight of the polymers in the fluids because the driving force of the viscoelastic chaotic flows is of molecular origin. This approach in constructing the characteristic maps of chaos parameters can be employed as a diagnostic tool for biological fluids and, more generally, chaotic signals.

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confidence: 99%

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confidence: 99%

Chaos analysis of viscoelastic chaotic flows of polymeric fluids in a micro-channel

2015

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“…With the advancement of miniaturization techniques and increasing usage of microfabrication technology in the industry from the 1980s, flows in planar microchannels were the next focus of many studies (Rodd et al 2005a, 2007, Oliveira et al 2007, Gan et al 2007, Lam et al 2009, Afonso et al 2011, Gan and Lam 2012 With a saturation of research on contraction flows, Rodd et al (2005aRodd et al ( , 2007 was one of the pioneers to investigate the flows of viscoelastic liquids past a contraction-expansion micro-channel (16:1:16 contraction-expansion ratio, 400µm:…”

Section: Micro-channel Contraction Flowsmentioning

confidence: 99%

“…In a separate publication, Gan and Lam (2012) presented a De ratio -De main operating space (see Figure 2-11) which categorized the flow transitions and mixing efficiencies of the 3-stream flow. They highlighted that the discontinuity in viscoelastic energy i.e.…”

Section: Contraction And/or Expansion Flowsmentioning

confidence: 99%

“…As such, the manifestations of viscoelastic turbulence can be found in rotating and curvilinear flows, cross-slot flows, and contraction and/or expansion flows etc. (Liu and Steinberg 2010, Jun and Steinberg 2011, Tatsumi et al 2011, Haward et al 2012, Bonn et al 2011, Gan and Lam 2012, and no experimental findings on its occurrence in straight channel flows have been reported.…”

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Characteristics and origins of viscoelastic turbulence in a 3-stream contraction-expansion micro-channel

Tai¹

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At low Reynolds number (Re < 1), the flow of viscous liquids e.g. water, is laminar. An aqueous solution e.g. water becomes viscoelastic when a small amount of polymer additives (< 1 wt%) is added to it; its flow behavior can become drastically different and turbulent i.e. viscoelastic turbulence. This phenomenon has gained increasing attention because it violates the conventional school of thought i.e. high-Re criteria, for creating chaos and disorder in a fluid dynamics system. As the polymer molecules are invisible, the indirect deduction of molecular behavior via motion analyses of tracer additives has been adopted as the main investigative approach in viscoelastic turbulent flows. Based on this approach, reported works attribute viscoelastic turbulence to the release of elastic energy by the polymer molecules, which had been extended due to strong velocity gradients in the flow field. The release of energy occurs over a range of time scales which is dependent on the characteristic time scales of the molecules and bulk viscoelastic liquid. Although the reported characteristic time scales vary significantly, their effects on the structure of the viscoelastic turbulent flow field have not been investigated. Despite the significant number of investigations based on the conventional approach, the underlying mechanisms in viscoelastic turbulence remains elusive; several outstanding questions on viscoelastic flows remain unresolved e.g. the high Weissenberg number problem, and the drag reduction theory debate. "How do the polymer molecules change the flow field so drastically when they are only present in minute amounts?". This fundamental question has yet to be clearly answered. Although fluorescent-tagged DNA molecules are commercially available, because I would like to express my heartfelt gratitude to my supervisor, Professor Lam Yee Cheong. His advice and guidance has been invaluable throughout my Ph.D. study. In addition, I would like to thank NTU for the funding and support, which made this research work possible. The excellent research environment has greatly facilitated the experimental work required in this study. I would also like to thank all staffs of Materials Laboratory 1, Thermal and Fluids Laboratory and Precision Engineering Laboratory for their support and help in the management and usage of facilities. Most importantly, I wish to thank my parents and friends for their unwavering support. Blank

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Modeling and simulation of a single-mode multiphase Richtmyer–Meshkov instability with a large Stokes number

et al. 2019

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This study focuses on the effects of a large Stokes number (St) on the perturbation growth in linear and nonlinear stages of a Richtmyer–Meshkov instability (RMI) in a gas-particle system, which to the best of our knowledge has not been previously reported. A linear growth model is developed by linear stability analysis and numerically verified by the compressible multiphase particle-in-cell (CMP-PIC) method. Additionally, the RMI growth characteristics in the nonlinear stage are also investigated by CMP-PIC. For the linear growth model, two major differences characterize the effects of a large St. The first one is that an RMI with a large St, which performs significantly different from the RMI with a small St, is induced and driven only by the density difference of the gas-phase and totally independent of particle density. Second, due to the significant momentum coupling effects between gas and particle phases, which govern the gas-particle flow, the growth rate experiences exponential decay, even in the linear RMI stage. The decay behavior performs markedly different from any previous RMI models, especially those of the original single-phase RMI and the gas-particle RMI with a small St. Notably, in the nonlinear stage of the RMI with a large particle volume fraction, the decay effects are much more pronounced and lead to a fall in the growth rate to almost zero, which is not found in any other type of RMI. These findings offer the possibility to develop a new method to control the development of hydrodynamic instability.

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Experimental observations of flow instabilities and rapid mixing of two dissimilar viscoelastic liquids

Cited by 4 publications

References 32 publications

Chaos analysis of viscoelastic chaotic flows of polymeric fluids in a micro-channel

Chaos analysis of viscoelastic chaotic flows of polymeric fluids in a micro-channel

Characteristics and origins of viscoelastic turbulence in a 3-stream contraction-expansion micro-channel

Modeling and simulation of a single-mode multiphase Richtmyer–Meshkov instability with a large Stokes number

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