A numerical study of the measurement of elongational viscosity of polymeric fluids in a semihyperbolically converging die

Feigl, Kathleen; Tanner, Franz X.; Edwards, Brian J.; Collier, J. R.

doi:10.1016/j.jnnfm.2003.08.002

Cited by 53 publications

(45 citation statements)

References 27 publications

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“…In a hyperbolic converging channel, the total Hencky strain along the centerline of the channel is determined by the ratio of wide to narrow dimension of the converging channel as ε H =ln (L w / L n ) (Feigl et al 2003). Although, here, we showed the experimental result with a ratio of the condition (L w / L n =10), the effect of total strain on RBCs can be investigated by controlling the ratio of (L w / L n ).…”

Section: Microfluidic Devicementioning

confidence: 99%

Extensional flow-based assessment of red blood cell deformability using hyperbolic converging microchannel

Lee

Yim

Ahn

et al. 2009

Biomed Microdevices

137

136

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The deformability of the red blood cell (RBC), is known to be closely related to microcirculation and diagnosis of specific diseases such as malaria, arterial sclerosis, sepsis, and so on. From the viewpoint of the flow type, conventional methods to measure the cell deformability have exploited simple shear or complex flow field with little focus on extensional flow field. In this paper, we present a new approach to assess cell deformability under the extensional flow field. For this purpose, a hyperbolic converging microchannel was designed, and the cell deformation in the extensional flow region was continuously monitored. It overcomes the limitation of conventional methods by reducing experiment time. As quantified by the degree of deformation, the extensional flow (Deformation Index = 0.51 at 3.0 Pa) was found to be more efficient in inducing cell deformation compared to the shear flow (Deformation Index = 0.29 at 3.0 Pa). This indicates the insufficiency of the existing models that predict the blood damage in artificial organs, which only consider shear flow. Also, this method could detect the heat-induced difference in deformability of RBCs. It provides a new platform to study the clinical effect of RBC deformability under extensional flow, and is expected to contribute the association of several diseases and deformability of RBCs.

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Section: Microfluidic Devicementioning

confidence: 99%

Extensional flow-based assessment of red blood cell deformability using hyperbolic converging microchannel

Lee

Yim

Ahn

et al. 2009

Biomed Microdevices

137

136

View full text Add to dashboard Cite

show abstract

“…This facilitates the measurement of an effective extensional viscosity using a hyperbolic contraction device. Many studies using a range of model fluids and viscoelastic constitutive models have been performed to assess the suitability of converging dies for measuring extensional viscosity, typically by attempting to decouple the viscous and elastic contributions to the measured pressure drop (James & Saringer (1982); Rajagopalan (2000); Feigl et al (2003); Pandey & Lele (2007); Oliveira et al (2008); Wang et al (2010); Sousa et al (2011)). In the computational study of Rajagopalan (2000), for example, the Phan-Thien-Tanner (PTT) model was used to predict the pressure field in the flow through both abrupt and tapered contractions, from which an extensional viscosity was calculated using different analytical techniques and compared against the predicted extensional viscosity for the PTT model in a homogeneous extensional flow.…”

Section: Introductionmentioning

confidence: 99%

Microfluidic extensional rheometry using a hyperbolic contraction geometry

et al. 2013

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Microfluidic devices are ideally suited for the study of complex fluids undergoing large deformation rates in the absence of inertial complications. In particular, a microfluidic contraction geometry can be utilized to characterize the material response of complex fluids in an extensionally-dominated flow, but the mixed nature of the flow kinematics makes quantitative measurements of material functions such as the true extensional viscosity challenging. In this paper, we introduce the 'extensional viscometer-rheometer-on-a-chip' (EVROC), which is a hyperbolically-shaped contractionexpansion geometry fabricated using microfluidic technology for characterizing the importance of viscoelastic effects in an extensionally-dominated flow at large extension rates (λε a 1, where λ is the characteristic relaxation time, or for many industrial processesε a 1 s −1 ). We combine measurements of the flow kinematics, the mechanical pressure drop across the contraction and spatially-resolved flow-induced birefringence, to study a number of model rheological fluids as well as several representative liquid consumer products in

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“…A more detailed methodology for calculating the entropy changes from elongational flow processes is described elsewhere. [37,40] Figure 3(a) and (b) shows the elongational viscosity of salt containing CNA/PEO nanocomposite gels as a function of elongational strain rate at a temperature of 25 8C. It can be observed that elongational viscosity values of all dispersions gradually decrease with increasing the elongational strain rate.…”

Section: Resultsmentioning

confidence: 96%

“…Numerical simulations showed that h ef provides a good approximation of h e , [40] for which reason in this study we consider h e ¼ h ef . The term h e represents the elongational viscosity as given by the elongational rheometer.…”

Section: Resultsmentioning

confidence: 99%

Elongational Rheology of Polymer/Clay Dispersions: Determination of Orientational Extent in Elongational Flow Processes

Stefanescu

Petrovan

Daly

2008

Macro Materials & Eng

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The purpose of the present contribution is to provide an efficient method that would help to quantify the orientational levels occurring in polymer/clay dispersions subjected to elongational flow. The extent of internal orientation developed in salt containing montmorillonite/poly(ethylene oxide) gels is investigated, combining shear and elongational rheology methods. Entropic changes indicate that the strength of the transient network present in each gel affects the orientational ability of clay particles and polymer chains. We found that an increased Hencky strain of the hyperbolic die leads to a higher variation of the calculated entropy of the material.magnified image

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A numerical study of the measurement of elongational viscosity of polymeric fluids in a semihyperbolically converging die

Cited by 53 publications

References 27 publications

Extensional flow-based assessment of red blood cell deformability using hyperbolic converging microchannel

Extensional flow-based assessment of red blood cell deformability using hyperbolic converging microchannel

Microfluidic extensional rheometry using a hyperbolic contraction geometry

Elongational Rheology of Polymer/Clay Dispersions: Determination of Orientational Extent in Elongational Flow Processes

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