Comparing Phenomenological Models of Shear Thinning of Alkanes at Low and High Newtonian Viscosities

IF 2.9 3区 工程技术 Q2 ENGINEERING, CHEMICAL
Wenhui Li, Vikram Jadhao
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引用次数: 0

Abstract

There is an ongoing debate concerning the best rheological model for fluids sheared in elastohydrodynamic lubrication (EHL) where high pressures lead to a dramatic rise in Newtonian viscosity and high strain rates lead to pronounced shear thinning. Two classes of phenomenological models at the center of this debate are based on the work of Eyring and Carreau. We use intermediate scaling plots and a justification criterion proposed by Gao and Müser in a recent article (Tribol Lett 72(1):16, 2024) to evaluate the fitting of Eyring, Carreau, and Carreau–Yasuda (CY) models to rheological data on the shear thinning of squalane, a model EHL fluid, at 293 K over a wide range of pressures \(P \in (0.1,955)\) MPa that change the Newtonian viscosity \(\eta _0\) of squalane from \(\sim 10\) to \(\sim 10^7\) mPa s. The justification criterion enables a fair comparison of Eyring, Carreau, and CY models that have two, three, and four fitting parameters, respectively. We find that the use of Eyring model to describe shear thinning of squalane is justified over Carreau model and CY model with crossover parameter \(a>1\) for \(\eta _0 > 10^2\) mPa s and \(\eta _0 > 10^3\) mPa s, respectively. The unrestricted CY model produces \(a<1\) in all fits and fares better but is not justified over Eyring for squalane sheared at high Newtonian viscosities \(\eta _0 > 10^4\) mPa s. More importantly, CY models fitted with \(a<1\) fail to produce a physical low-rate asymptotic behavior and an appropriate crossover to Newtonian flow. Our findings show that CY models with \(a > 1\) guarantee a proper description of the crossover from shear thinning to Newtonian zone, and should be the phenomenological model of choice for shear thinning at low pressures. As pressure rises and \(\eta _0\) becomes large (e.g., \(> 10^3\) mPa s for squalane), the use of Eyring model to describe shear thinning is justified.

Abstract Image

比较低牛顿粘度和高牛顿粘度下烷烃剪切稀化的现象学模型
在弹性流体动力润滑(EHL)中,高压会导致牛顿粘度急剧上升,而高应变率则会导致明显的剪切稀化,关于在这种情况下剪切流体的最佳流变学模型一直存在争论。处于这一争论中心的两类现象学模型是基于 Eyring 和 Carreau 的研究成果。我们使用中间缩放图以及 Gao 和 Müser 在最近的一篇文章(Tribol Lett 72(1):16, 2024)中提出的合理性标准,来评估 Eyring、Carreau 和 Carreau-Yasuda (CY) 模型与模型 EHL 流体角鲨烷在 293 K 的剪切稀化流变学数据的拟合情况。我们发现,使用 Eyring、Carreau 和 CY 模型,分别有两个、三个和四个拟合参数。我们发现,对于 \(\eta _0 > 10^2\) mPa s 和 \(\(\eta _0 > 10^3\) mPa s,使用 Eyring 模型描述角鲨烷的剪切稀化比使用交叉参数 \(a>1\) 的 Carreau 模型和 CY 模型更合理。更重要的是,用\(a<1\)拟合的 CY 模型不能产生物理的低速率渐近行为和与牛顿流体的适当交叉。我们的研究结果表明,用(a > 1\ )拟合的CY模型可以保证正确描述从剪切稀化到牛顿区的交叉,应该成为低压下剪切稀化现象学模型的首选。随着压力的升高,\(eta _0\)变得很大(例如,角鲨烷的\(> 10^3\s) mPa s),使用 Eyring 模型来描述剪切变稀是合理的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Tribology Letters
Tribology Letters 工程技术-工程:化工
CiteScore
5.30
自引率
9.40%
发文量
116
审稿时长
2.5 months
期刊介绍: Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.
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