Influence of each cylinder’s contribution on the total effective viscosity of a two-dimensional suspension by a two-way coupling scheme

Naoki Okamura, T. Fukui, M. Kawaguchi, K. Morinishi
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引用次数: 3

Abstract

Einstein’s viscosity formula is sometimes strongly limited for viscosity estimation of suspensions; that is, it is only applicable for low-concentration suspensions in which hydrodynamic interactions are sufficiently negligible. In particular, hydrodynamic interactions between particles (cylinders in two dimensions) should be taken into consideration when finite-size particles are suspended. Therefore, change in the microstructure, i.e., spatial arrangement of particles in the flow field, is important for understanding mechanism of suspension rheology. In order to provide better practical applications for viscosity estimation instead of Einstein’s formula, we investigated the influence of each cylinder’s contribution on the total effective viscosity of a suspension with finite-size cylinders considering the microstructure, especially in terms of cylinder-wall and cylinder-cylinder distances. Two-dimensional pressure-driven flow simulations were performed using the regularized lattice Boltzmann method and a two-way coupling scheme. The rigid circular cylinders suspended in a Newtonian fluid were assumed to be neutrally buoyant and non-Brownian. As a result, we found that both distances between cylinders and cylinder-wall are significant for viscosity estimation. In addition, the effective viscosity can be estimated accurately when the confinement is sufficiently low ( C ≈ 0.04). It can be stated that the microstructure of the suspension is one of the promising factors to estimate and control suspension rheology.
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双向耦合方案下各气缸对二维悬浮液总有效粘度的影响
爱因斯坦的粘度公式有时对悬浮液的粘度估计有很强的限制;也就是说,它只适用于水动力相互作用可以忽略不计的低浓度悬浮液。特别是,当有限大小的颗粒悬浮时,应考虑颗粒(二维圆柱体)之间的水动力相互作用。因此,微观结构的变化,即颗粒在流场中的空间排列,对于理解悬浮液流变机理具有重要意义。为了提供更好的实际应用粘度估计代替爱因斯坦公式,我们研究了每个圆柱体的贡献对悬浮液的总有效粘度的影响,考虑微观结构,特别是在圆柱体-壁和圆柱体-圆柱体距离方面。采用正则晶格玻尔兹曼方法和双向耦合方式进行了二维压力驱动流动模拟。悬浮在牛顿流体中的刚性圆柱体被假定为中性浮力和非布朗性。结果,我们发现气缸和气缸壁之间的距离对粘度估计都很重要。此外,当约束足够低(C≈0.04)时,可以准确地估计有效粘度。由此可见,悬浮液的微观结构是预测和控制悬浮液流变的重要因素之一。
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来源期刊
CiteScore
1.00
自引率
12.50%
发文量
2
期刊介绍: Journal of Fluid Science and Technology (JFST) is an international journal published by the Fluids Engineering Division in the Japan Society of Mechanical Engineers (JSME). JSME had been publishing Bulletin of the JSME (1958-1986) and JSME International Journal (1987-2006) by the continuous volume numbers. Considering the recent circumstances of the academic journals in the field of mechanical engineering, JSME reorganized the journal editorial system. Namely, JSME discontinued former International Journals and projected new publications from the divisions belonging to JSME. The Fluids Engineering Division acted quickly among all divisions and launched the premiere issue of JFST in January 2006. JFST aims at contributing to the development of fluid engineering by publishing superior papers of the scientific and technological studies in this field. The editorial committee will make all efforts for promoting strictly fair and speedy review for submitted articles. All JFST papers will be available for free at the website of J-STAGE (http://www.i-product.biz/jsme/eng/), which is hosted by Japan Science and Technology Agency (JST). Thus papers can be accessed worldwide by lead scientists and engineers. In addition, authors can express their results variedly by high-quality color drawings and pictures. JFST invites the submission of original papers on wide variety of fields related to fluid mechanics and fluid engineering. The topics to be treated should be corresponding to the following keywords of the Fluids Engineering Division of the JSME. Basic keywords include: turbulent flow; multiphase flow; non-Newtonian fluids; functional fluids; quantum and molecular dynamics; wave; acoustics; vibration; free surface flows; cavitation; fluid machinery; computational fluid dynamics (CFD); experimental fluid dynamics (EFD); Bio-fluid.
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