GOALI: Multiscale Modeling of Electro- and Magnetorheological Fluids

GOALI：电流变液和磁流变液的多尺度建模

• 批准号: 0424087
• 负责人: Daniel Klingenberg
• 金额: $ 14万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0424087&HistoricalAwards=false
• 关键词: GOALI; Multiscale; Modeling; Electro; Magnetorheological

ABSTRACT - 0424087Electro- and magnetorheological (ER and MR) fluids are particulate suspensions whose rheological properties are dramatically altered by electric and magnetic fields, respectively. The applied fields also alter the suspension microstructure, causing the formation of particulate columns oriented in the field direction in quiescent suspensions, and the formation of concentrated particulate stripes oriented in the flow direction in sheared suspensions. These structural changes are intimately connected to the rheological phenomena. The formation of particulate columns is known to cause the dramatic rheological changes. The appearance of stripes is associated with the onset of a transient rheological response, where the shear stress slowly increases as the stripes coalesce, coarsen, and densify. ER and MR fluids are being exploited in the development of such applications as shock absorbers, clutches, and brakes, with MR applications recently reaching commercialization. Understanding and modeling the transient structural and rheological behavior is crucial for the design, optimization and control of ER and MR fluids and devices. Particle-level simulations have been valuable for understanding the relationships between particle properties, interactions, and macroscopic behavior. However, these approaches are computationally expensive, and thus ill-suited for modeling the behavior of an entire device. Other modeling strategies must be developed to complement particle-level simulations and overcome their inherent limitations. We have developed a continuum description of the structure evolution in ER suspensions, as characterized by the time and position-dependent particle volume fraction _(x; t). The particle flux is related to the particle contribution to the stress via a momentum balance. Using this two-fluid approach, one predicts the patterns observed experimentally-column formation in quiescent suspensions, and stripe formation in sheared suspensions- without the computational expense of following the motion of individual particles. Although this continuum model can successfully reproduce certain features of structure evolution, assumptions employed for the constitutive behavior limit its predictive power. Most notably, assuming a form for the electrostatic stress appropriate for an isotropic suspension precludes an estimate for the field-induced shear stress and thus the associated rheological transients; and the neglect of nonlocal polarization gives little insight into the long-time transients. The main goal of the proposed work is to combine the strengths of the two modeling approaches to obtain a multiscale description of ER/MR fluids and devices, overcoming the limitations of our prior continuum modeling effort. We will employ particle-level simulations (i.e., Stokesian dynamics simulations) to determine the appropriate constitutive behavior for particle stress and particle flux for use in the continuum model. Employing this constitutive behavior will allow us to probe both the evolution of structure and shear rheology from a continuum perspective. We will also extend a selfconsistent field model of ER fluids to model nonlocal polarization contributions in the continuum model, in order to describe the long-time transient phenomena. The proposed work will yield a complete continuum description of the rheology and mass transport in ER and MR fluids that can be used in the design, optimization and control of ER and MR fluids and devices. Simulation studies will be performed by Klingenberg, Morris, and students, with continuing consultation with Ulicny at General Motors. Experiments for verification will be performed at both UW and GM. GM will also provide experimental results for clutch performance from measurements on a clutch test rig at GM.Intellectual Merit and Broader Impact. The proposed work will specifically benefit the design, optimization and control of sheared ER and MR devices by providing a models for both the rheology and mass transport. Such information is necessary as particle transport appears to be ubiquitous in sheared ER and MR fluids, and impacts the apparent rheology. More generally, the proposed work will benefit suspension mechanics research as we further develop continuum methods for describing the flow of suspensions. The broader impact of this work includes an educational component through the training of undergraduate and graduate students in the technical modeling aspects of this work, as well as the experimental techniques. Results from this work will be available to the scientific community through submission of manuscripts to refereed journals, and presentations at scientific meetings.

摘要：电和磁流变（ER和MR）流体是一种颗粒悬浮液，其流变性能分别在电场和磁场作用下发生显著改变。外加电场还改变了悬浮液的微观结构，在静态悬浮液中形成了面向电场方向的颗粒柱，在剪切悬浮液中形成了面向流动方向的集中颗粒条纹。这些结构变化与流变现象密切相关。颗粒柱的形成引起了剧烈的流变变化。条纹的出现与瞬态流变反应的开始有关，当条纹合并、变粗和变密时，剪切应力缓慢增加。ER和MR流体正被用于减震器、离合器和制动器等应用的开发，MR应用最近达到商业化。对瞬态结构和流变行为的理解和建模对于电流变换器和磁流变器的设计、优化和控制至关重要。粒子级模拟对于理解粒子性质、相互作用和宏观行为之间的关系是有价值的。然而，这些方法在计算上很昂贵，因此不适合对整个设备的行为进行建模。必须开发其他建模策略来补充粒子级模拟并克服其固有的局限性。我们已经开发了一个连续体描述结构演变的ER悬浮液，表征为时间和位置相关的颗粒体积分数_（x; t）。粒子通量通过动量平衡与粒子对应力的贡献有关。使用这种双流体方法，可以预测实验中观察到的模式——静止悬浮液中的柱状形成，剪切悬浮液中的条纹形成——而无需跟踪单个颗粒运动的计算费用。虽然这种连续体模型可以成功地再现结构演化的某些特征，但本构行为的假设限制了它的预测能力。最值得注意的是，假设适合于各向同性悬浮液的静电应力的形式排除了对场诱导剪切应力的估计，从而排除了相关的流变瞬态；而忽略非定域极化对长时间瞬态的影响较小。这项工作的主要目标是结合两种建模方法的优势，以获得ER/MR流体和设备的多尺度描述，克服我们之前连续体建模工作的局限性。我们将采用颗粒级模拟（即斯托克动力学模拟）来确定连续介质模型中使用的颗粒应力和颗粒通量的适当本构行为。采用这种本构行为将使我们能够从连续体的角度探索结构和剪切流变的演变。我们还将扩展电流变流体的自洽场模型来模拟连续介质模型中的非局部极化贡献，以描述长时间的瞬态现象。所提出的工作将产生一个完整的连续描述在ER和MR流体的流变学和质量传输，可用于设计，优化和控制ER和MR流体和设备。模拟研究将由Klingenberg， Morris和学生进行，并与通用汽车公司的Ulicny继续协商。验证实验将在华盛顿大学和通用汽车公司进行。通用汽车公司还将提供在通用汽车公司的离合器测试台上测量的离合器性能的实验结果。通过提供流变学和质量传递的模型，所提出的工作将特别有利于剪切ER和MR设备的设计、优化和控制。这些信息是必要的，因为粒子输运似乎在剪切ER和MR流体中普遍存在，并影响表观流变性。更一般地说，所提出的工作将有利于悬架力学研究，因为我们进一步发展连续体方法来描述悬架的流动。这项工作的广泛影响包括通过培训本科生和研究生在这项工作的技术建模方面以及实验技术的教育组成部分。这项工作的结果将通过向评审期刊提交手稿和在科学会议上发表报告的方式提供给科学界。