Analysis and Rheological Measurements of Suspensions of Magnetic Nanoparticles in Oscillating/Rotating Magnetic Fields

波多黎各大学-马亚圭提出将流体力学的研究和教学工作结合起来，特别是磁活性复杂流体的响应。研究任务包括铁磁流体、悬浮在粘弹性流体中的永久磁化纳米颗粒、磁流变流体和磁流变流体复合材料的交流磁场响应的协调实验和理论研究。需要考虑的具体问题包括：由于施加在圆柱形容器和同轴圆柱形几何结构中的流体上的均匀旋转磁场而产生的流动和扭矩，沿板形和锥形几何形状的轴方向的直流/交流磁场，以及板-板和锥-板情况下板平面上的均匀旋转磁场。对于铁磁流体，在线性磁化极限下采用摄动法求解铁磁流体动力学方程，在非线性磁化范围内采用数值方法求解铁磁流体动力学方程。计划中的实验将测试这些分析的结果，使用改进的流变仪和粘度计来测量容器壁上的扭矩，并使用超声多普勒测速仪来测量诱导流场。最后，提出了振动/旋转均匀磁场下平面泊泽维尔/库埃特流的铁水动力流动稳定性分析，以及同轴圆柱库埃特几何结构在振动轴向磁场作用下的稳定性分析，并将后者作为项目的一部分进行了实验验证。教育工作的重点是通过化学工程的最新发展，包括提出的研究成果，非牛顿流体现象和处理的问题和例子，以及利用有限元技术模拟复杂问题，从而解决更新我们核心课程的迫切需要，使流体力学和运输现象的本科和研究生课程充满活力。智力优势：拟议的研究旨在填补磁活性复杂流体文献中的空白，在这些文献中，对应用交流场的流体响应进行协调的实验和理论研究将有助于进一步理解和应用开发。从基本的角度来看，待研究的流体是有趣的，因为它们可能维持电磁体偶，从而导致不对称的应力状态，需要考虑内部角动量守恒。从实际的角度来看，通过拟议的研究获得的知识将有助于推进这些受应用交流磁场影响的磁活性复杂流体的应用，包括磁流体热疗和基于磁性纳米颗粒的纳米传感器。以本研究成果为基础，对本科流体力学和研究生输运现象课程进行改革的教育努力，将满足日益增长的对化学工程核心课程进行改革的需求，以应对未来几代人将面临的挑战。更广泛的影响：在波多黎各大学马亚圭斯校区执行拟议的研究和教育任务，这是一个非博士学位授予（根据NSF定义）西班牙裔服务机构，为NSF提供了促进各种更广泛影响优先领域的特殊机会。平均每年有110名化学工程学士和10名化学工程硕士毕业，几乎所有的毕业生都是西班牙裔美国公民，其中68%是女性。我们的本科生中有很大一部分活跃在upm和美国的夏季项目（如NSF REU）的研究中。这些学生中的许多人随后进入美国的大学攻读研究生学位。此外，由于最近在拉美裔大学建立了一个博士项目，该项目有可能进一步推动拉美裔美国人参与美国博士水平的研究和教育。为了实现这些目标并更好地为这些学生服务，拟议的教育任务旨在更新核心课程，并创建与拟议研究相关的新课程，并解决未来几代人面临的挑战。此外，PI将指导本科生和研究生进行拟议的研究。提出的研究旨在分析和测试具有磁性活性的复杂流体，以进一步了解这些系统，并开发下一代仪器来研究它们的行为。最后，提出的研究和教育任务的结果将通过有关的研究和教育文献以及通过国家和国际会议加以传播

ABSTRACT - 0457359University of Puerto Rico - MayaguezA combined research and education effort in fluid mechanics in general and the response of magneticallyactive complex fluids in particular is proposed. Research tasks consist of coordinated experimental and theoretical studies of the AC magnetic field response of ferrofluids, permanently magnetized nanoparticles suspended in viscoelastic fluids, magnetorheological fluids, and magnetorheological fluid composites. Specific problems to be considered include flows and torques due to uniform rotating magnetic fields applied to the fluid in a cylindrical container and in a coaxial cylinder geometry, DC/AC fields along the axis of plateplate and cone-plate geometries, and uniform rotating fields in the plane of the plate in the plate-plate and cone-plate situations. For ferrofluids, the equations of ferrohydrodynamics will be solved using perturbation methods in the linear magnetization limit and using numerical methods in the nonlinear magnetization regime. Planned experiments will test the results of these analyses using modified rheometers and viscosimeters to measure the torques on container walls and using Ultrasonic Doppler Velocimetry to measure the induced flow fields. Finally, analyses of ferrohydrodynamic flow stability for the planar Poiseuille/Couette flow in the presence of oscillating/rotating uniform magnetic field and for the coaxial cylinder Couette geometry with applied oscillating axial field are proposed, with the latter being verified experimentally as part of the project. Educational efforts are focused on invigorating undergraduate and graduate courses on fluid mechanics and transport phenomena with recent developments in Chemical Engineering, including results from the proposed research, and problems and examples of phenomena and processing of non-Newtonian fluids, and utilization of finite element techniques to model complex problems, thereby addressing the pressing need to update our core curriculum.Intellectual Merit: The proposed research aims to fill gaps in the magnetically-active complex fluids literature where coordinated experimental and theoretical studies of fluid response to applied AC fields would be of value to further understanding and application development. The fluids to be studied are interesting from a fundamental perspective as they may sustain electromagnetic body couples, consequently resulting in asymmetric states of stress and the need to consider internal angular momentum conservation. From a practical perspective, the knowledge gained through the proposed research will serve to advance applications of these magnetically active complex fluids subjected to applied AC fields, including magnetic fluid hyperthermia and magnetic nanoparticle based nanosensors. Educational efforts to renovate the undergraduate fluid mechanics and graduate transport phenomena courses with results from the proposed research will satisfy the growing need to renovate the core Chemical Engineering curriculum to address the challenges to be faced by future generations.Broader Impact: Performing the proposed research and education tasks at the University of Puerto Rico Mayaguez campus, a non-PhD granting (as per NSF definitions) Hispanic Serving Institution, provides special opportunities to advance various broader impact priority areas for NSF. The UPRM graduates an average of 110 BS and 10 MS Chemical Engineers each year, practically all of which are Hispanic US citizens and 68% of which are female. A significant fraction of our undergraduate students are active in research both at UPRM and in summer programs (such as NSF REU) in the US. Many of these students subsequently attend Universities in the US to pursue graduate degrees. Furthermore, with the recent establishment of a doctoral program in ChE, the UPRM has the potential of further advancing the participation of Hispanics in doctoral-level research and education in the Nation. To achieve these goals and to better serve these students, the proposed education tasks aim to renovate core curricula and create new courses with material related to the proposed research and addressing challenges to be faced by future generations. In addition, the PI will mentor undergraduate and graduate students performing the proposed research. The proposed research aims to analyze and test magnetically active complex fluids with the objective of furthering our understanding of these systems as well as developing next-generation instrumentation to study their behavior. Finally, the results of the research and educational tasks proposed will be disseminated through the relevant research and educational literature, as well as through National and International meetings