RUI: Multi-scale modeling of interfacial flows of magnetic fluids with macro-chain aggregates

磁流体（或铁磁流体）是磁性纳米颗粒的悬浮液，其性质和流动受到外加磁场的影响，使其在工业和生物医学应用中非常有用。潜在的未来应用，如靶向药物输送和微流体泵送，涉及小尺度的活性界面和运动，在小尺度上磁颗粒分布可能变得不均匀。特别是，在适度的电场下，纳米颗粒聚集成宏观链，进而影响流体的流动。这些链先前已经被研究人员使用在阿贡国家实验室获得的高分辨率x射线相衬图像观察到。小尺度铁磁流体的建模和模拟的进一步发展需要新的方法。为了加快铁磁流体器件的开发和设计步伐，促进铁磁流体新应用的探索，需要一种鲁棒且灵活的模拟方法。本项目将开发、验证和应用这样一个工具，以多尺度代码的形式用于磁流体界面流动的数值模拟。这些模拟代码将集成场致宏观磁粒子链的中尺度模型和具有最先进界面的Navier-Stokes代码的体铁磁流体的实际非线性磁化。Navier-Stokes计算将包括一个高阶曲率算法，该算法可以精确计算界面处的表面张力。由场诱导的宏观链引起的粘性应力将由耗散粒子动力学型模型导出。该提案包括精心策划的项目，将涉及和支持来自蒙特克莱尔州立大学不同人口的学生进行前沿研究。研究人员将开发一种计算机模拟磁性液体，也被称为铁磁流体，一种独特的“智能”材料，很容易用普通磁铁操纵。虽然广泛用作计算机磁盘驱动器中的液体密封，但这种易于控制的流体具有更大的潜力，包括应用于生物医学（药物输送、眼科手术和MRI造影剂）以及用于生物技术和药物测试中操纵微小流体体积的小型设备。进展被两个障碍所阻碍。首先，实验受到限制，因为这种液体非常不透明，看起来像一种闪亮的黑色液体。其次，赋予流体磁性的纳米级颗粒也导致了内部结构，如颗粒链，这使得其数学描述变得复杂。该项目通过使用最先进的计算机模拟而不是实验来克服第一个挑战，而它通过在Argonne国家实验室进行的高分辨率x射线实验建立简单的内部结构力学模型来克服第二个挑战。研究人员将让学生参与开发这一计算机模拟工具的关键角色，该工具可用于探索、设计和测试这些和其他磁流体的新应用。

Magnetic fluids (or ferrofluids) are suspensions of magnetic nanoparticles whose properties and flows are affected by applied magnetic fields, making them useful in industrial and biomedical applications. Potential future applications, such as targeted drug delivery and micro fluidic pumping, involve both active interfaces and motion on small scales, upon which the magnetic particle distribution may become nonuniform. In particular, under moderate fields, nanoparticles aggregate into macroscopic chains which, in turn, affect the fluid flow. These chains have been previously observed by the investigators using high resolution X-ray phase-contrast images obtained at Argonne national lab. Further progress in modeling and simulation of ferrofluids on small scales demands new approaches. To speed the pace of development and design of ferrofluidic devices and to facilitate the exploration of new ferrofluid applications, a robust and exible simulation method is required. This project will develop, validate and apply such a tool, in the form of a multi-scale code for the numerical simulation of interfacial flows of magnetic fluids. These simulation codes will integrate a mesoscale model of field-induced macroscopic magnetic-particle chains and a realistic nonlinear magnetization for the bulk ferrofluid with a state-of-the-art interfacial Navier-Stokes code. The Navier-Stokes computation will include a high-order curvature algorithm that accurately computes surface tension at interfaces. Viscous stress due to field induced macro-chains will be derived from a dissipative particle dynamics type model. The proposal includes carefully planned projects that will involve and support students from Montclair State's diverse population in leading-edge research.The investigators will develop a computer simulation of magnetic liquid, also known as ferrofluid, a unique "smart" material that is easily manipulated using ordinary magnets. While widely used as a liquid seal in computer disk drives, this easily controlled fluid has far greater potential, including applications in biomedicine (drug delivery, eye surgery and as MRI contrast agents) and in small scale devices which manipulate tiny fluid volumes, as used in biotechnology and pharmaceuticals tests. Progress has been stalled by two obstacles. First, experiments are limited because the fluid is very opaque, appearing as a shiny black liquid. Second, the nano-scale particles which give the fluid its magnetic character also lead to internal structures, such as particle chains, which make its mathematical description complex. This project overcomes the first challenge by using state-of-the-art computer simulations instead of experiments, while it overcomes the second challenge by building simple mechanical models of internal structure based on high resolution x-ray experiments, performed at Argonne national lab. The investigators will involve students in key roles in the development of this computer simulation tool that can be used to explore, design and test these and other new applications of magnetic fluids.