Multiscale Modeling of Flow over Functionalized Surfaces: Algorithms and Applications

CBET-0852948 Karniadakis许多微流体、合成材料和生物医学应用经常需要从近壁子区域和外部流动在较长的模拟时间内模拟几个数量级的时空尺度上的多尺度流动现象。该项目的目标是开发一种经过验证的方法，用于模拟具有生物医学焦点的功能化表面上的多尺度流动现象。为此，PI提出了一种基于介观方法(耗散粒子动力学或DPD)与分子动力学(MD)和不可压缩N-S(NS)方程无缝对接的“三层”流动模型。与以前的方法不同，PI方法的新奇之处在于在NS和MD之间使用了介观层，以促进从原子论到连续统制度的平稳过渡。他们对简单流体的初步结果显示了这种方法的巨大潜力。在这里，PI提出了根本性的新发展，使该方法适用于复杂的流体和包括聚合物刷子在内的功能化表面上的流动，其中由一端拴在表面上的聚合物链的组装形成了具有特殊性质的表面。从De Gennes的工作开始，大量的理论和实验工作将作为一个试验台来验证所提出的方法并评估其效率，然后使用聚合物刷子作为细胞表面的模型来模拟蛋白质涂层表面的细胞黏附。本文的目的是开发一个基于分子的粘接动力学模型，以补充现有的多粒子粘接动力学的宏观力学模型。具体地说，PI将模拟疟疾感染的红细胞(RBC)与功能化壁上的结合，就像最近的微流体实验中所做的那样，本质上是模拟小动脉和毛细血管中的细胞黏附。三层流体(MD-DPD-NS)方法是通用的，可以应用于微流体或生物医学应用中的简单和复杂流体，也可以应用于更经典的应用，例如使用表面活性剂或疏水表面来控制壁面剪应力。DPD首先在欧洲推广，是模拟复杂流体和软物质的一种非常有效的方法，但在美国还没有得到广泛的应用，本文的工作将有助于DPD的进一步应用和发展。更广泛地说，这项关于聚合物刷子的工作可用于广泛的工业应用，如采油、汽车润滑、胶体稳定以及裁剪表面特性。私人投资公司将通过现有的外部开放源码网站，将其模型和三层代码作为开放源码传播。他们将组织面向布朗大学所有学生的研讨会课程，重点是多尺度建模和应用。此外，本科生通过布朗大学的UTRA(本科教学和研究助学金)计划，将在学年或夏季参与研究项目。PIS还与MET学校合作，为市中心的高中生计划外展活动，在那里，布朗的学生将与MET学校的教师密切合作，辅导MET高中生的物理和数学。这项研究由CBET、CMMI和DMS部门共同资助。

CBET - 0852948KarniadakisMany microfluidic, synthetic-materials, and biomedical applications often need to model multiscale flow phenomena across several orders of magnitude in spatio-temporal scales from near-wall subdomains but also the outer flow over long simulation times. The goal of this project is to develop a validated methodology for simulating multiscale flow phenomena over functionalized surfaces with a biomedical focus. To this end, the PIs propose a "triple-decker" flow model based on interfacing seamlessly a mesoscopic method (dissipative particle dynamics or DPD) to molecular dynamics (MD) on one side and incompressible Navier-Stokes (NS) equations on the other side. The novelty of the PIs' approach is the use of a mesoscopic layer between NS and MD--unlike previous approaches-- to facilitate a smooth transition from the atomistic to the continuum regime. Their preliminary results for simple fluids show the great potential of this method. Here the PIs propose fundamental new developments to make the method applicable to complex fluids and to flows over functionalized surfaces including polymer brushes, where an assembly of polymer chains tethered by one end to a surface creates a surface with specialized properties. The large theoretical and experimental works on this topic, starting with the work of de Gennes, will act as a testbed to validate the proposed methodology and evaluate its efficiency and then model cytoadhesion over protein-coated surfaces using the polymer brushes as model of cell surface. The objective here is to develop a molecularly based adhesive dynamics model to complement existing mechanistic macromodels for multiparticle adhesive dynamics. Specifically, the PIs will simulate the binding of malaria-infected red blood cells (RBCs) to functionalized walls, as was done in recent microfluidic experiments, in essence mimicking cytoadhesion in arterioles and capillaries. The triple-decker (MD-DPD-NS) approach is general and can be applied to simple and complex fluids in microfluidic or biomedical applications but also in more classical applications, e.g., control of wall shear stress using surfactants or hydrophobic surfaces. DPD, first popularized in Europe, is a very effective method for modelng both complex fluids and soft matter but has not yet been adapted widely in USA, and the proposed work will contribute to its further use and development. More broadly, this work on polymer brushes can be used in a wide range of industrial applications in oil recovery, automotive lubrication, colloid stabilization, and in tailoring surface properties. The PIs will disseminate their models and the triple-decker codes as open source codes via existing external open source websites. They will organize seminar-courses open to all students at Brown University focused on multiscale modeling and applications. In addition, undergraduate students, through Brown's UTRA (Undergraduate Teaching and Research Assistantships) program, will be involved in the research projects, either during the academic year or the summer. The PIs also plan outreach activities for inner-city high school students in a partnership with the MET school, where Brown students will be tutoring MET high school students in physics and mathematics in close collaboration with MET school teachers.This study is cofunded by the CBET, CMMI, and DMS divisions.