Modifying the Boundary Conditions of Lubricant Flow

修改润滑油流动的边界条件

• 批准号: 0119626
• 负责人: Steve Granick
• 金额: $ 30.23万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0119626&HistoricalAwards=false
• 关键词: Modifying; Boundary; Conditions; Lubricant; Flow

0119626Granick This work will provide a critical experimental assessment of the"stick" boundary condition of continuum hydrodynamics. The stick assumption is presently one of the cornerstones of calculation regarding fluid flow in tribology yet recent theories and experiments raise the exciting possibility that surfaces can be engineering to produce the boundary condition of partial slip. The approach will consist of testing the classical Reynolds Equation of continuum hydrodynamics for cases where systematic prior experiments do not yet exist: partially-wetted surfaces (finite contact angle of the fluid on the surface) and variable surface roughness (the roughness will be topographical, chemical, and lubrication additives). For measurement, a modified surface forces apparatus will be operated at spacings large enough (10-200 nm) that intervening Newtonian fluids are believed to behave as a continuum. Nanometer-level oscillatory modulations of film spacing will be performed such that the amplitude and frequency of modulation are varied independently, allowing the mean velocity to vary over a wide range without large change of the film thickness. First, we will put to direct test recent theoretical predictions and molecular dynamics simulations that predict breakdown of stick boundary conditions when low-viscosity fluids fail to wet completely a smooth solid boundary. Secondly, we will extend this work to" patchy" surfaces - surfaces that are chemically and geometrically rough - to test theoretical predictions that" stick" boundary conditions of fluid flow stem from the presence of roughness. Third, we will extend this work to "hairy" surfaces - surfaces that bear surface-attached polymer chains. This is the situation that prevails in oil lubrication owing to the presence of polymer additives. It is the situation that prevails in biolubrication owing to the presence of surface-attached biomacromolecules. The engineering impact will be to point the way to new ways by which energy dissipation can be controlled during lubricant flow. The main applications will pertain not so much to the high-load conditions characteristic of heavy machines, as to the low-load conditions characteristic of emerging nanotechnologies and micromachines.***

0119626 Granick这项工作将提供一个关键的实验评估的“棒”边界条件的连续流体动力学。 粘假设是目前计算的基石之一，在摩擦学流体流动，但最近的理论和实验提出了令人兴奋的可能性，表面可以工程产生的边界条件的部分滑移。该方法将包括测试经典的雷诺方程的连续流体动力学的情况下，系统的先前的实验还不存在：部分润湿的表面（有限的接触角的表面上的流体）和可变的表面粗糙度（粗糙度将地形，化学和润滑添加剂）。 为了测量，将在足够大的间距（10-200 nm）下操作经修改的表面力装置，使得介入的牛顿流体被认为表现为连续体。 纳米级的振荡调制膜间距将被执行，使得调制的振幅和频率是独立变化的，允许的平均速度在很宽的范围内变化，而没有大的变化的膜厚度。首先，我们将直接测试最近的理论预测和分子动力学模拟，预测故障的坚持边界条件时，低粘度流体不能完全润湿光滑的固体边界。 其次，我们将这项工作扩展到“补丁”表面-表面是化学和几何粗糙-测试理论预测，“坚持”流体流动的边界条件干从粗糙度的存在。 第三，我们将把这项工作扩展到“毛状”表面--带有表面附着的聚合物链的表面。 由于聚合物添加剂的存在，这是油润滑中普遍存在的情况。 由于表面附着的生物大分子的存在，这是生物润滑中普遍存在的情况。 工程的影响将指出的方式，通过这种新的方式可以控制能量耗散在润滑剂流动。主要的应用与其说是重型机器的高负载条件特征，不如说是新兴的纳米技术和微型机器的低负载条件特征。