Nonlinear transient high-speed non-Newtonian flow of thin films

薄膜的非线性瞬态高速非牛顿流动

• 批准号: 205002-2006
• 负责人: Khayat, Roger
• 金额: $ 2.11万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=365377
• 关键词: Nonlinear; transient; speed; non; Newtonian

The project examines the nonlinear stability of Newtonian and viscelasic thin films flowing at high speed in confined and open systems, typically as encountered in the film processing and lubrication industry. Flow in nano channels will also be considered, as encountered in nanoflidic devices. Although consisting of monatomic molecules, nano fluidic flows are typically of (compressible) non-Newtonian character because of the relatively long molecular mean-free path between colliding molecules, thus allowing momentum and energy to transferred over long distances, similarly to polymeric fluids. While creeping thin-film flows, which are mainly dominated by surface tension effects for open films, have been extensively investigated in the past, the influence of inertia and elasticity has been relatively ignored because of the difficulty in dealing with nonlinearities of convective and elastic nature. These nonlinear effects are dominant for flow at high speed and in the initial stages of development, which are often the stages when long-term difficulties emerge in real processes. The project thus focuses on open film flow with a free surface, as encountered in the coating industry, and flow of thin layer between two modulated rigid boundaries, as encountered in lubrication and nano systems. A unified spectral methodology is proposed to solve the thin-film equations, which are of the boundary-layer type. From a fundamental perspective, thin-film flow at high speed involves shock formation and is highly sensitive to initial conditions given the hyperbolic nature of the flow. From a practical perspective, the work should provide insight into the origins and causes of film instability and rupture in a given process. More importantly, the modeling and simulation are aimed at providing the film industry with the process conditions for the onset of instability, and, consequently, at providing the manufacturer with the required tools to control or avoid instability and process breakdown.

该项目考察了牛顿和粘滞薄膜在受限和开放系统中高速流动的非线性稳定性，这在胶片加工和润滑行业中是典型的。纳米通道中的流动也将被考虑，就像在纳米流体器件中遇到的那样。虽然由单原子分子组成，但纳米流体流动通常具有(可压缩的)非牛顿性质，因为碰撞分子之间的分子平均自由路径相对较长，从而允许动量和能量远距离传递，类似于聚合物流体。薄膜蠕动流动过去已被广泛研究，但由于难以处理对流和弹性性质的非线性，惯性和弹性的影响相对较少。这些非线性效应在高速流动和发展的初期阶段占主导地位，而这些阶段往往是实际过程中出现长期困难的阶段。因此，该项目的重点是涂层工业中遇到的具有自由表面的开放式薄膜流动，以及润滑和纳米系统中遇到的两个调制刚性边界之间的薄层流动。提出了一种求解边界层型薄膜方程的统一谱方法。从根本上讲，高速下的薄膜流动包括激波形成，并且由于流动的双曲性，对初始条件高度敏感。从实践的角度来看，这项工作应该提供对给定过程中薄膜不稳定和破裂的起源和原因的洞察。更重要的是，建模和模拟的目的是为电影工业提供出现不稳定的工艺条件，从而为制造商提供控制或避免不稳定和工艺故障所需的工具。