Effects of Spatial Inhomogeneity on Nonlinear Pattern Forming Systems

空间不均匀性对非线性图案形成系统的影响

• 批准号: 9610248
• 负责人: Robert Behringer
• 金额: $ 22.5万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-09-15 至 2000-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9610248&HistoricalAwards=false
• 关键词: Effects; Spatial; Inhomogeneity; Nonlinear; Pattern

This is an investigation of the effects of spatial inhomogeneities in both thermally driven convection and Taylor vortex flow (TVF). The investigation will consider both porous media convection (PMC) and Rayleigh-Benard convection (RBC). The experiments on PMC will be a continued exploration of the effects of media spatial structure on both pattern selection and stability-and the consequent, often large, effects on heat and impurity transport. This work will relate pattern selection to pore structure, for both pure fluids and binary mixtures. Regarding RBC, the experiments will involve horizontal variations in both the layer thickness and in the temperature profile. Related experiments will address similar effects in Taylor vortex flow (TVF) where the radial gap, (delta)R, between the inner and outer cylinder varies. The advantage of this flow is that the first pattern-forming instability (when only the inner cylinder rotates) is to rolls aligned along the cylinder axis-therefore, the complications of directional degeneracy are removed. It is envisioned that experiments on different hydrodynamic systems with control over spatial variations in different ways, will yield broad insight into the effects of spatial variations on such flows. In the past, there has been some work focusing on slow spatial variations of parameters or periodic variation of parameters, but very little on the effects of broad-band random spatial variations, a particularly important issue for PMC. There are a number of important applications for this work including heat transfer devices, insulation, and the flow of contaminants in ground water when there are temperature or concentration gradients. In most practical applications involving heat and mass flows, the systems are far from the usually studied idealizations, and the need for more information on imperfect systems is considerable. Recently developed experimental techniques will allow experimenters to non-invasively image patterns in PMC, leading to im portant new insights into the effects of the medium structure on pattern selection. Particle imaging velocimetry (PIV) will be used to study TVF.

这是一个调查的空间不均匀性的影响，在热驱动对流和泰勒涡流（TVF）。研究将考虑多孔介质对流（PMC）和瑞利-贝纳德对流（RBC）。 PMC的实验将继续探索介质空间结构对模式选择和稳定性的影响，以及随之而来的，通常很大的，对热量和杂质传输的影响。 这项工作将涉及模式选择的孔隙结构，为纯流体和二元混合物。 关于RBC，实验将涉及层厚度和温度分布的水平变化。 相关实验将解决泰勒涡流（TVF）中的类似效应，其中内外圆柱体之间的径向间隙（Δ）R变化。 这种流动的优点是，第一个图案形成不稳定性（当只有内圆筒旋转时）是使辊沿着圆筒轴线对齐，因此，消除了方向简并的复杂性。据设想，在不同的流体动力学系统与控制空间变化，以不同的方式进行实验，将产生广泛的洞察空间变化对这种流动的影响。 在过去，已经有一些工作集中在缓慢的空间变化的参数或周期性变化的参数，但很少在宽带随机空间变化的影响，一个特别重要的问题PMC。 这项工作有许多重要的应用，包括传热设备，绝缘，以及当存在温度或浓度梯度时地下水中污染物的流动。 在大多数涉及热量和质量流的实际应用中，系统与通常研究的理想化相去甚远，并且需要有关不完美系统的更多信息。 最近开发的实验技术将允许实验者非侵入性的图像模式在PMC，导致important新的见解的介质结构对模式选择的影响。 粒子成像测速技术（PIV）将被用来研究TVF。