Propulsion through Diffusion

通过扩散推进

• 批准号: 0854230
• 负责人: Thomas Peacock
• 金额: $ 8.2万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0854230&HistoricalAwards=false
• 关键词: Propulsion; through; Diffusion

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).0854230 Peacock, Thomas The PIs have discovered a remarkable new propulsion mechanisms that operates in density-stratified environments. The underlying mechanism is a little-studied phenomenon, diffusion-driven flow, first identified within the context of salt transport in rock fissures and ocean boundary-mixing; although its origins date back to Prandtl's study of thermal winds. Diffusion-driven flow spontaneously arises due to an interaction between diffusion and gravity on sloping surfaces, which are the rule rather than the exception for floating, neutrally-buoyant objects. If a floating object is asymmetric, diffusion-driven flow produces an unbalanced force that propels it. The PIs have demonstrated this concept in salt-stratified water, using a carefully designed triangular wedge. At first sight, the effect is highly counterintuitive, requiring no moving parts and therefore seemingly generating propulsion from nowhere; when in fact, the kinetic energy of motion is drawn from the underlying molecular diffusion process. Many fundamental questions remain to be answered, including: How does the propulsion speed scale with the governing parameters? Does suppression of vertical fluid motion by stratification dictate that confinement is always an influence? And is this effect exploited to transport particles and organisms in natural settings, such as lakes and oceans? This study will develop understanding of a new physical effect in fluid dynamics: propulsion through diffusion. The planned studies center on a carefully coordinated program of laboratory experiments, designed to investigate the interdependency of the dimensionless groups that govern the propulsion speed as affected by, three-dimensionality, shape, stratification, diffusivity, viscosity and inertia.. The planned Particle Image Velocimetry (PIV) is difficult for such small-scale, low-speed flows. This data will reveal the underlying flow structure, to help develop analytical and numerical models. Undergraduate research students will be involved in the experiments through the MIT UROP program and through a flow-visualization research project coordinated with Dr. Jim Bales at the MIT Edgerton Lab. Visualizations will be posted to repositories of fluid mechanics, and benchmark data for testing numerical simulations of stratified flow will be posted on the PI's website.

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。0854230孔雀，托马斯私人投资公司发现了一种在密度分层环境中运行的非凡的新推进机制。潜在的机制是一种很少被研究的现象，扩散驱动的流动，首先在岩石裂隙中的盐分运输和海洋边界混合的背景下被发现；尽管它的起源可以追溯到普兰特对热风的研究。扩散驱动的流动是由于倾斜表面上的扩散和重力之间的相互作用而自发产生的，对于漂浮的中性浮力物体来说，这是规则而不是例外。如果漂浮物是不对称的，扩散驱动的流动会产生一种不平衡的力来推动它。PI使用精心设计的三角形楔子，在盐分分层水中演示了这一概念。乍一看，这种效果是非常违反直觉的，不需要移动部件，因此似乎没有从哪里产生推力；而实际上，运动的动能来自潜在的分子扩散过程。许多基本问题仍有待回答，包括：推进速度如何与控制参数保持一致？层化对垂直流体运动的抑制是否意味着禁闭总是一种影响？这种效应是否被用来在湖泊和海洋等自然环境中运输颗粒和有机体？这项研究将加深对流体动力学中一种新的物理效应的理解：通过扩散推进。计划中的研究以精心协调的实验室实验计划为中心，旨在调查控制推进速度的无量纲基团之间的相互依存关系，这些基团受三维、形状、层化、扩散性、粘度和惯性的影响。计划中的粒子图像测速(PIV)对于这样的小尺度、低速流动来说是困难的。这些数据将揭示潜在的流动结构，以帮助开发分析和数值模型。本科生将通过麻省理工学院UROP计划和与麻省理工学院埃杰顿实验室的吉姆·贝尔斯博士协调的流动可视化研究项目参与实验。可视化图像将发布到流体力学知识库中，用于测试分层流动的数值模拟的基准数据将发布在PI的网站上。