Experiments on Three-Dimensional Disturbance Interactions Leading to Boundary-Layer Transition

三维扰动相互作用导致边界层转变的实验

• 批准号: 0245253
• 负责人: Edward White
• 金额: $ 21.49万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-05-15 至 2006-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0245253&HistoricalAwards=false
• 关键词: Experiments; Three; Dimensional; Disturbance; Interactions

PROPOSAL NO.: CTS-0245253PROPOSAL TYPE: INVESTIGATOR INITIATEDPRINCIPAL INVESTIGATOR: EDWARD B. WHITEINSTITUTION: CASE WESTERN RESERVE UNIVERSITYEXPERIMENTS ON THREE-DIMENSIONAL DISTURBANCE INTERACTIONS LEADING TO BOUNDARY LAYER TRANSITIONThe laminar-to-turbulent transition of boundary layers is a complicated process that can proceed via a number of scenarios depending on fluid velocity, surface geometry, environmental disturbances, and other factors. In spite of its complicated nature, past research on the subject of transition has tended to focus on single disturbance-growth mechanisms in isolation from all other competing mechanisms. For Blasius boundary layers, the growth of streamwise-traveling, spanwise-invariant disturbances known as Tollmien-Schlichting (T-S) waves is one such mechanism that has been extensively studied. A newly discovered mechanism known as transient growth, which favors stationary, spanwise-varying disturbances, has also received significant attention. Although much progress has been made in understanding these mechanisms in isolation, little progress has been made in predicting or controlling transition onset in real systems in which several competing mechanisms can exist. To address the lack of useful data on realistic transition scenarios involving competing disturbances, a wind-tunnel investigation of the interactions of T-S waves and transient disturbances in a Blasius boundary layer will be undertaken. The proposed experiments will provide a controlled and systematic investigation of how T-S waves, transient disturbances, and the secondary instabilities of both compete and interact to bring about transition. The input disturbances will be varied over wide parameter ranges and will be designed to take full advantage of signal-analysis techniques suitable for extracting very low amplitude disturbance signals from a noisy background. The results will provide data necessary for transition prediction and control efforts. Beyond the intrinsic scientific value of the project, the proposed work will also contribute to the improvement of important technological systems and to the promotion of the role of research in teaching at Case Western Reserve University. Transition affects the performance and efficiency of a broad range of vehicles and industrial systems because laminar boundary layers result in low vehicle drag, whereas turbulent boundary layers are often desired for complete and efficient fluid mixing. It would be of great benefit if designers were capable of predicting and controlling the conditions under which laminar flows become turbulent. Accurate prediction would shorten design cycles and reduce the over design typical of systems sensitive to transition, and flow control would permit the design of radically more efficient systems. More immediately, this project will enhance the role of research in teaching by supporting a vigorous experimental program in a wind-tunnel laboratory that is accessible to undergraduates and by incorporating the work performed in the tunnel into experimental-methods and fluid mechanics instruction.

提案编号： CTS-0245253提案类型：提案人发起的主要提案人：Edward B。怀特研究所：边界层从层流到湍流的转捩是一个复杂的过程，它可以通过许多方案进行，这取决于流体速度、表面几何形状、环境扰动和其他因素。 尽管其复杂的性质，过去的研究对过渡的主题往往集中在单一的扰动增长机制孤立于所有其他竞争机制。 对于Blasius边界层，被称为Tollmien-Schlichting（T-S）波的流向传播、展向不变扰动的增长是一种已被广泛研究的机制。 一个新发现的机制称为瞬态增长，有利于稳定，展向变化的干扰，也受到了极大的关注。 虽然在孤立地理解这些机制方面取得了很大进展，但在预测或控制可能存在几种竞争机制的真实的系统中的转变开始方面却进展甚微。 为了解决缺乏有关涉及竞争扰动的实际转捩方案的有用数据的问题，将进行Blasius边界层中T-S波和瞬态扰动相互作用的风洞研究。 拟议的实验将提供一个控制和系统的调查如何T-S波，瞬态干扰，和二次不稳定性的竞争和相互作用，以实现过渡。 输入干扰将在宽的参数范围内变化，并将被设计为充分利用信号分析技术，适用于从嘈杂的背景中提取非常低的振幅干扰信号。 研究结果将为转捩预测和控制工作提供必要的数据。 除了该项目的内在科学价值外，拟议的工作还将有助于改善重要的技术系统，并促进凯斯西储大学的研究在教学中的作用。 过渡影响广泛范围的车辆和工业系统的性能和效率，因为层流边界层导致低车辆阻力，而湍流边界层通常需要完全和有效的流体混合。 如果设计者能够预测和控制层流变成湍流的条件，那将是非常有益的。 准确的预测将缩短设计周期，减少过渡敏感系统的过度设计，流量控制将允许设计效率更高的系统。 更直接的是，该项目将通过支持一个充满活力的实验计划，在风洞实验室，是本科生访问，并通过将在隧道中进行的工作纳入实验方法和流体力学教学，提高研究在教学中的作用。