Collaborative Research: Control of Natural Convection Alonga Heated, Inclined Plate

合作研究：沿加热倾斜板的自然对流控制

• 批准号: 9318332
• 负责人: Ari Glezer
• 金额: $ 27.37万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-08-01 至 1998-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9318332&HistoricalAwards=false
• 关键词: Collaborative; Research; Control; Natural; Convection

The proposed research focuses on the active control on the origin and evolution of the streamwise vortices in a flat plate boundary layer along an inclined heated surface. Because these vortices play important roles in transport phenomena near the surface, active control of their onset and evolution can become a powerful tool for the manipulation of heat transfer and surface deposition for free convection boundary layers of practical interest, including cooling techniques and manufacturing of electronics chips. The proposed experiments will be conducted in water, and the flow instabilities leading to the formation of the streamwise vortices will be manipulated using mosaics of individually-controlled film heaters flush-mounted on a submerged test surface. An important feature of such manipulation is that the ensuing flow structures are extremely repeatable in time and space, thus allowing for detailed measurements and flow visualization studies that are phase-locked to the excitation wave-form. Of particular interest are the flow mechanisms, associated with the evolution of the streamwise vortices. Spanwise interactions of these vortices appear to be a precursor to the development of a secondary instability that is followed by rapid transition to turbulence. High-resolution measurements of cross-stream and spanwise time-dependent temperature distributions will be obtained using rakes of miniature cold-wire temperature sensors, and the flow will be visualized using sensitive double-pass Schlieren system. An important aspect of the proposed work is the measurement of global and of planform distributions of heat flux from the test surface to the adjacent fluid. Of particular interest is the incremental change in heat transfer between the forced and unforced flows. At the later stages of this research, the surface actuators will be used to control suppression or enhancement of the longitudinal vortices.

所提出的研究重点是沿着倾斜受热表面的平板边界层中流向涡流的起源和演化的主动控制。 由于这些涡流在表面附近的传输现象中发挥着重要作用，因此对其产生和演化的主动控制可以成为操纵传热和具有实际意义的自由对流边界层表面沉积的强大工具，包括冷却技术和电子芯片的制造。 拟议的实验将在水中进行，并且将使用齐平安装在水下测试表面上的独立控制薄膜加热器的马赛克来操纵导致流向涡流形成的流动不稳定性。 这种操纵的一个重要特征是，随后的流动结构在时间和空间上具有极高的可重复性，从而允许对激励波形进行锁相的详细测量和流动可视化研究。 特别令人感兴趣的是与流向涡流演化相关的流动机制。 这些涡流的展向相互作用似乎是二次不稳定发展的先兆，随后迅速转变为湍流。 将使用微型冷线温度传感器的耙子获得横流和翼展方向随时间变化的温度分布的高分辨率测量，并且将使用灵敏的双通纹影系统将流动可视化。 拟议工作的一个重要方面是测量从测试表面到相邻流体的热通量的全局分布和平面分布。 特别令人感兴趣的是强制流和非强制流之间传热的增量变化。 在本研究的后期阶段，表面执行器将用于控制纵向涡流的抑制或增强。