Wall Turbulence

摘要CTS-9500518伊利诺伊州汉拉蒂大学 这一建议处理的湍流产生的流动超过固体边界。 目标是确定湍流是如何产生的，如何控制湍流，如何预测雷诺应力和小尺度湍流的性质。 该研究的一个重要特征是它使用直接数值模拟（DNS）、脉冲图像测速（PIV）、双分量激光多普勒测速（LDV）以及专门建造的湍流光学研究设施。 主要的推力是发展一个概念框架壁湍流，可以用来分析复杂的流动，并确定如何湍流可以修改。 所采取的方法是考虑结构和动力学的应力产生涡流。 研究内容包括：（1）“简单”壁湍流，如槽道中充分发展的流动或库埃特流动;（2）波浪形固体边界上的流动;（3）减阻聚合物溶液的流动。 PIV和DNS将用于研究外流中的大尺度涡。 将特别注意它们的起源和它们与靠近壁面的流动导向涡流的相互作用，这些涡流是非常大的湍流产生者。 适当的正交分解将分离大尺度和小尺度湍流。 波浪形边界上的流动与光滑边界上的流动有着根本的不同，因为靠近壁面的湍流产生与分离剪切层有关，而不是与壁面涡有关。 添加量小至3 ppm的长链聚合物，通过改变粘性壁区域中的结构，以知之甚少的方式显著降低阻力。

ABSTRACT CTS-9500518 HANRATTY UNIVERSITY OF ILLINOIS This proposal deals with turbulence generated by flow over a solid boundary. The goals are the determination of how turbulence is produced, of how to control turbulence, of how to predict Reynolds stresses and the properties of small scale turbulence. An important feature of the research is that it uses direct numerical simulations (DNS), pulsed-image velocimetry (PIV), two-component laser-Doppler velocimetry (LDV), and a specially constructed facility for optical studies of turbulence. The chief thrust is to develop a conceptual framework for wall turbulence which can be used to analyze complex flows and to determine how turbulence can be modified. The approach taken is to consider the structure and dynamics of stress producing eddies. Studies will be made of (1) "simple" wall turbulence, such as fully developed flow in a channel or Couette flow, (2) flow over a wavy solid boundary, (3) flow of a solution of drag-reducing polymers. PIV and DNS will be used to study large scale eddies in the outer flow. Particular attention will be given to their origin and to their interaction with the flow oriented vortices close to the wall which are very large producers of turbulence. Proper orthogonal decomposition will separate large and small scale turbulence. Flow over a wavy boundary is fundamentally different from flow over a smooth boundary in that turbulence production close to the wall is associated with a separating shear layer rather than wall vortices. The addition of a long chain polymer, in amounts as small as 3 ppm, dramatically decreases drag by changing the structure in the viscous wall region, in ways which are poorly understood.