动态粗糙元扰动对湍流边界层多尺度作用和自维持机制影响的实验研究

As increasing the Reynolds number, large-scale structures become more remarkable on spatial scales and energy containing, but also exhibit an important role on scale interactions and self-sustaining mechanisms of turbulent boundary layer, which indicates that the large-scale structures dominate the dynamic characteristics of the turbulent boundary layer. Thus, the large-scale structures are deemed as the jumping-off place of flow control. In this proposal, the dynamic roughness element will added to the turbulent boundary layer to perturb the large-scale structures by the secondary flow with a certain spatial-temporal scale, and the experimental measurements by combining hot-wire rake and Tomo-TRPIV will be carried out, to investigate the dynamic roughness effects on the dynamics of turbulent boundary layer. From the viewpoint of statistics and structures, the scale interactions and self-sustaining mechanisms under the dynamic roughness perturbation will be discussed. By the advantage of the simultaneity of Tomo-TRPIV and hot-wire data, the spatial-temporal characters of the dynamic perturbation will be further analyzed to explore the relationship between the turbulent structures and statistics. Then, the physical explanation of the scale interactions will be provided, and the dynamic roughness effects on the self-sustaining dynamic process will be further addressed. Advances of this work have direct implications for the development of wall turbulence model and control method. It could have the potential application value on the transport system, and play an important role in the energy and environment fields.

随着雷诺数的升高，大尺度结构不仅在空间尺度和能量贡献方面具有突出表现，而且对湍流边界层的尺度作用和自维持机制也有重要影响，从而主导着湍流边界层的动力学特性，因此，大尺度结构也成为了尝试湍流边界层控制的出发点。本项目拟在湍流边界层中加入动态粗糙元，产生具有特定时空尺度的二次流动结构对大尺度结构进行扰动作用，结合多通道热线技术和Tomo-TRPIV对扰动作用下的湍流边界层进行同步测量。分别从统计学和形态学的角度，研究动态扰动对湍流边界层多尺度作用和自维持机制的影响。基于动态粗糙元的时空扰动特征，结合多通道热线和Tomo-TRPIV实验数据，建立尺度结构和形态结构之间的联系，解释尺度作用的物理意义，揭示动态粗糙元扰动对湍流边界层自维持特性的影响机理。本项目的开展，不仅能够为发展湍流边界层控制手段、建立湍流模型提供理论依据，而且对输运系统具有潜在的应用价值，在节能环保等方面具有重要意义。

随着雷诺数的升高，大尺度结构不仅在空间尺度和能量贡献方面具有突出表现，而且对湍流边界层的尺度作用和自维持机制也有重要影响，因此，大尺度结构和近壁小尺度内循环系统共同作用并主导着壁湍流流动机理。本项目通过发展大尺度PIV、锁相Tomo-PIV和单/双通道热线，对湍流边界层中的多尺度构架和调制作用机理开展了研究，给出了尺度作用的结构学物理解释，揭示了湍流边界层多尺度自维持机理。通过前缘扰动的改变，探究了高雷诺数下大尺度结构的运动学特性，揭示了人工产生高雷诺数湍流边界层的尺度作用机制。针对外区大尺度结构和近壁内循环系统，分别发展了动态粗糙元扰动和壁面压电振子扰动控制方法，探究湍流边界层的高效减阻控制。研究发现外区大尺度结构面对动态粗糙元扰动表现出了很强的鲁棒性。外区大尺度结构对近壁压电振子扰动尺度具有幅值放大作用，并且激发出相位翻转的高阶谐波，从而对湍流小尺度结构和喷射事件产生了相位耦合调制作用，实现了25%的壁面减阻。本项目的开展，不仅能够为发展湍流边界层控制手段、建立湍流模型提供理论依据，而且对输运系统具有潜在的应用价值，在节能环保等方面具有重要意义。