Control of near-wall turbulence via slip and transpiration

通过滑移和蒸腾控制近壁湍流

• 批准号: 1965893
• 金额: --
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1965893
• 关键词: Control; near; wall; turbulence; via

Turbulent motions near the wall are dominated by a quasi-cyclic, self-sustaining process driven by the interaction between two key coherent structures: quasi-streamwise vortices and streaks. This process has been observed to contribute significantly to turbulent skin friction drag, suggesting that turbulent flow control techniques would benefit by seeking to disrupt it. One such technique is to manipulate the flow in such a way that results in the turbulence statistics of the different velocity components being shifted relative to each other in the wall normal direction. This may be achieved with complex geometrical structures, such as riblets, or with the use of non-conventional boundary conditions in numerical simulations, such as surface slip. Another technique, know as transpiration, counteracts velocity fluctuations near the wall by flow injection and suction at the wall itself, and can also result in a relative shift in the turbulence statistics. The primary aim of this project will be to simulate, understand and model the combined effect of surface slip and transpiration on near-wall turbulence by using direct numerical simulations (DNS). It might then be possible to identify an optimum combination of streamwise slip, spanwise slip and wall-normal transpiration for drag reduction that could later be used to aid in the design of novel control techniques.

墙壁附近的湍流运动以准环状，自我维持的过程为主导，这是由两个关键相干结构之间的相互作用驱动的：准式旋转的涡旋和条纹。已经观察到该过程对湍流皮肤摩擦的阻力有显着贡献，这表明湍流控制技术将通过寻求破坏它而受益。一种这样的技术是以这样的方式操纵流量，从而导致在壁正常方向上相对于彼此相对移动的不同速度成分的湍流统计。这可以通过复杂的几何结构（例如Riblets）或在数值模拟（例如表面滑动）中使用非惯性边界条件来实现。另一种被称为蒸腾作用的技术，通过在壁本身的流动注入和吸力来抵消墙壁附近的速度波动，也可能导致湍流统计数据的相对变化。该项目的主要目的是通过使用直接数值模拟（DNS）模拟，理解和建模表面滑动和蒸腾对近壁湍流的综合作用。然后，有可能确定流向滑动，跨度滑动和壁正常蒸腾作用的最佳组合，以减少阻力，后来可以用来帮助设计新颖的控制技术。

项目成果

The smooth-wall-like behaviour of turbulence over drag-altering surfaces: a unifying virtual-origin framework

阻力改变表面上的湍流的光滑壁状行为：统一的虚拟原点框架

• 发表时间: 2020
• 期刊: arXiv preprint
• 作者: Ibrahim J I

A unified approach to the study of turbulence over smooth and drag-reducing surfaces

研究光滑减阻表面湍流的统一方法

• 发表时间: 2019
• 作者: Ibrahim JI

Control of the buffer and logarithmic layers in wall-bounded turbulent flows

壁界湍流中缓冲层和对数层的控制

• 发表时间: 2021
• 作者: Joseph I Ibrahim