用层析高时间分辨率PIV研究复杂条件下壁湍流相干结构时空演化动力学特征及湍流控制减阻机理

We will measure time series of three-dimension- three-component (3D-3C) velocity vector fields in turbulent boundary layer with solid-liquid, gas-liquid, gas-solid-liquid multiphase fluids at different Reynolds numbers and different pressure gradients using tomographic time-resolved Particle Image Velocimetry (PIV) technique, accompanied by the pressure measurement at different positions on the wall with time-resolved pressure sensors. Comparing with DNS results, we will investigate the temporal-spatial dynamics of coherent structures evolution for their producing, developing and maintaining stages by different analysis methodologies, such as the spatial local-averaged velocity structure function, the dynamic mode decomposition (DMD), the Lagrangian coherent structure, the conditional sampling and spatial phase average method，POD etc. Furthermore, the phase-average spatial mode evolutions of different physical quantities of coherent structures at their producing, developing and maintaining process will be also analyzed, including velocity, velocity gradient, velocity strain, vorticity, Reynolds stress and turbulent kinetic energy production etc. In addition, we will discuss the singularity of the dynamical system on the distributions of above-mentioned physical quantities in the phase space. Besides, we will evaluate the drag reduction effects for the coherent structures active and passive manipulation techniques utilizing wall piezoelectric ceramics local distortion, wall local blowing/suction, groove/riblet wall, high polymer solution additives,compliant wall, wavy wall, wall coating, wall roughness and wall micro-bubbles etc. Lastly, we will discuss the variations of all above-mentioned contents at different Reynolds numbers and different pressure gradients in the solid-liquid, gas-liquid and gas-solid-liquid multiphase fluid 2D and 3D turbulent boundary layers.

用层析高时间分辨率PIV技术测量不同雷诺数、不同压力梯度、固液、气液、气固液多相湍流边界层3D-3C速度场的时间序列，同时用多个高时间分辨率压力传感器测量壁面不同位置压强变化；结合对比直接数值模拟数据库的分析，用空间局部平均速度结构函数、动力模态分解、拉格朗日相干结构、条件采样和空间相位平均、恰当正交分解等技术分析相干结构产生、发展、演化的时空动力学规律，研究相干结构的速度场、速度梯度场、速度变形率场、涡量场、雷诺应力场、湍流产生项等物理量的在相干结构产生、发展、演化不同阶段的空间相位平均形态的变化；分析上述物理量在相空间分布的动力系统奇异性；用壁面压电陶瓷局部变形、壁面局部吹吸、沟槽、高分子聚合物溶液添加剂、柔性壁、波形壁、壁面涂料、壁面粗糙元、壁面微气泡等相干结构主、被动控制技术实现壁湍流减阻；分析上述研究内容随不同雷诺数、不同压力梯度、固液、气液、气固液多相的变化规律。

背景：湍流边界层是广泛存在于航空航天飞行器、交通运输工具和工业流体设备中的复杂流动形态，其中大尺度相干结构是湍流边界层中的主要结构，与湍流边界层的维持、演化、发展密切相关，是流动中的能量消耗、传热传质、运行稳定、振动噪声的主要原因。开展相干结构发展演化的运动学、动力学机理的研究，提出通过主/被动控制相干结构实现湍流边界层减阻的有效技术，.主要研究内容：利用层析高时间分辨率粒子图像测速(Tomo-TRPIV)、高时间分辨率粒子图像测速(TRPIV)、热线测速等先进的流动测量技术，对壁湍流相干结构时-空发展演化特征进行了实验研究，发现了湍流边界层相干结构表现为沿法向多层分层的反对称涡包结构，发现了发卡涡的空间流线拓扑表现为鞍点-焦点不稳定动力系统。针对多种水面/水下航行体及管道输运等工程减阻需求，开展超疏水壁面、人工粗糙元壁面、沟槽壁面、低浓度高分子聚合物溶液添加剂等减阻壁面湍流边界层相干结构特征与被动控制减阻机理的实验研究，发现减阻条件下，壁湍流相干结构的四极子涡包结构受到破坏，相干结构的活跃度和湍流产生量均减弱，湍流相干结构的自繁衍机制受到抑制。使用安装在壁面上的单个、展向布置的同步和异步振动的双压电振子振动，只用开环控制23.3%的能量消耗实现湍流边界层主动控制并取得了22.6%的减阻效果，实现了湍流边界层相干结构猝发开环/闭环主动控制和高效减阻。