壁面局部动态扰动作用下湍流边界层多尺度相互作用

Scale Interactions of Turbulent Boundary Layer Flows Under Local Dynamic Wall Disturbance

对比分析大尺度高速/低速来流背景下,多种尺度间的相互作用,讨论通过主动减阻控制系统间歇输入能量实现流场减阻控制的可行性。实验使用压电振子对湍流边界层施加周期性局部扰动,同步采集压电振子上游固定探针和下游移动探针(沿法向高度移动)的流场信息。通过对压电振子上、下游不同尺度脉动速度信号的相关性分析,确定上下游信号的时空关系。通过预乘能谱图确定扰动信号及其高次谐波,并划分不同信号尺度。着重讨论大尺度高速/低速来流背景下,大尺度与扰动尺度、扰动尺度与小尺度的相互作用,发现大尺度高速背景对扰动信号有幅值调制作用。大尺度高速/低速来流背景下,扰动信号与小尺度信号存在固定的相位对应关系,且不受来流背景影响。明确以压电振子对流场进行主动间歇性控制时,在大尺度高速来流背景下施加局部动态扰动具有更好的调制控制效果。

This paper analysed the relationships between various scales by considering the condition of the upstream flow fields.The feasibility of flow control for drag reduction through intermittent energy input from active drag reduction systems was discussed.In the experiment,a piezoelectric oscillator was used to impose local disturbances on a turbulent boundary layer.Flow field information was collected using fixed probes upstream of the piezoelectric oscillator and moving probes downstream(moving along the wall-normal direction).Correlation analyses were performed on velocity signals of different scales both upstream and downstream of the piezoelectric oscillator to determine their spatiotemporal relationships.Distur-bance signals and their higher-order harmonics were identified through the pre-multiplied energy spectrum,and different signal scales were categorized.The interactions between large scales and disturbance scales,as well as between disturbance scales and small scales,were particularly discussed under large-scale high-speed/low-speed inflow backgrounds.It is observed that the large-scale high-speed background modulates the disturbance signals.Under both large-scale high-speed and low-speed inflow backgrounds,there exists a fixed phase correspondence between the disturbance signals and small-scale signals,which remains unaffected by the inflow background.It is explicitly stated that when actively controlling the flow field intermittently using a piezoelectric oscillator,it is advisable to operate under a large-scale high-speed inflow background.