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Influence of synthetic jet on uniform momentum zones
International Journal of Heat and Fluid Flow ( IF 2.6 ) Pub Date : 2023-03-30 , DOI: 10.1016/j.ijheatfluidflow.2023.109131
Jin-Hao Zhang , Biao-Hui Li , Jing-Bo Su , Nan Jiang

Based on a set of streamwise-wall-normal experimental databases of turbulent boundary layer (TBL) acquired by time-resolved particle image velocimetry (TR-PIV) system at the Reynolds number Reτ=537, which includes the velocity fields with and without synthetic jet, the influence of the synthetic jet on uniform momentum zones (UMZs) was studied. The turbulent/non-turbulent (T/NT) interface of each instantaneous frame was identified by local turbulent kinetic energy (L-TKE) method and the area below the interface was divided into UMZs by probability density function (P.d.f.) histogram of streamwise velocity. The relationship between the T/NT interface average height EYi and the UMZs number NUMZ is analyzed. The spatial position and velocity of UMZs are extracted by centroid method, and the basic statistical characteristics within UMZs under two working conditions are investigated. After processing the velocity fields corresponding to each NUMZ separately, it is found that NUMZ is highly correlated with Q events. The synthetic jet reduces the streamwise and wall-normal length scales of the fluid induced by Q events, and under the same externa conditions, the two scales are also positively related to the intensity of Q events. The shear stress in the flow field promotes the generation of the forward vortices, which drives the stratification of UMZs. The hairpin vortices generated by synthetic jet result in a large number of forward vortices in the region with y/δ<0.3, and the turbulent kinetic energy (TKE) and Reynolds shear stress are input into the vortex region in varying degrees.



中文翻译:

合成射流对均匀动量区的影响

基于雷诺数下时间分辨粒子图像测速(TR-PIV)系统获取的一组湍流边界层(TBL)流向壁面法向实验数据库关于τ=537,其中包括有和没有合成射流的速度场,研究了合成射流对均匀动量区 (UMZ) 的影响。通过局部湍流动能(L-TKE)方法识别每个瞬时帧的湍流/非湍流(T / NT)界面,并通过流向速度的概率密度函数(Pdf)直方图将界面下方的区域划分为UMZ . T/NT界面平均高度的关系和 UMZ 编号UMZ被分析。通过质心法提取UMZs的空间位置和速度,研究了两种工况下UMZs内部的基本统计特征。处理完每个对应的速度场后UMZ分别发现UMZ与 Q 事件高度相关。合成射流减小了由Q事件引起的流体的流向和壁法向长度尺度,并且在相同的外部条件下,这两个尺度也与Q事件的强度正相关。流场中的剪应力促进前向涡流的产生,从而驱动 UMZs 的分层。合成射流产生的发夹涡导致该区域出现大量前向涡/δ<0.3,湍流动能(TKE)和雷诺剪切应力不同程度地输入到涡流区域。

更新日期:2023-03-30
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