This paper first uses a low-speed stereoscopic particle image velocimetry (SPIV) system to measure the convergent statistical quantities of the flow field and then simultaneously measure the time-resolved flow field and the wall mass transfer rate by a high-speed SPIV system and an electrochemical system, respectively. We measure the flow field and wall mass transfer rate under upstream pipe Reynolds numbers between 25 000 and 55 000 at three specific locations behind the orifice plate. Moreover, we apply proper orthogonal decomposition (POD), stochastic estimation and spectral analysis to study the properties of the flow field and the wall mass transfer rate. More importantly, we investigate the large-scale coherent structures’ effects on the wall mass transfer rate. The collapse of the wall mass transfer rates’ spectra by the corresponding time scales at the three specific positions of orifice flow suggest that the physics of low-frequency wall mass transfer rates are probably the same, although the flow fields away from the wall are quite different. Furthermore, the spectra of the velocity reconstructed by the most energetic eigenmodes agree well with the wall mass transfer rate in the low-frequency region, suggesting that the first several energetic eigenmodes capture the flow dynamics relevant to the low-frequency variation of the wall mass transfer. Stochastic estimation results of the velocity field associated with large wall mass transfer rate at all three specific locations further reveal that the most energetic coherent structures are correlated with the wall mass transfer rate.

中文翻译：

---

大尺度高能相干结构及其对圆管孔后壁传质速率的影响

本文首先使用低速立体粒子图像测速（SPIV）系统测量流场的收敛统计量，然后通过高速SPIV系统同时测量时间分辨流场和壁面传质速率，分别是电化学系统。我们在孔板后面的三个特定位置测量上游管道雷诺数在 25 000 到 55 000 之间的流场和壁传质速率。此外，我们应用适当的正交分解（POD）、随机估计和谱分析来研究流场和壁传质速率的特性。更重要的是，我们研究了大规模相干结构对壁传质速率的影响。壁面传质率谱在孔口流动的三个特定位置的相应时间尺度上的坍缩表明，低频壁面传质率的物理特性可能是相同的，尽管远离壁面的流场相当不同的。此外，由最有活力的本征模式重建的速度谱与低频区域的壁传质速率非常吻合，这表明前几个高能本征模式捕获了与壁质量的低频变化相关的流动动力学转移。与所有三个特定位置的大壁传质速率相关的速度场的随机估计结果进一步表明，最具能量的相干结构与壁传质速率相关。