Abstract

An ultrasound-based Lagrangian particle tracking (echo-LPT) method is used to investigate path-dependent quantities for confined vortex rings in dense suspensions with volume fractions up to 40%. The echo-LPT measurement technique is successfully validated through a close comparison of the pixel displacements collected with established ultrasound image velocimetry methods. The carrier phase of the suspension is tracked through the vortex ring in transitional and turbulent circulation-based Reynolds numbers of \(Re_{\mathrm {\Gamma }}=2.4\) , \(4.2\times 10^{4}\) . Furthermore, fluid transport and residence time are obtained using pathline extension techniques for entrained and recirculating particles in order to compare with traditional Eulerian analysis. The fluid transport and residence time results show that the entrained fluid originates from similar locations and generally indicate that there is no dependence or effect of changing volume fraction. These results show that the convective entrainment mechanisms for the forming vortex rings are insensitive to changes in \(Re_{\mathrm {\Gamma }}\) and volume fraction. Exceptions are found for the volume fraction 40% cases where increases in nonlinear fluid behaviour and particle–particle interaction are thought to inhibit vortex-ring roll-up and reduce entrainment.

Graphic abstract

摘要

基于超声的拉格朗日粒子追踪 (echo-LPT) 方法用于研究体积分数高达 40% 的稠密悬浮液中受限涡环的路径相关量。通过与已建立的超声图像测速方法收集的像素位移的密切比较，成功验证了回波 LPT 测量技术。悬浮液的载相通过涡环以基于过渡和湍流循环的雷诺数\(Re_{\mathrm {\Gamma }}=2.4\)、\(4.2\times 10^{4}\)进行跟踪。此外，使用夹带和再循环颗粒的路径延伸技术获得流体传输和停留时间，以便与传统的欧拉分析进行比较。流体传输和停留时间结果表明，夹带的流体源自相似的位置，并且通常表明不存在体积分数变化的依赖性或影响。这些结果表明，形成涡环的对流夹带机制对\(Re_{\mathrm {\Gamma }}\)和体积分数的变化不敏感。体积分数为 40% 的情况存在例外，其中非线性流体行为和颗粒间相互作用的增加被认为会抑制涡环卷起并减少夹带。

图文摘要