https://scholars.lib.ntu.edu.tw/handle/123456789/598833
標題: | Transient instability in long, tilted water columns with fast-settling, particle-laden layers | 作者: | Chang Y.-J Chern R.-L RUEY-LIN CHERN YI-JU CHOU |
關鍵字: | shear-flow instability;Aerodynamics;Modal analysis;Prandtl number;Stability;Baseflows;Energy gain;Flow instabilities;Particle laden flows;Particle-laden;Settling particles;Settling speed;Shear-flow instability;Transient instability;Water columns;Shear flow;flow field;flow modeling;flow stability;fluid dynamics;numerical model;shear flow;unsteady flow;wave force | 公開日期: | 2021 | 卷: | 929 | 來源出版物: | Journal of Fluid Mechanics | 摘要: | We study the stability of unsteady particle-laden flows in long, tilted water columns in batch settling mode, where the quasi-steady assumption of base flow no longer holds for the fast settling of particles. For this purpose, we introduce a settling time scale in the momentum and transport equations to solve the unsteady base flow, and utilise non-modal analysis to examine the stability of the disturbance flow field. The base flow increases in magnitude as the settling speed decreases and attains its maximum value when the settling speed becomes infinitesimal. The time evolution of the disturbance flow energy experiences an algebraic growth caused by the lift-up mechanism of the wall-normal disturbance, followed by an exponential growth owing to the shear instability of the base flow. The streamwise and spanwise wavenumbers corresponding to the peak energy gain are identified for both stages. In particular, the flow instability is enhanced as the Prandtl number increases, which is attributed to the sharpening of the particle-laden interface. On the other hand, the flow instability is suppressed by the increase in settling speed, because less disturbance energy can be extracted from the base flow. There exists an optimal tilted angle for efficient sedimentation, where the particle-laden flow is relatively stable and is accompanied by a smaller energy gain of the disturbance. ? |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85119182645&doi=10.1017%2fjfm.2021.876&partnerID=40&md5=491af10698e1cd7d6c1c54f128565464 https://scholars.lib.ntu.edu.tw/handle/123456789/598833 |
ISSN: | 00221120 | DOI: | 10.1017/jfm.2021.876 |
顯示於: | 應用力學研究所 |
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