Numerical study of instability mechanism in the air-core vortex formation process

Air-core vortices are a ubiquitous phenomenon in the intakes of hydropower stations. Due to the transient and instability of two-phase vorticial flow, the prediction of air-core vortex formation is challenging, and understanding of the instability mechanism remains elusive. In this study, the large...

Full description

Saved in:
Bibliographic Details
Published in:Engineering applications of computational fluid mechanics 2023-12, Vol.17 (1)
Main Authors: Kan, Kan, Xu, Yuhang, Li, Zhixiang, Xu, Hui, Chen, Huixiang, Zi, Dan, Gao, Qiang, Shen, Lian
Format: Article
Language:English
Subjects:
Air-core vortex
Attenuation
counterrotating pair
Flow stability
Fluid flow
Hydroelectric power stations
Intake pipes
Large eddy simulation
Surface stability
Two phase flow
Velocity gradient
Vortices
Vorticity
water level fluctuation
Water level fluctuations
wave
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Air-core vortices are a ubiquitous phenomenon in the intakes of hydropower stations. Due to the transient and instability of two-phase vorticial flow, the prediction of air-core vortex formation is challenging, and understanding of the instability mechanism remains elusive. In this study, the large eddy simulation (LES) method and a coupled level-set and volume-of-fluid (CLSVOF) method are performed to study air-core vortex formation in a benchmark reservoir with a horizontal intake pipe. The process of air-core vortex formation can be classified into an inception stage, an instability stage, and a stability stage. In the instability stage, the surface vortex repeatedly goes through the process of inception, enhancement, attenuation, and extinction. The movement of the counterrotating secondary vortices and water surface level fluctuation plays a negative role in air-core vortex formation. The additional motion generated by the counterrotating pair drives the pair to the back wall. The main vortex undergoes attenuation due to the stretching/tilting effects induced by the secondary vortex. Water level fluctuations briefly increase the submergence depth, which in turn reduces the vertical velocity gradient and vertical vorticity, destabilizing the vortex. The perturbation of the air-core vortex by water level fluctuations is present only at the beginning of the instability stage.
ISSN:1994-2060
1997-003X
DOI:10.1080/19942060.2022.2156926