Publication detail
Experimental investigation of vortex ring formation as a consequence of spiral vortex re-connection
ŠTEFAN, D. RUDOLF, P. HUDEC, M. URUBA, V. PROCHÁZKA, P. URBAN, O.
English title
Experimental investigation of vortex ring formation as a consequence of spiral vortex re-connection
Type
conference paper
Language
en
Original abstract
The unsteady shape variation of a cavitating spiral vortex is experimentally studied pointing out the repetitive creation of vortex ring (or vortex loop). To generate the spiral vortex structure, a newly designed vortex generator is employed. This generator is used to study the decelerated swirling flow leading to the spiral vortex formation as a consequence of spiral vortex breakdown, which is considered to be the main triggering mechanism for the occurrence of the coherent vortex rope structure in the Francis turbine draft tube operated at part load conditions. Thanks to its design, the vortex generator enables to change the ratio between fluxes of axial momentum and tangential moment of momentum of generated swirl. Using this set-up, the behavior of the vortex structure changes in a similar way as the flow rate variation in the draft tube of Francis turbine. At certain flow conditions, the spiral vortex movement is characterized by sudden spiral entanglement leading to disconnection of a vortex ring and followed by spiral reconnection. Thanks to the transparent diffuser of the swirl generator apparatus, both high-speed camera recording of the cavitating vortex and PIV measurements of velocity fields at cavitationfree conditions are employed. The main aim of this paper is to link the visual observation of the above described vortex dyn
English abstract
The unsteady shape variation of a cavitating spiral vortex is experimentally studied pointing out the repetitive creation of vortex ring (or vortex loop). To generate the spiral vortex structure, a newly designed vortex generator is employed. This generator is used to study the decelerated swirling flow leading to the spiral vortex formation as a consequence of spiral vortex breakdown, which is considered to be the main triggering mechanism for the occurrence of the coherent vortex rope structure in the Francis turbine draft tube operated at part load conditions. Thanks to its design, the vortex generator enables to change the ratio between fluxes of axial momentum and tangential moment of momentum of generated swirl. Using this set-up, the behavior of the vortex structure changes in a similar way as the flow rate variation in the draft tube of Francis turbine. At certain flow conditions, the spiral vortex movement is characterized by sudden spiral entanglement leading to disconnection of a vortex ring and followed by spiral reconnection. Thanks to the transparent diffuser of the swirl generator apparatus, both high-speed camera recording of the cavitating vortex and PIV measurements of velocity fields at cavitationfree conditions are employed. The main aim of this paper is to link the visual observation of the above described vortex dyn
Keywords in English
spiral vortex, Francis turbine, velocity
Released
20.12.2019
ISSN
1755-1315
Book
IOP Conference Series: Earth and Environmental Science
Volume
405
Number
2019
Pages from–to
1–6
Pages count
6
BIBTEX
@inproceedings{BUT161148,
author="Edita {Mariánková} and David {Štefan} and Pavel {Rudolf} and Martin {Hudec} and Ondřej {Urban},
title="Experimental investigation of vortex ring formation as a consequence of spiral vortex re-connection",
booktitle="IOP Conference Series: Earth and Environmental Science",
year="2019",
volume="405",
number="2019",
month="December",
pages="1--6",
issn="1755-1315"
}