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Global linear stability analysis of flow inside an axial swirl generator with a rotating vortex rope
Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-7599-0895
2023 (English)In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 61, no 1, p. 34-50Article in journal (Refereed) Published
Abstract [en]

In hydraulic turbines, either Francis or axial turbines, a high swirling flow is generated at PL conditions at the inlet of the draft tube resulting in the formation of a rotating vortex rope (RVR). This leads to pressure fluctuations which limit the operating range of single regulated turbines. In the present study, an axial hydraulic turbine has been numerically simulated by the k−ϵk−ϵ and SST-based Scale-Adaptive Simulation model (SST SAS) turbulent models to capture helical RVR. Considering the formation of the RVR as the result of a global instability, linear global stability analysis of the time-averaged turbulent flow field has been conducted. For the first time in axial hydraulic turbines, how boundary conditions affect the unstable mode and which frequency, plunging or rotating, is related to the vortex rope instability have been studied. It is found that the flow inside the draft tube is sensitive to the asymmetrical disturbances with a frequency close to the rotational component.

Place, publisher, year, edition, pages
Taylor & Francis, 2023. Vol. 61, no 1, p. 34-50
Keywords [en]
Part-load, rotating vortex rope, stability analysis, turbomachinery, turbulence
National Category
Fluid Mechanics
Research subject
Fluid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-94412DOI: 10.1080/00221686.2022.2106591ISI: 000889555700001Scopus ID: 2-s2.0-85142376465OAI: oai:DiVA.org:ltu-94412DiVA, id: diva2:1714857
Funder
EU, Horizon 2020, 814958
Note

Validerad;2023;Nivå 2;2023-04-20 (joosat);

Available from: 2022-11-30 Created: 2022-11-30 Last updated: 2025-02-09Bibliographically approved

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Cervantes, Michel

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