Investigation of Flow-Induced Instabilities in a Francis Turbine Operating in Non-Cavitating and Cavitating Part-Load Conditions
Artikel i vetenskaplig tidskrift, 2023

The integration of intermittent renewable energy resources to the grid system requires that hydro turbines regularly operate at part-load conditions. Reliable operation of hydro turbines at these conditions is typically limited by the formation of a Rotating Vortex Rope (RVR) in the draft tube. In this paper, we investigate the formation of this vortex using the scale-resolving methods SST-SAS, wall-modeled LES (WMLES), and zonal WMLES. The numerical results are first validated against the available experimental data, and then analyzed to explain the effect of using different scale-resolving methods in detail. It is revealed that although all methods can capture the main features of the RVRs, the WMLES method provides the best quantitative agreement between the simulation results and experiment. Furthermore, cavitating simulations are performed using WMLES method to study the effect of cavitation on the flow in the turbine. These effects of cavitation are shown to be highly dependent on the amount of vapor in the RVR. If the amount of vapor is small, cavitation induces broadband high-frequency fluctuations in the pressure and forces exerted on the turbine. As the amount of cavitation increases, these fluctuations tend to have a distinct dominant frequency which is different from the frequency of the RVR.

cavitating simulations

synchronous pressure fluctuations

scale-resolving simulations

rotating vortex rope


Mohammad Hossein Arabnejad Khanouki

Chalmers, Mekanik och maritima vetenskaper, Marin teknik

Håkan Nilsson

Chalmers, Mekanik och maritima vetenskaper, Strömningslära

Rickard Bensow

Chalmers, Mekanik och maritima vetenskaper, Marin teknik


23115521 (eISSN)

Vol. 8 2 61

Unsteady flow and cavitation during off-design and transients in water turbines

Energiforsk AB (VKU14164), 2021-10-01 -- 2022-12-31.

Chalmers, 2021-10-01 -- 2022-12-31.

Svenskt Vattenkraftcentrum (2018-2022), 2021-10-01 -- 2022-12-31.


Hållbar utveckling


Teknisk mekanik


Strömningsmekanik och akustik




C3SE (Chalmers Centre for Computational Science and Engineering)



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