This video is a result of the CFD simulation of flow in a Francis turbine, operating at part load. As a result of the circumferential velocity component at the outlet of the runner, a vortex rope forms in the cone of the draft tube. Depending upon the pressure level the vortex rope may cavitate.

In this movie, the vortex rope is presented as iso-surface of vapour pressure. The simulation was performed as non-cavitating one.

Information about similar CFD simulations (cavitating or non-cavitating), with comparison with the experimental results, can be found in:
Jošt, D., Škerlavaj, A., Morgut, M., and Nobile, E., 2017. Numerical Prediction of Cavitating Vortex Rope in a Draft Tube of a Francis Turbine with Standard and Calibrated Cavitation Model. Journal of Physics: Conference Series 813(1), 012045. doi:10.1088/1742-6596/813/1/012045

This short video is a result of the CFD simulation of flow in a Francis turbine, operating at high load. Depending upon the level of excessive circumferential velocity component at the outlet of the runner, vortical structures rotate around the central coherent structure while travelling in the direction of the draft tube.

More information about the CFD simulation with the zonal LES turbulence model can be obtained in the paper:
Jošt, D., Škerlavaj, A., Morgut, M., Mežnar, P., and Nobile, E., 2015. Numerical simulation of flow in a high head Francis turbine with prediction of efficiency, rotor stator interaction and vortex structures in the draft tube. Journal of Physics: Conference Series 579(1), 012006. doi:10.1088/1742-6596/579/1/012006

 

This short video is a result of the CFD simulation of flow in a Francis turbine, operating at the best-efficiency point (BEP). A coherent structure in the center of the draft tube cone is visible. At BEP there is no circumferential velocity component at the inlet of the draft tube. Therefore, contrary to the part load, vortex structures move in the direction of the draft tube.

More information about the CFD simulation with the zonal LES turbulence model can be obtained in the paper:
Jošt, D., Škerlavaj, A., Morgut, M., Mežnar, P., and Nobile, E., 2015. Numerical simulation of flow in a high head Francis turbine with prediction of efficiency, rotor stator interaction and vortex structures in the draft tube. Journal of Physics: Conference Series 579(1), 012006. doi:10.1088/1742-6596/579/1/012006

 

These two videos are a result of the CFD simulation of flow in a Francis turbine, operating at deep part load (less than 35% of flow rate at the best efficiency point). It can be observed that the nature of the flow is unsteady, with a large swirl in the draft tube.

More information about the CFD simulation with the zonal LES turbulence model can be obtained in the paper:
Jošt, D., Škerlavaj, A., Morgut, M., Mežnar, P., and Nobile, E., 2015. Numerical simulation of flow in a high head Francis turbine with prediction of efficiency, rotor stator interaction and vortex structures in the draft tube. Journal of Physics: Conference Series 579(1), 012006. doi:10.1088/1742-6596/579/1/012006

Dragica Jošt and Mitja Morgut attended the event Academy of Mech. Engineering 2017 & 6th Int. Conference of Mech. Engineers (Ljubljana, 26th October 2017). The goal of the event is to stimulate a closer cooperation between industrial and academic spheres of mechanical engineering.

The ACCUSIM group presented the poster (in Slovene) entitled:

Napoved kavitacije v Peltonovi turbine in v centrifugalni črpalki (Prediction of Cavitation in a Pelton Turbine and in a Centrifugal Pump)

Authors: Dragica Jošt, Aljaž Škerlavaj, Mitja Morgut, Enrico Nobile, Valentin Pirnat

The poster presents results obtained with default and calibrated mass transfer models that were tested for prediction of sheet cavitation in a Pelton turbine and of cloud cavitation in a centrifugal pump.

Roberto Renato Stopar attended the conference ‘Kuhljevi dnevi 2017′  in Terme Dobrna, Slovenia, on 28th of Sept.

Kuhljevi2017

Every year, the Slovene association for Mechanics (Slovensko društvo za mehaniko) organizes conference Kuhljevi dnevi on memory of Slovene scientist Anton Kuhelj. This year the conference was in Terme Dobrna from 28th to 29th of September.

Roberto presented the paper:
Multiobjective optimization of a hydraulic shape of runner cone extension in Francis turbine

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25th -27th September 2017
Kolektor Turboinštitut, Rovšnikova 7, Ljubljana

Kolektor Turboinštitut and Dept. of Engineering and Architecture of the University of Trieste were pleased to share their knowledge and expertise, gained during the Marie-Curie European project ACCUSIM, about the application of:

  • Advanced (scale resolving) turbulence modelling
  • OpenFOAM
  • Cavitation
  • Design optimization.

In three days the participants had the opportunity to listen to 16 presentations given by ten lectures. For each of the main topics four invited speakers had introductory lectures, followed by the presentations of the results achieved during the ACCUSIM project. The main topics were discussed in practical cases for hydraulic turbines and marine propellers. The last day Kolektor Turboinštitut’s laboratory and production of small turbines was presented to everyone interested.

Among the 36 participants of the Summer school there were graduate and PhD students from Ljubljana, Maribor and Trieste and engineers from 11 companies.

Program of the ACCUSIM Summer school

Proceedings of the ACCUSIM Summer School

summer_schoolPhoto: Opening of the ACCUSIM Summer School