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Shiraghaee, S., Sundström, J., Raisee, M. & Cervantes, M. J. (2024). Experimental Investigation of Part Load Vortex Rope Mitigation With Rod Protrusion in an Axial Turbine. Journal of Fluids Engineering, 146(8), Article ID 081205.
Open this publication in new window or tab >>Experimental Investigation of Part Load Vortex Rope Mitigation With Rod Protrusion in an Axial Turbine
2024 (English)In: Journal of Fluids Engineering, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 146, no 8, article id 081205Article in journal (Refereed) Published
Abstract [en]

The present paper investigates the rotating vortex rope (RVR) mitigation on an axial turbine model by the radial protrusion of four cylindrical rods into the draft tube. RVR mitigation is of particular interest due to the unfavorable pressure pulsations it induces in the hydraulic circuit that can affect turbine life and performance. The protrusion lengths, which were the same among the four rods, were varied according to a predefined sequence. The experiments were performed under four part-load regimes ranging from upper part load to deep part load. Time-resolved pressure measurements were conducted at two sections on the draft tube wall along with high-speed videography and efficiency measurement to investigate the effect of the mitigation technique on the RVR characteristics and turbine performance. The recorded pressure data were decomposed and studied through spectral analyses, phase-averaging, and statistical analyses of the RVR frequency and peak-to-peak pressure amplitude distributions. The results showed different levels of pressure amplitude mitigation ranging from approximately 10% to 85% depending on the operating condition, protrusion length, and the method of analysis. The hydraulic efficiency of the turbine decreased by a maximum of 3.5% that of the best efficiency point (BEP) with the implementation of the mitigation technique. The variations in the obtained mitigation levels and efficiencies depending on protrusion length and operating condition indicate the need for the implementation of a feedback-loop controller. Thus, the protrusion length can be actively optimized based on the desired mitigation target. 

Place, publisher, year, edition, pages
ASME Press, 2024
Keywords
rotating vortex rope, hydraulic turbines, swirling flow, part load, pressure measurement, turbine efficiency
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104969 (URN)10.1115/1.4064610 (DOI)2-s2.0-85187202672 (Scopus ID)
Funder
EU, Horizon 2020, (Grant No. 814958; Funder ID: 10.3030/814958)
Note

Validerad;2024;Nivå 2;2024-04-04 (joosat);

Full text: CC BY license

Available from: 2024-04-04 Created: 2024-04-04 Last updated: 2024-06-27Bibliographically approved
Shiraghaee, S., Sundström, J., Raisee, M. & Cervantes, M. J. (2024). Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation. Renewable energy, 225, Article ID 120232.
Open this publication in new window or tab >>Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation
2024 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 225, article id 120232Article in journal (Refereed) Published
Abstract [en]

The implementation of hydropower to stabilize electrical grids dictates more frequent off-design operations of these renewable energy resources. Flow instabilities under such conditions reduce the efficiency of hydro turbines. Part-load operation is particularly detrimental since the development of a rotating vortical structure termed rotating vortex rope (RVR) in the draft tube leads to periodic pressure pulsations that jeopardize turbine performance. This paper experimentally explores a novel solution involving the protrusion of flat plates into the turbine draft tube. Three flat plates equally separated by 120° were vertically installed on the draft tube wall. The plates were protruded up to 83% of the draft tube local radius under four different part-load conditions. Their impact was observed through time-resolved pressure measurements in the draft tube and vaneless space, as well as efficiency measurements. The results demonstrated successful RVR mitigation, achieving a maximum 85% reduction in pressure oscillation amplitudes. Protruding flat plates disrupted RVR periodicity and coherence, confining its orbit to the draft tube center. This approach proved particularly effective at lower part-load conditions, enhancing turbine hydraulic efficiency by increasing torque extraction. Reducing the adverse effects under part load, the proposed method appears promising in extending the operational range of hydraulic turbines.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Hydropower, Part-load, Pressure measurement, Rotating vortex rope, Turbine efficiency, Vortex rope mitigation
National Category
Fluid Mechanics and Acoustics Energy Engineering
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104627 (URN)10.1016/j.renene.2024.120232 (DOI)2-s2.0-85187203326 (Scopus ID)
Funder
EU, Horizon 2020, 814958
Note

Validerad;2024;Nivå 2;2024-03-18 (hanlid);

Full text license: CC BY

Available from: 2024-03-18 Created: 2024-03-18 Last updated: 2024-05-08Bibliographically approved
Kalantar Neyestanaki, M., Dunca, G., Jonsson, P. & Cervantes, M. J. (2024). Extending the pressure-time method to bend using 3D-CFD. Flow Measurement and Instrumentation, 96, Article ID 102535.
Open this publication in new window or tab >>Extending the pressure-time method to bend using 3D-CFD
2024 (English)In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 96, article id 102535Article in journal (Refereed) Published
Abstract [en]

According to the IEC 60041 standard, the pressure-time method (1D PTM) can be employed to determine the flow rate in hydraulic turbines. This method assumes a one-dimensional flow and applies to straight pipes with uniform cross-sections, with specific restrictions on the pipe length, fluid velocity, and distance between the measurement sections from any irregularities in the pipeline. However, challenges arise when applying this method in low-head hydropower plants due to the short lengths, irregularities like bends and developing flows in the intake. The present paper aims to improve the performance of the method in the presence of a bend. To this end, a test rig has been developed and measurements performed, including such geometry. The data are evaluated using the development of a newly proposed approach combining the 1D PTM based on an energy balance formulation and three-dimensional computational fluid dynamics (3D CFD) developed for axis-symmetrical accelerating flows. The updated methodology includes a correction of the experimental pressure measurements used in the 1D PTM to account for the effects of the Dean vortices present after the bend as well as the kinetic energy correction factors which deviate from known values in transient conditions. The results obtained under conditions involving the presence of bends either between or in close proximity to one show a significant improvement compared to the standard one-dimensional pressure-time method.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
3D CFD, Bend, Low-head hydraulic turbine, Pressure-time method out of IEC 60041
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-103997 (URN)10.1016/j.flowmeasinst.2024.102535 (DOI)2-s2.0-85182870156 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-02-26 (joosat);

Full text license: CC-BY

Available from: 2024-01-29 Created: 2024-01-29 Last updated: 2024-03-26Bibliographically approved
Kalantar Neyestanaki, M., Dunca, G., Jonsson, P. & Cervantes, M. J. (2024). Extending the Pressure-Time Method to Pipe With Variable Cross-Section With Three-Dimensional Numerical Simulations. Journal of Fluids Engineering, 146(2), Article ID 021305.
Open this publication in new window or tab >>Extending the Pressure-Time Method to Pipe With Variable Cross-Section With Three-Dimensional Numerical Simulations
2024 (English)In: Journal of Fluids Engineering, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 146, no 2, article id 021305Article in journal (Refereed) Published
Place, publisher, year, edition, pages
ASME Press, 2024
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-102519 (URN)10.1115/1.4063491 (DOI)001147728000011 ()2-s2.0-85182877054 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-11-20 (joosat);

Available from: 2023-11-20 Created: 2023-11-20 Last updated: 2024-03-26Bibliographically approved
Mitruț, R., Bucur, D. M., Dunca, G. & Cervantes, M. J. (2024). Flow Around a 2D-Cylinder: Influence of Bluff-Bodies in the Wake. UPB Scientific Bulletin, Series D: Mechanical Engineering, 86(1), 207-220
Open this publication in new window or tab >>Flow Around a 2D-Cylinder: Influence of Bluff-Bodies in the Wake
2024 (English)In: UPB Scientific Bulletin, Series D: Mechanical Engineering, ISSN 1454-2358, E-ISSN 2286-3699, Vol. 86, no 1, p. 207-220Article in journal (Refereed) Published
Place, publisher, year, edition, pages
University Politechnica of Bucharest, 2024
Keywords
linear global stability analysis, sensitivity analysis, vortex shedding
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-105616 (URN)2-s2.0-85193715798 (Scopus ID)
Note

Validerad;2024;Nivå 1;2024-05-28 (hanlid);

Funder: Ministry of Investments and European Projects (62461/03.06); Ministry of Research, Innovation and Digitization (PN-III-P2-2.1-PTE-2021-0269)

Available from: 2024-05-28 Created: 2024-05-28 Last updated: 2024-05-28Bibliographically approved
Kumar, S., Cervantes, M. J. & Gandhi, B. (2024). Flow Field Analysis of Francis Turbine Draft Tube using POD at Design and Part Load Operating Conditions. Journal of Applied Fluid Mechanics, 17(4), 770-784
Open this publication in new window or tab >>Flow Field Analysis of Francis Turbine Draft Tube using POD at Design and Part Load Operating Conditions
2024 (English)In: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 17, no 4, p. 770-784Article in journal (Refereed) Published
Abstract [en]

The hydraulic turbines, especially Francis turbines, frequently run at part load (PL) conditions to meet the dynamic energy needs. The flow field at the runner exit changes significantly with a change in the operating point. At PL, flow instabilities such as the Rotating Vortex Rope (RVR) form in the draft tube of the Francis turbine. The present paper compares the features of the velocity and vorticity field of the Francis turbine draft tube at the best efficiency point (BEP) and PL operations using the Proper Orthogonal Decomposition (POD) of the 2D-PIV data. The POD analysis decomposes the flow field into coherent and incoherent structures describing the spatiotemporal behavior of the flow field. A visual representation of the coherent structures and the turbulent length scales in the flow field is extracted and analyzed for BEP and PL, respectively. The study highlights the salient features of the draft tube flow field, which differentiate the BEP and PL operation. The fast Fourier transform of the temporal coefficients confirms the presence of RVR frequency (0.29 times the runner frequency) at PL. The phase portraits of different modes elucidate the relationship between different harmonics of the RVR frequency at PL.

Place, publisher, year, edition, pages
Isfahan University of Technology, 2024
Keywords
POD, Part load, Vortex rope, Dissipation, Francis Turbine
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104298 (URN)10.47176/jafm.17.4.2274 (DOI)001156482800010 ()2-s2.0-85185516449 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-04-02 (joosat);

Full text license: CC BY-NC-ND 4.0; 

Available from: 2024-02-19 Created: 2024-02-19 Last updated: 2024-04-02Bibliographically approved
Seifi, Z., Raisee, M. & Cervantes, M. J. (2024). Linear global stability analysis of a transient swirling flow leading to the formation of a helical precessing vortex breakdown in a straight diffuser. European journal of mechanics. B, Fluids, 103, 43-57
Open this publication in new window or tab >>Linear global stability analysis of a transient swirling flow leading to the formation of a helical precessing vortex breakdown in a straight diffuser
2024 (English)In: European journal of mechanics. B, Fluids, ISSN 0997-7546, E-ISSN 1873-7390, Vol. 103, p. 43-57Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Part-load, Rotating vortex rope, Stability analysis, Turbomachinery, Turbulence, Transient simulation
National Category
Fluid Mechanics and Acoustics Energy Engineering
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-101663 (URN)10.1016/j.euromechflu.2023.08.004 (DOI)001075975400001 ()2-s2.0-85170645395 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-10-16 (joosat);

Available from: 2023-10-16 Created: 2023-10-16 Last updated: 2023-10-16Bibliographically approved
Bahrami, M. A., Raisee, M., Cervantes, M. J. & Nourbakhsh, A. (2024). Numerical investigation of hydrodynamic damping of a pitching hydrofoil at different flow regimes. In: Yuan Shouqi (Ed.), The 17th Asian International Conference on Fluid Machinery (AICFM 17 2023) 20/10/2023 - 23/10/2023 Zhenjiang, China: . Paper presented at 17th Asian International Conference on Fluid Machinery (AICFM17), Zhenjiang, China, October 20-23, 2023. Institute of Physics (IOP), Article ID 012071.
Open this publication in new window or tab >>Numerical investigation of hydrodynamic damping of a pitching hydrofoil at different flow regimes
2024 (English)In: The 17th Asian International Conference on Fluid Machinery (AICFM 17 2023) 20/10/2023 - 23/10/2023 Zhenjiang, China / [ed] Yuan Shouqi, Institute of Physics (IOP), 2024, article id 012071Conference paper, Published paper (Refereed)
Abstract [en]

Due to the development of intermittent renewable energy resources, hydropower plants are mostly operated under off-design conditions. This may lead to natural frequency excitation shortening the turbine life-span. To accurately estimate the fatigue life, it is necessary to evaluate the hydrodynamic damping parameters. In the present study, different flow regimes and their relationship with hydrodynamic damping are analyzed numerically using the 3 - Reθt transition SST ĸ - ω turbulence model. The test case is a NACA0009 hydrofoil pitching around its center of mass. A good agreement between the present and previous numerical results is obtained. Consistent with the literature, hydrodynamic damping coefficient demonstrate consistently two different regions. The phase shift between the displacement and moment increases with the rise of the pitching frequency. After reaching a peak value at a reduced frequency of around κ = 5, the phase shift starts to decrease, and eventually approaches zero again. The damping behavior demonstrates an opposite trend. First, it reduces in spite of the phase shift increase, and after the inflection point, where the flow field changes from the drag mode to the thrust mode, it rises due to the torque development. The maximum of the damping occurs at the low frequencies.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2024
Series
Journal of Physics: Conference Series, ISSN 1742-6588, E-ISSN 1742-6596 ; 2707
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104954 (URN)10.1088/1742-6596/2707/1/012071 (DOI)2-s2.0-85188256771 (Scopus ID)
Conference
17th Asian International Conference on Fluid Machinery (AICFM17), Zhenjiang, China, October 20-23, 2023
Note

Full text license: CC BY 3.0; 

Available from: 2024-04-03 Created: 2024-04-03 Last updated: 2024-04-03Bibliographically approved
Khullar, S., Kumar, S., Singh, K. M., Cervantes, M. J. & Gandhi, B. K. (2024). Numerical study of peripheral air injection in draft tube of a Francis turbine at upper and normal part load operations. Sadhana (Bangalore), 49(1), Article ID 81.
Open this publication in new window or tab >>Numerical study of peripheral air injection in draft tube of a Francis turbine at upper and normal part load operations
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2024 (English)In: Sadhana (Bangalore), ISSN 0256-2499, E-ISSN 0973-7677, Vol. 49, no 1, article id 81Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Springer Nature, 2024
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104492 (URN)10.1007/s12046-023-02366-y (DOI)2-s2.0-85185560933 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-03-07 (hanlid);

Funder: Central Power Research Institute (CPR-1133-MID, CPR-1799-MID)

Available from: 2024-03-07 Created: 2024-03-07 Last updated: 2024-03-07Bibliographically approved
Seifi, Z., Raisee, M. & Cervantes, M. J. (2024). Optimal flow control of vortex breakdown in a laminar swirling flow. In: Yuan Shouqi (Ed.), The 17th Asian International Conference on Fluid Machinery (AICFM 17 2023) 20/10/2023 - 23/10/2023 Zhenjiang, China: . Paper presented at 17th Asian International Conference on Fluid Machinery (AICFM17), Zhenjiang, China, October 20-23, 2023. Institute of Physics (IOP), Article ID 012129.
Open this publication in new window or tab >>Optimal flow control of vortex breakdown in a laminar swirling flow
2024 (English)In: The 17th Asian International Conference on Fluid Machinery (AICFM 17 2023) 20/10/2023 - 23/10/2023 Zhenjiang, China / [ed] Yuan Shouqi, Institute of Physics (IOP), 2024, article id 012129Conference paper, Published paper (Refereed)
Abstract [en]

In highly swirling flows, such as hydraulic turbines operating under part-load (PL) conditions, vortex breakdown occurs and performance is impaired. Consequently, it is imperative that mitigation measures are taken. In the present study, a laminar swirling flow with a vortex breakdown at a Reynolds number of 180 is investigated. At the inlet, a swirling velocity profile with a swirl number of 1.095 is set. A stability analysis is conducted to identify unstable modes based on the assumption that vortex breakdown is a global instability. The results indicate that spiral modes with wave number 1 are unstable. An optimal flow control method based on the Adjoint method is then utilized to mitigate vortex breakdown. In the present study, the control method targets vorticity using a minimization algorithm. Control variables include radial and axial body forces. According to the results, the method was effective in mitigating vortex breakdown. A stability analysis conducted during the control process revealed that as the vorticity decreased, the growth-rate of the eigenvalue decreased, indicating that the flow is stabilized.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2024
Series
Journal of Physics: Conference Series, ISSN 1742-6588, E-ISSN 1742-6596 ; 2707
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104953 (URN)10.1088/1742-6596/2707/1/012129 (DOI)2-s2.0-85188256545 (Scopus ID)
Conference
17th Asian International Conference on Fluid Machinery (AICFM17), Zhenjiang, China, October 20-23, 2023
Note

Full text license: CC BY 3.0; 

Available from: 2024-04-03 Created: 2024-04-03 Last updated: 2024-04-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-7599-0895

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