bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of labyrinth clearance on the hydrodynamic performance of a high head Francis turbine
Authors: Kamal M M , Devinar L , Abbas A 
Published: December 2024

Abstract
Francis turbines have a leakage loss from the corresponding labyrinth seals i.e., crown side and a skirt side labyrinth clearance. Therefore, the labyrinth clearance between the runner and turbine cover plays an important role in the hydrodynamic characteristics of the hydro turbine. Generally, the geometrical details of labyrinth clearance are not considered in the numerical model due to complexity involved in modelling and requirement of high computational power that may lead inaccurate prediction of performance of the turbine. In the present investigation, steady-state numerical simulations have been performed on a high head Francis turbine, under different operating conditions, ranging from part load to overload condition, to assess the influence of labyrinth clearance on the hydrodynamic performance of the turbine. FVM method (as discretization method) along with SST k-omega turbulence model has been adopted for computational modelling. The simulation results such as hydraulic efficiency and power output are validated with model test results which was done as per IEC 60193 standard and found satisfactory agreement. Further, the axial thrust force is also computed for different operating conditions and compared with model test results. Based on the simulation results, it has been found that the hydraulic efficiency of turbine with labyrinth clearance was found 0.4% - 1.1% lower than the turbine without labyrinth clearance. The influence of labyrinth clearance on the turbine performance is higher at part-load condition compared to other operating conditions. It is observed that the leakage loss is almost same for all loading conditions at a particular head and fall in the range of 0.61% - 0.81%. Further, the value of axial thrust increases with the increases in discharge value and value of maximum axial thrust was found as 203 kN at overload condition.
On the effect of flow rate on pressure fluctuations and cavitation characteristics in a novel bulb turbine
Authors: Shandilya S , Das S P , Chatterjee D 
Published: December 2024

Abstract
Bulb turbines, having low excavation cost, are promising solutions for harnessing energy from low/ultra-low head run-of-the-river hydropower sources. A novel bulb turbine with no guide vanes, having a uniform efficiency over a range of discharges, is tested. Unsteady numerical simulations are carried out for this bulb turbine over a range of ± 30% of the design flow rate (Q
d) of 0.25 m3/s. Using a normalised Q-criterion to quantify the intensity of swirling flow inside the draft tube, the strong presence of hub and tip vortices is detected. The strength of these vortices increases with an increase in the flow rate. The amplitude and pattern of pressure fluctuations, monitored at different planes along the longitudinal direction, confirm the presence of vortex structures. Frequency analysis of pressure fluctuations shows that the blade passage frequency of the runner is the dominant frequency. With a flow field exhibiting significant fluctuations, a cavitation study is required to characterise the turbine. A turbine operating at various flow rate conditions is susceptible to encountering cavitation, especially at off-design conditions. The current study reports the effect of partial cavitation on the turbine performance at different discharges and assesses the suitability of the novel design from a cavitation perspective.
Design and Development of Guide Vane Cascade Test Rig
Authors: Sahu Rohit , Kumar Sandeep , Gandhi Bhupendra K 
Published: December 2024

Abstract
Flow instabilities around guide vanes of the Francis turbine directly contribute to the pressure pulsation, which is caused by rotor-stator interaction at the inlet of the runner. An experimental guide vane cascade rig is being developed at the Indian Institute of Technology Roorkee, whose flow field is set up to match the actual turbine’s. The test rig is designed for a maximum discharge of 0.06 m3/s in the closed loop, and provisions are made for particle image velocimetry to investigate the flow field around the clear plexi guide vane. Periodic walls of the flow channel between guide vanes are identified as the starting profile for the boundary of the cascade. The cascade will be made of a transparent acrylic sheet with a PIV window size of 230 mm X 59 mm to use a laser system. A 6 mm diameter pressure sensor measures pressure at the suction and non-suction sides of the guide vane. This paper presents the design and arrangements of the test rig components according to the discharge condition. Scale-down design calculations for the turbine are done using IEC 60193. The numerical model of guide vane cascade is prepared using ANSYS CFX. The numerical flow field investigation of the cascade is carried out to find the pressure and velocity distribution at the mid-span location and around the pressure and suction side of the guide vane at best efficiency point. The cascade’s inlet and outlet flow conduits have been optimized through computational fluid dynamics to check the pressure drop across the cascade and match the flow field to the actual turbine. Based on CFD results, the final layout of the test setup will be designed and manufactured.
Experimental and Numerical Investigation of Hydraulic Axial Thrust Fluctuation due to Draft Tube Vortex at partial load on Francis turbine
Authors: Tamura Yuta , Chugun Atsushi , Obuchi Ryomei , Ishihara Tomoaki 
Published: December 2024

Abstract
Operation range extension of Francis turbine is beneficial for effective use of hydraulic energy. However, the swirl flow in the draft tube of Francis turbine becomes large at the operating point far from the design point. As a result, the draft tube vortex occurs and this unsteady behaviour causes various problems such as pressure fluctuation, vibration and noise. Regarding the vibration, the correlation between the draft tube vortex and axial thrust fluctuation was revealed by the model test and CFD analysis in this research.
In the model test, the pressure fluctuations were measured on the upper draft tube and the back chamber of runner crown. The axial thrust fluctuation of runner was measured by thrust meter on the rotational shaft. The unsteady behaviour of the draft tube vortex was captured through photos using high-speed cameras from side of upper draft tube and bottom of the bent draft tube. For the CFD simulation, the assembly of guide vane, runner, draft tube, back chamber of runner crown and the side chamber of runner band were modelled. Both study and unsteady simulation was carried out. From the CFD simulation results the pressure fluctuation at each measuring point and unsteady behaviour of draft tube vortex were obtained and compared with the model test data. Besides, the axial thrust force exerted on runner with respect to time was compared with the thrust fluctuation measured during model test. As the behaviour of draft tube vortex depends on operating point, the pressure fluctuation and thrust fluctuation were also measured from no load to full load condition during the model test. Furthermore, additional unsteady simulations were carried out at the operation point, where the increased thrust fluctuation was observed. As the result, the multiple (3~5 in number) short draft swirls formed with similar circumference as the balance holes at that flow rate. When the low-pressure regions were far from the balance holes, the pressure on the back chamber of the runner was high, and then the axial force on the runner back surface increased. On the other hand, when the low-pressure regions were closer to the balance holes, the pressure on the back chamber decreased, and then thrust on the back surface decreased. This cycle was repeated, causing the hydraulic thrust fluctuation.
Numerical analysis and runner shape optimization of a high head pump-turbine
Authors: Chirkov D , Ustimenko A , Rigin V , Semenova A , Skorospelov V , Turuk P , Seleznev V 
Published: December 2024

Abstract
A set of numerical approaches ranging from the time-consuming unsteady full turbine RANS approach to a very fast periodic steady-stage approach were considered for CFD simulation of flow in Francis pump-turbines. Their computational efforts and accuracy of efficiency prediction were assessed through comparison with experimental data in both pump and turbine modes. It was shown that the unsteady full turbine approach is needed for accurate simulation of low discharge regimes in pump mode. From the other hand, near the optimum and in the high discharge zone, periodic steady-stage approach can be utilized. Next, an approach for multi-objective runner shape optimization of pump-turbine runners was proposed. Thirty free design parameters allowed flexible variation of runner blade shape, hub and band curves, as well as the height of the distributor, linked to the guide vane opening angle. Two or three reference operating points, indicating the turbine performance and head in both turbine and pump modes, were taken for optimization. Cavitation characteristics were accounted for through special constraints. The approach was tested for a 500 m head pump-turbine. It was shown that the optimized runners significantly outperform the initial one in terms of efficiency with comparable cavitation performance.
Analysis of mode-switching of a contra-rotating pump-turbine based on load gradient limiting shutdown and startup sequences
Authors: Fahlbeck J , Nilsson H , Salehi S 
Published: December 2024

Abstract
The contra-rotating pump-turbine (CRPT) is investigated as a runner configuration enabling more efficient low-head pumped hydro storage (PHS). To enhance the flexibility of low-head PHS with a CRPT, it is important to examine mode-switching. This study examines two mode-switching sequences for the CRPT, one turbine-to-pump and one pump-to-turbine. The mode-switching sequences are made as a combination of shutdown and startup sequences of each mode. The goal is to avoid pump and turbine brake modes while maintaining smooth load gradients. The turbine shutdown of the turbine-to-pump mode-switching involves a multi-stage valve closure to reduce the rotational speed of the runners, followed by the pump startup based on a previously optimised sequence. The pump shutdown of the pump-to-turbine mode-switching involves a gradual valve closure and rapid speed down of the runners at the end of the sequence. This is followed by the turbine startup, where a valve opens to generate sufficient flow over the runners before increasing the rotational speed of the runners simultaneously. Both mode-switching sequences require approximately 5 s each, and the largest loads are experienced during the pump mode parts of the sequences. The analysis is carried out using transient computational fluid dynamics with the OpenFOAM open-source software.
An innovative approach to PID governor upgrade for reaching SFC regulation stability
Authors: Dolenc D. , Pekolj J. , Ješe U. 
Published: December 2024

Abstract
Due to the growing number of renewable power sources in electrical grids, there is a need for expanding the number of generating units capable of providing power-frequency ancillary services. Hydropower is emerging as a viable provider of secondary frequency control (SFC) however, many units, esp. those with complex waterway systems, cannot achieve the stability requirements for SFC using conventional PID governors. In the paper, an innovative approach to a PID governor upgrade for a hydropower plant Alpaslan-2 in Turkey is presented. The modelling of the hydraulic system and turbine governor was implemented and tested in the computer software SIMSEN. An upgraded PID governor includes a wicket gate manoeuvring compensation loop, surge tank level oscillation compensation loop, and a feed forward loop. With the improved model, we achieved (in a simulation and on site) a load fluctuation inside the ±1% load range during small and large load reference changes. This allowed the Alpaslan-2 HPP to conform to the Turkish grid SFC and primary frequency control (PFC) requirements.
Large eddy simulation analysis of Francis turbine: A comparison with experimental data and investigation of vortex rope dynamics in the draft tube
Authors: Ramdani Soufiane , Shingai Kenji , Kobayashi Katsutoshi , Sato Koma , Tamura Yuta 
Published: December 2024

Abstract
The rapid deployment of renewable energy is pushing for an increased use of hydro turbines operating at part load conditions. This is done to enable a quick response to shifts in demand and to compensate for fluctuations in supply from other electricity sources. In these conditions, pressure pulsations in the draft tube are generated which affects the structural behaviour of the machine as well as the hydraulic circuit. This research aims to improve the prediction accuracy of pressure pulsations of Francis turbines in the partial load operation using computational fluid dynamics (CFD) simulations. The obtained numerical approach will contribute the decrease of the pressure pulsations in the hydraulic power stations. In this study, the unsteady LES using the FrontFlow/Blue (FFB) solver is adopted and validated. Results for the case with guide vane openings (GVO) set at 50% reveal the presence of a vortex rope in the draft tube, validated by experimental imagery. Fast Fourier transform analysis highlights a frequency corresponding to the vortex rope’s precession speed.
1D-3D co-simulation pipe resonance induced by cavitating vortex shedding
Authors: Alligne S , Veuthey N , Béguin A , Ruchonnet N , Nicolet C 
Published: December 2024

Abstract
Hydraulic systems may experience excitation caused by complex flow patterns within various components of the system. A computational effective way to predict the interaction between the hydraulic system and the excitation source is to conduct a co-simulation using two independent simulation codes. One code models the fluid pipe system using a one-dimensional compressible approach, while the other code simulates the excitation source with a three-dimensional model. Recognized as a standard communication protocol for linking two simulation codes that solve a system of ordinary differential equations, the Functional Mockup Interface, FMI, protocol has been implemented in SIMSEN to couple with the Ansys CFX software solution. Localized hydrodynamic instabilities including cavitation are prone to interact with the entire system. A cavitating case study has been investigated to assess robustness and accuracy of the co-simulation performed with the FMI protocol. The case study consists in a straight pipe connecting two constant pressure tanks with a bluff body placed at 3/4 of the pipe length. The vortex shedding is the excitation which frequency is proportional to the flow velocity. Measurements are available for resonant and non-resonant conditions in cavitating and free cavitating flow regimes. Co-simulations are performed between SIMSEN 1D model of the pipe and a pseudo 3D CFX model of the bluff body, reduced to one cell in the width direction. The comparisons with measurements show good agreement despite the pseudo 3D approach to simulate bluff body-induced excitation. This demonstrates that this approach is valid to address complex unsteady, compressible and cavitating flow phenomena.
Analysis of the impact of magnetic and electric fields on the environment within the free space of SUTT segment Ulee Kareng - Banda Aceh
Authors: Hizas S , Gani A , Sara ID 
Published: December 2024

Abstract
Public concerns exist regarding the potential negative impacts of magnetic and electric fields generated from SUTT lines on the environment and health. This study investigates the validity of this public concern by measuring and analyzing the magnitude of the magnetic and electric fields to determine if they remain within safe limits according to SNI, IRPA, and WHO standards. The study aims to mitigate the negative impact of SUTT on research locations including highway areas, plantations, rice fields, and brick houses, chosen using purposive sampling. This study found that the highest electric field value was measured in the plantation area at point A2 (2.1367 kV/m) and the lowest in the brick house area at point A5 (0.1795 kV/m). The highest magnetic field value was measured in the rice field area at point A5 (1.6363 μT) and the lowest in the road area at point B2 (1.5517 μT). SUTT operators monitor the magnetic and electric fields around the transmission area to ensure that the values remain within safe limits. Therefore, it is recommended to manage the vegetation around the transmission area to prevent interference with SUTT performance and to ensure that vegetation does not become an unwanted electrical conduction path.
Attitudes, awareness, and knowledge of Wolbachia-aedes aegypti technology in Yogyakarta: a survey
Authors: Jassey B , Yudhastuti R , Notobroto H B , Azizah R , Candraning D K , Ridha M R , Indrayani R , Sulistyorini L , Jalaludin J , Manjang B , Permatasari F I 
Published: December 2024

Abstract
In 2014, Yogyakarta initiated the release of male Wolbachia-Aedes mosquitoes as a supplementary measure to vector control efforts, targeting the suppression of Aedes aegypti mosquitoes in designated study areas. Concurrently, with the ongoing expansion of the Randomized Control Trial of Wolbachia in Yogyakarta to encompass broader regions, a household-based survey was conducted between January and June 2024 across two Project Wolbachia study sites. The survey utilized a structured questionnaire to gauge current public sentiments and identify the need for enhanced public messaging and engagement. Factors influencing awareness, attitudes, and knowledge towards Wolbachia-Aedes technology were examined using Pearson’s Chi-square test and binary logistic regression analysis. Among the 1000 respondents, 80.8% reported a Randomized Control Trial of Wolbachia in Yogyakarta awareness. However, the level of detailed knowledge about Wolbachia-Aedes technology was notably lower, indicating significant knowledge gaps that necessitate improved communication and educational efforts to counter misinformation. The survey revealed that prolonged exposure to the project correlated with higher awareness, while higher educational attainment was linked to better knowledge levels. Additionally, younger age groups and individuals with higher education levels demonstrated greater project acceptance. Trust and acceptance levels towards the project were generally high among the population. The public’s favorable perception of the project underscores the success of the current public communication strategies and will support the program’s future expansion.
Environmental influences on sleep quality in university dormitories
Authors: Budiawan Wiwik , Prastawa Heru , Merdeka Gusti Fattahilah Putra , Ari Shania Mustika 
Published: December 2024

Abstract
Environmental factors play a critical role in determining sleep quality, which is essential for physical and cognitive restoration. Key environmental parameters such as ambient temperature, relative humidity, CO2 levels, and particulate matter (PM2.5) have been identified as significant contributors to sleep disturbances. This study investigates the impact of university’s dormitory environmental conditions on student’s sleep quality. By understanding these influences, we aim to provide data-driven recommendations for optimizing the dormitory environment to promote better sleep quality. The findings revealed that students’ sleep quality was poor, with subjective measures such as a Pittsburgh Sleep Quality Index (PSQI) score above 5 and Sleep Onset Latency (SOL) over 20 minutes, and objective measures showing less than 7 hours of total sleep time, REM sleep percentage below 25%, and NREM sleep percentage under 75%. High average temperatures of 29.79°C and relative humidity of 88.70% were significant environmental factors associated with poor sleep quality. Additionally, CO2 and PM2.5 concentrations exceeded safe limits, contributing to respiratory discomfort and reduced sleep quality. Thus, improving the dormitory environment at UNDIP is essential for enhancing sleep quality.
Effectiveness of commercial bioactivator in biofilters on acclimatization time and reduction of BOD and COD in cracker industrial wastewater treatment
Authors: Hamdani A , Hadiyanto  , Sudarno  
Published: December 2024

Abstract
Indramayu is one of the regions with a fish cracker processing industry with production output of 3.5 thousand tons or 45.20% of the total production of processed fishery products. The production of fish crackers produces wastewater which increase organic pollutants in wates that exceed quality standards. The study aims to determine the effectiveness of commercial bioactivator on acclimatization time and the reduction of COD and BOD levels in liquid waste of the cracker industry by using anaerobic-aerobic biofilters on andesite stone fragment media. Based on the results of this study, the bioactivator was able to reduce COD concentration from 2337.71 mg/L to 196.94 mg/L and BOD concentration from 653.6 mg/L to 95.09 mg/L. The final ratio of BOD/COD increased from 0.22 at 4 hours to 0.47 at 24 hours indicating a shift into the biodegradable zone. The total COD removal efficiency reached 91.42%, while BOD removal efficiency reached 85.26%.
Analysis of Carbon and Nitrogen Content in Organic Waste Processed by Bio-drying with a Hot Air Flow System
Authors: Suryantara A R , Samadikun B P , Zaman B , Hardyanti N , Putri N S , Purwono P , Failusuf T A M , Oktiawan W 
Published: December 2024

Abstract
The biodrying method is used in mechanical biological treatment facilities, focusing on the rapid reduction of moisture content through the heat generated by the degradation of organic matter. Analysis of changes in carbon and nitrogen content in the biodrying process of organic waste with a hot airflow system is essential to understand the biodegradation process and the quality of the final product. This study aims to analyze changes in carbon and nitrogen content in organic waste biodrying with a hot air flow system. This research method uses a biodrying reactor made of concrete with a thickness of 10 cm. Reactor dimensions 80 x 250 cm. The composition of the sample consisted of cabbage waste, kale waste, spinach waste, dried leaves. The samples are chopped, mixed and fed into a bio drying unit. Hot air was flowed to the bio drying unit. The result show that the carbon concentration of the initial sample is 39.21%. The highest carbon concentration occurred at the 20th minute at 92.30%, while the lowest value occurred at the 25th minute at 14.18%. The highest value of nitrogen concentration occurred at the 20th minute of 2.23%, while the lowest value occurred at the 55th minute of 0.16%. The highest change occurred in the time interval of 15 minutes to 25 minutes.