Water Head Research Articles

Vortices Evolution Characteristics and Pressure Pulsations of Variable-speed Francis Turbine

Abstract The stability of Francis turbine under low load conditions has become the focus in the power grid dominated by variable renewable energy. In this paper, the variable-speed approach is used to explore the operating characteristics of the Francis turbine, the RANS/LES hybrid turbulent model is adopted to investigate the fluid structure evolution process, and using the Q-criterion depicts the vortex cores. The results show that the numerical simulation agrees well with the experimental data acquired from the model test. It is found that the variable-speed operation can effectively eliminate the vortex ropes in the draft tube. Unexpectedly, the vortices in the runner will evolve from the separated vortices at the runner outlet for the fixed-speed Francis turbine to the inter-blade vortices at the runner inlet for the variable-speed Francis turbine in the case of small guide vane opening. It is concluded that the optimum operating range of a variable-speed Francis turbine (VSFT) should be within ±30% rated speed and 60% to 100% opening, and the pressure pulsation coefficient in the draft tube can be reduced from 7% to 1% at minimum water head, the output and efficiency of the turbine are increased by about 30% and 10% respectively.

Comparing labyrinth and ogee spillways at high hydraulic heads – a case study in Zambia

A new over-the-dam spillway and 3 m dam raising were selected as the preferred option for resolving matters in the interest of safety for an existing dam in Zambia. The cost of supplying concrete at the dam site had the greatest effect on overall project capital costs, and thus optimising the size of the concrete spillway was critical. Both ogee and labyrinth weir designs were developed for a hydraulic head of 5 m in the Safety Check Flood. The ogee shape design was developed to achieve high efficiency and required a weir width of 81 m. For labyrinth weirs, a limiting factor to the allowable head is the ratio between the water head and weir height above its foundation apron. Using published state-of-the-art research, 60 labyrinth weir configurations were tested, with varying angles, leg lengths and number of cycles. The optimal labyrinth configuration was chosen as the one with the minimum overall spillway width 64 m, and volume of concrete. This configuration provided a 23% potential reduction in concrete volume compared to the ogee. The labyrinth design was taken forward for computational fluid dynamic modelling to prove the concept and for further development into a detailed design.

An experimental study on the impact of particle surface wettability on melt infiltration in particulate beds

Melt infiltration into porous media is an intriguing phenomenon that holds immense significance across various sciences and technologies. In this work, the problem of metallic melt infiltration in particulate beds is investigated for understanding and prediction of severe accident progression associated with a molten pool penetrating through an underlying debris bed which may form in the reactor core or in the lower head of a light water reactor.The present study aims to quantify the effect of particle surface’s wettability on melt infiltration kinetics. For this purpose, two categories of experiment are conceived and carried out to measure the wettability of different material surfaces by melt and to characterize melt infiltration kinetics in one-dimensional particulate beds, respectively. The melt material is tin–bismuth eutectic alloy with a melting point of 139 °C. Copper (Cu), stainless steel (SS), Tin (Sn) and tin-coated stainless steel (Sn-coated SS) are chosen as materials of substrates and particles in wettability measurement and melt infiltration study. The particulate beds, packed with 1.5 mm spheres, are preheated to 200 °C before the melt infiltration begins.The experimental data of wettability measurement shows that the contact angles of liquid Sn-Bi eutectic on the above-mentioned material surfaces range from 79° to 135°. The results of melt infiltration tests confirm the significant effect of wettability on melt penetration kinetics. The capillary force plays a significant role in the initial infiltration of particulate beds. Specifically, a wettable particulate bed enhances the initial melt infiltration, whereas non-wettable beds hinder it.

Numerical simulation of wave-number effects on the performance of traveling wave pump-turbine in turbine mode

Pumped storage represents an economically viable, highly efficient, and extensive energy storage solution, receiving substantial research attention worldwide. This study utilized the energy dissipation of fish swimming in the water, and the traveling wave plate was arranged in a vertical rectangular flow channel to obtain energy through reverse thinking. Numerical simulation was employed to investigate the performance characteristics of the traveling wave turbine under varying wave number across high and low water head. The results reveal that the efficiency at low water head starts to increase and then decreases with the increase of wave number. There is an optimal wave number N = 4 to maximize turbine efficiency, and the maximum efficiency under low water head condition is 89.35 %. The efficiency of the high head condition shows a continuous upward trend, with a maximum value of 92.27 % in the range of wave number studied. With the increase of wave number, the instantaneous mass flow coefficient and power coefficient become more stable. The advantage of increasing the wave number is that more traveling wave plates can participate in energy capture, which is conducive to reducing the force required by each traveling wave plate and making the pressure distribution in each working cavity more regular.

Experimental and numerical investigation of rectangular labyrinth weirs in an open channel

Labyrinth weirs are commonly used to increase the discharge efficiency in free-overflow discharges. These weirs provide a higher discharge efficiency than conventional linear weirs at the same headwater. In this study, the hydraulic performance of rectangular labyrinth weirs (RLWs) under different geometries and flow conditions was investigated experimentally and numerically. The numerical model was verified and validated using the grid convergence index method and experimental data. Numerical modelling results showed increased performance of the RLW due to the distribution of lateral velocities in the inlet keys, while nappe interference in the downstream keys led to a decrease in performance at high headwater. Within the limitations of 1.5 ≤ L/B ≤ 2.33 and 0.1 < Ho/P < 0.61 (L is the weir crest length, B is the channel width, Ho is the total water head and P is the weir height), a performance increase of 44% on average (maximum increase of 67%) for unit channel width was found for RLWs compared with linear weirs. For these limitations, two new empirical formulas with a high correlation were derived to estimate the discharge coefficients of RLWs based on B and L for Ho/P > 0.1, which are widely used in practice. When compared with some data in the literature, the empirical formulas produced satisfactory results.

Numerical simulation of temperature field of a new type of freezing device under seepage effect.

In order to investigate the development of the temperature field of a new type of freezing reinforcement under seepage conditions, in this paper, COMSOL finite element software was used to simplify the model and simulate the effect of groundwater seepage on the development of the temperature field of frozen pipes by coupling the Darcy's law module and the heat transfer module for porous media. The heads of water were also varied to simulate the change in seepage velocity to further investigate the effect of seepage velocity on the temperature field. The results of the study show that the freezing wall formed in the high head region was thinner than that in the low head region due to the effect of seepage, and this phenomenon was aggravated with the increase of seepage rate; The effect of seepage action on the temperature field had a hysteresis along the seepage direction; When the seepage rate was greater than 1.65 m/d, the soil in the center of the device feezed better and could form a tight and dense freezing wall comparable to the size of the freezing device; When the seepage rate was greater than 5.78 m/d, the temperature of the center soil body gradually increased, and eventually the freezing curtain cannot be formed.

Analysis of the impact of uneven permeability of surrounding rock caused by the coupling effect of ground stresses and fault structure on sudden water inrush in tunnels

Affected by fault structure and in situ stress, the heterogeneity of the permeability of surrounding rock is universal. Treating it as a fixed value will reduce the prediction accuracy of water inflow and structural head. In view of this problem, considering the coupling effect of ground stress and fault structure, the permeability of surrounding rock is regarded as a spatially discrete type, a plane one-dimensional seepage calculation model in the vertical section is constructed, and the phreatic surface drop curve equation is established. Using Taylor's formula and series expansion theorem, the equation can be reduced to the expression of the falling curve when the permeability of the surrounding rock is homogeneous. Based on Darcy's law and the law of conservation of fluid mass, the calculation formula for tunnel water inflow and external water pressure of the structure was derived and verified through ongoing construction projects. Research shows that the calculation error of water inflow can be reduced from 23.1% to 7.5% when considering the influence of ground stress and fault structure on the permeability of surrounding rock, and the calculation error of water head borne by the supporting structure can be reduced from 43.8% to 30%, which improves the prediction accuracy. Thematic collection: This article is part of the Climate change and resilience in Engineering Geology and Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/climate-change-and-resilience-in-engineering-geology-and-hydrogeology

Harvesting Electricity from Water Pipeline in Hydro Power Generator

The purpose of this endeavour is to build a small-scale hydroelectric power plant that can produce energy for household use using water from a storage tank. One trustworthy and efficient kind of clean, green power is picohydroelectricity. It generates electricity with low maintenance and no fuel use. Water moving through residential pipes provides the kinetic energy to generate electricity for storage of energy. The design and construction of a pico-hydro generating system that extracts water from the water tanks of residential buildings are covered in this study. Three unique mechanical arrangements are added for improved operation and energy production: U-tube piping, a big nozzle pipe end, and an air bladder for sustaining water pressure. As a result, we might design a mechanical system which could produce electricity using the potential energy contained in a water storage tank from a water head. Key words: Renewable energy, Hydroelectricity, turbine , diaphragm pump, portable etc.

Experimental investigation on the characteristics of seepage failure of landslide dams with strongly permeable zones

Landslide dams are formed by river blockages caused by landslides or other slope instability bodies. They exhibit loose structure, poor stability and strong permeability. Large water head caused by water-level increase can trigger seepage deformation of soil and influence the stability of landslide dams, possibly leading to dam breach and catastrophic damage. Various landslide dam structures also result in differences in seepage characteristics. In this study, multiple physical model tests for seepage failure of landslide dams with strongly permeable zones were designed. The influence of the location and gradation of the strongly permeable zones on the seepage of landslide dams was studied. The characteristics and modes of seepage failure of landslide dams with strongly permeable zones were analysed. The experimental results showed that the cyclic evolution failure of piping and downstream slope collapse was an essential failure mode for the seepage-induced failure of landslide dams with strongly permeable zones. Compared with the strongly permeable zone at the bottom of a landslide dam, the piping caused by seepage evidently promoted the slope erosion of the dam with the strongly permeable zone in the middle. As the permeability coefficient of strongly permeable zones increased, piping was faster and easier to form, and piping failure, slope erosion, and slope collapse were more severe. The seepage failure of landslide dams mainly included the emergence of seepage water, piping, slope erosion, and downstream slope collapse. Piping was caused by the erosion and migration of some fine particles of soil in seepage channels in the dam. When the flow drag force could overcome the resistance force among the soil particles, some fine particles and even large particles on the downstream slope surface were continuously eroded. This study provides new insights into the evolution process and breach mechanisms for the seepage-induced failure of landslide dams with strongly permeable zones.

Ultimate water level and deformation failures of the artificial dam in the coal mine underground reservoir

Coal mine underground reservoirs provide a new choice for the protection and utilization of water resources. This paper takes the underground reservoir of Wulanmulun Mine as the background, and takes the MB-1# artificial dam in the goaf of 31104–31116 working face of 3–1 coal seam as the research object. The theoretical model of artificial dam is established by elastic–plastic two-way slab theory, and the theoretical mechanical analysis and calculation are carried out. A similitude physical model for the coal mine underground reservoir was built by using the self-developed nested dual-dynamic-pressure similitude simulation testing system. Later, the mechanical response and deformation failure features of the artificial dam under different water pressure values were analyzed and the ultimate water pressure was determined. In addition, FLAC3D was used to determine the stress-seepage field-coupling model for the artificial dam. Using this model, the influence of water pressure on the multi-load coupling effect of the artificial dam and coal pillar dam was characterized. The dam form is optimized and the safety water level evaluation method of the dam body is proposed. The research results are as follows: (1) Based on the theory of elastic–plastic two-way slab, the theoretical analysis model of artificial dam is established, the expression of the ultimate water level function of artificial dam is derived, and the theoretical ultimate water head is determined to be 18.2 m (2) The seepage law of underground reservoir under different water pressures is obtained, and the ultimate water pressure of the model is determined to be 11.43 kPa. (3) It is clarified that the failure modes of the artificial dam are seepage failure and mechanical failure, and it is revealed that the groove area is the weakest position where the dam is most vulnerable to failure. In view of the failure modes of the dam, the I-shaped structure artificial dam is proposed. (4) A safe water level assessment method is proposed for the constructed artificial dam. According to the analysis of on-site monitoring data of MB-1# dam, the actual water level in the reservoir is within the allowable water level range of the artificial dam, and the whole reservoir is in a stable and relatively safe state at present. The reliability of this assessment method has been verified.

Fire Prevention in Buses Using Water Head and AWO System

Abstract: Buses can be designed to carry many passengers ,and in public places, incidents such as bus fires impose a relatively high threats to assets and lives. Hence, it is common to witness substainal casualties when a bus fire occurs .Fire diaster is common threat to lives and property . An IOT based automatic window opening system when smoke is detected by sensors is efficient one but ,this paper represents with a doubt if any one is struck on the bus ,this project helps to save their lives that keeping the steel pipes inside and outside of the bus and providing sprinkles and holes to the pipe In and Out side of the side of the bus in respectively. When some amount of fire/flame and smoke is detected by the sensors the water and foam mixture pass through the pipes and spreads over the bus.The rectangular water and foam storage tank is kept on the roof of the bus .The equipment here is the foam that can resists the fire so, Silicon Foam is the flame-retardant, self-extinguishing and can withstand 2100℃ flame .This project helps minimizing and delaying the spread of fire

Numerical Simulation Study on The Ultimate Water Head of Artificial Dam in Coal Mine Underground Reservoir

In order to improve the problem of low utilization rate of groundwater in the process of coal mine production, some mining areas in northwest China use the goaf of the working face as a water storage space, and establish underground reservoirs to realize water retention mining. In order to solve the problem of the stability of the artificial dam of the underground reservoir, this paper takes the underground reservoir of the 51103 working face of Guojiawan Coal Mine as the engineering background, and uses the FLAC3D numerical simulation software to establish the artificial dam model, and the experimental results show that when the head height is 26m, the maximum tensile stress inside the dam is 1.264MPa, which is still lower than the limit of the tensile strength of the concrete, until the water pressure increases to 27m, the maximum tensile stress inside the dam is 1.290MPa, which is greater than the limit of the tensile strength of the concrete, so the ultimate head height of the artificial dam is 26m.

Experimental Study on Two-Phase Countercurrent Flow Limitation in Horizontal Circular Pipes

The two-phase countercurrent flow limitation (CCFL) in horizontal channels is important in relation to nuclear reactor safety. In this study, we aim to investigate the CCFL characteristics and the flow behaviors in horizontal circular pipes with small diameters. The effects of pipe diameter and the water head in the upper plenum on CCFL characteristics are experimentally studied. An image-processing technique and statistical treatments are implemented to analyze the horizontal countercurrent flow. The results show that the CCFL characteristics for the horizontal circular pipes with small diameters can be well correlated using the dimensionless parameters, which are based on adding fluid viscosity to the Wallis parameters. The CCFL characteristics are significantly affected by the pipe diameter and are slightly affected by the water head above the horizontal pipe. The gas–liquid interface fluctuates with certain periods, and flow pattern transitions happen in the horizontal air–water countercurrent flow. As the air flow rate increases, the occurrence location of the liquid slug appears to shift towards the water entrance. In addition, the further away from the water entrance, the lower the average of liquid holdup.

Investigations on the performance of bottle blade overshot water wheel in very low head resources for pico hydropower

Abstract An overshot water wheel is considered as a low-cost and simple alternative for rural electrification. Hence, the aim of this study is to develop a noncomplex geometrical design of an overshot water wheel, namely, bottle blade overshot water wheel (BOWW), yet effectively operated for pico hydropower generation. The BOWW and hydro system were assessed at very low water head conditions, namely, 0.3, 0.4, and 0.5 m water head using a water test rig. According to the experimental results, the BOWW equipped with eight blades when operated at 0.5 m head produced significant mechanical power and electrical power up to 48.58 and 15.55 W. Analytically, the turbine with eight blades has 26.8–49.1% efficiency. Meanwhile, the effectiveness of four blades is between 5.66 and 28.96%. The results showed that eight blades performed well. Finally, it proves that, with a very low water head and low flow rate, the proposed system can perform and produce a significant power output for power generation.

Feasibility of Microbially Induced Carbonate Precipitation to Enhance the Internal Stability of Loess under Zn-Contaminated Seepage Conditions

Loess is widely distributed in Northwestern China and serves as the preferred engineering construction material for anti-fouling barriers. Heavy metal contamination in soil presents significant challenges to the engineering safety of vulnerable loess structures. Hence, there is an urgent need to investigate the impact of heavy metal ions on their percolation performance. In order to investigate the effectiveness of microbially induced carbonate precipitation (MICP) using Sporosarcina pasturii (CGMCC1.3687) bacteria in reducing internal seepage erosion, a saturated permeability test was conducted on reshaped loess under constant water head saturation conditions. The response of loess to deionized water (DW) and ZnCl2 solution seepages was analyzed by monitoring changes in cation concentration over time, measuring Zeta potential, and using scanning electron microscopy (SEM). The results indicate that the hydrolysis of Zn2+ creates an acidic environment, leading to the dissolution of carbonate minerals in the loess, which enhances its permeability. The adsorption of Zn2+ ions and the resulting diffusion double-layer (DDL) effect reduce the thickness of the diffusion layer and increase the number of free water channels. Additionally, the permeability of loess exposed to ZnCl2 solution seepage significantly increased by 554.5% compared to loess exposed to deionized water (DW) seepage. Following the seepage of ZnCl2 solutions, changes in micropore area ratio were observed, decreasing by 48.80%, while mesopore areas increased by 23.9%. MICP treatment helps reduce erosion and volume shrinkage in contaminated loess. Carbonate precipitation enhances the erosion resistance of contaminated loess by absorbing or coating fine particles and creating bridging connections with coarse particles. These research results offer new perspectives on enhancing the seepage properties of saturated loess in the presence of heavy metal erosion and the geochemical mechanisms involved.

A variable pressure water-sealed compressed air energy storage (CAES) tunnel excavated in the seabed: Concept and airtightness evaluation

For compressed air energy storage (CAES) caverns, the artificially excavated tunnel is flexible in site selection but high in sealing cost. A novel concept of building a water-sealed CAES tunnel in the seabed is proposed in this study, and the airtightness of the system is preliminarily evaluated. Based on the proposed variable pressure water-sealed CAES tunnel excavated in the seabed and combined with the actual operation of the system, a multifield and multiphase coupling calculation model for the airtightness calculation of water-sealed CAES tunnel under pressure changes was constructed, and the rationality of the model was confirmed by a case study. The airtightness analysis of the water-sealed CAES system is carried out. It is an effective method to excavate a tunnel in the seabed, and sealing the CAES system by utilizing the water head pressure in the pores of the rock mass and the low permeability of the rock mass. To satisfy the sealing requirements of the CAES system, the seawater depth of the tunnel should be deeper than 190 m if the gas pressure inside the tunnel is 4.5–10.0 MPa with the rock mass permeability of 1.0 × 10-16 m2 and the overlying rock thickness of 100 m, When the gas pressure inside the tunnel is 4.5–10.0 MPa, the overburden thickness is 100 m and the seawater depth is 50 m; the rock mass permeability should be less than 7.32 × 10-17 m2.

Application of One-Dimensional Hydrodynamic Coupling Model in Complex River Channels: Taking the Yongding River as an Example

River conditions are complex and affected by human activities. Various hydraulic structures change the longitudinal slope and cross-sectional shape of the riverbed, which has a significant impact on the simulation of water-head evolution. With continuous population growth, the hydrological characteristics of the Yongding River Basin have undergone significant changes. Too little or too much water discharge may be insufficient to meet downstream ecological needs or lead to the wastage of water resources, respectively. It is necessary to consider whether the total flow in each key section can achieve the expected value under different discharge flows. Therefore, a reliable computer model is needed to simulate the evolution of the water head and changes in the water level and flow under different flow rates to achieve efficient water resource allocation. A one-dimensional hydrodynamic coupling model based on the Saint-Venant equations was established for the Yongding River Basin. Different coupling methods were employed to calibrate the coupling model parameters, using centralised water replenishment data for the autumn of 2022, and the simulation results were verified using centralised water replenishment data for the spring of 2023. The maximum error of the water-head arrival time between different river sections was 4 h, and the maximum error of the water-head arrival time from the Guanting Reservoir to each key cross-section was 6 h. The maximum flow error was less than 5 m3/s, and the changing trend of the flow over time was consistent with the measured data. The model effectively solved the problem of low accuracy of the water level and flow calculation results when using the traditional one-dimensional hydrodynamic model to simulate the flow movement of complex river channels in the Yongding River. The output results of the model include the time when the water head arrives at the key section, the change process of the water level and flow of each section, the change process of the water storage of lakes and gravel pits, and the change process of the total flow and water surface area of the key section. This paper reports data that support the development of an ecological water compensation scheme for the Yongding River.

Estimating fracture characteristics and hydraulic conductivity from slug tests in epikarst of southwest China

Study regionGuizhou Province, Southwest China Study focusThis study aims to estimate the hydraulic conductivity (Kh) of the weathered rock fractures (epikarst) based on the best fitting of observed water head in 105 slug tests in the study sites. Specifically, comparisons of the estimated results from the analytical and numerical methods reveal the effects of changes in fracture flow conditions (e.g., steady and non-steady) on Kh for various fracture apertures and soil fillings. New hydrological insights for the regionThe results comparatively show that Kh from the analytical solution of steady flow was significantly underestimated, and the numerical modeling of the non-linear and unsteady flow can improve the water head fitting when the Reynolds number (Re) > 17.27. The optimized Kh ranges 0.014–2673 m/d and the mean value of Kh is about 100 times the median value, suggesting that epikarst flow might be controlled by a limited number of larger fractures. Moreover, the soil filling in large fractures (>10 mm) creates a turning point of the exponential increase of Kh with d. Comparatively, the naturally full-filling fractures resemble the soil matrix with a low Kh, and the partial-filling fractures can create preferential flow around the soil-rock interfaces with a high Kh. These results fundamentally improve our understanding of water infiltration, retention, and availability for plant uses in the karst areas of southwest China.

Analysis of hydraulic losses in the series from 1990 to 2022 at the Retiro small hydroelectric power plant

Hydraulic losses are a crucial variable in hydroelectric ventures as they can cause significant reductions in power generation. This article analyses the impact of hydraulic losses on the Retiro Small Hydroelectric Power Plant (SHPP), investigating their effect on monthly average power and, consequently, the efficiency of electricity generation. This study examines the historical series of load losses at the Retiro SHPP from 1990 to 2022. The calculations are based on flow data available in HidroWeb. The study considered the maximum and minimum flow rates in the historical flow series as constraints for hydropower generation. We used a multivariable function to calculate the efficiency of the hydraulic turbine, relating the turbine flow rate and the net water head. We developed mathematical relationships for head losses that occur in the grid, at the water intake, and due to friction from the intake to the turbine of the Retiro SHPP. The article presents a comparison between the actual monthly average power of the Small Hydroelectric Power Plant (SHPP) and the simulated monthly average power. We normalized the data for turbine flow and load loss to conduct statistical analysis. Kernel probability density was applied to understand the distribution shape of the data. Findings show that average monthly capacity is lowest in September, at approximately 0.81 MW. In March, the highest power occurs, approximately 14.19 MW. During the high flow period, the simulated average power, which accounts for load losses, closely matched the actual average power generated at the Retiro SHPP. In the months from July to October, despite being the period with the lowest head losses, it is the time when there is a greater opportunity to maximize energy generation at the power plant. An inefficient power generation system experiences significant load losses during specific periods of the year. To minimize this effect, it is crucial to understand the behavior of hydraulic losses and consider implementing mitigating measures.

POTENSI PLTMH DI BENDUNGAN SIDAN, DESA BELOK SIDAN, KABUPATEN BADUNG

The potential of new renewable energy is highly needed to support Clean Energy Bali, and one of the viable energy sources is Micro Hydro Power Plant (PLTMH). The design of the Sidan Dam PLTMH is based on the construction of the Sidan Dam area in Belok Sidan Village, Badung Regency. The planning of the Sidan Dam PLTMH only extends to the construction of the penstock. In this Capstone Project, the design of the Sidan Dam PLTMH utilizes water discharge and head height data from the Sidan Dam planning. This data is used to determine the design, type of water turbine, dimensions of the water turbine, and to determine the appropriate generator capacity. The calculation results indicate that the Sidan Dam PLTMH has a potential capacity of 290.83 kW with a Francis turbine type and a generator capacity of 472.59 Kva. It is estimated to generate an annual energy output of 1,783,396 kWh with a capacity factor 70%.