Hydraulic Flow Research Articles

Evaluation of Hydropower Potential of Kapologwe Waterfalls for Rural Electrification in Rungwe District, Mbeya Region Tanzania

Hydropower remains one of the most significant renewable energy sources, accounting for a substantial proportion of global electricity production. In Tanzania, where electricity access is limited, particularly in rural areas, untapped hydropower resources could play a critical role in meeting local energy needs. This study investigates the hydropower potential of the Kapologwe Waterfalls on the Kala River, located in Rungwe District, Mbeya Region. Key factors influencing hydropower generation, including hydraulic head, flow rate, and turbine efficiency, were analysed using land survey techniques and hydrological modeling. The hydraulic head was measured at 605.15 meters, and flow rates were calculated based on field data, with a design flow of 1.542 m³/s. A Pelton turbine, known for its high efficiency under high-head, low-flow conditions, was selected for the site. The estimated power potential is 7.238 MW, suggesting that the Kapologwe Waterfalls could significantly contribute to localised electrification and reduce reliance on Tanzania’s national grid. This research highlights the feasibility of small-scale hydropower projects in rural Tanzania and their potential to alleviate energy poverty.

Sedimentological and diagenetic impact on reservoir characteristics using hydraulic flow units: case study from lower cretaceous Aradeiba-Bentiu sequence reservoir rocks of Laloba Oilfield, SE Muglad Basin, Sudan

Sedimentological and diagenetic impact on reservoir characteristics using hydraulic flow units: case study from lower cretaceous Aradeiba-Bentiu sequence reservoir rocks of Laloba Oilfield, SE Muglad Basin, Sudan

Temporal asynchrony analysis for dynamic operation of hydraulic-thermal-electricity multiple energy networks based on holomorphic embedding method

Analyzing the operational states of multiple energy networks (MEN) in multi-energy systems is crucial for ensuring system stability. The dynamic operational characteristics of different energy flows pose challenges for computational analysis. Traditional steady-state methods are inadequate for addressing the dynamics of MEN, especially when dealing with temporal discrepancies between hydraulic and thermal flows in thermal networks (TN) and the heterogeneity between TN and electrical networks. Therefore, this paper proposes a novel holomorphic embedding method (HEM) based on multi-stage decomposition method. The developed HEM constructs a time coefficient matrix and utilize inner-outer loop recursion to handle the time lag between thermal flow and hydraulic flow in the TN. Additionally, we reconstruct a holomorphic matrix, integrating hydraulic flow to bridge thermal and electric power flows, thereby improving the operational heterogeneity among different networks. Real-case simulations show that when the Taylor expansion order in HEM is equal to 4, the proposed method achieves a mere 1% discrepancy from actual operational data, enhancing computational efficiency by 60% compared to the Newton-Raphson method. Moreover, in this real-case, the TN exhibits a maximum delay response time of 180s compared to electrical networks. Exploiting this delay time effectively increases renewable energy generation within multi-energy systems by 961.58kW per day.

Controls on Erosion and Cyclic Step-Formation Upstream of Waterfalls.

Waterfall retreat transmits base-level perturbations upstream, thereby providing markers of changing climate and tectonics. In homogeneous rock, waterfalls often retreat either by direct waterfall-face erosion or incision from repeating ('cyclic') steps formed above waterfalls. We lack knowledge on the conditions driving these different erosion styles, limiting our ability to predict waterfall retreat. We address this knowledge gap through flume experiments assessing how changing flow hydraulics modulates bedrock erosion. We show that, under large discharges, changes in flow hydraulics cause spatial variability in particle impact velocity, leading to cyclic step formation. As discharge decreases, both the magnitude and spatial variability of particle impact velocity decreases, causing more uniform erosion, limiting cyclic step development and potentially allowing direct erosion of the waterfall face to become the dominant retreat mechanism. These results suggest climate change and water-resource management can alter the rate and style of waterfall retreat.

Pressurised flow in cracks in embankment dam cores

A major hazard to embankment dams is internal erosion and piping arising from concentrated leaks through cracks in the core due to differential settlement. Previous work (Peirson et al., 2023) quantified the hydraulics of flow through near-surface transverse cracks subject to near-horizontal pressure gradients. This present short note extends the previous work to address pressurised flow through cracks that might occur deeper within the core. Water speeds, hydraulic shear stresses, flows are computed as a function of the applied hydraulic gradient. These results extend previous work addressing the hydraulics of very narrow cracks.

Novel dissolved oxygen distribution model of a full-scale aeration tank for a municipal wastewater treatment plant in a cold climate region

ABSTRACT Aeration is the most energy-intensive process in wastewater treatment plants (WWTP). Seasonal variation in hydraulic flow and load has a significant effect on WWTP's aeration energy efficiency. High flow and temperature variations are common in cold climate regions, and with climate change increasing, extreme weather events will accentuate these situations. The prediction of oxygen mass transfer is crucial for minimizing the energy consumption of the aeration tank. This study presents a computational fluid dynamics model for a turbulent flow regime, simulating the hydraulics and dissolved oxygen (DO) concentration distribution of two phases, water and air bubbles, in a full-scale, as-built activated sludge tank. Model validation error was less than 15%. Different seasonal flows and temperatures were investigated by fixing liquid side oxygen mass transfer coefficient (kL) to 0.7 × 10–5 m/s and initial bubble diameter (dB) to 0.0025 m in the gas phase. The results show that variating hydraulic flow causes noticeable differences in DO distribution and higher flow could be more effective levelling in DO gradients. More even DO distribution could result in using up to a 10% lower DO setpoint value, using 3% less air for the same treatment result, thus lowering aeration energy cost.

Hydrodynamic simulation of coastal reservoir in response to flow control: a numerical study of the Saemangeum reservoir

Coastal reservoirs (CRs) are important water resources worldwide, but environmental problems can arise due to limited material mixing caused by the blocked propagation of tidal waves. The Saemangeum Reservoir is a large brackish reservoir in South Korea; owing to its complex fluctuation characteristics, accurate reproduction of its three-dimensional (3D) circulation and material distribution characteristics remains a challenge. Here, we aimed to improve the reproducibility of the Delft3D model through long-term precision monitoring and analyze problems occurring in CRs. The model reproduced the hydraulic flow and stratification phenomena in CRs. The Richardson number ( R i ) was higher than 100, and the Stratification Index ( SI ) was higher than 1 due to the density difference between the surface and bottom layers. The stratification strength of the Saemangeum Reservoir was, therefore, considered high. Moreover, a two-layer circulation occurred due to the strength of the eddy and the horizontal gradient of salinity. When the sluice gate was expanded, the area and number of days where hypoxia occurred decreased. It would also mitigate the retention of materials caused by the eddy and improve circulation. The findings of this study can be used as foundational data for solving and managing hydraulic problems within CRs.

Effectiveness and impact factors of passive convergence-permeable reactive barrier (PC-PRB): Insights from tracer simulation study

Passive convergence-permeable reactive barrier (PC-PRB) represents a green and sustainable technology for in-situ remediation of contaminated groundwater. A laboratory-scale PC-PRB tracer simulation system was established to quantify its contaminant plume capture performance using image analysis method. Results indicate that PC-PRB captures the plume 65% wider than C-PRB, which means that fewer PRB sizes and materials volume would be necessary to treat an equivalent contaminated plume. This improvement is due to a significant drawdown within the PC-PRB's passive well, known as the passive hydraulic decompression-convergent flow effect. We further evaluated the effects of water pipe length, hydraulic gradient, and media particle size on PC-PRB's plume capture performance. Results indicate that an increased water pipe length enhances the PC-PRB's plume capture capacity due to greater well drawdown. PC-PRB not only captures the plume but also acts as a hydraulic barrier. The retardation effect of PC-PRB on plume migration increases with water pipe length. Conversely, both hydraulic gradient and media particle size impact the plume capture capacity of PC-PRB by modifying groundwater flow velocity and pollutant dispersion. An increase in either hydraulic gradient or media particle size decreases the plume capture performance of PC-PRB. Therefore, PC-PRB technology may be more effective in contaminated sites characterized by low hydraulic gradients and permeability. Overall, PC-PRB demonstrates significant effectiveness in enhancing plume capture performance, which can notably reduce remediation costs and environmental footprint, broadening its application scope.

Depositional and diagenetic heterogeneities in sequence stratigraphic framework of a mixed carbonate-siliciclastic reservoir: A case study from Oligocene–Miocene Asmari Formation in the Persian Gulf

Mixed siliciclastic–carbonate reservoirs, such as the Asmari Formation in the Zagros Basin, present significant heterogeneities that influence hydrocarbon exploration and production. This study examines the depositional and diagenetic heterogeneities of the Asmari Formation in the northwest Persian Gulf through a multi-methodological approach, including petrographic analysis, petrophysical measurements, core CT-scanning, X-ray diffraction, and sieve analysis. The primary goal is to identify the origins, scales, and predictability of these heterogeneities within a sequence stratigraphic framework to enhance reservoir characterization. Facies analysis reveals depositional environments ranging from sabkha to shoreface, peritidal, lagoonal, and shoal settings, with carbonate sedimentation interrupted by clastic influxes associated with sea-level fluctuations. Diagenetic processes, including dolomitization, dissolution, cementation, and fracturing, were identified through petrographic analysis, highlighting their effects on reservoir quality. To quantify these heterogeneities and delineate reservoir flow units, methods such as Winland classification, hydraulic flow unit (HFU) analysis, and Lorenz zonation were applied. Results show that depositional heterogeneities, predominantly driven by sea-level changes, range from small to large scales and can be predicted within a sequence stratigraphic context. Diagenetic modifications substantially affect porosity and permeability, with dolomitization improving reservoir potential, while compaction and cementation tend to reduce it. Fracturing, particularly in the lower Asmari carbonates, enhances permeability. The study concludes that accurately recognizing and modeling reservoir heterogeneities in three dimensions can significantly improve exploration and development strategies in the Persian Gulf. A better understanding of the spatial distribution of high-quality reservoir zones and impermeable baffle layers will facilitate more precise well placement, optimize hydrocarbon recovery, and mitigate exploration risks.

Study Assesses Effects of Carbon Dioxide on Drilling-Fluid Performance in CCS Wells

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 217711, “CCS Well-Control Impact of CO2 on Drilling-Fluid Performance,” by Jan O. Skogestad, SPE, Blandine Feneuil, SPE, and Elie N’Gouamba, SPE, SINTEF, et al. The paper has not been peer reviewed. _ Drilling carbon-dioxide (CO2) storage wells is a task expected to involve handling an influx of CO2 into the drilling fluid. In the study described in the complete paper, experimental characterization of density, rheology, phase envelope, hydrate formation, and drilling-fluid stability are performed on drilling fluids mixed with CO2 for relevant pressures and temperatures. Based on these experiments and verified thermodynamic model descriptions, local models for properties of drilling-fluid/CO2 mixtures were developed and integrated into an existing drilling software suite. Requirements for Enhanced Well-Control Software Well-control-evaluation software based on sophisticated and verified models of the drilling-fluid/gas interaction in the wellbore plays an important role in planning drilling operations. The software also can be used to evaluate the strategy for circulating out a kick and regaining control of the well. When drilling infill wells into CO2 storage sites, this software must be able to process kicks originating from both CO2 and natural gas influx. To achieve this ability, knowledge gaps related to the interaction of CO2 and drilling fluid must be closed. Hydraulic-flow models need to be enhanced with local models that capture the unique properties of CO2 and how it affects drilling-fluid performance. Starting from carefully devised experimental campaigns, the authors developed local models for drilling-fluid/CO2 interaction that were integrated into an existing hydraulic flow model. A well-control-evaluation product for use during planning and execution of infill drilling operations into CO2 storage reservoirs may then be built using the upgraded models. Experimental methods, equipment, and setup are detailed in the complete paper. Experimental Results Bubblepoints. Bubblepoint experiments in the base oil have been performed with CO2 weight content from 4 to 50% of the total weight of the mixture and at room temperature and 50 and 100°C. All measurements have been repeated at least once. At room temperature, CO2 can be dissolved in oil at mass fractions of up to approximately 50%. The bubblepoint increases when the temperature increases (i.e., the solubility decreases). As with base oil, the solubility of oil-based drilling fluid (OBDF) decreases with temperature. The bubblepoint at room temperature with 25% of CO2 by weight of the mixture is approximately 60 bar, roughly the bubblepoint of pure CO2. Therefore, the maximal solubility of CO2 in OBDF is probably below 25%. To compare the measured solubility in base oil and in OBDF, the CO2 content relative to the base oil has been calculated using the OBDF composition provided by the manufacturer.

The impact of effective fractured rock mass properties on development of flow channeling in enhanced geothermal systems

Controlling the distribution of working fluid in an Enhanced Geothermal System (EGS) is crucial to prevent early thermal breakthrough and sustain the initial heat drainage area. Over time, working fluid flow may localize to a small area if fracture permeability increases non-uniformly, and efforts are not made to control the flow distribution. This scenario can potentially lead to mechanical reopening of hydraulic fractures, flow channeling, and thermal short-circuiting. However, current models neglect the nonlinear and inelastic deformation of fractured rock masses on EGS coupled thermo-mechanical response. The objective of this work is to estimate and predict the likelihood of thermal short-circuiting by flow-channeling in an EGS reservoir composed of rock and compliant natural fractures. We utilize three dimensional numerical solutions with reservoir properties based on effective medium theory of fractured rocks to achieve this objective. The results show that presence of natural fractures considerably changes the EGS response to thermal destressing, compared to linear poroelastic models. Flow channeling and short-circuiting, resulting in early thermal breakthrough, are more likely to occur in sparsely fractured reservoirs with stiff and strong natural fractures. Conversely, short-circuiting is unlikely in densely fractured reservoirs where thermal strains are absorbed by natural fracture opening and shear sliding rather than by rock matrix contraction. Estimation of natural fracture density is crucial in long-term forecasting and prediction of EGS power output. Accurate fracture characterization could decisively impact the fate of a project.

Influence of outlet keys slope on downstream bed topography in trapezoidal piano key weirs: An experimental investigation

Assessing scour depth downstream of piano key weirs (PKWs) is crucial for maintaining their structural integrity. The slope of the outlet keys significantly influences flow velocity and the associated risk of downstream scouring. This study experimentally investigates the impact of various factors on scour downstream of trapezoidal PKWs, specifically focusing on weir outlet keys slope (So), particle Froude number, sediment size, bed levels, and relative drop height. The research identifies three distinct stages of scouring. Notably, changes in So significantly affect the hydraulic flow over both the inlet and outlet keys. Reducing So by 57 % led to increases of approximately 32 %, 34 %, 49 %, and 54 % in relative maximum scour depth, distance from the weir, length, and volume of the scour hole, respectively, while relative weir toe scour decreased by about 31 %. Additionally, a decrease in So shifted the locations of the maximum scour depth and sediment ridge downstream, enhancing the symmetry of the scour hole. Increasing the particle Froude number and relative drop height, along with decreasing tailwater depth and sediment size, further intensified the scour hole and sediment ridge characteristics. This study provides critical insights for mitigating downstream scouring in PKWs through a comprehensive analysis of varying So. The proposed optimal value for So, along with newly developed design equations, offers practical guidance for engineers and water resource managers in enhancing the stability of hydraulic structures.

Influence of axial distance between impeller and diffuser on the hydraulic performance and flow loss characteristics of bulb tubular pump

Abstract Bulb tubular pumps used in regional water transfer projects consume substantial power. Optimizing the geometric parameters of tubular pumps is crucial for enhancing efficiency and minimizing hydraulic losses. ANSYS CFX is used to investigate the axial distance between the impeller and the diffuser on the hydraulic performance and flow loss characteristics of the rear-bulb tubular pump, and the numerical simulation results are compared with the experimental data. Then, the entropy production theory is introduced to analyze flow losses. As the axial distance increases, the diffuser’s rectification effect on the flow at the impeller outlet deteriorates, leading to increased flow losses and decreased head and efficiency of the device. Flow losses in the bulb tubular pump are ranked from largest to smallest as follows: impeller, outflow channel, diffuser, inlet channel. The impeller exhibits the highest entropy production ratio, reaching 61.05% at an axial distance of 25 mm. By elucidating the energy loss distribution of each component under varying axial distances, this paper offers insights for the hydraulic optimization design of bulb tubular pumps.

An improved hydraulic method for calculating ecological flow considering the changes of rainfall and temperature within a year

Ecological flow (Hereinafter referred to as EF) is vital for sustaining the health of aquatic ecosystems, whereas fluctuations in rainfall and temperature markedly influence the water needs of riverine aquatic organisms. However, traditional hydrological methods for calculating EF provide a single, fixed EF value throughout the year or for specific periods (such as the flood season or non-flood season), neglecting the dynamic effects of these environmental variables on flow requirements. Building on regression analyses of rainfall and temperature, this study proposes an improved hydraulic method (Hereinafter referred to as IHM) that integrates both rainfall and temperature effects. Utilizing the three cascade hydropower plants on the mainstream of the Liuxi River in Guangdong Province, China, as case studies, the proposed method expands upon traditional hydraulic methods by establishing a relationship between river hydraulic parameters and flow, and employing the ecological suitability thresholds of indicator species as constraints to calculate the EF solution sets for the three hydropower plants. By fitting functions to the basin’s rainfall and temperature data, linear interpolation was applied to distribute the EF solution sets across 12 months within a year. The IHM is subsequently compared and validated with the evaluation standards of the traditional method. The results demonstrate that the monthly EFs by the IHM for the three cascaded hydropower plants address the constraints of fixed EFs by traditional hydraulic methods, offering more accurate and context-specific EFs for each month. The monthly EFs by the IHM also typically conform to the Tennant method’s 10 % standard (fair status) and, during certain months, reach the 40 % standard (good status), thereby effectively preserving the stability of the river’s aquatic environment. The IHM provides a robust technical foundation and theoretical framework for the accurate determination of EFs in riverine hydropower plants.

Performance of carbon and nitrogen removal in a system combining an aerobic trickling filter followed by two stages of vertical flow treatment wetland

Treatment wetland has become a reference in wastewater treatment, particularly for the treatment of domestic or agricultural effluent in rural areas. The AZOE process developed by the company SCIRPE is an optimised system of water treatment based on a conventional two-stage treatment wetlands with vertical hydraulic flow. A trickling filter has been added at the head of the system and filtration stages have been partially saturated to promote anoxic conditions. This study presents the monitoring of a complete pilot-scale AZOE system receiving real and continuous effluents. Effluents from two periods of the year are studied: autumn and spring when the organic load is higher. The performance of each treatment unit, as well as the total treatment unit is presented in this study. The main results show that i) the trickling filter consumes about half of the carbon load whatever the season but that nitrification is lower when the incoming organic load is higher ii) the first stage of filtration contributes a lot to denitrification thanks to the anoxic zones iii) the contribution of the second stage is lower but can increase in case of higher incoming load highlighting a safety role of the treatment. The continuous ammonium and nitrate data at the outlet of the first and second stages show a very characteristic dynamic of this system during the feeding period: a well-defined nitrate peak at the outlet of the first stage which is found on the second stage. The lack of carbon is pointed out as the most limiting factor to denitrification on the second stage.

Enhancing permeability estimation methods in Brazilian pre-salt complex carbonate reservoirs

Carbonate pre-salt reservoirs pose formidable challenges for formation evaluation and estimation of petrophysical properties such as rock flow capacity. The high complexity of the pore system and its textural heterogeneity often lead to poor predictions when using conventional formation evaluation methods. This paper discusses and tests the applicability of two approaches to calculate the absolute permeability curves for the carbonate reservoirs of the Barra Velha Formation in the Santos Basin, proposing a fine-tuned workflow for these complex rocks. In developing our workflow, we used data from a case study well, comprising a complete well log suite and two formation tests, and routine core analysis results (RCAL) in core plugs and sidewall cores. Our workflow consists of: (1) reinterpreting the nuclear magnetic resonance (NMR) log in vugular intervals by decomposing the transversal relaxation time spectra; (2) calculating the absolute permeability by the Timur–Coates model and adjusting the coefficients with the RCAL results from representative samples; (3) applying the Flow Zone Indicator (FZI) method for rock typing to optimally define Hydraulic Flow Units (HFU); (4) checking the consistency of HFUs regarding pore geometry and lithological characteristics; (5) evaluating the performance of the models against core data and formation tests. The predicted permeability curves performed well for the NMR and FZI models when compared to the RCAL data from representative samples, with mean absolute errors for the logarithm of permeabilities equal to 0.78 and 0.87, respectively. This represents an improvement of 15% and 5% when compared to the simplistic approach that uses a power law to relate porosity to permeability from RCAL. These curves also reasonably reproduce the results from the formation tests for the top part of the reservoir, where matrix porosity dominates the flow. However, the NMR and FZI permeability curves underestimate the test results at the bottom part of the reservoir, where karstic and fracture features dominate, demonstrating limitations in these permeability estimation methods for this specific scenario. From our observations, we propose several improvements to enhance the current methods for estimating absolute permeability in pre-salt carbonate reservoirs. In the case of the NMR approach, it is essential to consider the effects of mud invasion in vugs for the correct estimation of the proportions of free and irreducible fluids. In the FZI approach, optimization in defining the quantity and limits of hydraulic flow units is important, which shows that four units are sufficient to represent the reservoir interval.

Failure law of hydraulic pipe joints sealing performance under vibration loads

Aviation hydraulic pipe joints are inevitably affected by vibration loads during service. Fatigue relaxation occurs in the pipe joint structure by vibration, and fretting fatigue wear occurs in its sealing interface, leading to a decline in sealing performance. In order to investigate the sealing performance of hydraulic pipe joints affected by vibration load, this paper first analyzes the modal distribution of the sealing system pipeline under different hydraulic pressures and hydraulic fluid flow rates through vibration frequency sweeping experiments. Secondly, the vibration load is applied to the pipe joints for different numbers of cycles, which reveals the microscopic wear behavior of the sealing interfaces under different tightening torques. Finally, by carrying out the leakage measurement experiment under vibration load, the evolution law of the sealing performance of pipe joints under different hydraulic fluid pressures and tightening torques was obtained.

Pengoperasian Pintu Pembilas terhadap Efisiensi Penggelontoran Sedimen: Studi Kasus Bendung Alale

This study discuss about hydraulic physical model tests of Alale weir to ensure hydraulic flow behaviour of design flood, condition on downstream of weir, and sediment flushing. In this study, observation were made on a physical hydraulic model in the laboratory with a scale of 1 : 50. Flushing tests were carried out to determine effectivity of the flushing, condition of sedimentation or scouring that occurred at downstream. Alale Weir has 3 flushing gate on the right side of the weir. Flushing is carried out using discharge Q25yr with a flowing duration of 1 hour. Flushing gate has considered quite effective in flushing sediment from upstream of weir. The sediment carried is almost 50% in all flushing scenarios. 6th flushing scenario (gate 1 and 2 were closed and gate 3 was fully opened) has the highest efficiency, 53.81%.

Investigation on the Dynamic Characteristics of a New High-Pressure Water Hydraulic Flow Control Valve

Investigation on the Dynamic Characteristics of a New High-Pressure Water Hydraulic Flow Control Valve

Sediment Storage and Fluvial Sediment Transport Linkages Across an Experimental Flood Sequence

AbstractRiver channels are maintained by coordination between flow hydraulics, sediment supply, riparian vegetation, and sediment transport. This coordination is challenging to understand in natural flow regimes, where climatic and environmental drivers produce episodic flood and sediment supply events. To better understand the response of channels to flood sequences, we have undertaken laboratory flume experiments on sediment storage and export across a sequence of alternating hydrographs. Our experiments indicate that accumulated sediment storage before floods predicts sediment transport during floods, with sediment storage depletion during floods causing a nonlinear variation of sediment‐transport rates through time. Likewise, sediment storage between floods follows a growth‐to‐saturation pattern, whereby the sediment transport gradually increases toward the sediment feed rate depending on the occupation of available sediment storage zones. To describe these non‐linear variations, we developed a mathematical model which represents sediment transport and storage as a coupled dynamical system. This work highlights the crucial role that within‐channel sediment storage and its history play in determining sediment export in rivers.