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Piano key weirs (PKWs) represent an evolved and novel type of labyrinth weirs, offering a higher discharge coefficient when compared to linear weirs. Recent attention has focused on investigating energy loss and downstream scouring associated with piano key weirs, given their high efficiency and potential for reducing financial and life risks. In this research, a type-C trapezoidal piano key weir with a height of 0.2 m was utilized, incorporating two jumps with radii of 0.15 and 0.21 m at the weir outlet keys. After setting the flow rate and the tailwater, scouring was started, and then after the equilibration time, the pump was turned off after complete drainage, and the bed profile was taken by a laser meter. The findings indicated that the presence of a jump contributes to an increase in maximum scour depth. Furthermore, the presence of a jump causes the maximum scouring depth to occur further away from the weir toe. Increasing the radius of the jumps also results in an augmented maximum scour depth. The length of the maximum scour depth, compared to the weir toe, is approximately 12% greater in weirs with a bigger jump radius than those with a smaller radius. On average, the maximum length of the scour depth about the weir toe is 29.4% and 19.5% longer in weirs with jump radii of 0.21 and 0.15 m, respectively, compared to weirs without jumps. Additionally, the presence of a jump diminishes scouring at the weir toe, with toe scour being approximately 42% less pronounced in weirs with a bigger jump height compared to weirs without jumps. The average scour index in weirs with jump radii of 0.21 and 0.15 m is approximately 2.77% and 0.52% lower, respectively, compared to weirs without jumps. Moreover, an increase in jump radius correlates with a decrease in the discharge coefficient. [ABSTRACT FROM AUTHOR]

Piano Key Weir (PKW) is a non-linear weir with a small foundation footprint that allows large discharges through a narrow channel. The presence of overhangs classifies it into A, B, C, and D. For different PKW types, this study aims to assess the discharge, hydraulic characteristics (flow regimes, water surface profile, and nappes interference), and energy dispersion. This study employs the FLOW-3D software and validated by comparing experimental types A and D PKW with numerical simulations. Experimental and simulation results agreed well, with lower MAPE values for both types. After that, eight simulations for each PKW type were run, with headwater ratios (Ht/P) from 0.13 to 0.85 (Ht: total upstream head above crest, P: PKW height). Regarding discharge performance, type-B was superior to all other PKW types at lower heads (Ht/P ≤0.40) due to longer upstream overhangs. While at higher heads (Ht/P > 0.40), type-A became the highest PKW type. Since PKWs disperse energy more effectively than linear weirs, they acquire new performance as energy dissipators. Type-C had the highest energy dispersion rate, followed by type-A, type-D, and type-B. Finally, an empirical equation was provided to predict energy dispersion rates over PKW types as a function of discharge coefficient. [ABSTRACT FROM AUTHOR]

Surge chambers play a critical role in moderating oscillations in pumped storage power stations after load disturbances. Owing to the high costs, increased risks, and extended construction times associated with conventional surge chambers (CSCs), we proposed a shaft coaxial surge chamber (SCSC) as an alternative, which was otherwise a compact, economical, and construction-friendly structural configuration. The present study aimed to investigate the hydraulic oscillations, stability, and flow characteristics of an SCSC compared to a CSC under disturbance conditions. Physical models of both types of surge chambers were developed and validated. The results indicated that the novel SCSC system could maintain stability before and after disturbances; its hydraulic fluctuations were slightly higher than those of the CSC, particularly under pumping conditions. During the disturbance, the water level fluctuation amplitudes in the SCSC were at least 1.43 and 2.24 times those of the CSC under different working conditions with 10% flow disturbance. As the disturbance frequency increased, the stability of the SCSC approached that of the CSC. Moreover, a new discharge coefficient range of 0.9–1.2 for the SCSC was proposed, increasing the conventional standard values by 1.5 times. In conclusion, the higher discharge coefficient and unstable flow patterns in the connecting pipe are critical mechanisms that influence the hydraulic oscillations of the SCSC. These findings provide valuable theoretical guidance for practical applications. [ABSTRACT FROM AUTHOR]

Droplet size and distribution uniformity of sprinklers significantly affect production safety in the processes of steam temperature and pressure reduction within nuclear power, and other high-temperature, high-pressure industries. In industrial sprays with high flow rates and low pressure drops, reducing droplet size poses additional challenges, making improved spray uniformity essential for enhancing heat transfer. This study designed and produced a set of swirling-straight sprinklers, tested their flow characteristics and liquid distribution, and proposed a highly uniform spray mode involving swirl jet interaction mixing. The discharge coefficient (Cd) changes indicated that enlarging the jet channel area diminishes the amplification effect, suggesting a trade-off in industrial high flow sprinkler design. A detailed evaluation and analysis method of the spray process, which is superior to the use of a single uniformity parameter, is proposed based on Gaussian function peak fitting method. It has been observed that the relationship between the Gaussian fitting parameters and the pressure drop of the sprinkler tends to be linear. This discovery provides a new basis for designing nozzles with low pressure drop, high flow rates, and uniform distribution. The findings contribute to the optimization of spray performance and provide valuable data for computational fluid dynamics model verification. [ABSTRACT FROM AUTHOR]

Electrical energy consumers, such as AC motors, can be supplied by a dual power supply consisting of a DC grid and a supercapacitor (SC) energy storage system. The efficiency of energy flow can vary depending on where the energy storage system is connected to the DC network, due to the resistance associated with transmission. This paper details an analysis of energy loss in SC and DC source dual-supply systems based on mathematical and simulation models. This study considers three variants, where the SC is connected to a DC line and located close to the load, distant from the load, and close to the DC source. For each case, simulation and mathematical models are developed and the simulation results are verified. Through simulations, the influence of the supercapacitor's discharge proportionality coefficients on power supply efficiency is also studied. [ABSTRACT FROM AUTHOR]

An in-depth understanding of leak behavior in water distribution systems is essential for ensuring the long-term reliability and resilience of critical infrastructure. While previous research has extensively explored leak opening behavior under positive pressure conditions, this study aimed to investigate how leaks behave under negative pressures (e.g., caused by transients, fire flows, etc.). To achieve this, a series of experiments in a 110-mm diameter PVC pipe was conducted, examining various types of leaks under negative pressure conditions. Subsequently, modeling studies were conducted to assess the implications of the observed behavior on intrusion flows through longitudinal cracks considering common pipe materials and properties typical for real water distribution networks, i.e., PVC, PE, AC, and steel. The experimental tests showed consistent head-area slopes for leaks under both positive and negative pressures, with smaller discharge coefficients for intrusion compared to those for leakage flows. This finding suggests that the existing knowledge of leak behavior under positive pressures can be applied in negative pressure conditions. Although round holes and circumferential cracks showed negligible and minimal changes in leak area, respectively, the longitudinal cracks displayed large positive head-area slopes, meaning that their leak areas decreased under negative pressures and sometimes closed, limiting intrusion flows. The study further showed that a leakage exponent (N1) different from 0.5 obtained under positive pressure produces inaccurate results when applied to intrusion flows. The results of modelling studies showed that the intrusion flows in rigid pipe materials such as steel and AC have similar or slightly lower intrusion flows than in the fully rigid case. In contrast, more flexible materials, such as PE and PVC, showed a greater reduction in intrusion flows when subjected to negative pressures. [ABSTRACT FROM AUTHOR]

This study used a direct simulation Monte Carlo approach to investigate the effects of facility pressure on micronozzles for the propulsion systems of microspacecraft. The simulations quantitatively evaluated the effect of background pressure on the micronozzle performance in nozzle flows ranging up to a throat Reynolds number of 220. The results showed that the background pressure could reduce total thrust by more than 50% as the inverse of the nozzle pressure ratio increases from 0 to 5.0×10-3. The primary cause identified was the gas depletion created by the collision of the nozzle plume with the background gas, which creates a negative thrust on the wall surface surrounding the nozzle. The trend of the background-gas-pressure effect differed at each Reynolds number. The wall size also affected the thrust in finite background pressure. Furthermore, this study emphasized the critical role of test-facility conditions in accurately predicting the performance of micronozzles and provided the knowledge necessary to properly predict their performance during space operations. [ABSTRACT FROM AUTHOR]

A series of laboratory experiments were carried out to study the hydrodynamics of flow through and over permeable grade-control structures with different dimensions and degrees of permeability. The local erosion downstream of the grade-control structures was measured at different flow regimes, and the effects of geometry and permeability of the grade-control structures were evaluated. Three flow regimes were observed in free-flow conditions, named as the through-flow regime, combined fully through-flow and overflow regime, and the transition between the two regimes. Semiempirical equations were proposed based on the theory of orifices and weirs to estimate the stage-discharge relationships over and through the permeable grade-control structures. The maximum scour depth at the downstream was predicted by implementing dimensional analysis and multivariable regression technique for both partial through flow (i.e., transition regime) and the combination through-flow and overflow regime. A series of numerical simulations was also performed to model the hydraulics of flow through and over grade-control structures. The numerical model was validated with the experimental results, and detailed information such as instantaneous and time-averaged velocity profile, bed shear stress, and turbulent kinetic energy were extracted from the validated numerical model. The numerical results clearly showed that the effect of crest length on jet deflection and formation vortex region at the downstream of structure was significant. The numerical outcomes indicated the existence of three zones in the surface jet above the grade-control structure, named the entrance zone, the upper roller zone, and the upper–lower rollers interaction zone. Numerical results confirmed a direct correlation between the structure's length and the geometry of local scour hole and indicated that by increasing the crest length by three times, the maximum scour depth decreased by approximately 25%. [ABSTRACT FROM AUTHOR]

By decreasing the entrained air flow discharge and improving the hydraulic characteristics of vertical shaft spillways, Marguerite-shaped inlets (MSIs) can mitigate the effects of swirling flow surrounding their inlet. The hydraulic and hydrodynamic characteristics of flow around MSIs under orifice flow regime were numerically investigated, applying different geometrical parameters. This inlet configuration can decrease the strength of swirling flow and increase the flow discharge through the shaft. The finite-volume method and the re-normalisation group k–ε turbulence model were employed to solve the governing equations of motion in a cylindrical coordinate system and a two-phase air–water flow on the water free-surface. Increasing the height and length of the blades of the MSIs was found to increase the area of the barriers against swirling flow, weaken the swirling flow strength, engender a more uniform flow and lower the water free-surface level. Extremely long or high blades, however, resulted in an intense collision of the flow with the spillway and increased the water free-surface level and the swirling flow strength at the MSI. [ABSTRACT FROM AUTHOR]

A novel set of dimensionless numbers for predicting cavitation flow in gas-liquid flow through a throttling orifice is proposed. Multiple sets of cavitation data are obtained from the literature, and eight dimensionless groups are extracted using dimensional analysis. Subsequently, self-similarity among these groups is established, leading to the proposal of new dimensionless correlations (CfW and CfWd). Investigation results indicate that the established correlations between dimensionless groups can predict cavitation flow in orifices under a wide range of hydrodynamic and geometric conditions. The predictive model is validated using different sets of experimental data, improving accuracy (average relative error decreased by more than 57%) and covering more physical conditions compared to previous correlation predictions. Furthermore, dimensionless parameters with significant influence on the cavitation discharge coefficient are identified by the explanatory machine learning technique SHapley Additive exPlanations (SHAP) and sensitivity analysis. Based on these findings, this investigation contributes to a reduction in the number of variables involved in cavitation experiments or simulations. [ABSTRACT FROM AUTHOR]

A spillway comprises several sections, primarily the crest and chute, essential for safe water flow from an upstream reservoir to a downstream river. Incorporating a hydrofoil crest and stepped chute features creates an efficient Hydrofoil-Crested Stepped Spillway (HCSS). The hydraulic features of the 60 HCSS models, which were designed through the National Advisory Committee for Aeronautics (NACA) equation, are assessed through laboratory experiments under a skimming flow regime, where the five hydrofoil formation indexes (t), three numbers of steps (Ns), and four chute angles (θ) are of concern. The findings indicate that an escalation in the ratio of upstream depth (y up) to spillway height (P), correlates with a rise in the discharge coefficient (C d) in HCSSs. Furthermore, augmenting the t effectively boosts the C d value. On average, the C d value of the crest at t = 1 surpasses that at t = 0.2 by 20 %. This increase in t accentuates the curvature of the spillway crest, thereby enhancing the curvature of streamlines and reducing the flow distance therein. The Energy Dissipation Ratio (EDR) of HCSS is influenced by factors such as t (positively correlated), Ns (positively correlated), and θ (negatively correlated). Optimal performance of the HCSS is observed at t = 1, where both the C d and EDR reach their peak values. [ABSTRACT FROM AUTHOR]

Copyright of Larhyss Journal is the property of Biskra University, Research Laboratory in Subterranean & Surface Hydraulics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance of discharge coefficient (Cd) and wall pressure of Venturi meter under various convergent and divergent cone angles have been experimentally investigated. Several models of tubes have been examined, where the tubes have been manufactured with two convergent angles (20° and 40°) and three divergent angles (7°, 11° and 15°). A pipe system along with ten tapping points distributed along the Venturi meter wall has been utilised to measure the static pressure. The examinations have been done for wide ranges of Reynolds number (Re). Results of Cd have been compared with the empirical solutions and they show a good agreement between them with a relative difference less than 3.5%. As Re is increased until Re = 15000, the results of Cd is substantially increased. Results display that the convergent angle has a less impact on Cd and a major influence on pressure drop as compared to divergent angle. Divergent angle has an inversely impact on Cd. The best value of Cd has been obtained when using the tube that has a convergent angle of 7° and divergent angle of 20°. Present results clearly demonstrate the necessity of choosing the required geometric parameters accurately while designing Venturi meter to achieve the optimum performance HIGHLIGHTS: Reduced scale experiments are conducted to analyze and compare the performance of three air supply strategies. Numerical simulation method is verified by experimental data and applied to the analysis of various scenarios. Side air supply is found as the most efficient air distribution form in the isothermal condition and the heating condition. [ABSTRACT FROM AUTHOR]

To cope with the change of inflow runoff caused by climate change, many old reservoirs need to evaluate the change of discharge capacity of spillway after installing retaining wall or other renovation measures, to formulate safe operation and management measures of reservoir. Taking an old reservoir as a study case, the formula of the correction coefficient of weir pier, a unified formula for calculating the discharge capacity of different weir flow type, the classification method of weir flow type were obtained based on theoretical analysis, the relationship between water level and discharge and the flow type of weir flow are observed through physical model tests, and then the relation of the correction coefficient for weir pier and comprehensive discharge coefficient with water head and the change condition of flow type are determined based on the observed data. The research results show that: the discharge capacity of weir flow is significantly different for weir flow and orifice flow, the unified formula is suitable and practical for such case, the relationship between the comprehensive discharge coefficient and the water head is quadratic for weir flow and linear for orifice flow, and the relationship between the coefficient of pier correction and the ratio of water head and pier shape parameters is an approximate linear. These results can be used as a theoretical basis for the assessment of the discharge capacity of the spillway of hydropower station with the addition of retaining wall to the dam roof to cope with climate change. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The efficiency of water distribution at primary, secondary, and tertiary levels in the Indus Basin Irrigation System (IBIS) has historically suffered due to poor design, suboptimal operation, and water scarcity. To address these issues, the system has been designed with ungated irrigation outlets to ensure equitable water allocation at secondary and tertiary levels. This research evaluates the hydraulic performance of three irrigation outlets: adjustable proportional module (APM), adjustable orifice semi-module (AOSM), and open flume (OF) using a physical model study. A distributary channel model with these outlets was constructed at the Centre of Excellence in Water Resources Engineering, where discharge coefficients (Cd) were calibrated and measured under various hydraulic and geometric conditions, including free and submerged flow conditions, and with adjustments to flow depths and outlet settings. The results showed variability in Cd values under free flow and submerged flow conditions with APM and AOSM ranging from 6.07 to 8.20 and 0.56 to 0.74, respectively, and OF between 2.46 and 4.31. Additionally, the behavior of outlet tampering on Cd values was also assessed under three scenarios: tampering with the half wing wall (1st), tampering with the full wing wall (2nd), and lowering the bed level downstream of the outlet (3rd). The increase in Cd values for APM and AOSM was + 10.84% and + 14.49% under 1st scenario, + 17.12% and + 22.36% under 2nd scenario, and + 24.25% and + 26.30% under 3rd scenario, respectively. The results reveal that even minor tampering with outlet structures can lead to significant deviations in performance, highlighting the importance of maintaining stringent control over outlet configurations to ensure equitable and efficient water distribution. There is a critical need for rigorous, site-specific calibration of irrigation outlets to optimize their performance under local conditions and redesigning outlet structures to minimize the impacts of tampering, thereby enhancing the overall sustainability of water use in large-scale irrigation systems. The findings from this study provide essential insights for irrigation engineers and policymakers tasked with upgrading and maintaining irrigation infrastructure. By adopting a more customized approach to outlet design and management, it is possible to significantly improve water use efficiency and achieve more sustainable irrigation practices. [ABSTRACT FROM AUTHOR]

Rim seals at the periphery of cavities can prevent high-temperature gas from ingesting into the disk cavity. The sealing performance of rim seals and ingestion mechanism for the counter-rotating cavity of a 1 + 1/2 counter-rotating turbine are studied by solving the three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations via shear stress transfer (SST) turbulence model. The accuracy of the numerical method is verified by comparing with the experimental data. The sealing effectiveness in cavities and flow field in rim seal clearance of three rim seals are analyzed, and the impact factor of unsteady flow pattern is explored. The results show that, the sealing effectiveness ε c of the disk cavity of LPR lipped rim seal is the highest within the full sealant flow rate Φ 0 range. When the non-dimensional sealant flow rate Φ 0 is 0.034, the sealing effectiveness ε c at the high-pressure rotor (HPR) disk at r/b = 0.96 for LPR lipped rim seal is 10.96% higher than that of the axial seal which is the smallest; the sealing effectiveness ε c on the low-pressure rotor (LPR) disk at r/b = 0.96 is 18.99% higher than that of HPR lipped rim seal. A clockwise Kelvin-Helmholtz (K-H) unstable vortex within the rim seal clearance is formed due to the large radial gradient of circumferential velocity. The existence of unstable vortices significantly changes the flow pattern of ingress and egress, which can block the axial clearance and reduce the amount of gas ingestion by reducing discharge coefficients. Affected by the supersonic flow inside HPR blades, shock waves occurred near the trailing edge of the HPR blades, including inner-extending shock (IES) and outer-extending shock (OES) and the non-axisymmetry of circumferential pressure coefficient C p at the trailing edge significantly increases. The K-H unstable vortex and non-axisymmetric circumferential distribution of the pressure coefficient C p jointly affect on the ingress and egress process. When the radial inward flow of the vortex is downstream of the high and low circumferential pressure, gas ingestion is enhanced and weakened, respectively. [ABSTRACT FROM AUTHOR]

Sharp-crested weirs are commonly used in hydraulic engineering for flow measurement and control. Despite extensive research on sharp-crested weirs, particularly regarding their discharge coefficients, more information is needed via research on their energy dissipation downstream. This study conducted experimental tests to assess the influence of contraction ratio (b/B) of rectangular sharp-crested weirs (RSCWs) on energy dissipation downstream under free flow conditions. Five RSCWs with different b/B equals 6/24, 7/24, 8/24, 9/24, and 10/24 were used. The results showed a consistent decrease in relative energy dissipation (ΔEr) with an increase in the head over the weir. Furthermore, as the discharge per unit width (q) increased, the relative energy dissipation (ΔEr) decreased, indicating more efficient discharge over the weir. A higher b/B further reduces ΔEr, suggesting that wider weirs are more effective in minimizing energy losses. The maximum relative residual energy (E1/E0) and relative energy dissipation (ΔEr) occurred at b/B = 10/24 and 6/24, with values of 0.825 and 0.613, respectively. Additionally, the maximum discharge coefficient (Cd) of RSCWs is found at b/B = 6/24, with an average value of 0.623. The results support the accuracy of the proposed equation with R2 = 0.988, RMSE = 0.0083, and MAPE = 1.43%. [ABSTRACT FROM AUTHOR]

Liquid nitrogen is a widely utilized effective low-temperature cooling medium, also employed in the ATR-GG (Gas Generator cycle Air Turbo rocket) engine to cool high-temperature components. Due to the high-temperature work environment and the ease with which liquid nitrogen evaporates and boils, liquid nitrogen would experience a flash boiling process. In order to study the influence of flash boiling on spray characteristics, experiments and simulations were conducted with two types of hollow-cone nozzles and two types of solid-cone nozzles under subcooled water at normal temperature which is not affect by flash boiling and superheat liquid nitrogen inflow conditions. The research found that flashing already begins inside the nozzle, significantly reducing the discharge coefficient of the solid-cone nozzle. The nitrogen gas-liquid mixture fills the air core of the hollow-cone spray, resulting in a comparatively smaller impact on the discharge coefficient. The liquid nitrogen spray exhibit spray collapse, unable to achieve the spray cone angels as the water spray. The major reason is that during the flashing process, nitrogen vapor expansion enhances the axial velocity, reducing the spray cone angle. The study recommends using hollow-cone nozzles to mitigate the impact of flash boiling on the spray characteristics. [ABSTRACT FROM AUTHOR]

To improve the accuracy of the wind tunnel test, relying on the high-pressure gas source of the China Aerodynamic Research and Development Center, a secondary flow standard facility based on a sonic nozzle array was developed, with a pressure range of (1~6) MPa and a flow range of (0.12~5.55) kg/s. Currently, most facilities use the average temperature measured by the temperature array to represent the upstream temperature of the sonic nozzle array. However, the small flow calibration test results showed that the maximum temperature difference upstream of the standard sonic nozzle array was 1.97 K, and the temperature field upstream of the sonic nozzle array showed non-uniformity, so the above method cannot accurately obtain the upstream temperature. To solve this problem, each nozzle used in the standard sonic nozzle array was accurately measured by temperature sensors. The uncertainty of the facility and the discharge coefficient of the calibrated nozzle between the two methods were compared. The results showed that compared with the discharge coefficient obtained using the temperature sensor array of 0.9902, the accurate measurement of 0.9904 was closer to the National Institute of Metrology, China (NIM) traceable result of 0.9907, and the relative uncertainty of the facility was reduced from 0.124% (k = 2) to 0.120% (k = 2). [ABSTRACT FROM AUTHOR]

This study utilized machine learning models to predict the discharge coefficient for a sharp-crested triangular side orifice (TSO). The chosen models were the Artificial Neural Network (ANN) and Gene Expression Programming (GEP). Development of the models was based on 570 experimental datasets, with 70% allocated for training and the remaining 30% for testing. Five nondimensional parameters were utilized as inputs for the models, including TSO’s crest height to its height (W*=W/H), main channel width to TSO’s base length (L*=B/L), main channel width to TSO’s height (H*=B/H), upstream flow depth to the TSO’s height (Y*=y1/H), and upstream Froude number of the main channel (Fr). While the discharge coefficient (Cd) was defined as the output. Then, the developed models were evaluated by three performance metrics, violin boxplots, and Taylor diagrams to ensure their reliability and accuracy. Furthermore, a sensitivity analysis was conducted to indicate the most effective parameter affecting the Cd value. The findings revealed that both models predicted very well compared to the actual values, with the ANN model emerging as the most reliable predictor. It exhibited the highest determination coefficient (R2), nearing 1, along with the lowest Mean-Square-Error (MSE) and Mean-Absolute-Error (MAE) values, both close to zero. The sensitivity analysis highlighted that the orifice crest height and Froude number significantly impacted the Cd value, contributing to more than 36%. In addition, the predicted discharge coefficient stayed within the range of ± 5.0% of the experimental values. Finally, the developed models demonstrated a high level of equivalence compared to previous studies, especially the ANN model. Therefore, these models are recommended as accurate, robust, and rapid tools to predict the TSO’s discharge coefficient.

Weirs play an important role in controlling and managing water in irrigation canal networks through several functions, such as discharge measurements, water distribution, and lowering the water level. Weirs also play a crucial role in protecting canals from flooding, which might cause the earthen banks to collapse, by eliminating surplus water at the ends of the canals. Over the previous decades, the flow over the traditional sharp-crested weirs was extensively investigated by many researchers; however, the well-escape weirs have not received sufficient attention. These types of weirs were mostly constructed in the form of vertical wells that may be circular or rectangular in shape, and water may flow through the entire perimeter of the weir or part of the perimeter. In the present research, the effect of the well-escape-weir shape on the characteristics of flow over the weir was studied. A set of models were constructed in different shapes, circular and square, and the entire perimeter of the weir or part of the perimeter is working as the weir crest length. The discharge passing over the unit length of the weir crest (q) is investigated and compared for the circular and square weirs of various crest lengths and positions. The results indicated that the discharge capacity of the circular weirs increases by a rate ranging between 7.5% and 15% more than that of the square weirs at the same head. Also, results indicated that the discharge coefficient of the circular weirs increases by a rate ranging between 9.3% and 10.3% more than that of the square weirs. This behavior can be attributed to the interference between the orthogonal water nappes at the corners of the square models. In addition, the flow direction has little effect on the discharge coefficient at small discharges, and this effect becomes more obvious at higher discharges. Additionally, the well-escape weirs of the upstream crest have a slightly higher discharge capacity than those of the downstream crest due to the effect of the approach velocity, which increases the water entrance velocity at the upstream crest. The results of flow patterns around the weir showed that the locations of maximum flow velocities (u, v, w) are mostly near the weir crest and depend entirely on the crest length and position.

With increased length of the crest in a certain width range, the labyrinth weirs increase the discharge capacity. In this study, a laboratory flume was used with a length of 8 m and a width and height of 0.6 m, in which the hydraulic loss of linear/non-linear, labyrinth, triangular, and trapezoidal weirs were investigated. Dimensional analysis using the Buckingham methodology showed that the discharge coefficient (Cd) is a function of parameters such as hydraulic head ratio (Ht/P), weir shape factor (Sf), and hydraulic loss ratio (Hf/P). The results showed that the ATRL weir has a lower discharge coefficient than the ALR by 44% and ATPL a lower discharge coefficient than ALR by 50%. The ATRL weir has a higher hydraulic loss than ALR by 2300% and a higher hydraulic loss than ATPL by 2000%. The TRL weir has a higher hydraulic loss than LR by 4900% and a higher hydraulic loss than TPL by 5700%. The TRL weir has a lower discharge coefficient than LR by 41% and TPL by 43%. The best correlation with the Cubic statistical model was obtained in the TPL weir in terms of discharge coefficient and in the ALR weir in terms of hydraulic loss.

A spillway comprises several sections, primarily the crest and chute, essential for safe water flow from an upstream reservoir to a downstream river. Incorporating a hydrofoil crest and stepped chute features creates an efficient Hydrofoil-Crested Stepped Spillway (HCSS). The hydraulic features of the 60 HCSS models, which were designed through the National Advisory Committee for Aeronautics (NACA) equation, are assessed through laboratory experiments under a skimming flow regime, where the five hydrofoil formation indexes (t), three numbers of steps (Ns), and four chute angles (θ) are of concern. The findings indicate that an escalation in the ratio of upstream depth (yup) to spillway height (P), correlates with a rise in the discharge coefficient (Cd) in HCSSs. Furthermore, augmenting the t effectively boosts the Cd value. On average, the Cd value of the crest at t = 1 surpasses that at t = 0.2 by 20 %. This increase in t accentuates the curvature of the spillway crest, thereby enhancing the curvature of streamlines and reducing the flow distance therein. The Energy Dissipation Ratio (EDR) of HCSS is influenced by factors such as t (positively correlated), Ns (positively correlated), and θ (negatively correlated). Optimal performance of the HCSS is observed at t = 1, where both the Cd and EDR reach their peak values.

The current study examines the flow characteristics under free flow conditions over a crump weir. The impact of the side slopes of the weir on the coefficient of discharge (Cd) is taken into account. Four physical models with crest heights of 0.15 m under free flow circumstances and four upstream side slope (1:3, 1:2.5, 1:2 and 1:1.5) were used to investigate the impact of various variables on discharge coefficient (Cd). Using the dimensional analysis technique, the elements influencing the crump weir's discharge coefficient were determined based on laboratory tests. For the same flow rate, Cd value decrease by decreasing upstream side slope. It notices that a decrease in upstream slope (from 1:3 to 1:2.5) reducing Cd value about (2.61 %), decrease upstream slope from (1:3 to 1:2) reducing Cd value about (4.16 %) and when decrease upstream slope from (1:3 to 1:1.5) reducing Cd value about (5.81 %).

Side weirs are hydraulic structures employed in irrigation and drainage channels as diversion devices or head regulators. The increasing efficiency of the structure of side weirs for constant head has been one of the concerns of researchers in the last decade. The use of different forms of sharp crest, labyrinth, piano key, and increasing the length of the overflow by changing the geometry of the crest have been investigated. In this research, a new type of triangular-shaped side weir has been studied in the laboratory under different hydraulic conditions in sub-critical flow conditions. The results demonstrated that by inclining the crests of the triangular side weir, the amount of vortex created at the entrance of the opening was reduced. So the discharge coefficient and the flow volume over the side weir showed an increase of up to 27% and 48%, respectively, compared to the normal triangular and rectangular side weirs. Also, after analyzing the data, a non-linear equation was presented to estimate the discharge coefficient with the dimensionless parameters of the ratio of the upstream depth to the weir height (y1/p) and the upstream Froud number (Fr1) with an accuracy of ±15% and NRMSE=0.134.

Nowadays, piano key (PK) weir with an expanded crest length are often used to deal with surplus discharge in dams due to unexpected climate change effects, increasing safety. The present study deals with the numerical modelling of a group of PK weirs with auxiliary geometrical parameters to predict the flow over a PK weir using different FLOW-3D turbulence models. The numerical outcomes were compared with the experimental results to check the accuracy of the underlying FLOW-3D models. It was found that the k-𝜀 turbulence model of FLOW-3D estimated the flow over a piano key weir more closely to the experimental results than the RNG (renormalized group) and LES (large eddy simulation) models. Statistical parameters were used to evaluate the simulated results. It was observed that the coefficient of correlation (CC) was close to one and the root mean square error (RMSE) close to zero when numerical outcomes were compared with experimental datasets. The results show that the FLOW-3D software is quite effective in estimating the flow. Therefore, the present study will help to understand the best combination of mesh, models, adaption and convergence processes in simulation and provide an insight into the numerical analysis of flow configuration over PKW by considering one of the best numerical models.

Phase-to-ground discharge of transmission lines due to ice cover is a common issue. To assess the risk of phase-to-ground discharge of overhead lines under complex ice-covering conditions, this study used finite element analysis to model the interaction between ground wire, conductor, and insulator. The study examined how different factors affect the minimum safe distance between the conductor and ground wire, as well as the risk coefficient of phase-to-ground discharge and the risk zone. The finding reveals that as icing thickness increases, conductor bouncing intensifies, reducing the phase-to-ground distance, and placing one half of the line span within the risk zone for the given conditions. For the same length of de-icing, the closer the de-icing region is to the midpoint, the greater is the maximum jump height of the conductor. When the span is extended to 600 m, the risk range covers approximately 70% of the total line length. Under strong winds, conductor lateral displacement increases with wind speed, which leads to a higher risk of discharge. [ABSTRACT FROM AUTHOR]

The present work shows the development of a comprehensive theoretical formulation for its application in the study of the internal flow of pressure-swirl atomizers with helical channels: "screw-conveyer", which are characterized by presenting in their inlet channels, an angle of incidence or helix angle ψ. This angle originates a trigonometric factor ( cos ψ ) that must be considered in the geometrical characteristics parameter of pressure-swirl atomizer ( A h ), which consequently involves other geometric parameters, such as the annular section coefficient (φ), discharge coefficient ( C d ), spray angle ( 2 α ), etc., being relevant in the internal flow study and design of the pressure-swirl atomizers type screw-conveyer. This theoretical formulation integrates an internal ideal flow model (Abramovich theory) with a model that considers the influence of the liquid viscosity (Kliachko theory) and hydraulic resistance of Idelchik. For the validation of this theoretical formulation, numerical simulation was used, considering the commercial software Ansys Fluent 2023 R2 furthermore, hexahedral meshes were generated with the ICEM CFD software 2023, for four cases of helix angle ψ ( 15 ° , 30 ° , 45 ° and 60 ° ), with application of the RNG k- ε turbulence model and VOF multiphase model (volume of fluid) for the location of the liquid-gas interface and spray angle visualization. [ABSTRACT FROM AUTHOR]

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A significant number of dams worldwide are very old and thus require a reassessment of maximum flood discharges due to siltation and climate change effects. The Piano Key Weir (PKW) is a relatively new labyrinth-type weir that has emerged as a viable solution for dam rehabilitation and new projects with space constraints. While various studies have been conducted in the past to investigate the influence of geometrical parameters of PKW, there is a lack of information regarding the effect of non-linear slope profile of keys on the discharge efficiency. In this paper, ogee profiles have been introduced in the outlet keys to study their influence on the discharge coefficient. The experiments were performed at the Hydraulics Laboratory, IIT Roorkee, India, using a flume 15 m long, 0.39 m wide and 0.52 m deep. These experiments involved four PKW models with different slope profiles in the outlet key. The results of the laboratory studies and RANS model simulations indicate that the PKW models with ogee shaped outlet keys are more efficient than the linear shaped counterpart for heads higher than their design head. The maximum increase in discharge coefficient for the PKW models with curvilinear outlet keys was 9%. [ABSTRACT FROM AUTHOR]

A rectangular slit weir is used to measure small flows, namely, those flows less than 5 L/s and contraction ratios (b/B) less than 0.25. In the present study, flow tests were conducted in a laboratory setup with various contraction ratios (b/B) under models A (b/B = 1/12), B (b/B = 1/8), C (b/B = 1/6), D (b/B = 5/24), and E (b/B = 1/4). The dimensional analysis revealed that b/B, the height of the flow on the crest of the weir to the height of the weir crest (h/P), the Reynolds number (Re), and the Weber number (We) are effective parameters for predicting the discharge coefficient of the slit weir. The experimental results indicated that the discharge coefficient is variable for different contraction ratios; the maximum average discharge coefficient was achieved at the lowest b/B (Model A), with a value of 0.72. The minimum average discharge coefficient obtained in Model B equals 0.639. In addition, former prediction equations were compared with the obtained experimental data, and the minimum, average, and maximum errors were calculated. Furthermore, a relationship was established for deriving the discharge coefficient in slit weirs with R2 = 0.9212, RMSE = 0.02244, and MAE = 0.0134 based on the obtained experimental data with four effective parameters, b/B, h/P, Re, and We. [ABSTRACT FROM AUTHOR]

Piano key weirs are a type of non-linear weir that have a higher discharge coefficient than similar linear weirs. These hydraulic structures have a lightweight foundation and a simple structure is designed and installed on dams and drainage channels. Due to the high efficiency of these weirs, the investigation of downstream scour and ways to reduce it has been the focus of engineers in recent years. In the present study, a trapezoidal type C piano key weir, three discharges, and three tailwater depths were used. Two obstacles with heights of 0.02 and 0.04 meters were also used at the end of the weir exit keys. The results showed that the presence of an obstacle reduces scour at the toe of the weir. The amount of reduction in scour at the toe of the weir was greater in the weir with a larger obstacle height than in the weir with a smaller obstacle height, and in both cases was less than in the simple weir. The presence of an obstacle reduces the maximum depth of scour and moves the distance of the maximum depth of scour away from the toe of the weir. In the weir with obstacle heights of 0.02 and 0.04 meters, compared to the weir without an obstacle, the amount of maximum scour depth is approximately 16.4% and 26.9% less, and the distance of the maximum scour depth is approximately 8.7% and 19.1% more than the weir without an obstacle. The scour index in weirs with obstacles is less than in weirs without obstacles, which can reduce the risk of weir overturning. The lowest value of the scour index was observed in the weir with an obstacle height of 0.04 meters, which is approximately 41.2% less than the weir without an obstacle. [ABSTRACT FROM AUTHOR]

Side weirs are hydraulic structures employed in irrigation and drainage channels as diversion devices or head regulators. The increasing efficiency of the structure of side weirs for constant head has been one of the concerns of researchers in the last decade. The use of different forms of sharp crest, labyrinth, piano key, and increasing the length of the overflow by changing the geometry of the crest have been investigated. In this research, a new type of triangular-shaped side weir has been studied in the laboratory under different hydraulic conditions in sub-critical flow conditions. The results demonstrated that by inclining the crests of the triangular side weir, the amount of vortex created at the entrance of the opening was reduced. So the discharge coefficient and the flow volume over the side weir showed an increase of up to 27% and 48%, respectively, compared to the normal triangular and rectangular side weirs. Also, after analyzing the data, a non-linear equation was presented to estimate the discharge coefficient with the dimensionless parameters of the ratio of the upstream depth to the weir height (y1/p) and the upstream Froud number (Fr1) with an accuracy of ±15% and NRMSE=0.134. [ABSTRACT FROM AUTHOR]

Urban pluvial floods can be produced or exacerbated by an insufficient density of inlets or by their poor hydraulic efficiency. Therefore, proper consideration of the hydraulic performance of inlets is essential to guarantee the correct functioning of urban drainage systems during heavy storm events. Recent advances in computational analysis in the field of hydrodynamics modelling allow the use of the well-known concept of dual drainage for design and planning purposes by simulating flow transfers between the surface layer (streets) and underground layers (sewers) through a proper hydraulic characterisation of inlet efficiency. Powerful commercial software packages allow simulations of flow transfer and use different approaches and formulas. Many of these approaches include the possibility of treating a sewer inlet as an orifice. In this context, this paper presents a methodology to obtain orifice discharge coefficients for three inlets previously tested at the hydraulics laboratory of the Technical University of Catalonia. Discharge coefficients of 0.18–0.58 were obtained for Froude numbers of 1.12–4.40, quite far from the usual recommended values. The proposed procedure can also be applied to non-tested grates. [ABSTRACT FROM AUTHOR]