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In this study, we investigate the discharge coefficient prediction of arched labyrinth weirs with a cycle angle of 6 degrees, employing 243 data series. Labyrinth weirs, aside from their economic advantages, exhibit superior flow-passing capabilities compared to linear weirs. Notably, increasing the length of the crest within a specified width enhances discharge efficiency with less upstream height. Machine learning algorithms, namely QNET and SVM, play a pivotal role due to their proficiency in uncovering intricate relationships between independent and dependent parameters, leading to significant time and cost savings. Our results using QNET and SVM indicate that the combination of (Cd, , θ, ) yields optimal accuracy, with QNET achieving (R²=0.9850), (RMSE=0.0259), and (DC=0.9892) in the training phase, and (R²=0.9824), (RMSE=0.0292), and (DC=0.9788) in the test phase. For SVM, the training phase results are (R²=0.9889), (RMSE=0.0189), and (DC=0.9870), and in the test phase (R²=0.9881), (RMSE=0.0199), and (DC=0.9853). Sensitivity analysis shows the significant role of the total water load ratio parameter ( ) in determining the discharge coefficient of arched labyrinth weirs. This research contributes to the understanding of non-linear arched weir discharge predictions and highlights the efficacy of QNET and SVM algorithms in this domain.

A paramount determinant in the selection of irrigation canal overflow configurations resides in their flow conveyance capacity. This overflow capacity is contingent upon the effective length and geometric characteristics of the weir. In the present investigation, the hydraulic performance and discharge coefficient (Cd) of circular-crested weir were scrutinized through the utilization of FLUENT software. Specifically, the study delved into the impact of geometric parameters, namely the radius and height of the crest, on these hydraulic aspects. Following the execution of calibration and validation procedures using FLUENT in conjunction with laboratory-derived data, the outcomes of the simulation revealed that augmenting the radius of the crest led to a corresponding escalation of 144.28% in the maximum pressure exerted on the crest and a 6.84% increase in flow depth. Conversely, the maximum velocity and Cd experienced reductions of 6.84% and 7.82%, respectively. The elevation of the weir height exhibited negligible influence on the maximum pressure magnitude at the crest. Contrastingly, a reduction in weir height constricted the range of pressure variations on the crest, indicating a more limited domain of pressure changes. Elevating the weir height induces a notable augmentation in the maximum flow velocity at the crest by 44.36%, concomitant with a reduction in both the depth and Cd by 52.66% and 68.96%, respectively.

The purpose of this research is to provide a solution to eliminate the vortices formed upstream of the sliding valve. The effect of the threshold with the geometric shapes of semi-cylinder, cylinder, pyramid and rectangular cube in different widths of 5, 7, 10, 15 and 20 cm under the sliding valve was investigated experimentaly. The results of this research showed that the entry of air into the fluid leads to the formation of the vortex phenomenon in the flow profile due to the water absorption of the slide valve from the surface layers. The conservation of angular momentum at the opening of the valve causes the combination of vertical and horizontal components of the velocity near the sliding valve. The results showed that placing the threshold under the horizontal sliding valve increases the horizontal velocity of the flow. Therefore, it turns the vortex with a larger diameter into end-line vortices. Due to the insignificant effect of threshold shape on vortices, its effect was ignored.

This study delves into the impact of downstream obstruction angles on the discharge coefficient (Cd) over ogee weirs within open channel flows, a critical factor for accurate flow rate predictions in hydraulic engineering. Employing a series of detailed laboratory experiments, the influence of various obstruction angles on Cd was scrutinized applying a suite of regression analysis to develop predictive models. The analysis was enriched by considering hydraulic parameters such as flow rate, water level, and weir geometry. Despite the established importance of Cd in hydraulic designs the nuanced effects of downstream obstructions have received limited attention, highlighting a critical research gap. The findings highlight a strong correlation between obstruction angles and Cd, with developed regression models demonstrating notable predictive strength. Remarkably the models exhibited varying levels of accuracy, with the Random Forest regressor achieving an exceptionally low root mean square error (RMSE) of 0.005, indicating superior predictive performance. Conversely, traditional models like Decision tree and XG BOOST reflected higher RMSE values of 0.60, suggesting less predictive accuracy in this context. LASSO, Bayesian Ridge, and OMP regressors stood out with an RMSE of zero, denoting perfect predictions under the study's specific conditions. HIGHLIGHTS The study employed multilinear and polynomial regression techniques to predict variations in the coefficient of discharge for an ogee weir due to downstream obstructions at different angles. This approach provides a quantifiable understanding of how such obstructions impact hydraulic efficiency.; Results highlight the significant impact of obstructions on the discharge efficiency of ogee weirs, emphasizing the need for careful consideration of potential downstream barriers in the design and management of hydraulic structures to optimize performance and reduce flood risks.; The findings offer valuable insights for engineers and practitioners in the field, suggesting that regression models can serve as effective predictive tools for estimating the discharge coefficient under various scenarios, aiding in the design and operation of more efficient hydraulic systems.;

Accurate calculation of flow discharge for sluice gates is essential in irrigation, water supply, and structure safety. The measurement of discharge with the requirement of distinguishing flow regimes is not conducive to application. In this study, a novel approach that considers both free and submerged flow was proposed. The energy–momentum method was employed to derive the coefficient of discharge. Subsequently, the discharge coefficient was determined through the experiment which was performed on the physical model of a vertical sluice gate with a broad-crested weir. Feature engineering, incorporating dimensional analysis, feature construction, and correlation-based selection were performed. The best subset regression method was employed to develop regression equations of the discharge coefficient with the generated features. The derived formula was applied to compute the discharge coefficient in the vertical sluice gate and determine the flow discharge. The accuracy of adopted method was assessed by comparing it with recent studies on submerged flow, and the results demonstrate that the developed approach achieves a high level of accuracy in calculating flow discharge. The coefficient of determination for the calculated flow rate is 0.993, and the root mean square percentage error is 5.04%. HIGHLIGHTS The feature combination with efficient interpretability of free-submerged flow discharge coefficient was proposed.; The computational equation applicable to free-submerged flow regimes based on the EM method was established with high accuracy.; The process of feature selection and calculation is not complicated and has potential for automated calibration.;

AbstractIntroduction: The use of numerical methods is widely used in diagnosing the performance of hydraulic systems and optimizing them. Numerical modeling is less expensive than experimental work. Numerical methods can be used to check the accuracy of the results and compare them. In this thesis, the fluid volume method is used to simulate the free surface flow of water inside the lower discharger of Kani Sib Dam. Since the flow inside the dischargers is turbulent, k-ε, k-ε RNG, k-ω SST, k-ω and also LES turbulence models have been used and compared. Also, the discharge coefficient inside the lower discharger and the aeration flow have been investigated and compared.Methods: To simulate the turbulent flow inside the lower discharger, continuity equations, momentum, energy and equation of state along with equations related to the aforementioned turbulence models have been solved using OpenFoam software. The set of equations of conservation of mass, conservation of momentum and energy for turbulent flow, which are so-called Reynolds averaging equations, are the governing equations of the flow and are used to model the flow by solving them numerically.Findings: The simulation and optimization of the hydraulic parameters of the turbulent flow in the lower dischargers of the Sib Mineral Dam has been completed using OpenFOAM. The results have been made on the parameters of the lower discharger of Sib mineral dam. And the optimization is done using genetic algorithm. In this research, it was found that with the increase of the hydraulic diameter, the discharge coefficient increases. Also, with the increase of the hydraulic diameter, the core of the water fluid jet inside the discharger undergoes a strong fluctuation, which can increase the shear stress. An excessive increase in shear stress can cause corrosion of the discharge walls. On the other hand, with a further decrease in shear stress, deposition inside the lower discharger increases. At the same time, with the increase in the length of the lower discharger, the discharge coefficient decreases. The optimal selection of the length of the lower drain depends on the height behind the dam. As the opening rate increases, the discharge coefficient also increases and the k- ε turbulence model gives more acceptable results to estimate the results. Finally, for each aeration flow rate, a set of optimal values for the discharge coefficient and the opening rate has been obtained.

One of the most important hydraulic structures which are used to divert flow is lateral intake. It can be performed by different methods, such as channels, pipes, orifices and etc. This study investigates the effects of various geometric and hydraulic parameters on bottom intake which is widely used as seawater intake for desalination plants. Observation shows that the flow velocity is higher in the square shape than in the circular shape in the front of velocity cap, while it is more at the both sides of the velocity cap in circle type. The correlation of various factors on the discharge coefficient was analyzed based on 180 physical tests by using Python code. Results show that the discharge capacity of the circle shape intake velocity cap is about 2% to 4% higher than that of the square shape intake cap. In addition, discharge coefficient of intake is affected by the approach flow Froude number and area of intake, while the height of the velocity cap has less effect on discharge trough intake. Furthermore, numerical investigation invests on flow pattern around velocity caps. Observation show that separation zone located at the back side is bigger in the square shape than in the circular shape.

【Objective】 Discharge coefficient is a coefficient describing the discharge of non-point source pollution to water bodies. It is affected by many biotic and abiotic factors. In this paper, we analyze its variation in typical drylands in river network areas in a plain. 【Method】 The studied area is located at the Chongming Island, Shanghai. A hydrology-water quality collaborative monitoring system was constructed in the island, which can accurately calculate the discharge coefficient of non-point source pollution, identify its temporal variation, and analyze the underlying influencing factors. 【Result】 ① Daily discharge coefficient of total nitrogen (TN) and total phosphorus (TP) is 2.2-9 843.9 and 0.08-667.0 g/(hm2·d), respectively; monthly discharge coefficients of TN and TP is 0.02-17.2 and 0.001-1.04 kg/(hm2·m) respectively. ② The total nitrogen discharge coefficient during precipitation runoff period is significantly positively correlated with duration of the precipitation, while the TP discharge coefficient is significantly positively correlated with the total precipitation, average precipitation intensity, and maximum hourly precipitation intensity. ③ Following fertilization, the daily discharge coefficient of TN increases rapidly, while the daily discharge coefficient of TP remains almost unchanged. ④ At different time scales, there is no notable correlation between TN discharge coefficient and surface runoff, whereas the TP discharge coefficient exhibits a significant positive correlation with surface runoff. 【Conclusion】 The discharge coefficients of nitrogen and phosphorus vary with time scales, with significant differences observed between daily and monthly discharge coefficients. TN discharge coefficient is primarily influenced by fertilization, whereas TP discharge coefficient is more sensitive to precipitation and surface runoff.

Flow measurements in pipes and open channels are critical for successful water resource management as the economic value of water has increased. Orifice meters are typically used as flow-measuring devices in pipes because they are cheap and simple compared to other devices. Also, orifices are used as energy dissipation methods in water hammer protection devices and hydroelectric power tunnels. Although traditional circular orifice meters have been extensively studied, many points need to be studied. So, experimental and numerical research is carried out to study the effect of orifice geometry on energy loss and the discharge coefficient. The experimental tests are carried out using two different types of orifice plates: circular and triangular, for each one the cross-sectional area is changed four times. The orifice is installed on a 10 cm diameter transparent pipe. The flow rate is changed ten times for each orifice ranging from 13.8 to 49.2 m3/hr. A general correlation equation for the coefficient of discharge is deduced. It was found that the triangular orifice shapes are better than the circular orifice shapes in terms of performance, with reduced head loss and a larger discharge coefficient. By using computational fluid dynamics techniques, the flow behavior through the orifice is analyzed by ANSYS Fluent software. The numerical results confirmed the experimental ones where the pressure head loss for the triangular orifice is lower than the circular orifice and vena contracta is located at a distance equal to half the pipe diameter downstream of the orifice plate. [ABSTRACT FROM AUTHOR]

In order to solve the problem that the wind field disturbs the trajectory of falling seeds and causes the seeds to be unable to be arranged in equidistant rows when the UAV is spreading rice, a shot seeding device that can sow five rows of pelleted rice seeds at the same time was designed. The unit is centered on an external grooved wheel seed metering device and a seed acceleration unit for row seeding and hole sowing. The airflow simulation of the rotor wind field of the UAV was carried out by simulation software to explore the changes in the wind field of the UAV during operation. The position where the wind field disturbance is minimized is chosen for the seed guide tube arrangement. The position with the least wind field disturbance is chosen to arrange the seed guide tube and combine it with a seed acceleration device to reduce the influence of the UAV wind field airflow on the direction of seed movement. The operational effectiveness of the seeding device with and without wind was verified by an indoor test and an outdoor flight seeding test, respectively. Simulation results show that: when the mouth of the seed guide pipe is 0.9 m away from the paddle, the wind field has the smallest influence on the sowing results. The results of the bench test show that: when the rotational speed is 30-45 r/min, the coefficient of variation of the discharge rate of each row (CVR) and total seed discharge rate stability (CVT) are less than 1.98% and 0.84%, and the seed breakage rate is less than 0.95%, which all conform to the UA V fly sowing industry standards. The outdoor mud box test shows that: when the baffle angle changes by 26%, 58%, and 71%, each slot wheel hole can store 5-10, 3-5 and 1-3 seeds respectively, and the UAV operates at a speed of 2 m/s-3 m/s, the pass rate of hybrid rice is greater than 86%, which meets the agronomic requirements of rice sowing operation. [ABSTRACT FROM AUTHOR]

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The piano key weir (PKW) is an evolution with more hydraulic efficiency, compared to labyrinth weir. The studies on this type of weir have shown a significant increase in its discharge efficiency, especially at low heads. In this study, discharge coefficient of various shapes of piano key weir (i.e. rectangular, trapezoidal, and triangular) is investigated experimentally. Also, the aeration process of the studied weirs is described. According to the results, it was found that the discharge coefficient of the triangular PKW is about 28.2% more than the discharge coefficient of the rectangular PKW, and the discharge coefficient of the trapezoidal PKW is about 12.9% more than the discharge coefficient of the rectangular PKW. Also, the discharge capacity of the rectangular, triangular, and trapezoidal PKWs are 3.8, 3.96, and 3.96 times the sharp crest weir, respectively. The equations introduced for the discharge coefficient show good agreement (with R2 from 0.968 to 0.988 and average percentage error from 0.82 to 2.6%) between the actual and calculated values. [ABSTRACT FROM AUTHOR]

The complex field of free flow around a cylindrical weir – gate with and without a flow extender is investigated experimentally. The effects of the gap between the channel bed and the cylinder on the discharge characteristics of the cylindrical weir-gate are studied. It is observed that the ratio of the gate to weir discharge increased non-linearly with the normalized opening height. Four triangular downstream extensions of the cylinder oriented at, θ = 0, 10, 20, and 30 degrees were tested, and the minimum underflow to overflow discharge ratio was observed for θ = 10°. The highest improvement in discharge coefficients was 16% ± 6% for extender orientation angles of θ = 10°. The effects of opening height and extender angle on flow streamlines, pressure distribution, vortex strength, turbulent kinetic energy, and Reynolds stresses were investigated. A region of negative pressure was observed near the weir crest and the peak negative pressure increased with the opening height. The size and orientation of downstream wakes were measured, and it was found that the length of wakes varies from 0.30 to 1.06 times the diameter of the cylinder. The experiments showed that for a constant normalized opening height, the vortex center point formed further downstream as the upstream water head increased. [ABSTRACT FROM AUTHOR]

A spillway is a significant structure that releases the exceeded water during extreme flood events. It is considered as a safety valve during dams operating. Spillway location at dam body is one of the most important requirements of dam design. Different locations may influence the flow patterns which lead to change in the hydraulic performance of the spillway. In this paper, a numerical model was presented utilizing the Ansys fluent software using the realizable k-ɛ turbulence model to investigate the flow patterns of Mandali Dam's spillway at different locations. The interaction between air and water phases was simulated by using volume of fluid (VOF) model. Moreover, cavitation damage was studied for different flow discharges values. the validation of the numerical model was executed in compression with the measurement of the physical model. A discharge of 1800 m3/s was utilized for validation, while five different discharges; 1800, 1300, 1040, 440, and 67 m3/s were employed to investigate the hydraulic properties. The results show an agreement between numerical model and the physical model. According to the hydraulic properties, the spillway location at the center of the dam is better than its location at the edge of the dam. The discharge coefficient value in scenario one was found to be closer to the physical model value compared to the second scenario. At discharge 1800 and 1300, the discharge coefficient was 2.02 and 1.72, while in scenario two it was 1.46 and 1.21 in comparison with physical model which was 2.06 and 1.99. For cavitation investigations, the numerical model shows that the spillway is safe with no cavitation effects for the whole applied discharge values. [ABSTRACT FROM AUTHOR]

Current research presents a comprehensive numerical study on the performance of riverbed intake systems equipped with non-circular cross section racks. Three types of bottom racks, such as rhombus bars, rounded-edge rectangle bars, and circular bars, were numerically modeled using Flow3D software with different geometric and hydraulic parameter, all in super critical approaching flow in clear water condition. Subsequently, changes in diverted discharge ratio (DDR) of bottom racks and factors affecting its intensity and manner of changes, were studied using model results. The study reveals that the RNG k-ε turbulence model accurately represents the flow field around the bottom racks. The results indicated that the DDR changes are directly related to rack length changes but is inversely related to the rack slope and upstream flow discharge. Also, rhombus bars outperform circular and rounded bars, with 23.34% and 35.92% higher flow diversion, respectively, attributed to the formation of more negative pressures between bars. The main focus of the present study was on accurate and complete estimation of the diverted discharge coefficient (Cd) for racks with different bar shapes—especially non-circular bars using the results of the constructed numerical model. Proposed relations for the diverted discharge coefficient (DDC), especially for non-circular bars, were rigorously validated and showed high accuracy in predicting DDC under diverse hydraulic and geometric conditions. [ABSTRACT FROM AUTHOR]

In the present study, a passive flow device is considered for drag reduction purposes through implementation in a transonic high-power rocket. The high-power rocket serves as a reference platform that, apart from the operating conditions, enforces several constraints in terms of available volume and placement locations. A step-by-step methodology is suggested, where the unit is initially broken down into an inlet and an outlet component. The flow field is investigated by means of computational modeling (CFD), where the Reynolds-averaged Navier–Stokes equations are solved coupled with turbulence models that vary depending on the design phase and the individual component. In the first design phase, the best alternative configuration is selected for each component by comparing mass flow rates and discharge coefficients. In the second design phase, each component is analyzed in greater detail based on the first phase results. Indicatively, the protruding inlet diffuser-type channel is converted into a protruding inlet nozzle-type channel to avoid choked flow phenomena, and a nozzle geometry is selected as the outlet amongst the other considered scenarios. The two components are eventually integrated into a common base bleed unit and a final assessment is made. The computational results are used to predict the performance and trajectory of the rocket through a well-established trajectory software. The overall methodology is validated against full-scale test flight data. The results show that the base bleed unit developed in the framework of this study yields a drag reduction of approximately 15% at transonic speeds without impacting the rocket mass and stability. [ABSTRACT FROM AUTHOR]

This document discusses a research paper on the discharge coefficient of Type-A piano key weirs. The discussers appreciate the authors' efforts but suggest further analysis for one equation in the original paper. They conducted simulations and analysis, providing graphs and tables to support their findings. The document also includes a sensitivity analysis of input parameters affecting the discharge coefficient, showing the varying effects of different parameters. The study provides insights into estimating the discharge coefficient and was supported by funding from the Water Resources Department of Jiangxi Province and the Natural Science Foundation of Jiangxi Province in China. [Extracted from the article]

Swirling flow at vertical shaft spillways results in flow fluctuations, reduces hydraulic system efficiency, and causes structural damage. Optimizing the shape of the inlet is a practical means to decrease the swirling flow strength. In the present study a comprehensive experimental investigation was performed to examine the effects of a new type of inlet over vertical shaft spillways, namely the circular piano-key (CPK) inlet, for free, orifice and full-pipe or black water flow regimes. Head-discharge relationships, threshold and critical submergence depths and the effects of different geometrical parameters of the CPK inlets on the spillway flow discharge coefficient were assessed. Results reveal that increases in the height of the inlet and outlet keys increase the released capacity of the shaft spillway. Given its increased total crest length and the effects of the radially placed walls of a CPK against the swirling flow, angles of the inlet and outlet keys of the CPK are found to significantly affect the spillway flow discharge. The effect of inlet and outlet overhangs on the efficiency of CPK inlets is not noteworthy, being negligible. Considering the destructive effects of swirling flow, the CPK inlets significantly decrease the range of submergence for an unfavourable swirling flow regime condition, increasing the threshold submergence depth and decreasing the critical submergence depth. The flow discharge through the CPK inlets is higher than those of the other circular-type spillways. The present modified CPK inlets more effectively divert water, serving as an economical alternative to the conventional circular spillways. [ABSTRACT FROM AUTHOR]

Both the flow and spray characteristics of a gas–liquid pintle injector element under the backpressure environment were investigated experimentally and numerically. The cold atomization tests were conducted with the backpressure range from 0.50 to 1.54 MPa. Both the interaction process between gas film and liquid jets and the detail distribution of the spray were obtained by the verified volume of fluid to discrete phase model. Results showed that there is a local high-pressure zone at the root of the liquid jets resulted by the collision of gas film and liquid jet. A semi-empirical model for predicting the discharge coefficient of the orifices is proposed considering the effect of local high-pressure zones based on the experiments. It was found that the discharge coefficient is mainly affected by the local momentum ratio (LMR) and ambient pressure. The discharge coefficient increases with the increase in LMR and ambient pressure. Before the primary breakup occurs, the liquid jets deform from rectangle jets to bow-shaped liquid films under the effect of the gas film. Then, both the gas and liquid mix in the range included by the gas passed by the windward surface and side of liquid jets. The droplet size is larger at the edges of the spray and the Sauter mean diameter (SMD) is beyond 100 μm. On the contrary, it is relatively small and uniform at the spray central, and the corresponding SMD is about 50 μm. [ABSTRACT FROM AUTHOR]

This paper presents a holistic approach to address the challenges associated with deploying laboratory-derived hydraulic models in real operational conditions within Urban Water Systems (UWS). The underlying methods and tools are tested and validated using real-world data from the conveyance system serving the city of Athens, Greece. Initially, a novel data repair mechanism is developed, to rectify inconsistencies in time series. Subsequently, algorithmic techniques are applied to identify the most suitable datasets for calibration purposes. Furthermore, a grey-box procedure is developed to adjust key hydraulic modelling parameters, following a modular calibration procedure and aligning them with the specific characteristics of the UWS under study. The findings of this study provide valuable insights for effectively adapting and implementing laboratory-derived hydraulic models in real-world UWS scenarios, enabling better decision-making and management strategies for complex hydro-systems under challenging operational conditions. [ABSTRACT FROM AUTHOR]

This paper presents an experimental campaign conducted next to the Condoroma dam, in Perú, at 4075 m a.s.l. The tests carried out in this paper were conducted in a 21 m long channel located at the toe of Condoroma dam. The setup consisted of a series of standard profile spillways with a vertical upstream face of up to five different dimensionless heights (P/Hd) ranging from 0.5 to 2. The experimental results indicated that, the P/Hd ratio influences the discharge coefficients in Condoroma, and P/Hd ≥ 1 values are recommended for the design of the spillway profile. In addition, for all the P/Hd ratios studied, the discharge coefficients adjusted to the Condoroma altitude were lower than those reported by classical formulations used in conventional spillway designs. Finally, a generalized equation is proposed to estimate the discharge coefficient for standard spillways located in dams at similar elevations above sea level. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the viability of employing ammonia (R717), a naturally existing refrigerant, within a transcritical cascade refrigeration configuration. The low temperature (LT) cycle of the cascade transcritical refrigeration system is driven by carbon dioxide, while the high temperature (HT) cycle is propelled by ammonia. Furthermore, the proposed transcritical cascade cycle has the potential to be utilized not just for cooling purposes but also for heat generation. The thermal performance of the cascade cycle has been evaluated for several combinations of design and operational parameters, leading to the identification of optimal presentation metrics like COPheating, COPcooling, COPsys, and the mass flow ratio of R717/R744. The lowtemperature cycle is dependent on two specific temperatures that are considered design parameters: the temperature of the evaporator and the temperature at which the gas cooler outlet is set. The analysis demonstrates that the coefficient of performance (COP) for cooling remains relatively constant, with values of approximately 0.601 at 32° and 0.680 at 40°. This suggests that variations in the evaporator temperature do not significantly impact the COP of the system. The impact of increasing discharge pressure on the system's coefficient of performance (COP), heating, and cooling becomes apparent. An inverse correlation exists between the discharge pressure and the coefficient of performance (COP) of the system. Specifically, the COP is measured at 0.791 when the discharge pressure is 8000 kPa, and it decreases to 0.620 when the discharge pressure increases to 12000kPa. [ABSTRACT FROM AUTHOR]

Modern high-pressure injection systems for heavy-duty applications are prone to cavitation, which may have a detrimental effect on the system integrity. The present study aims to develop reliable correlations for Lagrangian engineering simulations to predict the onset of cavitation. Using the extensive data generated from the high-fidelity Eulerian volume-of-fluid (VOF) simulations of a single-hole injector for a wide range of operating conditions, a proper set of discharge (C d) and contraction (C a) coefficients are determined. In particular, four significant factors characterizing nozzle geometry are considered: the K factor, inlet curvature radius, nozzle exit radius, and channel length, as well as ambient and injection pressures. The results showed that a larger K factor and inlet curvature radius yielded higher C d and C a values, while the exit radius and channel length had a less significant impact on the cavitation dynamics. The smaller pressure difference between the nozzle inlet and exit mitigated the cavitation formation. These trends were well described using the mathematical regression model. Furthermore, two other correlation models based on the regression learner and artificial neural network methods were also developed. Of these three models, the mathematical regression model yielded the best agreement with an external validation dataset. [ABSTRACT FROM AUTHOR]

A paramount determinant in the selection of irrigation canal overflow configurations resides in their flow conveyance capacity. This overflow capacity is contingent upon the effective length and geometric characteristics of the weir. In the present investigation, the hydraulic performance and discharge coefficient (Cd) of circular-crested weir were scrutinized through the utilization of FLUENT software. Specifically, the study delved into the impact of geometric parameters, namely the radius and height of the crest, on these hydraulic aspects. Following the execution of calibration and validation procedures using FLUENT in conjunction with laboratory-derived data, the outcomes of the simulation revealed that augmenting the radius of the crest led to a corresponding escalation of 144.28% in the maximum pressure exerted on the crest and a 6.84% increase in flow depth. Conversely, the maximum velocity and Cd experienced reductions of 6.84% and 7.82%, respectively. The elevation of the weir height exhibited negligible influence on the maximum pressure magnitude at the crest. Contrastingly, a reduction in weir height constricted the range of pressure variations on the crest, indicating a more limited domain of pressure changes. Elevating the weir height induces a notable augmentation in the maximum flow velocity at the crest by 44.36%, concomitant with a reduction in both the depth and Cd by 52.66% and 68.96%, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this research is to provide a solution to eliminate the vortices formed upstream of the sliding valve. The effect of the threshold with the geometric shapes of semicylinder, cylinder, pyramid and rectangular cube in different widths of 5, 7, 10, 15 and 20 cm under the sliding valve was investigated experimentally. The results of this research showed that the entry of air into the fluid leads to the formation of the vortex phenomenon in the flow profile due to the water absorption of the slide valve from the surface layers. The conservation of angular momentum at the opening of the valve causes the combination of vertical and horizontal components of the velocity near the sliding valve. The results showed that placing the threshold under the horizontal sliding valve increases the horizontal velocity of the flow. Therefore, it turns the vortex with a larger diameter into end-line vortices. Due to the insignificant effect of threshold shape on vortices, its effect was ignored. [ABSTRACT FROM AUTHOR]

In this study, we investigate the discharge coefficient prediction of arched labyrinth weirs with a cycle angle of 6 degrees, employing 243 data series. Labyrinth weirs, aside from their economic advantages, exhibit superior flow-passing capabilities compared to linear weirs. Notably, increasing the length of the crest within a specified width enhances discharge efficiency with less upstream height. Machine learning algorithms, namely QNET and SVM, play a pivotal role due to their proficiency in uncovering intricate relationships between independent and dependent parameters, leading to significant time and cost savings. Our results using QNET and SVM indicate that the combination of (Cd, 𝐻𝑇/𝑝, θ, 𝐿𝐶/𝑊 ) yields optimal accuracy, with QNET achieving (R²=0.9850), (RMSE=0.0259), and (DC=0.9892) in the training phase, and (R²=0.9824), (RMSE=0.0292), and (DC=0.9788) in the test phase. For SVM, the training phase results are (R²=0.9889), (RMSE=0.0189), and (DC=0.9870), and in the test phase (R²=0.9881), (RMSE=0.0199), and (DC=0.9853). Sensitivity analysis shows the significant role of the total water load ratio parameter (𝐻𝑇/𝑝 ) in determining the discharge coefficient of arched labyrinth weirs. This research contributes to the understanding of non-linear arched weir discharge predictions and highlights the efficacy of QNET and SVM algorithms in this domain. [ABSTRACT FROM AUTHOR]

The flow capacity of the intake port has a great influence on the charging efficiency of the internal combustion engine, affecting the engine's performance, so it is critical to improve the intake port flow capacity. In this paper, the intake port numerical model was established, and the influence of the inlet and outlet area ratio on intake port flow capacity was studied. The results show that, under the same condition of relative pressure difference, the intake port discharge coefficient increases sharply and then slowly with an increase in area ratio. Under the same condition of area ratio, the discharge coefficient is only determined by relative pressure difference and decreases with an increase of relative pressure difference when the inlet and outlet area ratio > 1. The optimal area ratio decreases and then converges with an increase in relative pressure difference. When the intake port is designed, the optimal area ratio under the working condition of a smaller relative pressure difference should be applied in order to ensure the discharge coefficient is optimal under all working conditions. [ABSTRACT FROM AUTHOR]

Hydrogen is gaining attention as a clean energy source for the sustainable development of the global economy and mitigation of global warming. Flow rate measurements are vital for ensuring the accuracy of hydrogen transaction volumes. As a widely accepted standard for gas flow rate, critical flow nozzles are expected to fulfill this role. However, the discharge coefficient associated with the calibration tests of critical flow nozzles for high-pressure hydrogen does not align with the semi-empirical formula of ISO 9300 (ISO curve). This discrepancy has not yet been resolved. In this study, we conducted 3 D numerical simulations of the nozzle discharge coefficients for high-pressure hydrogen. Based on our simulations and experimental results from the previous study, we investigate the cause of the deviation of the discharge coefficient from the ISO curve at high pressure. We also propose a method for calculating the discharge coefficient based on real-gas effects and demonstrate that the discharge coefficient aligns with the ISO curve at high pressures. • High-pressure hydrogen flow is 3D-simulated in critical flow nozzles. • Theoretical mass flow rate of real gases is calculated in high-pressure critical nozzles. • Deviation of nozzle discharge coefficient from ISO curve under high-pressure is explained. • Calculated discharge coefficients of the proposed method match with the ISO curve. [ABSTRACT FROM AUTHOR]

Hospital readmission involves the unplanned emergency admission of patients within 30 days from discharge after the previous admission. According to the Canadian Health Institute (CIHI), 1 in 11 patients were readmitted within 30 days of leaving the hospital in 2021. In the USA, nearly 20% of Medicare patients were readmitted after discharge, where the average cost of readmission was approximately USD 15,000, as reported by the Agency for Healthcare Research and Quality (AHQR) in 2018. To tackle this issue, we first conducted a descriptive analysis study to understand the risk factors associated with hospital readmission, and then we applied machine learning approaches to predict hospital readmission by using patients' demographic and clinical data extracted from the Electronic Health Record of the MIMIC-III clinical database. The results showed that the number of previous admissions during the last 12 months, hyperosmolar imbalance and comorbidity index were the top three significant factors for hospital readmission. The predictive model achieved a performance of 95.6% AP and an AUC = 97.3% using the Gradient Boosting algorithm trained on all features. [ABSTRACT FROM AUTHOR]

A bridge versus culvert hydraulics approach may be taken to estimate the headwater of larger-span (or equivalently short) culvert-like structures, and design manuals often argue that the former should be technically preferred. A laboratory study was undertaken to investigate short and long box culverts, including roughness effects, with special attention paid to short-structure cases with entirely open-channel flow. The data were analyzed using discharge coefficients and approximate analytical models. Simulations were conducted with the HEC-RAS bridge model (with mainly default or recommended parameter values and options) and HY-8 to assess the predictive performance and benefits, if any, of a bridge versus culvert hydraulics approach. Observations support the presence of shortness and roughness effects, but do not support any significant advantage of a bridge versus culvert hydraulics approach. On the contrary, the performance of HY-8 was found to be superior to that of the HEC-RAS bridge model for rough-bed cases, perhaps fortuitously, due to its often conservative choice of parameter values. [ABSTRACT FROM AUTHOR]

Side weir is an effective control in streams. To study geometrical dimensions effect of the weir on the generated flow structure, here, experimental and numerical simulation analysis of the previous and present experimental studies was done on the flow around different geometric types of side weir. A triangular labyrinth side weir with three distinct included angles (θ = 30°, 45°, and 60°) and three weir heights (P = 10, 15 and 20 cm) has been tested, in addition normal rectangular side weir for comparison. The volume of fluid (VOF) approach was used for tracking free-surface subcritical flow conditions at the centerline of the main channel and near side weir banks. Accurate results were discovered by employing the Renormalization Group (RNG k-∈) turbulence model with the experimental outcomes. The smallest inclusion angle of side weir, generates smaller width of vortices zone near the upstream side weir wall which obstacles only a smaller length of crest as compared to the larger inclusion angle that hindrances larger length of this side for flowing water. In addition the contribution portion of the surface flow for the smallest inclusion angle which is indicated by streamlines is about 0.66 times the main channel width. Moreover, the maximum width of separation zone at the downstream of the main channel reached to 0.8 times the width of the main channel for the triangular labyrinth side weir. The stagnation point exists at the downstream end of side weir results the increase of surface elevation to reach maximum level. The coefficient of discharge of such weirs were 3.8, 2.7 and 2.12 times the coefficient of the normal rectangular side weir for θ = 30°, 45° and 60°, respectively. [ABSTRACT FROM AUTHOR]

A fuel injector plays a crucial role in an internal combustion engine, and the occurrence of cavitation inside the injector may affect the engine's spray, atomization, and combustion efficiency. In this study, a micro-turbojet engine equipped with a micro-orifice fuel injector was developed that operated under low injection pressure (Pinj), that is, at a low Reynolds number (Re). Given the paucity of cavitation studies conducted under such conditions, the current study experimentally and numerically investigated the cavitation and spray characteristics of water and kerosene in a micro-orifice injector with a diameter of 0.3 mm. The results indicated that the water and kerosene exhibited no cavitation, cavitation, supercavitation, and hydraulic flip. However, the discharged jet was unaffected by internal flows, and the jet angles remained nearly constant, indicating that the cavitation in micro-orifice injectors at a low Re is less important than that at a high Re. Because cavitation in micro-orifice injectors under a low Re has no positive effects on the atomization and spray, determining the geometry of a micro-injector is essential. The injector with a length-to-diameter (L/D) ratio of 3 exhibited an approximately 25% higher discharge coefficient (Cd) than those of injectors with L/D ratios of 6 and 8 and, thus, is recommended for injectors in micro-turbojet engines. [ABSTRACT FROM AUTHOR]

CFD models of intakes in high-head hydropower systems are rare due to the lack of geometric data and cost of modeling. This study tests two different types of software to see how modeling can be performed in a cost-effective way with scarce input data and still have sufficient accuracy. The volume of fluid (VoF) model simulations are conducted using both ANSYS Fluent and OpenFOAM. The geometry is modelled from Google Earth satellite images, drone scanning data, and design drawings from the construction period and supported by field observations for extra quality control. From the model, both capacity parameters and flow pattern are calculated. For capacity, the  C d  factor is calculated and compared with the literature. The simulations are conducted for a Tyrolean weir with rectangular bars (flat steel) in the rack. Simulated flow patterns through the rack with ANSYS Fluent and OpenFOAM are compared. OpenFOAM simulations yielded 15% to 20% higher water levels compared to the VOF model applied in Ansys Fluent. Also, when the flow rate was high, the water capture capacity calculated with ANSYS Fluent was 10% higher than that obtained with OpenFOAM. However, considering the total simulation times, modeling with OpenFOAM offered approximately 11% faster results. [ABSTRACT FROM AUTHOR]

In this study, experimental investigations were conducted on rectangular side weirs with different widths and heights. Corresponding simulations were also performed to analyze hydraulic characteristics including the water surface profile, flow velocity, and pressure. The relationship between the discharge coefficient and the Froude number, as well as the ratios of the side weir height and width to upstream water depth, was determined. A discharge formula was derived based on a dimensional analysis. The results demonstrated good agreement between simulated and experimental data, indicating the reliability of numerical simulations using FLOW-3D software (version 11.1). Notably, significant fluctuations in water surface profiles near the side weir were observed compared to those along the center line or away from the side weir in the main channel, suggesting that the entrance effect of the side weir did not propagate towards the center line of the main channel. The proposed discharge formula exhibited relative errors within 10%, thereby satisfying the flow measurement requirements for small channels and field inlets. [ABSTRACT FROM AUTHOR]

The present study used three machine learning models, including Least Square Support Vector Regression (LSSVR) and two non-parametric models, namely, Quantile Regression Forest (QRF) and Gaussian Process Regression (GPR), to quantify uncertainty and precisely predict the side weir discharge coefficient (Cd) in rectangular channels. So, 15 input structures were examined to develop the models. The results revealed that the machine learning models used in the study offered better accuracy compared to the classical equations. While the LSSVR and QRF models provided a good prediction performance, the GPR slightly outperformed them. The best input structure that was developed included all four dimensionless parameters. Sensitivity analysis was conducted to identify the effective parameters. To evaluate the uncertainty in the predictions, the LSSVR, QRF, and GPR were used to generate prediction intervals (PI), which quantify the uncertainty coupled with point prediction. Among the implemented models, the GPR and LSSVR models provided more reliable results based on PI width and the percentage of observed data covered by PI. According to point prediction and uncertainty analysis, it was concluded that the GPR model had a lower uncertainty and could be successfully used to predict Cd. [ABSTRACT FROM AUTHOR]

Background and Objectives: Labyrinth weirs are often a desirable design option to regulate upstream water elevations and increase flow capacity and the gate structures have some advantages including passing the floating substances and the sediments in using combined weir-gate structure. But, it can be difficult to design due to the complex flow characteristics of a labyrinth weir-gate. A labyrinth weir could be described as a continuous and broken weir plan in a trapezoidal or triangular form. Thus, for a fixed width, labyrinth weirs have a longer crest distance when compared to linear one. Most weirs create a relatively static water zone in their upstream, which can be the site for sedimentation and waste materials, which is a disadvantage of these structures. Because of the sediments deposition in upstream of the weirs the flow conditions change and the accuracy of the presented relationships is reduced. Although numerous methods of design have been published for labyrinth weirs, there is insufficient design information available about the combined models of Labyrinth weir-gate. Methodology: This study was conducted to improve labyrinth weir -gate design and analyses techniques using physicalmodel-based data sets. The experiments were conducted in a metal and glass flume with a rectangular crosssection. The flume was 0.25 m wide, 0.5 m deep, and 10 m long. In each test the upstream subcritical depth was measured using point gauges of 0.1 mm accuracy The location for measuring the total head of the water upstream of the weir is a horizontal distance of three to four times the maximum water head on the crest of the weir. The discharge was measured with a triangle sharp weir placed at the end of the flume. The dischargehead relationship (Q-h) for triangular weir in experiments is as Q=0.6918 h2.5. The trapezoidal labyrinth weirgate models was installed at the distance of 3 m of the beginning of flume. The base material roughness was made of natural sand with a mean diameter of 3 mm. In this research, experimental study of combined flow trapezoidal labyrinth weir-gate with one cycle has done for three sidewall angles of 15, 20 and 25 degrees, three gate openings 2, 4 and 6 cm and the weir height of 14 cm in a rectangular channel. According to the effective parameters of the combined models including sidewall angel (), gate opening (a) and the hydraulic head (Ht), the discharge coefficient has evaluated. By applying the Buckingham π theorem an equation was obtained. The discharge coefficient of trapezoidal labyrinth weir-gate can be expressed as a function of the variables of Fr, Re, We, ..., ϕ, α. In this study, the depth of water measured on the weir crest is at least 3 cm, so the effect of surface tension on the weir (We) is negligible. The effect of dynamic viscosity on the hydraulic behavior of the flow can be ignored. Therefore, the Reynolds number (Re) can be removed. Findings The results show that the discharge coefficient decreases with increasing the ratio of Ht/P for both smooth and rough beds and it reaches a constant discharge coefficient for Ht/P >0.6. According to the effective parameters of the combined models, the discharge coefficient has obtained averagely in the range of 0.61-0.75. The discharge coefficient of the combined flow increases with increasing angle of the weir. The increase in discharge coefficient is due to the decrease in the length of weir which decreases the flow mixing. Also for a specified angle, the discharge coefficient increases with increasing of L/Ht then gets a constant value. The effects of artificial roughness on discharge capacity are also presented. It can be shown that the discharge coefficient increases in rough bed condition compared to the smooth bed condition. The present test data and those of Crookston (2010) were compared and it can be seen that the discharge coefficient in combined flow trapezoidal labyrinth weir-gate is more than the discharge coefficient of the trapezoidal labyrinth weir (without gate) in Crookston (2010) investigation. Conclusion: The discharge coefficient of trapezoidal labyrinth weir-gate has the highest value for weirs with a sidewall angle of 25° and gate opening of 6 cm in rough bed condition about 17% more than the smooth bed. Among the different experimental models with a sidewall angle of 25, the labyrinth weir-gate in the rough bed condition has the highest discharge coefficient (approximately 0.93) compared to the smooth bed (approximately 0.61). [ABSTRACT FROM AUTHOR]

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This study investigates the viability of a strong algorithm (PSOGSA) merging particle swarm optimization (PSO) and gravity search algorithm (GSA) in tuning adaptive neuro-fuzzy system (ANFIS) parameters for modeling dimensionless experimental discharge of combined weir–orifices. The results are compared with the standard ANFIS and two hybrid models ANFIS tuned with PSO and GSA. The models are assessed by applying several dimensionless input parameters, consisting h/D (the ratio of upstream water depth to channel diameter), W/D (the ratio of orifice opening height to channel diameter), H/D (the ratio of plate height to channel diameter) and using comparison indices such as root-mean-square error and mean absolute error. The outcomes reveal that the new ANFIS-PSOGSA method provides superior accuracy in modeling dimensionless experimental discharge over the ANFIS-PSO, ANFIS-GSA and standard ANFIS method. Among the input parameters, the h/D was found to be the most effective input on modeling dimensionless experimental discharge while involving the H/D parameter deteriorated the models' performances. The relative root-mean-square error differences between ANFIS-PSOGSA and ANFIS are found as 50% and 68.29% for pipe A and B, respectively. By implementing the ANFIS-PSOGSA, the accuracy of ANFIS-PSO and ANFIS-GSA is also improved in modeling dimensionless experimental discharge by 45.71% and 29.63% in pipe A and by 63.89% and 45.83% in pipe B with respect to root-mean-square error. [ABSTRACT FROM AUTHOR]

This paper numerically studied supersonic film cooling performance in a convergent divergent nozzle, for the purpose of exploring and extending the knowledge of high-efficient cooling techniques for exhaust nozzles in real working conditions. The work was conducted with a steady state RANS approach with the SST turbulence model. The boundary conditions were chosen to mimic a real engine condition. The slot height and the inlet pressure ratio were varied to investigate the effect of the geometrical condition and flow condition. The flow field was analyzed in detail to study the phenomena of the supersonic secondary flow injected into the transonic flow. Besides the cooling effectiveness, the thrust coefficient and the discharge coefficient for the cooling cases were discussed together with the baseline case, to evaluate the influence of the supersonic coolant injection on the nozzle performance. The work can be a basis for the design of cooling schemes in an aero-engine exhaust nozzle. [ABSTRACT FROM AUTHOR]

This study numerically investigated the effects of geometric parameters of chimney weirs on the discharge coefficient (Cd). Here, chimney weirs with apex angles 74°, 84°, 94.4°, 106° and 116° at two crest heights were examined. The RNG turbulence model was selected due to its greater accuracy compared to k-ε, k-ω and LES methods for these types of flows. With increasing discharge and crest height, the value of Cd decreases. The effect of constant Cd showed an increase in the percentage of discharge deviation from the discharge values obtained from numerical solution. Based on dimensionless variables such as ratio of water head to the crest height, the ratio of crest length to the crest height, the ratio of the vertical distance between weir crest and the first point where the weir slope changes to the crest height, and the vertex angle of the inverted triangle, non-linear polynomial regression relations were obtained. Highlights A numerical investigation of the discharge coefficient of Chimney weir with different geometry has been done using FLOW-3D software. Chimney weirs have high reliability in measuring discharge due to less sensitivity to changes in upstream water depth. This investigation improves the design of hydraulic control structures. New equation was developed for calculating the discharge coefficient of Chimney weir. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to provide a numerical simulation, taking into account the collisional interactions of droplets in an airless rotary spray coating process. The hydrodynamics of gas and droplets are simulated using the CFD-discrete element method (DEM) with the JKR contact model in an airless rotary spray coating process of a horizontal square duct. The surface energy parameter used in the JKR model is calibrated using a virtual accumulation angle test in the funnel device. Based on the distribution of accumulation angles, a suitable surface energy for wall droplets is proposed. A rational gas RNG k-ε model is suggested in accordance with the comparisons of velocities, standard deviations, and the skewness of droplet number fractions from three turbulence models. The simulations of droplet film thicknesses agree with measurements from the literature regarding the film thickness along a vertical panel. The correlations of the exit gas and droplet velocities of sprayer holes are proposed with a discharge coefficient of 0.85 for gas and 5.87 for droplets. A number index of droplets is introduced in order to measure the uniformity of droplet distributions. A low droplet number index is found at low rotational speeds, representing a more uniform distribution of droplets as the rotation speeds reduce within the square duct. The normal force between the droplet and the wall is approximately an order of magnitude larger than the droplet–wall tangential force of collisions. [ABSTRACT FROM AUTHOR]

Nowadays, streamlined weirs including circular crested weirs and hydrofoil weirs have been introduced as the weirs with high discharge coefficient (Cd). In this study, the Cd e of circular crested weirs including cylindrical, semicircular and quarter-circular weirs were compared with the hydrofoil weirs. This was done using data published in reputable journals. The trend of the published data showed that the o Cd f of the semicircular and cylindrical crested weirs are close to each other and vary between 1.00 and 1.40. The Cd e of the quarter-crested weirs varies between 1.00 and 1.25 and the Cd of the hydrofoil weirs varies between 0.95 and 1.05. It should be noted that for all models, the range of the ratio of crest height to weir height varied between 0.5 and 2.10. The results showed that the Cd of the semicircular weir was about 30% higher than that of the hydrofoil weir. The Cd of semicircular weirs is about 10 percent higher than that of quarter-circular crested weirs.

In this paper, the discharge coefficient prediction model for this structure in a subcritical flow regime is first established by extreme learning machine (ELM) and Bayesian network, and the model's performance is analyzed and verified in detail. In addition, the global sensitivity analysis method is introduced to the optimal prediction model to analyze the sensitivity for the dimensionless parameters affecting the discharge coefficient. The results show that the Bayesian extreme learning machine (BELM) can effectively predict the discharge coefficients of the symmetric stepped labyrinth side weir. The range of 95% confidence interval [−0.055,0.040] is also significantly smaller than that of the ELM ([−0.089,0.076]) and the Kernel extreme learning machine (KELM) ([−0.091,0.081]) at the testing stage. The dimensionless parameter ratio of upstream water depth of stepped labyrinth side weir p/y1 has the greatest effect on the discharge coefficient Cd, accounting for 55.57 and 54.17% under single action and other parameter interactions, respectively. Dimensionless step number bs/L has little effect on Cd, which can be ignored. Meanwhile, when the number of steps is less (N = 4) and the internal head angle is smaller (θ = 45°), a larger discharge coefficient value can be obtained. HIGHLIGHTS The discharge coefficient model of a symmetrical stepped labyrinth side weir is developed.; The quantitative model of the discharge coefficient is established.; The discharge characteristics of a symmetrical stepped labyrinth side weir are analyzed comprehensively.; The effects of different dimensionless parameters on the discharge coefficient are compared.;

ABSTRACTNonlinear weirs offer a relatively high discharge capacity under low water loads. Their efficiency, however, is decreased at high water loads due to the submergence of the weir outlet key. In the present study, sloping parapet walls with the heights of 2, 4, and 6 cm and lengths of 60 and 30 cm were added to trapezoidal labyrinth weir and piano-key weirs in order to reduce the submergence at the weir inlet. The experiments were conducted in a test flume with a length of 7 m and a width and height of 0.6 m. Results of this study suggested that addition of the sloping parapet walls could reduce discharge coefficient by at least 10% and 13% in Piano-Key Weirs and labyrinth weirs respectively as compared to the control cases. Also, after addition of the parapet walls, Piano-Key Weir outperformed labyrinth weir by up to 19% in terms of the discharge coefficient. The highest efficiency of parapet wall for Piano-Key Weirs was found to be corresponding to parapet wall length and height of 30 cm and 2 cm respectively which differed from that of labyrinth weir of the same parapet wall dimensions by 14%. In fact, the addition of the parapet walls to the labyrinth and piano-key weirs increases the efficiency at high discharges by up to 40%.

ABSTRACTTriangular plan form weirs are one type of long-crested weirs. Therefore, they can pass more discharge capacity than weirs at the given channel width. This study aims to investigate the effects of different number of teeth (3, 4, and 5 teeth), angle of the weir tip (90, 60, 120, and 150 degrees), and the amount of different discharges (0.009–0.0063 m3/s) of sharp-crested triangular plan form weirs on the hydraulic parameters by using the Finite Volume Method (FVM). It was found that, increasing the effective length of the crest, increases the discharge coefficient up to 95% in the case with 5 teeth (L/B = 4.14 and h/W = 0.128), 45% in the case with 4 teeth (L/B = 3.71 and h/W = 0.168) and 39% for 3 teeth (L/B = 3.28 and h/W = 0.188) compared to the simple triangular plan weir (without teeth). Also, Results indicated that the discharge coefficient has an inverse relationship with the h/w ratio. In contrast, the investigations showed that the velocity in the flow jet is affected by the effective length of the triangular plan crest, and the increase in the effective length results in a decrease in the average velocity of the flow jet. So that these disturbances caused the highest dissipation of energy to occur in the triangular plan crest with 5 teeth (27% compared to the upstream section (Section 1) and 37% compared to the downstream section (Section 2)).

ABSTRACTNonlinear weirs are among the major structures used in water transfer. Thus, these structures have been the subject of various studies. This study investigates the effect of flow splitters on discharge performance of trapezoidal and triangular labyrinth weirs of one cycle. This study delves into the effects of flow splitters installed on the crest of trapezoidal and trapezoidal one-cycle labyrinth weirs using numerical methods (Flow-3D) and physical models. In the physical model, two, four, or six vanes were placed on the crest at regular intervals. The results showed that the triangular weir offered 4% higher efficiency than its trapezoidal counterpart and that the vanes had better effects on the trapezoidal weir. The vanes can improve the weir efficiency by up to 11%, and the discharge coefficient was found to be 10.2% higher in the numerical simulation than in the physical model.