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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]

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]

This study combines the experimental and numerical simulation methods to deeply analyze the impact of liquid crossflow on the discharge coefficient of a gas jet hole on a flat plate. Experiments were conducted to examine the influence of momentum flux ratio and theoretical momentum flux ratio on the discharge coefficient under various crossflow Reynolds numbers. It was found that the variation of the discharge coefficient with the theoretical momentum flux ratio clearly reflects the impact of the crossflow boundary layer velocity profile on the discharge coefficient. The rapid growth of velocity in the boundary layer near the wall in the direction normal to the wall surface, or the decrease in the thickness of the boundary layer, both enhance the shearing effect of the crossflow, leading to a decrease in the discharge coefficient. Analysis of the cavity morphology at the hole exit captured by high-speed camera revealed that the averaged profile of the gas–liquid boundary on the symmetrical plane of the jet below the hole can be approximated as a straight line within the scale of the hole diameter, and the sine of the angle between this line and the upper wall surface is roughly equivalent to the normalized discharge coefficient. This relationship was physically interpreted through the analysis of effective and equivalent flow cross-sectional shapes derived from numerical simulation at different crossflow Reynolds numbers and theoretical momentum flux ratios. Additionally, this paper introduces an innovative method for predicting jet flow rate based on image processing technology. A notable feature of this method is that it does not require the measurement of the pressure inside the gas chamber. [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]

Aims: Interatrial shunts are under evaluation as a treatment for heart failure (HF); however, their in vivo flow performance has not been quantitatively studied. We aimed to investigate the fluid dynamics properties of the 0.51 cm orifice diameter Ventura shunt and assess its lumen integrity with serial transesophageal echocardiography (TEE). Methods and results: Computational fluid dynamics (CFD) and bench flow tests were used to establish the flow‐pressure relationship of the shunt. Open‐label patients from the RELIEVE‐HF trial underwent TEE at shunt implant and at 6 and 12 month follow‐up. Shunt effective diameter (Deff) was derived from the vena contracta, and flow was determined by the continuity equation. CFD and bench studies independently validated that the shunt's discharge coefficient was 0.88 to 0.89. The device was successfully implanted in all 97 enrolled patients; mean age was 70 ± 11 years, 97% were NYHA class III, and 51% had LVEF ≤40%. Patency was confirmed in all instances, except for one stenotic shunt at 6 months. Deff remained unchanged from baseline at 12 months (0.47 ± 0.01 cm, P = 0.376), as did the trans‐shunt mean pressure gradient (5.1 ± 3.9 mmHg, P = 0.316) and flow (1137 ± 463 mL/min, P = 0.384). TEE measured flow versus pressure closely correlated (R2 ≥ 0.98) with a fluid dynamics model. At 12 months, the pulmonary/systemic flow Qp/Qs ratio was 1.22 ± 0.12. Conclusions: When implanted in patients with advanced HF, this small interatrial shunt demonstrated predictable and durable patency and performance. [ABSTRACT FROM AUTHOR]

Evaluation of hydraulic parameters in an open channel plays a pivotal role in the design and estimation of different hydraulic characteristics; therefore, an experimental-based research study was conducted on different canals tertiary in the command of three distributaries falling in the hydraulic boundaries of the Jamrao canal. Keeping in the view objectives of the study, the recorded data of hydraulic characteristics (discharge, wetted perimeter, roughness coefficient, and bed slope) were determined and correlated using simple linear regression analysis for earthen watercourses to develop the empirical equations for important hydraulic characteristics. An empirical equation for the roughness coefficient has developed which is simple and explicit for computing the value of the roughness coefficient as compared to Universal Manning's formula. The comparison of observed values of important hydraulic characteristics and roughness coefficient computed from empirical equations for the watercourse has yielded satisfactory results. The mean absolute error of important hydraulic parameters viz. discharge, wetted perimeter, roughness coefficient, and bed slope is in the order of ±10.23%, ±4.25%, ±9.9%, and ±3.2% respectively. The value of the coefficient of determination (R2) for the set of these equations is within the range of 78 to 96% which is the indicator of an excellent correlation within the variables. The general empirical equations developed from this study can fairly be used in determining the flow variables particularly discharge in the tertiary canals without using a cumbersome method that is a cut-throat flume and associated monographs. [ABSTRACT FROM AUTHOR]

Seawater desalination is increasing due to the global water crisis, and velocity caps are widely used at intake entrances to protect marine life and facilitate the required flow. Despite various investigations of seawater intake, a lack of precise research on the discharge coefficient of these structures is evident. The discharge characteristics of seawater intake are investigated both analytically and experimentally. Results show that the circle velocity caps have higher capacity than square ones, about 2% to 3.5%. Also, the Froude number of approach flow and the area of the velocity caps are the two parameters with the greatest impact on discharge coefficients. However, the height of caps and the number of separator blades have the least effect. Furthermore, some equations of discharge coefficients are developed based on machine-learning techniques with appropriate accuracy. Additionally, the Taguchi method, evaluated as an economical approach, significantly reduces the number of tests while the accuracy of results decreases. [ABSTRACT FROM AUTHOR]

Measuring and controlling flow in conduits is one of the most important issues in the management and operation of irrigation and drainage systems. Investigations on this issue are of great importance for cost-effectiveness and ease of operation, construction, as well as increasing the accuracy of flow measurement and control. In this research, the hydraulic parameters of the flow on multiple elliptic lopac gates in submerged flow conditions have been investigated. This study was done using Flow3D fluid dynamics simulation software. The simulations are performed in three flow rates 20, 40, and 60 liters per second, three opening rates 30, 45, and 60 degrees and three absorption rates 70, 80, and 90 percent. The maximum flow velocity, discharge coefficient and flow vortices are investigated, and their analysis is described. Regarding the maximum velocity, the results showed that when using lopac elliptic gates in submerged conditions compared to free flow conditions, the maximum velocity in the flow rates (20, 40 and 60) liters per second in the opening of 30 degrees on average for the amount of absorption (70, 80, and 90) percent will decrease by 9, 30, and 54 percent, respectively, at 45-degree opening, by 8, 22, and 38 percent, and at 60-degree opening, by 12, 22, and 44 percent, respectively. The results regarding the Discharge coefficient showed that when multiple lopac elliptic gates are used in submerged conditions compared to free flow conditions, the Discharge coefficient in the flow rates of (20, 40, and 60) liters per second in the opening of 30 degrees on average For the extraction rate (70, 80 and 90) percent, 8, 26 and 45%, respectively, at 45 degree opening, 16, 34 and 49%, respectively, and at 60 degree opening, 17, 36 and 54%, respectively will find Finally, the observations showed that when multiple elliptic lopac gates are used in free flow conditions, high-strength vortices are formed compared to multiple elliptic lopac gates in submerged flow conditions. However by examining the flow pattern of multiple elliptic lopac gates in submerged flow conditions, the size of the eddies has decreased, and as a result, its strength has decreased. [ABSTRACT FROM AUTHOR]

In the present study, we develop a theoretical model for predicting hydrogen jet ignition in a shock tube with a partially opened diaphragm for hydrogen as a driver gas and air as a driven gas. Effects of pressure losses associated with the gradual diaphragm opening process are taken into account by developing a new discharge coefficient model. The discharge coefficient for incompressible flows is first calculated and then converted into the discharge coefficient for compressible flows. Three regimes are identified for the discharge coefficient, which depend on whether the ruptured portion of the diaphragm, which remains attached to the orifice, is negligible or not. We extensively validate the new model against experimental results from the literature. We show that the critical initial pressure ratio across the diaphragm and the shock-wave strength required for ignition can be calculated in a conservative manner with a maximum relative error equal to 9% and 10%, respectively, for the ratio of diaphragm opening area to driven-section cross-sectional area from 0.125 to 1.0. Finally, we explore, via our new model, the influence of different parameters on the shock-wave Mach number and ignition limits. We show that all our model predictions can be generalized into two simple dimensionless correlations. [Display omitted] • Three regimes are identified for the discharge coefficient. • Model predicts the ignition limits within 9% of experimental values. • The ignition limit is constant for area ratios between 0.52 and 1.0. • Model predictions can be generalized into two correlations. [ABSTRACT FROM AUTHOR]

Due to their superior technical and hydraulic performance and minimal environmental impact, porous weirs have emerged as a feasible alternative to traditional impermeable solid weirs in water transmission and distribution systems. This research study assesses the hydraulic performance of porous broad-crested weirs (PBCWs) with sloping crests. To accomplish this, 30 PBCW models were designed and tested under various operating conditions, including free and submerged flow scenarios. A comparative analysis was conducted to evaluate the performance of PBCWs with and without sloping crests, with the results being compared against a solid broad-crested weir (SBCW) model. The findings revealed that PBCWs with an upstream crest slope exhibited an average increase of 38% in the discharge coefficient compared to similar SBCWs. Similarly, PBCWs with a downstream crest slope demonstrated an average increase of 28% in the discharge coefficient. Additionally, PBCWs with sloping crests showcased heightened sensitivity to changes in tailwater levels compared to PBCWs with horizontal crests, with PBCWs featuring an upstream crest slope being more responsive than those with a downstream crest slope. Finally, leveraging extensive experimental data, empirical equations were derived using nonlinear multi-variable regression and gene-expression programming techniques to accurately represent the free flow discharge coefficient and submerged flow discharge reduction factor. [ABSTRACT FROM AUTHOR]

In this study, a one-dimensional mathematical model based on rigid theory is developed to evaluate the maximum water filling flow rate and filling time of closed pipeline water supply systems during rapid-filling processes. Polynomial fitting is utilized for prediction, and numerical simulation results are analyzed to understand the variations in maximum water filling flow rate, filling time, and pressure with respect to opening valve time, air valve area, filling head, and segmented filling pipe length. The findings highlight the significant impact of the filling head on the maximum water filling flow rate, while the filling time is predominantly influenced by the gas discharge coefficient. Rapid changes occur only at the initial stage of rapid filling, reaching the maximum value with a very high acceleration (around t = 4 s). It is observed that pressure fluctuations in the gas–liquid two-phase flow inside the pipeline lead to velocity differences and periodic changes in gas pressure opposite to the filling head. When the gas discharge coefficient reaches approximately 0.3, pressure variation within the water supply system diminishes, and the time and flow rate required for pipeline filling become independent of the discharge coefficient. This study suggests the use of a segmented filling approach to ensure the effectiveness and stability of pipeline filling. [ABSTRACT FROM AUTHOR]

Labyrinth weirs are well known for their superiority in providing higher flow capacity for a given hydraulic head, especially in areas where space is limited. This study presents an experimental and numerical study to determine the hydraulic efficiency of triangular labyrinth weirs. The discharge coefficient of a weir was determined in two different ways, depending on the width of the channel (Cd) and the length of the crest of the weir (CL). Although the crest length is the most important factor in increasing the discharge coefficient per unit channel width, the discharge coefficient per unit crest length decreases with increasing the crest length for a given head. It can be said that the main reason for the reduction in weir efficiency, particularly at high headwater, is nappe interference and therefore local submergence between cycles. From the results of systematic analyses, some new highly correlated multiple regression equations calculating these two coefficients in relation to the weir geometries and the flow conditions were obtained. As a result of the literature comparison, although they were found to be generally compatible with the results of similar studies in the literature, the reasons for the differences between them were discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Chinese solar greenhouse (CSG) is a prevalent feature in agricultural practices within China. Nevertheless, the regulation of natural ventilation within this architectural structure remains suboptimal. Consequently, the development of a natural ventilation model becomes imperative for the effective management of the greenhouse environment. Of particular significance within these models is the consideration of the discharge coefficient as a pivotal parameter. Conducting a multi-case investigation into the variable-dependent discharge coefficient is crucial for both practical application and model advancement. This research delved into the impact of various factors, including the upper-lower vents area ratio (Aup/Alow), vent-greenhouse area ratio (Alow/Agreenhouse), lower vent position height (h/H), the incident angle of the external wind, and altitude, on the discharge coefficient (Cd) of CSG. A CFD model was developed for a scaled CSG with validation conducted through field experiments and wind tunnel tests. Results indicated a 61.6% reduction in Cd on average corresponding to an 80% decrease in Aup/Alow. Cd levels remained consistent following the attainment of an Aup/Alow ratio of 1.0. Besides, there was an average increase of 52.5% in Cd levels for every 0.09 decline in h/H, attributed to the blocking effect of the cover. Moreover, the ventilation rate and the pressure coefficient difference were utilized to construct a model of Cd pertaining to greenhouse design and ventilation operation, exhibiting a notable accuracy level of R2 = 0.95. Furthermore, the blocking effect of higher h/H was relieved as the incident angle θ decreased under the windward conditions. The increase in Aup/Alow and the decrease in Alow/Agreenhouse were identified as crucial factors contributing to the growth of Cd under leeward conditions. Ultimately, the high-altitude environment led to a rise in Cd levels in contrast to the low-altitude region. The increasing rate of Cd correlated positively with Alow/Agreenhouse and h/H initially, but exhibited a decline once Alow/Agreenhouse reached 0.036, remaining stable thereafter once h/H reached 0.18. In summary, a comprehensive examination of the discharge coefficient of CSG was undertaken, addressing a significant knowledge deficiency and laying the groundwork for advancements in the natural ventilation model and the intelligent control system for CSG. [ABSTRACT FROM AUTHOR]

Accurately evaluating the buoyancy and stability of damaged ships, particularly the flow rate of the water inflow through damaged openings, is of great significance for ship rescue and emergency repair. A three-dimensional simplified model of inflow for a ship's damaged side bulkheads is established using the shear stress transport k-epsilon and volume of fluid (VOF) models by STAR-CCM+. Moreover, the flow rates of water inflow through damaged openings with different shapes, characteristic sizes, and central depths are calculated. Furthermore, the corresponding discharge coefficients are obtained, and the relevant rules are summarized. It was found that the influence of water depth on the coefficient is minimal in these work conditions, but from the perspective of the damaged opening's characteristic dimensions and shape, the variation in the coefficient is more pronounced. Overall, the triangular opening has a higher coefficient than the circular opening, which in turn is higher than that of the square-damaged opening, and the coefficient decreases as the size of the opening increases. Lastly, empirical formulas for two different methods are provided. The research provides a reference for the rescue repair and buoyancy stability assessment of damaged ships. [ABSTRACT FROM AUTHOR]

Weirs are hydraulic constructions typically employed in dam spillways and channel control structures. The shape and size of the crest will determine whether the weir is linear or nonlinear. Of the two types, non-linear weirs are often selected due to their ability to allow different discharge levels at the minimal heads. A recently introduced variation of the nonlinear kind is the piano key weir. This research undertakes a comprehensive analysis of the hydraulic functionality of the type-C piano key weir under conditions of free flow. The research methodology involved modifying the models by adding stages to the sides and monitoring the effect on the efficacy of discharge, represented by the discharge coefficient. The study further extrapolated formulae linking critical variables to the discharge coefficient, using dimensional analysis and SPSS software. The findings of this study revealed that the introduction of stages significantly bolstered the discharge coefficient in the altered models compared to the standard model. This enhancement was reflected in a 6% and 11% ascent with length expansion of the stages and a 6% and 8% rise with height increase of the stages. Additionally, the model's performance was augmented with a drop in the total head ratio. [ABSTRACT FROM AUTHOR]

High-quality development of water resources supports high-quality socio-economic development. High-quality development connects high-quality life, and clarifying the key management contents of small watersheds plays an important role in building ecologically clean small watersheds and promoting regional production and life. Previous research on pollution loads has focused on examining the impact of various external drivers on pollution loads but still lacks research on the impact of changes in pollution sources themselves on pollution loads. In this study, sensitivity analysis was used to determine the impact of changes from different sources on the total pollution loads, which can recognize the critical pollution sources. We first employed the pollutant discharge coefficient method to quantify non-point source pollution loads in the small watershed in the upstream Tuojiang River basin from 2010 to 2021. Then, combination sensitivity analysis with Getis-Ord Gi* was used to identify the critical sources and their crucial areas at the global, districts (counties), and towns (streets) scales, respectively. The results indicate: (1) The pollution loads of COD, NH3-N, TN, and TP all show a decreasing trend, reducing by 18.3%, 16.2%, 18.6%, and 28.1% from 2010 to 2021, respectively; (2) Livestock and poultry breeding pollution source is the most critical source for majority areas across watershed; (3) High-risk areas are mainly concentrated in Jingyang district and its subordinate towns (streets). There is a trend of low-pollution risk areas transitioning to high-pollution risk areas, with high-risk areas predominantly concentrated in the southeast and exhibiting a noticeable phenomenon of pollution load spilling around. This study can promote other similar small watersheds, holding significant importance for non-point source pollution control in small watersheds. [ABSTRACT FROM AUTHOR]

Several means are used for flow measurement, including the flumes that are of interest to the present study. The operating principle of the flume is based on the lateral contraction of the walls of a trapezoidal channel that ends in a triangular section extended by a throat of the same section. The convergent part of the flume accelerates the flow from a subcritical state to a critical state in the throat where a control section is created. Thus, the flow can be determined by taking a single depth reading in the inlet cross-section of the flume. The recommended device is simple and compact in shape, requiring a minimum of space compared to known trapezoidal flumes. Furthermore, the device has been designed to be used in open channels regardless of the shape. Therefore, the flume has the property of being of a universal range. A rigorous theoretical development led to the derivation of the governing discharge coefficient Cd relationship, solely depending on the dimensionless parameter M1 = mh1/b1, where m is the side slope of the flume, h1 is the upstream flow depth, and b1 is the inlet cross-section width of the converging part of the flume. Based on 1023 pairs of values Q-h1 collected from twelve tested flumes of different practical dimensions, the in-depth analysis of laboratory observations corroborated the validity and reliability of the theoretical relationship governing Cd within the wide range 0.10 ≤ M1 ≤ 0.95, since the maximum deviation is only 0.215% when compared to observations. Among the twelve tested devices, only the results of the observations carried out on one device will be presented herein. The observations collected on this device are considered the most unfavourable compared with those carried out on the eleven other tested devices, especially regarding the deviation affecting the discharge coefficient Cd. [ABSTRACT FROM AUTHOR]

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 %).

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.

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.

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.

ABSTRACTWeirs 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.

ABSTRACTThis 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.

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 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]

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]

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]

Abstract The broad‐crested weir is convenient to construct and has a small amount of excavation, widely used in practical engineering. Discharge computing has been the focus of research on this structure, thus developing generalized regression neural network (GRNN), genetic programming (GP), and extreme learning machine (ELM) are used to predict the discharge coefficient (Cd) of the triangular broad‐crested weir. The comprehensive analysis shows that the ELM model has high stability, predictive ability, and computational speed. The coefficient of determination (R^2) is 0.99982, the mean absolute percentage error (MAPE) is 0.000261, the Nash‐Sutcliffe coefficient (NSE) is 0.99977, and the root means square error (RMSE) is 4.17E‐05 in the testing phase. The apex angle θ is the most critical parameter affecting the Cd, and the contribution to the Cd is 52.45%. A new computational formula is proposed and compared with the accuracy of empirical formulas, showing that the intelligent method has higher accuracy and efficiency.

The current study deals with a composite broad-crested weir which is specially designed with the unique idea for a ‘constant discharge coefficient (Cd) of 0.6’. It is investigated experimentally and numerically. The available designs of the weir are unable to give constant Cd over a wide range of discharge as ‘Cd’ itself is relative to the head over the weir crest. Therefore an attempt is made to restrict Cd value to 0.6 irrespective of the variable head on the weir crest. This is achieved by adjusting the widths of the weir. With the novel objective, Cd is frozen to constant value and instead of it, ‘b’ is allowed to vary. The weir so designed is capable of producing constant Cd over a wide range of discharge and hence will be helpful from the viewpoint of field applications. Under existing laboratory conditions, the research reports for emissions varying from 20 to 100% of the design discharge. The numerical performance of the CBC weir through FLOW 3D is experimentally validated to examine the crest width effect and head over weir crest. In the experiments, Cd is found to vary proportionally with discharge from 0.518 to 0.648. The R-value is 0.999, with a mean error in discharge measurement being much less. HIGHLIGHTS The available designs of the weir are unable to give constant Cd over a wide range of discharge as ‘Cd’ itself is relative to head over weir crest.; Thus, an attempt was made to restrict the Cd value (0.6) irrespective of the variable head on weir crest.; This is achieved by controlling head over weir by adjusting the widths of weir.; With the novel objective, Cd is frozen to a constant value and instead, ‘b’ is allowed to vary.;

Accurate control of water injection rate is a key to separate-layer water injection technology, especially in low-permeability reservoirs. Firstly, a dynamics model of the two-layer water injection system was established. Then, the relationship between the discharge coefficient and the opening of the water nozzle was obtained, and the consistency between the simulation and the experiment was verified. Finally, the simulation results revealed that the increase of the water injection rate and the decrease of the pressure difference between the reservoirs are beneficial to the automatic adjustment of the nozzle. The proposed method can improve reservoir development significantly. Discharge coefficients for different openings of fan nozzles obtained by simulation. Relationship among water injection pressure, water injection rate, and nozzle opening are calculated. Accurate control method of separate-layer water injection rate is proposed. [ABSTRACT FROM AUTHOR]

Building flood reduction dams for territory protection is very often necessary as it allows the reduction of peak flows during flood events by creating a storage in upstream areas. An online structure with such characteristics is outlined, presenting one or more openings in order to allow normal and moderate flows to pass downstream. A stilling basin is provided downstream of the openings and, on one side of the flooded area, a spillway weir is set. For low river flows, the openings will act as free-surface weirs. The openings are equipped with a sill in such a way to let the discharge independent of the downstream flow conditions. For moderate flood flows, the water level upstream of the dam will rise, and the openings will become submerged, effectively behaving as an orifice arrangement. For large flood flows, the crest of the flood spillway weir is reached and they will be discharged via both the orifice structure and the flood spillway structure. The silled openings and the stilling basin are one only hydraulic complex. Since no examples exist of their behavior as a whole, the aim of this paper is to give the designers the opportunity to size them given the basic requirement of the flood reduction dam, i.e. the max discharge allowed downstream. For this reason, the paper will focus on the opening discharge coefficients, the stilling basin energy dissipation and water level. Both the orifices and the stilling basins were studied starting from the hydraulic models of three dams that were built in Calabria (Italy). The structures of the stilling basins are original. The results appear in dimensionless form and offer useful guidance for similar hydraulic cases, with the exception of specific terrain related issues. Finally, an example of a preliminary design of orifices and stilling basin is presented. [ABSTRACT FROM AUTHOR]

For inherently compensated aerostatic bearings, the traditional modeling method of describing an air supply orifice with a nodal point results in computational errors when numerical discretization methods, such as the finite difference method, are used particularly for a small air-film thickness. To address this problem, this paper proposes an equivalent pressure-equalizing chamber model (EPECM) to consider the pressure depression around the orifice. First, numerical simulations of the circular centrally fed aerostatic thrust bearing (CCFATB) were conducted using computational fluid dynamics. The discharge coefficient and the radius of the pressure-depression region under various operation conditions were obtained. Subsequently, by combining these two key parameters, the EPECM was applied to analyze the static performances of the CCFATB and annular aerostatic thrust bearing (AATB). The air domain of the AATB was divided into non-uniform grids. The five-point difference scheme and nine-point difference scheme were adopted to solve the Reynolds equation respectively, and the computational results were compared. The proposed model and discretization method were verified by comparing the results with experimental and published data. It is found that the EPECM has a high computational accuracy and superior numerical iteration efficiency compared with the commonly used point-source assumption. The five-point difference scheme is able to deal with the non-uniform mesh model accurately. Moreover, the modified discharge coefficient and pressure-depression region radius calculated in this study provide useful data for performance analysis of inherently compensated air bearings. [Display omitted] • The computational error of the point-source assumption in the modeling of aerostatic bearings is studied. • An improved model is proposed to consider the pressure depression around the orifice. • 576 bearing models are established through CFD dynamic mesh method and the modified discharge coefficient and pressure-depression region radius are obtained. • High computational accuracy and superior numerical efficiency are achieved by using the improved model. [ABSTRACT FROM AUTHOR]

Based on the principles design of hydrofoil weirs, Modified Semi-Cylindrical Weirs (MSCWs) incorporate an innovative tangential ramp along the downstream crest contour, thereby significantly enhancing their performance compared to conventional semi-cylindrical weirs. A pivotal parameter in the calculation of flow discharge over the weir is the discharge coefficient (Cd). This study involves a comprehensive comparative analysis of various Cd estimation methodologies for MSCWs, employing a range of machine learning-based models, notably including Artificial Neural Network (ANN), Multivariate Adaptive Regression Splines (MARS), M5 tree, Locally Weighted Polynomial Regression (LWPR), and Support Vector Machine (SVM) models. To begin, a feature selection analysis utilizing the Gamma Test (GT) method was conducted to identify the optimal input configuration for modeling the discharge of MSCWs. The results of the feature selection revealed that the Cd of the MSCWs is primarily influenced by the ratio of upstream flow depth (yup) to crest radius (R), while showing negligible sensitivity to the slope of the downstream ramp (θ). The dataset was partitioned into two segments: 70% were assigned to the training stage, while the remaining 30% were allocated to the testing stage. The precision of Cd predictions is evaluated through four key statistical metrics: Mean Absolute Error (MAE), Mean Squared Error (MSE), Root Mean Square Error (RMSE), Correlation Coefficient (R2), and Nash –Sutcliff Efficiency (NSE). The outcomes reveal that, for the training and testing phases, the R2 values for the ANN, MARS, M5 tree, LWPR and SVM models are respectively 0.967, 0.931, 0.974, 0.937, and 0.933, and 0.925, 0.953, 0.953, 0.980, and 0.954. Notably, the LWPR model outperforms the ANN, MARS, M5 tree, and SVM models, boasting MAE, MSE, RMSE, and NSE values of 0.0167, 0.0005, 0.0217, and 0.942 during training, and 0.0107, 0.0002, 0.0136, and 0.949 during testing. As a result, the LWPR model clearly emerges as the superior model, followed by the M5 model tree. [ABSTRACT FROM AUTHOR]

The aim of this study is to numerically investigate the effect of bed slope on the hydraulic performance of side weirs in supercritical and subcritical flow regimes. Increasing the bed slope decreases the weir efficiency and discharge coefficient in the subcritical flow regime up to 14.54% and in the supercritical flow regime up to 9.26%. By examining the longitudinal velocity distribution, it was observed that in the subcritical flow regime, the maximum longitudinal velocity occurs at the beginning of the upstream of the side weir, and by moving towards the downstream of the weir, the flow velocity decreases and increases again after leaving the length of the weir. In the supercritical flow regime, it has an increasing trend when the flow enters from the upstream of the side weir. The increase in discharge coefficient with the increase of the weir height varied between 4.6% and 7.8%. With increase of the slope of the channel bed, the velocity along the length of the weir increases by 10.88% and 6.17%, respectively, in the subcritical and supercritical regimes, and the transverse velocity along the transverse direction for the subcritical and supercritical flow regimes decreased by 22.23% and 4.80%, respectively. [ABSTRACT FROM AUTHOR]

Tip leakage loss significantly influences aerodynamic performance of high-pressure turbines, with squealer tips serving as an effective control strategy. The development of a tip leakage loss model is crucial for evaluating and predicting turbine aerodynamic performance and guiding blade tip design. This study presents a novel leakage loss model for squealer tips, employing a hybrid approach that integrates physics-driven and data-driven methodologies, followed by comprehensive validation. The leakage flow within the squealer tip gap is modeled into three basic flows: Vena contracta motion in both the pressure-side and suction-side squealer tip gaps, and jet diffusion inside the cavity. The specific flow pattern and loss magnitude inside the cavity are intricately linked to the evolution of the scraping vortex. The paper introduces a methodology for modeling the scraping vortex through deep learning, grounded in the separation and reattachment theory of backstep flow. Subsequently, it presents a physical model of the leakage flow across the squealer tip gap, informed by the classical theories of three identified basic flows and the scraping vortex's behavior. The influences of complex factors that are challenging to address solely through physical modeling are also taken into consideration with the aid of machine learning. The proposed model enables a rapid and precise prediction of key flow features, such as scraping vortex characteristics, discharge coefficient, leakage flow rate and momentum, alongside total leakage flow rate and leakage loss. This model provides a reliable analytical tool for predicting leakage performance and guiding designs for the squealer tip. [ABSTRACT FROM AUTHOR]

After a check dam is filled with sediment, the debris flow will flow out from the spillway. Insufficient discharge capacity of the spillway can lead to debris flow scouring the dam's shoulder and foundation. Therefore, it is necessary to study the discharge capacity of the spillway. It is of great importance for further optimizing the structural design of the check dam. This article analyzes discharge characteristics of debris flow of a spillway through a series of flume experiments. According to the motion states, it can be divided into five stages: contact stage of the spillway, flushing and climbing stage, increasing and reflux stage, stable discharge stage, and final discharge stage. We analyzed the influencing factors of the discharge capacity, including the type of spillway, bulk density of debris flow, scale of debris flow, flume gradient, and effective opening width of the spillway. Furthermore, we derived a calculation formula of discharge for the spillway based on Bernoulli's principle. Finally, we considered the influence of the ratio of flow area and Froude number to the discharge coefficient and established a calculation method of discharge. Consequently, we compared the calculated results with the measured results and found them to be in good agreement. Our research results provide a quantitative calculation method for the design of spillways and energy dissipation and erosion prevention projects under check dams, which is beneficial for improving engineering value and for better serving disaster prevention and reduction efforts. [ABSTRACT FROM AUTHOR]

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It is more difficult to accurately control the cycle fuel mass of a gasoline engine as the injection pressure increases, and the difference in the injection mass flow will become intense due to the machining error of GDI injector structural parameters. In order to guarantee the uniform cycle fuel mass of the GDI injector, this paper investigates the effect of the inlet orifice on the injection mass flow and the sensitivity of inner-flow characteristics in the GDI injector nozzle to the inlet orifice radius by the single factor analysis method. The results show that the local resistance of the injector nozzle will decrease and the discharge coefficient will rise due to the increase in the inlet orifice radius; the sensitivity of cycle fuel mass to the inlet orifice radius is most strong at r = 0.02 mm, and its accuracy should be improved when grinding the chamfer of the nozzle inlet; the sensitivity coefficient of the inlet orifice radius will rise up, and the machining accuracy of the inlet orifice radius should be improved as there is an increase in injection pressure. [ABSTRACT FROM AUTHOR]

Local regulations control the additional runoff produced by urbanization processes. Sustainable urban drainage systems can mitigate the issues associated with increased runoff by employing infiltration basins, detention ponds, wet ponds, and constructed wetlands. Traditionally, the Water Level Pool Routing Method, which relies on an implicit calculation scheme, has been used to calculate outflow hydrographs in reservoirs. In this research, an explicit scheme for the Water Level Pool Routing Method has been developed. The proposed model is applied to a case study where the reservoir has a surface area of 9.12 hectares. The influence of weir width and the discharge coefficient is also analyzed. Additionally, the variation in time step does not significantly affect the response of the proposed model, demonstrating its adequacy as a novel method. The proposed model is compared to the traditional method, yielding similar results in an analyzed ornamental reservoir (low percentage reduction in peak flow). However, a case study with experimental data reveals that the proposed model provides better accuracy than the traditional method. In addition, the proposed model is more efficient as it reduces computational time compared to the implicit scheme (conventional method). Finally, the proposed model is simplified for small watersheds by applying the rational method for computing an inflow hydrograph. [ABSTRACT FROM AUTHOR]

Since complete fluidic sprinklers (CFS) cannot function well in low-pressure environments, dynamic fluidic sprinklers (DFS) were developed to address this issue. In 2021, research in the field and laboratory were conducted to examine how well DFS and CFS performed hydraulically in both indoor and outdoor conditions. In this investigation, a Thiess Clima laser precipitation monitor was used to evaluate the droplet size and velocity distribution of two different types of sprinklers indoors. From the findings, DFS velocities ranged from 0.1 to 4 m/s whereas CFS ranged from 0.1 to 5.3 m/s. The maximum frequency value was obtained at velocities of 1 m/s for each combination. The DFS had a slightly greater discharge coefficient and spray pattern than the CFS. The DFS's maximum spray range was 12.2 m, while the CFS's maximum spray range was 10.8 m, with standard deviations of 1.07 and 1.66, respectively. Under high wind speed conditions, the maximum combined Coefficient of Uniformity (CU) of DFS and CFS were 81.1% and 78%, respectively. For a given pressure and sprinkler spacing, DFS delivered higher CU values than CFS, especially while running at low pressure, demonstrating that DFS offered a more favored water distribution pattern at low pressure. At different distances from the sprinkler, the highest application rates for DFS and CFS were 6.7 mm h-1 at 7 m and 6.5 mm h-1 at 7 m, respectively. A comparison of DFS and CFS under hydraulic performance indicated that DFS had a better performance than CFS. The study can serve as a guide for how to conserve water in sprinkler-irrigated fields. [ABSTRACT FROM AUTHOR]

Background and Objectives: The Voshmgir dam with a height of 21 meters, is one of the oldest dams in the country and is located in Golestan Province. The Voshmgir Dam is built with one main reservoir and three sub-reservoirs with a total initial volume of 96 MCM. However, in the current situation, given the end of the useful life of the dam and the filling of the dam reservoir due to the influx of sediments from numerous floods, it has decreased to 45 MCM. The available topographic maps show that it is not possible to increase the height of the main body of the dam and its side walls, and all the potential of the area has been used for the construction of the dam. Therefore, the only available solution to increase the volume is to increase the overflow's height. To increase the dam height, according to the calculations, a one-meter increase in the height of the dam's spillway, dam has been done. The purpose of this research is to investigate the hydraulics of the flow on the Voshmgir dam spillway with a rubber valve and compare it with sharp-edged, wide-edged, and cylindrical spillways using physical modeling. Materials and Methods: In this research, Anwar's mathematical model, which is the modeling of the upstream part of rubber dams, was tested on a flexible object. Then, the rubber dam with 4 different internal pressures (the ratio of internal pressure to the height of the rubber dam) was made with a rigid body and installed on the main spillway model of the dam. Experiments were conducted in 7 different flow rates between 12.69 and 30.45 liters per second in a concrete channel with a width of one meter and a length of 6 meters in non-submerged and clear water conditions in the water and sediment laboratory of Gorgan University of Agricultural Sciences and Natural Resources. Finally, to take advantage of these studies in the design of rubber dams, various linear and non-linear equations were extracted and presented to estimate the discharge coefficient using SPSS software. Results: The results showed that the hydraulic behavior of the rubber dam is more similar to the broad-crested weir than to the sharp-crested and cylindrical weirs. In all models, the flow coefficient increases with the increase of the hs/P ratio. Additionally, when the internal pressure of the dam increases from 0.5 to 1.3 at a constant hs/p, the discharge coefficient shows an average increase of 19%. Moreover, it has been observed that at a constant Froud number, the discharge coefficient experiences a 13.7% increase as the ratio of internal pressure to the height of the rubber valve increases. Conclusion: Based on the obtained results, Anwar's mathematical model can model the geometry of rubber dams well. The geometry of the rubber valve is a function of its internal pressure and the flow rate changes with the change of the geometry. It can also be concluded that the flow rate, the height of the rubber valve and its internal pressure, the height of the flow relative to the crest of the dam and the height of the upstream water are among the factors affecting the flow hydraulics, including the flow coefficient. [ABSTRACT FROM AUTHOR]

Gas turbine pre-swirl systems has been known to provide smooth cooling air to rotating turbine blades for prevention of thermal damage caused by high turbine inlet temperatures. The performance of the pre-swirl system depends on the shapes of its components, such as the pre-swirl nozzle and receiver hole. This study focused on obtaining the optimal shape of a pre-swirl nozzle that minimizes aerodynamic losses. To determine the optimal shape with minimal design parameters, we modeled the nozzle vane using piecewise cubic functions in three segments to satisfy the given geometric constraints. The optimization results indicated that the nozzle discharge coefficient increased when the second and third segments were positioned closer to the throat area. Even simpler shapes, such as a cubic function in one or two segments with less smooth connections between the segments, were tested for comparison. Although the simplest shape using one segment yielded the best performance, all considered shapes were proposed as candidates for the optimal shape in the general design of the pre-swirl nozzle vane. [ABSTRACT FROM AUTHOR]

This document is a discussion of a research paper that examines the discharge coefficient of symmetrical stepped and triangular labyrinth side weirs in a subcritical flow regime. The authors conducted experiments and numerical simulations to understand how the design of these weirs affects hydraulics and discharge capacity. They found that the discharge coefficient increased with certain design changes, but there were still hydraulic phenomena that impacted the weir's ability to effectively drain water. The discussers suggest the use of antivortex structures to address these concerns and improve discharge efficiency. The research was supported by various funding sources, and the data and models used in the study are available for further exploration. [Extracted from the article]

Plasma confinement and transport in tokamaks play a crucial role in the development of high poloidal beta steady-state operation scenarios. Therefore, it is very important to study the relevant mechanism of internal transport barriers (ITBs), which can help plasmas to obtain better confinement in order to achieve higher fusion gain. This paper mainly introduces the analysis of the characteristics of electron heat transport of discharges with ITB in high β P operation regime in Experimental Advanced Superconducting Tokamak (EAST). Based on the statistical analysis of stable discharges with β P > 1.5, it is found that there is an obvious bifurcation of the normalised electron temperature gradient (ETG) ( R / L T e ) in the range of β P = 2–2.2. Then the discharges of lower β P ( β P < 2, where the value of β P is below the bifurcation threshold) and of higher β P ( β P > 2.2, where the value of β P is above the threshold) were selected for analysis. The diagnostic data provided by Thomson scattering, x-ray crystal spectrometry and charge exchange recombination spectroscopy are used to provide reliable parameter profiles and then combined with the data of external magnetic probe measurements and the polarisation interferometer diagnosis system to fully reconstruct the balance. A relevant plasma current calculation model is used to calculate and analyse the current density profiles and power deposition, and then the transport analysis is carried out. Interestingly, in the higher β P discharges, it is found that the turbulence intensity provided by the CO2 laser collective scattering system gradually decreases and the normalised ETG R / L T e gradually increases. It is also found that the electron heat transport coefficient decreases in the discharge with higher β P and the growth rate of the electron-scale turbulence calculated by transport gyro-Landau fluid (TGLF) is significantly reduced. Meanwhile, similar conclusions are also obtained in the discharges when the β P is further increased. [ABSTRACT FROM AUTHOR]

A high-speed backlight system was adopted to investigate the evolution process of the inside-out-gas (IOG) effervescent atomizer and subsequent influence on spray morphology. The results show that bubble flow and annular flow are the most obvious flow patterns when the liquid flow rate is 20 g/s. During the transition from bubble to annular flow, slug flow occurred at gas–liquid mass ratio (GLR) of 3.2%. The annular flow was observed when the GLR further increased to 6.4%. In particular, when the mixing chamber is in a large bubble flow, an annular flow can still be formed at the orifice for the small exit diameter. For the annular flow, a relatively stable spray cone angle was observed. On the contrary, the slug flow has a greater oscillation for the spray cone angle. It was found that bubble flow in the orifice has little effect on atomization effect. For the spray cone angle, the oscillation in the slug flow is larger. Furthermore, the effects of GLR and liquid injection pressure drop are carefully considered in the empirical formula fitting compared to the widely used empirical formula. The empirical formula of the discharge coefficient of the effervescent atomizer is fitted, which provides fast data support for engineering applications. [ABSTRACT FROM AUTHOR]

The effect of nozzle pressure ratio (NPR) on the starting characteristics of an axisymmetric divergent dual throat nozzle is investigated numerically. The steady and unsteady numerical simulation methods are used to study the internal flow field of the nozzle and variation in the related performance parameters as a function of the nozzle pressure ratio. The results show that for change in the total pressure of the nozzle inlet flow or back pressure under the same nozzle pressure ratio, the flow field structures in the nozzle cavity remains basically the same, and there is a little difference between the unsteady numerical simulation results and the corresponding time-independent numerical simulation results. In addition, the discharge coefficient of the nozzle increases rapidly with the increase of the nozzle pressure ratio, and then changes only slightly when the nozzle pressure ratio reaches a certain value. With increase in the nozzle pressure ratio, the thrust coefficient of the nozzle will oscillate in the initial stage, then gradually decrease, and then slowly increase, and suddenly decrease near the critical nozzle pressure ratio (NPRcr), and then gradually increase. The typical flow field structures in the cavity under the starting and non-starting conditions are presented before and after reaching the critical nozzle pressure ratio at which the thrust coefficient of the nozzle suddenly drops. [ABSTRACT FROM AUTHOR]