https://jhyd.iha.ir/ Journal of Hydraulics en daily 1 Sat, 21 Mar 2026 00:00:00 +0330 Sat, 21 Mar 2026 00:00:00 +0330 https://jhyd.iha.ir/article_240638.html IntroductionOne of the most important issues discussed in the field of reservoir management is the release of accumulated sediments. According to documented reports, 1% of the available volume of reservoirs is lost annually to sedimentation, which can increase to 3% in semi-arid regions. Sedimentation causes undesirable consequences such as increased maintenance costs, inability to control floods, reduced power generation capacity, etc. Various methods have been proposed to manage sediment inflow into the reservoir and removal of accumulated sediment. Among these methods, an innovative VMHS hydrosuction method has significant advantages which consists of the vertical multi-hole pipe connected to a pipeline continued to downstream of the reservoir. In this method, the energy is obtained by the difference in water level between the reservoir and the outlet of the system is used to discharge the water/sediment mixture flow through the holes and drive it to the downstream. The other considerable advantages of this system are the minor loss of the reservoir water, durability and the ease of use as well as environmentally friendliness.In this research, it is attempted to provide quantitative understanding of hydraulic characteristics of flow through inlet, holes and connections of the pipeline system for designers of VMHS.MethodsThis study was conducted at the Hydraulics Laboratory of the College of Agriculture and Natural Resources of the University of Tehran. A physical model consisting of a tank and a hydro-suction pipe system. The system included a perforated vertical suction pipe with various hole configurations and dimensions, designed to evaluate hydraulic behavior for different flow and pressure conditions. Experiments were categorized into three stages to provide sufficient data for estimating longitudinal and local loss coefficients with a no-hole pipe and multi-hole vertical pipe based on flow discharge and pressure measurements. A total of 28 suction pipe types were tested, varying in hole number (1, 2 and 3 holes), position, spacing, and diameter (14.25, 28.5 and 42.75 mm). Dimensional analysis using the Buckingham π method was employed to define key dimensionless parameters influencing the system's flow characteristics.Results and DiscussionsThis study focuses on determining head loss coefficients in a VMHS system across various configurations and flow rates. The first stage involved measuring frictional and minor losses using Bernoulli’s and Darcy-Weisbach equations for different energy head conditions (ΔH1, ΔH2, ΔH3 respectively 1.5, 2 and 2.5m). The experiments encompassed a wide range of flow discharges, and associated Reynolds numbers revealed that all flows were turbulent. Frictional loss coefficients varied based on pipe roughness and Reynolds number, while minor loss coefficients were evaluated at bends, flowmeter, inlet, and globe valves. These coefficients were then averaged and summarized for further use in subsequent stages of the study.In the third stage, the flow was restricted to only pass through pipe holes by sealing the pipe inlet, showing reduced discharge rates that were unaffected by the ΔH. The suction performance improved with increased hole diameter and number, and the discharge coefficient (CD) for each configuration was calculated. Lower CD values indicated smoother flow entry and reduced wall resistance. Notably, “Type 3” pipes with the largest holes showed negative minor loss coefficients (Kh), indicating that perforations served as primary inlets. Hydraulic pressure analyses showed that in high flow discharges, negative pressures developed along the pipe walls due to inlet flow curvature, and averaged pressures were used for analysis when local measurements were unreliable. The influence of hole sizes and layout on inlet pressure was also assessed, indicating minimal effects for smaller diameters.ConclusionIn the first phase of the experiments, energy losses in the hydrosuction system were analyzed, including both friction loss along the pipeline and minor losses from components such as bends, flowmeter, control valve, and the pipe inlet. In the second and third stages, the flow discharge coefficients and minor loss coefficients at the suction pipe holes were calculated using experimental data and hydraulic energy equations. Results showed that negative pressure at the pipe inlet wall is due to flow curvature and compression, and at higher discharges, the averaged inlet pressure becomes negative, with larger hole diameters leading to increased inlet pressure and greater flow contribution from side holes. https://jhyd.iha.ir/article_239795.html In recent decades, increasing drought frequency, declining renewable water resources, and growing agricultural water demand have intensified the need for sustainable water management, particularly in arid and semi-arid regions such as Iran. The agricultural sector, which accounts for over 90% of total water withdrawals in Iran, suffers from low conveyance efficiency and excessive dependence on groundwater abstraction. Traditional irrigation networks, controlled by manual structures such as Amil regulators, often fail to respond to flow fluctuations and result in significant water losses, high energy consumption, and inequitable water distribution among users. These challenges necessitate the adoption of automated and data-driven operation systems. Model Predictive Control (MPC) has recently emerged as an effective technique for improving the hydraulic performance of open-channel systems. However, MPC alone cannot assess the environmental and energy implications of operational decisions. Therefore, integrating MPC with an analytical sustainability framework such as CLEWs (Climate–Land–Energy–Water Systems) provides a comprehensive understanding of the interlink ages between hydraulic, energy, and environmental dimensions. This research aims to develop a coupled MPC–CLEWs framework to quantify the synergies and trade-offs between operational efficiency, energy use, and carbon emissions in an irrigation network.Methodology The study was conducted on the Qazvin irrigation network in northwestern Iran, which covers approximately 59,000 hectares and receives water mainly from the Taleghan Dam. Two operational strategies were modeled: (1) the conventional Amil regulator-based method and (2) a centralized Model Predictive Control (MPC) system. Both methods were simulated under two hydrological scenarios : normal and drought conditions, using a dynamic integrator-delay hydraulic model. Key performance indicators included Water Delivery Adequacy (PA), Energy Consumption (E), and CO₂ Emissions (CE). These indicators were normalized and aggregated into the composite CLEWs Index, defined as:CLEWs = 0.4·Iw + 0.3·(1–Ie) + 0.3·(1–Im),Where Iw, Ie, and Im represent the normalized sub-indices of adequacy, energy, and emissions, respectively. Energy consumption was calculated based on pumping volume, head, and pump efficiency according to Howells et al. (2013). The coupled module was implemented in MATLAB R2023b, allowing automatic integration of the operational outputs (from MPC) into the CLEWs analytical structure. Additionally, a multi-objective sensitivity analysis was conducted by varying the weight of each component to identify trade-offs between water supply adequacy and energy use. Pareto front diagrams were then generated to visualize optimal balance points between performance and sustainability under both operational modes.Results and Discussion The results revealed significant differences between the two operation strategies under both hydrological conditions. In the normal scenario, the average CLEWs Index improved from 0.75 under the Amil operation to 1.00 under MPC, indicating complete system stability and elimination of groundwater dependency. Downstream reaches (7–10), which previously suffered from inadequate supply (CLEWs < 0.75), achieved full adequacy and zero emissions under MPC. Under the drought scenario, the Amil-based system experienced a sharp decline in performance, with the average CLEWs Index dropping to 0.62, driven by increased groundwater pumping and CO₂ emissions. Conversely, MPC maintained a relatively high CLEWs value of 0.88, demonstrating resilience against reduced inflows. The energy demand in the Amil method increased by more than 40% compared to MPC due to inefficient reallocation of flows. Pareto front analysis highlighted that MPC achieves superior trade-offs, minimizing energy consumption while maximizing adequacy and environmental sustainability. In contrast, the Amil regulator showed steep trade-offs between supply reliability and energy costs, reflecting its vulnerability to hydrological variability. The coupled CLEWs framework effectively captured these multi-dimensional interactions, offering a quantitative link between operational decisions and their sustainability outcomes. Overall, the integrated MPC–CLEWs system enhances not only hydraulic stability but also energy efficiency and carbon reduction potential in irrigation management.Conclusion This study introduced a novel coupling between operational control (MPC) and the CLEWs analytical framework to evaluate irrigation sustainability in real time. Results demonstrated that MPC substantially improves water delivery adequacy, reduces energy demand, and minimizes greenhouse gas emissions compared to conventional Amil-based management. The coupled model provides a comprehensive decision-support tool for irrigation managers, enabling the formulation of adaptive strategies under water scarcity. The proposed MPC–CLEWs framework bridges the gap between operational modeling and sustainability assessment, offering a replicable approach for integrated water–energy–environment management. https://jhyd.iha.ir/article_240639.html The behavior of non-Darcy flow in gravel materials depends on the physical characteristics of the aggregate, the fluid properties and the flow characteristics. Non-Darcy flow in inhomogeneous environments also depends on the physical characteristics of each of the components of the environment, and the equivalent Forschheimer coefficients of the entire inhomogeneous environment are a function of the aforementioned coefficients of each of the components of the environment. The present study was conducted in the Hydraulic Laboratory of the University of Zanjan in a channel with a length of 5 meters, a width of 30 centimeters and a height of 30 centimeters for three aggregates: fine, medium and coarse. For this purpose, 90 experiments were conducted at different discharge rates and vertical homogeneous and inhomogeneous conditions. The equivalent Forschheimer coefficients of the vertical inhomogeneous environment were determined by three different methods based on the relationship between velocity and hydraulic gradient. In the first method, by equating the sum of the losses of each component of the medium with the total loss of the inhomogeneous medium, in the second method, by equating the values ​​of the friction force of each component with the total friction force, and the third method, which was estimated as an empirical relationship and has been developed into different relationships. Since Darcy's relationship is valid only in laminar flow, according to the experiments conducted in the present study and the invalidity of Darcy's relationship, the flow is always turbulent. The studies conducted show that the average error of the coefficient a in the first, second, and third methods was 87.32, 87.91, and 48.41 percent, respectively, and the average error of the coefficient b in the first, second, and third methods was 34.78, 32.31, and 33.24 percent, respectively. The average relative error of the hydraulic gradient estimated by the first, second, and third methods will be 8, 8.77, and 5.7 percent, respectively. https://jhyd.iha.ir/article_239796.html The accumulation of large wood (LW) at bridge structures poses a significant flood hazard, yet the critical role of initial log placement in triggering these blockages remains insufficiently quantified. This study provides a systematic experimental investigation into the parameters governing the accumulation probability (AP) at bridge piers and abutments. It focuses on four key domains: (1) initial log placement conditions (release distance, lateral position, and orientation); (2) approach flow conditions; (3) geometric characteristics of the bridge, particularly the varying distance between the pier and abutment; and (4) LW characteristics, including length, diameter, branching, and transport regime (uncongested vs. congested). Results identified the worst-case scenario for LW accumulation around piers and abutments: logs released 1m upstream of the abutment nose, from the channel centerline, and oriented perpendicular to the flow. Furthermore, the analysis reveals that accumulation probability is predominantly a function of approach flow velocity, log length and diameter, and the distance between the pier and abutment. Overall, these findings provide a quantitative, design-oriented basis for estimating LW accumulation risk and for guiding the layout of pier–abutment systems to enhance resilience against wood-laden floods.The experimental program was conducted in a large rectangular flume (14 m length, 1 m width, 0.8 m depth) at Semnan University's Hydraulics Laboratory. The setup featured two circular plexiglass piers (diameter D_p = 0.05 m) and a rectangular abutment positioned 9.45 m downstream in the channel centerline. Three distinct flow conditions were examined, with discharges of 0.016, 0.026, and 0.036 m³/s, corresponding to approach velocities (u_0) of 0.16, 0.26, and 0.36 m/s and Froude numbers (Fr_0) of 0.16, 0.26, and 0.36, respectively. The approach flow depth (h_0) was maintained constant at 0.10 m throughout all experiments. Model large wood elements consisted of smooth natural wooden logs with specific lengths of L_Lw = 0.25, 0.3, 0.35, and 0.40 m and corresponding diameters of d_LW = 0.006, 0.012, and 0.025 m, scaled using a factor of λ = 20 based on field observations from the 2021 flood event in the Sajadrood River, Iran.The experimental methodology employed a novel two-pronged framework. First, critical placement thresholds were identified by testing combinations of key parameters: LW release distances of 1 m, 3 m, and 6 m from the abutment nose; lateral release positions at the left bank (adjacent to the abutment), channel centerline, and right bank; and log position angles of 0°, 45°, and 90° relative to the flow direction. The combination that maximized AP defined the worst-case scenario. Subsequently, this worst-case scenario was utilized to systematically quantify the influence of other governing parameters, including LW characteristics and transport regimes.The results identify a definitive worst-case scenario where logs released 1 m upstream of the abutment, from the channel centerline, with a perpendicular orientation (θ_LW = 90°) demonstrated dramatically increased accumulation probabilities. This configuration showed up to 86% higher AP compared to longer release distances (6 m) and 375% greater probability compared to parallel orientations (0°). The accumulation probability decreased sharply from p = 45% at x_LW = 1 m to p = 25% at x_LW = 3 m, and further to p = 6% at x_LW = 6 m for 25 cm logs at velocity 0.16 m/s. Similarly, for longer logs (L_LW = 40 cm), the probability of accumulation decreased by 61% as release distance increased from 1 m to 6 m.Regarding orientation effects, for a 25 cm log at u_0 = 0.16 m/s, the accumulation probability increased progressively from p = 12% at 0° to p = 40% at 45°, and reached p = 45% at 90°. This probability rose dramatically for longer logs, reaching p = 0.93 for a 40 cm log at the perpendicular orientation. Lateral positioning also proved critical, with the highest accumulation probability consistently occurring at the channel centerline across all tested conditions. At velocity 0.16 m/s, accumulation probability for long logs reached 85% at the centerline, compared to 77% and 75% on the left and right banks, respectively. This distinction became more pronounced at velocity 0.26 m/s, where the difference between the centerline (80%) and the right bank (55%) reached 25 percentage points.Log dimensions significantly influenced accumulation patterns. Longer logs (40 cm) showed dramatically higher accumulation rates than short logs (25 cm), with probability increasing by 365% at velocity 0.16 m/s and surging by 656% at velocity 0.26 m/s. Diameter effects were also substantial, with p = 22% (d_LW = 0.6 cm), 51% (d_LW = 1.2 cm), and 55% (d_LW = 2.5 cm) for L_LW = 25 cm at u_0 = 0.16 m/s. Shape characteristics further modulated accumulation behavior, with branched logs (89%) and coniferous logs (93%) showing significantly higher AP than smooth logs (29%) at low velocity (0.16 m/s), though these differences diminished at higher velocities.Transport regime emerged as another crucial factor, with congested transport resulting in substantially higher AP compared to uncongested conditions. For L_LW = 25 cm, AP increased by an average of 15.5% for congested wood transport, while for L_LW = 40 cm, the value increased by an average of 82%. Under congested transport with L_LW = 40 cm, p ≥ 90%, exhibiting the highest values observed in this study.These findings collectively establish initial log placement as a decisive factor in accumulation initiation, offering novel, quantitative insights for predictive models and the design of safer bridge infrastructure in wood-prone rivers. The research demonstrates that how wood arrives at a structure can be more influential than the wood's dimensions alone, providing crucial information for flood hazard assessment and resilient infrastructure design in river systems susceptible to large wood transport during flood events. https://jhyd.iha.ir/article_239797.html Introduction Spillways and gates serve as flow measurement and water level control structures in both natural and artificial irrigation channels. Ogee spillways, in particular, not only regulate reservoir levels but are also widely used for power generation, irrigation, and flood control. A ogee spillway allows excess reservoir water to flow downstream. However, due to high-velocity flow at the downstream of these structures, hydraulic jumps commonly occur, characterized by sudden transitions from supercritical to subcritical flow, turbulent air entrainment, and energy dissipation.Combined spillway-gate or spillway-culvert systems are designed to enhance hydraulic efficiency and sediment flushing by separating the ogee from the channel bed via gates or culverts. These configurations typically pass higher discharge than simple weirs due to dual flow paths—over the spillway and under the gate. The interaction of these flows significantly increases downstream energy dissipation, reducing scouring risks.Numerous studies have examined the hydraulic performance of various geometries, including sharp-ogeeed, inclined, rectangular, and cylindrical weirs. Research highlights how geometric parameters like gate opening, spillway height, and flow head affect discharge and flow characteristics. Modern research increasingly relies on numerical and experimental methods to investigate hydraulic jumps and two-phase (air-water) flow behavior in such systems, ensuring safe and efficient hydraulic structure designs.Methodology A three-dimensional Computational Fluid Dynamics (CFD) model was developed using FLOW-3D software to simulate flow behavior in a composite hydraulic structure consisting of a ogee ogee spillway integrated with a culvert under free-flow conditions. The FLOW-3D code solves Reynolds-Averaged Navier-Stokes (RANS) equations using the finite volume method, incorporating VOF and FAVOR techniques for tracking free surfaces and representing solid boundaries, respectively. Turbulence was modeled using four approaches: standard k-ε, RNG, LES, and k-ω, with calibration based on experimental data from Toozandehjani & Kashefipour (2012, 2013). The physical model consisted of a 12-meter-long rectangular flume. For numerical efficiency, the model domain was shortened to 5 meters.Experimental results identified a 45° outlet angle as optimal for energy dissipation. Numerical simulations evaluated the performance of different turbulence models, showing that k-ω achieved the best agreement with experimental data, with R² = 0.97 and RMSE = 0.0112. Mesh independence analysis confirmed that a cell size of 0.0007 m provided stable velocity profiles. Simulations also investigated the influence of culvert elevation within the spillway body across four configurations. The model reached steady-state flow after 72 seconds, validating its temporal convergence.Finally, variations in culvert positioning significantly affected flow patterns and energy dissipation. This study highlights the effectiveness of FLOW-3D in simulating complex free-surface flows and optimizing hydraulic structure designs through combined experimental and numerical analysis.Results and Discussion This study numerically investigates flow behavior in a ogee overflow spillway equipped with culverts under free flow conditions, focusing on velocity patterns, Froude number variations, and total energy loss.Velocity Distribution:Two-dimensional velocity vectors and vertical velocity profiles before and after the hydraulic jump were analyzed for minimum and maximum discharges. Vortex formation and air–water mixing were observed in the hydraulic jump region, particularly when culverts were present. Two primary vortices were identified: one near the culvert outlet close to the bed and another above the jet stream. Unlike the classical hydraulic jump, the velocity profiles with culverts showed the maximum velocity occurring above the bed, indicating altered jet behavior due to culvert interactions. When culverts were placed at 50% and 75% of the spillway height, the surface jet velocity was higher than the culvert jet, causing more concentrated downstream flow. Dual-culvert configurations reduced peak velocity by 40% and shifted its location 14% higher compared to the spillway without culverts.Froude Number Analysis:The longitudinal profile of the Froude number showed that culvert placement significantly influenced flow regimes. For low discharge, the flow remained subcritical longer when culverts were elevated (e.g., at 75% height). Dual-culvert setups caused submerged hydraulic jumps near the toe of the spillway. At high discharges, subcritical flow extended further downstream across all culvert placements. The greatest Froude number reduction occurred when culverts were placed at the base or used in pairs, reducing subcritical zones by up to 25% of the spillway slope.Energy Loss:Energy loss contours indicated that the presence of culverts shifted energy dissipation toward the spillway body, weakening the hydraulic jump and reducing its length. At low discharges, energy loss was more pronounced due to the dominant culvert flow. As discharge increased, energy losses decreased due to reduced upstream-downstream water level differences. Culvert-spillway systems also reduced the secondary depth of hydraulic jumps, further enhancing energy dissipation efficiency.Conclusion The hydrodynamics of flow downstream of ogee spillway–culvert structures were investigated numerically using a series of laboratory-based studies under various culvert placement scenarios. The hydraulic assessment of the proposed spillway–culvert configuration under free flow conditions indicated that the structure possesses a higher discharge capacity compared to a conventional ogee spillway. Variations in turbulent kinetic energy at different flow rates revealed that the location of maximum energy dissipation shifts toward the toe of the spillway as the culvert is positioned closer to it. This shift in energy dissipation results in a reduced energy loss rate, thereby increasing the potential for erosion. It was also found that, at peak discharges, the formation of dual vortices in the dual-culvert configuration enhances energy dissipation, making the proposed structure more effective and potentially suitable as a fish passage route. https://jhyd.iha.ir/article_240637.html The study of the characteristics of waves generated by the collapse of rock masses in dam reservoir walls is of great importance. Factors influencing the wave flow over the body and crest of a dam include the length, height, and speed of the waves generated by the collapse of rock masses due to various factors. For this reason, in the present study, the wave parameters mentioned were measured for the first time using laser surface profiling in a pool with dimensions of 12.5 meters in length, 6.5 meters in width, and 1 meter in height at Zanjan University, Iran, due to the collapse of a mass in this reservoir. The experiments were conducted using a sliding mass weighing 200 kilograms and for a water depth of 75 cm. The laser setup consisted of two arrays (with a 76 cm distance between them), where each array contained 15 lasers arranged in pairs facing each other. Using these lasers and a DSLR camera, after the mass was dropped onto the inclined surface, the variations in wave height over time were recorded. Then, using the recorded images and laser surface profiling, the wave height was first measured, and then, using the changes in height, the wavelength was calculated. Following this, by measuring the time it took for the wave to pass in front of the two laser arrays, the wave speed was also obtained. It is worth noting that the camera's frame rate was 0.04 seconds. The experimental results indicate that the measured wave speed using the proposed method was 2.67 meters per second, while the wave speed calculated using the wave speed formula (C=√gh) was 2.71 meters per second, showing a difference of 1.48%, which demonstrates the high accuracy of the proposed measurement method.Keywords : Mass fall,impact waves,wavelength,wave speed,laser surface profilometry https://jhyd.iha.ir/article_240640.html IntroductionFlow measurement in an open channel is a fundamental principle in the advanced management and regulation of irrigation networks. Currently, the principle of critical flow conditions in an open channel is used in the design of flow measurement flumes. A method for creating a flow cross-section, known as a control section, has been implemented, allowing for a definite correlation between flow depth and discharge to be expressed. The Venturi flume was a pioneer in recognizing the effect of local constriction in a channel on the pressure and velocity distribution (Hager 1985; Ferro 2002). Flumes that operate by locally changing the channel width are common, and in various European countries, the throat flume, characterized by a gradual change in width, is used. On the contrary, the Parshall flume, known as a throatless flume, is widely used in Anglo-Saxon countries (Blaisdell 1994; Parshall 1926). Hager (1988) used a moving circular flume to measure flow through channels, which consists of a circular column positioned vertically in the center of a pipe to achieve the required constriction. Hager (1986) and Samani and Magallanez (1993) recommended quantifying flow rate by integrating a circular column into a trapezoidal channel. Samani et al. (1991) conducted laboratory studies to investigate the hydraulic properties of various circular flumes. A review of the research background shows that the flumes used are either partial flumes or flumes with a central baffle. In partial flumes, part of the cross-section is reduced, and sometimes they have a bottom protrusion. In central baffle flumes, the baffle is also non-submerged, and in addition to increasing the possibility of blockage, the high-speed flow passing through both sides of the structure has high shear stress on both sides. In the flume proposed in this study, the goal is to utilize the entire cross-section, especially at high discharges, and, additionally, the flow submerges the baffles. One of the hypotheses of this study is that due to the use of multiple baffles, the shear stress created downstream of the baffles is likely to be reduced compared to flumes with single central baffles. This is especially important in erodible beds. The goal of this study is to conduct a hydraulic evaluation of a new flume with a structure consisting of cylindrical baffles. For this purpose, the effect of the percentage of obstruction (or diameter), and the effect of the height of the cylinders at different discharges have been tested. Additionally, using dimensional analysis, the appropriate discharge relationship for this flume has been extracted, and this relationship has been determined through nonlinear multivariate regression.MethodologyThe modeling of this research will be carried out in a rectangular flume with a length, width, and height of 15, 0.8, and 0.6 meters, respectively, in the hydraulic laboratory of Shahid Chamran University of Ahvaz. In general, 11 models were built with geometric variables, including different heights (P) and diameters (D). Hydraulic variables also include different discharges. At each discharge in free-flow conditions, the downstream valve is fully open. Considering the hydraulic variables, a total of 190 experiments were conducted for free conditions.Results and discussionAs the height of the baffles increases, the structures are submerged at a higher discharge. Additionally, as the diameter of the baffles increases, due to the increased obstruction, the structures are submerged at a lower discharge rate. Determining the threshold discharge of the obstruction submersion is especially important in waterways that include debris flows, such as tree branches or debris. Because this debris can obstruct the structure, it can also lead to errors in the discharge estimate. In this type of flume, the relationship between discharge and eschel is a logarithmic function. Given that the obstruction of the structure increases with the diameter of the baffles, for a specific discharge, the eschel value is higher for baffles with larger diameters. The results show that for a given upstream depth, the discharge index value decreases with increasing height and increasing obstruction. With the same reasoning used for the height of the baffles, increasing the diameter and increasing obstruction, for a given upstream height, the discharge index is higher for smaller diameter baffles. Based on the dimensionless relationship presented in the dimensional analysis section, as well as the laboratory data, an empirical relationship derived from nonlinear multivariate regression has been established. This relationship has been extracted using SPSS 16 software. For this purpose, the laboratory data were divided into two categories: training data (75% of the data) and calibration data (25% of the data). The training data was used to extract the relationship, and the calibration data was used to evaluate the accuracy of the extracted relationship.ConclusionThis study experimentally investigated the hydraulic performance of a flume with cylindrical baffles, focusing on how baffle height and diameter affect flow under free conditions. Results show that discharge changes logarithmically with these variables. Reducing the height or increasing the diameter of the baffles causes the flume to become submerged at lower discharges. Also, increasing the height and diameter of baffles reduces the discharge index due to greater flow obstruction. An empirical formula for the discharge index was developed using dimensional analysis and nonlinear regression, achieving high accuracy (R² = 0.90 for training data and 0.96 for calibration data) and a relative error of approximately 9% for the calibration data. https://jhyd.iha.ir/article_240643.html Title: A Monte Carlo-LSTM Framework for Realistic Assessment and Predictive Management of Urban Canal Dredginga) Keywords Dredging, Uncertainty Quantification, Monte Carlo Simulation, LSTM, Predictive Maintenance.b) IntroductionFlood-control canals are key infrastructures for protecting urban and agricultural communities. Maintaining their hydraulic capacity requires dredging, a continuous, costly, and essential maintenance activity. Traditionally, the effectiveness of dredging is evaluated retrospectively; judgment on a project's success is made after its completion based on hydrographic data and observed performance. This approach has inherent limitations when dealing with dynamic systems affected by human activities. This reactive "dredge-and-see" cycle is inherently inefficient and risky, focusing on past performance rather than future needs.This weakness presents a significant opportunity to transition from a reactive management model to a strategic, predictive framework. This transition requires confronting a fundamental technical challenge: uncertainty. Deterministic hydraulic models provide a misleading picture of precision, as real-world systems face uncertainties from parametric sources (e.g., Manning's roughness coefficient), input data errors, and structural model simplifications. To manage this, probabilistic methods like Monte Carlo simulation have emerged as standard tools, allowing engineers to generate a probability distribution of possible outcomes instead of a single deterministic output. While Monte Carlo can assess uncertainty for a given scenario, it cannot forecast future scenarios. This is the domain of data-driven predictive modeling. Deep learning models, particularly Long Short-Term Memory (LSTM) networks, have shown an extraordinary ability to forecast complex time series, such as river flow and water levels, and now provide reliable predictive tools. Despite the parallel maturation of Monte Carlo methods and deep learning, a significant research gap exists in their integrated application to dredging evaluation. This paper fills this gap by presenting an innovative framework that links these two domains, transforming dredging assessment from a passive, historical exercise into an active, strategic, and forward-looking management tool.c) MethodologyThis study was conducted on the Abu Dhar canal in Tehran, Iran, a key component of the city's urban runoff network. Field data, including hydraulic and geometric parameters, were collected before and after a dredging operation on July 9, 2023. Water levels were continuously recorded at 15-minute intervals using ultrasonic sensors, while flow velocity and cross-sectional dimensions were measured using a current meter and surveying operations, respectively.The methodological framework consisted of three main stages:1. Deterministic Baseline Calculation: First, the classical Manning's equation was used with field data to calculate the initial, deterministic values for Manning's 'n' before and after dredging. This calculation yielded a baseline improvement of 4.47% and provided the mean values (μ) for the subsequent probabilistic analysis.2. Probabilistic Uncertainty Analysis: A Monte Carlo simulation framework was implemented to quantify the uncertainty surrounding this baseline value. Key inputs—flow velocity (V) and a geometric factor (K)—were modeled as random variables with normal distributions, assuming relative uncertainties of 5% and 2%, respectively. The simulation was run for 50,000 iterations to generate a full probability distribution of the percentage reduction in Manning's 'n'.3. Time-Series Forecasting (Proof of Concept): To demonstrate the feasibility of predictive management, an LSTM network was developed. Field-collected 24-hour water-level time series data (as described in the main text) was utilized. The data was normalized using a MinMaxScaler, and sequences were created using a look-back window of 8 time-steps (2 hours) to predict the next step. The LSTM model, consisting of one LSTM layer (50 units) and one Dense output layer, was trained for 50 epochs using the 'adam' optimizer. Its performance was evaluated using the Root Mean Squared Error (RMSE) on unseen test data.d) Results and DiscussionThe Monte Carlo analysis revealed that while the mean reduction in Manning's 'n' was 4.47%, the 95% confidence interval was exceptionally wide, spanning from -9.66% to +17.12%. This finding is critical, as it exposes the "illusion of certainty" in traditional assessments. It demonstrates that while the project was likely beneficial on average, the measurement uncertainty is so significant that a wide range of outcomes, including no improvement, cannot be statistically ruled out. The resulting probability distribution (visualized in Figure 4) highlights the inherent risk and variability that are ignored by deterministic approaches. This probabilistic view provides a more honest and managerially useful assessment of the project's risk profile. On the predictive front, the LSTM model demonstrated high efficacy. The final evaluation on the test set yielded an RMSE of only 0.032 meters (3.2 cm). This high level of accuracy confirms the model's potential for operational applications. The model's predictions (visualized in Figure 8) confirm this accuracy, showing the forecasted data closely tracking the complex fluctuations of the real-world time series. This successful proof of concept illustrates a paradigm shift from reactive maintenance to proactive, data-driven management. It opens the door for developing real-time flood warning systems and "Digital Twins" of urban water infrastructure. In synthesis, this study's probabilistic analysis offers a realistic "hindcast" of past actions, while the predictive model provides a powerful "forecast" for future management. https://jhyd.iha.ir/article_240642.html Application of SPM for estimating the velocity index in geometric channelsExtended AbstractIntroductionAccurate flow measurement in open channels is essential for applications such as flood risk assessment, hydropower generation, water resource management, and hydraulic modeling. Traditional in-situ discharge measurements using electromagnetic or mechanical instruments are labor-intensive, costly, and potentially hazardous under high-flow conditions. As a result, surface velocity-based methods, including radar and image velocimetry, have become increasingly popular for non-contact discharge estimation. A critical step in these methods is converting surface velocity (us) to depth-averaged velocity (Ud), typically using the velocity coefficient α. Although many studies report average α values ranging from 0.62 to 0.92 depending on bed roughness, flow depth, and channel geometry, a comprehensive understanding of α variation across geometric channels remains limited. Most existing approaches consider α as a constant, which may introduce significant error, especially in non-uniform or shallow flows. This study aims to address this gap by applying the Single Point Method (SPM), introduced by Maghrebi (2003), to quantify the variation of α across the free surface of geometric channels. Additionally, the study examines the relationship between α variations and isovel contours, and compares SPM results with previous empirical and experimental findings.Methodology The core concept of the velocity index α is rooted in establishing a functional relationship between the depth-averaged velocity (Ud) and a single-point measurement, typically the surface velocity (us). In this study, a power-law vertical velocity distribution is assumed to represent flow behavior, consistent with experimental observations and theoretical models. The Single Point Method (SPM) provides a semi-analytical approach to estimate point velocities within the channel cross-section based on boundary effects. Derived from analogies with the Biot–Savart law in electromagnetism, the method computes local velocities using an integral formulation that considers the geometry of the wetted perimeter, the relative roughness, and shear velocity parameters. A constant exponent m=7 is used in the velocity profile to model turbulent open-channel flow over smooth boundaries. To apply the SPM, each channel section (rectangular, trapezoidal, or triangular) is discretized into vertical strips, and point velocities at the free surface are computed at discrete locations. Under each surface point, a vertical band is analyzed to compute the depth-averaged velocity using numerical integration of the power-law profile. The local α at each surface point is then calculated as the ratio Ud/us. To obtain the overall α for the entire section, a discharge-weighted averaging approach is used. This methodology was implemented for multiple geometric configurations (varying B/H and side slope m) and validated by comparison with published data.Results and DiscussionThe SPM was applied to three types of channel cross-sections: rectangular (n=0), trapezoidal, and triangular (B=0), over a wide range of width-to-depth ratios (B/H) and side slopes (n). Isovel contours (lines of constant dimensionless velocity λ) were plotted to visualize the velocity distribution and examine the location of maximum flow velocities. In rectangular channels, increasing the B/H ratio shifts the location of maximum velocity toward the free surface, while in narrow sections (low B/H), it moves deeper into the cross-section. This pattern directly affects α: in wide channels, local α values near the centerline decrease, while in narrow channels, they increase. For trapezoidal channels, similar trends were observed. However, additional variations in α appeared near the sloped walls due to decreasing effective strip height and declining surface velocity, us. Triangular sections exhibited a strong concentration of α around the central region, with lower values at the deepest point. Average α values obtained for each cross-section type are: 0.73 to 1.04 for rectangular section (increasing in narrower channels), 0.71 to 0.88 for trapezoidal section (depending on B/H and n), and 0.78 to 0.88 for triangular section (decreasing with side slope, n). The validation of discharge results using the cross-sectional α-coefficient against the experimental discharge and the measured surface velocity indicates a relative error below 5% and demonstrates a good agreement of the results. Furthermore, these results were consistent with previous studies (e.g., Fujita 2018; Welber et al. 2016), where α values in artificial channels typically ranged from 0.8 to 0.9. The maximum relative error between SPM-based α and literature values was under 12.7%. Notably, the study confirms that α varies significantly across the free surface and is sensitive to channel geometry, highlighting the limitation of assuming a constant α. Two empirical equations were also proposed to estimate α based on geometric parameters with a maximum error of 2.18%.ConclusionThis study demonstrated that the Single Point Method (SPM) can effectively model surface and depth-averaged velocities in geometric channels and accurately estimate both local and global α coefficients. The results emphasize that α is not a constant and exhibits systematic variation across the free surface depending on the channel geometry. The proposed method offers a cost-effective, non-contact alternative for discharge estimation and improves upon existing empirical assumptions. The findings validate the applicability of SPM for hydraulic analysis in artificial channels and support its extension to real-world flow conditions with complex geometries. https://jhyd.iha.ir/article_240644.html Introduction Measuring, recording, and monitoring water flow in the waterways and irrigation and drainage networks is essential for demand-driven volumetric water delivery. Measuring fluids in open channels is more complex than in closed channels because the uncertainty and degree of freedom of flow are greater in open channels. On the other hand, these irrigation systems require low-cost and accurate measuring instruments or structures. Due to their economic efficiency and low uncertainty, flow measurement structures based on the discharge-scale relationship, such as weirs and flumes, are used. Among them, measuring flumes are one of the basic structures in irrigation networks, which, if constructed correctly, have high accuracy. In this study, the submergence threshold and discharge under submerged conditions were tested in a porous cut-throat flume with triangular and trapezoidal throats. The main goal of this study is to obtain an empirical relationship for finding the submergence threshold and also the throughflow under submerged conditions of a cut-throat flume with a gabion structure.Methodology The experiments were conducted in the hydraulic laboratory of the Water Engineering Department of the Faculty of Agriculture, Razi University. For this purpose, a laboratory channel with a rectangular cross-section of 37 cm wide, 60 cm high, and 6 m long was used. To construct the gabion structures used in this study, 6 mm rebar was used, and the structures were filled with aggregates with different porosity percentages and the aggregates were divided into three different porosity percentages. The flumes were constructed with 3 different flume heights, 4 different throat openings, and 3 different porosity percentages. Finally, in this study, 36 measurement structures and 330 experiments under submergence threshold conditions and 880 experiments under submerged flow conditions were used to calibrate the mathematical relationship and examine the effect of variables on flow. To estimate the appropriate mathematical relationship, first, appropriate dimensionless groups were obtained between the variables used using Buckingham's theory, and then, using nonlinear regression and Gene Expression Programming methods, mathematical relationships were obtained with appropriate accuracy to estimate the submergence threshold and submerged flow of the flume.Results and Discussion The results indicate that for a constant discharge, if the opening and porosity of the materials are constant, with increasing flume height, the depth of submergence threshold increases by 5 to 28 percent. If the height and porosity of the flume materials are considered constant, with increasing the throat opening at a constant discharge, the structure is submerged faster and the depth of submergence threshold decreases, which varies from 9 to 26 percent. A flume with greater height and lower porosity and opening percentage has a higher submergence threshold, and as a result, is more resistant to submergence and submerges more slowly. On the other hand, by increasing the flume opening for a constant water depth, the value of dimensionless discharge increases between 9 and 66 percent. This is observed with an increase in the porosity percentage and a decrease in the height of the structure. In this condition, a larger flow rate passes through the flume and a larger flow rate range can be measured. Finally, by considering the dimensionless groups obtained by dimensional analysis, mathematical relations for estimating the depth of the flume submergence threshold and relations for estimating the flow discharge under submergence conditions were obtained between the dimensionless groups using two softwares: SPSS 26 and GeneXproTools 5.0. These relations were separated in order to increase the measurement accuracy for flumes with triangular and trapezoidal throats.ConclusionThis study showed that the use of a porous flume helps to widen the range of flow measurement under submerged conditions and confirms the use of this type of flume in submerged flow conditions. On the other hand, by increasing the size of the flume, can be prevented from becoming submerged. However, it is worth noting that the use of gabion structures in alluvial waterways with high sediment concentrations may cause the flume pores to fill and the porosity of the structure to change over time. https://jhyd.iha.ir/article_240645.html IntroductionSediment flushing is a significant phenomenon in hydraulic engineering, influencing both river morphology and environmental stability downstream of diversion dam. Experimental studies in this domain are often costly and time-consuming. Consequently, numerical modeling has emerged as a practical and efficient method for analyzing sediment transport processes. This study focuses on modeling the impact of varying channel slopes and gate openings on sediment bed evolution in sediment slice canals of diversion dams using Flow-3D software. MethodologyThe study utilized experimental data from a laboratory flume at the University of Tehran to calibrate the numerical model. The flume, measuring 2.5 m in length, 0.16 m in width, and 0.35 m in height, featured a centrally positioned vertical sluice gate. Sediment material consisted of uniform sand particles with a mean diameter of 3.5 mm. Simulations were performed using the Volume of Fluid (VOF) method in Flow-3D, applying different gate openings (25%, 50%, 100%) and channel slopes (5%, 10%, 15%). Three turbulence models (RNG, k-ε, and LES) were tested, and the RNG model was selected due to its better agreement with experimental results.Results and DiscussionSimulation results revealed that reduced gate openings led to increased scour depth and more pronounced formation of sediment mounds downstream. The sediment bed profile exhibited minimal variation beyond 70% gate opening. Moreover, increasing the channel slope resulted in greater scour depth near the gate and sequential sediment mound formation further downstream. The RNG turbulence model achieved a calibration error of only 3.4%, outperforming the other models. Temporal analysis indicated that sediment transport and profile formation occurred rapidly after gate opening, but profile changes were less significant beyond 0.6 seconds, suggesting that time was a secondary factor compared to slope and gate opening.ConclusionThe study demonstrates that numerical modeling using Flow-3D with the RNG turbulence model provides a reliable approach for simulating sediment bed evolution downstream of sediment flushing structures. Gate opening and channel slope significantly influence the depth and pattern of sediment scour. For gate openings exceeding 70%, further increases have negligible effects. These findings can inform future designs of sediment flushing systems and support the development of optimized hydraulic structures in irrigation and water distribution networks. https://jhyd.iha.ir/article_240646.html IntroductionIn this research, a comprehensive laboratory investigation of the combined weir with a bottom gate was conducted to examine its performance under varying hydraulic conditions. This type of structure is significant in hydraulics and water management as it combines the benefits of both a weir and a gate, by providing controlled flow regulation while minimizing hydraulic losses.MethodologyThe experiments related to this research were carried out in the hydraulic laboratory of the Faculty of Agriculture at the University of Birjand. The study was performed in a rectangular channel measuring 10 meters in length, 0.5 meters in height, and 0.3 meters in width. To assess and calculate the flow coefficient, the experiments were conducted under two distinct configurations: (1) at constant Gate openings with varying flow rates, and (2) at constant flow rates with different Gate openings. These experiments were executed at two slopes of 0.002 and 0.004, allowing for a detailed analysis of how slope influences flow characteristics.Results and DiscussionThe results of the present study indicated that as the dimensionless parameter Y/D (the height of water on the Gate compared to the height of the channel) increased, the discharge coefficient exhibited a downward trend. Conversely, a decrease in Y/D led to an increase in the discharge coefficient, approaching a value of 0.76. Furthermore, the increase in the dimensionless parameter H_g/D corresponded to a rise in the flow coefficient, which remained within the range of C_T≤0.72. Notably, variations in the slope of the channel floor did not produce significant changes in the discharge coefficient of the structure, suggesting that other factors may play a more critical role in achieving optimal hydraulic performance.ConclusionComparing the findings of the present research with existing studies by other scholars in this area reveals a commendable consistency in results. This alignment underscores the validity of the current research methodology and findings, indicating that the combined weir with a bottom gate operates efficiently under the tested conditions. The insights gained from this study contribute to the ongoing discourse on hydraulic structure optimization in water resource management. https://jhyd.iha.ir/article_241097.html IntroductionThe growing scarcity of freshwater resources—driven by population growth and rising demand—has intensified the need for rigorous analysis and optimization of urban water distribution networks (WDNs). Flow control valves play a pivotal role in ensuring equitable water distribution across such networks. Atashparvar et al. (2019) designed and experimentally evaluated flow control valves with nominal flow rates of 5 and 10 L/s. Using dimensional analysis, they investigated the flow behavior through a cylindrical orifice and found that the actual discharge consistently fell below the design flow rate, highlighting the influence of hydraulic losses and geometric constraints.Water extraction patterns at consumer endpoints significantly affect network performance. In residential complexes, rapid bulk withdrawal—typically for filling elevated or ground-level storage tanks—often results in transient, high-intensity demand surges. These surges induce substantial pressure drops elsewhere in the network, particularly during peak usage periods. Building upon prior research, the primary innovation of this study lies in the implementation of an automatic flow-stabilizing valve, adapted from the design principles of Bijankhan et al. (2025), to regulate maximum inflow at high-demand nodes. Critically, this approach aims to enhance upstream network pressure without altering end-user consumption behavior—achieved through the strategic sizing and deployment of flow-stabilizing valves.MethodologyFlow measurement was conducted with two objectives: (i) to characterize the demand pattern at a selected node downstream of the water source, and (ii) to inform the design and evaluate the performance of the automatic flow-stabilizing valve. Based on a site suitability assessment and alignment with the project scope, the water supply system of Imam Khomeini International University (IKIU) was selected as the case study.An ultrasonic flowmeter—comprising two clamp-on transducers mounted on the pump discharge pipe—was deployed to monitor instantaneous flow rates. Concurrently, an ultrasonic level sensor was custom-assembled and installed inside the main storage tank to track water volume dynamics (i.e., storage vs. drawdown phases). Data from both sensors were logged via microcontroller-based acquisition systems, with the entire instrumentation housed in a weatherproof enclosure for field deployment.Results and DiscussionValve performance was first validated in the hydraulic laboratory at IKIU. Prototype automatic flow-stabilizing valves were fabricated with nominal capacities of 2 and 4 L/s, respectively. These were subsequently installed on the municipal supply line feeding the university’s potable water reservoir.All comparative analyses were conducted using operational data recorded on Sunday, 3 March 2024. Under uncontrolled inflow (baseline scenario), reservoir levels remained relatively stable. In contrast, with the 4 L/s automatic valve in operation (indicated by the blue circle in time-series plots), a progressive deficit emerged—peaking at ~3:00 PM due to sustained high demand—and reached a maximum drawdown of 40 cm by midnight, representing a 10 cm increase (from 30 cm to 40 cm) over 24 hours. The valve was activated at 12:00 PM on 3 March 2024 and remained operational until 6 March 2024. Over this 3.5-day period, the cumulative reservoir deficit stabilized at ~35 cm, equivalent to a volume loss of approximately 150,000 L.Pipeline pressure on the municipal supply main was monitored under three conditions:Uncontrolled inflow: Near-zero inlet pressure (~0 m), indicating gravity-driven, high-flow, low-pressure entry.Daily flow control (4 L/s setpoint): Inlet pressure rose to ~3.6 m.Weekly flow control (2 L/s setpoint): Pressure further increased to ~7.0 m.Notably, these pressure gains were achieved without detectable changes in campus-wide water consumption, confirming that pressure recovery resulted solely from inflow regulation—not demand reduction.ConclusionsBased on measured demand profiles, the peak average hourly flow rate was calculated as 3.99 L/s. Accordingly, automatic flow-stabilizing valves rated at 4 L/s (for daily control) and 2 L/s (for extended, conservative regulation) were deployed.While the 4 L/s configuration led to a gradual reservoir deficit (~35 cm/150,000 L over 3.5 days), switching to the 2 L/s regime on Friday enabled an inflow of ~164,000 L—sufficient to fully offset the accumulated deficit. This demonstrates the system’s ability to shift inflow temporally: suppressing intake during peak periods and enabling reservoir replenishment during off-peak hours.Critically, flow regulation alone—without infrastructure upgrades or demand-side interventions—yielded a 7-meter increase in municipal pipeline pressure (from ~0 m to 7 m) under the 2 L/s scenario. This underscores the efficacy of smart inflow management as a low-cost, high-impact strategy for improving hydraulic resilience in urban water networks.