انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Experimental evaluation of the hydraulic characteristics of VMHS pipeline ارزیابی آزمایشگاهی خصوصیات هیدرولیکی خط لوله سیستم هیدروساکشن VMHS 1 21 240638 10.30482/jhyd.2025.523035.1734 FA سروناز حسینی غفاری دانشکده عمران، دانشکدگان فنی دانشگاه تهران 0000-0003-1611-2907 پیمان بدیعی دانشکده عمران پردیس فنی دانشگاه تهران 0000-0001-6636-7612 صلاح کوچک زاده دانشکده فناوری کشاورزی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران 0000-0002-3752-943X Journal Article 2025 05 18 Introduction One 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. Methods This 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 Discussions This 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. Conclusion In 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. چکیده - یکی از چالش‌های مهم عصر حاضر در زمینه مدیریت منابع آبی، تخلیه رسوبات تجمع یافته در مخازن سدها است. انباشت رسوبات باعث تبعات نامطلوب زیادی به لحاظ هزینه‌های احیاء مخازن و از دست رفتن کارایی تجهیزات جانبی سد از جمله توان تولید برق، مدیریت سیلاب و غیره می‌شود. بنابراین، بکارگیری روش‌های کارامد برای کنترل رسوبات و تخلیه آن‌ها بسیار ضروری است. در میان روش‌های ارائه شده، روش هیدروساکشن (VMHS) به عنوان یکی از راهکارهای نوین موثر با بازدهی مناسب در تخلیه رسوبات به شمار می‌رود که در دو دهه اخیر مورد توجه محققین و مهندسین علم هیدرولیک قرار گرفته است. در این تحقیق به بررسی بیشتر این روش اهتمام شده است تا با شناخت بهتر از عملکرد و خصوصیات آن، موجب ارتقاء طراحی و افزایش بهره‌وری سیستم گردد. این تحقیق در شرایط آزمایشگاهی و با استفاده از انواع لوله‌های مکش بدون و با سوراخ‌های مکنده با انواع قطرها و آرایش متنوع تحت سه اختلاف تراز تامین کننده انرژی سیستم استفاده شد و با کمک ابزارهای اندازه‌گیری دقیق، دبی و فشار جریان بررسی و تحلیل شد. در نهایت، با کمک این داده‌ها و روابط تحلیلی تمامی افت‌های طولی و موضعی موجود در سیستم براورد شد. همچنین، ضرایب دبی جریان و افت موضعی در سوراخ‌های لوله مکش محاسبه و به بررسی دقیق فشار در دهانه لوله و اندرکنش آن با عملکرد سوراخ ها در انتقال جریان به درون سیستم پرداخته شد.

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انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Experimental Study of the Equivalent Coefficients of the Forschheimer Equation in Vertical non-homogeneous Media of non-Darcy Flow in Gravel Materials بررسی آزمایشگاهی ضرایب معادل رابطه فورشهایمر در محیط غیرهمگن عمودی جریان غیردارسی در مصالح سنگریزه‌ای 23 38 240639 10.30482/jhyd.2025.524010.1735 FA حمید عزیزخانی ابهر خیابان 17 شهریور پلاک9 0009-0004-8731-9299 جلال بازرگان زنجان دانشگاه زنجان 0000-0002-6352-8422 عاطفه صدری دانشگاه آزاد ابهر Journal Article 2025 05 19 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. رفتار جریان غیردارسی درون مصالح سنگریزه‌ای به مشخصات فیزیکی سنگدانه، خواص سیال و ویژگی‌های جریان بستگی دارد. جریان غیردارسی درون محیط‌های غیرهمگن نیز به مشخصات فیزیکی هر یک از اجزاء تشکیل دهنده محیط مذکور وابسته بوده و ضرایب رابطه فورشهایمر معادل کل محیط غیرهمگن، تابعی از ضرایب مذکور هر یک از اجزاء محیط می‌باشد. پژوهش حاضر در آزمایشگاه هیدرولیک دانشگاه زنجان در کانالی به طول ۵ متر و عرض ۳۰ سانتی متر و ارتفاع ۳۰ سانتی‌متر برای سه دانه بندی ریز،متوسط ودرشت سنگدانه‌هاانجام شده است. برای این منظور آزمایشات به تعداد 90 مورد در دبی های مختلف و شرایط همگن وغیرهمگن عمودی انجام شده است.روابط ضرایب معادل فورشهایمر محیط غیرهمگن عمودی ازسه روش مختلف برپایه رابطه بین سرعت وگرادیان هیدرولیکی تعیین شده است.درروش اول بامساوی قراردادن مجموع افت‌های هریک ازاجزای محیط باکل افت محیط غیرهمگن،درروش دوم با مساوی قرار دادن مقادیر نیروی اصطکاک هر یک از اجزا با کل نیروی اصطکاک و روش سوم که به صورت رابطه تجربی برآوردگردید و به روابط متفاوتی توسعه داده شده است. ازآنجاکه رابطه دارسی فقط درجریان آرام اعتبار دارد، در نتیجه طبق آزمایشات انجام شده درپژوهش حاضر وعدم اعتبار رابطه دارسی،جریان همواره آشفته می باشد. بررسی‌های انجام شده نشان می‌دهدکه میانگین خطای ضریب a در روش‌های اول، دوم وسوم به ترتیب 32/87، 91/87 و 41/48 درصد ومیانگین خطای ضریب bدر روش‌های اول،دوم و سوم به ترتیب 78/34، 31/32 و 24/33 درصد بوده است. میانگین خطای نسبی گرادیان هیدرولیکی برآوردشده باروش‌های اول،دوم و سوم به ترتیب 8، 77/8 و 7/5 درصد خواهد بود.

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انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Numerical Modeling of Flow Patterns in Ogee Spillways with Culverts under Free Flow Conditions مدل‌سازی عددی الگوی جریان در سرریزهای اوجی همراه با کالورت در شرایط جریان آزاد 39 56 239797 10.30482/jhyd.2025.525447.1739 FA الهام سلیمانی گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران 0009-0002-1034-298X محمدرضا زایری گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران 0000-0002-3812-7512 سید محمود کاشفی پور گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران 0000-0001-7108-828x مهدی دریائی گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران 0000-0003-4304-0240 Journal Article 2025 05 23 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. اندازه‌گیری دبی و سازه‌های کنترل جریان به‌طور گسترده‌ای در کاربردهای مهندسی هیدرولیک مورد استفاده قرار می‌گیرند. هدف این مطالعه، مدل‌سازی عددی از جریان عبوری از سیستم ترکیبی سرریز اوجی با استاندارد USBR و سازه کالورت به عنوان شکاف در بدنه سد می‌باشد. علاوه بر این، به‌منظور بررسی الگوی جریان، اثر قرارگیری این کالورت در چهار حالت ارتفاعی مختلف در بدنه سرریز اوجی در نسبت‌های متفاوتی از دبی مورد بررسی قرار گرفت. برای انجام شبیه‌سازی‌های عددی، معادلات ناویر-استوکس میانگین‌گیری شده (RANS) با استفاده از روش حجم محدود در نرم‌افزار Flow-3D حل شده‌اند. ارزیابی داده‌های آزمایشگاهی و یافته‌های عددی برای سرریز اوجی بدون کالورت نشان می‌دهد که با استفاده از مدل آشفتگی K-\omega اختلاف پروفیل سطح آب با آماره‌های ضریب تبین (R2) و مجذور میانگین مربعات خطا (RMSE) به ترتیب مقدار 97/0 و 0112/0 تطابق دارند. به‌طورکلی نتایج نشان می‌دهد در حالت به‌کارگیری دو کالورت حداکثر سرعت جریان به میزان 40 درصد در پنجه سرریز اوجی کاهش داشته و به میزان 14 درصد موقعیت آن بالاتر از حالت سرریز بدون کالورت می‌باشد. بررسی عدد فرود در این حالت نشان می‌دهد که رژیم جریان را به دلیل کاهش مومنتوم به‌صورت پرش هیدرولیک مستغرق در پنجه سرریز تشکیل می‌شود. همچنین نتایج نشان می‌دهد در دبی کم، جایی که نقش کالورت برجسته‌تر بوده و سهم بیشتری از جریان کل از آن عبور می‌کند، افزایش سه برابری دبی منجر به کاهش افت کلی انرژی تا 30 درصد می‌شود.

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انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Hydraulics of a Flume with Multiple Cylindrical Baffles under Free-Flow Conditions هیدرولیک جریان در فلوم با موانع استوانه‌ای چندگانه در شرایط جریان آزاد 57 67 240640 10.30482/jhyd.2025.532244.1742 FA نسرین بهرامی دانشجوی دکتری سازه‌های آبی، گروه مهندسی آب، دانشکده کشاورزی، دانشگاه لرستان، خرم آباد، ایران امیر حمزه حقی آبی استاد، گروه مهندسی آب، دانشکده کشاورزی، دانشگاه لرستان، خرم آباد، ایران 0000-0001-9512-0360 محمود شفاعی بجستان استاد، گروه سازه‌های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران 0000-0003-3688-9561 حسن ترابی پوده استاد، گروه مهندسی آب، دانشکده کشاورزی، دانشگاه لرستان، خرم آباد، ایران 0000-0002-0976-9516 مصطفی رحمانشاهی پژوهشگر پسا دکتری، گروه مهندسی عمران و محیط زیست، دانشگاه پلی تکنیک هنگ کنگ، هنگ کنگ Journal Article 2025 07 02 Introduction Flow 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. Methodology The 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 discussion As 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. Conclusion This 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. فلوم‌ها یکی از متداول‌ترین روش‌های اندازه‌گیری جریان در مجاری باز مبتنی بر رابطه دبی- اشل هستند. در این تحقیق، هیدرولیک جریان در فلوم‌های با موانع استوانه‌ای به صورت آزمایشگاهی مطالعه شده است. برای این منظور مدل‌های مختلفی از این نوع فلوم در شرایط جریان آزاد مورد آزمایش قرار گرفت. متغیرهای این تحقیق شامل ارتفاع‌ها و قطرهای مختلف موانع و دبی‌های متفاوت در شرایط جریان آزاد می‌باشند. در این تحقیق برای 11 مدل فلوم در مجموع 190 آزمایش انجام شد. نتایج نشان داد با افزایش قطر و ارتفاع موانع، مقدار شاخص دبی کاهش می‌یابد. همچنین با کاهش ارتفاع و افزایش قطر موانع، سازه در دبی کمتری مستغرق گردید. سپس با استفاده از تحلیل ابعادی پارامترهای بدون بعد موثر این فلوم استخراج شده و در نهایت با استفاده از رگرسیون چند متغیره غیرخطی یک رابطه تجربی ارائه شد که دقت آن با استفاده از معیارهای آماری مورد ارزیابی قرار گرفت. مقدار R2 این رابطه برای داده‌های آموزش و واسنجی 98/0 می‌باشد. مقدار خطای نسبی این رابطه بر اساس داده‌های واسنجی حدود 11 درصد است.

https://jhyd.iha.ir/article_240640_5c15d897fb2e7b98d3577cc544f65f22.pdf

انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Application of SPM for estimating the velocity index in geometric channels کاربرد SPM در تخمین ضریب سرعت در کانال‌های هندسی 69 87 240642 10.30482/jhyd.2025.538906.1743 FA رامین محمدی گروه عمران، دانشکده مهندسی، دانشگاه فردوسی مشهد محمود فغفور مغربی گروه عمران، دانشکده مهندسی، دانشگاه فردوسی مشهد 0000-0002-0082-0020 سید حسین مجتهدی گروه عمران و محیط زیست، موسسه آموزش عالی اسرار، مشهد 0000-0002-9096-3016 Journal Article 2025 08 09 Application of SPM for estimating the velocity index in geometric channels Extended Abstract Introduction Accurate 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 Discussion The 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%. Conclusion This 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. مقدار ضریب سرعت (α) و تغییرات آن در عرض سطح آزاد آب در کانال‌های هندسی تاکنون بطور مشخص مورد بررسی قرار نگرفته است. در این پژوهش، با استفاده از روش تک نقطه‌ای (SPM)، که یک روش آسان و کم‌هزینه است، تغییرات ضریب سرعت در عرض سطح آزاد آب در کانال‌های هندسی مورد بررسی قرار گرفته است. این ضریب با استفاده از روش مذکور و با درنظر گرفتن توزیع قائم سرعت توانی، برای هر نقطه از سطح آزاد آب بدست آمده و سپس ضریب سرعت برای کل مقطع، به‌صورت میانگین وزنی محاسبه گردید. صحت-سنجی نتایج با استفاده از داده‌های آزمایشگاهی انجام شد که با توجه به خطای نسبی زیر 5%، نشان‌دهنده دقت بسیار خوب مدل SPM است. نتایج نشان می‌دهند که در تمام مقاطع هندسی، با باریک شدن مقطع کانال، محل سرعت حداکثر از سطح آزاد آب دور شده و مقدار ضریب α محلی افزایش می‌یابد (α=1.04 در کانال مستطیلی باریک) و در کانال‌های عریض، محل سرعت حداکثر به سطح آزاد نزدیک شده و مقدار ضریب α محلی کاهش پیدا می‌کند (α=0.714 در کانال ذوزنقه‌ای عریض). بنابراین، ارتباط کلی بین تغییرات منحنی‌های هم‌سرعت و ضریب α نتیجه گرفته و مشخص شد مقدار پیش‌فرض 0.85 برای ضریب سرعت نمی‌تواند در تمام شرایط هندسی قابل کاربرد باشد. علاوه‌بر این، مقایسه‌هایی بین ضریب سرعت بدست آمده از SPM و سایر پژوهش‌ها انجام شد که نشان داد محدوده تغییرات بدست آمده برای ضریب α در کانال‌های هندسی، در محدوده قابل قبول است و مقادیر خطای نسبی در شرایط مشابه از 0.92% تا 12.67% متغیر است

https://jhyd.iha.ir/article_240642_d41be7d74a1ab3f562268c915f6e6105.pdf

انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Laboratory modeling of porous flume with trapezoidal and triangular throats under submerged flow conditions مدلسازی آزمایشگاهی فلوم متخلخل با گلوگاه ذوزنقه‌ای و مثلثی در شرایط جریان مستغرق 89 106 240644 10.30482/jhyd.2025.540357.1746 FA حدیثه صدیقی هرسینی گروه مهندسی آب، پردیس کشاورزی و منابع طبیعی، دانشگاه رازی، کرمانشاه، ایران علی آرمان گروه مهندسی آب، پردیس کشاورزی و منابع طبیعی، دانشگاه رازی، کرمانشاه، ایران 0000-0001-9427-2987 مصطفی رحمانشاهی پژوهشگر پسا دکتری، دانشکده عمران و محیط زیست دانشگاه پلی تکنیک هنگ کنگ، هنگ کنگ. Journal Article 2025 08 09 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. Conclusion This 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. فلوم‌های بدون گلو به دلیل ساختار ساده و اجرای راحت، در کنار دقت بالایی که دارند، ابزاری کارآمد جهت اندازه‌گیری دبی در کانال‌های روباز محسوب می‌شوند. از طرفی سازه‌های گابیونی به دلیل سازگاری با محیط زیست و کارایی بهتر آنها نسبت به سازه‌های صلب مورد توجه محققین مختلف قرار گرفته است. در این پژوهش به مدلسازی آزمایشگاهی فلوم متخلخل با گلوگاه ذوزنقه‌ای و مثلثی در شرایط جریان آستانه استغراق و مستغرق، پرداخته شده است. بدین منظور 36 فلوم ساخته شد که دارای ارتفاع، بازشدگی گلوگاه و درصد تخلخل متفاوتی بودند. در مجموع 330 آزمایش در شرایط جریان آستانه استغراق و 880 آزمایش در شرایط جریان مستغرق بر روی این فلوم‌ها انجام گرفت. نتایج حاکی از آن است که برای یک دبی ثابت در صورتی که بازشدگی و تخلخل مصالح ثابت باشد، با افزایش ارتفاع فلوم، عمق آستانه استغراق به میزان 5 تا 28 درصد افزایش پیدا می‌کند که موجب مقاومت فلوم در برابر استغراق می‌شود. همچنین، فلوم متخلخل با ارتفاع 20 سانتی‌متر که گلوگاه مثلثی دارد و مصالحی با درصد تخلخل 37 درصد پر شده است، مقاوم‌ترین فلوم در برابر استغراق است. در انتها، با استفاده از رگرسیون چند متغیره غیرخطی به عنوان یک مدل جعبه سفید و نیز مدل GEP به عنوان یک مدل جعبه خاکستری روابطی تجربی بر اساس تحلیل ابعادی انجام شده، استخراج شد و با استفاده از معیارهای آماری مورد ارزیابی قرار گرفت.

https://jhyd.iha.ir/article_240644_5169f44e4a46c6bffe38180829ebfb20.pdf

انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Numerical Modeling of the Sediment Bed Downstream of Flushing Channels for Different Gate Openings and Slopes مدل‌سازی عددی بستر رسوبی پایین‌دست مجاری شست‌وشو برای بازشدگی‌ها و شیب‌های متفاوت 107 122 240645 10.30482/jhyd.2025.541158.1747 FA حسام وطن دوست گروه مهندسی عمران، دانشگاه آزاد اسلامی پرند و رباط کریم علی مهدی ابهری دانشجوی کارشناسی ارشد مهندسی مکانیک ، واحد علوم و تحقیقات تهران، دانشگاه آزاد اسلامی، تهران، ایران Journal Article 2025 08 15 Introduction Sediment 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. Methodology The 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 Discussion Simulation 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. Conclusion The 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. یکی از مباحث مورد توجه در مهندسی هیدرولیک، پدیده رسوب‌شویی و اثرات مخرب آن بر مورفولوژی و زیست محیط رودخانه در پایین‌دست آن است. در بررسی این پدیده پیش‌بینی تغییرات تراز بستر رسوبی ناشی از رسوب‌شویی ضروری است. ازآنجایی‌که انجام تحقیقات آزمایشگاهی و میدانی در زمینه پدیده معمولاً پرهزینه و زمان‌بر است، چنانچه بتوان به راهکاری برای بررسی آن به طور گسترده‌تر و کم‌هزینه‌تر رسید، می‌توان در کنترل هزینه‌ها و همچنین افزایش سرعت تحقیقات گام مهمی برداشت. در این پژوهش به بررسی اثرگذاری فاکتورهای شیب، میزان بازگشایی دریچه و زمان بر تغییرات بستر رسوبی در مجاری رسوب‌شویی پرداخته شده است. با مقایسه صورت‌گرفته بر روی مدل فیزیکی و آزمایشگاهی مشخص گردید مدل آشفتگی RNG با میزان خطای 3/4 درصد نسبت به دو مدل آشفتگی k-ε و Les در شبیه سازی بستر فرسایش‌پذیر مناسب‌تر بوده و جهت ادامه مطالعات انتخاب گردید. پس از مشخص شدن میزان خطا با تعریف آزمون‌های مختلف مشخص گردید با کاهش میزان بازشدگی دریچه از 100 به 50 و 25 درصد عمق آبشستگی در مجاورت دریچه حدود 35 و 60 درصد و طول ناحیه فرسایش یافته نیز در پایین دست تا 4/1 برابر افزایش می‌یابد. بررسی‌ها نشان داد با افزایش شیب مجرای رسوبشویی از 5 به 15 درصد عمق آبشستگی در مجاورت دریچه تا 45 درصد افزایش می‌‌یابد و حجم رسوبات منتقل‌شده به پایین‌دست با افزایش حدود ۵۰ درصدی مواجه می‌گردد. همچنین مشخص گردید فاکتور زمان در شکل‌گیری پروفیل بستر نسبت به شیب مجرا و بازشدگی‌ دریچه تاثیر کمتری را دارد.

https://jhyd.iha.ir/article_240645_7cf8447656b56d1601a7ec289d08d3a3.pdf

انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 21 1 2026 03 21 Laboratory investigation on the Discharge coefficient of a composite section weir with a bottom Gate بررسی آزمایشگاهی تعیین ضریب آبگذری سازه سرریز با مقطع مرکب همراه با دریچه تحتانی 123 137 240646 10.30482/jhyd.2025.551538.1749 FA فاطمه مهویدی گروه علوم و مهندسی آب دانشگاه بیرجند حسین خزیمه نژاد دانشگاه بیرجند 0000-0002-2731-1170 یوسف رمضانی گروه علوم و مهندسی آب دانشگاه بیرجند Journal Article 2025 10 06 Introduction In 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. Methodology The 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 Discussion The 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. Conclusion Comparing 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. در این پژوهش به مطالعه آزمایشگاهی سازه ترکیبی سرریز با مقطع مرکب همراه با دریچه تحتانی پرداخته شد و ضریب جریان در شرایط هیدرولیکی مختلف مورد بررسی قرار گرفت. آزمایش‌های مربوط به این پژوهش در آزمایشگاه هیدرولیک دانشکده کشاورزی دانشگاه بیرجند در کانال مستطیلی به طول 10 متر، ارتفاع 50 سانتی‌متر و عرض 30 سانتی‌متر انجام گرفته است. به منظور بررسی و محاسبه ضریب جریان، آزمایش‌ها در دو حالت جریان با بازشدگی ثابت دریچه با دبی‌های متفاوت و بازشدگی متفاوت دریچه با دبی‌های ثابت در دو شیب 002/0 و 004/0 صورت گرفت. نتایج پژوهش حاضر نشان داد با افزایش پارامتر بدون‌بعد Y/D (ارتفاع آب روی دریچه نسبت به ارتفاع کانال)، ضریب جریان دارای روند نزولی می‌باشد. از طرفی با کاهش Y/D، ضریب جریان افزایش یافته و به سمت عدد 76/0 میل می‌کند. همچنین با افزایش پارامتر بدون‌بعد H_g/D (میزان بازشدگی دریچه نسبت به ارتفاع کانال)، ضریب جریان افزایش می‌یابد و ضریب جریان در محدوده 72/0C_T≤ قرار می‌گیرد. تغییر شیب کف کانال نیز تغییرات قابل توجه‌ای در ضریب جریان سازه ایجاد نکرد. مقایسه نتایج پژوهش حاضر با سایر پژوهش‌های مرتبط نشان از همخوانی و تطابق نتایج دارد؛ به عبارتی با افزیش پارامتر ارتفاع بی‌بعد آب روی دریچه ضریب جریان سازه ترکیبی کاهش و با افزایش پارامتر بازشدگی بی‌بعد دریچه، ضریب جریان سازه ترکیبی افزایش می‌یابد.

https://jhyd.iha.ir/article_240646_6a14e11386c50d1c0031f6abcc309761.pdf