محسن ایثاری

بررسی پدیده انتقال رسوب، شامل فرآیندهای فرسایش و رسوب‌گذاری، در رودخانه‌ها از اهمیت بسزایی برخوردار است. مداخلات انسانی از طریق احداث سازه‌های هیدرولیکی در مقاطع عرضی رودخانه، منجر به اختلال در چرخه طبیعی انتقال رسوب می‌گردد. به عنوان نمونه، ساخت سد در بالادست، منجر به تجمع رسوبات در مخزن سد و کاهش قابل‌توجه بار معلق در پایین‌دست می‌شود. در هنگام وقوع سیلاب، افزایش سرعت جریان ناشی از تنگ‌شدگی مقطع رودخانه در محل پایه‌های پل، منجر به تشدید فرسایش بستر می‌گردد که این امر می‌تواند به تهدید پایداری و کارآمدی سازه پل منجر شود. این پژوهش با سه هدف اصلی (کلی) انجام شده است: نخست، تحلیل تاثیر وجود سازه‌های هیدرولیکی در مقطع عرضی رودخانه بر پارامترهای هیدرولیکی نظیر تراز سطح آب، سرعت جریان و پتانسیل فرسایش‌پذیری بستر در شرایط سیلاب؛ دوم، بررسی تغییرات پارامترهای هیدرولیکی از جمله غلظت رسوب جریان، تغییرات بستر و تاثیر دمای آب بر فرسایش بستر رودخانه سقز به علت وجود سد بالادست؛ و سوم، تخمین حداکثر عمق آبشستگی در پایه‌های پل مجتمع تجاری کردمال و مکان‌یابی دقیق این پدیده. این پژوهش با استفاده از مدل‌های هیدرودینامیکی نرم‌افزار HEC-RAS برای شبیه‌سازی جریان‌های ماندگار و شبه‌غیرماندگار دبی روزانه و معادله بار کل رسوب یانگ انجام شده است. علاوه بر این، از مدل رسوبی نرم‌افزار FLOW-3D برای تحلیل آبشستگی پایه‌های پل استفاده شده است. نتایج نشان می‌دهد که احداث سد در بالادست، منجر به افزایش فرسایش مقاطع عرضی رودخانه می‌گردد، در حالی که در شرایط بدون سد، در این مقاطع رسوب‌گذاری رخ داده بود. دبی کل رسوب جریان در زمان دبی اوج، در ورود به محدوده مورد مطالعه، برای حالت عدم وجود و وجود سد به‌ترتیب 83/30640 و 063/9964 تن در روز بوده است که حاکی از کاهش 48/67 درصدی دبی رسوب به‌دلیل احداث سد بالادست است. دبی رسوب خروجی از محدوده پژوهش برای حالت‌های بدون سد و با وجود سد به‌ترتیب 93/12333 و 62/7723 تن در روز بوده است که نسبت به دبی رسوب ورودی بالادست حدود 75/59 درصد و 48/22 درصد کاهش یافته است. تغییر الگوی جریان ناشی از برخورد رودخانه با تکیه‌گاه باعث تشدید عمق آبشستگی در پایه‌های کناری می‌شود. حداکثر عمق آبشستگی در پایه‌های کناری به 96/1 متر رسیده است. عمق آبشستگی در پایه‌های میانی پل نسبت به پایه‌های کناری کمتر است و حداکثر عمق آبشستگی در این پایه‌ها به 09/1 متر می‌رسد. نسبت اختلاف حداکثر عمق آبشستگی بین پایه‌های کناری و پایه‌های میانی به 82/79 درصد می‌رسد.

There have been more studies on the numerical modeling of spillways in the last few years due to the quick development of numerical simulation technology. In contrast, the case of gates particularly vertical plane gates was not as well studied in the literature, which focused primarily on uncontrolled spillways. Hence, this thesis addresses this gap by exploring the simulation of flow characteristics over a controlled Ogee-type spillway surface. The main objective of the research is to simulate and assessing flow characteristics over a controlled Ogee-type spillway for two models. The investigation and analysis focused on how altering each of the three parameters (flow rate, height of the gate opening, and width of the spillways) influenced: the water level changes along the spillway, the pressure distribution across the spillway surface, comprehending the variations in water velocity along the spillway, and the variations in shear stress across the spillway surface. Numerical simulations are conducted in the study using the FLOW-3D program. To simulate the turbulent flow, the software uses both the Two-Equation (k−ε) model and the Large Eddy Simulation (LES) model to numerical modeling for two distinct model into four different scenarios to compute the pressure, velocity, and shear stress at seven sensors along the controlled Ogee-type spillways. The results are compared with observed data from the literature as experimental and another numerical simulation result of the turbulence model (𝑘−𝜀) obtained. A good agreement was achieved between the numerical results from both equations and the experimental data except for sensors 5, 6, and 7, for the first case, and sensor 6, and 7 for the second case due to varying the three parameters for every simulation. Furthermore, the results in both equations matched more closely with the numerical output of the uncontrolled (k−ε) model from FLOW-3D compared to the experimental data. The results showed that the pressure distribution typically decreases with increases the flow rate. Conversely, it tends to increase as height of the gate opening or width of the spillway increases. Also decreasing just height of the gate opening, it causes to decreasing the pressure distribution in the first region the negative region and increasing from all remain sensors. The first region shows that as discharges increase, the negative pressure decreases and vice versa. Furthermore, the first model analysis identified two regions of negative pressure throughout the domain: one situated at the Ogee curve and the other located at the end of the sloping straight line, after the Ogee curve. In this study, the performance of numerical models in predicting pressure distribution was evaluated using surrogate models that considered three parameters and applied the Pareto optimization method. MATLAB codes were used to solve the equations. The surrogate model results showed good agreement with the numerical results from FLOW-3D, achieving a coefficient of determination (R²) of 1 for both the exact and predicted pressure distribution data at each sensor, as well as for Latin Hypercube cases 1 and 2 for both equations. This indicates that surrogate modeling is an effective tool for predicting responses in controlled Ogee-type spillways and is useful for optimizing the three variables to determine the optimal pressure. The result in both scenarios, the (LES) equation model consistently yields optimal pressures that are closer to zero or even positive, which is beneficial for reducing the risk of cavitation. Additionally, these pressures are closer to atmospheric pressure, further lowering the probability of cavitation. The main goal of assessing and optimizing pressure distribution for a controlled Ogee spillway is to boost its structural integrity, hydraulic performance, and safety. This brings numerous advantages, including better operational efficiency, enhanced safety, lower maintenance costs, and a longer lifespan for the spillway structure. The numerical results for velocity and shear stress data using the (k−ε) turbulence model equation show good agreement when comparing a controlled Ogee-type spillway to an uncontrolled Ogee spillway using the (k−ε) turbulence model equation. This study shows that FLOW-3D modeling can efficiently assess controlled Ogee-type spillways' hydraulic performance.

The design and performance evaluation of drip irrigation systems are essential for achieving optimal efficiency and uniformity. This study emphasizes the importance of assessing existing designs and the various factors influencing their performance. With the advancement of computer technology, numerical models have become invaluable in the hydraulic design of irrigation systems. This research employs IRRICAD software to simulate flow and pressure characteristics and compares these simulations with experimental data to validate accuracy. Key findings include the validation of IRRICAD for its accuracy, features, and accessibility; the critical role of selecting correct parameters for simulation models; and a comprehensive understanding of irrigation performance measures crucial for evaluating overall system efficiency. The study introduces a novel methodology for evaluating drip irrigation systems by collecting pressure and dripper flow data and inputting them into the IRRICAD program to diagnose and identify issues related to zone performance and system flows. These issues are typically manifested through variations in pressure and dripper flow rates. The study also involves determining the dripper exponent of flow, which is then reentered into the program for thorough system evaluation. This study evaluates the hydraulic performance of a drip irrigation system designed for the University of Sulaimani using IRRICAD software, laboratory testing of drippers, and field measurements. The model's outputs were compared with actual measurements to validate its accuracy. Laboratory tests indicated a mean flow variation of 0.028, which is favorable, and a mean coefficient of variation (CV) of 0.013, which is considered excellent. Field measurements for hydraulic performance were conducted at a constant operating pressure, assessing parameters such as the Emitter Discharge Coefficient of Variation (Vqs), Hydraulic Design Coefficient of Variation (Vhs), Emitter Performance Coefficient of Variation (Vpf), Emission Uniformity (EU), Christiansen Uniformity Coefficient (CU), and Statistical Uniformity of Emitter Discharge (Us).The results revealed that CU, EU, and Us fall within the excellent classification, with CU and EU exceeding 90% efficiency. The Vqs value is below 0.1, indicating excellent performance, while Vhs falls within the 10-20% range and Vpf within the 5-10% range, both indicating very good performance. Additionally, a comparison of pressure values between field measurements and two data sources from the IRRICAD software showed minimal differences: 0.313 for Field Observations (OPF), 0.315 for IRRICAD Observed Points (OPI), and 0.324 for the IRRICAD Summary Report (SRI). These minimal differences suggest that IRRICAD's estimates closely align with field observations. To validate the IRRICAD model, the mean squared error (MSE), mean absolute error (MAE), and root mean squared error (RMSE) were calculated. For discharge values, the errors were 2.29, 1.09, and 1.48, respectively, while for pressure values, the errors were 0.08, 0.26, and 0.28, respectively. This comparison demonstrates that using pressure values for evaluating and improving irrigation system performance with IRRICAD software yields better accuracy and less deviation from modeled values, particularly when pressure-compensating drippers are employed. The study's insights into the design and performance evaluation of drip irrigation systems underscore the importance of accurate simulation models and comprehensive performance assessments in achieving optimal irrigation system performance. The experimental results show that the IRRICAD software closely aligns with field data, demonstrating minimal discrepancies and confirming its utility for accurate performance evaluation. Furthermore, the research explores different scenarios to understand the impact of varying parameters on system performance. The findings highlight the importance of accurate pressure and flow measurements, as discrepancies in these can significantly affect the system's efficiency. The study also identifies common issues such as excessive pipe velocity and nozzle pressures outside the specified operational range, suggesting areas for system optimization. This study's insights into the design and performance evaluation of drip irrigation systems emphasize the critical role of accurate simulation models and comprehensive performance assessments. The novel method proposed for assessing irrigation systems, validated through rigorous experimental comparison, provides a robust framework for future research and practical applications aimed at enhancing irrigation efficiency and sustainability.

Culverts are crucial components of surface water drainage systems, often favored for their cost-effectiveness compared to structures like bridges. However, scouring at the upstream and downstream ends can undermine culvert foundations, potentially leading to collapse and significant damage to surrounding structures. Additionally, culvert blockage during flood events alters the flow structure, increasing the risk of failure. This research investigates the scour of culverts in sandy environments and suggests using barrels to minimize it under various flow and obstruction conditions. This study experimentally investigates the reduction scouring process at the downstream culvert with different inlet blockage rates. It spans flow rates from 4.8 to 20 l/s across both box and circular culverts for two different hydrographs created in seven steps for unsteady flow conditions, while steady flow conditions were analyzed at flow rates of 13.8 l/s and 20 l/s were chosen based on peak discharge in two hydrographs, reducing the scouring process by using the 10 to 11 barrels in (50 mm width, 50 mm length, and 150 mm height) at downstream the culvert sorting in different locations in three options. We conducted experimental tests under both steady and unsteady flow conditions for two distinct hydrographs. Ninety-six experiments are carried out. The median grain size (d50 = 1.77 mm) of sediment material was used in this investigation. The findings were compared to the base case for the same shape and level of blockage. Results indicate that barrels notably diminish scour under steady conditions, reducing the maximum depth of scour (dsm), and the formation of scour holes compared to the base case in the same shape and blockage rate. About (Xsm), the position of maximum scour decreased in most cases when applied to the barrels, and the comparison between circular and box data sets reveals that the maximum scour depth values are greater in the circular data sets than in the box data sets. During unsteady flow, barrels effectively in both shapes when used; a barrel’s maximal scour depth location often reduces the maximum depth of scour (dsm), the position of maximum scour depth (Xsm), and scour hole formation when the used culverts are unobstructed or partially obstructed, and the evaluation of scour depth was often greater in circular culverts during the rising limb of the hydrograph compared box shape for all scenarios. However, when we use an inlet blockage, it does not always result in increases in deepest scour depth in both steady and unsteady flow conditions. Nevertheless, there's a risk of overflow, especially in circular culverts with significant blockage in both flow conditions. The study underscores the importance of hydraulic factors in scour mitigation to improve culvert performance. Comparisons between steady and unsteady flows reveal consistent trends in souring process reduction, emphasizing the potential of barrels for effective mitigation.

به دلیل تغییراقلیم و مواجه شدن با کمبود آب مخصوصاً درکشورهای درحال توسعه، نیازبه مدیریت این منبع با ارزش بیش ازپیش اهمیت دارد. از مشکلات تغییر اقلیم می‌توان به حدی شدن (گرما و یا سرمای شدید)آب و هوا، وقوع سیل و آب گرفتگی اشاره کردکه مشاهده شده سالانه مناطق در معرض سیل را با خسارت‌های زیادی روبه رو کرده است. تغییر اقلیم همچنین باعث شده که کمبود آب بیش از پیش احساس شود و استفاده وبهره برداری از آب‌های زیرزمینی به عنوان یک گزینه مهم در اولویت‌ها قرار گیرد. هدف اصلی این تحقیق بهینه سازی تخصیص آب، ذخیره آب ناشی از بارندگی و کاهش سیلاب است چون با افزایش جمعیت این مشکلات و چالش‌ ها بیشتر نمایان می‌شوند که به این منظور در این تحقیق با استفاده از مفهوم شهر اسفنجی مناطق سیل خیز شهر سنندج مشخص، واقدمات لازم ومطالعات و تحقیقات اولیه برای اجرای این مفهوم انجام گیردیده است بر این اساس در این تحقیق با استفاده از نقشه ی رقومی ارتفاع (DEM) وضعیت توپوگرافی منطقه مورد بررسی قرار‌گرفته وسپس، با استفاده از نرم افزار GIS مناطق آبگیر و کم ارتفاع مشخص شده اند. بعد از آن میزان سرعت نفوذ آب در خاک غالب شهر استان و برای خاک‌های مختلف محاسبه و میزان بارندگی با استفاده از مدل‌های شبکه عصبی مصنوعی مدل سازی شده است و با استفاده از نقشه‌‌ی NDVI و نقشه‌ی جایگیری ساختمان‌ها و جاده‌ها توسط نرم‌افزار QGIS عدد CN محاسبه شد ودر ادامه نیز با استفاده از نرم افزار GIS نیز محل‌های مناسب برای پیاده‌سازی شهر اسفنجی همراه با محیط ومساحت آنها مشخص شده. در بخش تخصیص با نرم‌افزار WEAP محاسبه شدکه میزان تقاضای برطرف نشده(کمبود) و کل آب مورد نیاز در سه بخش شهری- صنعتی، کشاورزی و تغذیه آب زیرزمینی از سال 2021 الی 2042 به ترتیب 17071.13908 و 20739.05353 میلیون متر مکعب است و در بحث مقدارمیزان آب پوشش یافته(نیاز برآورده شده) در سال‌های مختلف، مقدار آن برای بخش‌های ذکرشده متفاوت بدست آمده.

The study investigated the simulation of flow characteristics over an ogee-type spillway surface. The study's primary goal is to simulate and analyze flow characteristics over an ogee-type spillway, commonly used in water engineering for controlling water flow over a dam or weir. The study focuses on how flow rate changes with different conditions, analyzing how the water level changes along the spillway on the other side. Also, investigating how pressure varies across the spillway surface, understanding how the velocity of the water changes along the spillway, and analyzing the shear stress acting on the spillway surface. The study uses the Flow-3D software to perform numerical simulations. The software utilizes an RNG and LES turbulence model to represent turbulent flow conditions. The choice of this model is expected in Computational Fluid Dynamics (CFD) for simulating turbulent flows. The results are compared with observed data from literature as experimental and numerical simulation. Experimental and simulation data by ANSYS software studied by (Kanyabujinja, 2015). Also, the numerical simulation result of turbulence model "𝑘−𝜀" obtained by (KARIM, 2017). Good agreement is reported between the numerical results by using turbulence model (RNG) compared to experimental results. This signifies that the numerical model effectively mirrors the behavior of the physical flow. The results suggest that the pressure distribution is reduced as the discharge increases and vice versa. This indicates a relationship between flow rate and pressure distribution on the spillway and identifies two regions of negative pressure within the flow domain. The first is located at the ogee curve, and the second is observed at the end of the sloping straight line beyond the ogee curve. To address these findings, it was suggested that the slope of the spillway's horizontal surface could be reduced, or the ogee formula changed. Negative pressure zones can have implications for cavitation, a concern in spillway design. The slope of the spillway surface after the ogee crest is noted to influence pressure distribution and potentially prevent cavitation issues. In conclusion, this study offers valuable insights into the flow characteristics of ogee-type spillways. It effectively demonstrates the accuracy of numerical modelling software, specifically Flow-3D, in representing the system's physical behavior. Moreover, it underscores the significance of comprehending the impact of discharge and spillway design on pressure distribution and cavitation risk.

This research investigates how the presence of alternating steps in stepped spillways situated downstream of embankment dams affects the flow properties. This investigation employs Flow 3D software for conducting simulations and analysis. The research goals were achieved by creating six numerical models. These models included two with regular step patterns (MR) and four with alternating step patterns (MA), each varying in terms of step heights and configurations. Each model measured 1.08 m in depth, 2.54 m in length, two regular and two alternatives have 0.6 m width, other two alternative models with 0.9 m width. (MR1, MA1, MA3) have 28 steps with 3.6 cm height, (MR2, MA2, MA4) have 12 steps with 7.2 cm height and 4 steps with 3.6 cm height. All models have a longitudinal slope (θ) of 26.6°. The models were subjected to different flow rates, spanning from 8.01 ≤ Q ≤ 164.3 m3/h, in order to examine and analyze their flow characteristics. To simulate the turbulent flow, the Renormalized group (RNG) turbulence model is done in the numerical modelling. Outcomes indicate that alternative steps cause more energy dissipation than regular steps, and alternatives with 0.9 m width dissipate more energy than alternatives with 0.6 m. by increasing discharge energy dissipation will decrease. And those models which have 7.2 cm step height dissipate more energy than models with 3.6 cm step height. As a results MA4 is a best energy dissipator. Moreover, regular steps have longer hydraulic jump length than alternative steps. and models with alternative steps with 0.9 m width have smaller hydraulic jump than alternative step models with 0.6 m. by decreasing discharge hydraulic jump will decrease. And by increasing the steps height the hydraulic jump will decrease. As a results smaller stilling basin is required for MA4.

پدیده فرونشست برخلاف سایر پدیدههای مخرب مانند سیل و زلزله در بازه زمانی طولانی و بهآرامی رخ میدهد. فرونشست به دلیل ایجاد آسیب های غیرقابلجبران از قبیل آسیب به زیرساختها، خطوط انتقال انرژی )گاز، آب و برق(، ساختمانها، ایجاد فرو چالهها، سیل در مناطق ساحلی و از همه مهمتر تخریب خاک و سفرههای آب زیر زمینی ، به یکی از دغدغه و مسائل روز مدیریتی تبدیل شده است. بهرهبرداری ب یش از حد آب از سفرههای زیر زمینی مهمترین عامل ایجاد پدیده فرونشست است. برداشت بیش از حد مجاز از منابع آب زیر زمینی موجب رشد نرخ تنش موثر در آبخوان و تغییر در تراکم ذرات ریزدانه رسوبات میشود. بنابراین، بر اثر پدیدآمدن این تغییرات در آبخوان یک منطقه، فرونشست رخ میدهد. همچنین عوامل طبیعی دیگری همچون ضخامت رسوبات و قابلیت انتقال آبخوان میتواند به طور مستقیم و غ یرمست قی م بر پدیده فرونشست اثرگذار باشد. در این پژوهش تمرکز بر محاسبه، ارزیابی و مدلسازی میزان فرونشست متاثر از برداشت بیرویه از منابع آب زیر زمینی ، ضخامت رسوبات و قابلیت انتقال آبخوان با بهرهگیری از روش تداخل سنجی راداری و در دشت دهگلان استان کردستان در بازه زمانی 1 فروردین 1401 تا )MLP( شبکه عصبی مصنوعی پرسپترون چندلایه 2 مهر 1402 میباشد. نرخ فرونشست محاسبه شده با استفاده از تصاویر سنجنده سنتینل - 1 و تکنی ک تداخل سنجی راداری بیانگر ابتلای دشت دهگلان به پدیده مخرب فرونشست میباشد. حداکثر نرخ فرونشست محاسبه شده از این روش برابر با 165 میلیمتر و نرخ بالا آمدگی برابر 41 میلیمتر است و توزیع مکانی فرونشست در نواحی غربی و مرکزی بیشتر از نواحی شرقی ظاهر شده است. علاوه بر این تکنیک، در آبخوان دشت دهگلان استان کردستان با استفاده از روش مدلسازی با شبکه عصبی پرسپترون چندلایه در نرمافزار متلب مقدار فرونشست به کمک نتایج بهدستآمده از روش تداخل سنجی راداری و دادههای تغییرات تراز آب زیر زمینی، قابلیت انتقال آبخوان و ضخامت رسوبات پیشبین ی و مدلسازی شد. این مقادیر نشاندهنده توانایی بالای مدل در شبیهساز ی و پیشبین ی فرونشست در قیاس با مقادیر حاصله از روش تداخل سنجی راداری است بهگون های که قادر به محاسبه مقدار دادههای گمشده نرخ فرونشست در اثر اعوجاجهای هندسی را بادقت خوبی پیشبی نی کند. همچنین، در تحلیل رگرسیونی دادههای مدلسازی شده و مقادیر حاصله از روش تداخل سنجی راداری، به ضریب رگرسیون متوسط 0.92 دستیابی شد و این امر حاکی از انطباق بسیار خوب این نتایج است. در نهایت، باید به این مسئله توجه داشت که روند فرونشست در دشت دهگلان سیر صعودی دارد و بههیچوجه آسیبهای وارد شده به آبخوان دشت دهگلان قابلبازگشت نمیباشد و فقط باید برای آینده تصمیمات درستی از قبیل فرهن گسازی، اعمال ممنوعیتها و مجازات شدید در جهت کاهش بهر هبرداریهای غیرمجاز و ب یرویه از منابع آب زیرزمینی و نظارت مداوم بر فرونشست منطقه با استفاده از روشهای مدلسازی شبکه عصبی و سنجش از راه دور اتخاذ گردد.