The increase of population and demand for water, agriculture and energy cause rapid increase construction of the dam has been. Moreover, the increase of dam height to increase storage and estimate the need for water cause increase the velocity of water over the spillway has been. Spillways, chutes and bottom outlets are important hydraulic structures for dam safety. Due to high velocities combined with low pressures, cavitation damages may occur on chute bottom and cause major damages or endanger the dam stability. Damage experience for flows in spillway tunnels and chutes indicates that damage becomes significant when water velocities exceed 30m/s, this velocity or head can be considered as the borderline for high velocity or high head flows. Introducing air to high-speed flow is necessary to prevent pressure reduction and its events such as cavitation. It is possible to protect spillway surfaces from cavitation damages using aerator devices. Usually, the air entering the flow is not reached to the bed chute. It is necessary to install the first aerated according to topographic conditions and cavitation index at the appropriate location. By determining the process of changing the air concentration of the bed, the distance between the two aerators can be determined. The air in the flow causes the compression and damping that cause Bursting bubbles. In result, the damage caused by cavitation is reduced. So cavitation investigations will be necessary and need to reduce and prevent cavitation damages. The length of the flow jet has a fundamental role in determining the distance between two aerators. With increases the length of the jump, the contact surface of the upper and lower layers of the jet is in more contact with the air and affects the amount of air entering the flow. The absorbed air is removed from the flow after the Jet collision. By determining the minimum concentration of air in the bed, an optimal distance between the two aerations can be selected to prevent cavitation damage. Select the minimum air concentration of bed is based on the relationship provided by Wood (1983). It means that the concentration of average air in the stream is higher, which causes the flow of bulking and requires taller walls for the sides of the shut Which is not economically feasible. The variation in the air concentration of the bed can only be considered as a function of the length of the jump flow and the upstream heights. Creating a suitable duct for providing A negative cavity pressure Lead to better performance that causes increases the distance between aeration. So use of aerators in suitable places and the entrance of air to water flow is a most effective way to reduce this damage, therefore in this study, an equation has been derived to estimate the distance between two aerators base on 1200 data of 90 experiments with R2 more than 0. 84. Results of the present study with distance aerators of the Azad dam based on the minimum air concentration of bed have been compared and investigated.

Geometry of the chute blocks in stilling basins plays a significant role in size and type of these structures. One of the most influencing factors in the design of the blocks is the fluctuating pressure which may cause fatigue on the blocks. Despite investigations conducted by many researchers, there is not enough information about the pressure fluctuation around chute blocks in compacted stilling basins such as Saint Anthony Falls (SAF) basins. In this paper, the results of a naval experimental work and measurement of pressure fluctuations around chute blocks of SAF stilling basins are reported. The results show that the pressure fluctuations around the chute blocks cannot be overlooked in designing such structures. The variation of pressure fluctuation with Froude number of incoming supercritical flow at various faces of the chute block is reported, which shows an increasing trend of pressure fluctuation. It is also observed that the submergence of hydraulic jump will decreasingly affect the pressure fluctuations. The trend of variations will follow different patterns at the different faces of the block.

Induced total pressure by flow, including mean and fluctuating components, around a selected chute block in SAF stilling basins downstream of an ogee spillway was studied. Several pressure holes were selected on various faces of a selected chute block to get enough information regarding the total pressure field. This paper reports the results of an experimental work and measurement of mean and fluctuation pressures around chute blocks of SAF stilling basins. The observations showed that the maximum total pressure varies inversely with Froude number of incoming flow while its position of occurrence follows a quadratic polynomial relationship. Statistical analysis also showed that the peak instantaneous pressure fluctuations could be as large as ±4.5 times the RMS value.It is concluded that pressure fluctuation around the chute blocks may double the magnitude of pressure field around the chute blocks and can not be overlooked in designing such appurtenances.

Abstract The Shatta al-Arab River is approximately 200 km long and is formed by the confluence of the Tigris and Euphrates rivers in the city of al-Qarna, 74 km northwest of the port city of Basra in southern Iraq. The river is affected by climate change and frequent rains, it shows the risk of flooding and overflowing at the riverside. The Shatta al-Arab River Basin in the city of Basra has been faced with floods and devastating consequences. The purpose of this study is to evaluate and analyze the spatial risk of river overflow of the Shatta al-Arab River in the city of Basra, Iraq, using the Geospatial Information System (GIS). GIS was used to estimate and evaluate the location and zoning of the Shatt al-Arab floodplain in Basra using the available data. By identifying the types of land uses around the river, provided a detailed analysis of how they are distributed in different risk areas. The results show that the agricultural landuse due to its large area is more at risk than other uses. The results of this study can have a significant impact on preventing irreparable flood damage in this area.

One of the ways to prevent creating negative pressure and cavitation in spillways is to introduce air into the flow over the spillways. Understanding the distribution of air concentration variations along the spillway is of significant importance for estimating the aeration level. This study explores the application of GPR and SVM molels in predicting air concentration. To achieve this, a dataset of 2268 laboratory experiments obtained from hydraulic models of chute spillways was utilized in the modeling process. Various input models were defined based on different combinations of measured parameters. The results demonstrate the high capability of both methods in estimating the required air concentration over the spillway. In predicting air concentration in the chute spillway under artificial aeration conditions, flow discharge (QW), longitudinal distance ratio from the end of the deflector to the channel width (L/W), and depth ratio (perpendicular to the spillway) to channel width (Y/W) significantly influenced the outcomes. Statistical indices, including R, DC, and RMSE for this case were 0.9214, 0.8451, and 1.008, respectively, in the GPR, and 0.9333, 0.8662, and 0.937 in the SVM. For scenarios without artificial aeration, the model with input parameters QW, L/W, Y/W, and ΔP (pressure difference between atmospheric pressure and the pressure under the jet) achieved the best performance in the GPR method with values of R=0.9222, DC=0.8644, and RMSE=0.914. In the SVM, the same model with values of 0.87, 0.7543, and 0.123 for R, DC, and RMSE, respectively, was selected as the superior model.

A physical model of gabion overflow dams was studied to determine the velocity profile and Reynolds shear stress.Physical tests were done under two different conditions of dam crest, overflow dams with impermeable and with permeable crests.Instantaneous velocity components over dam crest were measured by an ADV (Acoustic Doppler Velocimeter) instrument. This instrument is capable of measuring instantaneous velocity components with frequencies up to 25 Hz. Average velocity components and bed shear stress were extracted from ADV measurements. The results of this research show the effect of crest permeability on velocity and Reynolds shear stress. The magnitude of Reynolds sheer stresses, horizontal velocity components, and absolute value of vertical velocity components under the permeable scenario are bigger than those of the impermeable scenario. Velocity distribution over the dam crest is different from the universal logarithmic profile.

In this study the effect of chute bed roughness height on energy dissipation has been investigated. First effective parameters were identified and then a general dimensionless relationship was developed. A series of tests were conducted by a physical model using the bed slopes of 25 and 35 degrees and four different uniform roughness heights (3. 38, 7, 12. 7 and 38. 1 mm) having uniform particle sizes on the bed. Total of 80 tests were conducted with flow discharges range between 4 and 40 L s-1 and Froude number between 4. 5 and 9. A relationship was developed for prediction of energy slope on this type roughened bed chutes and the results obtained were compared with the results of previous works. Energy dissipation per unit length of the roughened chute was 7 to 38% greater than that of the smooth chute (without roughness).

One of the most effective strategies for energy dissipation of hydraulic structures is hydraulic jump. The position of hydraulic jump play an important role in design of stilling basin. In this study, hydraulic jump in ogee spillways were simulated by using fluent software. The governing equations were solved through finite volume method and the standard model was applied for estimating the turbulence flow. The equations were discretized in structured mesh accommodate the well-defined boundaries and the volume of fluid (VOF) method was introduced to solve the complex free-surface problem. The study examined the effect of increasing the discharge and the slope on the hydraulic jump position and lentgh. the results suggest that increasing the slope and discharge caused the spatial delay in hydraulic jump. It was found that in ogee spillway with a constant slope, the hydraulic jump length increases up to 120% when the discharge increases. Additionally, for a certain discharge and a constant length of spillway, increasing the slope of spillway decreases the hydraulic jump length up to 43%.

Progressive Web Apps (PWA) are a new web development paradigm that is being used in a variety of web apps. With this new paradigm, web apps can provide features similar to native apps, blurring the line between websites and native apps. However, new challenges may arise during the development of PWAs. Understanding the issues that developers may encounter while developing PWAs is necessary due to their widespread interest. These issues have not yet been extensively identified and analyzed in the existing research. Therefore, this research aims to fill this knowledge gap by conducting an empirical study of PWA-related questions on Stack Overflow (SO), a well-known website for developers. Our process involves obtaining a list of PWA tags and extracting 8,654 questions related to PWAs from SO. To comprehend the issues being discussed by PWA developers on SO, we use topic modeling. After that, we analyze their characteristics (such as the challenges’ popularity and difficulty). Our research shows that developers encounter eleven challenges, including the Service Worker lifecycle. Our study deepens our understanding of PWA development issues and provides recommendations for researchers, educators, and developers to promote PWA adoption.

Construction of stilling basins downstream of hydraulic structures is a common tool to dissipate the excess energy created by exit supercritical flows from the outlets. The length of the stilling basin and its construction costs are the factors which should closely be considered by designers to select the most economical structure. Saint Anthony Fall (SAF) stilling basin is one of the compact and short length pools which are utilized in downstream of high velocity exit flows. The efficiency of energy dissipation of this type of stilling basins would be too high despite to the short length of the pool which is the consequence of appurtenances encountered with this basin. Generally, to design this stilling pools the average flow characteristics (such as mean velocity, hydrostatic pressure ,...) are used which reflects some uncertainties due to presence of high turbulent and fluctuating flow in the reach which is to be considered for careful clarifications. In this research a stilling basin of SAF type has been constructed in a glass walled flume and electronic devices been used to take the precise measurements of actual pressure prevailed around the chute blocks of the basin. The results showed that the mean pressure is not in accordance with hydrostatic distribution and varies inversely with entering supercritical flow and directly with submergence ratio of hydraulic jump formed in the basin. It was also revealed that the variation of mean pressure at different faces of the chute blocks follows a different trend at each face.