Using energy dissipaters on the soled aprons downstream of head structures is the main technique for accelerating hydraulic jump formation and dissipating a great amount of the residual harmful kinetic energy occurring downstream of head structures. In this paper, an experimental study was conducted to investigate some untested shapes of curved dissipaters with different angles of curvature and arrangements from two points of view. The first is to examine its efficiency in dissipating the kinetic water energy. The second is to examine the most effective shape and arrangement obtained from the aforementioned step in enriching the flow with dissolved oxygen for enhancement of the irrigation water quality. The study was held in the irrigation and hydraulic laboratory of the Civil Department, Faculty of Engineering, Assiut University, using a movable bed tilting channel 20 m long, 30 cm wide, and 50 cm high, using 21 types of curved dissipaters with different arrangements. A total of 660 runs were carried out. Results were analysed, tabulated and graphically presented, and new formulas were introduced to estimate the energy dissipation ratio, as well as the DO concentrations. Results in general showed that the dissipater performance is more tangible in dissipating the residual energy when the curvature is in the opposite direction to that of the flow. Also, the energy loss ratio increases with an increase in curvature angle (θ), until it reaches (θ = 120°), then it decreases again. The study also showed that using three rows of dissipaters give nearly the same effect as using four rows, concerning both the relative energy dissipation and dissolved oxygen content. So, it is recommended to use three rows of the curved dissipater with the angle of curvature (θ = 120°) in the opposite direction to that of the flow to obtain the maximum percentage of water energy dissipation downstream of head structures, and maximum dissolved oxygen content too
One of the most important problems Egypt is facing nowadays is saving and controlling the limited available quantity of water and its quality for irrigation and other purposes. Such goals may be achieved through different types of diversion head structures across the river and in the entrance of other carrying canals. The construction of diversion head structures, which usually causes many technical problems, should have the objective of solving and overcoming to protect the structure from failure. The main problem occurs downstream. Such structures have the harmful effect of converting the potential energy gained in the upstream side to a kinetic energy in the downstream side. This energy must be dissipated shortly and safely as near as possible to the head structure to avoid its destructive effect. The hydraulic jump is the most effective tool for the dissipation of water energy, accelerating the forming of the hydraulic jump downstream such structures became essential for achieving our main goal. Using energy dissipaters on the soled apron in the downstream side of the structures was the main technique for accelerating the hydraulic jump formation and dissipating great amount of the residual harmful kinetic energy occurring downstream head structures. So early, many researchers investigated different types, shapes, and arrangements of such dissipaters to evaluate its efficiency in dissipating the water energy and accelerating the forming of the hydraulic jump. In fact, in our present study we will try to investigate some other shapes of energy dissipaters, which have not been studied enough, by evaluating its positive technical impact on: (i) percentage value of dissipating kinetic water energy; (ii) percentage value of increasing the dissolved oxygen (DO) content in the irrigation water, and improving its quality. The study is proposed to be held in the irrigation and hydraulic laboratory of the Civil department, Faculty of Engineering, Assiut University, using a movable bed tilting channel 20 m long, 30 cm wide, and 50 cm high, using fourteen types of curved dissipaters with different arrangements as shown in Table 2. It is worth mentioning that, in this first part of our paper, we will introduce a comparative analysis for the efficiency of different types of energy dissipaters available in the literature review. The most effective types of the previously studied dissipaters will be put in a comparison with our new dissipaters from the two above mentioned points of view, and the results will be presented in the second part of this paper later.
The geometry of weirs is a prime factor influencing hydraulic performance and accuracy. One of the geometric components of weirs, is the situation of its top corners, are they sharp or rounded, and what is the most suitable radius of such rounding curves? The present study was conducted to examine the effect of using five different radius of curvature for both the upstream and downstream top corners of a clear over-fall weir on its hydraulic performance and accuracy. Eleven models of wooden weirs were shaped and prepared with five different values of rounding curvature. The prepared weir models were located in a laboratory tilting flume of 13.50 m length, 0.30 m width, and 0.30 m depth. The study was carried out in the Irrigation and Hydraulic Laboratory of the Civil Department, Faculty of Engineering, Assiut University, Egypt. A discharge ranging from 2.0 to 22.0 dm3 s−1 was used, and through 66 experimental runs, all the necessary hydraulic parameters were measured, and recorded. The obtained data were tabulated, analyzed, plotted, and technically discussed. The main results and obtained conclusions proved that when the front weir top edge is curved the discharge coefficient increases up to 8%. Also, when both front, and behind weir top edges are curved the discharge coefficient increases up to 14%. At the same time the discharge coefficient has a maximum value when the radius of curvature in upstream and downstream top corners equals 20% of the height of the weir.
In such problematic water situation in Egypt, control and saving of the available limited quantity takes great importance from both technical and national points of view. In addition to all the well-known traditional reasons of the problem such as pollution, over usage, and bad traditions of dealing with water, a new very important reason is added nowadays, called “Climate Changes” which has a direct impact on sea water rising, that causes a serious attack of the salt water to the fresh water especially in River Deltas., Not only the surface water, but also the ground water. Since that process proved some acceleration, several investigations have recently considered the worst impacts of climate change and sea water level rise on sea water intrusion. Most of them have revealed the severity of such problem, and the significance of the land movement of the dispersion zone under the sea water level rise situation. In this paper, we try to introduce a technical review and study for the most popular studies concerning our topic, and its most important conclusions, as an approach for preparing the Ph.D. thesis about the Nile Delta water equilibrium in the light of the expected Mediterranean Sea water level rise. Nile Delta, which located between Damietta Branch on the East, and Rosetta Branch on the west, occupies about 20000 square kilometers of the most rich, productive land in Egypt. About 50% of Egyptian population live in that area, agriculture is the main human activities on them, so water is the prime factor in their life, and their agriculture investments. The great amount of this investment depends on the ground water, which faces a serious challenge due to, two reasons, first, is the overuse, and over pumping, while the second is the attack of the salt water due to the Mediterranean Seawater level rise, because of the climate changes. These two reasons must be overcome, if the first reason can be controlled by law, and technical roles, the second reason needs intensive studies and investigations concerning the interaction between seawater and fresh ground water.
The compatibility between the needed structural designed dimensions of the irrigation works and the dimensions of the water stream or the canal in which the irrigation work will be located has a great importance from more than one point of view. As it is well known, the main aim of the designer of such works is to reach the optimum design for maximum performance efficiency with economical cost, and minimize negative technical impacts that may be harmful to the safety of the whole work. Since the complete suitability between the obtained designed dimensions of the different construction elements of the work, and the original properties and dimensions of the canal in which the work will be constructed, is rarely occurring. The designer always has to make some changes in the original engineering properties and dimensions of canals, such as bed width, bed level, and/or inside side slope, to reach the needed suitable compatibility between the structural design and the natural original canal cross section. For the economical purposes, the design always needs less width of the work, than the width of the bed of the original stream cross section, so a contraction may be needed where the work will be constructed; the literature indicated that, such a contraction must not be less than 0.6 of the original bed width. That contraction, of course, has a direct impact on the different hydraulic parameters, such as water depth, velocity, and flow regime in the location of the work. Changes of such hydraulic parameters may exceed their safe permissible values, and so the whole structure may face some dangerous situations, which must be overcome. In this paper, we present a technical survey of the previous research concerning canal width contraction, with the needed technical comments, and comparisons as a logical approach for a master-thesis under the same title.
Bahr Youssef (B.Y) is a semi-natural branch canal connecting the River Nile with Fayoum depression, in the desert immediately to the west of the Nile Valley, about 92 kilometers southwest of Cairo, for irrigation purposes of El-Minya, El-Fayoum, Bani-Swif, and Giza governorates. The area served by Bahr Youssef reaches about 850.000 feds in the Middle Egypt, out of 1.650.000 feds served by the Ibrahimeya carrier canal, which branches from the River Nile's at Assiut barrage, and extends northward for 55 kilometers, until Dayrut city. In Dayrut; “Ibrahimeya” canal bifurcates into seven carrier canals, (Bahr Youssef is one of them,) through Dayrut Group of regulators. Bahr Youssef suffers from, meandering phenomenon, in many reaches, occurred with all its harmful and destructive effects. As meanders are the direct result of erosion-deposition processes occur in such flatty reaches with hydraulically unstable sections, our effort here is directed for studying the existing geometric, and hydraulic conditions of some representative reaches of Bahr Youssef, to evaluate the size of the problem through intensive field measurements, and to verify the available predicting techniques and theories by comparison with the obtained measured values. Introducing an acceptable, effective and easy method, which can be used for an accurate estimation of the meandering phenomenon, is the main objective of this study. This was achieved through reviewing and assessment of the available predicting techniques, and evaluating their liability, validity, and suitability through the comparison with the field collected measurements.
The problematic water situation in Egypt, as one of the River Nile basin countries, has been heightened by the harmful effects of the Grand Ethiopian Renaissance Dam (GERD) on Egypt’s share of the Nile water. In the light of this Egyptian attention was directed towards a study of worldwide transboundary water problems, in order to find the most effective methods for dealing successfully with water shortage problems in basin countries. The present study focuses on the most successful experiences in the management and development of international river basins worldwide, as well as studying the possibility of implementing these experiences in other basins, especially the River Nile basin. The study showed that overcoming the water scarcity problems in Egypt and increasing the Nile water yield for all the basin countries can be achieved, first of all through serious cooperation among all the basin countries for minimizing the huge water losses from the river (more than 1480 Billion Cubic Metres per year which represents roughly 90% of the whole basin income), and secondly to make use of the most successful technical and political experiences that have been implemented in other international river basins mentioned in the present study.
The dimensions of many water streams, which satisfy proper hydraulic conditions, may not be compatible with the designed dimensions of an irrigation work that needs to be constructed in some locations. The design requirements of such irrigation works may involve a contraction in the channel width in the required location. This contraction, of course, affects different flow properties and the scour hole formed downstream of these structures. Therefore, the present experimental study aims to investigate the effect of the transition angle and the contraction on the flow properties and on the scour phenomenon downstream water structures. Through 460 experimental runs, carried out on 20 experimental models, the study proved that, for an efficient hydraulic performance and economic design, the best transition angle (θ) for the approaches of water structures is 30° with a relative contracted width ratio (r = b/B) not less than 0.6.