The dimensions of many water streams, which satisfy the proper hydraulic condition, may not be compatible with the designed dimensions of an irrigation work needed to be constructed in some locations. The design requirements of such irrigation works may need to make a contraction in the channel width in the location of constructions. This contraction, of course, affects the different flow properties and the scour hole formed downstream these structures. So, the present experimental study aims to investigate the effect of the transition angle and the contraction ratio on the flow properties and on the scour phenomenon downstream water structures. Through 454 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 contraction ratio (r) not less than 0.6.

In the conditions of severe climatic changes that are sweeping the world now, causing many problems, of which high surface water levels, torrential rains and floods are among the most dangerous phenomena. Since dams are the most engineering and structural protection means that engineers resort to, to protect against these dangers in such circumstances, not to mention the other important uses of dams such as storing water for irrigation purposes, generating electricity, feeding the underground reservoir, or diverting flow paths for any engineering purpose. Dams are usually classified on the basis of several considerations, including solid dams of different types, and flexible dams. Flexible dams, which are sometimes called earth dams, are of a special nature as they consist mainly of loose materials of a special porous nature and different ratios of interspaces that allow water to pass through them and penetrate the dam body in different proportions, which, if not prevented or avoided, may lead to the collapse of the dam body. In the present study a numerical analysis of seepage through zoned earthen dams is introduced, as they are the most popular type of flexible dams, to clarify the behavior of the streamlines of the seepage water through the body of such type of dams with different types of used soil of filling materials. Decreasing the relative permeability coefficient between the inner and transition zones up to 0.001 caused a significant decrease in the different seepage properties, after that, the effect was minor.

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.

This paper is intended to determine the space-charge-free field on the stressed discharge wires’ surface, the corona-onset voltage of wire-duct electrostatic precipitators (ESP) as influenced by the variation of the velocities of the incoming flow gases. The corona current-voltage (I-V) characteristics of wire-duct ESP is calculated under varying velocities of incoming flow gases. The calculation is made using the improvement of Deutsch’s Method. The method is endorsed by an iterative process to determine an estimate for the underlying dissemination of the charge density close to the surface of the stressed discharge wire(s). The electric potential, field, space-charge density in the interelectrode spacing, corona onset voltage and current-voltage characteristics of the precipitator are considered. Besides, the effect of gradually increase of the velocities of incoming flow gases, changing the number of stressed wires and …

Abstract: Several models of multi-criteria decision-making (MCDM) have identified the optimal alternative electrical energy sources to supply certain load in an isolated region in Al-Minya City, Egypt. The load demand consists of water pumping system with a water desalination unit. Various options containing three different power sources: only DG, PV-B system, and hybrid PV-DG-B, two different sizes of reverse osmosis (RO) units; RO-250 and RO-500, two strategies of energy management; load following (LF) and cycle charging (CC), and two sizes of DG; 5 and 10 kW were taken into account. Eight attributes, including operating cost, renewable fraction, initial cost, the cost of energy, excess energy, unmet load, breakeven grid extension distance, and the amount of CO2, were used during the evaluation process. To estimate these parameters, HOMER® software was employed to perform both the simulation and optimization process. Four different weight estimation methods were considered; no priority of criteria, based on a pairwise comparisons matrix of the criteria, CRITIC-method, and entropy-based method. The main findings (output results) confirmed that the optimal option for the case study was hybrid PV-DG-B with the following specification: 5 kW DG, RO-500, and load following control strategy. Under this condition, the annual operating cost and initial costs were $ 5546 and $ 161022, respectively, whereas the cost of energy was 0.077 $/kWh. The excess energy and unmet loads were 40998 and 2371 kWh, respectively. The breakeven grid extension distance and the amount of CO2 were 3.31 km and 5171 kg per year, respectively. Compared with DG only, the amount of CO2 has been sharply reduced by 113939 kg per year.

A new interconnected translational manipulator is proposed. It is the only interconnected manipulator that makes such motion using revolute joints and three rotary actuators. Rotary joints and actuators are favored practically than their linear counterparts due to their lower price, lower size of installation and higher reliability. The configuration of the proposed manipulator allows it to maintain, to a large extent, the combined merits of serial and parallel manipulators. In contrast to all other existing interconnected manipulators, the proposed manipulator has free-internal-singularity workspace. Using a practical proposed methodology, a balancing system is developed that reduces dramatically the power consumption and facilitates using small-sized-motors. The mobility analysis is carried out using a newly developed methodology suitable for interconnected manipulators. Closed forms for position and velocity kinematics …

Nowadays, new generations of building envelope need to manage the energy exchange between outdoor and indoor environment responsively and save the building energy. A significant amount of solar heat gain in buildings comes through the windows. The transparent envelope also must answer to visual requirements allowing for external vision but guarantying comfort conditions. In this framework, this article aims to test numerically the thermal performance of a new design of multifunctional glazed window combining the most recent technologies used in building envelopes. Five distinct window designs combing phase change material (PCM), vacuum glazing (VG), photovoltaic (PV), and air cavity were numerically tested for hot weather conditions. The proposed window designs slide inside the wall of the building. A comprehensive transient Multiphysics model coupling the thermo-electric model of the PV …

High penetration of intermittent wind-turbine generation (WTG) into electric distribution system along with large variations of load demand introduce many problems to the system such as high power losses, voltage sag, and low voltage stability. To mitigate such problems, the distribution system is supported by superconducting magnetic energy storages (SMESs). This paper is aimed at determining the optimal placement and sizing of WTGs and SMESs in a distribution system using a proposed multi-objective-function based optimization method. The method is a hybrid one being based on an efficient algorithm called Equilibrium Optimizer (EO) along with loss sensitivity factor (LSF). The weighted-sum multi-objective function (IMO) is formulated for simultaneous minimization of energy-loss and voltage-deviation as well as enhancement of voltage-stability as indices characterizing the distribution system performance. The weight factors are no longer assumed or left open to the preferences of the decision maker. They are computed while optimizing the indices of the IMO in order to determine the optimal placement and sizing of WTGs and SMESs. The proposed method for optimal placement and sizing of WTGs and SMESs is tested and validated on the standard IEEE 33-bus distribution system with time-varying voltage-dependent load models including residential, industrial, commercial, and mixed loads as well as variable wind-speed. The results obtained using EO algorithm are compared with those obtained by particle swarm optimization (PSO) and genetic algorithm (GA) to validate the effectiveness of EO. The numerical results and simulations imply that the combination of WTGs and SMESs can successfully achieve minimization of energy-loss and voltage-deviation as well as enhancement of voltage-stability, and thereby significantly improve the performance of distribution system.

The charge simulation technique (CST) was applied for computing the electric field in long space-charge-free rod-to-plane gaps with G (=gap-spacing to rod-radius) ratio in the range of 50-500. In this article, a new formation of CST is proposed for computing the electric field in short positively stressed rod-to-plane gaps characterized by G in the range of 2-160 and gap spacing up to 8 cm, provided that the gap can accommodate space charges. This is a prerequisite for computing the inception voltage of different corona modes, including burst pulses (BP), onset streamers (OS), and positive glow (PG). The criteria developed before for computing the inception voltage of BP and OS are refined for short rod-to-plane gaps. However, the inception criterion for PG cannot be extended to short gaps. A method is proposed for calculating the inception voltage of PG in short rod-to-plane gaps in the air at room temperature. The initiatory electrons for burst avalanches are produced by photoionization inside the ionization zone rather than by detachment of negative ions as experienced in long gaps. The resulting BP merges in time to form the steady glow at the rod surface in conformity with Loeb's postulate. The computed inception voltage of BP, OS, and PG agreed reasonably with those measured experimentally for short rod-to-plane gaps.