Papers by Berge Djebedjian
MEJ. Mansoura Engineering Journal
MEJ. Mansoura Engineering Journal, 2021
MEJ. Mansoura Engineering Journal, 2021
MEJ. Mansoura Engineering Journal, 2021
The present paper investigates experimentally the incompressible turbulent flow in a 180° curved ... more The present paper investigates experimentally the incompressible turbulent flow in a 180° curved diffuser of rectangular cross section. A three-hole probe and pressure taps have been used to measure the mean velocities and static pressures. The turbulent flow in the diffuser has been analyzed numerically using the time-averaged Navier-Stokes equations. The numerical solutions of the elliptic partial differential equations written for a body fitted coordinate have been obtained using the standard and non-equilibrium k-e turbulence models. The non-equilibrium k-e model takes into account the streamline curvature. The objective of the present investigation is to study the turbulent flow characteristics in a 180° curved diffuser in order to improve pressure recovery of this type of diffusers.
Les diffuseurs annulaires sont employes a l'aval des turbomachines pour accroitre la pression... more Les diffuseurs annulaires sont employes a l'aval des turbomachines pour accroitre la pression statique et reduire la vitesse de l'ecoulement avec un minimum de pertes. Ces diffuseurs sont pourvus d'un moyeu central et de tirants, mais ont des formes de veines differentes. La presente revue examine ces dispositifs a partir des etudes publiees. Les effets des conditions d'entree et les methodes generales utilisees pour ameliorer la performance de ces diffuseurs et pour diminuer les effets des sillages des tirants sont analyses.
iwtc.info, 2006
* Mechanical Power Engineering Department, Faculty of Engineering, Mansoura University, El-Mansou... more * Mechanical Power Engineering Department, Faculty of Engineering, Mansoura University, El-Mansoura, Egypt ** Damietta Drinking Water Company, Damietta, Egypt E-mail: bergedje@mans.edu.eg , ashrafyasseen@yahoo.com , mrayan@mans.edu.eg
Proceedings of …, 2006
The development of non-conventional water resources in Egypt is essential in order to respond to ... more The development of non-conventional water resources in Egypt is essential in order to respond to the continuously increasing demand. The most advanced and charming desalination system is the reverse osmosis (RO) system. In this paper, the effect of the feed water temperature, ...
… of the Tenth International Water Technology …
* Mechanical Power Engineering Department, Faculty of Engineering, Mansoura University, El-Mansou... more * Mechanical Power Engineering Department, Faculty of Engineering, Mansoura University, El-Mansoura, Egypt ** Damietta Drinking Water Company, Damietta, Egypt E-mails: bergedje@mans.edu.eg , ashrafyasseen@yahoo.com , mrayan@mans.edu.eg
Volume 3: Materials and Joining; Pipeline Automation and Measurement; Risk and Reliability, Parts A and B, 2006
This paper presents a new adaptive penalty method for genetic algorithms (GA). External penalty f... more This paper presents a new adaptive penalty method for genetic algorithms (GA). External penalty functions have been used to convert a constrained optimization problem into an unconstrained problem for GA-based optimization. The success of the genetic algorithm application to the design of water distribution systems depends on the choice of the penalty function. The optimal design of water distribution systems is a constrained non-linear optimization problem. Constraints (for example, the minimum pressure requirements at the nodes) are generally handled within genetic algorithm optimization by introducing a penalty cost function. The optimal solution is found when the pressures at some nodes are close to the minimum required pressure. The goal of an adaptive penalty function is to change the value of the penalty draw-down coefficient during the search allowing exploration of infeasible regions to find optimal building blocks, while preserving the feasibility of the final solution. In...
In this paper, a methodology is developed for optimization of the reverse osmosis (RO) desalinati... more In this paper, a methodology is developed for optimization of the reverse osmosis (RO) desalination system performance. The solution-diffusion model is used for the modeling. The optimization of RO systems is achieved by the genetic algorithms (GA) technique. The objective function is taken as the maximization of permeate volumetric flow rate. The optimization problem is to find the best pressure difference across the membrane which maximizes permeate volumetric flow rate and fulfill the permeate concentration constraint. The used constraint is that permeate concentration to be less than a desired value. A computer program was written in FORTRAN, GARO program (Genetic Algorithm Reverse Osmosis) to include the methodology. A binary-coded micro-genetic algorithm was linked with the equations describing the RO system performance. The methodology was tested on a real RO desalination plant in Nuweiba City, Egypt. Results from application of the GARO program on this plant have shown that ...
A theoretical investigation on the performance prediction of solar still is presented in this pap... more A theoretical investigation on the performance prediction of solar still is presented in this paper. A solar still of conventional type is considered. The mathematical model is based on time-averaged Navier-Stokes equations. The effect of the variable fluid properties is taken into consideration by using a mixture of air and vapour in the still. A steady state twodimensional approach with constant temperature boundaries is considered. A discretization schema with finite-difference technique is adapted. The SIMPLER (Semi-Implicit Method for Pressure-Linked Equations Revised) methodology is used. The grid size independence solution is checked for convergence. The numerical results show clearly different zones of circulation with reverse velocity on the inside still glass cover. The numerical results prove the necessity to undertake a numerical investigation before the sizing of solar still. The objective of the present investigation is to present a mathematical model in order to impro...
The paper presents the water network optimization by selecting the optimal pipe diameters for ste... more The paper presents the water network optimization by selecting the optimal pipe diameters for steady state flow and water hammer. The optimization method used is the Genetic Algorithm (GA). The GA’s have been used in solving the water network optimization for steady state conditions. The GA is integrated with the Newton-Raphson program and a transient analysis program to improve the search for the optimal diameters under certain constraints. These include the minimum allowable pressure head constraints at the nodes for the steady state flow, and the minimum and maximum allowable pressure heads constraints for the water hammer caused by the pump power failure. The application of the computer program to a case study shows the suitability of the method to find the least cost in a favorable number of function evaluations. This technique can be used in the first stages of the design of water distribution networks to protect it from the water hammer damages. The technique is very economic...
The paper presents the water distribution systems optimization by selecting the optimal pipe diam... more The paper presents the water distribution systems optimization by selecting the optimal pipe diameters for water hammer transients. The optimization method used is the Genetic Algorithm (GA). The GA’s have been used in solving the water network optimization for steady state conditions. The GA is integrated with the steady state hydraulic analysis program and a transient analysis program to improve the search for the optimal diameters under certain constraints. These include the minimum allowable pressure head constraints at the nodes for the steady state flow, and the minimum and maximum allowable pressure heads constraints for the water hammer. Three cases are studied including the following causes of water distribution transients: changes in water demands at the nodes, sudden valve closure and pump power failure. The application of the computer program to the studied cases shows the suitability of the method to find the least cost in a favorable number of function evaluations. Thi...
Due to the continuously increasing demand of fresh water in the desert and remote areas, the deve... more Due to the continuously increasing demand of fresh water in the desert and remote areas, the development of non-conventional water resources in Egypt is essential. The most advanced and charming desalination system is the reverse osmosis (RO) system.
Accelerated growing population and migration to urban areas in developing countries have resulted... more Accelerated growing population and migration to urban areas in developing countries have resulted in a vital need for the establishment of protected source water and modern, well-maintained drinking-water treatment plants to disseminate potable water to residents. While the challenge in the developed world is mainly to prevent existing infrastructure from decay and to initiate a transition from the disposal-oriented regimes toward more sustainable approaches with a focus on reuse options, the situation is more complex in developing countries. Developing countries suffer from economic problems and are often struggling with insufficient infrastructure and low water supply and sanitation coverage, particularly in rapidly growing urban slum settlements, with significant consequences, especially regarding public health. In this chapter, we discuss the urban water cycle and water consumption, the challenges facing urban water management in developing countries including climate change, th...
Numerical calculation of turbulent separated flow characteristics in an axial steam turbine engin... more Numerical calculation of turbulent separated flow characteristics in an axial steam turbine engine exhaust diEuser having 22 cylindrical struts in its passage is presented. The used numerical code is based on the resolution of the averaged Navier-Stokes equations and a finite volume formulation. Turbulence is simolated by the k-s model and the Reynolds stress model. Computations are performed for turbulent flow in a sector of l/S of exhaust dif&ser (2 struts / 45’ of the total geometry). In this simplified geometry, the presence of 6 struts is neglected. The comparison between the numerical results with the experimenta.l data reveals an important difference for the static pressure recovery coefficient. A small part of this difference is attributed to numericaI reasons: turbulence model, discretization scheme, wall function, swirl treatment in the model,... etc. These numerical factors are already observed in previous work concerning the different types of diffusers. A large part of ...
The present study investigates numerically the twoand three-dimensional incompressible turbulent ... more The present study investigates numerically the twoand three-dimensional incompressible turbulent flow through two types of square sectioned U-bend duct flows with mild and strong curvatures. Calculations have been carried out using the flow analysis program FLUENT. Five turbulence models are implemented, namely: Standard kmodel, Renormalizationgroup (RNG) kmodel, Realizable kmodel, kmodel and Reynolds stress model (RSM). All models managed to mimic the general flow patterns and to predict a later separation position than the experiment. The reattachment lengths predicted by all models are overpredicted. All models give more reliable results in the 3-D analysis in comparison with 2-D. The results showed that using the Reynolds Stress model allowed better predictions compared to the k-ω two-equation models. More refined turbulence models are thus necessary when strong curvature affects. The eddy viscosity models must relate the Reynolds shear stresses to velocity gradient in order to ...
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Papers by Berge Djebedjian