Dam and powerhouse operation sustainability is a major concern from the hydraulic engineering perspective. Powerhouse operation is one of the main sources of vibrations in the dam structure and hydropower plant; thus, the evaluation of turbine performance at different water pressures is important for determining the sustainability of the dam body. Draft tube turbines run under high pressure and suffer from connection problems, such as vibrations and pressure fluctuation. Reducing the pressure fluctuation and minimizing the principal stress caused by undesired components of water in the draft tube turbine are ongoing problems that must be resolved. Here, we conducted a comprehensive review of studies performed on dams, powerhouses, and turbine vibration, focusing on the vibration of two turbine units: Kaplan and Francis turbine units. The survey covered several aspects of dam types (e.g., rock and concrete dams), powerhouse analysis, turbine vibrations, and the relationship between dam and hydropower plant sustainability and operation. The current review covers the related research on the fluid mechanism in turbine units of hydropower plants, providing a perspective on better control of vibrations. Thus, the risks and failures can be better managed and reduced, which in turn will reduce hydropower plant operation costs and simultaneously increase the economical sustainability. Several research gaps were found, and the literature was assessed to provide more insightful details on the studies surveyed. Numerous future research directions are recommended.
The simulation have been made for 3D flow structure and heat transfer with and without
longitudinal riblet upstream of leading edge vane endwall junction of first stage nozzle guide vane .The research explores concept of weakening the secondary flows and reducing their harmful effects.Numerical investigation involved examination of the secondary flows ,velocity and heat transfer rates by solving the governing equations (continuity, Navier -stokes and energy equations ) using the known package FLUENT version (12.1).The governing equations were solved for three dimentional, turbulent flowe, incompressible with an appropriate turbulent model (k-ω,SST) .The numerical solution was carried out for 25 mode
... Show MoreGreen areas are an essential component of city planning, as they serve as an outlet for them to spend their free time, in addition to the environmental role that these green areas play in improving the city’s climate by purifying the air and beautifying the city. The study’s problem is summarized in identifying the appropriateness of the current spatial distribution of green areas in the city of Najaf with the current population densities and the pattern in which green areas are distributed using GIS and knowing the per capita share of those green areas in the city, the research assumes that the inconsistency of spaces between regions Green and residential neighbourhoods need to c
The purpose of this study was to examine the histological structure of the kidney in snake Eryx gaculus gaculus. In present study, the snakes were collected from the city of Baghdad and transferred to the laboratory where their kidneys were dissected out. The samples were then processed to be prepared for histological examination microscopial observations showed that there is no border between the cortex and medulla regions of kidney. The kidney consists of nephrons which are composed of glomerulus surrounded by Bowman’s capsule; the other segments are proximal tubule, distal tubule and connecting tubule. The epithelial tissue lining of these segments simple cuboidal tissue.
Abstract
The nuclear structure of 28-40Si isotopes toward neutron dripline has been investigated in framework of shell model with Skyrme-Hrtree-Fock method using certain Skyrme parameterizations. Moreover, investigations of static properties such as nuclear densities for proton, neutron, mass, and, charge densities with their corresponding rms radii, neutron skin thicknesses, binding energies, separation energies, shell gap, and pairing gap have been performed using the most recent Skyrme parameterization. The calculated results have been compared with available experimental data to identify which of these parameterizations introduced equivalent results with the ex
... Show MoreThe goal of this study was intend to study the effects of induced
thyrotoxicosis on the histological structure of submandibular gland.
Two groups of mature albino mice wen: used, the first group was injected (subcutaneous) daily with (0.2_0.4)ml norma] salinfor 11 days and used as control group, while the second group was injected daily wi th L_thyroxin (T4) 0.2mg /Kg (subcutaneous) for l l days.
At the end of the treatment , supmandibular glands were processed for light microscopic examination .
The result.s have shown the presence of degenertaive changes of major submandibular acini cells in anima
... Show MoreA descriptive evaluation study is conducted on primary health care centers in Baghdad City in order to
evaluate the organization structure as component of quality improvement of maternal and child health promotion
from April 10th 2012 to May20th 2013. A total of (22) primary health care centers. Study instrument was
comprised of three questionnaires and overall items included in these questionnaire were (65) items. Data are
collected through the utilization of the developed questionnaire and the interview technique as means of data
collection. Data are analyzed through the application of descriptive statistical data analysis methods which
includes the measurement of the frequencies, percentages, and computation of mean
This study was aimed to explore the impact of social concepts about tribe, clan and women, on internal audit performance. These concepts are considered to be components of the organizational culture and performance of internal audit practice, with respect to the individual and collective performance within the institution. The study, furthermore, was intended to investigate and understand the role of the organizational culture of the tribal, clan and women components with regard to their role in society, in Qatar.
To achieve these objectives, the researcher followed the descriptive analytical approach, using a questionnaire directed to experts and staff working in the banking sector, with the view to test
... Show MoreThe objective of this work is to investigate the performance of a conventional three phase induction motor supplied by unbalanced voltages. An effort to study the motor steady state performance under this disturbance is introduced. Using per phase equivalent circuit analysis with the concept of symmetrical components approach, the steady state performance is theoretically calculated. Also, a model for the induction motor with the MATLAB/Simulink SPS tools has been implemented and steady state results were obtained. Both results are compared and show good correlation as well. The simulation model is introduced to support and enhance electrical engineers with a complete understanding for the steady state performance of a fully loaded induc
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