فهرست مطالب مجید احسانی

In the present paper, owing to importance of seeking a proper hydraulic response evaluation of the rubble mound structure against the incident waves, a systematic study has been carried out to investigate the wave overtoping on rubble mound breakwater. To gain this goal, numerical simulation was conducted an apposite range of sea state condition and geometrical parameters to investigate wave overtopping on rubble mound breakwater. In the current research, the effects of environmental parameters such as wave height, wave period, water depth and also a diversity of geometrical parameters including berm width, front slope and crest freeboard over the overtopping discharge, have been individually scrutinized and studied. The Flow-3D software has been used to simulate and solve the governing equations on the flow. The numerical results have been validated using experimental results. The computed results of wave overtopping discharge over parsian breakwater agree well with the physical model results. The present study, results showed that an increase in wave height, wave period and water depth would increase the wave overtopping on crest breakwater. Also, results outlined by enhancing the structural parameters like berm width and crest freeboard would increase the wave overtopping. As the slope gets steeper, the wave overtopping will be on a striking increase and strongly run-up level will be increased.

Porous breakwater structures are widely used as protection against waves for ports and harbors as well as for general coastal protection. Often the breakwater structure is designed as a porous structure that allows water to flow through the structure while the wave energy is removed. These structures prevent coastal erosion and ensure safe and functioning harbors. As such, it is of high importance that these structures remain stable under extreme wave action. On the other hand, regarding the high complexity of wave interaction with porous structures, it is required to provide a rich understanding and conduct fundamental studies on the mechanism of rubble mound breakwaters subjected to incident waves. The existing literature review on wave interaction with rubble mound breakwaters reveals two mechanisms inside the porous media of such structures and outside the structure on the armor layer. Both could make destructive forces affecting the structure’s stability. In the present study, the stability of the multi-layer berm breakwater has been studied by considering the effect of run-up/run-down flow on the armor layer of a breakwater and, consequently, the flow inside the porous media as it gets filled and empty during wave run-up and run-down. Both numerical and experimental methods are used to investigate the flow inside and outside the multi-layer berm breakwater. Validation of numerical results is conducted through the use of experimental results, including the water level fluctuation outside the structure and also the water pressure variations inside the breakwater. The Flow-3D software has been used to simulate and solve the governing equations on the flow. FLOW-3D numerically integrates RANS (Reynolds Average Navier-Stokes) equations using the Volume of- Fluid (VOF) method to track the free surface. It has been thoroughly tested for coastal hydrodynamics problems. Various turbulence models are available, and the results presented here are based on the RNG turbulence model. The time series of pressure variation in the porous media indicates that as the flow infiltrates, the created pressure damping and also its variation at a constant elevation have been significantly decreased due to energy dissipation during the infiltration. Moreover, at the maximum run-down and exfiltration process, the created flow from inside to outside would be approximately perpendicular to the structure’s slope at about the maximum run-down elevation. Results reveal that the pressure gradient due to changes in the flow field of porous media would lead to a pressure force toward the outside during the run-down and a pressure force toward the inside during the run-up. It has been found that the positive pressure gradient force toward outside during the run-down and also the perpendicular force of flow during the exfiltration occurred simultaneously and acted as an active force to destabilize the stones. More to the destabilizing mechanism of stones, the effect of flows occurred during the run-up, and run-down on the armor layer have been investigated using the recorded images during the experimental tests.

The presence of halite karst systems in dam reservoirs can be one of the crucial sources of pollutants for the water resources. Karstic regions are those with dissolving caves. If dam is constructed in the regions with reactive rocks it is likely to be endangered by karst phenomenon, dissolution and corrosion of current waters. construction of dams and reservoirs in these formations are associated with high risk. Comprehensive and accurate understanding of the salt dissolution processes facilitates the description of salt karst formations dissolution process in dam reservoirs.This research was performed based on three basis: field studies, experimental investigation and numerical modeling. For determination of dissolution coefficient, the physical model of reservoir was built in form of trapezoidal channel and samples of salt rock in the reservoir were used in the physical model of karst formation. This model was implemented in different conditions and the results of dissolution amount and salt concentration were measured for different time scales. At the next stage, the physical model was simulated in numerical model for determining of dissolution coefficient. The numerical model ran with different dissolution coefficients and results were compared with experimental results. With this comparison and adaptation of results, the dissolution rate of halite karst determined and then used in the numerical simulation of main reservoir. With simulation of main reservoir using dissolution coefficient obtained from laboratory study, the effect of salt karst formation on reservoir’s water quality was analyzed. The influences of effective parameters such as dissolution rate, air temperature, discharge and relative humidity on the water quality of dam reservoir were studied along with carrying out a wide range of sensitivity numerical analysis. To this purpose, a versatile finite volume tool ‘MIKE’ was used. Using the experimental study and numerical simulation and implementation of results, the dissolution coefficient of salt karst formation was calculated about 0.2 cm/h. Numerical model results showed that early months of operation were not critical to the project and salt concentration in reservoir was in the range of 0.8 to 0.9 of allowable limit. But considering the changes occuring in reservoir’s conditions, the process of salinity distribution increases and salt concentration increases with time. By comparing the salt concentration in reservoir and in numerical model, it was found that the average error percentage of concentration values was  about 13.65 percent and the numerical model showed the values lower than the reservoir in most times.The sensitivity analysis of parameters affecting the salinity distribution, showed that these parameters have a significant impact on salinity distribution and salt concentration in reservoir. It was found that with 10 percent changes in studied parameters, dissolution rate with 21%, air temperature with18%, discharge with 21.1% and relative humidity with 6.1% caused changes in salt concentration of reservoir. According to the results it is evident that dissolution rate and discharge were the most important factors that influence the behavior of salinity distribution in dam reservoir.

Based on the water surface elevation, there is three types of flow control: flow control at the spillway crest, flow control at the shaft and flow control at the top of the shaft tunnel. In the following research, Flow3D software used for numerical modeling and the results were compared with experimental work, and good agreement was observed. Also, discharge - head graph is plotted for morning glory spillway, which shows by increasing the head, control point moves from the crest to the vertical shaft and then to downstream tunnel. In the case of complete submergence, significant changes in the head are observed with a low increase in flow rate. A parametric study has been done on the length of the vertical shaft and elbow radius. the results show the direct effect of these changes on head of the crest morning glory spillway, so that by increasing the length of the shaft, at a specified discharge increase head on crest, also by increasing the radius of the elbow, the head height on the crest reduced after the submergence elbow of morning glory spillway.

Incarcerated youths have a higher prevalence of behaviors that might put them at more risk for hepatitis C than the general public. This study was performed to determine prevalence of hepatitis C in inmates of a correctional center in Isfahan, Iran.

In a cross-sectional study, during one year, 160 under 18-year old incarecerated individuals using nonprobable sampling method were enrolled in the study. Risky behaviours were obtained by a validated questionaire and blood sample for hepatitis C detection. The experiences of administration were gathered and analysed by content analysis.

All of the elligible participants were voluntarily enrolled in the study. This population consisted of the 147 boys and 13 girls. Seven cases of hepatitis C were diagnosed that makes HCV prevalence 4.4%.

This was a successful experience due to the excellent caoperation between suffs of correctionl centers and the investigators. However, the high HCV prevalence obserrved in this study leads us to prepare and education programmes to decrease HCV spread and risky behavours in this population.