Abstract: Bridge piers which are constructed in the track of high water rivers cause some variations in the flow patterns. This variation mostly is a result of the changes in river sections. Decreasing the river section, bridge piers significantly impress the flow patterns. Once the flow approaches the piers, the stream lines change their order, causing the appearance of different flow patterns around the bridge piers. New flow patterns are created following the geometry and the other technical characteristics of the piers. One of the most significant consequences of this event is the scour generated around the bridge piers which threatens the safety of the structure. In order to determine the properties of scour holes, to find maximum depth of the scour is an important factor. In this manuscript a numerical simulation of the scour around Marand-Soofian route bridge piers has been carried out via SSIIM 2.0 Software and the amount of maximum scour has been achieved subsequently. Eventually the methods for retrofitting of bridge piers against scours and also the methods for decreasing the amount of scour have been offered.
Abstract: Due to the three- dimensional flow pattern interacting with bed material, the process of local scour around bridge piers is complex. Modeling 3D flow field and scour hole evolution around a bridge pier is more feasible nowadays because the computational cost and computational time have significantly decreased. In order to evaluate local flow and scouring around a bridge pier, a completely three-dimensional numerical model, SSIIM program, was used. The model solves 3-D Navier-Stokes equations and a bed load conservation equation. The model was applied to simulate local flow and scouring around a bridge pier in a large natural river with four piers. Computation for 1 day of flood condition was carried out to predict the maximum local scour depth. The results show that the SSIIM program can be used efficiently for simulating the scouring in natural rivers. The results also showed that among the various turbulence models, the k-Ļ model gives more reasonable results.
Abstract: Sedimentation formation is a complex hydraulic phenomenon that has emerged as a major operational and maintenance consideration in modern hydraulic engineering in general and river engineering in particular. Sediments accumulation along the river course and their eventual storage in a form of islands affect water intake in the canal systems that are fed by the storage reservoirs. Without proper management, sediment transport can lead to major operational challenges in water distribution system of arid regions like the Dez and Hamidieh command areas. The paper aims to investigate sedimentation in the Western Canal of Dez Diversion Weir using the SHARC model and compare the results with the two intake structures of the Hamidieh dam in Iran using SSIIM model. The objective was to identify the factors which influence the process, check reliability of outcome and provide ways in which to mitigate the implications on operation and maintenance of the structures. Results estimated sand and silt bed loads concentrations to be 193 ppm and 827ppm respectively. This followed ,ore or less similar pattern in Hamidieh where the sediment formation impeded water intake in the canal system. Given the available data on average annual bed loads and average suspended sediment loads of 165ppm and 837ppm in the Dez, there was a significant statistical difference (16%) between the sand grains, whereas no significant difference (1.2%) was find in the silt grain sizes. One explanation for such finding being that along the 6 Km river course there was considerable meandering effects which explains recent shift in the hydraulic behavior along the stream course under investigation. The sand concentration in downstream relative to present state of the canal showed a steep descending curve. Sediment trapping on the other hand indicated a steep ascending curve. These occurred because the diversion weir was not considered in the simulation model. The comparative study showed very close similarities in the results which explains the fact that both software can be used as accurate and reliable analytical tools for simulation of the sedimentation in hydraulic engineering.
Abstract: Permanent rivers are the main sources of renewable
water supply for the croplands under the irrigation and drainage
schemes. They are also the major source of sediment loads transport
into the storage reservoirs of the hydro-electrical dams, diversion
weirs and regulating dams. Sedimentation process results from soil
erosion which is related to poor watershed management and human
intervention ion in the hydraulic regime of the rivers. These could
change the hydraulic behavior and as such, leads to riverbed and river
bank scouring, the consequences of which would be sediment load
transport into the dams and therefore reducing the flow discharge in
water intakes. The present paper investigate sedimentation process
by varying the Manning coefficient "n" by using the SHARC
software along the watercourse in the Dez River. Results indicated
that the optimum "n" within that river range is 0.0315 at which
quantity minimum sediment loads are transported into the Eastern
intake. Comparison of the model results with those obtained by those
from the SSIIM software within the same river reach showed a very
close proximity between them. This suggests a relative accuracy with
which the model can simulate the hydraulic flow characteristics and
therefore its suitability as a powerful analytical tool for project
feasibility studies and project implementation.
Abstract: Analytical investigation of the sedimentation
processes in the river engineering and hydraulic structures is of vital
importance as this can affect water supply for the cultivating lands in
the command area. The reason being that gradual sediment formation
behind the reservoir can reduce the nominal capacity of these dams.
The aim of the present paper is to analytically investigate
sedimentation process along the river course and behind the storage
reservoirs in general and the Eastern Intake of the Dez Diversion weir
in particular using the SHARC software. Results of the model
indicated the water level at 115.97m whereas the real time
measurement from the river cross section was 115.98 m which
suggests a significantly close relation between them. The average
transported sediment load in the river was measured at 0.25mm ,
from which it can be concluded that nearly 100% of the suspended
loads in river are moving which suggests no sediment settling but
indicates that almost all sediment loads enters into the intake. It was
further showed the average sediment diameter entering the intake to
be 0.293 mm which in turn suggests that about 85% of suspended
sediments in the river entre the intake. Comparison of the results
from the SHARC model with those obtained form the SSIIM
software suggests quite similar outputs but distinguishing the
SHARC model as more appropriate for the analysis of simpler
problems than other model.