فهرست مطالب

Hydraulic Structures - Volume:3 Issue: 2, Autumn 2017

Journal of Hydraulic Structures
Volume:3 Issue: 2, Autumn 2017

  • تاریخ انتشار: 1396/10/30
  • تعداد عناوین: 6
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  • Hamid Goharnejad *, Mahyar Azizkhani, Mahmoud Zakeri Niri, Saber Moazami Pages 1-9
    Due to the immense damage caused by dam failure, especially dams constructed near large cities, it is necessary to consider the breaking phenomena as well as studying and designing different parts of the dam. For this purpose, the hydrograph of the outflow due to dam failure must be identified according to size of the fracture and then flood routing, and flood zone must be determined based on the downstream topography and morphology. The integration of hydraulic models and geographic information system is used to achieve this objective. In this research the effect of breaking Taleghan storage dam due to the slip of a pile of reservoir abutment and the creation of current wave toward the dam body as well as the vulnerability analysis due to the breaking of the dam on downstream lands was studied. At first, Taleghan dam failure for five different scenarios was modeled using the FLOW-3D numerical software and then the geometric data of the river was extracted using the ArcGIS software and modeling the flood due to dam failure was conducted in Hec-GeoRas model. Then, the risk analysis was performed for each break scenario of Taleghan dam. The results indicated that the maximum amount of inundation would occur in Razmian city at an approximate distance of 45 kilometers from Taleghan dam site.
    Keywords: Dam breaking, Inundation, Vulnerability, Risk analysis, Taleghan dam
  • Ali Rajabi *, Elham Hatamkhani, Jalal Sadeghian Pages 10-21
    The equations of fluids in porous media are very useful in designing the rockfill and diversion dams, gabions, breakwaters and ground water reserves. Researches have been showed that the Forchheimer equation is not sufficient for the analysis of hydraulic behavior of free-surface radial flows; because, in these flows, in addition to the hydraulic gradient and velocity, the variable of radius is also an independent parameter due to variations in cross section. In this paper, we have used an experimental model to analyze the nonlinear free surface radial flows and to introduce an equation compliant with these flows. This is a semi cylindrical model including a type of coarse grained aggregate which leads the radial flow into the center of a well. Thereafter, the hydraulic gradient was measured on different points of the experimental model by three distinguished methods of difference of successive radii, keeping constant the minimum and maximum radii. An equation, describing the behavior of free surface radial flow, was then proposed by measured data (as regression data) from the laboratory and analysis of the results. Verification of the proposed equation by test data shows that the equation is valid on the established limits of the data.
    Keywords: Hydraulic gradient, Hydraulic behavior, Forchheimer, Porous media, Radial flow
  • Samira Ghotbi *, Azam Abdollahi, Mehdi Azhdari Moghadam Pages 22-31
    Local scouring in the downstream of hydraulic structures is one of the important issues in river and hydraulic engineering, which involves a lot of costs every year, so the prediction of the rate of scour is important in hydraulic design. Side weirs are the most important of hydraulic structures that are used in passing flow. This study investigate the scouring due to falling jet from side weir in downstream in side channel numerically. The simulation was done with finite volume method. The comparison of numerical and experimental results of flow fields shows agreement. Results show that from upstream to downstream of side weir located in side channel, scoring is increased and the dimensions of the scour hole in the downstream of the rectangular side weirs increase along it. In fact, at the downstream of the lower edge of side weirs in side channel, scouring has the greatest dimensions; in particular the depth.
    Keywords: Scour, Side weir, Three dimensional, Modeling, Finite volume method
  • Mohammad Vaghefi *, Mohammad Moghanloo, Danesh Dehghan, Arsalan Keshavarz Pages 32-46
    Base-level fall in river beds occurs due to varying natural or unnatural causes. Base-level fall causes the change in the behavior of flow at the location of drop in base-level. In such situations, most of scour occur at the foot of the slope, and slope wall retreats in the upstream direction. This phenomenon widens the wall of the river bank, thus leading to its destruction. The amount of bed topography variations and scour around a rectangular bridge pier with an oblong nose located in the 90 degree angle of a 180 degree sharp bend was studied in this work by generating base-level fall at the beginning of the 180 degree sharp bend, and it was compared with a case without a base-level fall. The results indicated that in the case of base-level fall at the upstream side of the bridge pier, increase in flow depth, as well as reduction in velocity at the area around the pier, is observed, and the maximum depth of scour hole and the volume of scour hole around the pier respectively reduce by 73 and 97% in comparison with those in the case where no base-level fall occurs.
    Keywords: 180 degree sharp bend, base, level fall, Scour, Bridge pier, topography
  • Soroosh Alahdin *, Hamid Ghafouri Pages 47-61
    In this study a simulation-optimization model is developed for deriving operation rule-curves in drought ýperiods. To each reservoir, two rule-curves with adjustable monthly levels are introduced dividing the ýreservoir capacity into three zones between the normal water level and minimum operation level. To each ýzone of a reservoir and for each month of the year a hedging coefficient is introduced that determines the ýrelease from the reservoir. Accordingly, an optimization problem is developed in which the objective is ýthe minimization of water demands deficits in drought and the decision variables are the rule-curves ýlevels and hedging coefficients. For optimization of the problem, a genetic algorithm equipped with a ýself-adaptive constraint handling strategy is used. To evaluate the objective function and constraints ýviolations, the flexible and widely-used WEAP simulation model is exploited and coupled to the ýoptimization solver. The model is then applied to the Zohreh three-reservoir system in the southwest of ýIran and compared to the Standard Operation Policy (SOP). According to the sustainability indices for ýthe system operated in drought, the obtained operating rule-curves are found significantly superior to the ýSOP. As a result of applying the rule-curves, the modified shortage index (MSI) and vulnerability ýý(extent) of the system are respectively improved by 22% and 28% compared to the SOP. Consequently, ýthe developed policy application resulted in longer periods of deficit (but less severe) as shown by ýdecrease in reliability (5%) and resilience (40%) indices. ý
    Keywords: Operating policy, Rule, Curve, Sustainability Indices, Optimization Model, Hedging
  • Alireza B. Dariane *, Leila Eamen Pages 62-77
    Urmia Lake in northwestern Iran has been facing critical water level shrinkage in recent years with ýserious environmental consequences. It is expected that with the current trend, the lake will be ýcompletely dried out in a few years from now. This study attempts to assess the impacts of human ýactivities on water level fluctuations of Urmia Lake by developing a comprehensive hydrologic ýsimulation model. Model development and calibration was carefully accomplished by utilizing effective ýwater resources management components in the basin. An important contribution was accomplished by ýproperly estimating the agricultural water demand and consumption in the absence of measured data. ýResult of long-term simulation reveals that excessive water consumption by inefficient and expanding ýirrigated agriculture is the main reason for Urmia Lake shrinkage. It was found that main reservoirs are ýonly responsible for 23% of current situation. Whereas, 77% of the current crisis has been caused by ýmiscellaneous agricultural water withdrawals in the basin.ý
    Keywords: Agricultural Development Projects, Comprehensive Water Resources Simulation, Lake Level ?Fluctuations, Urmia Lake Basin