Showing 5 results for M. Kashefipour
A. Moradi Sabz Koohi, S. S.m. Kashefipour, M. Bina,
Volume 15, Issue 56 (sumer 2011)
Abstract
Drops are the most important and common hydraulic structures used as energy dissipators in irrigation networks and erodible waterways. Dissipation of energy occurs in two different ways. One portion belongs to the geometric form of the structure (briefly called loss due to structure), whereas the other occurs due to happening of hydraulic jump downstream of the structure. The dimensions of drop structure and downstream stilling basin can be optimized if geometric and hydraulic characteristics are recognized properly. In this research, the effects of drop geometry and hydraulic characteristics on the loss due to structure were investigated. At first, the effective dimensionless parameters were specified. 14 physical models of more common drops including straight, inclined and stepped drops were then built in 2 heights of 51.5 & 25.5 centimeters and 2 bed slopes of 26.6 & 33.7 degrees. The number of steps in stepped models was chosen equal to 3 and 7. With establishment of 90 flow rate, the energy losses were compared. The results showed that in the range of variable parameters, the straight drop has the maximum amount of energy dissipation.
F. Kooti, S. M. Kashefipour, M. Ghomeshi,
Volume 16, Issue 59 (spring 2012)
Abstract
In this paper, velocity profiles were analyzed under different conditions such as bed slope, discharge and concentration of density current, and water entrainment. Experiments were carried out in a tilting flume with the density currents being provided using salt and water solution. Results showed that the above mentioned factors have significant effects on the velocity profile characteristics. Dimensionless velocity profiles were also provided and compared for sub-critical, critical and supercritical flow conditions and the results showed that for supper critical conditions the velocity profiles are generally thicker due to the more ambient water entrainment. The coefficients of velocity profile equations were also derived for the jet and wall zones, which showed good agreements with the experimental measurements. Relative values of the velocity profile characteristics were also calculated in order to have a better understanding about the velocity profile structure.
R. Ghobadian, M. Zare, S. M. Kashefipour,
Volume 16, Issue 60 (Summer 2012)
Abstract
Development of precise and simple methods in flood simulation has greatly reduced financial damage and life loss. Various methods and procedures have been implemented based on Saint-Venant's one-dimensional equation governing unsteady flows. To simplify the solution for these flows, analytical and numerical methods have been used. In the present study, a new method that provides the optimal outcome is introduced using non-linear programming. Penalty function has also been used to convert nonlinear programming (NLP) constrained problems into unconstrained optimal issues. To verify the accuracy of decision variables, the study covered 60 cross-sections of Gharasu River and 25-year flood hydrographs. After determining the model correctness, the 50 and 100-year flood hydrograph were routed in 18 Kilometers. The results were statistically compared with hydraulic and Muskingum hydrological methods. To sum up the routed hydrographs introduced by NLP method were very close to the hydrographs produced by dynamic wave method. The R2 of calculated discharge of routed hydrograph by NLP and dynamic wave method were 0.948, 0.990, and 0.989, respectively, with the return period of 25, 50 and 100-year flood being 0.989. It can be concluded that NLP method is more accurate than Muskingum method, especially when predicting the peak discharge of flood hydrograph.
S. Baghbanpour* and S. M. Kashefipour, ,
Volume 16, Issue 61 (fall 2012)
Abstract
Rivers as a main sources of supplying water for urban areas, agriculture and industry, are very important. This point reveals the necessity of the control, improvement and solving the problems of rivers, especially all problems relating to water quality. In this study, transport of the suspended sediment is numerically modeled. The Saint-Venant hydrodynamic equations and also advection-dispersion equation (ADE) are applied for modelling flow and suspended sediment transport. It is necessary to choose appropriate empirical and/or semi-empirical equation to accurately estimate the equilibrium suspended sediment discharge, as well as the appropriate equation describing longitudinal dispersion coefficient. In this research, 5 and 6 equations were applied in the ADE for estimating equilibrium suspended sediment discharge and longitudinal dispersion coefficient, respectively. 30 combinations of these equations were made and the final model was run for each of them separately. Comparison of the predicted suspended sediment concentrations and the corresponding measured values at the survey site, Abdelkhan Station, for the calibration and verification periods showed that the combination of the Van Rijn's equilibrium suspended sediment equation and the Fischer's longitudinal dispersion equation performed very well. The maximum percentages of errors in estimation of suspended sediment concentrations were 19.56% and 26.3% for the calibration and verification periods, respectively.
M. Toozandehjani, M. Kashefipour,
Volume 16, Issue 62 (Winte - 2013 2013)
Abstract
One of the usual ways to dissipate excess energy in the dam's downstream is hydraulic jump. Hydraulic jump is a rapidly varied flow, in which the flow conditions change from supercritical to sub-critical with a large amount of energy loss. In this research, a combination of two water jets in the form of overflow dam and underflow through a slot on the body of an ogee dam with the USBR standard was established in order to decrease the length and sequent depth in a hydraulic jump. In these experiments, the underflow from the slot was designed with three out passages of 0, 45, and 90 degrees in respect horizontal line. Six different discharge ratios were used for each slot and the effect of each experiment conditions on decreasing of the length and sequent depth of hydraulic jump was investigated. The results showed that the confluence of two jets with 45 degrees from the slot had the maximum effect on the reducing of the length of hydraulic jump and sequent depth, and when 26 percent of the total discharge passed through the slot as underflow, it caused the length of hydraulic jump to be reduced by 50 percent in comparison with the classic jump. This slot not only decreases the length and sequent depth of hydraulic jump but also the sediment behind the dam can be evacuated through it. Moreover, it increases the discharge coefficient.
