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Showing 6 results for Ghomeshi
Evaluation of Sediment Transport Equations in the Khuzestan Rivers
M. Ghomeshi, H. Torabi-Poodeh,
Volume 6, Issue 1 (spring 2002)
Abstract

Many sediment transport equations have been developed for estimation of the river sediment materials during the past four decades. There are significant differences in the results from these equations when applied to compute sediment transport for a specific river. Therefore, application of an equation for estimation of a river sediment load is not an easy task. In this study, 12 important sediment transport equations including Meyer-Peter and Muller, Einstein, Bagnold, Engelund and Hansen. Toffaleti, Ackers and White, Yang, Van Rijn, Wiuff, Samaga et al, Beg and Fazel were tested against the measured field data of four major Khuzestan rivers, namely, the Karoon, the Dez, the Karkheh, and the Maroon. For accurate results and rapid computation, a computer program was developed for this purpose. Over 490 measured data from the gauging stations of these rivers are selected. Using these data, the hydraulic parameters and the bed material of the gauging stations are determined.

The results of the computer program are analyzed and compared with the measured data. The results from this study show that those equations which are based on the energy exchange of the flow, are generally in good agreement with the measured data for Khuzestan Rivers. From these equations, the Engelund and Hansen’s equation generally predicts satisfactory results for the all gauging stations except for the Maroon River gauging station. And finally if the sediment load computed by the Beg’s method is multiplied by a factor of 0.1, the results approximately match those obtained from the Engelund and Hansen’s method.


Analyzing Velocity Profiles in Density Current
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.
The Functional Comparison of the Turbulent Model to the RNG Model at Predicting the Plunge Point Depth
H. Goleij, J. Ahadiyan, M. Ghomeshi, H. Arjmandi,
Volume 18, Issue 69 (fall 2014)
Abstract

While the mass density current penetrates the stagnant fluid, a plunge point occurs. In this regard, the boundary of the dense fluid with ambient fluid is determined at the plunge point height. In this research, the hydraulic parameters of the dense flow and the bed slope of the stagnant fluid which have a significant effect on the plunge point have been investigated under the two turbulence models: the k- and the RNG at the Flow-3D model. To achieve the purpose of this research, a physical model was set up at the hydraulics laboratory of Shahid Chamran University (SCU), Ahwaz, Iran. Then, using the Flow-3D model with both the k- and the RNG turbulence model, the height of the plunge point was simulated according to the same experimental condition. Findings showed that the predicted depth under the RNG model is closer to the results of the physical model. For example, the k- and RNG model for the 12% slope can estimate the plunge point depth by 30% and 12.28% respectively more than the experimental data. However, for all the slopes, the k-e model can on average overestimate by 27% and RNG model 10.5% more than the results of experimental data. The statistical analysis showed that the RNG model predicts the plunge point depths with a satisfactory precision.


Experimental Analysis on the Water Entrainment of Turbidity Current over a Mobile Bed
A. Sharifnezhad, M. Kashefipour, M. Ghomeshi,
Volume 23, Issue 1 (Spring 2019)
Abstract
Study of Turbidity Current, as one of the most important phenomena affecting the sedimentation in the reservoirs of dams, is essential. Since most of the research studies have been conducted under experimental conditions on rigid beds, the effect of erodible bed and the formation of the bed form on the turbidity current specifications is not yet clear. Therefore, in this Research, the study of the turbidity current in two conditions of rigid and mobile bed was conducted in order to determine water entrainment specification and the effective hydraulic parameters. The results showed that water entrainment changes depended on the variation of bed roughness and the type of bed form. Also, water entrainment of turbidity current was initially reduced by about 25% with the change in the bed shear stress, relative to the rigid bed, due to formation of small bed forms; then, it increased by about 30%, forming the larger bed forms; finally it decreased with increasing the flow strength and removing the bed forms. In addition, comparison of the results of the present study with previous research showed that the formation of bed forms increased water entrainment in a constant Richardson number up to 50%.

Experimental Study of discharge - head Flow Rate Relation through Combined Structure Sharp Crested Rectangular Weir with Multiple Square Orifice
S. Barani, M. Zeinivand, M. Ghomeshi,
Volume 27, Issue 4 (Winter 2023)
Abstract
In this study the effect of orifice number and dimensions in combined structure sharp crested rectangular weir with multiple square orifice was investigated. For this propose, some experiments in different flow rate, different orifice number and dimensions were done. The results showed that by different orifice numbers and dimensions, flow discharge increased at the same upstream flow head. This increasing trend was observed in all numbers and dimensions of the investigated experiments. The analysis of the quantitative results showed that by increasing the number of orifices, the discharge rate through the combined structure of weir-orifice was increased on average 2.06 liters per second and by increasing each centimeter of orifice dimensions, the discharge was increased by 2.82 liters per second. Also by calculating the percentage of flow rate increase, it was observed that by adding the orifice number, it increases by 18.7% and by increasing the size of the orifice by one centimeter, the flow rate increases by 28.1%.

Experimental Investigation of the Effect of the Pier Group Skew Angle on Local Scour Around the Piers under Steady Flow
L. Hashemi, S. M. Kashefipour, M. Ghomeshi, M. Bahrami Yarahmadi,
Volume 28, Issue 2 (Summer 2024)
Abstract
Local scour around bridge piers is one of the most significant factors for the bridges’ destruction. Therefore, it is necessary to investigate the scour depth around the bridge piers. The effect of the skew angle of the single-column pier group related to the flow direction in two different arrangements including 1×2 and 1×3 piers on the maximum scour depth around the pile group was investigated in this study. The experiments were carried out under steady flow conditions. The pier group was placed in the 1×2 arrangement at the skew angles of 0 to 90 degrees and in the 1×3 arrangement at the skew angles of 0 to 45 degrees. The results showed that increasing the skew angle of the pier group is almost ineffective on the maximum scour depth around the first pier. However, it has a great effect on the maximum scour depth, its temporal development, and the expansion of the scour hole around the second and third piers in different arrangements of the pier groups. The maximum scour depth of the pier group in both different arrangements occurred at a skew angle of 30 degrees, in the arrangement of 1×2 around the second pier and by 13.33% more than the first pier and in the arrangement of 1×3 around the third pier and by 21.57% more than the first pier.

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