In this study, different components that affect energy dissipation on flow over gabion-stepped spillways were investigated using physical models, and comparisons were made with the other studies. Flow over gabion spillway was conducted in both through flow and overflow simultaneously. The discharge is in the range of 5 to 65 liters per second. Uniform particles with three medium diameters of 10, 25, and 40 mm were used. The height and width of the physical models were 60 and 40 cm, respectively, with 3 steps and the downstream slope of weirs was 1: 1, 1: 2, and 1: 3 (V: H). Tow end sills including rectangular and inclined shapes were used. The results showed that the effect of end sills in gabion-stepped weirs with lower slope is more than that of weirs comprising higher slope. The effect of the end sills on the energy dissipation in the weir for d50=40 mm and S=1: 2 is about 10% more than the weir with d50=10 mm and S=1: 1. In weir including d50=10 mm and S=1: 2 is about 30 to 35 percent more than the weir with d50=10 mm and S=1: 1. Therefore, the existence of end sills in the weirs with the body of materials of d50=10 and 40 mm have the highest and the least effects on the energy dissipation. On the other hand, the effect of the rectangular end sill on the energy loss is about 3-4% more than that the effect of the triangular end sill.

In this study, the effect of different hydraulic parameters on the energy loss of flow over gabion stepped spillways are examined using physical models and comparisons are made with the other studies. Two end sills including rectangular and inclined shapes are used on each spillway step. The results showed that the influence of end sills in gabion stepped spillways with lower slopes is greater than that of spillways with higher slopes. The influence of end sills on energy loss in spillways with d50=40 mm and S = 1:2 is about 10% more than the spillways with d50=10 mm and S = 1:1 (d50 is the mean diameter of gravel in the gabion and S is the downstream slope of the gabion stepped spillways, vertical: horizontal). Energy dissipation in spillways with d50=10 mm and S = 1:2 is about 30 to 35 percent more than spillways with d50=10 mm and S = 1:1. Hence, end sills in spillways with gravel size of d50 = 10 mm have the most significant impact on the energy loss. Instead, the influence of the rectangular end sill on the energy loss is about 3-4% more than the effect of a triangular (inclined) end sill.

In this study, experimental procedure and laboratory works have been conducted to investigate the energy loss rate on stepped spillway, using inclined steps together with end sill. To have a more elucidated investigation inclined steps with different slopes (Horizontal, 7, 10, and 12 degrees with respect to the horizon) and end sill with different thicknesses (5 and 10 mm) and heights (6, 8, 10, and 15 mm) were used to determine the impact of these parameters on the relative energy loss. Results show that using inclined steps together with end sill has a considerable effect on the energy loss of both nappe (30 liter/sec) and skimming (90 liter/sec) flows; however, energy dissipation in nappe flows is greater than that in skimming flows. Energy loss resulted from end sills with smaller thicknesses is higher than that of end sills with greater thicknesses. Comparison of the results of the current survey with similar studies reveals that the approach used in the current investigation is more efficient than previous ones.

Hydraulic jump has been used widely for dissipating excess energy downstream of hydraulic structures in irrigation and drainage networks. The characteristics of hydraulic jump in triangular sections have not been studied as much as those in rectangular, trapezoidal and circular sections.In this paper, the characteristics of hydraulic jump in a triangular channel with broad crested endsill is studied. The experiments are carried out in a laboratory flume of 9 m length, 0.5 m width and o.6 m height with glass side walls. Different flow discharges and sluice gate openings with issuing jet Froude number in the range of 2.5-12.5 was studied. The results showed that for a given Froude number, the required tail water depth for the triangular section is up to 70% lower than that in a rectangular section. Based on the regression analysis, several empirical equation sare proposed for determining sequent depth ratio and dimensionless sill height as a function of inflow Froude number. The proposed equations can be used in designing controlled hydraulic jump in triangular sections were tail water is not adequate for a classic hydraulic jump.

Side channel spillways have a common usage in conveyance and distribution networks, high dams, water and wastewater treatment plants, and surface drainage networks. A side channel carries spatially varied flow with increasing discharge and their water surface profiles is a main feature in the design process. Usually, the bottom width of the channel is flared in the flow direction and an end sill is also installed at the downstream end to provide a control section and to generate an even water surface profile. In this study, the impact of installing an end sill on the flow characteristics in a non-prismatic side channel is presented. Six distinct longitudinal profiles were clearly observed in each run and the difference between the mid points of the maximum and the minimum profiles of each run was used to evaluate the sill effects on the water surface profile and the energy dissipation. The results indicated that the maximum and the minimum differences are, respectively, equal to critical depth and half of it generated at the channel downstream end. Also, based on an envelope of the data, a method was proposed to determine the maximum potential impact of an end sill that might have on the flow depth, which could also be considered as a guideline in the design process.

Estimation of scour at bridge piers has always been a challenging problem to the hydraulic engineers and has attracted the interest of many researchers. Bridges are always degradation due to various factors, but many researchers have identified the main cause of bridge failure as local scour around bridge piers (Lagasse and Richardson, 2001; Dey and Barbhuiya, 2004; Khaple et al., 2017b). Although there are numerous studies of local scour, however, the coherent structures in turbulent flow around the bridge pier still remain unknown. Most studies on scour have focused on techniques to control and reduce the local scouring (e.g. Izadinia and Heidarpour, 2012). Since the sediment transport process is very complicated due to the interaction of many parameters, therefore, studies have been carried out to determine the turbulent flow structure, but not enough. Lu and Willmarth (1973) introduced the quadrant analysis for studying the structure of the bursting phenomenon. In fact, the bursting phenomenon consists of four different events outward interaction, ejection, inward interaction, and sweep. Izadinia et al. (2013) and Izadinia and Heidarpour (2019) by measured velocity profiles around the circular pier and using quadrant analysis, they investigated the flow structure around the pier. Given the importance of the flow structure and in particular the bursting events around the bridge piers, it can be stated that still their characteristics have not been investigated in detail. Therefore, since the quadrant analysis is a powerful tool to recognize the structure of the bursting phenomenon and consequently to find the susceptible regions for sediment entrainment and deposition, this technique is considered in present study to investigate the coherent structure of turbulent flow in scouring process around the bridge pier. In addition, since previous studies have focused more on investigating the flow structure at the circular bridge pier, therefore, the main objective of this study is to investigate the flow structure around round-nosed rectangular with bed sill.

In this study, an explicit equation is presented for estimating the height of the end sill in the trapezoidal stilling basin based on the energy equation. In addition to the experimental results were compared with energy and momentum methods which have been solved by numerical methods. Evaluation results indicate proper coordination between experimental and computational data and confirmed that the presented explicit equation can compute end sill height with suitable accuracy. In recent decades, several studies aimed at understanding the function of hydraulic jumps in trapezoidal sections have been made Forrester and Skrinde (1950) to find an analytical equation based on the Froude number, initial depth, sequent depth and sill height for controlling jump in rectangular sections which used rectangular broad-crested weir equation for determining discharge which was created by Barker and Doeringsfeld (1941). Achour and Debabeche (2003) investigated the effects of broad-crested end sill on the U-shaped sections as well as the effect of the sharp-crested end sill on the triangular sections with the apex angle of 90o, by comparing the theoretical and experimental equations in U-shaped sections. They also found that the required sharp-crested end sill for controlling the hydraulic jump with the same conditions should be slightly taller than broad-crested end sill in U-shaped cross sections. Achour and Debabeche (2003) presented an explicit relationship in rectangular sections to find the minimum broad-crested end sill height necessary to control the hydraulic jump which indicated good agreement with the results of Forrester and Skrinde (1950). If a broad-crested end sill placed on the supercritical flow path in the stilling basin, hydraulic jump is formed. The minimum height necessary for the sill according to the specific energy concept can be calculated. In this case, due to the existence of critical depth on the sill, this section will act as a control section. To evaluate the results of the proposed explicit equation to determine the end sill height, a number of tests were carried out. Experiments were done in a horizontal channel with symmetrical trapezoidal cross-section, and with side slopes z=0.5, 1, 1.5, Length of 3 m and a width of 5.0 meters to measure the characteristics of flow jumps in the discharges range of 19.3 To slow down and measure the input flow in laboratory model, upstream primary reservoir, with dimensions of 1.25 m wide, 1 m long and 1 m high were designed and built. Inlet water flow to model supply through the circulated flow system with the closed circuit pipes in the laboratory, and through the branch of pipe near the model was connected to the first tank. To calm the approaching flow to the weir, a mesh with 1.25 m width and 1 meter height was used. Discharges measured with a calibrated weir in upstream tank. With the crossing of water over the weir, the flow was entered to supply-height reservoir. The purpose of constructing this reservoir was providing the required energy for the formation of the hydraulic jump with desired Froude number.Initial and sequent depth was measured with an accuracy of 1.0 mm by a point gage. In order to create jump without the end sills, flow was controlled by a terminal movable valve as a tailgate. For each of the experimental data obtained from the Fr1, in the range of 3 given that the critical depth was created on the broad-creased sill, by writing momentum equation at the section of the sequent depth and sections with critical depth on the sill, the sill height can be calculated. As well as the sill height can be calculated by Bernoulli equation without taking into account the energy loss. Using any of these two methods is needed to solve nonlinear equations implicitly. With the proposed explicit equation, estimation of height end sills is provided easily in terms of the flow characteristics and canal cross sections with high accuracy. The values obtained from the proposed explicit equation for the height of broad-creased end sills with predicted values of energy and momentum equations are approximately the same, and all three methods have little difference with the experimental results. Also, it can be said that this equation can be predicted experimental data with high accuracy and indicates good performance as terms of practicality.In this study, the control of hydraulic jump with broad-creased end sills in trapezoidal sections with three side slope of 1: 0.5, 1: 1 and 1: 1.5 was investigated. Flow analysis over the broad-creased sill allowed that the minimum sill height necessary for controlling the hydraulic jumps to be estimated.The results of the comparison of the proposed equation with momentum and energy equations and experimental results showed good accuracy in estimating the required broad-creased sill height to control the jumps in trapezoidal sections. Because there are no more experimental results, presented equation can be used as a guide in designing of energy dissipators to determine the broad-creased sill in trapezoidal sections with the explicit equation. It is noteworthy that the broad-crested sill is superior in comparison with other dissipators hydraulic jump structures, due to its structural stability and lower costs.

Stilling basins are used in the outlet of channels, chutes and culverts to dissipate the excess kinetic energy of incoming flow. One of the basins in which the energy of incoming flow is dissipated by impact, is USBR VI stilling basin. The USBR VI stilling basin was first introduced by Bradely and Peterka in 1995 and then was modified by Biechley in 1978. This structure consists of a middle wall and an endsill. Scouring around the structures that are located in the vicinity of erodible beds, such as stilling basins, has always been one of the most important problems related to these structures. Unlike other types of stilling basins, the studies carried out around this type of basin are limited, and there are still many hydraulics features of this type that have not been considered in previous researches. In this article, the effect of the shape of endsill on scour depth downstream of stilling basin is evaluated. Based on Beichley graph (Standard Design), the physical model of stilling basin was designed, constructed and installed in the hydraulic laboratory of Tarbiat Modares. Experiments were conducted in a 0.8 m wide, 0.9 m height, and 0.8 m length rectangular channel. The pump used in the experiments had a nominal flow rate of 400 cubic meters per hour (about 120 liters per hour), a head of 11.7 meters, a power of 22 horsepower, and an engine speed of 1450 rpm. In the design of experiments, the parameters including approach Froude number (i.e. 1, 1.5 and 2 times of standard Froude number on Beichley graph), the diameter of inlet pipe (i.e. De = 5, 8, and 12 centimeters), and endsill shapes (triangular, stepped and circular quadrant), in the form of 27 tests were assessed to study the dimensions of the scour depth. The observations revealed that in all three endsill shapes, the increase in Froud number has led to the decrease in scour index. the circular quadrant endsill had the lowest scour depth in the front of endsill and the least scour index, in the range of the Froude number of 2 to 6. In the range of the Froude numbers of 9 to 14, the triangular endsill causes the lowest scour index. In the relative diameter of inlet pipe equals to 10.16, for Froud numbers equal to 9.27 and 13.91, the triangular shaped endsill has the least scour index. in every endsills, decreasing the pipe’s diameter results in the maximum depth of the scour. Another important finding is that sediment bar is only formed in experiments conducted with inlet pipe’s diameter equal to 5cm for Froude number equal to Froude number on Beichley graph. The biggest amounts of the height of sediment bar and maximum scour depth are found for the stepped endsill and the smallest amounts of the height of sediment bar and maximum scour depth are found for the circular quadrant endsill. Subsequently, the non-dimensional equations according to the Froud number of incoming flow and the relative diameter of inlet pipe, were presented to estimate the maximum depth of the scour hole.

For the past three decades or so, language teachers, researchers and educators have been working on language learning strategies. From early examples of research such as the studies carried out by Rubin (I 975) and Stern (1975), to taxonomies of strategies like that drawn up by Oxford (1990), to theories of language acquisition which incorporate strategies (O'Malley & Chamot, 1990), much work has been done to identify what might be good language learning strategies. A major problem in measuring the learning strategies of learners of English as a foreign language (EFL) is the development of a valid and reliable instrument. This article deals with Oxford's Strategy Inventory for Language Learning (SILL). In fact, the present study investigate the reliability and construct validity Oxford's 50-item questionnaire designed to be used in foreign language settings. Five hundred and sixty eight Iranian BS and BA students took the questionnaire. The results revealed that the SILL has acceptable reliability, but does not enjoy satisfactory construct validity.

Expanding stilling basins not only are effective energy dissipators, but also appropriate translations between hydraulic structures. Hence, the present study aims at numerical simulation of the effect of end-sill location on the energy dissipation. Doing so, Fluent software was employed and hydraulic jump under two divergence angels and four end-sill locations in the range of 4 to 8 Froude number was examined. According to the results, for larger expansion angles, the sequent depth and jump length are lower and energy dissipation is much more. Moreover, as the end-sill closes to the basin’ s entrance, the lower sequent depth, shorter jump, and less energy dissipation are observed. For very close locations more instability in the flow surface are seen. Results showed that for a given expansion angel, improving the location of the end-sill can decease 20% the conjugate depth, enhance 90% the amount of energy dissipation, and reduce 26% the jump length.