Showing 8 results for Energy Dissipation
H. Hamidifar , M.h. Omid , J. Farhoudi ,
Volume 14, Issue 54 (1-2011)
Abstract
This paper presents the results of an analytical and experimental study on the characteristics of hydraulic jump in a triangular channel. The analytical consideration is based on the momentum conservation law for the upstream and downstream sections of the jump. The experiments were carried out in a triangular channel of glass side walls with the vertex angle of 94.4°. A wide range of discharge and inflow Froude number were used in the experiments for two different opening heights of the upstream sluice gate. The main characteristics of the jump such as the sequent depth ratio, relative energy dissipation and water surface profile were investigated and the results were compared with those of the rectangular sections. The results showed that the triangular section is more efficient to dissipate the inflow energy. The efficiency of jump in a triangular channel is about 12% more than a rectangular channel for the same condition. As a result, hydraulic jump in a triangular channel needs a smaller tail water depth for a given inflow jet height and Froude number. Also, empirical relations and graphs are presented to determine the characteristics of the jump in triangular sections
A. Moradi Sabz Koohi, S. S.m. Kashefipour, M. Bina,
Volume 15, Issue 56 (7-2011)
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.
K. Roshangar, R. Valizadeh,
Volume 21, Issue 2 (8-2017)
Abstract
Hydraulic jump is the most common method of dissipating water’s kinetic energy in downstream of spillways, shoots and valve. In this paper, Support Vector Machine (SVM) method, as a machine learning method, have been used to estimate hydraulic characteristics such as the sequent depth ratio, jump length and energy loss in three different sudden expansions stilling basins, and the rate of influence of input parameters in each jump has been analyzed. In order to evaluate the performance of proposed method, 936 sets of the observed data have been used for training and testing process of three kinds of expanding channel models. Furthermore, a comparison between semi-theoretical approaches and the data obtained from the best SVM models have been carried out. The results confirmed the efficiency of SVM method for estimating the hydraulic jump characteristics and proved that this method performed well in comparison to the semi-theoretical relationships. The obtained results revealed that the superior model for the sequent depth ratio and relative energy dissipation was the model with (Fr1,h1/B) parameters and the superior model for the length of hydraulic jump prediction was the model with (Fr1, h2/h1) parameters.
S. A. Banishoaib, A. Bordbar, A. A. Kamanbedast, A. Masjedi, M. Heidarnejad,
Volume 23, Issue 4 (2-2020)
Abstract
A ‘spillway’ is a structure used to provide the controlled release of flood water from upstream into downstream area of a dam. As an important component of every dam, a spillway should be constructed strongly, reliably and efficiently to be used at any moment. Labyrinth and stepped spillways are presented as appropriate modifications to those spillways hardly capable of managing the maximum potential discharge. Owing to their nonlinear crests for a given width, labyrinth and stepped spillways have a larger discharge rate than linear- crest spillways at an identical height. Compared to other energy dissipaters, the combination of stepped and labyrinth spillways is known as a very strong energy dissipater. In the following part, the combination of these two structures and their dimensional change for increasing the water- energy dissipation are addressed. To conduct this study, an experimental flume with a 90- degree bend in the Islamic Azad University of Ahwaz was used. In total, 90 experiments were conducted on three different labyrinth- shape stepped spillway models with two different lengths, three different widths, and five different discharges. Analysis of the results showed a greater energy loss reduction in triangular rather than rectangular or trapezoidal labyrinth- shape stepped spillways. In addition, energy loss was greater in labyrinth spillways with two cycles than those with one cycle. Energy loss was increased by raising the Froude number from 0.05 to 0.1; in contrast, energy loss was decreased with increasing the Froude number from 0.1 to 1.0, which was due to the submergence of steps, a decrease in the roughness of steps and an increase in the intensity of aeration.
R. Daneshfaraz, M. Majedi Asl, A. Bazyar,
Volume 24, Issue 2 (7-2020)
Abstract
Inclined drop is one of the supercritical flow producers used in open channels to reduce slope and elevation of the ground. Given that the application of horizontal and vertical screen in the downstream of this drop as an energy dissipater can be effective in the n energy dissipation of flow, in the present study, 180 different experiments were performed to investigate the energy dissipation of flow. The results showed that the angle of the drop had no marginal impact on energy dissipation and the relative depth of downstream of inclined drop equipped with a vertical screen, but increasing the porosity of screen caused enhancement in both parameters. Also, for the inclined drop equipped with a horizontal screen, by increasing angle and decreasing the porosity of screen, the energy dissipation and relative depth of downstream were raised. Also, for inclined drop equipped with a horizontal screen, by increasing the angle and decreasing the porosity of screen, the energy dissipation and relative depth of downstream were enhanced. For a constant relative critical depth, the relative depth of downstream and the energy dissipation of the inclined drop equipped with a horizontal screen considered the function of the wetted length of screen and length of the drop. For vertical screen, it is only a function of screen porosity.
H. Kheibar, S. M. Sajjadi, J. Ahadiyan,
Volume 24, Issue 3 (11-2020)
Abstract
Lopac gates, with the benefits of easy installation, automation and the ability to pass sediments and floating objects, are among the new structures considered for water level regulation and flow control in the irrigation canals. Converting the shape of the gate from a rectangular one to an elliptical one allows the flow rate to be increased by the same water level. In the present study, the effect of the sudden transition on the discharge and energy dissipation of the elliptical-lopac gate (ELG) in the submerged flow conditions was evaluated in the laboratory. The results showed that the dimensionless discharge and energy dissipation of the ELG with sudden transition to channel width conditions was decreased by 28 to 86% and increased by 11 to 35%, respectively. Finally, the statistical equations were presented to estimate the dimensionless discharge and energy dissipation of ELG by sudden transition under submerged flow conditions with a maximum error of 16%.
M. Majedi Asl, R. Daneshfaraz, J. Chabokpour, B. Ghorbani,
Volume 26, Issue 2 (9-2022)
Abstract
In the last decade, the use of gabion structures in hydraulic engineering for stabilizing the structure due to its high density and weight has become widespread. Also, the material's roughness and porosity cause it to be used in energy dissipation and drainage projects. This study evaluates the relative energy dissipation of gabion structures downstream of the ogee spillway in the conditions of a submerged hydraulic jump. The evaluated parameters in this study were Froude number, gabion height, gabion thickness, and material diameter. The experiments were performed with three average diameters of 1.5, 2.2, and 3 cm for rock material, three gabion heights of 10 and 20 cm, and Max. The end sill heights were 10, 20, and 30 cm. The operated discharges were regulated from 20 to 40 l/s. The results showed that by decreasing the average diameter of gabion aggregates, the amount of relative energy dissipation increases in all tested models, so that in gabion with a 1.5 cm average diameter of aggregates, the amount of energy dissipation increased by 3.6% in comparison with using the diameter of 3cm for the average diameter of the material. Increasing the height of the gabion to the extent that the flow is entirely inward can have up to 33% more relative energy dissipation than the gabion with a height of 10 cm. Also, by increasing the diameter of the gabion from 10 cm to 30 cm, relative energy dissipation increases up to 15%.
H. Noury Hasanabady, M.r. Kavianpour, A. Khosrojerdi, H. Babazadeh,
Volume 26, Issue 3 (12-2022)
Abstract
Using a rough bed for spillway compare to common dissipation methods such as stilling basins, stepped spillways, ski jumps, and bed elements may be more efficient to boost energy dissipation. In this research, the impact of spillway continuous bed roughness on energy dissipation was investigated. For this purpose, a non-dimensional relationship was developed, and by calibrating the numerical model based on the present experimental study, energy dissipation over the spillway for three slopes of 15, 22.5, and 30 (degree) with six roughness sizes of 0.0, 0.005, 0.0072, 0.0111, 0.016, and 0.022 (m) and three discharges of 170, 110, and 90 (lit/s) was investigated. Based on the present results, using a rough bed spillway will increase energy dissipation. Also, the ratio of energy lost per meter length of rough bed spillway to that of smooth spillway increases by chute slope. The results showed that the highest amount of relative energy consumption in the presence of roughness was related to the slope of 22.5 degrees and 22.2 mm for roughness (85%), and the lowest relative energy consumption was observed in the control state (25%). As a result of the present study, a natural rough bed without concrete coating has befitted in terms of environmental aspects, construction cost, and energy loss.
