Energy dissipation by vertically placed screens

2007 ◽  
Vol 34 (4) ◽  
pp. 557-564 ◽  
Author(s):  
Zafer Bozkus ◽  
Pinar Çakir ◽  
A Metin Ger
Keyword(s):  
Energy Dissipation ◽  
Froude Number ◽  
Hydraulic Jump ◽  
Large Range ◽  
Hydraulic Structure ◽  
Flow Depth ◽  
Supercritical Flow ◽  
Series Of Experiments ◽  
Upstream Flow

Screens can be utilized efficiently for dissipating energy of water. In this study, water flowing beneath a gate is used to simulate the flow downstream of a small hydraulic structure, and vertically placed screens are used as an alternative tool for energy dissipation. Investigations are conducted using a series of experiments. The porosity, thickness, and location of the screens are the major parameters together with the Froude number of the upstream flow. The experiments cover a range of supercritical Froude numbers between 5.0 and 18.0, porosities between 20% and 60%, and screen locations up to 100 times the undisturbed upstream flow depth. The thicknesses of the screens used are in the order of the undisturbed upstream flow depth. The results show the importance of each parameter in the energy-dissipating performance of the screens and the system. It is observed that screens dissipate significantly more energy than a conventional hydraulic jump within the large range of Froude numbers covered in the study. The results are also in agreement with the results of an earlier similar study.Key words: screen, energy dissipation, hydraulic jump, porosity, supercritical flow.

scholarly journals Experimental study of the hydraulic jump on reverse bed with porous screens

2019 ◽  
Vol 9 (7) ◽  
Author(s):  
A. Abbaspour ◽  
T. Taghavianpour ◽  
H. Arvanaghi
Keyword(s):  
Experimental Study ◽  
Energy Dissipation ◽  
Energy Loss ◽  
Froude Number ◽  
Hydraulic Jump ◽  
Open Channels ◽  
Supercritical State ◽  
Supercritical Flow ◽  
Study Results

Abstract Nowadays, the porous screens have been used extensively in open channels to prevent erosion in ditches as the water in supercritical state flows past the screen which forces the formation of a hydraulic jump upstream of the screen and produces significant energy loss. In this investigation, the operation of screens has been studied for supercritical flow and the Froude number in the range of 4.5 to 10.6 on two reverse slopes experimentally. In this study, the parameters included arrangements of screens in both the single and double types, and the angle and distance of screens from the hydraulic jump toe. The screens were studied with a porosity of about 50% with square holes. The study results showed that using of screens on the reverse slope of − 0.025 dissipates more energy compared to reverse slope of − 0.015. The screens with double arrangement have better performance and dissipate more energy than the screens with single arrangement, while the distance of screens from the toe of the hydraulic jump does not have a significant effect on the energy dissipation.

scholarly journals Uniform flow and energy dissipation of hydraulic-jump-stepped spillways

2020 ◽  
Vol 20 (4) ◽  
pp. 1546-1553
Author(s):  
Yu Zhou ◽  
Jianhua Wu ◽  
Fei Ma ◽  
Jianyong Hu
Keyword(s):  
Energy Dissipation ◽  
Water Flow ◽  
Hydraulic Jump ◽  
Flow Region ◽  
Uniform Flow ◽  
Stepped Spillway ◽  
Flow Depth ◽  
Clear Water ◽  
Air Concentration ◽  
Stepped Spillways

Abstract In skimming flow, a uniform flow can be achieved and the flow depth, velocity and air concentration remain constant if a stepped spillway is sufficiently long. In this study, physical model experiments were performed to investigate the uniform characteristics and energy dissipation of a hydraulic-jump-stepped spillway, which is a new type of stepped spillway for increasing the unit discharge capacity and energy dissipation. Based on the redefinition of uniform flow, experimental results show that at a given stepped spillway slope, a smaller height for the beginning of the uniform flow region, a greater uniform aerated flow depth and a greater uniform equivalent clear water flow depth can be obtained as compared with the traditional stepped spillway due to strong aeration in the aeration basin. Under the condition of uniform flow, the energy dissipation rate of stepped spillways can be estimated by the equivalent clear water flow depth with given inflow conditions. Compared with the traditional stepped spillway, the uniform flow over the hydraulic-jump-stepped spillway has a smaller specific energy, revealing that the hydraulic-jump-stepped spillway is more advantageous for dissipating energy, especially at large unit discharges.

scholarly journals Study on the Best Depth of Stilling Basin with Shallow-Water Cushion

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1801
Author(s):  
Qiulin Li ◽  
Lianxia Li ◽  
Huasheng Liao
Keyword(s):  
Energy Dissipation ◽  
Shallow Water ◽  
Froude Number ◽  
Flow Regime ◽  
Dissipation Rate ◽  
Hydraulic Jump ◽  
Energy Dissipation Rate ◽  
Main Stream ◽  
Stilling Basin ◽  
Key Factor

The depth of the stilling basin with shallow-water cushion (SBSWC) is a key factor that affects the flow regime of hydraulic jump in the basin. However, the specific depth at which the water cushion is considered as ‘shallow’ has not been stated clearly by far, and only conceptual description is provided. Therefore, in order to define the best depth of SBSWC and its relationship between the Froude number at the inlet of the stilling basin, a large number of experiments were carried out to investigate SBSWC. First of all, 30 cases including five different Froude numbers and six depths were selected for which large eddy simulation (LES) was firstly verified by the experiments and then adopted to calculate the hydraulic characteristics in the stilling basin. Finally, three standards, based on the flow regime of hydraulic jump, the location of the main stream and the energy dissipation rate, were proposed to define the best depth of SBSWC. The three criteria are as follows: (1) a complete hydraulic jump occurs in the basin (2) the water cushion is about 1/10–1/3 deep of the stilling basin, and (3) the energy dissipation rate is more than 70% and the unit volume energy dissipation rate is as high as possible. It showed that the best depth ratio of SBSWC (depth to length ratio) was between 0.1 and 0.3 and it also indicated the best depth increased with the increase in Froude number. The results of the work are of significance to the design and optimizing of SBSWC.

scholarly journals Hydraulic model experiment of energy dissipation on the horizontal and USBR II stilling basin

2021 ◽  
Vol 930 (1) ◽  
pp. 012029
Author(s):  
V Dermawan ◽  
Suhardjono ◽  
L Prasetyorini ◽  
S Anam
Keyword(s):  
Energy Dissipation ◽  
Hydraulic Jump ◽  
Control Point ◽  
Hydraulic Model ◽  
Flow Depth ◽  
Flow Conditions ◽  
Depth Measurement ◽  
Stilling Basin ◽  
Flow Energy ◽  
Starting Point

Abstract Flow conditions on overflow systems can result in construction failure, mainly due to the high flow energy. Stilling basin at downstream of the spillway is useful for reducing flow energy. It can reduce the destructive force of water flow. Controlling the hydraulic jump is an important part that includes the jump’s energy, length, and height. The physical hydraulic model was carried out with several series, by making a series of bottom lowering of horizontal and USBR II stilling basin. The experimental study is expected to represent flow behavior in the overflow system regarding flow conditions and energy dissipation. Based on the analytical calculation of flow velocity, the amount of flow energy that occurs at each control point is calculated. The control points are the starting point of the spillway, the chute way toe, and flow depth after the hydraulic jump. The energy loss can be calculated for each control point, while the efficiency of energy dissipation on stilling basin is calculated at the downstream flow depth after the hydraulic jump. Velocity calculated by dividing discharge per unit width by water depth which is based on the flow depth measurement data in the hydraulic model.

scholarly journals Flow regime changes at hydraulic jumps in an open Venturi channel for Newtonian fluid

2017 ◽  
Vol 9 (4) ◽  
pp. 169-179 ◽  
Author(s):  
Prasanna Welahettige ◽  
Bernt Lie ◽  
Knut Vaagsaether
Keyword(s):  
Flow Regime ◽  
Newtonian Fluid ◽  
Triple Point ◽  
Hydraulic Jump ◽  
Experimental Results ◽  
Hydraulic Jumps ◽  
Flow Depth ◽  
Supercritical Flow ◽  
Subcritical Flow ◽  
Regime Changes

The aim of this paper is to study flow regime changes of Newtonian fluid flow in an open Venturi channel. The simulations are based on the volume of fluid method with interface tracking. ANSYS Fluent 16.2 (commercial code) is used as the simulation tool. The simulation results are validated with experimental results. The experiments were conducted in an open Venturi channel with water at atmospheric condition. The inlet water flow rate was 400 kg/min. The flow depth was measured by using ultrasonic level sensors. Both experiment and simulation were done for the channel inclination angles 0°, −0.7°, and −1.5°. The agreement between computed and experimental results is satisfactory. At horizontal condition, flow in the channel is supercritical until contraction and subcritical after the contraction. There is a hydraulic jump separating the supercritical and subcritical flow. The position of the hydraulic jump oscillates within a region of about 100 mm. Hydraulic jumps coming from the contraction walls to the upstream flow are the main reasons for the conversion of supercritical flow into subcritical flow. An “oblique jump” can be seen where there is a supercritical flow in the contraction. There is a triple point in this oblique jump: the triple point consists of two hydraulic jumps coming from the contraction walls and the resultant wave. The highest flow depth and the lowest velocity in the triple point are found at the oblique jump.

Characteristics of a Hydraulic Jump Formed on Upstream Vegetation of Varying Density and Thickness

2020 ◽  
Vol 14 (03) ◽  
pp. 2050012
Author(s):  
Ghufran Ahmed Pasha ◽  
Norio Tanaka
Keyword(s):  
Energy Loss ◽  
Froude Number ◽  
Hydraulic Jump ◽  
Variable Density ◽  
Maximum Energy ◽  
Coastal Vegetation ◽  
Critical Flow ◽  
Vegetation Density ◽  
Sparse Vegetation ◽  
Upstream Flow

The effectiveness of coastal vegetation as a barrier to mitigate a tsunami greatly depends on the magnitude of tsunami and vegetation structure. This paper summarizes a series of laboratory experiments that investigated the upstream flow structure and energy loss due to a hydraulic jump in a steady super-critical flow. The characteristics of the jump were determined against vegetation of variable density ([Formula: see text], where [Formula: see text] of each cylinder in cross-stream direction, [Formula: see text] of cylinder), thickness (dn, where [Formula: see text] of cylinder, [Formula: see text] of cylinders in the stream-wise direction per unit of cross-stream width), and initial Froude number (Fro, where Froude number is obtained from a model without vegetation in the flume). In super-critical flow ([Formula: see text]–1.83), a weak hydraulic jump formed on upstream side of vegetation. The height of the jump, its location, and the resulting energy loss were increased by increasing both the vegetation density and thickness. Due to reduced reflection at vegetation front, the drag force against sparse vegetation ([Formula: see text]/[Formula: see text]) was higher compared to intermediate ([Formula: see text]/[Formula: see text]) and dense ([Formula: see text]/[Formula: see text]) vegetation. Under these conditions, the maximum energy reduction due to a weak hydraulic jump reached 9.4% for dense vegetation while it was 8.1% and 7.8% for intermediate and sparse vegetation, respectively.

Free Surface Flow Profile and Fluctuations of a Circular Hydraulic Jump Formed by an Impinging Jet

1995 ◽  
Vol 117 (4) ◽  
pp. 677-682 ◽  
Author(s):  
J. W. Stevens
Keyword(s):  
Free Surface ◽  
Hydraulic Jump ◽  
Surface Profile ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Profile ◽  
Flow Depth ◽  
Supercritical Flow ◽  
Jump Size ◽  
Free Surface Profile

A fine wire probe was used to make quantitative measurements of the free surface profile and surface fluctuations around the hydraulic jump formed by a normally impinging free liquid jet. Representative magnitudes of both radial and axial fluctuations were presented for two nozzle sizes and several jet Reynolds numbers and subcritical flow depths. The results were compared to previous measurements of the supercritical flow depth and to theoretical predictions of the circular hydraulic jump size. The agreement appeared reasonable for the supercritical flow depth while the analytical expressions predicted a shorter hydraulic jump than that found by the measurements for the same supercritical flow conditions.

scholarly journals Embedded fuzzy-based models in hydraulic jump prediction

2020 ◽  
Author(s):  
Mohammad Zounemat-Kermani ◽  
Amin Mahdavi-Meymand
Keyword(s):  
Froude Number ◽  
Optimization Algorithm ◽  
Hydraulic Jump ◽  
Learning Ability ◽  
Particle Swarm Algorithm ◽  
Hydraulic Jumps ◽  
Flow Depth ◽  
Whale Optimization ◽  
Moth Flame Optimization Algorithm ◽  
Downstream Flow

Abstract This study aims to evaluate the learning ability and performance of five meta-heuristic optimization algorithms in training forward and recurrent fuzzy-based machine learning models, such as ANFIS and RANFIS, to predict hydraulic jump characteristics, i.e., downstream flow depth (h2) and jump length (Lj). To meet this end, the firefly algorithm (FA), particle swarm algorithm (PSO), whale optimization algorithm (WOA), genetic algorithm (GA), and moth-flame optimization algorithm (MFO) are embedded with the fuzzy-based models, which represent the main contribution of this study. The analysis of the results of predicting hydraulic jump characteristics shows that the embedded ANFIS and RANFIS models are more accurate than the empirical relations proposed by the previous researchers. Comparing the performance of the embedded RANFISs and ANFISs methods in predicting Lj represents the superiority of the RANFIS models to the ANFISs. The results of the sensitivity analysis show that among the input independent parameters, flow discharge (Q) is the most important factor in predicting downstream flow depth in weak, oscillating, and steady hydraulic jumps (1.7 < Froude number < 9), while the upstream flow depth (h1) is more important than the other input parameters in strong hydraulic jumps (Froude number > 9).

Hydraulic jump in channel contraction

1995 ◽  
Vol 22 (5) ◽  
pp. 925-933 ◽  
Author(s):  
Y. Yasuda ◽  
Willi H. Hager
Keyword(s):  
Hydraulic Jump ◽  
Surface Profile ◽  
Momentum Equation ◽  
Flow Depth ◽  
Contraction Rate ◽  
Substantial Agreement ◽  
Limit Condition ◽  
Supercritical Flow ◽  
Small Contraction ◽  
Important Design

The hydraulic jump in a linearly contracting channel is studied in relation to choking flow. For a contraction intended to perform under supercritical flow, choking is an important design consideration because of the increase of flow depth and modified upstream conditions. Based on the momentum equation, a relation for the sequent depths ratio is determined and verified with extended experiments. Further, the mechanisms of both hydraulic jump and the choking flow are described. The wall surface profile is shown to be similar and equal to the profile of the classical hydraulic jump for a relatively small contraction rate. The lengths of roller and jump are determined, and substantial agreement with the classical jump is again found. The choking of a channel contraction is discussed as the limit condition of the hydraulic jump. A simplified model is shown to agree with observations. A design equation for choking is proposed. Key words: channel, choking, contraction, hydraulic jump, supercritical flow, water flow.

scholarly journals A Novel Analytical Method for Evaluating the Characteristics of Hydraulic Jump at a Positive Step

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2005
Author(s):  
Milad Mohammadi ◽  
Mohammad Nazari-Sharabian ◽  
Moses Karakouzian
Keyword(s):  
Experimental Data ◽  
Energy Dissipation ◽  
Dissipation Rate ◽  
Hydraulic Jump ◽  
Rectangular Channel ◽  
Theoretical Models ◽  
Energy Dissipation Rate ◽  
Flow Depth ◽  
Jump Length ◽  
Positive Step

We present a new method to evaluate the hydraulic jump characteristics in a horizontal rectangular channel with a positive step. We considered the flow curvature effect and the free surface’s small rise at the A-type hydraulic jump’s end. First, we present a novel method to give jump length estimation based on the similarity of the jump and the turbulent wall-jet, considering the pressure gradient. Then, considering the jump as a curvilinear flow and using a one-dimensional momentum equation, we present an accurate expression for the conjugate flow depth regarding the initial Froude number and step height. Finally, we compute the jump’s energy dissipation rate. Compared to the theoretical models for conjugate flow depth in a hydraulic jump, the proposed equation in this study fit the experimental data better, even for high steps and large initial Froude numbers. However, for low Froude numbers (F1 < 5), the equation was less accurate in estimating the jump length. Regarding the jump’s energy dissipation rate, the results agreed well with the experimental data from previous investigations. However, it is noted that the increased energy dissipation rate dwindled in larger Froude numbers.

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