scholarly journals Effect of roughness on sequent depth in hydraulic jumps over rough bed

2019 ◽  
Vol 71 (2) ◽  
pp. 105-111
Author(s):  
Arpan Arunrao Deshmukh ◽  
Naveen Sudharsan ◽  
Avinash D Vasudeo ◽  
Aniruddha Dattatraya Ghare
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Hydraulic Jump ◽  
Open Channel ◽  
Hydraulic Jumps ◽  
Open Channel Flows ◽  
Downstream Side ◽  
Rough Bed ◽  
Sequent Depth ◽  
Rough Beds

Hydraulic jump is an important phenomenon in open channel flows such as rivers and spillways. Hydraulic jump is mainly used for kinetic energy dissipation at the downstream side of a spillway with the assist of baffle blocks. It has been demonstrated that corrugated or rough beds show considerably more energy dissipation than smooth beds. The experimental research evaluating the effect of crushed stones on the hydraulic jump is presented in this paper. Five different-size sets of crushed stones were used. Results show that the effect of rough bed does not increase after a certain height of crushed stone is reached.

scholarly journals Numerical Simulation of Hydraulic Jump over Rough Beds

2020 ◽  
Author(s):  
Saman Nikmehr ◽  
Younes Aminpour
Keyword(s):  
Numerical Model ◽  
Velocity Distribution ◽  
Hydraulic Jump ◽  
Surface Profile ◽  
Jump Length ◽  
Rough Bed ◽  
Sequent Depth ◽  
Rough Beds ◽  
Different Characteristics ◽  
Good Agreement

In this study, the hydraulic jumps over rough beds are numerically simulated. In order to calibrate the numerical model, the experimental data were used, which performed in a rectangular flume in various roughness arrangements and different Froude numbers. The effect of the distance (s) and the height (t) of the roughness on different characteristics of the hydraulic jump, including the sequent depth ratio, water surface profile, jump’s length, roller’s length, and velocity distribution were evaluated and compared. The results showed that the numerical model is fairly well able to simulate the hydraulic jump characteristics. The results also showed that the height and distance of roughness slightly reduced the sequent depth ratios for all Froude numbers. Also, the hydraulic jump length is reduced at the presence of the rough bed. Velocity profiles in different experiments were similar and there was a good agreement between simulated and measured results. Also, increasing the distance and the height of the roughness will slow down the velocity near the bed, increase the shear stress, and increase the gradient of the velocity distribution near the bed.

scholarly journals Predicting the relative energy dissipation of hydraulic jump in rough and smooth bed compound channels using SVM

2018 ◽  
Vol 19 (4) ◽  
pp. 1110-1119
Author(s):  
Seyed Mahdi Saghebian
Keyword(s):  
Energy Dissipation ◽  
Hydraulic Jump ◽  
Dominant Role ◽  
Rectangular Channel ◽  
Relative Energy ◽  
Support Vector ◽  
Channel Models ◽  
Rough Bed ◽  
Different Shapes ◽  
Rough Beds

Abstract Channels with different shapes and bed conditions are used as useful appurtenances to dissipate the extra energy of a hydraulic jump. Accurate prediction of hydraulic jump energy dissipation is important in design of hydraulic structures. In the current study, hydraulic jump energy dissipation was assessed in channels with different shapes and bed conditions (i.e. smooth and rough beds) using the support vector machine (SVM) as an intelligence approach. Five series of experimental datasets were applied to develop the models. The results showed that the SVM model is successful in estimating the relative energy dissipation. For the smooth bed, it was observed that the sloping channel models with steps performed more successfully than rectangular and trapezoidal channels and the step height is an effective variable in the estimation process. For the rough bed, the trapezoidal channel models were more accurate than the rectangular channel. It was found that rough element geometry is effective in estimation of the energy dissipation. The result showed that the models of rough channels led to better predictions. The sensitivity analysis results revealed that Froude number had the more dominant role in the modeling. Comparison among SVM and two other intelligence approaches showed that SVM is more successful in the prediction process.

Effect of aspect ratio on developing and developed narrow open channel flow with rough bed

2018 ◽  
Vol 45 (9) ◽  
pp. 780-794 ◽  
Author(s):  
Minakshee Mahananda ◽  
Prashanth Reddy Hanmaiahgari ◽  
Ram Balachandar
Keyword(s):  
Kinetic Energy ◽  
Aspect Ratio ◽  
Channel Flow ◽  
Open Channel ◽  
Reynolds Shear Stress ◽  
Open Channel Flow ◽  
Flow Region ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Rough Bed

This study attempts to unravel the effect of aspect ratio on the turbulence characteristics in developing and fully developed narrow open channel flows. In this regard, experiments were conducted in a rough bed open channel flow. Instantaneous 3D velocities were acquired using an acoustic Doppler velocimeter at various locations along the centerline of the flume. The variables of interest include the mean components of the flow velocity, turbulence intensity, wall normal Reynolds shear stress, correlation coefficient, turbulence kinetic energy, and anisotropy. A new correlation between the equivalent roughness and velocity shift from the smooth wall logarithmic equation as a function of aspect ratio is proposed. Aspect ratio was found to influence the velocity characteristics throughout the depth in the developing flow region, while the effects are confined to the outer layer for fully developed flows. New equations to describe the variation of turbulence intensities and turbulent kinetic energy are proposed for narrow open channel flows. Reynolds stress anisotropy analysis reveals that level of anisotropy in narrow open channel flow is less than in wide open channel flows. Finally, a linear regression model is proposed to predict flow development length in narrow open channel flows with a rough bed.

Velocity Distribution and Attenuation Characteristic in Hydraulic Jumps on Rough Beds

2021 ◽  
Author(s):  
Lei Wang ◽  
Ming-jun Diao
Keyword(s):  
Velocity Distribution ◽  
Hydraulic Jump ◽  
Maximum Velocity ◽  
Hydraulic Jumps ◽  
Attenuation Characteristic ◽  
Jump Length ◽  
Attenuation Rate ◽  
Rough Bed ◽  
Velocity Attenuation ◽  
Rough Beds

This study was conducted to investigate the velocity distribution and attenuation in free jumps on rough beds. Based on the length scale of jump length Lj, the velocity distribution of the free jump on a rough bed can be divided into four parts by three typical sections where are in the position of x=0.4Lj, x=0.8Lj, and x=1.2Lj. It seems that the velocity distribution near section x=0.4Lj is the most uneven. The velocity attenuation rate in the bottom half of the water is larger than that in the top half of the water. The attenuation of the maximum velocity um is mainly done from x=0 to x=0.8Lj. The results show the mixed triangular corrugated floor increases the resistance of hydraulic jump development and is very efficient in energy dissipation.

scholarly journals Effect of channel slope and roughness on hydraulic jump in open channel flow

2021 ◽  
Vol 958 (1) ◽  
pp. 012014
Author(s):  
K Laishram ◽  
P A Kumar ◽  
T T Devi
Keyword(s):  
Hydraulic Jump ◽  
Open Channel ◽  
Hydraulic Characteristics ◽  
Empirical Relationships ◽  
Channel Characteristics ◽  
Rough Bed ◽  
Channel Slope ◽  
Sloping Bed ◽  
Sequent Depth ◽  
The Impact

Abstract An experimental study is conducted on hydraulic jump characteristics for understanding the impact of slope in an open channel flume. Hydraulic jump on different channel characteristics (horizontal smooth & rough and sloping smooth & rough) were analysed. The measured characteristics of hydraulic jump with different channel roughness and different slope were compared. The results showed that the sequent depth ratio (y2/y1 ) increases with the increase in Froude number (Fr1 ) for smooth horizontal bed and horizontal rough bed. It was also observed that with an increase in Fr1 , a decrease in y2/y1 in smooth sloping bed condition and decreases for rough sloping bed. New empirical relationships were also developed with the experimental data and results were found similar with the observed hydraulic characteristics data.

On the definition of the shear velocity in rough bed open channel flows

2006 ◽  
Author(s):  
C Manes ◽  
D Pokrajac ◽  
I McEwan ◽  
J Finnigan ◽  
V Nikora
Keyword(s):  
Open Channel ◽  
Shear Velocity ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Rough Bed ◽  
Definition Of

The Baffle Blocks Effects of Pressure Characteristics on USBR III Basin Floor

2012 ◽  
Vol 212-213 ◽  
pp. 821-825
Author(s):  
Keyvan Nasiri ◽  
Mohammad Reza Kavianpour ◽  
Siavash Haghighi
Keyword(s):  
Energy Dissipation ◽  
Hydraulic Jump ◽  
Pressure Fluctuations ◽  
Power Spectra ◽  
Low Frequency ◽  
Dominant Frequency ◽  
Energy Dissipation Rate ◽  
Tension And Compression ◽  
Basin Floor ◽  
Sequent Depth

The principle of energy dissipation in stilling basin is based on hydraulic jump formation. Due to the inherent fluctuating characteristic of the hydraulic jump, basin floor is subjected to variations of pressure, resulting in unstableness due to uplift forces. To increase the efficiency of the stilling basins and improve the energy dissipation rate, one or two rows of baffle blocks are applied on the basin floor. Causing a forced hydraulic jump, tension and compression forces are exerted by pressure fluctuations of rotating roller zone of hydraulic jump. In this investigation, to observe the impacts of baffle blocks on pressure fluctuations on basin floor, a standard USBR basin model type III was constructed, and then a second row of blocks was added to the basin. A set of pressure tubes was fixed along the axis of the basin to measure the static and dynamic pressures on basin floor. The results were expressed in dimensionless parameters including C-p, C+p, C’p, Cp. Also, power spectra of pressure fluctuations were calculated. The results show a decreasing trend in root mean square of pressure fluctuations as distancing from toe of jump along the basin with and without baffle blocks. Also, mean pressure increases when water jet strokes the basin then decreases under roller zone of jump and increases again after sequent depth. The spectral analysis indicates that the dominant frequency is between 10 rad/s and 35 rad/s and pressure fluctuations have low frequency characteristics.

scholarly journals Hydraulic resistance in open-channel flows over self-affine rough beds

2018 ◽  
Vol 57 (2) ◽  
pp. 183-196 ◽  
Author(s):  
Mark T. Stewart ◽  
Stuart M. Cameron ◽  
Vladimir I. Nikora ◽  
Andrea Zampiron ◽  
Ivan Marusic
Keyword(s):  
Hydraulic Resistance ◽  
Open Channel ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Rough Beds

Turbulence anisotropy and intermittency in open-channel flows on rough beds

2020 ◽  
Vol 32 (11) ◽  
pp. 115127
Author(s):  
F. Coscarella ◽  
N. Penna ◽  
S. Servidio ◽  
R. Gaudio
Keyword(s):  
Open Channel ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Turbulence Anisotropy ◽  
Rough Beds

Three-dimensional study of spatial submerged hydraulic jump

2007 ◽  
Vol 34 (9) ◽  
pp. 1140-1148 ◽  
Author(s):  
H K Zare ◽  
R E Baddour
Keyword(s):  
Velocity Field ◽  
Hydraulic Jump ◽  
Three Dimensional ◽  
Head Loss ◽  
Acoustic Doppler Velocimeter ◽  
Hydraulic Jumps ◽  
Orthogonal Components ◽  
Sequent Depth ◽  
Channel Bottom ◽  
Submerged Hydraulic Jump

A three-dimensional (3D) study of spatial submerged hydraulic jumps (SSHJs) was carried out using a physical model for Froude numbers Fr1 = 2.00 and 3.75 and width ratios α = 0.20 and 0.33. Three orthogonal components of the velocity field were obtained with an acoustic Doppler velocimeter (ADV). The 3D velocity field has indicated that the jump consisted of a central jet-like flow, close to the channel bottom, surrounded by vertical and horizontal circulations (rollers). The circulation was predominantly in vertical planes in the channel central region of the flow and in horizontal planes close to the walls. Vertical and horizontal profiles of stream-wise velocity characterized the 3D roller with two length scales, Lrv and Lrh. The strength of the roller was stronger close to the walls than at the centreline of the jump. Sequent depth and energy head loss for submerged symmetric hydraulic jumps are discussed in terms of the submergence ratio S = y3/y2.Key words: hydraulic jump, spatial, submerged, roller length, sequent depth, energy dissipation.

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