Hydraulic jump characteristics in non-prismatic channels (original) (raw)

Hydraulic Jumps in a Straight Rectangular Compound Channel: Theoretical Approach and Experimental Study

LARHYSS Journal, 2017

In this paper, theoretical developments, regarding the establishment of dimensionless relationships for sequent depths ratio and relative energy loss of hydraulic jumps are achieved in a straight rectangular compound channel. These relationships were given with and without consideration of a volume force Fx , which is assimilated by analogy to Borda-Carnot’s expression. The Experiment was carried out with three different values of the width ratio τ y . For each τ y ratio, several values of inflow Froude number were considered according to the five inflow ratio depths’ values τ z . The experiments proved the validity of the proposed theoretical relationships. The study showed the need to consider the force Fx when the ratio τ y reaches the value of 0.5. It reveals also the practical usefulness of the compound channel in terms of energy dissipation capability compared to the rectangular channel.

Modeling of Relative Length and Relative Energy Loss of Free Hydraulic Jump in Horizontal Prismatic Channel

Procedia Engineering, 2013

Hydraulic jump is a phenomenon caused by change in stream regime from supercritical to sub-critical flow with considerable energy dissipation and rise in depth of flow. Hydraulic jump primarily serves as an energy dissipater to dissipate excess energy of flowing water downstream of hydraulic structures, such as spillway, sluice gates etc. This excess energy, if left unchecked, will have adverse effect on the banks and the bed. A review of literature has shown that earlier researcher have studied the hydraulic jump characteristics in terms of approach Froude number (Fr 1) only. In the present paper hydraulic jump in horizontal prismatic channel has been studied and analyzed considering the effect of both approach Froude number and incoming Reynolds number (Re 1). Empirical models for relative length and relative energy loss of free hydraulic jump based on experimental data using Buckingham-theorem and regression analysis have been developed considering the effect of approach Froude number and incoming Reynolds number. The developed empirical computational model is validated using Bhutto (1987) data.

Correlation among Hydraulic Parameters of Moving Hydraulic Jump in Rectangular Open Channels

Engineer: Journal of the Institution of Engineers, Sri Lanka, 2016

The moving hydraulic jump is a phenomenon, which is often observed in field conditions. Since the parameters of moving hydraulic jump vary with time, analytical equations cannot be used to derive relationships among hydraulic jump parameters. Experimental investigations were carried out to study the relationships among hydraulic parameters of a moving hydraulic jump in a rectangular flume. A sluice gate was used to generate moving hydraulic jumps along the channel by changing the inflow to the channel. The flow parameters were recorded for the moving hydraulic jump produced for different sluice gate opening sizes. Based on the recorded data, flows parameters such as specific energy, flow rate and pressure force at downstream of the hydraulic jump were calculated. Also, using momentum and energy equations time independent relationships were obtained. The relationship among moving hydraulic jump parameters were obtained in non dimensional form. The correlations between stationary and moving hydraulic jump parameters such as specific energy, flow rate, pressure force and flow depth were derived in a non dimensional format

Experimental study of the hydraulic jump length in a smooth trapezoidal channel

Scientific Review Engineering and Environmental Studies (SREES), 2022

The paper showed the result of investigation of the hydraulic jump length in a trapezoidal channel. In this study, the basic factors that affect the length (Lj) and roller length (Lr) of the hydraulic jump were investigated by a physical trapezoidal channel’s model. The experiment carried out in purpose to establish a new empirical equation for calculating the roller length (Lr) of the jump in the horizontal trapezoidal channel with the upstream Froude number 4.0 to 9.0 (the steady jump). The hydraulic characteristics of forced jump were measured and statistically calculated using MS Excel software. The results of data analysis showed that the MAPE was relatively small (< 5%), and R2 > 0.9 (strong correlation between predicted and observed values) and other statistical indicators are less than 0.1 (MSE = 0.004, RMSE = 0.062, MEA = 0.047). Therefore, the equation found could be appropriated and applied to calculate characteristics of hydraulic jump trapezoidal channel.

Hydraulic jump in circular and U-shaped channels

Journal of Hydraulic Research, 2006

The Reynolds equations of mean turbulent flow in a two dimensional open channel of arbitrary cross section have been analysed. An integral equation for the turbulent hydraulic jump is proposed. In the closure model adopted, the depth averaged effective normal Reynolds stress is taken proportional to the product of constant eddy viscosity and depth averaged axial velocity gradient, and the constant of proportionality that is independent of channel geometry. The general theory has been applied to the flows in circular and U-shaped channels. The solutions for sequent depth, hydraulic jump length, roller length and aeration length have been estimated. The comparison of the theory with experimental data of Hager and Stahl for circular and U-shaped channels give very encouraging results.

Characteristics Of Hydraulic Jump

2014

The effect of an abruptly expanding channel on the main characteristics of hydraulic jump is considered experimentally. The present study was made for supercritical flow of Froude number varying between 2 to 9 and approach to expanded channel width ratios 0.4, 0.5, 0.6 and 0.8. Physical explanations of the variation of these characteristics under varying flow conditions are discussed based on the observation drawn from experimental results. The analytical equation for the sequent depth ratio in an abruptly expanding channel as given by eminent hydraulic engineers are verified well with the experimental data for all expansion ratios, and the empirical relation was also verified with the present experimental data.

Investigation of the Perfect Hydraulic Jump in Horizontal Rectangular Channel

مجلة الجامعة الأسمرية: العلوم التطبيقية

Accelerating the process of transition from supercritical to subcritical flow, by formation a forced hydraulic jump at the contract section (Forced perfect hydraulic jump), is one of the most important measures, in decreasing flow velocity, water energy dissipation and alleviation the scouring problem, leading to lessening the required protection length against the erosion issues in the bed of downstream of the channel. In the current study, physical model was prepared precisely at fluid mechanics laboratory in the faculty of Engineering/Alkhums at Elmergib University. Comprehensive experiments were conducted to evaluate measured and calculated characteristics of the perfect free jump, and consequently, the existence of the perfect hydraulic jump is investigated. Eventually, equation was derived that might be used to guarantee the existence of a free perfect jump, which is the limiting condition between both repelled and drowned jumps as well as, the limiting condition between both ...

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

2021

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 j...

Prediction of Sequent Depth Ratio of Hydraulic Jump in Abruptly Expanding Channel

A simple prediction model for computing sequent depth ratio of hydraulic jumps in abruptly expanding rectangular channel has been presented. The basic prediction equation is derived based on the application of one-dimensional momentum and continuity equations. The format of the derived equation is similar to well-Known Belanger equation for classical jump with modification in Froude number. The modified Froude number term of the derived equation contains two additional parameters, one of them incorporates the effect of abrupt expansion and the second one represents for describing the position of jump upstream the expansion . Experimental data from other sources are used to calibrate and verify the developed model for different positions of jumps. Prediction of sequent depth ratio resulted from the present model shows reasonable agreement with the experimental data and the data generated using the approaches developed by the other investigators.

Uncertainty analysis regarding evaluating effective parameters on the hydraulic jump characteristics of different shape channels

Water Supply

The hydraulic jump phenomenon is a beneficial tool in open channels for dissipating the extra energy of the flow. The sequent depth ratio and hydraulic jump length critically contribute to designing hydraulic structures. In this research, the capability of the Support Vector Machine (SVM) and Gaussian Process Regression (GPR) as kernel-based approaches was evaluated to estimate the features of submerged and free hydraulic jumps in channels with rough elements and various shapes, followed by comparing the findings of the GPR and SVM models and the semi-empirical equations. The results represented the effect of the geometry (i.e., steps and roughness elements) of the applied appurtenances on hydraulic jump features in channels with appurtenances. Moreover, the findings confirmed the significance of the upstream Froude number in the estimating of sequent depth ratio in submerged and free hydraulic jumps. In addition, the immersion was the highest contributing variable regarding the sub...