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Appurtenances for Economic and Efficient Design of Transition Structures
Published in S.K. Mazumder, Flow Transition Design in Hydraulic Structures, 2020
Different characteristics of free hydraulic jump acting as a transition from supercritical to subcritical flow have been discussed in Section 2.4. Hydraulic jump is a useful device for energy dissipation below a spillway where there is transition from supercritical to subcritical flow. Free jump length is very high varying from four to six times the conjugate depth. This requires very long length of stilling basin as shown in Figures 2.22–2.24. Energy dissipation in a free jump is not so satisfactory. Moreover, a free jump is very sensitive with tail water variation. Forced hydraulic jump with appurtenances considerably reduces the basin cost and is effective too. Basin length is reduced drastically, the jump is stable, more efficient as energy dissipator and it does not leave the basin with small tail water variation.
Hydraulic Methods for Steady Flows
Published in James L. Martin, Steven C. McCutcheon, Robert W. Schottman, Hydrodynamics and Transport for Water Quality Modeling, 2018
James L. Martin, Steven C. McCutcheon, Robert W. Schottman
The relationship illustrated by Figure 6 and discussed in the two previous sections also has an additional implication for water movement and water quality. As illustrated by Figure 6, when the flow changes from supercritical to subcritical flow, an increase in depth must occur. This increase in depth is called a hydraulic jump, which can take place at the free surface of a homogeneous fluid or at the density interface of a stratified fluid (French 1985). A hydraulic jump increases turbulence and energy dissipation. French (1985) lists a number of applications where a hydraulic jump is desirable and can be included in the design of open-channel structures, such as for the dissipation of energy in flows over dams, weirs and other hydraulic structures (near the transition between a steep and mild slope) or in obtaining increased mixing of chemicals in water purification. Increased kinetic energy in hydraulic jumps can also increase mixing and reaeration in natural streams. Chow (1959), Henderson (1966), and French (1985) provide methods for computing of the location of a hydraulic jump. For typical water quality applications, the location of the hydraulic jump is known and its effects on water quality must be computed.
Culvert hydraulics
Published in James C. Y. Guo, Urban Flood Mitigation and Stormwater Management, 2017
Hydraulic jump involves a tremendous amount of energy dissipation through rolls and eddies in the turbulent flow. However, a jump only occurs if the required tailwater depth exists in the pool. Therefore, placing a weir at the end of the stilling basin is a common practice to raise the tailwater depth. Referring to Figure 11.22, the hydraulic jump is analyzed by the balance of specific forces between sections 1 and 2 as
Quantifying flow and velocity distributions in open channels with varied roughness and slopes: a modelling approach
Published in Water Science, 2023
Hajir Al Hindasi, Eyad Abushandi
The laboratory experiments were conducted to provide insights into velocity and flow distributions. The channel roughness and geometry have a significant influence on the flow and velocity characteristics and distributions. The datasets were collected at different slope ranges but the same initial flow rates. The velocity profiles were measured while the slope was changing, at four different points along the channels, to extract the precise, quantified relationship between velocity and flow with changing slopes. The velocity and flow behavior in the concrete channel showed continuously declining rates by moving from the water source to the end of the channel. However, this was not the case for the steel channel, where the velocity and flow behaviors show continuously rising rates, by moving from the source of the water to form a hydraulic jump at the end of the channel (Figure 4). The hydraulic jump indicates a sudden change from supercritical flow (high velocity and low depth) to subcritical flow (low velocity and high depth) within a short distance.
Energy dissipation for supercritical flows by using screens with triangular shape openings
Published in ISH Journal of Hydraulic Engineering, 2023
Ujjawal Kumar Singh, Parthajit Roy
According to the second law of thermodynamics, the conversion of kinetic energy to potential energy is accompanied by an increase in entropy. The transition process therefore includes a mechanism for energy dissipation. This cannot be accomplished by the skin friction alone and as there are no boundary features which can lead to the separation of streamlines, the depth must spontaneously jump from supercritical to subcritical, thus creating the necessary deceleration and turbulent eddies to dissipate the kinetic energy of the flow. The formation of a hydraulic jump requires a downstream flow impediment due to which water depth increases during a hydraulic jump, and energy is dissipated as turbulence. Commonly, the stilling basins equipped with different flow reducing techniques are used as an effective measure downstream of these aforesaid hydraulic structures to create and hold a hydraulic jump to dissipate the excess energy associated with the supercritical flow thus reducing the exit velocity (Chow 1959). In addition to this hydraulic jump-type energy dissipaters, drops (Chanson 1999; Carvalho and Leandro 2011), baffled outlets, vertical stilling wells, and sky jumps (Burgi 1975) are some impact-type energy dissipators.
Gene expression programming-based approach for predicting the roller length of a hydraulic jump on a rough bed
Published in ISH Journal of Hydraulic Engineering, 2021
Hamed Azimi, Hossein Bonakdari, Isa Ebtehaj
A hydraulic jump is a free surface flow occurrence, whereby the supercritical flow changes quickly to subcritical flow regime. Throughout a hydraulic jump, the supercritical flow depth and upstream Froude number are denoted as and respectively, and after the hydraulic jump the flow depth becomes accordingly. The distance between and is generally called the hydraulic jump length. The horizontal distance from the jump toe where the flow depth is until the end of the roller is defined as the roller length (Afzal et al. 2011). A schematic layout of a hydraulic jump over a rough bed is shown in Figure 1.