scholarly journals Application of a model of internal hydraulic jumps

2017 ◽  
Vol 834 ◽  
pp. 125-148 ◽  
Author(s):  
S. A. Thorpe ◽  
J. Malarkey ◽  
G. Voet ◽  
M. H. Alford ◽  
J. B. Girton ◽  
...  
Keyword(s):  
Hydraulic Jump ◽  
Mixing Layer ◽  
Strong Support ◽  
Deep Ocean ◽  
Hydraulic Jumps ◽  
Model Predictions ◽  
Mode 2 ◽  
Mediterranean Outflow ◽  
Unknown Structure ◽  
Internal Hydraulic Jump

A model devised by Thorpe & Li (J. Fluid Mech., vol. 758, 2014, pp. 94–120) that predicts the conditions in which stationary turbulent hydraulic jumps can occur in the flow of a continuously stratified layer over a horizontal rigid bottom is applied to, and its results compared with, observations made at several locations in the ocean. The model identifies two positions in the Samoan Passage at which hydraulic jumps should occur and where changes in the structure of the flow are indeed observed. The model predicts the amplitude of changes and the observed mode 2 form of the transitions. The predicted dissipation of turbulent kinetic energy is also consistent with observations. One location provides a particularly well-defined example of a persistent hydraulic jump. It takes the form of a 390 m thick and 3.7 km long mixing layer with frequent density inversions separated from the seabed by some 200 m of relatively rapidly moving dense water, thus revealing the previously unknown structure of an internal hydraulic jump in the deep ocean. Predictions in the Red Sea Outflow in the Gulf of Aden are relatively uncertain. Available data, and the model predictions, do not provide strong support for the existence of hydraulic jumps. In the Mediterranean Outflow, however, both model and data indicate the presence of a hydraulic jump.

scholarly journals IDDES Evaluation of Oscillating Hydraulic Jumps

2018 ◽  
Vol 40 ◽  
pp. 05067 ◽  
Author(s):  
Vimaldoss Jesudhas ◽  
Frédéric Murzyn ◽  
Ram Balachandar
Keyword(s):  
Flow Field ◽  
Hydraulic Jump ◽  
Three Dimensional ◽  
Wall Jet ◽  
Hydraulic Jumps ◽  
Vortical Structures ◽  
Instantaneous Flow Field ◽  
Type Flow ◽  
Different Types ◽  
Flow Features

This paper presents the results of three-dimensional, unsteady, Improved Delayed Detached Eddy Simulations of an oscillating and a stable hydraulic jump at Froude numbers of 3.8 and 8.5, respectively. The different types of oscillations characterised in a hydraulic jump are analysed by evaluating the instantaneous flow field. The instability caused by the flapping wall-jet type flow in an oscillating jump is distinct compared to the jump-toe fluctuations caused by the spanwise vortices in the shear layer of a stable jump. These flow features are accurately captured by the simulations and are presented with pertinent discussions. The near-bed vortical structures in an oscillating jump is extracted and analysed using the λ2 criterion.

Effect of diurnal temperature variation on the hydraulics of clarifiers

1991 ◽  
Vol 18 (6) ◽  
pp. 1084-1087 ◽  
Author(s):  
Anna M. Godo ◽  
J. A. McCorquodale
Keyword(s):  
Hydraulic Jump ◽  
Richardson Number ◽  
Wall Jet ◽  
Density Currents ◽  
Thermally Induced ◽  
Primary Model ◽  
Internal Hydraulic Jump ◽  
Diurnal Temperature Variation ◽  
End Wall ◽  
Made In

This study was carried out to obtain data on the behaviour of thermally induced density currents in primary rectangular clarifiers so that better models can be developed for these units. This note deals with the case when the influent is cooler than the ambient temperature in the tank. The experiments were made in a model with a scale of about 1:20 compared to the typical full-scale clarifier. Temperature surveys and dye tests were carried out for turbulent flow and temperature differences between influent and effluent that were equivalent to ±0.2 °C in the prototype on a diurnal basis. The results indicate six flow regimes that follow a decrease in influent temperature: (i) denser wall jet; (ii) splash at the end wall; (iii) moving internal hydraulic jump; (iv) submerged internal hydraulic jump; (v) splash at the influent baffle; and (vi) stratified flow. A comparison of the test data with those available in the literature showed that the entrainment equations involving the Richardson number are adequate for modelling, but the classical hydraulic jump equations need modifications for the effect of entrainment. Key words: clarifiers, rectangular, primary, model, density currents, internal hydraulic jumps, unsteady flow, denser wall jets.

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.

What is the final size of turbulent mixing zones driven by the Faraday instability?

2017 ◽  
Vol 837 ◽  
pp. 293-319 ◽  
Author(s):  
B.-J. Gréa ◽  
A. Ebo Adou
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Mixing Layer ◽  
Strong Support ◽  
Large Set ◽  
Mixing Zone ◽  
Final Size ◽  
Final State ◽  
Weakly Nonlinear ◽  
Faraday Instability

Miscible fluids of different densities subjected to strong time-periodic accelerations normal to their interface can mix due to Faraday instability effects. Turbulent fluctuations generated by this mechanism lead to the emergence and the growth of a mixing layer. Its enlargement is gradually slowed down as the resonance conditions driving the instability cease to be fulfilled. The final state corresponds to a saturated mixing zone in which the turbulence intensity progressively decays. A new formalism based on second-order correlation spectra for the turbulent quantities is introduced for this problem. This method allows for the prediction of the final mixing zone size and extends results from classical stability analysis limited to weakly nonlinear regimes. We perform at various forcing frequencies and amplitudes a large set of homogeneous and inhomogeneous numerical simulations, extensively exploring the influence of initial conditions. The mixing zone widths, measured at the end of the simulations, are satisfactorily compared to the predictions, and bring a strong support to the proposed theory. The flow dynamics is also studied and reveals the presence of sub-harmonic as well as harmonic modes depending on the initial parameters in the Mathieu phase diagram. Important changes in the flow anisotropy, corresponding to the large scale structures of turbulence, occur. This phenomenon appears directly related to the orientation of the most amplified gravity waves excited in the system, evolving due to the enlargement of the mixing zone.

scholarly journals Turbulence at Free Surface in Hydraulic Jumps

Volume 1 ◽  
2004 ◽  
Author(s):  
D. Mouaze ◽  
F. Murzyn ◽  
J. R. Chaplin
Keyword(s):  
Free Surface ◽  
Mixing Layer ◽  
Hydraulic Jumps ◽  
Similar Data ◽  
Two Phase ◽  
Length Scales ◽  
Phase Measurements ◽  
Void Fractions ◽  
Cross Correlation Analysis ◽  
Turbulence Length

In the context of recent work by Brocchini & Peregrine [1,2], this paper aims to document free surface profiles, and turbulence length scales in hydraulic jumps with Froude numbers between 1.98 and 4.82. Although information on bubble size, frequency and velocities in hydraulic jumps is available in the literature, there is not much data on the features of the free surface, or on mixing layer thickness. In the present case, measurements at the free surface have been realized with two miniature resistive wire gauges each comprising two parallel 50 micron diameter wires with a separation of 1mm. These instruments were calibrated dynamically over a range of frequencies up to 20 Hz. Furthermore optical probes were used to measure properties of the air phase within the jump, including void fractions (up to 98%). The present results extend the range of Froude numbers for which two-phase measurements in hydraulic jumps are available, and, in most respects, confirm earlier results obtained with different experimental techniques. Length scales at the free surface are deduced from cross-correlation analysis of wire gauge measurements, and are compared with similar data obtained from images of the surface.

The Effect of Initial Momentum Flux on the Circular Hydraulic Jump

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
K. P. Vishwanath ◽  
Ratul Dasgupta ◽  
Rama Govindarajan ◽  
K. R. Sreenivas
Keyword(s):  
Numerical Simulations ◽  
Hydraulic Jump ◽  
Momentum Flux ◽  
Fluid Viscosity ◽  
Hydraulic Jumps ◽  
Initial Momentum ◽  
Flow Parameters ◽  
Controlling Parameter ◽  
Study Results ◽  
Wide Range

Earlier studies on the circular hydraulic jump have shown that the radial position of the hydraulic jump depends on the flow rate, gravity, and fluid viscosity. In this study, results from numerical simulations and experiments on circular hydraulic jumps are presented and through analysis, it is shown that the momentum flux is an additional controlling parameter in determining the jump location. Apart from the jump location, the variation of the film thickness with flow parameters is also obtained from experiments and numerical simulations. By including the dependence of the momentum flux and dissipation in the film along with other controlling parameters, the data on jump radius obtained from experiments and simulation (including the present study) covering a wide range of parameters reported in the literature can be collapsed on to a single curve.

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