An experimental investigation of the stability of the circular hydraulic jump (original) (raw)
Numerical Study of Circular Hydraulic Jump Using Volume-of-Fluid Method
Journal of Fluids Engineering, 2011
When a vertical liquid jet impacts on a solid and horizontal surface, the liquid starts spreading radially on the surface, until a sudden increase in the fluid height occurs and a circular hydraulic jump (CHJ), easily seen in the kitchen sink, is formed. In this study, the formation of CHJ is numerically simulated by solving the flow governing equations, continuity and momentum equations, along with an equation to track the free surface advection using the volume-of-fluid (VOF) method and Youngs’ algorithm. The numerical model is found to be capable of simulating the jump formation and its different types. Extensive comparisons are performed between the model results and those of the available experiments and modified Watson’s theory. The model is shown to accurately predict the jump location and its behavior. Also a parametric study for the effects of different parameters including volumetric flow rate, downstream height, viscosity and gravity on the jump radius, and its characteri...
Instabilities and elastic recoil of the two-fluid circular hydraulic jump
Experiments in Fluids, 2014
The two-fluid circular hydraulic jump, also called ''rinsing flow,'' is a common process where a jet of one liquid impinges upon a layer of a second liquid. We present an experimental analysis of rinsing flows using a high-speed camera and model fluids to decouple the effect of shear-thinning and elasticity. Varying the rheology of the coating fluid produced several types of instabilities at both the air-liquid interface and liquid-liquid interface. Layered ''stepped jumps'' and ''crowning'' on the rim of the jumps were both suppressed by fluid elasticity, while Saffman-Taylor fingering patterns showed strong dependence on both shear-thinning and normal stresses. In addition, the hydraulic jump evolution was quantitatively determined using a laser triangulation technique, and ''recoil'' of the jump front resulting from fluid elasticity was observed. Our work shows that the non-Newtonian two-fluid circular hydraulic jump is very complex, and the instabilities that arise also introduce additional complications when developing theoretical models.
Circular Hydraulic Jumps Triggered by Boundary Layer Separation
Journal of Colloid and Interface Science, 2001
When a high-flow-rate circular jet impinges vertically on a horizontal plane, it flows out radially and then undergoes a distinctive hydraulic jump on the plane because of boundary layer separation induced by hydrostatic back pressure. The jump radius is shown to be 0.37 a Re 1/3 −1/8 , where = (ga 3 /ν 2 ) Re −7/3 is a modified Froude number, Re = (Q/aν) is the jet Reynolds number, a is the jet radius, and Q the liquid flow rate, which is favorably compared to experimental data in the limit of small . When exceeds 3.0 × 10 −4 at low flow rates, the jump radius decreases below a minimum in the film depth and our experiments detect a different jump mechanism that may be triggered by capillary pressure rather than hydrostatic pressure. C 2001 Academic Press
Circular hydraulic jumps: where does surface tension matter?
Journal of Fluid Mechanics, 2022
Recently, an unusual scaling law has been observed in circular hydraulic jumps and has been attributed to a supposed missing term in the local energy balance of the flow (Bhagat et al., J. Fluid Mech., vol. 851, 2018, R5). In this paper, we show that – though the experimental observation is valuable and interesting – this interpretation is presumably not the right one. When transposed to the case of an axial sheet formed by two impinging liquid jets, the assumed principle leads in fact to a velocity distribution in contradiction with the present knowledge for this kind of flow. We show here how to correct this approach by maintaining consistency with surface tension thermodynamics: for Savart–Taylor sheets, when adequately corrected, we recover the well-known 1/r1/r1/r liquid thickness with a constant and uniform velocity dictated by Bernoulli's principle. In the case of circular hydraulic jumps, we propose here a simple approach based on Watson's description of the flow in the ...
The Impingement of a Normal Liquid Jet on a Horizontal Surface
Spanish Journal of Agricultural …, 2009
In this study, the impingement of a vertical liquid jet on a solid horizontal surface which leads to the formation of a circular hydraulic jump (CHJ) is numerically simulated by using the Volume-of-Fluid (VOF) method. The results show that increasing the volumetric flow rate will increase the radius of the jump which is confirmed by the experimental observations. Also, the numerical results are compared with the CHJ observed in experiments and that of the theory.
steel research international, 2012
Liquid jet impingement has many industrial cooling applications such as metal manufacturing and steel cooling on run-out tables (ROT). The development of the wetting front around the impingement point of a jet is central in jet impingement cooling. In this paper, the effects of moving target surface and jet Reynolds number on wetted zone and on the formation and location of hydraulic jump (HJ) are explored through a series of industrial-scale experiments of an impinging circular free surface long water jet with high Reynolds number of 11 000-50 000 and industrial jet parameters. The moving test surface impacts the radial evolution of circular wetted zone in all directions and alter the circular HJ at the wetting front into a non-circular contour that depends on the jet Re number. The limited relations in the literature do not represent these measured shapes and do not appropriately predict radii of HJ in industrial scale. A new correlation for radius of noncircular HJ has been derived in this study that compared more accurately to the experimental data. Numerical simulations of radial impingement flow on moving surface were performed using a variant of k-e turbulent model and results are compared to the experimental data. The computational results for the wetting front were found to be close to the experimental data indicating the appropriate performance of the turbulent model.
Experimental observations on undular hydraulic jumps with very high aspect ratio
Experimental data regarding jumps with very high aspect ratios are very rare in literature, therefore experimental works are necessary. The present paper analyses the formation of undular hydraulic jumps in a very large channel, characterized by a 4.0 m width, for low Reynolds number. Once observed that the investigated jumps were characterized by the formation of lateral shock waves, the purpose of the present work is both to analyse the flow conditions of undular jumps and to verify the experimental validity of the classic shock wave theory in very large channels. Seven experimental tests were carried out and their results can be summarized in the following way: (i) the presence of well developed lateral shock waves similar to those of oblique jumps were observed; (ii) the comparison of the experimental and the theoretical data show that the classical shock wave theory is confirmed, taking into account the experimental errors; (iii) the literature law of the wave height of first w...
Fluid Dynamics Research, 2019
The interaction of a light tungsten wire-array Z-pinch with an embedded heavy foam converter, whose mass ratio is typically less than 0.16, is numerically analyzed and experimentally investigated on the 1.3 MA "QiangGuang I" facility. Computational results show that this implosion process can be divided into three stages: acceleration of the tungsten wire-array plasma, collision, and stagnation. The tungsten plasma is accelerated to a high speed by the J Â B force and interacts weakly with the foam plasma in the first stage. Strong energy conversions take place in the second collision stage. When the high speed tungsten plasma impacts on the foam converter, the plasma is thermalized and a radial radiation peak is produced. Meanwhile, a shock wave is generated due to the collision. After the shock rebounds from the axis and meets the W/Foam boundary, the plasma stagnates and the second radial radiation peak appears. The collision and stagnation processes were observed and the two-peak radial radiation pulse was produced in experiments. Increasing the wire-array radius from 4 mm to 6 mm, the kinetic energy of the tungsten plasma is increased, causing a stronger thermalization and generating a higher first radiation peak. Experimental results also showed a higher ratio of the first peak to the second peak in the case of larger wire-array radius. If we add a thin CH film cover onto the surface of the embedded foam converter, the first radiation peak will be hardly changed, because the acceleration of the tungsten plasma is not evidently affected by the film cover. However, the second radiation peak decreases remarkably due to the large load mass and the corresponding weak compression.
Numerical and Experimental Study of Classical Hydraulic Jump
Water, 2020
The present work is an effort to simulate numerically a classical hydraulic jump in a horizontal open channel with a rectangular cross-section, as far as the jump location and free surface elevation is concerned, and compare the results to experiments with Froude numbers in the range 2.44 to 5.38. The governing equations describing the unsteady one-dimensional rapidly varied flow have been solved with the assumption of non-hydrostatic pressure distribution. Two finite difference schemes were used for the discretization of the mass and momentum conservation equations, along with the appropriate initial and boundary conditions. The method of specified intervals has been employed for the calculation of the velocity at the downstream boundary node. Artificial viscosity was required for damping the oscillations near the steep gradients of the jump. An iterative algorithm was used to minimize the difference of flow depth between two successive iterations that must be less than a threshold...
Hydraulic Jump: A Brief History and Research Challenges
Water, 2021
This paper presents a brief history of the hydraulic jump and a literature review on hydraulic jumps’ experimental and numerical studies. Leonardo da Vinci noticed this phenomenon early on, but it was only later studied by Bidone in 1820. Since the beginning of the 20th century, the hydraulic jump has received a lot of attention following the development of energy dissipater designs and stilling basins. The late 1920s and early 1930s saw many experimental studies researching the surface roller profile and energy dissipation. The study of internal flow features started in the late 1950s. Starting in the 70s, it was believed that the flow of a jump must be analyzed in its actual configuration of air–water mixture, an aspect that cannot be overlooked. Several experimental studies in the late 1980s and 1990s highlighted the existence of oscillating phenomena under specific flow conditions and particularly, a cyclic variation of jump types over long-lasting experiments. The early 2000s s...