The Field of Flow Structures Generated by a Wave of Viscous Fluid Around Vertical Circular Cylinder Piercing the Free Surface

Tafarojnoruz

2020

Fluids

Self Cite

Ski jump spillways are frequently implemented to dissipate energy from high-speed flows. The general feature of this structure is to transform the spillway flow into a free jet up to a location where the impact of the jet creates a plunge pool, representing an area for potential erosion phenomena. In the present investigation, several tests with different ski jump bucket angles are executed numerically by means of the OpenFOAM® digital library, taking advantage of the Reynolds-averaged Navier–Stokes equations (RANS) approach. The results are compared to those obtained experimentally by other authors as related to the jet length and shape, obtaining physical insights into the jet characteristics. Particular attention is given to the maximum pressure head at the tailwater. Simple equations are proposed to predict the maximum dynamic pressure head acting on the tailwater, as dependent upon the Froude number, and the maximum pressure head on the bucket. Results of this study provide useful suggestions for the design of ski jump spillways in dam construction.

Section: Methodsmentioning

confidence: 99%

Flow Pressure Behavior Downstream of Ski Jumps

Lauria

Tafarojnoruz

2020

Fluids

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“…For the execution of the calculations, the Flow-3D [22][23][24] finite-volume computational code has been used. In this code, the free-surface condition is handled with the VOF (volume of fluid) [25] method, that has extensively proven to be able to accurately track a wave interface [26,27]. The VOF method has been already used by several authors [24,26,27], always giving satisfactory results.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Discharge Coefficients for Sluice Gates Set in Weirs at Different Upstream Wall Inclinations

Lauria

Calomino

et al. 2020

Water

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Laboratory experiments and numerical simulations are performed to measure discharge coefficients in the case of a gate located on the upstream wall of a weir for flood storage. The effect of the gate slope and the side contraction have been taken into account. The study was first performed experimentally, when three series of tests were carried out with (and without) a broad crested weir located under the gate, at different values of the inclination angle of the weir upstream wall, and at different values of the shape ratio and the relative opening. In order to provide useful suggestions for those involved in sluice gate construction and management, three equations were obtained based on multiple regression, relating the discharge coefficient to different parameters that characterize the phenomenon at hand, separating the case when the broad-crested weir was present. Then numerical simulations were executed by means of the Reynolds-averaged Navier–Stokes (RANS) equations with the k-ε turbulence closure model and in conjunction with the volume of fluid (VOF) method, to validate the numerical results against the experimental and to possibly investigate phenomena not caught by the experimental measurements. Simulated discharges were very close to the observed ones showing that the proposed three-dimensional numerical procedure is a favorable option to correctly reproduce the phenomenon.

“…The interFoam solver has been designed for incompressible, isothermal, immiscible fluids using the VoF (Volume of Fluid) phase -fraction based interface capturing approach [16]. The VoF method was used in many investigations (see References [17][18][19][20], among others). The VoF method, proposed by Hirt and Nichols [17], locates and tracks the free surface flow.…”

Section: Numerical Solutionmentioning

confidence: 99%

Experimental and Numerical Study of Free-Surface Flows in a Corrugated Pipe

Calomino

Gaudio

et al. 2018

Water

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A new discharge computational model is proposed on the basis of the integration of the velocity profile across the flow cross-section in an internally corrugated pipe flowing partially full. The model takes into account the velocity profiles in the pressurised pipe to predict the flow rate under free-surface flow conditions. The model was evaluated through new laboratory experiments as well as a literature datasets. The results show that flow depth and pipe slope may affect the model accuracy; nevertheless, a prediction error smaller than 20% is expected from the model. Experimental results reveal the influence of the pipe slope and flow depth on the friction factor and the stage-discharge curves: the friction factor may increase with pipe slope, while it reduces as flow depth increases. Hence, a notable change of pipe slope may lead to the variation of the stage-discharge curve. A part of this study deals with numerical simulation of the velocity profiles and the stage-discharge curves. Using the Reynolds-Averaged Navier-Stokes (RANS) equations, numerical solutions were obtained to simulate four experimental tests, obtaining enough accurate results as to velocity profiles and water depths. The results of the simulated flow velocity were used to estimate the flow discharge, confirming the potential of numerical techniques for the prediction of stage-discharge curves.Reference [4]. On the other hand, there are few studies on the friction factor and velocity profiles of corrugated pipes under free-surface flow conditions. The following paragraphs point to the previous studies on the hydraulics of corrugated pipes under free-surface flow conditions. An earlier study on flow resistance of three relatively large corrugated pipes under both full-pipe and free-surface flow conditions was performed by Webster and Metcalf [5]. The employed pipes were 3, 5, and 7 ft in diameter. That study mainly focused on the velocity profile and friction factor of the selected pipes under full-pipe flow conditions with less attention to the flow resistance of the pipes under free-surface flow. Nevertheless, the finding of Webster and Metcalf [5] about the value of Manning's n when the pipes convey the flow under free-surface conditions is quite interesting: they concluded that Manning's n for free-surface flow is almost independent of the flow depth and is around the value of 0.024 s/m 1/3 obtained for full-pipe flow conditions.Ead et al. [6] derived empirical equations to predict the flow velocity pattern within a steel corrugated pipe. The measurement of the velocity profiles was conducted at the pipe centreline axis as well as at the different lateral distances from the central vertical plane. Ead et al. [6] reported that the well-known Prandtl equation for the rough wall is valid to predict the velocity profile at a region near the corrugations, whereas, after a certain distance from the corrugations, there would be a deviation from the logarithmic line. The proposed equations by Ead et al. [6] may be used to predict the location w...