Influence of Regular Surface Waves on the Propagation of Gravity Currents: Experimental and Numerical Modeling

Musumeci, Rosaria Ester; Viviano, Antonino; Foti, Enrico

doi:10.1061/(asce)hy.1943-7900.0001308

Cited by 13 publications

(24 citation statements)

References 47 publications

(71 reference statements)

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“…For example, Viviano and Musumeci et al [7][8][9] proposed simplified numerical models, which simulate turbulence by means of eddy viscosity formulation, to study the mechanism of waves. But when it comes to optimal design, computational fluid dynamics (CFD) turns out to be a better choice because it is more practical and it can overcome the limitations of experimental conditions [10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

et al. 2017

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Abstract:In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV) and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration based on field experiments and a finite element method (FEM) is presented. It is found that the resonance between the Kármán vortex and the stay vane is the main cause for the undesired vibration. Then, we focus on establishing an intelligent optimization model of the stay vane's trailing edge profile. To this end, an approach combining factorial experiments, extreme learning machine (ELM) and particle swarm optimization (PSO) is implemented. Three kinds of improved profiles of the stay vane are proposed and compared. Finally, the profile with a Donaldson trailing edge is adopted as the best solution for the stay vane, and verifications such as computational fluid dynamics (CFD) simulations, structural analysis and fatigue analysis are performed to validate the optimized geometry.

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Section: Introductionmentioning

confidence: 99%

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

et al. 2017

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“…The interaction between gravity currents and oscillatory motion has been investigated only in a few works [8,[27][28][29]. Ng and Fu [27] studied numerically the spreading of viscous gravity currents propagating in intermediate and deep water depth conditions, observing that wave-induced streaming flow acting at the bottom is responsible for changes in the gravity current velocity speed.…”

Section: Introductionmentioning

confidence: 99%

“…They adopted a point release technique and observed the self-similar phase of the two fronts respectively propagating under regular surface waves in deep water condition. Musumeci et al [28] investigated the propagation of gravity currents under regular surface waves, modeling the phenomenon both experimentally and numerically. The gravity currents were modeled assuming low density difference and intermediate water depth conditions and adopted the lock-exchange problem for the generation of the gravity current.…”

Section: Introductionmentioning

confidence: 99%

“…Such a model designed for engineering applications needs a previous careful calibration process to choose the calibration parameters of the Smagorinsky formulation. The recent work of Stancanelli et al [29] has explored a larger dataset compared to the one presented by Musumeci et al [28] evaluating the change of front velocity and mixing at the front of the current for a large number of wave types and different density fluid ratio conditions. They show that the front velocity is related to the Lagrangian mass transport induced by the surface waves, while the mixing observed at the front is related to the orbital motion.…”

Section: Introductionmentioning

confidence: 99%

“…To the authors' knowledge, this has never been attempted before. Indeed, previous works [28][29][30] were able only to comment on the 2D features of the turbulence structures, not taking into account small-scale structures. Numerical modeling is carried out by means of a computational fluid dynamics model (CFD).…”

Section: Introductionmentioning

confidence: 99%

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Computational Fluid Dynamics for Modeling Gravity Currents in the Presence of Oscillatory Ambient Flow

Stancanelli¹,

Musumeci²,

Foti³

2018

Water

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Gravity currents generated by lock release are studied in the case of initially quiescent ambient fluid and oscillating ambient fluid (regular surface waves). In particular, the dynamics of the density currents are investigated by means of CFD numerical simulations. The aim is to evaluate the influence of the ambient fluid velocity field on the observed mixing and turbulent processes. Results of two different turbulence closure models, namely the standard k − ε turbulence model and the LES model, are analyzed. Model predictions are validated through comparison with laboratory measurements. Results show that the k − ε model is able to catch the main current propagation parameters (e.g., front velocity at the different phases of the evolution of the current, gravity current depth, etc.), but that a LES model provides more realistic insights into the turbulent processes (e.g., formation of interfacial Kelvin-Helmholtz billows, vortex stretching and eventual break up into 3D turbulence). The ambient fluid velocity field strongly influences the dynamics of the gravity currents. In particular, the presence of an oscillatory motion induces a relative increase of mixing at the front (up to 25%) in proximity of the bottom layer, and further upstream, an increase of the mixing process (up to 60%) is observed due to the mass transport generated by waves. The observed mixing phenomena observed are also affected by the ratio between the gravity current velocity v f and the horizontal orbital velocity induced by waves u w , which has a stronger impact in the wave dominated regime (v f /u w < 1).

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Dynamics of Gravity Currents in the Presence of Surface Waves

2018

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The gravity current dynamics in the presence of regular surface waves is investigated experimentally. The aim is to determine the influence of the wave‐induced velocity field on gravity current kinematic parameters and on the concentration distribution. In the presence of surface waves, the front shows a pulsating behavior while periodic oscillations are observed at the interface between lighter and denser fluids. The dynamics of such processes is related to the wave parameters. Present results confirm that the lock‐exchange generated front velocity is strongly influenced by the oscillatory motion and it may be increased or decreased depending on the Lagrangian mass transport induced by the surface waves. Compared to the propagation in the absence of waves, the dynamics of the concentration field is governed by an enhancement of mixing process due to the orbital motion.

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Influence of Regular Surface Waves on the Propagation of Gravity Currents: Experimental and Numerical Modeling

Cited by 13 publications

References 47 publications

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

Computational Fluid Dynamics for Modeling Gravity Currents in the Presence of Oscillatory Ambient Flow

Dynamics of Gravity Currents in the Presence of Surface Waves

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