Large-eddy simulation of shallow turbulent wakes behind a conical island

Ouro, Pablo; Wilson, Catherine; Evans, Paul; Angeloudis, Athanasios

doi:10.1063/1.5004028

Cited by 27 publications

(18 citation statements)

References 45 publications

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“…A. Numerical framework Eddy-resolving simulations are accomplished using the in-house code Hydro3D which has been well-validated in hydro-environmental flows [32][33][34][35][36][37] . Hydro3D adopts the Large-Eddy Simulation (LES) approach to explicitly resolve the energy-containing flow structures while modelling the scales smaller than the grid size using a sub-grid scale model.…”

Section: Computational Methods and Set-upmentioning

confidence: 99%

“…The hydrodynamic forces generated on the cylinder are impacted by the asymmetric flow field developed around the cylinder owing to both its proximity to the bed and the upstream velocity logarithmic distribution. The cylinder forces are directly calculated from the immersed boundary method 36 in the horizontal and vertical directions, F x and F z respectively, and are used to calculate the drag (C D ) and lift (C L ) coefficients given by:…”

Section: F Dominant Shedding Frequency and Hydrodynamic Coefficientsmentioning

confidence: 99%

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Asymmetric wake of a horizontal cylinder in close proximity to a solid boundary for Reynolds numbers in the subcritical turbulence regime

2019

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Section: Computational Methods and Set-upmentioning

confidence: 99%

Section: F Dominant Shedding Frequency and Hydrodynamic Coefficientsmentioning

confidence: 99%

Asymmetric wake of a horizontal cylinder in close proximity to a solid boundary for Reynolds numbers in the subcritical turbulence regime

2019

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“…Flows around a wall-mounted circular cylinder appear in a large number of technical and environmental applications, such as river flows past bridge piers and pile foundations [1][2][3]. When the natural wall-bounded flow encounters a vertical cylinder, horseshoe vortices (HVs) are formed in the junction region between the bed and the cylinder [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

Chen

Yang

2019

Water

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A turbulent horseshoe vortex (HV) system around a wall-mounted cylinder in open channel is characterized by random variations in vortex features and an abundance of vortex interactions. The turbulent HV system is responsible for initiating the local scour process in front of the cylinder. The evolution of the turbulent HV system is investigated statistically and quantitatively with time-resolved particle image velocimetry. The cylinder Reynolds numbers of the flow are 8600, 10,200, and 13,600, respectively. A novel vortex tracking method was proposed to obtain the variations in position, size, and strength of the primary HV (PHV) which dominates the system most of the time. Relationships between the various features of the PHV during its evolutionary process were obtained through correlation analyses. Results show that the dimensionless mean lifespan of the PHV is about 5.0. Statistically, the downstream movement of the PHV toward the cylinder is accompanied with its bed-approaching movement and decreasing in size, and the opposite is true. The circulation strength of the PHV decreases and increases dramatically in the region downstream of its time-averaged position when the PHV approaches and departs from the cylinder, respectively. Meanwhile, mechanisms responsible for the generation, movement, variation, and disappearance of the PHV are re-investigated and enriched based on its interactions with vortices in the separation region and structures in the incoming flow. The obtained change trends of the features of the PHV and the underlying mechanisms for its evolution are valuable for predicting and controlling the initial stage of the local scour in front of cylinders.

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“…The fluid flow was resolved using Hydro3D, a well-validated LES research code [28][29][30][31][32][33][34], including geometry-resolved simulations of vertical axis turbines [4,15] and the validation of an ALM for HATs [35]. The governing equations resolved in Hydro3D are the spatially filtered Navier-Stokes equations for turbulent, incompressible, three-dimensional flow:…”

Section: Large-eddy Simulationmentioning

confidence: 99%

An Actuator Surface Model to Simulate Vertical Axis Turbines

Massie

Ouro²,

Stoesser

et al. 2019

Energies

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An actuator surface model (ASM) to be employed to simulate the effect of a vertical axis turbine on the hydrodynamics in its vicinity, particularly its wake is introduced. The advantage of the newly developed ASM is that it can represent the complex flow inside the vertical axis turbine's perimeter reasonably well, and hence, is able to predict, with a satisfying degree of accuracy, the turbine's near-wake, with a low computational cost. The ASM appears to overcome the inadequacy of actuator line models to account for the flow blockage of the rotor blades when they are on the up-stream side of the revolution, because the ASM uses a surface instead of a line to represent the blade. The ASM was used on a series of test cases to prove its validity, demonstrating that first order flow statistics-in our study, profiles of the stream-wise velocity-in the turbine's vicinity, can be produced with reasonable accuracy. The prediction of second order statistics, here in the form of the turbulent kinetic energy (TKE), exhibited dependence on the chosen grid; the finer the grid, the better the match between measured and computed TKE profiles.Energies 2019, 12, 4741 2 of 16 thus, reducing noise and fish mortality [4]; and finally, the wake generated by a VATT recovers quickly, which is particularly beneficial in the context of turbine array design and optimisation [5].One of the earliest experimental studies on VATTs, from Brochier et al. in 1986 [6], provided a concise description of vortex shedding of VAT blades in a dynamic stall through flow visualisation and velocity profile measurements. Subsequent contributions then built upon these findings to render a comprehensive picture of the processes involved in the formation and recovery of the wake of a rotating VAT [5,[7][8][9][10][11][12][13]; to record quantitative data for use in numerical model validation [5,8,11,12]; and to investigate the performance of different turbines or turbine configurations [9,14]. The flow-dynamics have been shown to be strongly dependent on the tip-speed ratio (TSR) of the turbine, with the Reynolds number having little effect on the wake [7]. At a lower TSR, the turbine blades will undergo large angles of attack which results in greater flow separation on their inner sides leading to large vorticity shedding [11]; the blades will enter dynamic stall on the upstream side of their path, resulting in the shedding of two counter-rotating vortices, from the leading and trailing edges. These vortices are convected downstream by the mean flow, through the rotor's swept area and across the path of the blade, where the blade will interact with them, resulting in an increase in lift [6]. At a higher TSR, the larger relative velocity of the blades reduces the flow separation, and hence the role of the dynamic stall vortices on the turbine's hydrodynamics [4].The kinematics of a turbine governs the extraction of energy from the mean flow, resulting in a velocity deficit behind the rotor, with a greater velocity deficit observed when it is operating at hig...

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Large-eddy simulation of shallow turbulent wakes behind a conical island

Cited by 27 publications

References 45 publications

Asymmetric wake of a horizontal cylinder in close proximity to a solid boundary for Reynolds numbers in the subcritical turbulence regime

Asymmetric wake of a horizontal cylinder in close proximity to a solid boundary for Reynolds numbers in the subcritical turbulence regime

Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

An Actuator Surface Model to Simulate Vertical Axis Turbines

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