On rotational flows with discontinuous vorticity beneath steady water waves near stagnation

Chen, Lin; Basu, Biswajit; Martin, Calin Iulian

doi:10.1017/jfm.2020.1057

Cited by 10 publications

(4 citation statements)

References 74 publications

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“…Te hydrodynamic environment was simulated using ABAQUS/Aqua, which has been commonly used in previous studies [36][37][38]. However, the real hydrodynamic environment may be more complex [39], and more research is needed to consider this.…”

Section: Numerical Validationmentioning

confidence: 99%

Simultaneous Estimation of Submerged Floating Tunnel Displacement and Mooring Cable Tension through FIR Filter-Based Strain and Acceleration Fusion

Choi

Jang

et al. 2023

Structural Control and Health Monitoring

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A submerged floating tunnel (SFT) is a tunnel structure that floats approximately 50 m below the water surface and is anchored to the seabed by mooring cables. It is a new alternative to conventional bridges and immersed tunnels. There have been ongoing efforts to construct SFTs worldwide, and the integrity of these SFTs needs to be monitored throughout their lifespan. This study simultaneously estimated the tunnel displacement and mooring cable tension force using acceleration and strain measurements to assess the integrity of an SFT. First, strain measurements were transformed to displacement using simplified mode shapes and mode-scaling factors, which did not require the true mode shapes of the SFT. The mode-scaling factors were automatically estimated using initial strain and acceleration measurements. Then, the strain-based displacement was combined with the acceleration measurement using a finite impulse response filter to improve the displacement estimation accuracy. In addition, the tension force of a mooring cable was estimated from the displacement at the connection between the tunnel and mooring cable. The feasibility of the proposed technique was examined through a series of numerical simulations and laboratory tests on an 8 m-long aluminum SFT mock-up structure.

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Section: Numerical Validationmentioning

confidence: 99%

Simultaneous Estimation of Submerged Floating Tunnel Displacement and Mooring Cable Tension through FIR Filter-Based Strain and Acceleration Fusion

Choi

Jang

et al. 2023

Structural Control and Health Monitoring

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“…It is noted that linear wave theories are adopted in the present study without considering the vortices of fluids 35 and nonlinear wave effects. 36,37 In addition, current induced loading which may cause significant loading effect on the monopile 38 is not considered. These nonlinear wave effects and current induced loading will be included in the authors' future research.…”

Section: Hydrodynamic Loadingmentioning

confidence: 99%

“…where ω s ¼ f opt ω n , and ω n is the OWT fundamental natural frequency of the tower, and f opt is the optimal frequency ratio determined using Equation (37). The initial optimum damping ratio ζ opt of the pendulum is determined using Equation (37).…”

Section: Real-time Tuning Of the 3d-aptmdmentioning

confidence: 99%

Adaptive bidirectional dynamic response control of offshore wind turbines with time‐varying structural properties

Sun

Jahangiri

Sun

2021

Structural Contr & Hlth

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Wind, wave and seismic loading induced excessive vibration of offshore wind turbines (OWTs) impairs the wind turbine energy output and escalates its fatigue damage. The present study proposes a three-dimensional adaptive pendulum tuned mass damper (3D-APTMD) to control the bidirectional dynamic responses of monopile OWTs exposed to combined wind, wave, seismic loading, and time-varying structural properties. In terms of the proposed adaptive tuning algorithm, the natural frequency and damping property of the 3D-APTMD are tuned in real time to match the wind turbine time-varying dominant frequency caused by environmental and/or structural property variations. Performance of the developed adaptive damper is examined on a monopile 5-MW (megawatt) baseline wind turbine subjected to representative wind, wave, and seismic loading. Time-varying stiffness of the tower and foundation is introduced to simulate damage evolution during service life. A threedimensional pendulum tuned mass damper (3D-PTMD) and dual linear TMDs (2TMD) are used for comparison. Research results show that when damage occurs, 3D-PTMD and 2TMD become partially off-tuned and less effective. In comparison, the 3D-APTMD which is tuned in real time maintains its effectiveness. It can improve the reduction effect by around 25% and 30% when compared with the 3D-PTMD and 2TMD, respectively. Therefore, the proposed 3D-APTMD is promising for real application to protect OWTs, high-rise buildings, chimneys, and other types of slender structures suffering from excessive bidirectional vibration, and environmental, operational, and/or structural property variations. K E Y W O R D Sbidirectional dynamic response control, offshore wind turbines, three-dimensional adaptive pendulum tuned mass damper, time-varying structural property, wind, wave, and seismic loading | INTRODUCTIONTo protect the deteriorating environment, wind energy production and consumption have been growing exponentially since 2000. In the passed decade, numerous offshore wind farms have been constructed in Europe, China, and the United States. Nowadays, offshore wind farms are becoming increasingly popular due to the advantages including

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“…They also constructed waves for flows with vorticity that varies linearly and quadratically with respect the stream function. More recently, Chen et al [4] presented an complete description of the flow beneath periodic water waves propagating on rotational flows with piece-wise constant vorticity. They took into account the effects of the vorticity on the free surface, on the streamlines, on the pressure distribution in the fluid and also showed particle trajectories.…”

Section: Introductionmentioning

confidence: 99%

Solitary waves on flows with an exponentially sheared current and stagnation points

Flamarion¹,

Ribeiro-Jr²

2022

Preprint

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While several articles have been written on water waves on flows with constant vorticity, little is known about the extent to which a nonconstant vorticity affects the flow structure, such as the appearance of stagnation points. In order to shed light on this topic, we investigate in detail the flow beneath solitary waves propagating on an exponentially decaying sheared current. Our focus is to analyse numerically the emergence of stagnation points. For this purpose, we approximate the velocity field within the fluid bulk through the classical Korteweg-de Vries asymptotic expansion and use the Matlab language to evaluate the resulting streamfunction. Our findings suggest that the flow beneath the waves can have zero, one or two stagnation points in the fluid body. We also study the bifurcation between these flows. Our simulations indicate that the stagnation points emerge from a streamline with a sharp corner.

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On rotational flows with discontinuous vorticity beneath steady water waves near stagnation

Abstract: Abstract

Cited by 10 publications

References 74 publications

Simultaneous Estimation of Submerged Floating Tunnel Displacement and Mooring Cable Tension through FIR Filter-Based Strain and Acceleration Fusion

Simultaneous Estimation of Submerged Floating Tunnel Displacement and Mooring Cable Tension through FIR Filter-Based Strain and Acceleration Fusion

Adaptive bidirectional dynamic response control of offshore wind turbines with time‐varying structural properties

Solitary waves on flows with an exponentially sheared current and stagnation points

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