scholarly journals APPLICATION OF OPEN BOUNDARIES WITHIN A TWO-WAY COUPLED SPH MODEL TO SIMULATE NON-LINEAR WAVE-STRUCTURE INTERACTIONS

2018 ◽  
pp. 14 ◽  
Author(s):  
Tim Verbrugghe ◽  
José Manuel Dominguez ◽  
Corrado Altomare ◽  
Angelantonio Tafuni ◽  
Peter Troch ◽  
...  
Keyword(s):  
Coupled Model ◽  
Wave Structure ◽  
Surface Elevation ◽  
Open Boundary ◽  
Test Case ◽  
Linear Wave ◽  
Linear Potential ◽  
Original Solution ◽  
Non Linear ◽  
Sph Model

A two-way coupling between the fully non-linear potential flow (FNPF) solver OceanWave3D and the Smoothed Particle Hydrodynamics (SPH) solver DualSPHysics is presented. At the coupling interfaces within the SPH domain, an open boundary formulation is applied. An inlet and outlet zone are filled with bu er particles. At the inlet, horizontal orbital velocities and surface elevations calculated with OceanWave3D are imposed on the bu er particles. At the outlet, horizontal orbital velocities are imposed, but the surface elevation is extrapolated from the fluid domain. Velocity corrections are applied to avoid unwanted reflections in the fluid domain. The SPH surface elevation can be coupled back to OceanWave3D, where the original solution is overwritten. The coupling methodology is validated using a 2-D test case of a floating box. Additionally, a 3-D proof of concept is shown where overtopping waves are acting on a heaving cylinder. The 2-way coupled model proofs to be capable of simulating wave propagation and wave-structure interaction problems with an acceptable accuracy with RMSE values remaining below the smoothing length h.

scholarly journals Implementation of Open Boundaries within a Two-Way Coupled SPH Model to Simulate Nonlinear Wave–Structure Interactions

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 697 ◽  
Author(s):  
Tim Verbrugghe ◽  
Vasiliki Stratigaki ◽  
Corrado Altomare ◽  
J. Domínguez ◽  
Peter Troch ◽  
...  
Keyword(s):  
Coupled Model ◽  
Wave Structure ◽  
Surface Elevation ◽  
Open Boundary ◽  
Test Case ◽  
Coupled Models ◽  
Flow Solver ◽  
Particle Hydrodynamics ◽  
Nonlinear Potential ◽  
Sph Model

A two-way coupling between the Smoothed Particle Hydrodynamics (SPH) solver DualSPHysics and the Fully Nonlinear Potential Flow solver OceanWave3D is presented. At the coupling interfaces within the SPH numerical domain, an open boundary formulation is applied. An inlet and outlet zone are filled with buffer particles. At the inlet, horizontal orbital velocities and surface elevations calculated using OceanWave3D are imposed on the buffer particles. At the outlet, horizontal orbital velocities are imposed, but the surface elevation is extrapolated from the fluid domain. Velocity corrections are applied to avoid unwanted reflections in the SPH fluid domain. The SPH surface elevation is coupled back to OceanWave3D, where the originally calculated free surface is overwritten. The coupling methodology is validated using a 2D test case of a floating box. Additionally, a 3D proof of concept is shown where overtopping waves are acting on a heaving cylinder. The two-way coupled model (exchange of information in two directions between the coupled models) has proven to be capable of simulating wave propagation and wave–structure interaction problems with an acceptable accuracy with error values remaining below the smoothing length h S P H .

scholarly journals Relation between orbital velocities, pressure and surface elevation in non-linear nearshore water waves

2021 ◽  
Author(s):  
Kévin Martins ◽  
Philippe Bonneton ◽  
David Lannes ◽  
Hervé Michallet
Keyword(s):  
Free Surface ◽  
Surface Energy ◽  
Water Waves ◽  
Energy Levels ◽  
Sea Surface ◽  
Surface Elevation ◽  
Linear Wave ◽  
Free Surface Elevation ◽  
High Frequencies ◽  
Non Linear

AbstractThe inability of the linear wave dispersion relation to characterize the dispersive properties of non-linear shoaling and breaking waves in the nearshore has long been recognised. Yet, it remains widely used with linear wave theory to convert between sub-surface pressure, wave orbital velocities and the free surface elevation associated with non-linear nearshore waves. Here, we present a non-linear fully dispersive method for reconstructing the free surface elevation from sub-surface hydrodynamic measurements. This reconstruction requires knowledge of the dispersive properties of the wave field through the dominant wavenumbers magnitude κ, representative in an energy-averaged sense of a mixed sea-state composed of both free and forced components. The present approach is effective starting from intermediate water depths - where non-linear interactions between triads intensify - up to the surf zone, where most wave components are forced and travel approximately at the speed of non-dispersive shallow-water waves. In laboratory conditions, where measurements of κ are available, the non-linear fully dispersive method successfully reconstructs sea-surface energy levels at high frequencies in diverse non-linear and dispersive conditions. In the field, we investigate the potential of a reconstruction that uses a Boussinesq approximation of κ, since such measurements are generally lacking. Overall, the proposed approach offers great potential for collecting more accurate measurements under storm conditions, both in terms of sea-surface energy levels at high frequencies and wave-by-wave statistics (e.g. wave extrema). Through its control on the efficiency of non-linear energy transfers between triads, the spectral bandwidth is shown to greatly influence non-linear effects in the transfer functions between sub-surface hydrodynamics and the sea-surface elevation.

Non-Linear Calculation of Tailored Wave Trains for Experimental Investigation of Extreme Structure Behaviour

2004 ◽  
Author(s):  
Gu¨nther F. Clauss ◽  
Janou Hennig ◽  
Christian E. Schmittner ◽  
Walter L. Ku¨hnlein
Keyword(s):  
Experimental Investigation ◽  
Wave Propagation ◽  
Wave Structure ◽  
Linear Wave ◽  
Advantages And Disadvantages ◽  
Non Linear ◽  
Linear Wave Propagation ◽  
Precise Prediction ◽  
Wave Trains ◽  
Wave Models

The experimental investigation of extreme wave/structure interaction scenarios puts high demands on wave generation and calculation. This paper presents different approaches for modelling non-linear wave propagation. Results of numerical simulations from two different numerical wave tanks are compared to models tests. A further approach uses analytical wave models which are combined with empirical terms to allow a fast and precise prediction of non-linear wave propagation for day-to-day use. All approaches can be used either separately or in combination — depending on their particular purpose. As an application, different special wave scenarios — both academic and realistic — are generated and validated by measurements. The advantages and disadvantages of the presented methods are discussed in detail with regard to their appropriate use for investigations of extreme structure behaviour.

Non-Linear Wave Diffraction Around a Moored Ship

2004 ◽  
Author(s):  
J. Zang ◽  
R. Gibson ◽  
P. H. Taylor ◽  
R. Eatock Taylor ◽  
C. Swan
Keyword(s):  
Wave Diffraction ◽  
Scattering Problem ◽  
Wave Interaction ◽  
Wave Structure ◽  
Second Order ◽  
Linear Wave ◽  
Wave Impact ◽  
Non Linear ◽  
Focused Wave ◽  
Run Up

The objective of this research, part of the FP5 REBASDO Programme, is to examine the effects of directional wave spreading on the nonlinear hydrodynamic loads and the wave run-up around the bow of a floating vessel (FPSO) in random seas. In this work, the non-linear wave scattering problem is solved by employing a quadratic boundary element method. An existing scheme (DIFFRACT developed in Oxford) has been extended to deal with uni-directional and directional bi-chromatic input wave systems, calculating second-order wave diffraction under regular waves and focused wave groups. The second order wave interaction with a floating vessel in a unidirectional focused wave group is presented in this paper. Comparison of numerical results and the experimental measurements conducted at Imperial College shows excellent agreement. The second-order free surface components at the bow of the ship are very significant, and cannot be neglected if one requires accurate prediction of the wave-structure interaction; otherwise a major underestimation of the wave impact on the structure could occur.

Non-linear wave-induced motions of cylindrical-shaped floaters of fish farms

2009 ◽  
Vol 223 (3) ◽  
pp. 361-375 ◽  
Author(s):  
D Kristiansen ◽  
O M Faltinsen
Keyword(s):  
Model Tests ◽  
Linear Wave ◽  
Linear Potential ◽  
Fish Farms ◽  
Non Linear ◽  
Computational Fluid Dynamics Cfd ◽  
Harmonic Components ◽  
Wave Induced ◽  
Hydrodynamic Effects ◽  
Sway Motion

This paper addresses the two-dimensional hydrodynamical problem of a floating circular cylinder in waves by means of model tests and numerical simulations. The problem is relevant for floaters of fish farms. Dedicated model tests and computational fluid dynamics (CFD)-simulations, using a presently developed numerical wave tank are presented. Large amplitude sway motion of the cylinder at a wave frequency equal to half the natural sway frequency was observed, both experimentally and numerically. This is argued to be associated with non-linear hydrodynamic effects and instabilities. Further, linear potential flow theory is shown to overpredict the sway motion at resonance of about 500 per cent compared with experiments and simulations. This discrepancy is explained to be mainly attributable to viscous damping caused by flow separation. Higher-order harmonic components of the hydrodynamic forces are significant and should be considered in fatigue life analyses of fish farms.

Numerical analysis of wave–structure interaction of regular waves with surface-piercing inclined plates

2021 ◽  
Author(s):  
C. P. Cummins ◽  
G. T. Scarlett ◽  
C. Windt
Keyword(s):  
Excellent Agreement ◽  
Stokes Equations ◽  
Scattering Problem ◽  
Low Frequency ◽  
Wave Structure ◽  
Finite Depth ◽  
Linear Potential ◽  
Low Frequencies ◽  
Resonant Wave ◽  
Non Linear

AbstractThe Mocean wave energy converter consists of two sections, hinged at a central location, allowing the device to convert energy from the relative pitching motion of the sections. In a simplified form, the scattering problem for the device can be modelled as monochromatic waves incident upon a thin, inclined, surface-piercing plate of length $$L'$$ L ′ in a finite depth $$d'$$ d ′ of water. In this paper, the flow past such a plate is solved using a Boundary Element Method (BEM) and Computational Fluid Dynamics (CFD). While the BEM solution is based on linear potential flow theory, CFD directly solves the Navier–Stokes equations. Problems of this type are known to exhibit near-perfect reflection (indicated by a reflection coefficient $$|R|\approx 1$$ | R | ≈ 1 ) of waves at specific wavenumbers $$k'$$ k ′ . In this paper, we show that the resonant motion of the fluid induces large hydrodynamic forces on the plate. Furthermore, we argue that this low-frequency resonance resembles Helmholtz resonance, and that Mocean’s device being able to tune to these low frequencies does not act like an attenuator. For the case where the water is deep ($$d'>\lambda '/2$$ d ′ > λ ′ / 2 , where $$\lambda '=2\pi /k'$$ λ ′ = 2 π / k ′ ), we find excellent agreement between our simulations and previous semi-analytical studies on the value of the resonant wave periods in deep water. We also find excellent agreement between the excitation forces on the plate computed using the BEM model, analytical results, and CFD for large inclination angles ($$\alpha > 45^\circ $$ α > 45 ∘ ). For $$\alpha \le 15^\circ $$ α ≤ 15 ∘ , both methods show the same trend, but the CFD predicts a significantly smaller peak in the excitation force compared with BEM, which we attribute to non-linear effects such as the non-linear Froude–Krylov force

Control Signal Optimization for Non-Linear Wave Generation

2018 ◽  
Author(s):  
J. B. H. Hicks ◽  
H. B. Bingham ◽  
R. Read
Keyword(s):  
Water Waves ◽  
Numerical Optimization ◽  
Wave Generation ◽  
Linear Wave ◽  
Linear Potential ◽  
Numerical Work ◽  
Flow Solver ◽  
Control Signals ◽  
Correction Scheme ◽  
Non Linear

This paper investigates the use of optimization for numerical-physical wave generation in wave tanks. Control signals for a wedge-shaped plunger-type wave generator are developed to produce stable non-linear, deep-water waves in both numerical and physical wave tanks. A fully non-linear potential flow solver developed at DTU is used for the numerical work. Numerical optimization proceeds by a defect correction scheme, resulting in optimized control signals for wavelengths of 0.7–2 m (corresponding to non-dimensional wave numbers kh = 2–5.5) and steepnesses of 3–11%.

Coupling methodology for smoothed particle hydrodynamics modelling of non-linear wave-structure interactions

2018 ◽  
Vol 138 ◽  
pp. 184-198 ◽  
Author(s):  
Tim Verbrugghe ◽  
José Manuel Domínguez ◽  
Alejandro J.C. Crespo ◽  
Corrado Altomare ◽  
Vicky Stratigaki ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Wave Structure ◽  
Linear Wave ◽  
Non Linear ◽  
Particle Hydrodynamics ◽  
Smoothed Particle
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