Simulations for Design and Reconstruction of Breaking Waves in a Wavetank

2015 ◽  
Author(s):  
R. Kurnia ◽  
T. van den Munckhof ◽  
C. P. Poot ◽  
P. Naaijen ◽  
R. H. M. Huijsmans ◽  
...  
Keyword(s):  
Eddy Viscosity ◽  
Flexible Structures ◽  
Breaking Waves ◽  
Boussinesq Model ◽  
Simulation Code ◽  
Efficient Simulation ◽  
Oil Platforms ◽  
Numerical Design ◽  
Breaking Mechanism ◽  
Wave Maker

To determine forces on fixed and flexible structures such as wind mills and oil platforms, experiments in wave tanks are useful to investigate the impacts in various types of environmental waves. In this paper we show that the use of an efficient simulation code can optimize the experiments by designing the influx such that waves will break at a predefined position of the structure. The consecutive actual measurements agree well with the numerical design of the experiments. Using the measured elevation close by the wave maker as input, the software recovers the experimental data in great detail, even for rather short (up to L/D=1) and very steep breaking waves with steepness parameter (ak) till 0.4. The experiments were carried out in the TUD-wavetank and the simulation is done by HaWaSSI-AB, a spatial-spectral implementation of a Hamiltonian Boussinesq model with an eddy-viscosity breaking mechanism that is initiated by a kinematic breaking condition.

scholarly journals Suppression of Wind Ripples and Microwave Backscattering Due to Turbulence Generated by Breaking Surface Waves

2020 ◽  
Vol 12 (21) ◽  
pp. 3618
Author(s):  
Stanislav Ermakov ◽  
Vladimir Dobrokhotov ◽  
Irina Sergievskaya ◽  
Ivan Kapustin
Keyword(s):  
Remote Sensing ◽  
Surface Waves ◽  
Wave Breaking ◽  
Wave Train ◽  
Wind Waves ◽  
Breaking Waves ◽  
Doppler Spectrum ◽  
Strong Wave ◽  
Wave Maker ◽  
Radar Backscattering

The role of wave breaking in microwave backscattering from the sea surface is a problem of great importance for the development of theories and methods on ocean remote sensing, in particular for oil spill remote sensing. Recently it has been shown that microwave radar return is determined by both Bragg and non-Bragg (non-polarized) scattering mechanisms and some evidence has been given that the latter is associated with wave breaking, in particular, with strong breaking such as spilling or plunging. However, our understanding of mechanisms of the action of strong wave breaking on small-scale wind waves (ripples) and thus on the radar return is still insufficient. In this paper an effect of suppression of radar backscattering after strong wave breaking has been revealed experimentally and has been attributed to the wind ripple suppression due to turbulence generated by strong wave breaking. The experiments were carried out in a wind wave tank where a frequency modulated wave train of intense meter-decimeter-scale surface waves was generated by a mechanical wave maker. The wave train was compressed according to the gravity wave dispersion relation (“dispersive focusing”) into a short-wave packet at a given distance from the wave maker. Strong wave breaking with wave crest overturning (spilling) occurred for one or two highest waves in the packet. Short decimeter-centimeter-scale wind waves were generated at gentle winds, simultaneously with the long breaking waves. A Ka-band scatterometer was used to study microwave backscattering from the surface waves in the tank. The scatterometer looking at the area of wave breaking was mounted over the tank at a height of about 1 m above the mean water level, the incidence angle of the microwave radiation was about 50 degrees. It has been obtained that the radar return in the presence of short wind waves is characterized by the radar Doppler spectrum with a peak roughly centered in the vicinity of Bragg wave frequencies. The radar return was strongly enhanced in a wide frequency range of the radar Doppler spectrum when a packet of long breaking waves arrived at the area irradiated by the radar. After the passage of breaking waves, the radar return strongly dropped and then slowly recovered to the initial level. Measurements of velocities in the upper water layer have confirmed that the attenuation of radar backscattering after wave breaking is due to suppression of short wind waves by turbulence generated in the breaking zone. A physical analysis of the effect has been presented.

Computational and Experimental Simulation of Nonbreaking and Breaking Waves for the Investigation of Structural Loads and Motions

2006 ◽  
Author(s):  
Gu¨nther F. Clauss ◽  
Robert Stu¨ck ◽  
Florian Stempinski ◽  
Christian E. Schmittner
Keyword(s):  
Data Transfer ◽  
Stokes Equations ◽  
Wave Structure ◽  
Breaking Waves ◽  
Experimental Simulation ◽  
Navier Stokes ◽  
Wave Crest ◽  
Breaking Wave ◽  
Simulation Code ◽  
Wave Trains

For the analysis of loads and motions of marine structures in harsh seaways precise information about the hydrodynamics of waves is required. While the surface motion of waves can easily be measured in physical wave tanks other critical characteristics such as the instantaneous particle velocity and acceleration as well as the pressure field, especially under the wave crest are difficult and time-consuming to obtain. Therefore a new method is presented to approximate the wave potential of a given instantaneous wave contour. Numerical methods — so called numerical wave tanks (NWTs) — are developed to provide the desired insight into wave hydrodynamics. A potential theory method based on the Finite Element method (Pot/FE), a RANSE (Reynolds-Averaged Navier-Stokes Equations) method applying VOF (Volume of Fluid) and a combination of both is utilized for the simulation of different model wave trains. The coupling of both CFD (computational fluid dynamics) solvers is a useful approach to benefit from the advantages of the two different methods: The Pot/FE solver WAVETUB (wave simulation code developed at Technical University Berlin) allows a very fast and accurate simulation of the propagation of nonbreaking waves while the RANSE/VOF solver has the capability of simulating breaking waves. Two different breaking criteria for the detection of wave breaking are implemented in WAVETUB for triggering the automated coupling process by data transfer at the interface. It is shown that an efficient method for the simulation of breaking wave trains including wave-structure interaction in 2D and 3D is established by the coupling of both CFD codes. All results are discussed in detail.

scholarly journals TIME DOMAIN COMPARISONS OF MEASURED AND SPECTRALLY SIMULATED BREAKING WAVES

2017 ◽  
pp. 12
Author(s):  
Mustafa Kemal Ozalp ◽  
Serdar Beji
Keyword(s):  
Time Domain ◽  
Surf Zone ◽  
Field Measurements ◽  
Wave Model ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Dissipative Effects ◽  
Spectral Components ◽  
Breaking Mechanism ◽  
Acceptable Agreement

For realistic wave simulations in the nearshore zone besides nonlinear interactions, the dissipative effects of wave breaking must also be taken into account. This paper presents the applications of a spectral nonlinear wave model with a dissipative breaking mechanism introduced by Beji and Nadaoka (1997). Results obtained for spectral components are converted to the time series and compared with Beji and Battjes' (1993) laboratory measurements and the field measurements of Nakamura and Katoh (1992) in the surf zone. While the model predicts the spilling-type breaking of irregular waves in acceptable agreement with the measurements in time domain, the agreement is unsatisfactory for plunging-type breakers.

scholarly journals NEW METHODS FOR STABILIZING RANS TURBULENCE MODELS WITH APPLICATION TO LARGE SCALE BREAKING WAVES

2020 ◽  
pp. 19
Author(s):  
Georgios Azorakos ◽  
Bjarke Eltard Larsen ◽  
David R. Fuhrman
Keyword(s):  
Turbulence Model ◽  
Large Scale ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Breaking Waves ◽  
Wide Spread ◽  
Cfd Simulations ◽  
New Methods ◽  
Rans Turbulence Models ◽  
Scale Breaking

Recently, Larsen and Fuhrman (2018) have shown that seemingly all commonly used (both k-omega and k-epsilon variants) two-equation RANS turbulence closure models are unconditionally unstable in the potential flow beneath surface waves, helping to explain the wide-spread over-production of turbulent kinetic energy in CFD simulations, relative to measurements. They devised and tested a new formally stabilized formulation of the widely used k-omega turbulence model, making use of a modified eddy viscosity. In the present work, three new formally-stable k-omega turbulence model formulations are derived and tested in CFD simulations involving the flow and dynamics beneath large-scale plunging breaking waves.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/T2fFRgq3I8E

Application of a Boussinesq model for the computation of breaking waves

1999 ◽  
Vol 26 (10) ◽  
pp. 927-947 ◽  
Author(s):  
C. Skotner ◽  
C.J. Apelt
Keyword(s):  
Breaking Waves ◽  
Boussinesq Model

Application of a Boussinesq model for the computation of breaking waves

1999 ◽  
Vol 26 (10) ◽  
pp. 905-925 ◽  
Author(s):  
C. Skotner ◽  
C.J. Apelt
Keyword(s):  
Breaking Waves ◽  
Boussinesq Model

scholarly journals MEASUREMENT AND MODELING OF SOLITARY WAVE INDUCED BED SHEAR STRESS OVER A ROUGH BED

2012 ◽  
Vol 1 (33) ◽  
pp. 21 ◽  
Author(s):  
Jaya Kumar Seelam ◽  
Tom E Baldock
Keyword(s):  
Shear Stress ◽  
Eddy Viscosity ◽  
Breaking Waves ◽  
Shear Stresses ◽  
Bed Shear Stress ◽  
Eddy Viscosity Model ◽  
Friction Factors ◽  
Convolution Model ◽  
Rough Bed ◽  
Bed Shear Stresses

Bed shear stresses generated by solitary waves were measured using a shear cell apparatus over a rough bed in laminar and transitional flow regimes (~7600 < Re < ~60200). Modeling of bed shear stress was carried out using analytical models employing convolution integration methods forced with the free stream velocity and three eddy viscosity models. The measured wave height to water depth (h/d) ratio varied between 0.13 and 0.65; maximum near- bed velocity varied between 0.16 and 0.47 m/s and the maximum total shear stress (sum of form drag and bed shear) varied between 0.565 and 3.29 Pa. Wave friction factors estimated from the bed shear stresses at the maximum bed shear stress using both maximum and instantaneous velocities showed that there is an increase in friction factors estimated using instantaneous velocities, for non-breaking waves. Maximum positive total stress was approximately 2.2 times larger than maximum negative total stress for non-breaking waves. Modeled and measured positive total stresses are well correlated using the convolution model with an eddy viscosity model analogous to steady flow conditions (nu_t=0.45u* z1; where nu_t is eddy viscosity, u* is shear velocity and z1 is the elevation parameter related to relative roughness). The bed shear stress leads the free stream fluid velocity by approximately 30° for non-breaking waves and by 48° for breaking waves, which is under-predicted by 27% by the convolution model with above mentioned eddy viscosity model.

scholarly journals SERRE GREEN-NAGHDI MODELLING OF WAVE TRANSFORMATION BREAKING AND RUN-UP USING A HIGH-ORDER FINITE-VOLUME FINITE-DIFFERENCE SCHEME

2011 ◽  
Vol 1 (32) ◽  
pp. 13 ◽  
Author(s):  
Marion Tissier ◽  
Philippe Bonneton ◽  
Fabien Marche ◽  
Florent Chazel ◽  
David Lannes
Keyword(s):  
Energy Dissipation ◽  
Finite Difference ◽  
Finite Volume ◽  
Wave Breaking ◽  
Ad Hoc ◽  
Laboratory Data ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Finite Volume Schemes ◽  
Boussinesq Model

In this paper, a fully nonlinear Boussinesq model is presented and applied to the description of breaking waves and shoreline motions. It is based on Serre Green-Naghdi equations, solved using a time-splitting approach separating hyperbolic and dispersive parts of the equations. The hyperbolic part of the equations is solved using Finite-Volume schemes, whereas dispersive terms are solved using a Finite-Difference method. The idea is to switch locally in space and time to NSWE by skipping the dispersive step when the wave is ready to break, so as the energy dissipation due to wave breaking is predicted by the shock theory. This approach allows wave breaking to be handled naturally, without any ad-hoc parameterization for the energy dissipation. Extensive validations of the method are presented using laboratory data.

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