Academic literature on the topic 'HOS-NWT'
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Journal articles on the topic "HOS-NWT"
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Kim, Shinwoong, Benjamin Bouscasse, Guillaume Ducrozet, Maxime Canard, Guillaume De Hauteclocque, Charaf Ouled Housseine, and Pierre Ferrant. "Numerical and experimental study of a FORM-based design wave applying the HOS-NWT nonlinear wave solver." Ocean Engineering 263 (November 2022): 112287. http://dx.doi.org/10.1016/j.oceaneng.2022.112287.
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Vyzikas, Thomas, Dimitris Stagonas, Christophe Maisondieu, and Deborah Greaves. "Intercomparison of Three Open-Source Numerical Flumes for the Surface Dynamics of Steep Focused Wave Groups." Fluids 6, no. 1 (December 30, 2020): 9. http://dx.doi.org/10.3390/fluids6010009.
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NewWave-type focused wave groups are commonly used to simulate the design wave for a given sea state. These extreme wave events are challenging to reproduce numerically by the various Numerical Wave Tanks (NWTs), due to the high steepness of the wave group and the occurring wave-wave interactions. For such complex problems, the validation of NWTs against experimental results is vital for confirming the applicability of the models. Intercomparisons among different solvers are also important for selecting the most appropriate model in terms of balancing between accuracy and computational cost. The present study compares three open-source NWTs in OpenFOAM, SWASH and HOS-NWT, with experimental results for limiting breaking focused wave groups. The comparison is performed by analysing the propagation of steep wave groups and their extracted harmonics after employing an accurate focusing methodology. The scope is to investigate the capabilities of the solvers for simulating extreme NewWave-type groups, which can be used as the “design wave” for ocean and coastal engineering applications. The results demonstrate the very good performance of the numerical models and provide valuable insights to the design of the NWTs, while highlighting potential limitations in the reproduction of specific harmonics of the wave group.
Dissertations / Theses on the topic "HOS-NWT"
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Kim, Shinwoong. "Experimental study on wave bending moments of a zero-speed rigid containership model in regular, irregular, and equivalent design waves." Electronic Thesis or Diss., Ecole centrale de Nantes, 2023. http://www.theses.fr/2023ECDN0001.
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La thèse vise à étudier les mouvements et les chargements internes d’un modèle de porte-conteneur rigide formé de 9 segments dans des vagues extrêmes. L’étude est principalement expérimentale et est réalisée avec une maquette sans vitesse d’avance dans une houle de face et une houle oblique (-120 degrés). L’étude aboutit à des résultats soulignant l’importance de la prendre en compte les aspects non linéaires des vagues et des réponses structurelles correspondantes.Dans des conditions de mer de face, trois types de vagues sont testés. Des vagues régulières sont utilisées pour s’assurer que le modèle se comporte de manière similaire à la campagne précédente effectuée avec la même maquette. Une approche de type Monte Carlo avec un certain nombre de réalisations de 2 heures 30 de vagues irrégulières est ensuite utilisée pour construire des données de référence. Enfin, des vagues equivalentes de design (EDW) sont générées pour vérifier, en particulier, la faisabilité d’une approche EDW irrégulière appelée First Order Reliability Method (FORM). Un algorithme numérique FORM couplé avec le solveur HOSNWT est développé et validé par rapport aux résultats Monte Carlo. Les caractéristiques géométriques des signaux EDW et VBM ainsi que leurs statistiques sont étudiées. L’étude vise peut-être deux quantités. Le premier est la hauteur de crête de la vague dans un scénario de vague seule, et le second est le VBM du modèle segmenté. L’utilisation du solveur de génération d’onde non linéaire HOS-NWT, permet une validation croisée avec la mesure expérimentale car les vagues générées sont comparables. Dans la condition de vagues obliques, l’étude est limitée aux vagues régulières avec différentes cambrure de vagues afin de fournir des données de référence pour les futures études. L’effet de non-linéarité des vagues sur les moments de flexion horizontaux et verticaux des vagues avec une cambrure variable est démontréThe present thesis aims to study the motions and the internal loads of a 9-segmented rigid containership model in extreme waves. The study is mainly experimental and is carried out on a zero-speed model in a 180-degree head sea and a -120 degree oblique sea. The study leads to results highlighting the importance of the consideration of nonlinear wave descriptions and corresponding nonlinear structural responses.In head sea conditions, three wave approaches are considered. Regular waves are used to ensure that the model behaves similar to the earlier campaign. A Monte Carlo approach with a number of full scale 2h30 irregular wave realizations is used to have reference data. Finally, irregular equivalent design waves (EDW) are studied to check, in particular, the feasibility of one irregular EDW approach called First Order Reliability Method.A numerical algorithm coupling with the HOS-NWT for the FORM EDW is developed and the validation compared to the Monte Carlo results is performed in terms of geometrical characteristics of the EDW and IW signals along with their statistics. The study targets mainly two quantities. The first is the wave crest in a wave-only scenario, and the second is the VBM of the segmented model. The use of the HOSNWT, a nonlinear wave generation solver, enables cross-validation with experimental measurement.In the oblique wave condition, the study is limited to regular waves with various wave steepness with the intent to provide reference data for future benchmark studies. The wave nonlinearity effect on the horizontal and vertical wave bending moments with varying steepness is shown
Conference papers on the topic "HOS-NWT"
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Seiffert, Betsy R., and Guillaume Ducrozet. "A Comparative Study of Wave Breaking Models in a High-Order Spectral Model." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61664.
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We examine the implementation of two different wave breaking models into the nonlinear potential flow solver HOS-NWT. HOS-NWT is a computationally efficient, open source code that solves for surface elevation in a numerical wave tank using the High-Order Spectral (HOS) method [1]. The first model is a combination of a kinematic wave breaking onset criteria proposed by Barthelemey, et al. [2] and validated by Saket, et al. [3], and an energy dissipation mechanism proposed by Tian, et al. [4, 5]. The wave breaking onset parameter is based on the ratio of local energy flux velocity to the local crest velocity. Once breaking is initiated, an eddy viscosity parameter is estimated based on the pre-breaking local wave geometry, as described in [4, 5]. This eddy viscosity is then added as a diffusion term to the kinematic and dynamic free surface boundary conditions for the duration of wave breaking. Results implementing this wave breaking mechanism in HOS-NWT have shown that the model can successfully calculate the surface elevation and corresponding frequency spectra, as well as the energy dissipation associated with breaking waves [6–8]. The second model implemented to account for wave breaking in HOS-NWT is based on the method proposed by Chalikov, et al. [9–11]. This model defines wave breaking onset by the curvature of the water surface and defines the wave as broken if it exceeds a certain value. A diffusion term is added to the kinematic and dynamic free surface boundary conditions which dissipates energy based on the local curvature of the water surface, which is consequently not constant in space nor time. Calculations made using the two models are compared with large scale experimental measurements conducted at the Hydrodynamics, Energetics and Atmospheric Environment Lab (LHEEA) at Ecole Centrale de Nantes. Comparison of calculations with measurements suggest that both models are successful at predicting wave breaking onset and energy dissipation. However, the model proposed by Barthelemy, et al. [2] and Tian, et al. [4] can be applied without knowing anything about the breaking waves a priori, whereas the model proposed by Chalikov [9] requires tuning to specific conditions.
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Ducrozet, Guillaume, Benjamin Bouscasse, Félicien Bonnefoy, and Vincent Leroy. "Methodology for the Integration of Experimental and Numerical Fluid Dynamics in the Study of a Floating Body Such As a Wind Turbine Subjected to Environmental Loads." In ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/omae2023-104676.
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Abstract The decrease in the computational cost of high-fidelity solvers like Computational Fluid dynamics (CFD) has expanded its use in the design of marine structures. This is true among academics and industrial R&D departments. After a long debate about whether CFD would or not supplant traditional experimental methods, it is widely accepted that the two approaches need to be considered together. The present paper proposes a framework for the integration of both experiments and high-fidelity numerical simulations in the design procedures of offshore wind turbines. It makes use of the nonlinear potential flow software HOS-NWT for wave generation, together with the NREL OpenFast software for wind generation and calculation of aerodynamic loads acting on the structure. For the numerical simulation, the environment (wave field) and aerodynamic loads are fed into the high-fidelity software with adequate couplings in the resolution algorithm. For the experiments, the wavemaker motion is run based on the HOS-NWT result, and the aerodynamic loads are imposed thanks to an actuator controlled by software in the loop system. Different scenarios are considered, from the classical CFD validation with experimental results up to more complex situations where the numerics and the experiments are done in sequence one before the other or vice versa, in order to complement or verify the findings.
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Choi, Youngmyung, Benjamin Bouscasse, Sopheak Seng, Guillaume Ducrozet, Lionel Gentaz, and Pierre Ferrant. "Generation of Regular and Irregular Waves in Navier-Stokes CFD Solvers by Matching With the Nonlinear Potential Wave Solution at the Boundaries." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-78077.
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The capability of wave generation and absorption in a viscous flow solver becomes important for achieving realistic simulations in naval and offshore fields. This study presents an efficient generation of nonlinear wave fields in the viscous flow solver by using a nonlinear potential solver called higher-order spectral method (HOS). The advantages of using a fully nonlinear potential solver for the generation of irregular waves are discussed. In particular, it is shown that the proposed method allows the CFD simulation to start at the time and over the space of interest, retrieved from the potential flow solution. The viscous flow solver is based on the open source library OpenFOAM. The potential solvers used to generate waves are the open source solvers HOS-Ocean and HOS-NWT (Numerical Wave Tank). Several simulation parameters in the CFD solver are investigated in the present study. A HOS wrapper program is newly developed to regenerate wave fields in the viscous flow solver. The wrapper program is validated with OpenFOAM for 2D and 3D regular and irregular waves using relaxation zones. Finally, the extreme waves corresponding to the 1000 year return period condition in the Gulf of Mexico are simulated with the viscous flow solver and the wave elevation is compared with the experiments.
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Canard, Maxime, Guillaume Ducrozet, and Benjamin Bouscasse. "Generation of 3-hr Long-Crested Waves of Extreme Sea States With HOS-NWT Solver." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18930.
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Abstract The accurate control of wave fields generated in experiments and numerical simulations is of great interest for the ocean engineering community. In the context of wave-structure interactions, the recommended practices of classification societies are indeed based on the definition of a wave spectrum, that needs to be reproduced. The present work intends to address this problem from the numerical point of view, using a Numerical Wave Tank equipped with a wavemaker and an absorbing beach, based on the High-Order Spectral method (HOS-NWT). The challenging case of the generation of 3-hours long-crested extreme sea states is studied in details. An iterative procedure to reproduce a target wave spectrum at a given distance from the wavemaker is proposed. The quality of the sea state obtained is evaluated using several criteria defined from spectral quantities. A validation is first performed with a highly nonlinear but non-breaking sea-state. Statistical crest distributions obtained are compared with the Forristall and Huang distributions [1,2]. Then, the Gulf of Mexico 1,000 Year Return Period wave condition is generated. This corresponds to an extreme sea state with significant wave breaking occurrence. The numerical solver needs to be able to account for this phenomenon [3]. The Tian breaking model [4, 5] is calibrated to realistically reproduce the dissipation due to breaking, with particular attention paid to the spatial discretization, enlightening its significant effect on breaking model actions. Consequences on the iterative correction process are studied. The computed statistical quantities appear to be significantly different changing the spatial discretization, while the wave energy spectrum stands the same. It questions the relevance of the characterization of a sea state with the sole wave energy spectrum.
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Canard, Maxime, Guillaume Ducrozet, and Benjamin Bouscasse. "Generation of Controlled Irregular Wave Crest Statistics in a Numerical Wavetank Using HOS-NWT Solver." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79880.
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Abstract In order to assess the reliability of offshore structures facing extreme environmental conditions, sea keeping tests are performed at model scale in experimental or numerical wave tanks. The scope of the present paper is limited to the generation of wave condition for such tests. The vast majority of industrial practices follow a stochastic approach. For each design sea state, several realizations of long irregular wave sequences are generated. The qualification of the waves mainly relies on the analysis of the mean spectrum and the ensemble crest height distribution at the structure (target) location (Xt). However, the wave propagation from the wavemaker to Xt is affected by nonlinear mechanisms and dissipation phenomena which lead to uncontrolled variations of the quantities of interest. To face those issues, the most advanced wave generation procedures usually focus on the quality of the wave spectrum at Xt, iterating on the wave maker motions. Nevertheless, depending on Xt, the crest height statistics can significantly differ. For instance with steep and narrow-banded unidirectional sea states, the distributions obtained at target locations far from the wave maker (Xt > 20λp, λp being the peak wavelength) enlighten a significant number of extreme events that are likely to strongly affect the response of the tested structure. On those grounds, the present study proposes a procedure that offers the possibility to reproduce those extreme statistics at locations closer to the wavemaker. The framework is limited to non breaking unidirectional waves. The procedure is numerically tested with the open-source nonlinear potential wave solver HOS-NWT. The study opens the way to an accurate control of the wave statistics at any location in a wave tank environment.
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Ducrozet, Guillaume, Fe´licien Bonnefoy, David Le Touze´, Pierre Roux de Reilhac, Chris Retzler, Jean-Marc Rousset, and Pierre Ferrant. "Experimental and Numerical Comparative Investigation of Pressure Fields Under Steep 2D Waves." In 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92616.
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In the present work is presented a recently developed fully-nonlinear spectral Numerical Wave Tank (NWT) model, named HOST-wm2, and its capabilities for reproducing highly-nonlinear evolutions in a wavetank are evidenced on experimental comparisons. This fully-spectral model is based on a Higher-Order Spectral (HOS) method, which ensures high levels of accuracy and efficiency, thanks to the fast resolution made by FFTs only. This numerical method is dedicated to model wave basins and a specific care is paid to fit the experimental wavetank characteristics (are included, the physical geometry of the wavetank, the snake-type wavemaker, an absorbing beach, ...). The numerical simulations are successfully compared to experiments conducted in cooperation with Ocean Power Delivery (OPD) in the wavetank of the Ecole Centrale de Nantes (ECN). Comparisons for wave elevation and pressure fields under highly-nonlinear steep 2D waves are reported. The usefulness of the presented NWT to assist experiments is also illustrated on the assessment of the procedure used to extract the pressure gradient from the experimental pressure signals.
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Aertsens, Tim, Guillaume Ducrozet, Alessandro Toffoli, and Jaak Monbaliu. "Two-Sided Wave Generation in a High-Order Spectral Numerical Wave Tank." In ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/omae2023-100850.
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Abstract The Coastal & Ocean Basin (COB) is a brand-new wave-current basin in Ostend (Belgium). The basin is 30m long and 30m wide, and it is equipped with modular wavemakers on two adjacent sides. This allows generation of multi-modal seas (including the so-called crossing-sea states). A system of multiple pumps will also be installed to allow generation of currents propagating at an arbitrary angle relative to the dominant wave field. To optimally utilize this new facility, an efficient numerical equivalent of the COB has been coded based on the High-Order Spectral Method (HOSM). The first step is the addition of a secondary wavemaker to the open-source High-Order Spectral Numerical Wave Tank (HOS-NWT). This was done by calculating an additional potential for each of the wavemakers in two separate additional domains and then using them as forcing terms on the two sides of the basin where the physical wavemakers are present. The implementation was done in a generic way and is made open-source. The effectiveness of the implemented method is demonstrated by comparing three base cases: only the x-wavemaker, only the y-wavemakers and both wavemakers together. However, there still remain challenges when it comes to wave generation in the y-direction and accurately modelling the corner between the two wavemakers.
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Bouscasse, Benjamin, Andrea Califano, Young Myung Choi, Xu Haihua, Jang Whan Kim, Young Jun Kim, Sang Hun Lee, et al. "Qualification Criteria and the Verification of Numerical Waves: Part 2: CFD-Based Numerical Wave Tank." In ASME 2021 40th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/omae2021-63710.
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Abstract There is increasing interest in numerical wave simulations as a tool to design offshore structures, especially for the prediction of stochastic nonlinear wave loads like those related to air-gap and wave impact. Though the simulations cannot replace all experiments, they are now competitive on some topics such as the computations of wind and current coefficients. To proceed further it is necessary to improve the procedure to account for another complex environmental factor, wave motion. This paper addresses an industrial collaboration to develop modeling practices and qualification criteria of CFD-based numerical wave tank for offshore applications. As a part of the effort to develop reliable numerical wave modeling practices in the framework of the “Reproducible Offshore CFD JIP”, qualification criteria are formulated for the wave solutions generated from either potential-flow based codes in Part 1 of this work. Part 2 presents first a set of solutions for forcing the qualified waves obtained with the potential codes in the CFD domain. Those solutions follow a set of coupling protocols previously proposed in the JIP framework. Two potential codes and two CFD solvers are combined, so that four possible methods of generating waves and modalities are described. Two different potential models are considered, one using the higher order spectral method for numerical wave tank (HOS-NWT), and another using the finite-element method in the horizontal direction and a modal expansion after a sigma transform in the vertical direction (solver is called TPNWT). Both are equipped with a breaking model to generate extreme sea states. The two CFD solvers tested are Simcenter STAR-CCM+ and OpenFOAM. Simulation setups are proposed for both software. Simulation results from eight academic or industrial partners are presented for two sets of 2D test cases in deep water, one with regular waves and one with irregular waves, both with one very steep condition (ratio of wave height over wavelength of 10% for regular waves and 1000 year return period for Gulf of Mexico for irregular waves). The irregular waves are simulated for 10 sets of 3 hours to apply a stochastic approach to verify the quality of the waves generated in the numerical domain. Attention is given to the wave spectrum and the ensemble probability of the crest distribution, both obtained from the wave elevation at the center of the domain.