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Collaborating Authors
International Journal of Offshore and Polar Engineering
Application of Machine Learning for Prediction of Wave-induced Ship Motion
Lee, Jae-Hoon (Seoul National University, Seoul) | Lee, Jaehak (Seoul National University, Seoul) | Kim, Yonghwan (Seoul National University, Seoul) | Ahn, Yangjun (School of AI Convergence, Sungshin Women’s University, Seoul)
_ This paper investigates the possibility of the machine learning technique being applicable in the real-time prediction of wave-induced ship motions. An integrated machine learning model is proposed by considering the two different physical attributes in the equation of motion: memory effects of past motion history and excitation forces induced by incident waves. A long short-term memory layer and a single fully connected layer were combined to establish this machine learning model. A database was constructed through the impulse response function-based numerical simulations for various ocean environments. After training, short-term deterministic predictions were conducted for new environments, and the effects of ship motion records were investigated. The response amplitude operators were evaluated based on regular wave simulations. The machine learning model was observed to have successfully learned the seakeeping characteristics of a ship. Introduction Autonomous ships have emerged as an important issue in the transportation market, including the shipbuilding industry. The global market size of the autonomous ship is projected to approximately triple by 2030 (MarketsandMarkets, 2021). The development of next-generation vessels, increasing investments in autonomous ships, and the surge of demand for safety have been the primary factors presenting many new technical issues in marine automation systems (Geertsma et al., 2017). Among these issues, a real-time prediction for ship operation performance is strongly required for the navigation process to improve safety and efficiency (Lee et al., 2022). Accurate and efficient predictions of seakeeping and maneuvering, however, still remain challenging, owing to the expensive computation cost for numerical simulations (Weymouth and Yue, 2013). Existing or conventional methods have difficulty immediately responding to the provided information during a voyage.
- North America > United States (0.28)
- Asia > China (0.28)
- Shipbuilding (0.88)
- Transportation > Marine (0.34)
Numerical Modelling of Breaking Wave Impacts on Seawalls with Recurved Parapets Using qaleFOAM
Li, Qian (School of Science and Technology, City, University of London, London) | Yan, Shiqiang (School of Science and Technology, City, University of London, London) | Zhang, Yi (School of Science and Technology, City, University of London, London) | Zhang, Ningbo (School of Science and Technology, City, University of London, London) | Ma, Qingwei (School of Science and Technology, City, University of London, London) | Xie, Zhihua (School of Engineering, Cardiff University, Cardiff)
_ This paper presents a numerical comparative study on the interaction between breaking waves and vertical seawalls with a recurved parapet attached using the hybrid solver qaleFOAM, which couples a two-phase incompressible Navier–Stokes (NS) solver with the quasi-Lagrangian-Eulerian finite element method solver based on the fully nonlinear potential theory. The focus of the comparison is to reveal the possible scale effect as a result of improper scaling of the viscous effects in the model test adopting the Froude similarity in wave-structure interaction practices. For this purpose, both a 1:8 scale model test and a full-scale experiment with a large prototype model are used in the study. In the NS solver of the qaleFOAM, both a laminar model and k- shear stress transport model are adopted. The wave elevations at different locations and the impact pressure on the seawall are investigated. It is concluded that the performance of the qaleFOAM is similar for both the scaled and full-scale modelling; the viscosity, turbulence, and air compressibility may be critical for the formation of the breaking waves, which eventually affects the prediction of the impact load. Introduction An understanding of the loads induced by large waves on seawalls is important for seawall design and construction, as the occurrence of extreme weather events has become more frequent. Both the maximum wave loading and the runup on the seawall are critical criteria. Compared with increasing the seawall height, installing a recurved parapet on the top of the seawall has a greater benefit on reducing overtopping by diverting the upward water flow back to the sea. Experimental work by Ravindar et al. (2022) has confirmed the effectiveness of the recurved parapet and categorized four types of wave impacts, including (1) the aerated impact, where the wave breaks in front of the wall and hits the wall with aerated water; (2) the air pocket impact, where the wave crest hits the wall, enclosing a thin air bubble; (3) the flip through impact, where the wave crest hits the wall and runs up without trapping any air bubble; and (4) the sloshing impact, where the run-up of the wave is higher than the wave crest so that the wave crest hits the water layer instead of the wall.
- Research Report > Experimental Study (0.94)
- Research Report > New Finding (0.68)
Numerical Comparative Study on Violent Wave Interactions with a Curved Seawall
Chen, Shuling (School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu) | Hu, Xiao (School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu) | Cui, Fuyin (School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu) | Wang, Wei (School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu)
_ The seawall is a classic structure for coastal protection. The ability to predict the wave loading and runup on the seawall plays a critical role in the design of the seawall, particularly in a high sea state and/or during a storm condition involving wave breaking and violent wave impact. This paper contributes to the numerical comparative study organized by the International Hydrodynamics Committee at the 32nd International Ocean and Polar Engineering Conference (ISOPE 2022), in which the wave load on a curved seawall with different scales was considered. The computational fluid dynamic software STAR-CCM+ was used to predict the wave elevations and wave-induced pressure on the seawall, as well as to quantify the turbulence effects through comparing the results from a laminar flow simulation and the corresponding large eddy simulation. It can be concluded that the results of the present study can reasonably capture the feature of the wave impact observed in the experimental data. More important, the results confirm that the turbulence effect is insignificant during the impact for both small-scale and full-scale modeling. Introduction As a classic coastal protection infrastructure, the seawall has been widely used in practice. The most critical parameters to be considered in seawall design are the maximum wave loading and runup on the seawall. The former is linked with the structural safety of the seawall, and the latter contributes to the evaluation of the probability of overtopping and coastal flooding. Great effort has been devoted to the design and optimisation of the seawall geometry aiming to reduce the wave loads and runup. Typical approaches include the curved front (e.g., De Chowdhury et al., 2017) and vertical seawall with parapets installed on the top (e.g., Castellino et al., 2018; Dong et al., 2021). The latter has been proven to be an effective design to avoid overtopping through diverting the wave toward the seaward direction (Ravindar et al., 2019, 2021, 2022; Stagonas et al., 2020; Ravindar and Sriram, 2021). The recurved parapet (e.g., Ravindar et al., 2022) in particular has attracted interest because it has the benefit of reducing the wave loads.
- Asia > China (0.28)
- North America > United States > California (0.28)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics (0.86)
- Data Science & Engineering Analytics > Information Management and Systems (0.68)
- Reservoir Description and Dynamics > Reservoir Simulation (0.68)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.48)
_ The interaction of a breaking wave and a vertical seawall with a recurved parapet attached is investigated using a three-dimensional parallel model based on a constrained interpolation profile (CIP); the model is accelerated by high-performance computation using the message passing interface algorithm and open multiprocessing algorithm. The Navier– Stokes equations are solved using the projection method. A high-order finite difference method, the CIP method, is applied for the convection term. In a volume of fluid method, the tangent of hyperbola for interface capturing with a slope weighting method is used to simulate the variation of the free surface. Numerical results are compared with the experimental results, and good agreement is obtained. The wave impact pressures on the vertical seawall attached with the recurved parapet are accurately predicted. Moreover, the large deformation of the wave profiles of the transient wave impact process is finely simulated, which can help us better assess the reliability and survivability of these structures in the presence of extreme loads. Introduction As the global climate warms and sea levels continue to rise, it is very important to reduce the damage of overtopping and slamming load to the vertical seawall in extreme events. A sea-facing overhang structure, the so-called recurved parapet, can be attached to a new or existing vertical seawall. The overhang structure, which forces the upward rushing water and towering waves to curl toward the sea, can release the energy of the waves back into the sea and reduce the damage to the structure. This process involves problems such as wave breaking, air trapping, and wave slamming (Ravindar et al., 2019). How to accurately predict the impact load and wave climb is a challenging topic both for the effectiveness of numerical models and for the accuracy of physical experiments (Liu et al., 2020).
_ This paper numerically investigates breaking wave interaction with a vertical wall attached with a recurved parapet in 1:8 model scale, as part of the ISOPE-2022 comparative study. The in-house CFD solver naoe-FOAM-SJTU based on the open source platform OpenFOAM is used to perform all simulations. For wave generation, a novel generating-absorbing boundary condition (GABC) is adopted to replace the time-consuming moving boundary wavemaker. A geometric volume-of-fluid (VOF) method based on piecewise-linear interface calculation (PLIC) is incorporated in the present numerical model to capture the sharp interface and improve the accuracy of the predicted impact pressure. The time history and frequency analysis of the wave elevation and pressure at each probe are compared with the experimental data. The comparison demonstrates that the present numerical model is able to predict the impact pressure with sufficient accuracy but gives less accurate results of wave elevation. Moreover, the evolutions of free surface, pressure, and vorticity distribution are further provided to achieve a better understanding of this complex wave-structure interaction issue as a good complement to the experiments. Introduction Vertical breakwaters are typical coastal structures intended to reduce the effects of incoming waves, especially in extreme sea conditions. In practical design, wave overtopping has been a significant issue of sustained concern for decades. Among the various solutions, a parapet fixed on the top of the vertical wall has been proven effective by deflecting back the up-rushing water seawards. However, according to previous studies, the shape and parameters of the parapet will significantly influence the impact force and pressure compared with the original vertical wall. To provide guidelines to predict the wave impact and wave loading, it is necessary to systematically investigate the variations under different wave conditions, including non-breaking and broken waves.
- North America (0.46)
- Asia > India (0.28)
Two-phase CFD Simulation of Breaking Waves Impacting a Coastal Vertical Wall with a Recurved Parapet
Benoit, Michel (EDF R&D, Laboratoire National d’Hydraulique et Environnement (LNHE)) | Benguigui, William (EDF R&D, Dept. Mécanique des Fluides, Energies et Environnement (MFEE)) | Teles, Maria (EDF R&D, Laboratoire National d’Hydraulique et Environnement (LNHE)) | Robaux, Fabien (Saint-Venant Hydraulics Laboratory (Ecole des Ponts, EDF R&D)) | Peyrard, Christophe (EDF R&D, Laboratoire National d’Hydraulique et Environnement (LNHE))
_ Breaking wave impacts on seawalls are simulated using a multiphase three-dimensional computational fluid dynamics (CFD) software, neptune_cfd; the focus here is on a particular layout composed of a plane-sloping bottom and a vertical wall with a recurved parapet on top of it. The goal is to assess the capabilities and performances of the solver to predict the propagation of regular waves over the variable bathymetry (including shoaling and nonlinear effects), the depth-induced breaking process, and the interaction of these breaking waves with the seawall. We simulate two experiments involving similar geometries of the seabed and seawall, performed at two different scales (1:8 for case A and 1:1 for case B). After a description of the CFD solver and its numerical methods, the model is applied to the simulation of the two cases involving high-impact pressure peaks at some places on the wall surface. Numerical results are compared with experimental data regarding both free surface elevation and pressure on the wall. In general, a correct agreement between numerical predictions and experiments is obtained for free surface elevation, including the breaking zone. The time history of pressure variations for different positions along the wall during wave impacts is correctly reproduced. Although the measured maximum impact pressure peaks exhibit some variability among successive impacts, the order of magnitude of these maximum pressures is well predicted for case A. For case B, however, the maximum impact pressures are somewhat underestimated by the current simulations (requiring further tests and improvements), because the elevation of the wave impact on the wall happens to be a bit lower in the simulation. Introduction The impact of breaking waves on marine and coastal structures is a question of central interest for many applications, as extremely high-pressure peaks at the wall can occur depending on the characteristics of the breaking wave and the shape of the jet impacting the wall, the dynamics of air entrapment, and the shape of the wall (see, e.g., Oumeraci et al., 1993). Such impact issues are encountered with offshore structures in deep, intermediate, or finite water depth (e.g., oil and gas platforms; monopiles; or floating structures supporting offshore wind turbines, coastal or harbor breakwaters, vertical quays, and seawalls). Breaking wave impact can also occur in liquified natural gas tanks in some particular sloshing conditions (e.g., Ibrahim, 2020).
Comparative Study on Breaking Waves Interaction with Vertical Wall Retrofitted with Recurved Parapet in Small and Large Scale
Saincher, Shaswat (Indian Institute of Technology Madras, India) | Sriram, V. (Indian Institute of Technology Madras, India) | Ravindar, R. (Indian Institute of Technology Madras, India) | Yan, Shiqiang (City University of London) | Stagonas, Dimitris (University of Cyprus, Cyprus) | Schimmels, Stefan (Forschungszentrum Küste (FZK), Leibniz University of Hannover & Technische Universität Braunschweig, Germany) | Xie, Zhihua (Cardiff University, UK) | Benoit, Michel (EDF R&D, France) | Benguigui, William (EDF R&D, France) | Teles, Maria (EDF R&D, France) | Robaux, Fabien (Ecole des Ponts ParisTech, France) | Peyrard, Christophe (EDF R&D, France) | Asiikkis, Andreas T. (University of Cyprus, Cyprus) | Frantzis, Charalambos (Cyprus Marine and Maritime Institute, Cyprus) | Vakis, Antonis I. (University of Groningen, The Netherlands) | Grigoriadis, Dimokratis G. E. (University of Cyprus, Cyprus) | Li, Qian (City University of London) | Ma, Qingwei (City University of London) | Zhang, Ningbo (City University of London) | Zheng, Kaiyuan (Zhejiang University, China) | Zhao, Xizeng (Zhejiang University, China) | Hu, Xiao (Jiangsu University of Science and Technology, China) | Chen, Shuling (Jiangsu University of Science and Technology, China) | Chen, Songtao (Shanghai Jiao Tong University, China) | Meng, Qingjie (Wuhan Second Ship Design and Research Institute, China) | Zhao, Weiwen (Shanghai Jiao Tong University, China) | Wan, Decheng (Shanghai Jiao Tong University, China)
_ This paper presents the ISOPE-2022 conference comparative study on the interaction between breaking waves and a vertical wall with a recurved parapet. The experiments, on the basis of which the comparative study has been conducted, were carried out at small scale (1:8) in the Department of Ocean Engineering, IIT Madras, as well as at large scale (1:1) in the Großer Wellenkanal (GWK), Hannover. The paper discusses the qualitative and quantitative comparisons between 10 different numerical solvers from various universities across the world. The numerical solvers presented in this paper are the recent state of the art in the field; some are commercial, and some have been developed in-house by various academic institutes. The participating codes have been benchmarked for their ability to capture interactions between the incident waves and waves reflected from the seawall. The codes have also been benchmarked for their ability to replicate multiple loading cycles, in time domain, evaluated at selected pressure probe locations over the vertical wall and recurved parapet. The same pressure-time histories have also been compared in the frequency domain to evaluate the solvers’ capability to capture the multitude of harmonics characterizing the impact load. Furthermore, the values of peak impact pressure over five loading cycles have been compared to assess the overall robustness of the codes in simulating repeated impact events at model and prototype scales. Introduction In the field of ocean and coastal engineering, today’s computational fluid dynamics (CFD) practitioners have a wide array of solvers to choose from. These include general-purpose commercial codes, longstanding, community-developed open-source codes, as well as up-and-coming in-house codes that are usually tailor-made for specific applications. These developments in numerical modeling have been complemented with equally great strides in physical modeling wherein an increasing number of experiments are being conducted at (e.g., Stagonas et al., 2020) or close to the prototype-scale (e.g., Ravindar and Sriram, 2021). As the number of international collaborations increase in academia, more and more researchers now have access to experimental datasets despite the fact that there exist only a handful of large-scale experimental facilities worldwide. This presents an opportunity to conduct massively collaborative computational studies in which numerical solvers belonging to several different classes of methodologies are applied to the same problem and are then compared mutually as well as against the experimental data. Some examples of such comparative studies include: ISOPE Benchmark 1 (Clément, 1999), ISOPE Benchmark 2 (Tanizawa and Clément, 2000), Loysel et al. (2012), Ransley et al. (2019, 2020), and, more recently, Sriram et al. (2021) and Agarwal et al. (2021). Collaborative computational studies are beneficial in that they: (a) help in developing a broad understanding of the capabilities of different algorithms toward simulating a particular class of problems, (b) help in establishing best practices in CFD modeling wherein, more often than not, it is identifying the constituents of the “best simulation” that matters more than identifying the “best solver,” and (c) provide researchers with an opportunity to place their self-developed codes under assessment and gain confidence through the benchmarking process.
_ To measure loads induced by nonimpacting waves on a vertical piercing cylinder, tests were performed in a 17 m long wave tank at the École Centrale Marseille. Different configurations of the cylinder (shape and size of the section and length) were studied for two focusing waves. Wave loads as calculated by the Morison equation were compared with measurements. The context for this experiment is the assessment of the hydrodynamic loads as a result of sloshing on the pump tower in liquefied natural gas tanks on floating structures. The comparisons turn out to be good in all cases studied, provided the Morison equation is used with relevant time series of liquid velocities and accelerations. Introduction Liquefied natural gas (LNG) membrane tanks are largely used on different kinds of floating structures such as LNG carriers, floating liquefied natural gas vessels, floating storage regasification units, LNG-fueled ships (LFSs), LNG bunker vessels, and all small-scale related applications. In these tanks, the liquefied gas remains in conditions close to thermodynamic equilibrium (-162°C at atmospheric pressure). Depending on the application, the volume of LNG tanks for floating structures ranges from a few thousand cubic meters for LFS or small-scale applications to about 55,000 m for tanks of the largest LNG carriers. Whatever the application, the shapes of these tanks are always prismatic, with large upper chamfers and smaller lower chamfers. The tanks do not include any structure that could mitigate LNG sloshing except a pump tower. As can be seen in Fig. 1, the pump tower is a tubular, vertical, stainless steel structure that enables the loading and unloading of the LNG, thanks to pumps located at its base. It is mainly made of three large vertical pipes: the emergency pipe at the front and two discharge pipes at the rear, connected together by struts. Located at the rear of the tank, in the central part but not necessarily exactly in the middle, it hangs from the liquid dome and is horizontally guided at its base by the pump tower base support.
- North America > United States (0.46)
- Asia (0.28)
- Europe > France > Provence-Alpes-Côte d'Azur > Bouches-du-Rhône > Marseille (0.25)
- Energy > Oil & Gas > Midstream (1.00)
- Transportation > Freight & Logistics Services > Shipping > Tanker (0.74)
Numerical Investigation of the Local Scour Around Subsea Pipelines in Combined Steady and Oscillatory Flow
Dhamelia, Vatsal (Western Sydney University, Penrith) | Zhao, Ming (Western Sydney University, Penrith) | Hu, Pan (Western Sydney University, Penrith) | Mia, Mohammad Rashed (Western Sydney University, Penrith)
_ Submarine pipelines have played a significant role in coastal, marine, and offshore engineering for transporting offshore oil and gas to shore. Over the last few decades, identifying the cause of pipeline failure has been a top interest for many researchers. Local scour is reported to be one of the main causes that threaten the safety of subsea pipelines. A great number of experimental and numerical studies have been performed to investigate local scour around subsea pipelines. Oscillatory and steady flows are commonly used to model flow near the seafloor induced by the motion of waves and currents, respectively. However, the studies of local scour around combined steady and oscillatory flow are limited. In this study, local scour around subsea pipelines under combined steady and oscillatory flow is investigated using the numerical method. The numerical model comprises Reynolds-averaged Navier-Stokes flow model, k-ω turbulence model, sediment transport model, and seabed evolution model. The effects of the combined flow ratio of the steady to oscillatory flow velocities on the scour are quantified and discussed. Introduction Over the last few decades, local scour below submarine pipelines has been studied extensively, because it has strong potential for causing pipeline failure in the ocean environment. If a pipeline is exposed to the flow or shallowly buried, the difference between the upstream and downstream pressure of the pipeline causes the onset of scour (Sumer et al., 2001; Zang et al., 2009, 2021). After the onset of scour, the increased flow velocity through the small gap between the pipeline and erodible bed leads to strong amplification of shear stress on the bed, which is the acting force for sediment transport and scour. Local scour problems have drawn many researchers to perform extensive experimental and numerical studies over the years.
Update on the Fatigue Strength of Large-size Bolt-assemblies in Steel Constructions
Glienke, Ralf (University of Applied Sciences Technology, Business and Design, Wismar) | Schwarz, Mathias (Fraunhofer-Institute for Large Structures in Production Engineering IGP, Rostock) | Johnston, Carol (TWI Ltd.) | Hagemann, Melanie (University of Applied Sciences Technology, Business and Design, Wismar) | Seidel, Marc (Siemens Gamesa Renewable Energy GmbH & Co. KG)
_ The fatigue strength of structural steel bolts is significantly affected by variables introduced during manufacturing. These factors are generally inconsistent in the design codes, depending on the set of rules used. In particular for large-diameter bolts, such as those used in abundance in wind turbines, an experimental basis for evaluating various impacts was only available to a very limited extent in the past. This paper evaluates the results of three different high-strength bolt systems with varying manufacturing conditions. The test basis covers a diameter range between M12 and M72 and focuses on tests with high, representative mean stress levels. In addition to the results of fatigue tests, fractographic investigations of fracture pattern growth are included in this study. Introduction In the last few years, reduction of electricity generation costs— i.e., Levelized Cost of Energy (LCoE)—has gained massive importance in wind energy. The effects of LCoE optimization include significantly faster increases in rotor diameter and turbine rating, as well as pressure to generate even more cost-effective plants. The tower has always played an important role in the total cost of a plant, approximately 20%–30% of the total. Therefore, optimized and lightweight tower structures are important (Lange and Elberg, 2017; Schaumann et al., 2021).