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Results
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.
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.
Lined Pipe Testing and Finite Element Modelling for Reel-lay Application
Le, Minh (Offshore Subsea Engineering, Saipem SA) | Ahmed-Kogri, Mamadou (Offshore Subsea Engineering, Saipem SA) | Stableford, Richard (Offshore Subsea Engineering, Saipem SA) | Giry, Eric (Offshore Subsea Engineering, Saipem SA)
_ In this paper, a numerical model is proposed for mechanically lined pipe (MLP). Laser-based scanning techniques were used to capture local straining of the liner and digital imaging correlation of the backing steel outer during simulated reeling trials. This included wrinkling generated by an unexpected anomaly near the transition area of one test string. Data were collected before, during, and after reeling. The numerical model developed to simulate the bending trial corresponds well with test data, proving the method useful for further MLP modelling studies. Introduction MLP is a cost-effective solution to transmit corrosive hydrocarbon fluids. A carbon steel host pipe shelters a thin tube made of CRA. The thin tube is inserted and expanded to fit the inner surface of the host pipe. A specific failure mode can occur based on delamination and collapse of the liner, known as “wrinkling,” when installed by reel laying (Vasilikis and Karamanos, 2012) or under repeated large bending (Bartolini et al., 2017). Several works were performed to address specifically the conditions that may trigger a wrinkle either from a numerical perspective or from combining experimental and numerical studies (Toguyeni and Banse, 2012). Some studies proposed criteria to anticipate the situation where liner wrinkling may occur (e.g., DNV, 2018; Tkaczyk et al., 2020; Le et al., 2021). Test campaigns were reported in recent years with dedicated instrumentation based on laser scanning to quantify the liner response and calibrate FEA (e.g., Focke et al., 2007). High-resolution measurements generate a large amount of data that require specific processing to get a valuable interpretation such as the one described by Harrison et al. (2016). Some test programmes focused on local features, such as a weld (Jones et al., 2021) or a liner imperfection (Pépin et al., 2019), that could initiate a wrinkle. However, to the authors’ knowledge, there has been no MLP bending test involving an anomaly that specifically triggers a wrinkle that is measured with high-resolution instrumentation and simulated through FEA. This paper proposes a comparison between experimental and numerical experience for such a case.
- Asia (0.68)
- Europe (0.46)
- North America > United States > California (0.28)
- Research Report > New Finding (0.48)
- Research Report > Experimental Study (0.48)
_ Seabed stability around submarine pipelines under wave-plus-current loading is one of the major issues in offshore projects. Unlike previous works that focused mainly on the evaluation of the seabed response around a single pipeline, in this study, two pipelines in tandem will be considered. The previous model (PORO-FSSI-FOAM) will be adopted to investigate the effect of the gap ratios (G/D) of twin pipes on the wave and current-induced oscillatory seabed response. The numerical model is validated with the previous experimental data for two pipelines in tandem. Based on numerical examples, the following conclusions were found: (i) when the gap ratio (G/D) is greater than 1.25, the soil response beneath both pipelines is more significant than in the condition of a single body; and (ii) the maximum liquefaction depth appears to increase as ks and Sr decrease, and ks is more sensitive to the evolution of the liquefied zone. Introduction Pipelines have been one of the essential associated installations for the oil and gas industry, which have been used for the transportation of oil and gas from offshore to onshore. Since the first offshore pipeline was built by Brown Root to carry oil in 1954, submarine pipeline networks have been regarded across the globe as the “lifelines” of the oil industry (Sumer and Fredsøe, 2002). The existence of a submarine pipeline does not only alter the nearby flow morphology, but also enhances the surrounding seafloor instability (including soil liquefaction, scour, and shear failure) and ultimately causes damage or failure of the pipeline (Sumer, 2014).
- Europe (0.93)
- North America > United States (0.46)
Experimental Study on the Vortex-Induced Vibration of a Catenary Flexible Riser under Sheared Flows
Zhu, Hongjun (Southwest Petroleum University, Chengdu) | Hu, Jie (Southwest Petroleum University, Chengdu) | Zhao, Honglei (Southwest Petroleum University, Chengdu) | Gao, Yue (Southwest Petroleum University, Chengdu)
The vortex-induced vibration (VIV) of a catenary flexible riser subjected to log-law sheared flows is experimentally investigated in a Reynolds number range of 308–953. The in-plane and out-of-plane responses are captured using the nonintrusive imaging technique. Experimental results illustrate that the mode transition is out of sync in the in-plane and out-of-plane directions, though the excited mode increases with the reduced velocity. Furthermore, the spatial variation of dominant frequency suggests the out-of-sync mode transition along the span. The predominant out-of-plane frequency is also observed in the in-plane response, whereas the in-plane dominant frequency differs when the reduced velocity is sufficiently large. Introduction The dynamic response of a circular cylinder exposed to flows is widely encountered in engineering applications. In particular, in offshore oil and gas engineering, the elongated flexible riser as a result of the increasing water depth experiences more complicated vortex-induced vibration (VIV) with the presence of multiple frequencies and mode competition. The vigorous VIV response is the main reason for structural fatigue damage: 15.8% of the submarine pipeline failures that occurred in the Gulf of Mexico during 1967–2012 were caused by VIV, as statistically reported by the Bureau of Safety and Environmental Enforcement (BSEE). These pipeline fatigue damages resulted in huge economic loss and serious environmental pollution (Marshall, 2021). Thus, a comprehensive understanding of the VIV response of flexible cylinders with a large aspect ratio is urgently required to predict and prevent fatigue failure (Wang et al., 2019). VIVs of flexible cylinders in uniform flows have been extensively investigated in past decades. The considered flexible cylinder in the experiments conducted by Song et al. (2011) has a large aspect ratio of 1,750. Although the cylinder is subject to uniform flow, asymmetric response was observed, with the highest mode reaching the sixth in the cross-flow direction. Whitney et al. (1981) pointed out that higher modes can be excited even at low towing speeds for very long marine pipes of aspect ratios 1,800, 5,400, and 10,800 with a bottom end mass. Sun et al. (2012) reported that the excited mode increased with the incident current velocity.
- North America > United States (1.00)
- Asia (1.00)
- Research Report > New Finding (0.51)
- Research Report > Experimental Study (0.51)
Time-frequency Domain Characteristics on the Dynamic Response of a Moored Floater Under a Freak Wave by Wavelet Analysis
Pan, Wenbo (Dalian University of Technology) | Zhang, Ningchuan (Dalian University of Technology) | Zeng, Fanxu (Dalian University of Technology) | Huang, Guoxing (Dalian University of Technology)
Regarding freak wave actions on structures, the majority of existing studies focus on the time-domain statistical characteristics of floaters. For the limited frequency-domain studies available, they were analyzed by adopting a conventional Fourier transform, which cannot provide the variation of energy in a time series. However, a freak wave is a spike in a random wave series, and hence the local characteristics in a time domain are of key importance. Compared with Fourier transfer, the wavelet analysis method is more effective in obtaining the energy spectral density as well as energy distribution of each frequency in time domain, especially the instantaneous physical changes under freak waves. By adopting wavelet analysis, this study manages to figure out the time-frequency domain characteristics on the dynamic responses of the moored floater under a freak wave through extensively experimental investigations. The results show that the wavelet analysis method is effective in obtaining the energy spectral density and the energy distribution of each frequency in time domain. There is a significant variation on the time-frequency domain characteristics of the dynamic response under a freak wave. The energy parameter □E of surge, heave, and pitch in freak waves can be up to 2.48, 1.88, and 1.65 times of those under random waves, respectively. Introduction Many maritime accidents demonstrate that a freak wave is a serious hazard to offshore vessels and structures. Nowadays, more and more occurrences of freak waves have been observed in the oceanographic observations globally. Therefore, it is worth investigating the security of marine structures under freak waves. On the interaction between freak waves and structures, Clauss et al. (2003) investigated the motions behavior and splitting forces of the semisubmersible GVA 4000 under a freak wave through experimental measurements and time-domain simulation. It was found that the maximum response is subjected to freak wave height. Schmittner (2005) investigated the motions and bending moments of floating production storage and offloading (FPSO) and heavy lift vessels as well as the motions and splitting forces of a semisubmersible under a freak wave.
- Asia > China (0.70)
- North America > United States (0.68)
A moving flux source is modified to predict ship waves by using NOWT-PARI (NOnlinear Wave Transformation model by the Port and Airport Research Institute), taking into account the expandability of setting ship navigation channels and applicability for representative ship shape in a harbor. The fluxes on a slender-ship sailing are generated with two functions approximating ship shape: a modified parabolic function and an interpolation of Lewis form. Through several sets of numerical simulations reproducing ship waves measured in model experiments, a tuning parameter related to the ratio of ship width and length to computational mesh size is introduced in order to secure independence of the calculation accuracy of ship waves from a spatial resolution.
Those tests are usually performed with model tanks at not possible with real fluids, but it can be reached with virtual scale 1: ( 40), filled with water and a mixture of gases chosen ones and numerically tested. If the numerical model only takes into account the density and the compressibility of the fluids, as in order to have the same gas-to-liquid density ratio as on is the case for solvers of the compressible Euler equations like board ships with Natural Gas (NG) and Liquefied Natural Gas SPH-flow, the complete similarity at both scales is reached if and (LNG). Irregular tank motions, calculated at full scale by a seakeeping only if three dimensionless numbers are kept the same at both software, are imposed to the model tank by a six-degreeof-freedom scales: the gas-to liquid density ratio (DR), and both Mach numbers hexapod after having been downscaled according to defined with the speed of sound into the gas and into the Froude similarity. This downscaling simply means that amplitudes liquid, respectively. As the reference velocity to be involved in are divided by and times are divided by . Mach numbers have to be in Froude similarity, this implies that This does not mean that the flow inside the model tank is in speeds of sound into the gas and the liquid at model scale are complete similarity with the full-scale flow. Actually, even disregarding times smaller than the corresponding ones at full scale (Braeunig the biases induced by phenomena that are present at et al., 2009).
Effect of Stress Reflection on Dynamic Stress Intensity Factor in Crack Arrest Toughness Testing
Handa, Tsunehisa (Steel Research Laboratory, JFE Steel Corporation) | Tagawa, Tetsuya (Steel Research Laboratory, JFE Steel Corporation) | Shimada, Yusuke (Nippon Steel and Sumitomo Metal Corporation) | Kawabata, Tomoya (University of Tokyo) | Inoue, Takehiro (Nippon Steel and Sumitomo Metal Corporation) | Kaneko, Masahito (Kobe Steel, Ltd.) | Sugimoto, Kei (ClassNK) | Aihara, Shuji (University of Tokyo) | Shibanuma, Kazuki (University of Tokyo)
In a brittle crack arrest toughness test, a brittle crack is initiated by an impact on the side-edge notch of a specimen subjected to a specified static test stress, and the crack arrest behavior is examined. The distance between the loading points of the specimen is one of the important test parameters. When the distance between the loading points is short, a running brittle crack tends to be easily arrested. This may be affected by the stress waves induced by the released stress during crack propagation, as the released stress waves are reflected at the loading points and return to the propagating crack line and can apply compressive stress dynamically to the propagating crack tip. Therefore, for correct evaluation of brittle crack arrest toughness in a brittle crack arrest toughness test, the influence of the reflected stress waves on crack arrest behavior must be eliminated. In the present work, the dynamic stress intensity factors for a running crack in the brittle crack arrest toughness test were calculated by dynamic elastic finite element method (FEM) analysis, and the required condition to avoid the influence of the reflected stress waves was investigated. In practical brittle crack arrest toughness tests, crack arrest toughness, Kca, is calculated by an analytical formula called a tangent formula. The consistency of the stress intensity factor, K, calculated by the analytical formula with the solutions obtained by dynamic elastic FEM was also examined.
The twin-plate breakwater, a novel permeable breakwater, was studied experimentally in the State Key Laboratory of Coastal and Offshore Engineering in Dalian, China. The dual horizontal plates were placed in parallel with the upper one at the still water level. This study is to investigate the distribution of dynamic wave pressures and wave loads on the twin-plate breakwater under the conditions of regular waves (with the relative plate width B/L = 0.28~1.43 and relative wave height H/d = 0.1~0.4) and random waves (with the relative plate width B/L = 0.2~0.66 and relative wave height Hs/d = 0.1~0.35). Effects of the relative plate width, relative wave height, and wave steepness have been addressed. The experimental results demonstrate that the effect of the relative plate width is dominant among the above parameters. For the purpose of bulk estimation in engineering applications, we overlooked the effects of the relative plate width, relative wave height, and wave steepness and obtained the best-fitting equation to predict the maximum dynamic wave pressure and wave force on the twin-plate breakwater.
- Research Report > New Finding (0.85)
- Research Report > Experimental Study (0.71)