{"title":"Electro-mechanical vibration control of functionally graded marine risers by a piezoelectric meta-structure design","authors":"Feng Liang , Zhi-Qiang Chen","doi":"10.1016/j.apor.2024.104388","DOIUrl":"10.1016/j.apor.2024.104388","url":null,"abstract":"<div><div>In this paper, a novel electro-mechanical meta-riser structure is designed aiming to suppress its vibration and wave propagation. The riser is made of porous functionally graded material (FGM), and is periodically attached with piezoelectric layers, each of which is connected with a multi-mode resonant shunt circuit to trigger multiple locally resonant (LR) band gaps (BGs). The periodically varying rigidity due to piezoelectric layers can also generate Bragg scattering (BS) BGs, resulting in a hybrid meta-structure. A point defect is introduced into the system by removing a certain piezoelectric layer. Theoretical analysis and finite element (FE) simulation both demonstrate the superior vibration control effect of the present meta-structure. Owing to the presence of defect, the riser presents a remarkable vibration response within the original BS BGs, reflecting the vibration energy localization and enabling energy harvesting by meta-structure designs. Different circuit designs and parameters can be used to regulate LR BGs, while the particular material composition of the riser will contribute to enhancing the BS BG performance. This study can provide a technical scheme for the vibration and elastic wave control of marine riser structures, and lay a theoretical foundation for the vibration energy harvesting by utilizing dynamical meta-structures.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104388"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143167007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Numerical study of asymmetric pitching amplitude effects on energy extraction performance of a semi-activated hydrofoil in shear flows","authors":"Hengliang Qu , Xueyan Li , Jinhai Zheng","doi":"10.1016/j.apor.2024.104410","DOIUrl":"10.1016/j.apor.2024.104410","url":null,"abstract":"<div><div>As a representative tidal current energy device, the operational stability and energy extraction performance of hydrofoils are significantly influenced by shear flow. Inspired by natural models, including insects, birds, and fish, the amplitude asymmetric pitching has been proposed as a strategy to mitigate the adverse impacts of the shear flow. A 2-dimensional (2D) numerical model of a semi-activated hydrofoil was developed using ANSYS-Fluent computational fluid dynamics software to assess the feasibility of amplitude asymmetric pitching. Hydrofoils employing the asymmetric and symmetric pitching motions under uniform and shear flows were studied. The hydrodynamic response and energy extraction performance of the hydrofoil were compared at various shear rates, pitching amplitudes, and asymmetric ratios. The results indicate that amplitude asymmetric pitching enhances both the operational stability and energy extraction performance of the hydrofoil under shear flow conditions. The appropriate asymmetric ratio for stable operation and energy extraction varies depending on the pitching amplitude and shear rate. Appropriate asymmetric ratios were determined using the trial-and-error method. Additionally, flow field comparisons between the asymmetric and symmetric pitching motions elucidated the underlying mechanisms. The amplitude asymmetric pitching does not completely eliminate the adverse effects of shear flow on the hydrofoil's energy extraction performance. The power coefficient of the hydrofoil with an appropriate asymmetric ratio decreases with increasing shear rate.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104410"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhongxiang Zhang , Su Chen , Yongzhi Wang , Xiaojun Li
{"title":"Experimental study on the effect of an underground structure on the seismic responses of saturated coral sand site","authors":"Zhongxiang Zhang , Su Chen , Yongzhi Wang , Xiaojun Li","doi":"10.1016/j.apor.2024.104392","DOIUrl":"10.1016/j.apor.2024.104392","url":null,"abstract":"<div><div>Understanding the effect of underground structures on the seismic responses of saturated coral sand sites is crucial for improving seismic design and preventing liquefaction disasters in island reef engineering. Despite advancements in this field, the specific effects of underground structures on the seismic behavior of coral sand sites remain underexplored. This study addresses this issue by conducting dynamic centrifuge shaking table tests on saturated coral sand sites, both with and without an underground structure. The seismic responses between the free field (FF) and structure field (SF) were compared in terms of pore pressure, acceleration, response spectra, and shear stress-strain behavior. Test results reveal that the presence of the underground structure led to a deeper liquefaction zone beneath it. The excess pore pressure in the soil layer above the structure dissipated rapidly after peaking and completely dissipated by the end of the seismic motions. Additionally, the soil near the bottom of the structure exhibited higher dilatancy. The structure amplified the acceleration of the soil above and near its bottom while reducing the acceleration of the soil adjacent to its sidewall. In the period range of 0.9–3.0 s, the presence of the structure weakened the attenuation of response spectra values for the soil adjacent to the sidewall and above the structure. Furthermore, the structure limited the deformation of the soil adjacent to its sidewall and increased the soil shear modulus.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104392"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Shoreline retreat and free overhang in overdeveloped tombolo behind detached breakwaters: Empirical, semi-analytical and numerical approach","authors":"Changbin Lim , Jung L. Lee , John R.C. Hsu","doi":"10.1016/j.apor.2024.104385","DOIUrl":"10.1016/j.apor.2024.104385","url":null,"abstract":"<div><div>Multiple detached breakwaters with narrow gaps have been constructed to dissipate wave energy to a beach and to promote salient or tombolo in the lee for shore protection since the 1960s. Although geometric parameters (breakwater length and distance offshore) are operative for the preliminary design of these structures, neither shoreline retreat from its initial position in the middle of each compartment was assessed, empirically or semi-analytically, nor was the tombolo's overhang length along the structure quantified, if it's overdeveloped. In this study, prototype data are collected to derive empirical relationship for a salient and tombolo geometry in static equilibrium. A semi-analytical approach is then used to derive algebraic equation for estimating shoreline retreat from an initial position, for three stages of shoreline planform, from a salient to initial tombolo and to an over-developed tombolo with free overhang. The results of this new approach are verified using empirical data and an approximate equation for shoreline retreat derived from the numerical results extended from the results of XBeach model. This also enables the backtracking to the existing shoreline, where extra hard protection is constructed in the middle of a compartment between consecutive DBWs, to its initial position. To mitigate the scenario of erosion, a preferred alternative combining nourishment with parabolic model is demonstrated to produce a stable beach with adequate beach buffer.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104385"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Ripple-averaged wave boundary layer over long-crest sand ripples at high Reynolds number: Observations and theoretical model","authors":"Jing Yuan , Deping Cao","doi":"10.1016/j.apor.2024.104357","DOIUrl":"10.1016/j.apor.2024.104357","url":null,"abstract":"<div><div>Long-crest sand ripples are common bedform features developed by moderate shoaling waves in the coastal environment. The spanwise coherent vortex (SCV) generated in the lee side controls the behavior of ripple-averaged (RA) flow, which is of primary interest to coastal modelers. However, few theoretical model explicitly describes the spatial-averaged flow within the sub-crest region (or ripple sublayer). To close this gap, this study first analyzed some recent high-Reynolds-number experiments with real and fixed ripples in an oscillatory water tunnel. The RA flow has a typical structure of wave boundary layer, i.e., a dominant first harmonic with an overshoot structure. The swirling motion of SCV transfers momentum like the swept and ejection of wall turbulence. The effective stress is most significant within the ripple sublayer, and contains a third harmonic, which is about half of the first harmonic. To model the RA flow, the governing equation is specified by examining the momentum budget. The final form of governing equation is similar to that of conventional oscillatory boundary layer, except for a drag term, which represents the pressure force from the ripple surface. The depth-invariant and time-varying effective viscosity proposed by Davies and Villaret (1997) is adopted, and the drag term is assumed to be linearly proportional to RA velocity. An analytical solution is derived and compared to the measurements. The model can yield satisfactory predictions of the first-harmonic flow. Switching off the drag term will lead to much worse prediction, suggesting the necessity of having it for modeling the sublayer. The model is the basis for further developing models that includes higher-order physics, e.g., wave propagation or wave–current interactions.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104357"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yiming Zhou , Jinhua Zhang , Kai Long , Ayesha Saeed , Tao Tao , Jianjun Chen
{"title":"Topology optimization on a jacket structure for offshore wind turbines by altering structural design domain","authors":"Yiming Zhou , Jinhua Zhang , Kai Long , Ayesha Saeed , Tao Tao , Jianjun Chen","doi":"10.1016/j.apor.2025.104421","DOIUrl":"10.1016/j.apor.2025.104421","url":null,"abstract":"<div><div>Topology optimization (TO) has been proven as a potent tool for offshore wind turbine supporting structure design. Typical TO methods optimize the material layout within a specific and fixed design domain that has previously been established. An investigation on the topology optimization design of jacket structure is conducted by altering the design domain, which is expanded by adopting two strategies of extending upwards and enlarging the distance between the legs at the bottom. The weighted and normalized compliance in two typical loading cases is adopted as the objective function subject to available material usage. The checkerboards are suppressed by minimum size constraints in the commercial software Optistruct ™, and geometrical symmetry is imposed to assure an identical material layout on four surfaces. Two sequences of innovative designs are automatically generated by the proposed strategies including expanding the leg distance and extending upwards to replace portions of the tower. To verify these optimized results, the jacket structures are reconstructed based on the initial structures and force transmission paths. Various structural responses such as the fundamental frequency of the entire offshore wind turbine, maximum displacement, and pull-out forces are investigated and analyzed to demonstrate the superiority of the presented approach in comparison to the reference structure. The effects of various parameters including water depth, wave height and system damping of a particular optimized structure are discussed. The resultant trends provide several suggestions for the jacket design.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104421"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tiesheng Liu , Yanjun Liu , Shuting Huang , Gang Xue
{"title":"Influence of the hydraulic power take-off system on the dynamic response and power output of a wind-wave hybrid system","authors":"Tiesheng Liu , Yanjun Liu , Shuting Huang , Gang Xue","doi":"10.1016/j.apor.2024.104359","DOIUrl":"10.1016/j.apor.2024.104359","url":null,"abstract":"<div><div>The power take-off (PTO) system plays a crucial role in the wind-wave hybrid system that directly affects the efficiency of wave energy conversion and the relative motion between buoys and the platform. The hydraulic PTO system, a commonly used type of wave energy conversion, has demonstrated practicality and reliability in practical projects. Effects of the hydraulic PTO system on the dynamic response and power output of the hybrid system are unclear due to the limitations of current simulation tools. Therefore, based on potential flow theory, the Laplace equation, blade element momentum theory, and others, this paper proposes an aero-hydro-servo-hydraulic-mooring fully coupled simulation method. The effect of hydraulic parameters (i.e., the piston area, motor displacement, orifice area, equivalent damping, initial volume, and pre-charge pressure) on the hybrid system is studied. The results show that the hydraulic parameters significantly influence the natural periods of heave and pitch of the platform, with variation amplitudes of 14.2 % and 12.27 %, respectively. The phase and amplitude of the PTO force significantly influence the surge, heave, and motion responses of the platform. For deterministic sea states, the same set of hydraulic parameters cannot simultaneously maximize the power generation of the WEC micro array and minimize the pitch motion response of the platform. Hydraulic parameters have negligible effect on the average values of the power generation and rotor torque of the wind turbine, but affect the amplitudes. Furthermore, the established framework can effectively simulate the working process of the hydraulic PTO system in a wind-wave hybrid system, which can provide essential pre-research for the actual hydraulic control to improve the wave energy conversion efficiency and hybrid system stability.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104359"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xingjia Jiang , Yingwei Dai , Suhan Li , Ranqi Ma , Taili Du , Yongjiu Zou , Peng Zhang , Yuewen Zhang , Peiting Sun
{"title":"Research on ship speed prediction based on time series imaging and deep convolutional network fusion method","authors":"Xingjia Jiang , Yingwei Dai , Suhan Li , Ranqi Ma , Taili Du , Yongjiu Zou , Peng Zhang , Yuewen Zhang , Peiting Sun","doi":"10.1016/j.apor.2024.104384","DOIUrl":"10.1016/j.apor.2024.104384","url":null,"abstract":"<div><div>Ship speed prediction is crucial for ship operation and safe navigation, providing precise data support for route planning and optimization, port operational efficiency enhancement, navigation system development, etc. Currently, the computational accuracy of the existing ship speed prediction methods faces great challenges. To enhance the precision and efficiency of ship speed prediction, an innovative method applying time series imaging technology for ship speed prediction is proposed. In this method, time series data is first sliced and converted into two-dimensional images. The data points of each period are converted into pixels in the image, and the intensity or color depth of the pixels represents the corresponding size of the data values. Subsequently, a deep convolutional network prediction model is constructed and trained to predict ship speed accurately. Finally, the effectiveness of the proposed method is validated using two sets of ship speed data, with a mean square error of 0.08 on the open-source dataset and 0.026 on the real ship dataset. The results indicate that the proposed method can achieve accurate prediction of ship speed.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104384"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Estimation of sound speed profile based on optimal spatial correlation radius: A case study of the Northwest Pacific","authors":"Yuyao Liu, Yu Chen, Wei Chen, Zhou Meng","doi":"10.1016/j.apor.2024.104408","DOIUrl":"10.1016/j.apor.2024.104408","url":null,"abstract":"<div><div>As one of the significant factors in determining the propagation mode of the underwater acoustic signal, the accurate acquisition of the sound speed profile (SSP) is crucial for constructing underwater acoustic systems. Ocean observation data are sparse on a horizontal scale, making the accurate estimation of the SSP based on available data become a research hotspot in oceanography and hydroacoustics. In this paper, we propose the concept of spatial correlation radius (SCR) of the SSP sets for the first time and achieve an accurate estimation of the SSP based on the optimal spatial correlation radius (O-SCR). Taking the Northwest Pacific as an example, the Argo float profile data of multiyear are employed to build a database of the O-SCR and conduct validation. The results show that the proposed strategy can effectively estimate the SSPs with a mean absolute error of less than 2.5 m/s. An eddy is identified via our frame, and the estimated core depth differs from the true depth by 6.7%. The acoustic transmission loss (TL) results illustrate that the proposed method can achieve more accurate acoustic field prediction in a distance-dependent environment. The estimation of the SSP based on the O-SCR provides a dependable technique for the precise perception of ocean sound speed field-acoustic field environment.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104408"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Phase-resolved prediction of ocean wave field using video prediction","authors":"Tatsuya Kaneko , Hidetaka Houtani , Ryota Wada , Tomoya Inoue","doi":"10.1016/j.apor.2024.104358","DOIUrl":"10.1016/j.apor.2024.104358","url":null,"abstract":"<div><div>Short-term phase-resolved ocean wave field prediction is desired for safe and efficient offshore operation. The dynamics of ocean waves are influenced by ambient currents, nonlinearity, and finite depth, which are difficult to characterize analytically. In this paper, we propose the application of video prediction methods by training the model with in-situ wave characteristics. The problem is set as predicting 5 s future waves in the square area within the predictable zone, using the surface elevation time-series data observed in the <span><math><mo>∼</mo></math></span>200 m <span><math><mo>×</mo></math></span> <span><math><mo>∼</mo></math></span>200 m range as input. The proposed model was evaluated using publicly available observational ocean wave field data and synthetic wave data compared to the 2D-FFT method based on linear wave theory. As a result, the video prediction showed higher accuracy than 2D-FFT for ocean wave field data. The key to successful wave prediction with observational data could be that the complex wave propagation property in the ocean was learned through in-situ training. Any explicit modeling of physics that can affect the wave propagation property is not necessary for wave prediction with video prediction.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104358"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143167001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}