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2026, 40(4)
:725-745.
doi: 10.1007/s13344-026-0055-8
Abstract:
Marine propellers are continually expected to achieve higher efficiency, lower noise, compactness, and improved manoeuvrability often simultaneously. However, conventional screw propellers are approaching their performance limits, prompting the exploration of unconventional propeller concepts for further advancement. This paper reviews recent studies on the hydrodynamic performance of several unconventional marine propellers, including tip-loaded propellers, contra-rotating propellers, rim-driven thrusters, vertical axis propellers, tandem propellers, and toroidal propellers. The review summarizes their geometric features, hydrodynamic characteristics, advantages and limitations, underlying mechanisms, and key directions for future research. The findings indicate that: (1) not all unconventional propellers enhance efficiency, yet many offer advantages in noise, vibration, or manoeuvrability; (2) simulation-base optimisation has become the state-of-the-art approach for both design and fair performance comparison among propeller types; (3) tip-loaded and contra-rotating propellers are proven to improve propulsive efficiency, while the newly proposed toroidal propeller requires further scientific investigation; and (4) despite varying levels of technological maturity, research on cavitation, scale effect, and radiated noise remains insufficient for most unconventional propellers.
Marine propellers are continually expected to achieve higher efficiency, lower noise, compactness, and improved manoeuvrability often simultaneously. However, conventional screw propellers are approaching their performance limits, prompting the exploration of unconventional propeller concepts for further advancement. This paper reviews recent studies on the hydrodynamic performance of several unconventional marine propellers, including tip-loaded propellers, contra-rotating propellers, rim-driven thrusters, vertical axis propellers, tandem propellers, and toroidal propellers. The review summarizes their geometric features, hydrodynamic characteristics, advantages and limitations, underlying mechanisms, and key directions for future research. The findings indicate that: (1) not all unconventional propellers enhance efficiency, yet many offer advantages in noise, vibration, or manoeuvrability; (2) simulation-base optimisation has become the state-of-the-art approach for both design and fair performance comparison among propeller types; (3) tip-loaded and contra-rotating propellers are proven to improve propulsive efficiency, while the newly proposed toroidal propeller requires further scientific investigation; and (4) despite varying levels of technological maturity, research on cavitation, scale effect, and radiated noise remains insufficient for most unconventional propellers.
2026, 40(4)
:746-760.
doi: 10.1007/s13344-026-0056-7
Abstract:
This study establishes a numerical model for simulating coupled interactions of floating offshore wind turbine (FOWT) with large-scale ocean waves and wind. The volume of fluid model combined with the 6-DOF solver efficiently resolves the fluid-induced dynamic motion of FOWT in a multi-phase flow comprising air and water using Fluent. A fluid-structure interaction (FSI) analysis for FOWT integrating the k−ω Shear Stress Transport (SST) turbulent model and a structural dynamic model is conducted. The study first simulates the floating platform’s motion effects on FOWT aerodynamic performance, including surge, pitch, and yaw. Subsequently, a fully coupled calculation of the FOWT is executed using the established numerical model. The aerodynamic hydrodynamic interactions of the FOWT under combined wind and wave effects are simulated. The complex unsteady flow fields considering blade and tower interference effects among blade-tip vortices, shedding vortices, and turbulent wakes are numerically visualized and examined in detail. Additionally, the study investigates the effects of inflow wind conditions, wave conditions, and blade and tower flexibility, calculating time series of aerodynamic loads and aeroelastic responses through one/two-way FSI modeling.
This study establishes a numerical model for simulating coupled interactions of floating offshore wind turbine (FOWT) with large-scale ocean waves and wind. The volume of fluid model combined with the 6-DOF solver efficiently resolves the fluid-induced dynamic motion of FOWT in a multi-phase flow comprising air and water using Fluent. A fluid-structure interaction (FSI) analysis for FOWT integrating the k−ω Shear Stress Transport (SST) turbulent model and a structural dynamic model is conducted. The study first simulates the floating platform’s motion effects on FOWT aerodynamic performance, including surge, pitch, and yaw. Subsequently, a fully coupled calculation of the FOWT is executed using the established numerical model. The aerodynamic hydrodynamic interactions of the FOWT under combined wind and wave effects are simulated. The complex unsteady flow fields considering blade and tower interference effects among blade-tip vortices, shedding vortices, and turbulent wakes are numerically visualized and examined in detail. Additionally, the study investigates the effects of inflow wind conditions, wave conditions, and blade and tower flexibility, calculating time series of aerodynamic loads and aeroelastic responses through one/two-way FSI modeling.
2026, 40(4)
:761-776.
doi: 10.1007/s13344-026-0057-6
Abstract:
This study proposes a fence-type permeable breakwater composed of multiple strategically arranged fences along the wave barrier. A wave-generating and absorbing boundary condition is implemented within the OpenFOAM framework—an open-source computational fluid dynamics (CFD) platform—to accurately simulate wave propagation and minimize spurious reflections. A numerical wave flume is developed to model regular wave conditions and investigate wave-structure interactions under controlled scenarios that replicate physical model tests. Transmission, reflection, and dissipation coefficients, along with the porosity of various perforated fence configurations, are evaluated and compared, supported by detailed flow field analysis. Results indicate that fence installation significantly reduces the reflection coefficient and enhances wave energy dissipation. Perforated fences effectively reduce both wave transmission and reflection while increasing energy dissipation. Optimal dissipation performance is achieved when perforations are positioned on the front face of the fence at a porosity of 10%. For practical engineering applications, perforation designs can be tailored according to specific project requirements. Flow field analysis further reveals that the fences lower water surface elevation and alter flow direction due to the perforated structure. The combined effect of these mechanisms enhances the overall wave dissipation capacity of the breakwater.
This study proposes a fence-type permeable breakwater composed of multiple strategically arranged fences along the wave barrier. A wave-generating and absorbing boundary condition is implemented within the OpenFOAM framework—an open-source computational fluid dynamics (CFD) platform—to accurately simulate wave propagation and minimize spurious reflections. A numerical wave flume is developed to model regular wave conditions and investigate wave-structure interactions under controlled scenarios that replicate physical model tests. Transmission, reflection, and dissipation coefficients, along with the porosity of various perforated fence configurations, are evaluated and compared, supported by detailed flow field analysis. Results indicate that fence installation significantly reduces the reflection coefficient and enhances wave energy dissipation. Perforated fences effectively reduce both wave transmission and reflection while increasing energy dissipation. Optimal dissipation performance is achieved when perforations are positioned on the front face of the fence at a porosity of 10%. For practical engineering applications, perforation designs can be tailored according to specific project requirements. Flow field analysis further reveals that the fences lower water surface elevation and alter flow direction due to the perforated structure. The combined effect of these mechanisms enhances the overall wave dissipation capacity of the breakwater.
2026, 40(4)
:777-792.
doi: 10.1007/s13344-026-0060-y
Abstract:
This study systematically investigates the added mass coefficient (Ca) and damping coefficient (Cb) of large-scale square and rectangular heave plates in water using Large-Eddy-Simulation (LES). A comprehensive parametric analysis examines the effects of sizes (ranging from 0.2 m×0.2 m to 5 m×5 m), Keulegan-Carpenter (KC=0.1−5) numbers, and forced oscillation frequencies (f=0.05−2 Hz) on Ca and Cb. The investigation spans laboratory-scale reduced models to near full-scale dimensions, demonstrating the practical engineering relevance of the derived hydrodynamic coefficients for full-scale applications. The findings indicate that Ca exhibits a piecewise linear relationship with the KC number, while Cb follows a cubic trend. Both coefficients become frequency-independent when f ≥ 0.2 Hz. The thickness ratio demonstrates minimal impact on Ca and Cb when below 1/50, and square heave plates with lengths between 0.2 m and 5 m show no significant size effect. Furthermore, as the aspect ratio approaches 1, Ca increases, while Cb remains relatively constant. Based on these analyses, enhanced correction formulas for calculating Ca and Cb are proposed, offering improved accuracy and broader parameter applicability for both square and rectangular heave plates. This research provides comprehensive insights for predicting hydrodynamic performance and optimizing the engineering design of square and rectangular heave plates in marine applications.
This study systematically investigates the added mass coefficient (Ca) and damping coefficient (Cb) of large-scale square and rectangular heave plates in water using Large-Eddy-Simulation (LES). A comprehensive parametric analysis examines the effects of sizes (ranging from 0.2 m×0.2 m to 5 m×5 m), Keulegan-Carpenter (KC=0.1−5) numbers, and forced oscillation frequencies (f=0.05−2 Hz) on Ca and Cb. The investigation spans laboratory-scale reduced models to near full-scale dimensions, demonstrating the practical engineering relevance of the derived hydrodynamic coefficients for full-scale applications. The findings indicate that Ca exhibits a piecewise linear relationship with the KC number, while Cb follows a cubic trend. Both coefficients become frequency-independent when f ≥ 0.2 Hz. The thickness ratio demonstrates minimal impact on Ca and Cb when below 1/50, and square heave plates with lengths between 0.2 m and 5 m show no significant size effect. Furthermore, as the aspect ratio approaches 1, Ca increases, while Cb remains relatively constant. Based on these analyses, enhanced correction formulas for calculating Ca and Cb are proposed, offering improved accuracy and broader parameter applicability for both square and rectangular heave plates. This research provides comprehensive insights for predicting hydrodynamic performance and optimizing the engineering design of square and rectangular heave plates in marine applications.
2026, 40(4)
:793-805.
doi: 10.1007/s13344-026-0059-4
Abstract:
The integration of flexible rubber-like materials into wave energy converters (WECs) holds significant potential for advancing commercial-scale wave energy exploitation. This study investigates a flexible spindle-shaped oscillating buoy (OB) moored to the seabed via a hydraulic power take-off (PTO) system. By combining viscous flow theory with the modal expansion method, a hybrid computational fluid dynamics (CFD)-finite element method (FEM) model is developed to simulate interactions among the external wave field, internal pneumatic pressure, and structural response of the flexible WEC. The hybrid CFD–FEM model accurately resolves structural dynamics—including both heave (rigid-body motion) and elastic (non-rigid) deformation modes—while simultaneously capturing wave scattering effects induced by the flexible OB. Compared with rigid counterparts, the flexible OB harvests additional wave power by effectively exploiting generalized deformation modes, enabling hydrodynamic efficiency to exceed 100% within certain wave periods. More importantly, the deformation of the flexible body reduces radiated waves and enables recovery of this energy component through elastic mode activation. However, conventional single-PTO configurations limit conversion of deformation-induced mechanical energy into electrical power. To address this limitation, multiple discrete PTO units are distributed across the body surface to ensure efficient harvesting of available deflections. Due to the reduced hydrostatic restoring stiffness inherent in the flexible OB design, the optimal PTO damping coefficient for each wave period is moderately higher than that of a rigid OB.
The integration of flexible rubber-like materials into wave energy converters (WECs) holds significant potential for advancing commercial-scale wave energy exploitation. This study investigates a flexible spindle-shaped oscillating buoy (OB) moored to the seabed via a hydraulic power take-off (PTO) system. By combining viscous flow theory with the modal expansion method, a hybrid computational fluid dynamics (CFD)-finite element method (FEM) model is developed to simulate interactions among the external wave field, internal pneumatic pressure, and structural response of the flexible WEC. The hybrid CFD–FEM model accurately resolves structural dynamics—including both heave (rigid-body motion) and elastic (non-rigid) deformation modes—while simultaneously capturing wave scattering effects induced by the flexible OB. Compared with rigid counterparts, the flexible OB harvests additional wave power by effectively exploiting generalized deformation modes, enabling hydrodynamic efficiency to exceed 100% within certain wave periods. More importantly, the deformation of the flexible body reduces radiated waves and enables recovery of this energy component through elastic mode activation. However, conventional single-PTO configurations limit conversion of deformation-induced mechanical energy into electrical power. To address this limitation, multiple discrete PTO units are distributed across the body surface to ensure efficient harvesting of available deflections. Due to the reduced hydrostatic restoring stiffness inherent in the flexible OB design, the optimal PTO damping coefficient for each wave period is moderately higher than that of a rigid OB.
2026, 40(4)
:806-818.
doi: 10.1007/s13344-026-0061-x
Abstract:
This study presents a graded multi-chamber oscillating water column (OWC) wave energy device designed to enhance broadband wave energy extraction. An experimental campaign was conducted to characterize the free decay behavior and natural frequencies of the multi-chamber OWC system, and to investigate its energy capture performance, reflection, and transmission characteristics under various operating conditions. From free decay tests, the natural frequencies of the water columns were determined, and these corresponded to the peak efficiency locations of their respective sub-chambers. The differences in natural frequencies among individual chambers contribute to an extended energy capture bandwidth in the graded multi-chamber OWC device, offering insights for broadband wave energy converter design. Moreover, the system achieved a maximum hydrodynamic efficiency of 89.84% within the tested range. By optimizing the opening ratios, a cumulative hydrodynamic efficiency exceeding 60% was achieved across the tested frequency range. Appropriate adjustment of the opening ratios also enabled effective wave absorption for longer-period waves.
This study presents a graded multi-chamber oscillating water column (OWC) wave energy device designed to enhance broadband wave energy extraction. An experimental campaign was conducted to characterize the free decay behavior and natural frequencies of the multi-chamber OWC system, and to investigate its energy capture performance, reflection, and transmission characteristics under various operating conditions. From free decay tests, the natural frequencies of the water columns were determined, and these corresponded to the peak efficiency locations of their respective sub-chambers. The differences in natural frequencies among individual chambers contribute to an extended energy capture bandwidth in the graded multi-chamber OWC device, offering insights for broadband wave energy converter design. Moreover, the system achieved a maximum hydrodynamic efficiency of 89.84% within the tested range. By optimizing the opening ratios, a cumulative hydrodynamic efficiency exceeding 60% was achieved across the tested frequency range. Appropriate adjustment of the opening ratios also enabled effective wave absorption for longer-period waves.
2026, 40(4)
:819-836.
doi: 10.1007/s13344-026-0058-5
Abstract:
The power take-off (PTO) mechanism, a crucial component in wave energy converters (WECs), plays an essential role in controlling motion and power conversion. This article examines the control mechanisms of the point-absorber wave energy converter, specifically addressing the multiple constraints related to damping and displacement. To optimize energy capture efficiency, a Model Predictive Control (MPC) framework is implemented and its performance is evaluated. Through reformulation of the time-lag function and derivation of the state-space equation, a predictive model and objective function for the control algorithm are established. A comprehensive model combining theoretical analysis with numerical simulations is constructed to simulate converter behavior under various sea conditions. This methodology enables the identification of optimal control strategies under different constraints, thereby enhancing wave energy conversion. The simulation results demonstrate that without external constraints, MPC and optimal damping control perform similarly in energy conversion optimization. However, when subject to external constraints such as PTO damping force and displacement, MPC demonstrates superior performance than optimal damping control in both regular and irregular waves, particularly near the absorber’s natural frequency.
The power take-off (PTO) mechanism, a crucial component in wave energy converters (WECs), plays an essential role in controlling motion and power conversion. This article examines the control mechanisms of the point-absorber wave energy converter, specifically addressing the multiple constraints related to damping and displacement. To optimize energy capture efficiency, a Model Predictive Control (MPC) framework is implemented and its performance is evaluated. Through reformulation of the time-lag function and derivation of the state-space equation, a predictive model and objective function for the control algorithm are established. A comprehensive model combining theoretical analysis with numerical simulations is constructed to simulate converter behavior under various sea conditions. This methodology enables the identification of optimal control strategies under different constraints, thereby enhancing wave energy conversion. The simulation results demonstrate that without external constraints, MPC and optimal damping control perform similarly in energy conversion optimization. However, when subject to external constraints such as PTO damping force and displacement, MPC demonstrates superior performance than optimal damping control in both regular and irregular waves, particularly near the absorber’s natural frequency.
2026, 40(4)
:837-847.
doi: 10.1007/s13344-026-0062-9
Abstract:
Wake interactions significantly influence the aerodynamic performance and energy efficiency of wind farms, yet their complex dynamics under realistic atmospheric conditions remain insufficiently resolved. This study employs large-eddy simulation (LES) with full-geometry overset grids to investigate the wake characteristics of the NREL 5 MW wind turbine under varying turbulence intensities and shear inflow conditions. Numerical validations against experimental data and established LES results confirm the reliability of the model. The analysis focuses on wake velocity distribution, recovery dynamics, vortex evolution, and turbulence intensity fields. Results demonstrate that increasing turbulence intensity markedly accelerates wake recovery by enhancing convective mixing, reducing the recovery distance by approximately 25%−30% when turbulence intensity rises from 5% to 15%. Shear inflow introduces vertical asymmetry, with faster recovery in the upper wake due to greater free-stream energy replenishment, while the lower wake remains constrained by near-ground shear. Vortex structure analysis using the Q-criterion reveals that higher turbulence intensities promote earlier vortex fragmentation, intensifying mixing and accelerating energy redistribution. Conversely, shear inflow weakens lower vortex systems but enhances cross-wake vortex interactions. These findings elucidate the coupled effects of shear and turbulence on wake development and highlight their implications for optimizing turbine spacing and wind farm layouts. The results provide actionable insights for designing more efficient and resilient wind energy systems.
Wake interactions significantly influence the aerodynamic performance and energy efficiency of wind farms, yet their complex dynamics under realistic atmospheric conditions remain insufficiently resolved. This study employs large-eddy simulation (LES) with full-geometry overset grids to investigate the wake characteristics of the NREL 5 MW wind turbine under varying turbulence intensities and shear inflow conditions. Numerical validations against experimental data and established LES results confirm the reliability of the model. The analysis focuses on wake velocity distribution, recovery dynamics, vortex evolution, and turbulence intensity fields. Results demonstrate that increasing turbulence intensity markedly accelerates wake recovery by enhancing convective mixing, reducing the recovery distance by approximately 25%−30% when turbulence intensity rises from 5% to 15%. Shear inflow introduces vertical asymmetry, with faster recovery in the upper wake due to greater free-stream energy replenishment, while the lower wake remains constrained by near-ground shear. Vortex structure analysis using the Q-criterion reveals that higher turbulence intensities promote earlier vortex fragmentation, intensifying mixing and accelerating energy redistribution. Conversely, shear inflow weakens lower vortex systems but enhances cross-wake vortex interactions. These findings elucidate the coupled effects of shear and turbulence on wake development and highlight their implications for optimizing turbine spacing and wind farm layouts. The results provide actionable insights for designing more efficient and resilient wind energy systems.
2026, 40(4)
:848-861.
doi: 10.1007/s13344-026-0063-8
Abstract:
The liner of mechanically lined pipe (MLP), which depends on mechanical residual contact pressure for attachment to the carrier pipe, risks wrinkling when subjected to large curvatures. A novel type of MLP, termed adhesively bonded mechanically lined pipe (ABMLP), has been recently developed to address this limitation. Beyond the residual contact pressure generated during manufacturing, ABMLP incorporates additional adhesive strength between the liner and carrier. To evaluate the ultimate bending capacity of ABMLP, this research established bending models utilizing both finite element methods and theoretical analysis. The adhesive layer was simulated using an element-based cohesive zone model (CZM). Results indicate that the adhesive in ABMLP effectively delays liner separation compared with MLP; however, substantial curvatures may still induce localized adhesive damage. Furthermore, sensitivity analyses examined critical adhesive layer parameters, including cohesive stiffness, strength, and fracture energy. The findings reveal that stiffness influences circumferential damage distribution in the adhesive layer, while cohesive strength and fracture energy substantially impact damage extent. Moreover, early adhesive layer failure diminishes the pipeline’s load-bearing capacity.
The liner of mechanically lined pipe (MLP), which depends on mechanical residual contact pressure for attachment to the carrier pipe, risks wrinkling when subjected to large curvatures. A novel type of MLP, termed adhesively bonded mechanically lined pipe (ABMLP), has been recently developed to address this limitation. Beyond the residual contact pressure generated during manufacturing, ABMLP incorporates additional adhesive strength between the liner and carrier. To evaluate the ultimate bending capacity of ABMLP, this research established bending models utilizing both finite element methods and theoretical analysis. The adhesive layer was simulated using an element-based cohesive zone model (CZM). Results indicate that the adhesive in ABMLP effectively delays liner separation compared with MLP; however, substantial curvatures may still induce localized adhesive damage. Furthermore, sensitivity analyses examined critical adhesive layer parameters, including cohesive stiffness, strength, and fracture energy. The findings reveal that stiffness influences circumferential damage distribution in the adhesive layer, while cohesive strength and fracture energy substantially impact damage extent. Moreover, early adhesive layer failure diminishes the pipeline’s load-bearing capacity.
2026, 40(4)
:862-872.
doi: 10.1007/s13344-026-0064-7
Abstract:
A thin-walled liner is widely employed to rehabilitate deep-buried pipelines. This bi-material lined-pipeline system may be situated in geohazard-prone regions, posing significant risks to structural integrity. This study proposes a systematic theoretical methodology to assess the seismic response of lined-pipelines subjected to strike-slip fault displacements. The strain distribution within the deformed system is determined by introducing an admissible transverse displacement function, while the onset of yielding in the lined pipeline is explicitly predicted using the classical beam-yield criterion. The formulated solutions are validated effectively against numerical simulations. Parametric studies subsequently evaluate the influence of the thickness ratio and fault plane inclination on strain development and yielding behavior. Results indicate that a greater fault plane inclination induces higher yield displacement in the lined-pipeline, while the yield strength of the liner exerts minimal influence on system-level yielding.
A thin-walled liner is widely employed to rehabilitate deep-buried pipelines. This bi-material lined-pipeline system may be situated in geohazard-prone regions, posing significant risks to structural integrity. This study proposes a systematic theoretical methodology to assess the seismic response of lined-pipelines subjected to strike-slip fault displacements. The strain distribution within the deformed system is determined by introducing an admissible transverse displacement function, while the onset of yielding in the lined pipeline is explicitly predicted using the classical beam-yield criterion. The formulated solutions are validated effectively against numerical simulations. Parametric studies subsequently evaluate the influence of the thickness ratio and fault plane inclination on strain development and yielding behavior. Results indicate that a greater fault plane inclination induces higher yield displacement in the lined-pipeline, while the yield strength of the liner exerts minimal influence on system-level yielding.
2026, 40(4)
:873-887.
doi: 10.1007/s13344-026-0065-6
Abstract:
Offshore heavy oil production is transitioning from steam flooding to in-situ combustion (ISC). To accurately evaluate the risk boundary of the combustion-zone casing section in injection wells during the ignition-combustion process, a dynamic risk assessment framework is proposed by integrating a time-dependent Kriging model with stress-strength interference theory. Thermo-mechanical finite element simulations are first conducted, alongside high-temperature tensile and creep tests on TP110H casing steel, which is widely used in offshore thermal recovery wells. These tests are performed over a temperature range from ignition to peak combustion temperatures to characterize the temperature-dependent mechanical behavior of casing materials under ISC conditions. A Kriging model is then constructed to extrapolate these data and characterize material behavior under continuously varying bottom-hole temperatures. Subsequently, Monte Carlo simulation is employed to sample random operating conditions, and the dynamic casing failure probability is evaluated using stress-strength interference theory. The results indicate that the failure probability of the combustion-zone casing section remains below 0.1% within the temperature range of 400−500 °C, but increases sharply to 34.66% when the temperature exceeds 500 °C. The proposed framework provides a practical approach for casing risk assessment under extreme high-temperature conditions and offers theoretical guidance for casing material selection, safety threshold determination, and completion strategy optimization in high-temperature production wells.
Offshore heavy oil production is transitioning from steam flooding to in-situ combustion (ISC). To accurately evaluate the risk boundary of the combustion-zone casing section in injection wells during the ignition-combustion process, a dynamic risk assessment framework is proposed by integrating a time-dependent Kriging model with stress-strength interference theory. Thermo-mechanical finite element simulations are first conducted, alongside high-temperature tensile and creep tests on TP110H casing steel, which is widely used in offshore thermal recovery wells. These tests are performed over a temperature range from ignition to peak combustion temperatures to characterize the temperature-dependent mechanical behavior of casing materials under ISC conditions. A Kriging model is then constructed to extrapolate these data and characterize material behavior under continuously varying bottom-hole temperatures. Subsequently, Monte Carlo simulation is employed to sample random operating conditions, and the dynamic casing failure probability is evaluated using stress-strength interference theory. The results indicate that the failure probability of the combustion-zone casing section remains below 0.1% within the temperature range of 400−500 °C, but increases sharply to 34.66% when the temperature exceeds 500 °C. The proposed framework provides a practical approach for casing risk assessment under extreme high-temperature conditions and offers theoretical guidance for casing material selection, safety threshold determination, and completion strategy optimization in high-temperature production wells.
2026, 40(4)
:888-900.
doi: 10.1007/s13344-026-0066-5
Abstract:
This study investigates methods to enhance the bearing capacities of pile foundations in coral sand through vertical bearing capacity model tests on coral sand samples. The tests examined single piles and pile groups with varying expansion agent dosages and pile spacings using high-performance calcium sulfoaluminate (HCSA)-based self-compacting expansion piles. The research proposes a combined systematic calculation and numerical simulation method for evaluating the bearing capacities of single piles and pile groups, with results validated through field testing. The findings demonstrate that pile end and side resistances increased significantly when incorporating appropriate HCSA expansive agent. A single pile with 15% mixing agent showed 43.75% larger ultimate bearing capacity compared with one without expansive agent. The load-settlement (Q-S) curve for single piles in coral sand foundations exhibited steep decline with a distinct downward turning point, indicating rapid failure. In contrast, pile groups showed gradual deformation without a clear turning point, suggesting progressive failure. The pile group effect was significant at spacings of 3d–4.5d (d represents pile diameter) but negligible at 6d. Coral sand foundations demonstrated stronger pile group effects than conventional sand at equivalent spacings, following reversible pile group effect patterns. These findings provide valuable guidance for pile foundation design in marine engineering projects utilizing coral sand.
This study investigates methods to enhance the bearing capacities of pile foundations in coral sand through vertical bearing capacity model tests on coral sand samples. The tests examined single piles and pile groups with varying expansion agent dosages and pile spacings using high-performance calcium sulfoaluminate (HCSA)-based self-compacting expansion piles. The research proposes a combined systematic calculation and numerical simulation method for evaluating the bearing capacities of single piles and pile groups, with results validated through field testing. The findings demonstrate that pile end and side resistances increased significantly when incorporating appropriate HCSA expansive agent. A single pile with 15% mixing agent showed 43.75% larger ultimate bearing capacity compared with one without expansive agent. The load-settlement (Q-S) curve for single piles in coral sand foundations exhibited steep decline with a distinct downward turning point, indicating rapid failure. In contrast, pile groups showed gradual deformation without a clear turning point, suggesting progressive failure. The pile group effect was significant at spacings of 3d–4.5d (d represents pile diameter) but negligible at 6d. Coral sand foundations demonstrated stronger pile group effects than conventional sand at equivalent spacings, following reversible pile group effect patterns. These findings provide valuable guidance for pile foundation design in marine engineering projects utilizing coral sand.
2026, 40(4)
:901-915.
doi: 10.1007/s13344-026-0067-4
Abstract:
The global expansion of offshore wind turbine (OWT) installations into seismically active regions has heightened concerns about their performance under earthquake loading. Beyond harsh environmental loads, seismic events can severely disrupt OWT operations, potentially resulting in permanent shutdowns. Incorporating soil-structure interaction (SSI) effects significantly influences their resilience and stability—factors that are critical yet poorly understood. Furthermore, the impacts of near-field and far-field ground motions on the seismic SSI behavior of jacket-supported OWTs remain unexplored, representing a critical knowledge gap. Therefore, this study investigates the influence of pulse-like ground motions on the nonlinear dynamic responses of jacket-supported OWT systems, accounting for SSI effects. A high-fidelity numerical model is developed and validated to ensure accuracy within the modeling framework. Following validation, extensive numerical simulations are conducted using earthquake records with and without velocity pulse characteristics. The results elucidate the interplay among pulse-type classifications, SSI effects, and the seismic response of jacket-supported OWTs, thereby supporting improved seismic design and analysis practices for such structures.
The global expansion of offshore wind turbine (OWT) installations into seismically active regions has heightened concerns about their performance under earthquake loading. Beyond harsh environmental loads, seismic events can severely disrupt OWT operations, potentially resulting in permanent shutdowns. Incorporating soil-structure interaction (SSI) effects significantly influences their resilience and stability—factors that are critical yet poorly understood. Furthermore, the impacts of near-field and far-field ground motions on the seismic SSI behavior of jacket-supported OWTs remain unexplored, representing a critical knowledge gap. Therefore, this study investigates the influence of pulse-like ground motions on the nonlinear dynamic responses of jacket-supported OWT systems, accounting for SSI effects. A high-fidelity numerical model is developed and validated to ensure accuracy within the modeling framework. Following validation, extensive numerical simulations are conducted using earthquake records with and without velocity pulse characteristics. The results elucidate the interplay among pulse-type classifications, SSI effects, and the seismic response of jacket-supported OWTs, thereby supporting improved seismic design and analysis practices for such structures.
2026, 40(4)
:916-929.
doi: 10.1007/s13344-026-0070-9
Abstract:
This study establishes a nonlinear surge motion model of a tension-leg platform wind turbine (TLPWT) under combined aerodynamic and hydrodynamic loads in the form of a Duffing type oscillator. The nonlinear restoring force is derived by considering stretching tendons and platform set-down motions, with the analytical solution obtained through the harmonic balance method (HBM). The motion stability is analyzed using stability algorithms, and the boundary is determined through Floquet theory. The research examines the effects of system dynamic parameters and environmental loads on the TLPWT surge model. Analysis of the Duffing oscillator model reveals that TLPWT surge exhibits an unstable region characterized by multiple coexisting periodic solutions due to nonlinear stiffness. This instability manifests in both low-frequency and high-frequency regions, with saddle-node bifurcation occurring at the stable boundary. Reduced damping expands the unstable region, while increased linear stiffness shifts it toward higher frequencies. Greater nonlinear stiffness reduces response amplitudes but expands the unstable region while compressing the high-frequency stable region. Wave force significantly affects resonance peak and vibration amplitude in the low-frequency region, whereas wind force shows minimal impact on motion amplitude and stability. The study also investigates bifurcation characteristics under failure conditions, including tendon and blade pitch failures.
This study establishes a nonlinear surge motion model of a tension-leg platform wind turbine (TLPWT) under combined aerodynamic and hydrodynamic loads in the form of a Duffing type oscillator. The nonlinear restoring force is derived by considering stretching tendons and platform set-down motions, with the analytical solution obtained through the harmonic balance method (HBM). The motion stability is analyzed using stability algorithms, and the boundary is determined through Floquet theory. The research examines the effects of system dynamic parameters and environmental loads on the TLPWT surge model. Analysis of the Duffing oscillator model reveals that TLPWT surge exhibits an unstable region characterized by multiple coexisting periodic solutions due to nonlinear stiffness. This instability manifests in both low-frequency and high-frequency regions, with saddle-node bifurcation occurring at the stable boundary. Reduced damping expands the unstable region, while increased linear stiffness shifts it toward higher frequencies. Greater nonlinear stiffness reduces response amplitudes but expands the unstable region while compressing the high-frequency stable region. Wave force significantly affects resonance peak and vibration amplitude in the low-frequency region, whereas wind force shows minimal impact on motion amplitude and stability. The study also investigates bifurcation characteristics under failure conditions, including tendon and blade pitch failures.
2026, 40(4)
:930-945.
doi: 10.1007/s13344-026-0068-3
Abstract:
Wave motion in variable sea states affects SOV operation times, particularly SOV-RM. A hybrid framework, further extended to an Adaptive Transformer–Transfer Learning (AdaTF–TL) approach, is proposed. By integrating an adaptive transformer architecture with transfer learning, the framework aims to extend the feasible construction windows for SOV operations. Temporal Similarity Quantization (TSQ) quantifies inter- and intra-sequence distribution shifts in SOV-RM caused by wave frequency and direction. Intra-sequence heterogeneity is mitigated through Dynamic Weighted Distance (DWD), which adjusts feature weights via adaptive attention. For inter-sequence heterogeneity across sea states, a Dynamic Unfreezing Strategy (DUS) transfers pre-trained model parameters for conditional probability alignment. Validation under sea states 3–6, using Pierson–Moscowitz and Longuet–Higgins spectra, demonstrates that the Adaptive Transformer–Transfer Learning (AdaTF–TL) framework achieves a prediction accuracy of 99.18%, outperforming four comparative models, including AdaRNN. Its robustness is further confirmed through RT-LAB–based simulations.
Wave motion in variable sea states affects SOV operation times, particularly SOV-RM. A hybrid framework, further extended to an Adaptive Transformer–Transfer Learning (AdaTF–TL) approach, is proposed. By integrating an adaptive transformer architecture with transfer learning, the framework aims to extend the feasible construction windows for SOV operations. Temporal Similarity Quantization (TSQ) quantifies inter- and intra-sequence distribution shifts in SOV-RM caused by wave frequency and direction. Intra-sequence heterogeneity is mitigated through Dynamic Weighted Distance (DWD), which adjusts feature weights via adaptive attention. For inter-sequence heterogeneity across sea states, a Dynamic Unfreezing Strategy (DUS) transfers pre-trained model parameters for conditional probability alignment. Validation under sea states 3–6, using Pierson–Moscowitz and Longuet–Higgins spectra, demonstrates that the Adaptive Transformer–Transfer Learning (AdaTF–TL) framework achieves a prediction accuracy of 99.18%, outperforming four comparative models, including AdaRNN. Its robustness is further confirmed through RT-LAB–based simulations.
2026, 40(4)
:946-958.
doi: 10.1007/s13344-026-0071-8
Abstract:
The hybrid pile-bucket foundation represents an innovative alternative to conventional monopile foundations for supporting offshore wind turbines (OWTs). Given the significant horizontal loads experienced by OWTs, this study comprehensively examines the horizontal ultimate bearing capacity of hybrid pile-bucket foundations in clay through model testing, finite element analysis, and upper bound limit analysis. The study analyzes how varying height-to-diameter (H/D) ratios affect the horizontal bearing capacity through model testing, revealing characteristic failure patterns and instability mechanisms. Finite element analysis validates the experimental results and elucidates the failure mechanism and velocity field of pile-bucket foundations under horizontal loading. Upper bound solutions for horizontal ultimate bearing capacity are derived using the virtual work equation, with detailed analysis of energy dissipation rate contributions from each component. The calculated upper bound solution demonstrates reasonable agreement with experimental and literature values, validating the proposed failure mode and methodology. These findings establish a theoretical foundation for the design and optimization of pile-bucket foundations.
The hybrid pile-bucket foundation represents an innovative alternative to conventional monopile foundations for supporting offshore wind turbines (OWTs). Given the significant horizontal loads experienced by OWTs, this study comprehensively examines the horizontal ultimate bearing capacity of hybrid pile-bucket foundations in clay through model testing, finite element analysis, and upper bound limit analysis. The study analyzes how varying height-to-diameter (H/D) ratios affect the horizontal bearing capacity through model testing, revealing characteristic failure patterns and instability mechanisms. Finite element analysis validates the experimental results and elucidates the failure mechanism and velocity field of pile-bucket foundations under horizontal loading. Upper bound solutions for horizontal ultimate bearing capacity are derived using the virtual work equation, with detailed analysis of energy dissipation rate contributions from each component. The calculated upper bound solution demonstrates reasonable agreement with experimental and literature values, validating the proposed failure mode and methodology. These findings establish a theoretical foundation for the design and optimization of pile-bucket foundations.
2026, 40(4)
:959-970.
doi: 10.1007/s13344-026-0072-7
Abstract:
This study investigates the flow characteristics around a newly designed offshore groin in the basin behind a pile-supported wharf to facilitate effective silt dredging. Detailed flow measurements are conducted around the groin in a current flume during peak ebb and flood tides. Laboratory results document the flow acceleration regime between the groin and the wharf. The Reynolds-Averaged Navier-Stokes (RANS) equations with a k−ε turbulence closure are implemented to establish a numerical flume using the computational fluid dynamics (CFD) tool FLOW-3D. The numerical model is validated through experimental flow measurements. The horizontal mean flow field, turbulent kinetic energy, and vorticity field around the groin are examined numerically under both tidal conditions. The effects of design parameters, including groin length, orientation, location, and incoming tidal current on flow acceleration around the groin are analyzed through numerical simulations. Results indicate that flow acceleration around the groin head and the extent of the effective accelerating region increase significantly with greater groin length and alongshore orientation angle, while remaining relatively unaffected by incoming tidal current variations. As the groin shifts shoreward from the wharf to the shoreline, flow deceleration persists around the groin head, while the effective accelerating region reaches its maximum at a specific distance from the wharf.
This study investigates the flow characteristics around a newly designed offshore groin in the basin behind a pile-supported wharf to facilitate effective silt dredging. Detailed flow measurements are conducted around the groin in a current flume during peak ebb and flood tides. Laboratory results document the flow acceleration regime between the groin and the wharf. The Reynolds-Averaged Navier-Stokes (RANS) equations with a k−ε turbulence closure are implemented to establish a numerical flume using the computational fluid dynamics (CFD) tool FLOW-3D. The numerical model is validated through experimental flow measurements. The horizontal mean flow field, turbulent kinetic energy, and vorticity field around the groin are examined numerically under both tidal conditions. The effects of design parameters, including groin length, orientation, location, and incoming tidal current on flow acceleration around the groin are analyzed through numerical simulations. Results indicate that flow acceleration around the groin head and the extent of the effective accelerating region increase significantly with greater groin length and alongshore orientation angle, while remaining relatively unaffected by incoming tidal current variations. As the groin shifts shoreward from the wharf to the shoreline, flow deceleration persists around the groin head, while the effective accelerating region reaches its maximum at a specific distance from the wharf.
2026, 40(4)
:971-984.
doi: 10.1007/s13344-026-0073-6
Abstract:
The turning maneuver performance of multi-body towing systems is crucial for navigation safety and efficiency, particularly in polar regions where ice floes impair turning capability. This paper presents a numerical model for simulating towing system turning operations in broken ice using the discrete element method (DEM). Numerical ice fields comprising polygon-shaped ice floes are generated randomly using the centroidal Voronoi tessellation (CVT) algorithm. The towline connecting the tug and towed structure is modeled as a catenary system. The Newmark-beta method resolves the coupled motions of tug, towed structure, and ice floes incrementally. The analysis examines turning processes for single and multiple tug configurations in ice-infested waters. Additionally, the study investigates how ice and towing characteristics—including ice concentration, thickness, floe size, and towline length—influence turning performance through numerical simulations, contributing insights to ice towing maneuverability.
The turning maneuver performance of multi-body towing systems is crucial for navigation safety and efficiency, particularly in polar regions where ice floes impair turning capability. This paper presents a numerical model for simulating towing system turning operations in broken ice using the discrete element method (DEM). Numerical ice fields comprising polygon-shaped ice floes are generated randomly using the centroidal Voronoi tessellation (CVT) algorithm. The towline connecting the tug and towed structure is modeled as a catenary system. The Newmark-beta method resolves the coupled motions of tug, towed structure, and ice floes incrementally. The analysis examines turning processes for single and multiple tug configurations in ice-infested waters. Additionally, the study investigates how ice and towing characteristics—including ice concentration, thickness, floe size, and towline length—influence turning performance through numerical simulations, contributing insights to ice towing maneuverability.
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Current Issue
- Volume 40
- Issue 4
- August 2026
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- Superintended by:
CHINA ASSOCIATION FOR SCIENCE AND TECHNOLOGY
- Sponsored by:
Chinese Ocean Engineering Society （COES）
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Nanjing Hydraulic Research Institute
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