2023 Vol.37(5)
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2023, 37(5): 709-724.
doi: 10.1007/s13344-023-0060-0
Abstract:
With the development of large liquid cargo ships, liquid tank sloshing has gradually become a hot research topic in the area of shipping and ocean Engineering. Liquid tank sloshing, characterized by strong nonlinearity and randomness, not only affects the stability of the ship but also generates a huge impact force on the wall of the tank. To further investigate liquid tank sloshing, a comprehensive review is given on the research process of the most focused subjects of liquid sloshing. Summarizing the existing research will help to identify issues in the current field and provide useful references. The methods for investigating sloshing, the research progress and the situations worldwide are discussed. The advantages and defects of experiments and numerical simulations are also explored. The problems which need to be explored in the future are subsequently proposed.
With the development of large liquid cargo ships, liquid tank sloshing has gradually become a hot research topic in the area of shipping and ocean Engineering. Liquid tank sloshing, characterized by strong nonlinearity and randomness, not only affects the stability of the ship but also generates a huge impact force on the wall of the tank. To further investigate liquid tank sloshing, a comprehensive review is given on the research process of the most focused subjects of liquid sloshing. Summarizing the existing research will help to identify issues in the current field and provide useful references. The methods for investigating sloshing, the research progress and the situations worldwide are discussed. The advantages and defects of experiments and numerical simulations are also explored. The problems which need to be explored in the future are subsequently proposed.
2023, 37(5): 725-737.
doi: 10.1007/s13344-023-0061-z
Abstract:
Accurate simulation of the horizontal-two-dimension (H2D) focused wave group in deep water requires high accuracy of a numerical model. The two-layer Boussinesq-type model (Liu and Fang, 2016; Liu et al., 2018) with the highest spatial derivative of 2 has high accuracy in both linear and nonlinear properties. Based on the further development of the velocity equations (Liu et al., 2023), the H2D numerical model for water waves is established with the prediction−correction-iteration model in the finite difference method, and a composite fourth-order Adams−Bashforth−Moulton scheme is used for time integration. The wave generation method proposed by Hsiao et al. (2005) is applied and calibrated in this H2D model. The numerical calculations lead to the following three main conclusions: First, compared with the analytical solution of Stokes linear waves, the calculated velocity profiles show higher accuracy by using the improved velocity formulas. Second, the simulations of the focused multidirectional wave group are carried out, and good agreements are found, demonstrating that the present H2D numerical model shows high accuracy in simulating focused multidirectional wave groups, and the effectiveness of the improved velocity formulas is also validated. Furthermore, the velocity profiles throughout the computational domain at the time of maximum wave crest are given. Finally, the FFT method is used to obtain the amplitude with different frequencies for several locations, and the changes of the wavelet energy spectrum at different locations are presented for several cases.
Accurate simulation of the horizontal-two-dimension (H2D) focused wave group in deep water requires high accuracy of a numerical model. The two-layer Boussinesq-type model (Liu and Fang, 2016; Liu et al., 2018) with the highest spatial derivative of 2 has high accuracy in both linear and nonlinear properties. Based on the further development of the velocity equations (Liu et al., 2023), the H2D numerical model for water waves is established with the prediction−correction-iteration model in the finite difference method, and a composite fourth-order Adams−Bashforth−Moulton scheme is used for time integration. The wave generation method proposed by Hsiao et al. (2005) is applied and calibrated in this H2D model. The numerical calculations lead to the following three main conclusions: First, compared with the analytical solution of Stokes linear waves, the calculated velocity profiles show higher accuracy by using the improved velocity formulas. Second, the simulations of the focused multidirectional wave group are carried out, and good agreements are found, demonstrating that the present H2D numerical model shows high accuracy in simulating focused multidirectional wave groups, and the effectiveness of the improved velocity formulas is also validated. Furthermore, the velocity profiles throughout the computational domain at the time of maximum wave crest are given. Finally, the FFT method is used to obtain the amplitude with different frequencies for several locations, and the changes of the wavelet energy spectrum at different locations are presented for several cases.
2023, 37(5): 738-752.
doi: 10.1007/s13344-023-0062-y
Abstract:
The motion of the moored ship in the harbor is a classical hydrodynamics problem that still faces many challenges in naval operations, such as cargo transfer and ship pairings between a big transport ship and some small ships. A mathematical model is presented based on the Laplace equation utilizing the porous breakwater to investigate the moored ship motion in a partially absorbing/reflecting harbor. The motion of the moored ship is described with the hydrodynamic forces along the rotational motion (roll, pitch, and yaw) and translational motion (surge, sway, and heave). The efficiency of the numerical method is verified by comparing it with the analytical study of Yu and Chwang (1994) for the porous breakwater, and the moored ship motion is compared with the theoretical and experimental data obtained by Yoo (1998) and Takagi et al. (1993). Further, the current numerical scheme is implemented on the realistic Visakhapatnam Fishing port, India, in order to analyze the hydrodynamic forces on moored ship motion under resonance conditions. The model incorporates some essential strategies such as adding a porous breakwater and utilizing the wave absorber to reduce the port’s resonance. It has been observed that these tactics have a significant impact on the resonance inside the port for safe maritime navigation. Therefore, the current numerical model provides an efficient tool to reduce the resonance within the arbitrarily shaped ports for secure anchoring.
The motion of the moored ship in the harbor is a classical hydrodynamics problem that still faces many challenges in naval operations, such as cargo transfer and ship pairings between a big transport ship and some small ships. A mathematical model is presented based on the Laplace equation utilizing the porous breakwater to investigate the moored ship motion in a partially absorbing/reflecting harbor. The motion of the moored ship is described with the hydrodynamic forces along the rotational motion (roll, pitch, and yaw) and translational motion (surge, sway, and heave). The efficiency of the numerical method is verified by comparing it with the analytical study of Yu and Chwang (1994) for the porous breakwater, and the moored ship motion is compared with the theoretical and experimental data obtained by Yoo (1998) and Takagi et al. (1993). Further, the current numerical scheme is implemented on the realistic Visakhapatnam Fishing port, India, in order to analyze the hydrodynamic forces on moored ship motion under resonance conditions. The model incorporates some essential strategies such as adding a porous breakwater and utilizing the wave absorber to reduce the port’s resonance. It has been observed that these tactics have a significant impact on the resonance inside the port for safe maritime navigation. Therefore, the current numerical model provides an efficient tool to reduce the resonance within the arbitrarily shaped ports for secure anchoring.
2023, 37(5): 753-767.
doi: 10.1007/s13344-023-0063-x
Abstract:
Experiments were conducted to investigate the dynamics of an oscillating bubble generated by a spark in the presence of an inclined attached air bubble. The study primarily focused on the influence of the inclination angle on the behavior of bubble jetting orientation, air bubble shape modes, and motion characteristics of the interaction between the two bubbles. Various complex bubble jetting behaviors were observed, including the presence of multiple types of bubble jetting directions, bubble splitting, and multidirectional jets. Four types of air bubble shapes were defined, namely inclined cup cover-shaped (with and without splitting), double-peaked cup cover-shaped, and inclined L-shaped air bubbles. The formation of different types of bubble jets was analyzed using the vector synthesis principle of the Bjerknes force exerted by the inclined attached air bubble and a steel plate. To describe the diverse orientations of bubble jetting and air bubble shapes, new parameters namely the dimensionless spark bubble oscillation time T* and volume ratio V* that consider the inclination angle are proposed. The findings of this investigation contribute to the existing knowledge and have the potential to further enhance methods for mitigating cavitation damage in marine, hydraulic machinery systems, and medical fields.l fields.
Experiments were conducted to investigate the dynamics of an oscillating bubble generated by a spark in the presence of an inclined attached air bubble. The study primarily focused on the influence of the inclination angle on the behavior of bubble jetting orientation, air bubble shape modes, and motion characteristics of the interaction between the two bubbles. Various complex bubble jetting behaviors were observed, including the presence of multiple types of bubble jetting directions, bubble splitting, and multidirectional jets. Four types of air bubble shapes were defined, namely inclined cup cover-shaped (with and without splitting), double-peaked cup cover-shaped, and inclined L-shaped air bubbles. The formation of different types of bubble jets was analyzed using the vector synthesis principle of the Bjerknes force exerted by the inclined attached air bubble and a steel plate. To describe the diverse orientations of bubble jetting and air bubble shapes, new parameters namely the dimensionless spark bubble oscillation time T* and volume ratio V* that consider the inclination angle are proposed. The findings of this investigation contribute to the existing knowledge and have the potential to further enhance methods for mitigating cavitation damage in marine, hydraulic machinery systems, and medical fields.l fields.
2023, 37(5): 768-780.
doi: 10.1007/s13344-023-0064-9
Abstract:
This study integrated piezoelectric layers in a flexible membrane to form a piezoelectric membrane. A fluid-filled piezoelectric membrane, which can be used as breakwater and wave energy converter simultaneously, was presented. The mathematical models to describe the interactions of the waves with the piezoelectric membrane were given. The dimensionless parameters to control the behavior of the piezoelectric membrane were obtained. The mixed Eulerian-Lagrangian method was employed to simulate the mathematical models. The simulation code was verified. Based on the simulation results, the effects of dimensionless elastic modulus of the membrane E*, tension of the membrane T0* and the resistance of the load R* on the behavior of the piezoelectric membrane were discussed. As E* is small (E*<0.04) and T0* is not too small (T0* >0.0001), the response of the piezoelectric membrane can be considered as linear. For linear response, the minimum transmission coefficient and maximum output electric power of the piezoelectric membrane can be achieved simultaneously by adjusting T0* and R*. For larger E*, nonlinear behavior of the piezoelectric membrane is observed. At some larger values of E*, working frequency of piezoelectric elements can reach eight times the wave frequency. In these cases, higher output electric power can be achieved for smaller strain of the membrane.
This study integrated piezoelectric layers in a flexible membrane to form a piezoelectric membrane. A fluid-filled piezoelectric membrane, which can be used as breakwater and wave energy converter simultaneously, was presented. The mathematical models to describe the interactions of the waves with the piezoelectric membrane were given. The dimensionless parameters to control the behavior of the piezoelectric membrane were obtained. The mixed Eulerian-Lagrangian method was employed to simulate the mathematical models. The simulation code was verified. Based on the simulation results, the effects of dimensionless elastic modulus of the membrane E*, tension of the membrane T0* and the resistance of the load R* on the behavior of the piezoelectric membrane were discussed. As E* is small (E*<0.04) and T0* is not too small (T0* >0.0001), the response of the piezoelectric membrane can be considered as linear. For linear response, the minimum transmission coefficient and maximum output electric power of the piezoelectric membrane can be achieved simultaneously by adjusting T0* and R*. For larger E*, nonlinear behavior of the piezoelectric membrane is observed. At some larger values of E*, working frequency of piezoelectric elements can reach eight times the wave frequency. In these cases, higher output electric power can be achieved for smaller strain of the membrane.
2023, 37(5): 781-793.
doi: 10.1007/s13344-023-0065-8
Abstract:
Based on the Euler-Bernoulli beam theory and Kelvin−Voigt model, a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established. The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique (GITT). The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram, phase trajectory diagram, power spectrum diagram, time-domain diagram, and Poincare map. The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system. Some new resonance phenomena can be observed, such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion, quasi-periodic motion or even chaotic motion due to the combined excitation action.
Based on the Euler-Bernoulli beam theory and Kelvin−Voigt model, a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established. The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique (GITT). The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram, phase trajectory diagram, power spectrum diagram, time-domain diagram, and Poincare map. The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system. Some new resonance phenomena can be observed, such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion, quasi-periodic motion or even chaotic motion due to the combined excitation action.
2023, 37(5): 794-806.
doi: 10.1007/s13344-023-0066-7
Abstract:
Channel avulsion is a natural phenomenon that occurs abruptly on alluvial river deltas, which can affect the channel stability. The causes for avulsion could be generally categorized as topography- and flood-driven factors. However, previous studies on avulsion thresholds usually focused on topography-driven factors due to the centurial or millennial avulsion timescales of the world’s most deltas, but neglected the impacts of flood-driven factors. In the current study, a novel demarcation equation including the two driven factors was proposed, with the decadal timescale of avulsion being considered in the Yellow River Estuary (YRE). In order to quantify the contributions of different factors in each category, an entropy-based methodology was used to calculate the contributing weights of these factors. The factor with the highest weight in each category was then used to construct the demarcation equation, based on avulsion datasets associated with the YRE. An avulsion threshold was deduced according to the demarcation equation. This avulsion threshold was then applied to conduct the risk assessment of avulsion in the YRE. The results show that: two dominant factors cover respectively geomorphic coefficient representing the topography-driven factor and fluvial erosion intensity representing the flood-driven factor, which were thus employed to define a two dimensional mathematical space in which the demarcation equation can be obtained; the avulsion threshold derived from the equation was also applied in the risk assessment of avulsion; and the avulsion threshold proposed in this study is more accurate, as compared with the existing thresholds.
Channel avulsion is a natural phenomenon that occurs abruptly on alluvial river deltas, which can affect the channel stability. The causes for avulsion could be generally categorized as topography- and flood-driven factors. However, previous studies on avulsion thresholds usually focused on topography-driven factors due to the centurial or millennial avulsion timescales of the world’s most deltas, but neglected the impacts of flood-driven factors. In the current study, a novel demarcation equation including the two driven factors was proposed, with the decadal timescale of avulsion being considered in the Yellow River Estuary (YRE). In order to quantify the contributions of different factors in each category, an entropy-based methodology was used to calculate the contributing weights of these factors. The factor with the highest weight in each category was then used to construct the demarcation equation, based on avulsion datasets associated with the YRE. An avulsion threshold was deduced according to the demarcation equation. This avulsion threshold was then applied to conduct the risk assessment of avulsion in the YRE. The results show that: two dominant factors cover respectively geomorphic coefficient representing the topography-driven factor and fluvial erosion intensity representing the flood-driven factor, which were thus employed to define a two dimensional mathematical space in which the demarcation equation can be obtained; the avulsion threshold derived from the equation was also applied in the risk assessment of avulsion; and the avulsion threshold proposed in this study is more accurate, as compared with the existing thresholds.
2023, 37(5): 807-818.
doi: 10.1007/s13344-023-0067-6
Abstract:
The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism process. In this study, the interface is discretized into multiple mesoscopic contact elements that are damaged randomly throughout the shearing process due to the natural heterogeneity. The evolution equation of damage variable is developed based on the Weibull function, which is able to cover a rather wide range of distribution shapes by only two parameters, making it applicable for varying scenarios. Accordingly, a statistical damage model is established by incorporating Mohr–Coulomb strength criterion, in which the interfacial residual strength is considered whereby the strain softening behavior can be described. A concept of “semi-softening” characteristic point on shear stress–displacement curve is proposed for effectively modeling the evolution of strain softening. Finally, a series of ring shear tests of the interfaces between fine sea sand and smooth/rough steel surfaces are conducted. The predicted results using the proposed model are compared with experimental data of this study as well as some results from existing literature, indicating that the model has a good performance in modeling the progressive failure and strain softening behavior for various types of soil–structure interfaces.
The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism process. In this study, the interface is discretized into multiple mesoscopic contact elements that are damaged randomly throughout the shearing process due to the natural heterogeneity. The evolution equation of damage variable is developed based on the Weibull function, which is able to cover a rather wide range of distribution shapes by only two parameters, making it applicable for varying scenarios. Accordingly, a statistical damage model is established by incorporating Mohr–Coulomb strength criterion, in which the interfacial residual strength is considered whereby the strain softening behavior can be described. A concept of “semi-softening” characteristic point on shear stress–displacement curve is proposed for effectively modeling the evolution of strain softening. Finally, a series of ring shear tests of the interfaces between fine sea sand and smooth/rough steel surfaces are conducted. The predicted results using the proposed model are compared with experimental data of this study as well as some results from existing literature, indicating that the model has a good performance in modeling the progressive failure and strain softening behavior for various types of soil–structure interfaces.
2023, 37(5): 819-828.
doi: 10.1007/s13344-023-0068-5
Abstract:
This research investigates the behavior of a 2×2 pile group under two-directional lateral loads in addition to the vertical load. Through three-dimensional numerical modeling based on Flac 3D software, the study examines the total bearing capacity and efficiency coefficient of the pile group, considering factors such as the angle of lateral load, relative pile spacing, and relative stiffness of the pile−soil system. The findings highlight the significance of these factors in understanding and predicting the response of pile groups to changing lateral load directions. The results reveal that increasing the angle of the lateral load from 0° to 45° enhances both the maximum total lateral load and the efficiency coefficient of the pile group. When the relative stiffness of the pile−soil system significantly increases, soil stiffening occurs and reducing the relative spacing of the piles from 7 to 3 times the diameter of the piles diminishes the influence of the pile group. Consequently, the response of the pile group to lateral loads becomes more linear, with only a slight alteration in the maximum total lateral load and the efficiency coefficient when the lateral load is angled from 0° to 45°. Conversely, increasing the relative distance between the piles, specifically from 3 to 7 times the diameter of the piles, amplifies the influence of the pile group. Both the maximum total lateral load and the efficiency coefficient of the pile group exhibit an observed increase. These provide insights for designing pile groups and optimizing their performance under lateral loading conditions.
This research investigates the behavior of a 2×2 pile group under two-directional lateral loads in addition to the vertical load. Through three-dimensional numerical modeling based on Flac 3D software, the study examines the total bearing capacity and efficiency coefficient of the pile group, considering factors such as the angle of lateral load, relative pile spacing, and relative stiffness of the pile−soil system. The findings highlight the significance of these factors in understanding and predicting the response of pile groups to changing lateral load directions. The results reveal that increasing the angle of the lateral load from 0° to 45° enhances both the maximum total lateral load and the efficiency coefficient of the pile group. When the relative stiffness of the pile−soil system significantly increases, soil stiffening occurs and reducing the relative spacing of the piles from 7 to 3 times the diameter of the piles diminishes the influence of the pile group. Consequently, the response of the pile group to lateral loads becomes more linear, with only a slight alteration in the maximum total lateral load and the efficiency coefficient when the lateral load is angled from 0° to 45°. Conversely, increasing the relative distance between the piles, specifically from 3 to 7 times the diameter of the piles, amplifies the influence of the pile group. Both the maximum total lateral load and the efficiency coefficient of the pile group exhibit an observed increase. These provide insights for designing pile groups and optimizing their performance under lateral loading conditions.
2023, 37(5): 829-841.
doi: 10.1007/s13344-023-0069-4
Abstract:
This paper presents a case study on incidents of offshore pile running in layered soils. The study provides a detailed description of the seabed soil data, pile driving records, and field surveillance video observations. Three-dimensional large deformation finite element (LDFE) analyses were conducted to retrospectively analyze the incidents, considering the remoulding of seabed soil and degradation of the pile-soil interface in the LDFE modeling. By comparing the field observations with the LDFE analysis, the mechanism of pile running was discussed, with a focus on investigating the pile penetration resistance in each layer. The study revealed that pile running in layered soils primarily resulted from a significant reduction in pile base resistance when transitioning from a strong layer to an adjacent weak layer. To further investigate the pile running mechanism in layered soils, a parametric study on the strength variation of adjacent soil layers and its influence on pile base resistance was conducted. Lastly, a simplified prediction model of pile base resistance, suitable for assessing the risk of pile running in layered soils, was proposed.
This paper presents a case study on incidents of offshore pile running in layered soils. The study provides a detailed description of the seabed soil data, pile driving records, and field surveillance video observations. Three-dimensional large deformation finite element (LDFE) analyses were conducted to retrospectively analyze the incidents, considering the remoulding of seabed soil and degradation of the pile-soil interface in the LDFE modeling. By comparing the field observations with the LDFE analysis, the mechanism of pile running was discussed, with a focus on investigating the pile penetration resistance in each layer. The study revealed that pile running in layered soils primarily resulted from a significant reduction in pile base resistance when transitioning from a strong layer to an adjacent weak layer. To further investigate the pile running mechanism in layered soils, a parametric study on the strength variation of adjacent soil layers and its influence on pile base resistance was conducted. Lastly, a simplified prediction model of pile base resistance, suitable for assessing the risk of pile running in layered soils, was proposed.
2023, 37(5): 842-848.
doi: 10.1007/s13344-023-0070-y
Abstract:
Marine equipments such as marine risers and oil pipelines operate in complex underwater environments and are usually attached by animals, plants and microorganisms. The attachment of marine fouling organisms will accelerate the corrosion damage of offshore structure and greatly reduce the service life. Studies have shown that non-smooth bionic surfaces with specific microstructures can inhibit fouling formation. Based on the idea of bionics, this paper proposes a new type of underwater flexible fretting texture, which is a composite material prepared by mixing graphene and silicone rubber, and modified by pulsed laser to construct a hexagonal bionic surface texture. Under the impact of specific water flow, the flexible texture can produce an angular displacement around 8° and a linear displacement in the amplitude range of 165 μm, and the inhibition rate of fouling biological diatoms up to 97.5%, which can effectively avoid the occurrence of marine biological fouling. The results provide a new idea for the surface protection of marine structures, which is of great significance for the development of marine industry.
Marine equipments such as marine risers and oil pipelines operate in complex underwater environments and are usually attached by animals, plants and microorganisms. The attachment of marine fouling organisms will accelerate the corrosion damage of offshore structure and greatly reduce the service life. Studies have shown that non-smooth bionic surfaces with specific microstructures can inhibit fouling formation. Based on the idea of bionics, this paper proposes a new type of underwater flexible fretting texture, which is a composite material prepared by mixing graphene and silicone rubber, and modified by pulsed laser to construct a hexagonal bionic surface texture. Under the impact of specific water flow, the flexible texture can produce an angular displacement around 8° and a linear displacement in the amplitude range of 165 μm, and the inhibition rate of fouling biological diatoms up to 97.5%, which can effectively avoid the occurrence of marine biological fouling. The results provide a new idea for the surface protection of marine structures, which is of great significance for the development of marine industry.
2023, 37(5): 849-862.
doi: 10.1007/s13344-023-0071-x
Abstract:
Fluid resonance within narrow gaps in multiple-box systems with sharp and round inlet configurations are investigated by using the potential flow and viscous fluid flow models in the OpenFOAM® package. Evident discrepancy between two numerical models can be observed for sharp inlet configurations. In addition to the dramatical decrease of resonant amplitude in narrow gaps, some peak values at the higher resonant frequencies predicted by the potential flow model even disappear in the viscous fluid flow results. The decreased normalized resonant amplitudes with the increase of incident wave amplitude can be observed for sharp inlet configurations. However, the hydrodynamic behaviors of multiple-box system with round inlet configurations between potential flow and viscous fluid flow models are quite similar with each other. The normalized resonant amplitudes are nearly independent of incident wave amplitudes for multiple-box systems with round inlet configurations. This implies that the energy dissipation associated with fluid viscosity and flow rotation plays an important role in the gap resonance for sharp inlet configurations; while it is insignificant for round inlet configurations.
Fluid resonance within narrow gaps in multiple-box systems with sharp and round inlet configurations are investigated by using the potential flow and viscous fluid flow models in the OpenFOAM® package. Evident discrepancy between two numerical models can be observed for sharp inlet configurations. In addition to the dramatical decrease of resonant amplitude in narrow gaps, some peak values at the higher resonant frequencies predicted by the potential flow model even disappear in the viscous fluid flow results. The decreased normalized resonant amplitudes with the increase of incident wave amplitude can be observed for sharp inlet configurations. However, the hydrodynamic behaviors of multiple-box system with round inlet configurations between potential flow and viscous fluid flow models are quite similar with each other. The normalized resonant amplitudes are nearly independent of incident wave amplitudes for multiple-box systems with round inlet configurations. This implies that the energy dissipation associated with fluid viscosity and flow rotation plays an important role in the gap resonance for sharp inlet configurations; while it is insignificant for round inlet configurations.
2023, 37(5): 863-875.
doi: 10.1007/s13344-023-0072-9
Abstract:
The application of the wellhead suction anchor in the second production test of natural gas hydrates (NGHs) in the South China Sea (SCS) was met with success. This design incorporates a central conductor guide pipe, which distinguishes it from traditional suction foundations. However, this addition resulted in a relatively high penetration resistance and a shallower penetration depth at the self-weight penetration stage. To mitigate this issue, the current study proposes an optimized design where the end of the suction foundation is sharpened. The installation characteristics of the traditional suction foundation and new suction foundation during self-weight penetration into sand are studied through laboratory tests and theoretical analysis. The flat and sharpened bottom shapes are considered in the traditional and new suction models. The effects of the initial penetration velocity on the initial penetration depth and soil plug and impact cavity characteristics are systematically studied. The results show that the self-weight penetration depth of the foundation with a sharpened bottom is 44.5% deeper than that of the foundation with a flat bottom. There are cavities around the foundation at the self-weight penetration stage, and the penetration depth is overestimated by 15%−30%. Finally, a model for predicting the penetration depth of the new suction foundation is proposed.
The application of the wellhead suction anchor in the second production test of natural gas hydrates (NGHs) in the South China Sea (SCS) was met with success. This design incorporates a central conductor guide pipe, which distinguishes it from traditional suction foundations. However, this addition resulted in a relatively high penetration resistance and a shallower penetration depth at the self-weight penetration stage. To mitigate this issue, the current study proposes an optimized design where the end of the suction foundation is sharpened. The installation characteristics of the traditional suction foundation and new suction foundation during self-weight penetration into sand are studied through laboratory tests and theoretical analysis. The flat and sharpened bottom shapes are considered in the traditional and new suction models. The effects of the initial penetration velocity on the initial penetration depth and soil plug and impact cavity characteristics are systematically studied. The results show that the self-weight penetration depth of the foundation with a sharpened bottom is 44.5% deeper than that of the foundation with a flat bottom. There are cavities around the foundation at the self-weight penetration stage, and the penetration depth is overestimated by 15%−30%. Finally, a model for predicting the penetration depth of the new suction foundation is proposed.
2023, 37(5): 876-884.
doi: 10.1007/s13344-023-0073-8
Abstract:
To study the water absorption of hollow glass microspheres (HGMs) composite epoxy resin solid buoyancy materials in the marine environment and its effect on the mechanical properties, the water absorption was measured by immersing the material in distilled water for 36 days at ambient temperature and fitted to Fick’s second law. The strength of materials before and after water absorption were tested by uniaxial experiments, and the effects of the filling ratio and water absorption on the mechanical properties of the materials were analyzed and explained. Finally, the failure modes and mechanism of the hollow glass microspheres composite material were explicated from the microscopic level by scanning electron microscope (SEM). This research will help solve the problems of solid buoyancy materials in ocean engineering applications.
To study the water absorption of hollow glass microspheres (HGMs) composite epoxy resin solid buoyancy materials in the marine environment and its effect on the mechanical properties, the water absorption was measured by immersing the material in distilled water for 36 days at ambient temperature and fitted to Fick’s second law. The strength of materials before and after water absorption were tested by uniaxial experiments, and the effects of the filling ratio and water absorption on the mechanical properties of the materials were analyzed and explained. Finally, the failure modes and mechanism of the hollow glass microspheres composite material were explicated from the microscopic level by scanning electron microscope (SEM). This research will help solve the problems of solid buoyancy materials in ocean engineering applications.
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