Table of Content

28 June 2023, Volume 57 Issue 6 Previous Issue    Next Issue

Naval Architecture, Ocean and Civil Engineering

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Review of Single Blade Installation and Docking Technology of Large Offshore Wind Turbine XIE Sihong, ZHAO Yongsheng, XU Yiqing, HE Yanping, HAN Zhaolong, XU Yuwang 2023, 57 (6):  631-641.  doi: 10.16183/j.cnki.jsjtu.2022.237 Abstract ( 399 )   HTML ( 356 )   PDF (14702KB) ( 574 )   Save In recent years, offshore wind turbines show the trend of large-scale development, the installation area of which has been expanding to the deep and far-reaching ocean. However, due to the harsh environmental conditions in the far-reaching ocean region, the traditional rotor-lifting method is facing many limitations. In contrast, the single blade installation technology has significant advantages in installation efficiency and safety, and has gradually become a new research hotspot. Based on the characteristics and difficulties of the offshore single blade installation technology, this paper investigates and summarizes the lifting equipment and key technologies involved in single blade installation section, including blade yokes, the single blade installation dynamic simulation model, and the active control technology. Among them, the research and development of novel single blade installation equipment and methods with active control technology are essential for large-scale offshore wind turbine installation in the far-reaching ocean region. Additionally, based on the development trend and prospect of offshore blade installation and the docking technology, it introduces some technical ideas, including single blade yoke with dynamic positioning function, and double hoop blade vertical installation auxiliary device, which are expected to solve the installation problem of large-scale offshore wind turbines. Figures and Tables | References | Related Articles | Metrics

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Aerodynamic Performance Optimization of MW-Level Large Vertical Axis Wind Turbine with Trailing Edge Flaps CHEN Hao, DAI Mengyi, HAN Zhaolong, ZHOU Dai, BAO Yan, TU Jiahuang 2023, 57 (6):  642-652.  doi: 10.16183/j.cnki.jsjtu.2021.488 Abstract ( 202 )   HTML ( 312 )   PDF (9287KB) ( 118 )   Save Low power efficiency is a critical factor that restricts the engineering application of the vertical axis wind turbine (VAWT). In order to improve the efficiency of VAWT and reduce aerodynamic load, an improved aerodynamic performance optimization model for a large VAWT with trailing edge flaps at a medium tip speed ratio (TSR=2.65) is proposed. A numerical simulation is conducted using the SST k-ω turbulence model. The results indicate that compared with the base model, the power coefficient of the model under the synergic motion of pitch and flap can be increased by 12.2%. In addition, the synergic motion of pitch and flap can significantly reduce the thrust and lateral force on the VAWT, which are reduced by 12.4% and 7.5% respectively compared with the base model. The load fluctuation of thrust and lateral force is also significantly lower than that of the base model, which is helpful to reduce the fatigue load on wind turbine. This model is expected to be applied to MW-level VAWT. Figures and Tables | References | Related Articles | Metrics

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Experimental Study of Hydrodynamic Responses of Cylinder Floating Production and Storage Offloading in Short-Crested Waves LI Jun, PENG Tao, ZHANG Jianhong, LU Wenyue 2023, 57 (6):  653-658.  doi: 10.16183/j.cnki.jsjtu.2022.239 Abstract ( 139 )   HTML ( 310 )   PDF (5584KB) ( 164 )   Save An experimental investigation is conducted to study the hydrodynamic responses of cylinder floating production storage and offloading (FPSO) subjected to heading short-crested waves of different spreading parameters. The motion response and mooring dynamics of cylinder FPSO are analyzed and the results are compared with those from the long-crested waves. The simulation experiment shows that the short-crested waves induce smaller surge motions and mooring tensions, but generate bigger sways and roll motions compared with those of the long-crested waves. There are statistically significant differences in hydrodynamics of cylinder FPSO between short-crested and long-crested waves. The research results provide important references for further study of short-crested waves and their interaction with ocean engineering structures. Figures and Tables | References | Related Articles | Metrics

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Application of Improved LSTM Neural Network in Time-Series Prediction of Extreme Short-Term Wave SHANG Fancheng, LI Chuanqing, ZHAN Ke, ZHU Renchuan 2023, 57 (6):  659-665.  doi: 10.16183/j.cnki.jsjtu.2021.438 Abstract ( 305 )   HTML ( 26 )   PDF (2062KB) ( 244 )   Save Efficient and accurate extreme short-term prediction is of great significance for the safety of ship and marine structures in actual sea waves. Due to the stochastic of actual sea waves, short-term prediction always uses time series analysis. The neural networks, particularly long short-term memory (LSTM) neural networks, have received increasing attention for their powerful forecasting capability in time series analysis. Based on this, an improved form of LSTM combining generative adversarial ideas is proposed, in which the frequency domain characteristics are embedded in the neural network to achieve coupled time-frequency domain information forecasting. The experimental test shows that the forecasting accuracy of this method is better than the results of traditional time series analysis methods and the LSTM neural network, and it is suitable for extreme short-term time series prediction for better ship maneuvering. Figures and Tables | References | Related Articles | Metrics

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Unsteady Evolution Law and Evaluation Index of Shallow Sea Wind-Wave-Current-Seabed Coupling Field CHEN Jing, KE Shitang, LI Wenjie, ZHU Tingrui, YUN Yiwen, REN Hehe 2023, 57 (6):  666-679.  doi: 10.16183/j.cnki.jsjtu.2022.065 Abstract ( 185 )   HTML ( 16 )   PDF (20403KB) ( 182 )   Save There is a strong real-time coupling between seabed topography and wave field, current field and wind field in shallow water area. The existing analysis model cannot directly consider the influence factors of seabed, and it is more difficult to explain the unsteady evolution mechanism of the coupling field between typical seabed topography and wave, shear flow and gradient wind. Based on the secondary development of STAR-CCM+platform, the shallow sea wind-wave-current numerical pool is constructed under four typical seabed landform conditions: seabed plain, seabed slope, trough, and flat landform. The multi-layer particle velocity coupling method is proposed and the multi-layer wind-wave-current coupling model is established. The wind-wave-current decoupling is realized at the initial time. The temporal and spatial evolution laws of wave field, current field, and wind field in different seabed topographies are compared and analyzed. The principal component analysis method is introduced to evaluate the unsteady effect of wind-wave-current in various typical seabed topographies, and the unsteady evaluation index of the whole life cycle of the wind-wave-current-seabed coupling field is established. The results show that the multi-layer wind-wave-current coupling model can more truly reflect the influence of vertical wind speed and uneven velocity distribution on wave field. The seabed topography can lead to a multi-stage time-history distribution of wave field in the evolution process. The flat topography, submarine slope, and trough conditions are divided into wave surface surge, attenuation, and stability stages. The submarine plain conditions are divided into external breaking wave, internal breaking wave, and climbing stage. The evolution of the current field presents a multi-stage spatial distribution, and the seabed leads to the formation of multi-vortex accumulation or multi-vortex coexistence in the current field. The coupling evolution of wind-wave-current-seabed has an amplification effect on the wind profile index, and positive relationship between seabed height and wind profile coefficient. The end-stage unsteady evaluation indices of flat landform, submarine plain, submarine slope, and trough are 0.268, 4.612, 0.672, and 0.926, respectively. Figures and Tables | References | Related Articles | Metrics

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Collision Simulation Method and Protection Mechanism of Composite Fenders for Ships LI Muzhi, BAO Wenqian, WANG Xiucheng, ZHANG Yiming, YUAN Yuchao, TANG Wenyong 2023, 57 (6):  680-689.  doi: 10.16183/j.cnki.jsjtu.2022.075 Abstract ( 190 )   HTML ( 21 )   PDF (13216KB) ( 195 )   Save Fenders play an important protective role in ship collisions, but there are few studies related to the collision simulation methods and the protection mechanism of composite fenders. First, aimed at the new composite fender design scheme proposed in this paper and based on the material properties exhibited in the test, low-density foam and hyperelastic models are selected to simulate the inner foam and outer polyurethane of the fender, respectively. Subsequently, for the hull-fender-quay collision problem, a multi-body geometry model is established and a collision simulation method is formed to analyze the fender protection mechanism from the perspective of energy conversion. It is proved that the composite material has a better protection effect on the hull structure than the rubber fender. Finally, the inner foam strength, hull stiffness, outer polyurethane thickness, and tensile strength of composite materials are varied to analyze the protection mechanism of composite materials respectively. The results show that the relative stiffness of the fender and the structure is the main factor affecting the protection performance. The inner foam of the composite fender is the main energy-absorbing structure, absorbing the kinetic energy of the hull through compression deformation to reduce the response of the structure, while the outer polyurethane mainly plays the role of protecting the core. Figures and Tables | References | Related Articles | Metrics

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Stability Analysis of Shield Cutter Replacement Ground Reinforced with Steel Pipe Pile-Grouting DAI Zhiheng, ZHANG Mengxi, WEI Hui, GU Jie, ZHANG Xiaoqing 2023, 57 (6):  690-699.  doi: 10.16183/j.cnki.jsjtu.2021.032 Abstract ( 139 )   HTML ( 14 )   PDF (18433KB) ( 124 )   Save Based on the Foshan-Dongguan Intercity Line Changlong Tunnel Project, indoor tests and numerical simulations were conducted to study the instability and progressive failure process of the cutter replacement ground at atmospheric pressure. The fast Lagrangian analysis of continua method was adopted to establish the numerical model. The safety factor of the cutter replacement ground was analyzed, and the effect of the steel pipe pile-grouting method on the control effect of release and displacement was studied. The results show that the excavation face becomes unstable at atmospheric pressure, which causes soil loss and earth pressure release. As the cutter head moves backward, a large-scale vertical displacement of cutter replacement ground is gradually induced, and finally goes through to the surface. With the steel pipe pile-grouting reinforcement, the safety factor of the cutter replacement ground is significantly improved, and the ground stress release and displacement is effectively controlled. Compared with the grouting reinforcement, the steel pipe pile-grouting reinforcement has the advantages of short construction period and less pollution. Moreover, the steel pipe pile could be recycled without affecting the subsequent use of the soil, which provides a new ground reinforcement idea for the project. Figures and Tables | References | Related Articles | Metrics

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Vertical Bearing Characteristics of Mat Foundation on Horizontal and Sloping Clay Seabed YAN Yuanzhong, ZHANG Qi, YE Guanlin, SUN Bo, LIU Guojun 2023, 57 (6):  700-708.  doi: 10.16183/j.cnki.jsjtu.2021.459 Abstract ( 181 )   HTML ( 11 )   PDF (14512KB) ( 140 )   Save Accurate evaluation of the vertical bearing capacity of the mat foundation on the clay seabed is of great significance for the safe operation of the mat-supported jack-up platform in the marine environment. Combining the centrifuge test and the coupled Eulerian-Lagrangin (CEL) large deformation numerical calculation method, the vertical bearing characteristics of mat foundation on horizontal and sloping clay seabed were studied. First, the distribution law of undrained shear strength of soil along the depth was obtained through the T-bar penetration test. Then, the vertical bearing characteristics of two kinds of bottom mat foundations on soft clay seabed were tested. Finally, the vertical bearing characteristics of the mat foundation were discussed in combination with the numerical method of CEL large deformation, and the bearing capacity and soil displacement changes of the foundation on different inclination seabed were analyzed. The results show that the foundation load displacement curve has no obvious peak value, and the bearing capacity of the square foundation is slightly higher than that of the rectangular foundation. The development law of soil excess pore pressure is basically consistent with the change law of bearing capacity in the process of foundation entering the sea bead, and most of the vertical stress is borne by the excess pore pressure. The foundation bearing capacity gradually decreases as the slope of the seabed increases, and the soil below the foundation tends to slip in the direction of the slope angle, which may lead to slip damage of the seabed. Therefore, operation in the seabed area with a large slope should be avoided in actual practice. Figures and Tables | References | Related Articles | Metrics

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Undrained Solution for Spherical Cavity Expansion in Structured Clay and Its Application in CPT ZHANG Yaguo, XIAO Shuxiong, ZHAI Zhanghui, LI Tonglu 2023, 57 (6):  709-718.  doi: 10.16183/j.cnki.jsjtu.2021.330 Abstract ( 153 )   HTML ( 11 )   PDF (2513KB) ( 147 )   Save The cavity expansion theory is widely used in the analysis and prediction of cone resistance and lateral displacements in cone penetration test (CPT) and pile installation. Nowadays, the existing theoretical solutions for cavity expansion in structured clay cannot consider the influences of structure degradation on the mechanical behaviors of soil during the expanding process, which limits its applications in practical engineering to some extent. Therefore, taking the penetration of cone or pile tip as a spherical cavity expansion process in soil, based on the structured Cam-Clay (SCC) model and the large strain theory in plastic zone, the undrained spherical cavity expansion problem could be attributed to a boundary value problem of a system of ordinary differential equations about effective stress components. The equations then could be solved with stresses on the elastic-plastic boundary serving as boundary conditions. The results show that, with strengthening of soil structure, the plastic and critical state zones narrow, the internal cavity stresses increased, and the softening behavior and dilatancy of over-consolidated soil become more significant. For structured clay with the same initial stresses, the effective stress components adjacent to cavity wall overlap with that of the corresponding reconstituted soil, which indicates that the degradation of soil structure occurs during the soil-disruption accompanied expansion process. Finally, the internal cavity stresses derived from the proposed solution were used for theoretical calculation of cone resistance and pore pressure in CPT. A comparison of the existing solution with the results calculated indicates that the results obtained with consideration of soil structure are closer to the measured values. Figures and Tables | References | Related Articles | Metrics

Aeronautics and Astronautics

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Improvement and Numerical Verification of Weighting Strategy for High Precision WCNS Scheme YANG Qiang, LI Weipeng 2023, 57 (6):  719-727.  doi: 10.16183/j.cnki.jsjtu.2022.014 Abstract ( 262 )   HTML ( 19 )   PDF (3360KB) ( 231 )   Save In order to reveal the complex flow mechanism, a series of high-order precision schemes have been proposed at home and abroad, of which, the weighted compact nonlinear scheme (WCNS) has a good shock capture ability and has been widely used in the numerical simulation of complex flows. However, it has insufficient resolution and large dissipation in the simulation of small-scale flows. In the framework of the WCNS, by using the weighting strategy of the targeted essentially non-oscillatory (TENO) scheme for reference, this paper introduces the new methods of discontinuity detection and template weighting into the construction of the WCNS scheme, and develops a WCNS7-T scheme with a 7-order accuracy. Example tests are conducted through one-dimensional shock tube problem and two-dimensional Riemann problem. By comparing with the traditional WCNS7-Z scheme, the improved performance of the new scheme is verified. The numerical experiments show that the WCNS7-T scheme can better suppress the numerical oscillation near the discontinuity, improve the resolution and shock capture ability, and further reduce the dissipation. Figures and Tables | References | Related Articles | Metrics

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Improved Thermal Network Method for Fuel Transient Temperature Prediction of High-Speed Aircrafts CHENG Xianda, ZHENG Haoran, YANG Xuesen, DONG Wei 2023, 57 (6):  728-738.  doi: 10.16183/j.cnki.jsjtu.2021.387 Abstract ( 187 )   HTML ( 12 )   PDF (11336KB) ( 316 )   Save The low simulation efficiency of three-dimensional transient calculation makes it difficult to be applied in predicting fuel temperature during the entire fuel consumption process. In order to satisfy the requirements of fuel temperature field calculation in the rapid iterative fuel system design process, a novel efficient and accurate improved thermal network method was proposed. The mixing coefficient was introduced to the heat conduction equation to represent the heat convection inside the fuel, and the heat transfer caused by the mass transfer term was added to the heat balance equation to represent the problem of overall fuel flow. Based on the improved thermal network method, the transient thermal analysis model of the high-speed aircraft fuel tank was constructed. The results show that under different thermal boundary conditions and tank geometries, the temperature deviation between the thermal network method and the computational fluid dynamics(CFD) method is less than 5%, and the calculation efficiency of the thermal network method is much higher, which can greatly improve the computational efficiency. By combining CFD calculation with the improved thermal network method, a novel fuel transient temperature prediction method is provided for the design of the high-speed aircraft fuel storage system. Figures and Tables | References | Related Articles | Metrics

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Effect of Corner Roundedness on Capillary Flow of Liquid Propellants in Microgravity YANG Enbo, JIN Yupeng, YANG Guang, HUANG Yonghua, WANG Tianxiang, LEI Gang, WU Jingyi 2023, 57 (6):  739-746.  doi: 10.16183/j.cnki.jsjtu.2021.504 Abstract ( 177 )   HTML ( 12 )   PDF (3571KB) ( 158 )   Save The theory of interior corner flow driven by surface tension provides an important support for design of liquid management devices in space. The flow rate, velocity, and liquid position are important factors to determine liquid management efficiency. In practice, due to machining precision or aiming to enhance the mechanical strength, the interior corner is often imperfect with a certain degree of roundedness. In this paper, the influence of corner roundedness on liquid flow characteristics is quantitatively analyzed by combining theoretical and experimental analysis. The results show that with a fixed corner roundedness, the height of liquid is always proportional to the square root of time. The velocity of capillary flow also decreases with the increase of corner roundedness. The present theoretical model is validated by the microgravity experiments based on magnetic compensation. Furthermore, the model is applied to simulate the capillary flow of liquid hydrogen and liquid oxygen. The variations of flow rate under different conditions are obtained, which provides important basic data for the design of liquid management devices for cryogenic propellant. Figures and Tables | References | Related Articles | Metrics

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Influence of Aerodynamic Characteristics of Airfoil Forward Flight Considering Step-Type Ground XU Xiaogang, ZHANG Yang, CHANG Min, CHEN Gang 2023, 57 (6):  747-756.  doi: 10.16183/j.cnki.jsjtu.2021.380 Abstract ( 168 )   HTML ( 14 )   PDF (6339KB) ( 227 )   Save The aerodynamic influence of ground effects during forward flight is difficult to ignore, especially when there is a sudden change in the ground structure. The aerodynamic performance of the airfoil during forward flight is investigated using the NACA4412 airfoil, the correlation between two factors, i.e., height and angle of attack, and the aerodynamic performance of the airfoil are analyzed. The results show that under the effect of step-type ground, the wing forward flight causes a steep drop in lift-to-drag ratio when the ground effect is absent, and there is a linear relationship with the height above the ground. The angle of attack from the ground has an inverse relationship with the sudden change in aerodynamic performance, i.e., the airfoil needs to maintain a large angle of attack when it leaves the ground in order to reduce the steep change in aerodynamic performance. The take-off and landing process of a shipboard aircraft is typical of a step-type ground. This paper provides a reference for the aerodynamic design of an airfoil under the influence of ground effects. Figures and Tables | References | Related Articles | Metrics