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Table of Content

    28 November 2023, Volume 57 Issue 11 Previous Issue    Next Issue
    Naval Architecture, Ocean and Civil Engineering
    Simulation Study of Reentry Dynamics of a Deep-Water Drilling Riser System Based on Model Predictive Control
    ZHANG Chenyu, MENG Shuai
    2023, 57 (11):  1389-1399.  doi: 10.16183/j.cnki.jsjtu.2022.235
    Abstract ( 1419 )   HTML ( 30 )   PDF (2622KB) ( 257 )   Save

    A marine drilling riser at normal operation condition is required to disconnect the lower marine riser package (LMRP) and blow-out preventer (BOP) in case of severe weather. When the weather gets fine, it must reconnect the LMRP and the BOP. This process is called riser reentry. Marine drilling operations have been driven into extreme deep-waters characterized by severe weather which inevitably leads to a much higher incidence of disconnection. In addition, it requires to accomplish the reentry in a fast way owing to the capricious ocean environment. This study tries to develop a novel reentry control system based on model predictive control (MPC). First, the transverse governing equation of the hanging-off riser system with an end-mass is established based on the modified Hamilton’s principle. The optimization function and constraints in MPC are designed by use of the riser prediction model and the target location. A nonlinear disturbance observer is established for compensation of the model uncertainties and ocean environment disturbances. Finally, simulations are conducted after introducing the dynamic position system (DPS). The riser dynamics employing MPC are compared with that when adopting proportional-integral-derivative (PID) controller. It has found that the drilling riser system based on MPC has a higher response speed, which can complete the reentry process in a faster and more stable manner. It can handle the hydrodynamic force model uncertainties well and has a good robustness for current velocity disturbances. As the flexibility of the riser system is notably enhanced with the significant increase of aspect ratio, the higher-order mode of the flexible hanging-off riser can be triggered in the fast reentry process subjected to the excitations of the mother vessel and ocean environment.

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    Analysis of Fluid-Structure Coupling Energy Transfer Characteristics Slender Structure with Variable Cross-Section at Low Reynolds Number
    DENG Xiubing, YU Yuemin, PANG Xiyuan
    2023, 57 (11):  1400-1409.  doi: 10.16183/j.cnki.jsjtu.2022.133
    Abstract ( 1706 )   HTML ( 14 )   PDF (18587KB) ( 221 )   Save

    The wavy deformed cross-section cylindrical structure has excellent properties of drag reduction in fluid flow, but the flow-induced vibration characteristics of flexible structure with such variable cross-section are still unclear. In this paper, based on the high-performance spectral element method, a fluid-structure coupled mechanistic model and a numerical algorithm for slender structures are established. The wake characteristics, structural dynamic responses, energy transfers, and spanwise variations of vortex shedding frequencies are discussed. The numerical simulation results show that slender structure with the wavy-deformed cross-section can greatly suppress the vortex-induced vibration response at an appropriate cross-section disturbance wave height, and the special vortex structure formed on both sides of the wavy-shaped slender structure can stabilize the flow around the shear layer and elongate the vortex formation length, thereby reducing the fluid-structure coupling effect between the wake structure and the slender structure, and suppressing the vortex-induced vibration response.

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    Dynamic Characteristics of Two-Dimensional Structures Slamming Under Free Fall Condition
    SUN Zhe, SUI Xupeng, KOROBKIN Alexander, DENG Yanzeng, ZHANG Guiyong, ZONG Zhi, JIANG Yichen
    2023, 57 (11):  1410-1420.  doi: 10.16183/j.cnki.jsjtu.2022.189
    Abstract ( 935 )   HTML ( 22 )   PDF (1402KB) ( 310 )   Save

    The slamming process of two-dimensional structures under free fall condition with arbitrary symmetrical shapes is investigated by combining various analytical models for slamming and the precise integration method in the time domain. By closely analyzing the mathematical expression of analytical models, the total slamming force acting on the body can be decomposed into two terms which are dependent on the velocity and the acceleration respectively. The developed model proposed in this paper is validated against the results from experiments and other numerical methods. Moreover, it is found that if the gravity of body is ignored, which is a reasonable assumption for situations such as structures with light weight or large entry velocity, the maximum acceleration (or the peak slamming force) for a free fall body will always occur at the certain penetration depth for a particular shape and mass, regardless of the initial slamming velocity.

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    Optimization Design of New Bionic Propeller
    WU Chunxiao, LU Yu, LIU Shewen, GU Zhuhao, SHAO Siyu, SHAO Wu, LI Chuang
    2023, 57 (11):  1421-1431.  doi: 10.16183/j.cnki.jsjtu.2022.174
    Abstract ( 1940 )   HTML ( 30 )   PDF (10709KB) ( 504 )   Save

    A novel method for optimal design of hydrodynamic performance of bionic propeller with a deformable leading edge is proposed. Based on the bionics principle and method of parameterized modeling, the fore-fin concave-convex structure of humpback whales is applied to the propeller leading edge, the leading edge in the propeller to meet flow region according to the exponential decay curve and the standard sine curve smooth leading edge for similar humpback fins protuberant structure of concave and convex deformation, and the leading edge of concave and convex bionic propeller. The hydrodynamic performance, the cavitation performance, and the noise performance of the exponential decay bionic propeller and the sinusoidal function bionic propeller were simulated respectively. The propeller with a better performance is selected, and the simulation based design (SBD) technology is introduced into the optimization design of the new bionic propeller. The parameters controlling the shape of the exponential attenuation curve of the guide edge deformation are taken as optimization design variables, the torque of the parent propeller is taken as the constraint condition, the open water efficiency is selected as the objective function, and the optimization algorithm of Sobol and T-Search is adopted. A bionic propeller optimization system based on the exponential decay curve is constructed. The results show that the application of the concave and convex structure of the humpback whale fore-fin to the guide edge of the propeller improves the cavitation performance and noise performance of the propeller, but the improvement of the open water performance of the propeller is not particularly significant. It is verified that the hydrodynamic performance optimization design method of the bionic propeller established in this paper is effective and reliable, which provides a certain theoretical basis and technical guidance for the performance numerical calculation and configuration optimization design of the bionic propeller.

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    Wake Field Characteristics of Non-Ducted and Ducted Propellers in Large-Angle Oblique Flow
    ZHANG Qin, WANG Xinyu, WANG Zhicheng, WANG Tianyuan
    2023, 57 (11):  1432-1441.  doi: 10.16183/j.cnki.jsjtu.2022.159
    Abstract ( 1721 )   HTML ( 16 )   PDF (18498KB) ( 239 )   Save

    In order to explore the wake characteristics of non-ducted and ducted propellers in oblique inflow with a large drift angle, based on the delayed detached eddy simulation, a numerical simulation of non-ducted and ducted propellers in oblique inflow is conducted with an advance coefficient (J=0.4) and a large drift angle (β=45°, 60°). It is found that the deflection degree of the non-ducted propeller wake is higher than that of the ducted propeller. However, the overall distribution area of the wake vortex behind the ducted propeller is kinked. The wake field in the oblique flow shows its complexity, and the evolution process of vortices on the windward side differs from that on the leeward side. The above characteristic of the non-ducted propeller is more prominent. At the same time, the leading edge of the nozzle on the leeward side will produce local shedding vortices and transmit to the downstream due to flow separation. Part of the kinetic energy of the ducted propeller is converted into the nozzle thrust, which makes the turbulence kinetic energy of the wake lower than that of the non-ducted propeller. This phenomenon is more evident with the increase in the drift angle. Compared with the non-ducted propeller, the ducted propeller can maintain a better handling stability in large-angle oblique flow. This paper analyzes the influence of large-angle oblique inflow on the non-ducted and ducted propellers from the perspective of wake field characteristics and explores the theoretical basis for the ducted propeller to maintain a better handling stability in oblique flow.

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    Experimental Investigation of Dynamic Response of Pile-Supported Wharf in Liquefiable Ground Under Wave Action
    BI Jianwei, SU Lei, XIE Libo, ZHANG Yu, LING Xianzhang
    2023, 57 (11):  1442-1454.  doi: 10.16183/j.cnki.jsjtu.2022.163
    Abstract ( 1653 )   HTML ( 12 )   PDF (8259KB) ( 311 )   Save

    Pile-supported wharf (PSW) is widely used in the deep-water port engineering construction, most of which are located in liquefiable ground. The effect of wave action on the working performance of PSW in liquefiable ground cannot be ignored, but few studies have been reported. This study performs the wave flume test of PSW in liquefiable ground considering the soil-structure-wave interaction. This test really reproduces the operating condition of PSW, and explores the internal response difference of wharf structure under wave. The influence of wave height on dynamic response of the PSW system is discussed systematically. The result shows that the acceleration and displacement of the PSW deck gradually increase first and finally remain relatively stable with the increase of wave action. The hydrodynamic pressure and deformation of each pile in pile group are obviously different, and the response variation is related to the pile position. The pore pressure of the soil layer in the free field and around the pile decreases with the increase of depth, and the existence of the pile group can reduce the pore pressure in the soil layer around the pile, and increase the acceleration of the soil layer. The effect of wave height on the soil layer decreases with the increase of depth. The above results can provide reference for the similar PSW test under wave and the support for the design and wave protection of PSW.

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    New Type Power System and the Integrated Energy
    Robust Optimization of Power Grid Investment Decision-Making Considering Regional Development Stage Uncertainties
    HUANG Wandi, ZHANG Shenxi, CHENG Haozhong, CHEN Dan, ZHAI Xiaomeng, WU Shuang
    2023, 57 (11):  1455-1464.  doi: 10.16183/j.cnki.jsjtu.2022.053
    Abstract ( 1616 )   HTML ( 18 )   PDF (2782KB) ( 138 )   Save

    Aimed at the problem of uncertainties in the regional development stage and the difficulties in quantifying regional investment demand in different development stages, a robust optimization method for power grid investment decision-making considering regional development stage uncertainties is proposed to promise the matching degree between power grid investment decisions and development needs, and to improve the ability of decision-making results to deal with portfolio risks and uncertainties in regional development stage. First, investment risk constraints are constructed based on the modern portfolio theory. Then, a box uncertainty set is used to characterize uncertainties in regional development stage, and a robust optimization model for power grid investment decision-making considering uncertainties in development stage is established. In the optimization model, the outer minimization problem is used to solve the uncertain variables in regional development stage in the worst scenario, while inner maximization problem is used to obtain the decision-making plan that can maximize investment return in the worst scenario. Furthermore, according to the strong duality theory, the double-layer optimization model is transformed into a single-layer model that can be solved directly, and the big-M method is used to solve the model proposed. Finally, an actual example of 13 cities in an eastern coastal province verifies the applicability and effectiveness of the power grid investment decision-making model.

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    An Improved NLC and Capacitor Voltage Control Method for Medium-/Low-Voltage MMCs
    ZHANG Wei, HAN Junfei, ZHONG Ming, WANG Yuqiang
    2023, 57 (11):  1465-1476.  doi: 10.16183/j.cnki.jsjtu.2022.172
    Abstract ( 1587 )   HTML ( 13 )   PDF (2806KB) ( 196 )   Save

    The modular multilevel converter (MMC) suffers from low output level and high harmonic distortion in medium-/low-voltage applications such as direct current (DC) distribution networks. In addition, the capacitor voltage of MMC is coupled with DC bus voltage in the traditional modulation method, leading to large fluctuations of capacitor voltages and deviation from the rated value under DC bus voltage margin. In order to solve the problems above, this paper proposes an improved nearest level control method, which can increase the output level of medium-/low-voltage MMCs by introducing a step wave correction. Based on the proposed modulation method, a capacitor voltage feedback control is thus proposed to limit the range of capacitor voltage fluctuations and improve equipment safety. The effectiveness of the proposed method is verified by MATLAB/Simulink simulation and real-time digital simulation system hardware-in-the-loop test.

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    Stepwise Inertial Intelligent Control of Wind Power for Frequency Regulation Based on Stacked Denoising Autoencoder and Deep Neural Network
    WANG Yalun, ZHOU Tao, CHEN Zhong, WANG Yi, QUAN Hao
    2023, 57 (11):  1477-1491.  doi: 10.16183/j.cnki.jsjtu.2022.157
    Abstract ( 1734 )   HTML ( 19 )   PDF (10551KB) ( 246 )   Save

    Stepwise inertial control (SIC) provides a step-increase of power after load fluctuation, which can effectively prevent system frequency decline and ensure the safety of grid frequency. However, in the power recovery stage, secondary frequency drop (SFD) is easy to occur. Therefore, it is necessary to optimize SIC to obtain a better frequency regulation effect. The traditional method has the disadvantages of high calculation dimension and long consuming time, which is difficult to meet the requirements of providing the optimal control effect in different scenarios. In order to realize the optimal stepwise inertial fast control of wind power frequency regulation in load disturbance events, this paper introduces the deep learning algorithm and proposes a stepwise inertial intelligent control of wind power for frequency regulation based on stacked denoising autoencoder(SDAE) and deep neural network(DNN). First, sparrow search algorithm (SSA) is used to obtain the optimal parameters, and SDAE is used to extract the data features efficiently. Then, DNN is used to learn the data features, and the accelerated adaptive moment estimation is introduced to optimize the network parameters to improve the global optimal parameters of the network. Finally, the stepwise inertial online control of wind power frequency regulation after disturbance event is realized according to SDAE-DNN. The simulation analysis is conducted for a single wind turbine and a wind farm in the IEEE 30-bus test system. Compared with the results obtained by the traditional method, shallow BP neural network and original DNN network, it is found that the proposed network structure has a better prediction accuracy and generalization ability, and the proposed method can achieve a great effect of stepwise inertia frequency regulation.

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    Optimization of Wind Turbine Vortex Generator Based on Back Propagation Neural Network
    XIA Yunsong, TAN Jianfeng, HAN Shui, GAO Jin’e
    2023, 57 (11):  1492-1500.  doi: 10.16183/j.cnki.jsjtu.2022.169
    Abstract ( 1644 )   HTML ( 15 )   PDF (9995KB) ( 225 )   Save

    The optimal Latin hypercube experimental design method is used to refine the vortex generator parameters, determine the test scheme, simulate and calculate the thrust and torque of the wind turbine, and obtain the experimental data. Based on the back propagation (BP) neural network, the aerodynamic performance model of the wind turbine vortex generator optimized by genetic algorithm is constructed. The reliability of the aerodynamic performance model is verified by calculating the error and root mean square of the predicted and simulated values of the aerodynamic performance model. Coupling the fish swarm algorithm and the aerodynamic performance model of the wind turbine vortex generator, an optimization method of the wind turbine vortex generator is established, and the height, length, and installation angle of the vortex generator are solved iteratively to realize the optimization of the vortex generator. The results show that compared with the original vortex generator scheme, the flow separation of the wind turbine blade section optimized by the vortex generator is effectively restrained and delayed, the surface fluid separation phenomenon is improved, the power of the wind turbine is increased by 1.711%, and the thrust of the wind turbine is decreased by 0.875%.

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    Multi-Objective Optimization of Electric Vehicle Spare Capacity Based on User Wishes
    SHAO Ping, YANG Zhile, LI Kang, ZHU Xiaodong
    2023, 57 (11):  1501-1511.  doi: 10.16183/j.cnki.jsjtu.2022.131
    Abstract ( 1006 )   HTML ( 14 )   PDF (5565KB) ( 187 )   Save

    Due to the considerable number and the characteristics of energy storage, it is possible for electric vehicles (EVs) to participate in the operation and regulation of power system to provide reserve service. In view of this, a multi-objective optimal scheduling model is established based on the wishes of electric vehicle users, with the objectives of the economic benefits of electricity collectors, microgrid power fluctuations and user satisfaction. Considering the uncertainty of load demand, the optimal scheduling analysis of multi-time scale scenes with the day-ahead time scale and the intra-day real-time correction time scale is conducted. The mainstream multi-objective intelligent optimization algorithm NSGA-III algorithm is adopted in the solution method, and the NSGA-II and MOEA/D algorithms are used for comparison. The optimal dispatching scheme is selected through comparative experiments and scenarios where EVs provide spare capacity are analyzed. The simulation results verify the feasibility and effectiveness of the proposed model.

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    Mechanical Engineering
    Fault Diagnosis of Rolling Bearing with Roller Spalling Based on Two-Step Transfer Learning on Unbalanced Dataset
    GUO Junfeng, WANG Miaosheng, WANG Zhiming
    2023, 57 (11):  1512-1521.  doi: 10.16183/j.cnki.jsjtu.2022.008
    Abstract ( 222 )   HTML ( 16 )   PDF (5567KB) ( 159 )   Save

    Under operating conditions, bearings have a substantial service life with short failure time periods, which leads to unbalanced dataset and greatly affects the accuracy of deep learning model fault diagnosis. To address this problem, a fault diagnosis method of rolling bearing unbalanced dataset based on two-step transfer learning is proposed in this paper. First, a small amount of data in the source and target domains is used to generate the transition dataset by conditional gradient penalized generative adversarial network (CWGAN-GP). Then, the constructed convolutional neural network model is migrated twice between the source domain dataset, the transition dataset, and the target domain dataset. Finally, a small amount of data from the target domain is used to fine-tune the transferred model to obtain the final fault diagnosis model. The experimental results show that the method has a good diagnostic recognition effect on rolling bearing spalling class faults with unbalanced dataset under different working conditions.

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    Sequential Preventive Maintenance Strategy Considering Difference of Maintenance Effect
    LI Xinlong, RAN Yan, ZHANG Genbao, HE Yan
    2023, 57 (11):  1522-1530.  doi: 10.16183/j.cnki.jsjtu.2022.023
    Abstract ( 221 )   HTML ( 9 )   PDF (996KB) ( 120 )   Save

    Proper preventive maintenance can improve equipment reliability and prolong equipment life to a certain extent. Aimed at the problems that the decision granularity of the current preventive maintenance strategy is too large and the maintenance effect of preventive maintenance on different types of failures is rarely considered, the imperfect sequential preventive maintenance strategy of the meta-action unit is studied. Taking the meta-action unit as the research carrier, the failures are divided into damage failure and essential fatigue failure according to the difference of preventive maintenance effect. Based on the generalized geometric process, a sequential preventive maintenance optimization model is established. The research shows that the overall maintenance cost rate will be underestimated without considering the differences in preventive maintenance effectiveness. At the same time, various types of maintenance costs, the proportion factor of damage-type failures and intrinsic fatigue-type failures, and the preventive maintenance effect parameter have a significant influence on the formulation of maintenance strategy. This research has a certain guiding role in formulating the sequential preventive maintenance strategy of meta-action unit and reducing its maintenance cost.

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