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Investigations on Fluid Resonance Within A Narrow Gap Formed by Two Fixed Bodies with Varying Breadth Ratios

China ocean engineering 2023年第6期37卷 962-974页

作者： GONG Shu-kai GAO Jun-liang MAO Hong-fei School of naval architecture and ocean engineering Jiangsu University of Science and TechnologyZhenjiang 212100China State Key Laboratory of Hydraulic engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300350China college of ocean engineering and Energy Guangdong Ocean UniversityZhanjiang 524000China Guangdong Provincial Key Laboratory of Intelligent Equipment for South China Sea Marine Ranching Guangdong Ocean UniversityZhanjiang 524088China

The resonant motion of the fluid inside a narrow gap between two fixed boxes induced by incident regular waves with various wave heights is investigated by adopting a two-dimensional numerical wave flume based on an opensourced CFD package,OpenFOAM.The two boxes have identical draft and height,but the upstream box has a variable breadth.This article focuses on the influences of the breadth ratio,defined as the ratio of the breadth of the upstream box to that of the downstream box,on the following three aspects of hydrodynamic characteristics of gap resonance:(1)the wave height amplifications inside the gap,and in front and at the rear of the structure system,(2)the reflection,transmission,and energy loss coefficients of the structure system,and(3)the response and damping time of the fluid resonance.It is found that the fluid resonant frequency,the amplification factor of the resonant wave height inside the gap and the maximum energy loss coefficient of the structure system are shown to gradually decrease with the increase of the breadth ratio.The response time of gap resonance is shown to first increase and then decrease with the breadth ratio overall,regardless of the incident wave height,and the configuration that the two boxes have the same breadth would bring the largest response time of gap resonance.

关键词： gap resonance wave amplification varying breadth ratios OpenFOAM

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Analysis of the nutation and precession of the vortex core and the influence of operating parameters in a cyclone separator

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Chinese Journal of Chemical engineering 2022年第6期35卷 1-10页

作者： Pan Zhang Guanghui Chen Weiwen Wang Guodong Zhang Huaming Wang college of Electromechanical engineering and Key Laboratory of Multiphase Flow Reaction and Separation engineering of Shandong Province Qingdao University of Science and TechnologyQingdao 266069China college of Chemical engineering Qingdao University of Science and TechnologyQingdao 266043China School of naval architecture and Electrical engineering Zhejiang Ocean UniversityZhoushan 316022China

Vortices motion in the anisotropic turbulent flow of cyclones makes a vital impact on flow stability and collection performance.Nevertheless,there remains a lack of clarity in the overall feature of vortices motion.In this work,a numerical analysis was conducted to clarify the complex motion of the vortex core in a cyclone separator.The validity of the numerical model was demonstrated by comparing the computational results with experimental data in the literature.As revealed by the results,the vortex core not only has a precession motion about the geometrical center axis but also does a nutation motion in the axial direction.The frequencies of the precession motions show two main peaks.And the magnitudes of the precession and nutation motions have non-uniform distributions in the cyclone.Moreover,the precession-nutation motions of the vortex cores exhibit a similar fluctuant pattern to the dust ring on the separator wall.The inlet gas velocity and the inlet solid loading show vital effects on the magnitudes and frequencies of precession and nutation motion.

关键词： Cyclone separator Precession vortex core Nutation motion Separation efficiency Numerical simulation Fluid mechanics

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Review on the Progress and Issues in Liquid Tank Sloshing of Ships

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China ocean engineering 2023年第5期37卷 709-724页

作者： ZHANG Zhen TAO Ai-feng WU Qiao-rui XIE Yong-he Key Laboratory of Ministry of Education for Coastal Disaster and Protection Hohai UniversityNanjing 210098China college of Harbor Coastal and Offshore EngineeringHohai UniversityNanjing 210098China college of naval architecture and Maritime Zhejiang Ocean UniversityZhoushan 316022China

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.

关键词： naval architecture and marine engineering liquid tank sloshing liquid cargo ship large deformation progress review

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Avoiding Small Denominator Problems by Means of the Homotopy Analysis Method

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Advances in Applied Mathematics and Mechanics 2023年第2期15卷 267-299页

作者： Shijun Liao Center of Marine Numerical Experiment State Key Laboratory of Ocean EngineeringShanghai 200240China School of naval architecture Ocean and Civil EngineeringShanghai Jiaotong UniversityShanghai 200240China

The so-called“small denominator problem”was a fundamental problem of dynamics,as pointed out by Poincar´e.Small denominators appear most commonly in perturbative theory.The Duffing equation is the simplest example of a non-integrable system exhibiting all problems due to small denominators.In this paper,using the forced Duffing equation as an example,we illustrate that the famous“small denominator problems”never appear if a non-perturbative approach based on the homotopy analysis method(HAM),namely“the method of directly defining inverse mapping”(MDDiM),is used.The HAM-based MDDiM provides us great freedom to directly define the inverse operator of an undetermined linear operator so that all small denominators can be completely avoided and besides the convergent series of multiple limit-cycles of the forced Duffing equation with high nonlinearity are successfully obtained.So,from the viewpoint of the HAM,the famous“small denominator problems”are only artifacts of perturbation methods.Therefore,completely abandoning perturbation methods but using the HAM-based MDDiM,one would be never troubled by“small denominators”.The HAM-based MDDiM has general meanings in mathematics and thus can be used to attack many open problems related to the so-called“small denominators”.

关键词： Small denominator problem Duffing equation limit cycle homotopy analysis method(HAM) MDDiM

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Health care data analysis and visualization using interactive data exploration for sportsperson

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Science China(Information Sciences) 2022年第6期65卷 85-97页

作者： Hao LIU Yang ZHANG Ke LIAN Yifei ZHANG Oscar Sanjuán MARTíNEZ Rubén González CRESPO Department of Sport and Exercise Sciences Kunsan National University Department of naval architecture and ocean engineering Ludong University Computer Science Department School of Engineering and Technology Universidad Internacional de La Rioja

Sports have scored significant attention among the public in this multifaceted world. Diverse training strategies are followed by many athletics and even flexible to adapt comfortable and optimal techniques. This fact has led physicians and educators to encourage remote health surveillance as one of the core strategies in athletic training. The need for innovative data exploration methodologies capable of facing Big Data’s influence to make remote monitoring services viable has been raised by the growing ties of networks that deliver high quantities of real-time data. This paper presents an interactive healthcare data exploration and visualization(IHDEV) model to enhance multi-scaling data analysis and visualization in the athletic health vision platform. This paper aims to simplify optimization methods to measure sportsperson muscle tension. This model illustrates a three-layer architecture with a raw data acquisition layer, data analysis layer, and visualization layer. The first layer considers the acquisition of health-related data from the athletes for remote monitoring using IoT and stores it into the cloud. The data analysis layer adapts artificial intelligence(AI) in data mining. The final layer introduces an intelligent interactive data visualization model assisted by a reactive workflow mechanism, enabling analysis and visualization solutions to be composed in a personalized data flow appropriate to the athletic training. This experimental study extended with two healthcare datasets to show the feasibility of IHDEV in promoting healthcare based athletic monitoring and improves the accuracy ratio of 96.7%, prediction ratio of 96.2%, an efficiency ratio of 96.8%, Pearson correlation coefficient of 98.2%, and reduces the error rate of 18.7% compared to other conventional models.

关键词： artificial intelligence health monitoring data visualization data analysis athletics

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Aero-Hydrodynamic Coupled Dynamic Characteristics of Semi-Submersible Floating Offshore Wind Turbines Under Inflow Turbulence

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中国海洋工程:英文版 2023年第4期37卷 660-672页

作者： JIANG Hai-rui BAI Xing-lan Murilo A.VAZ School of naval architecture and Maritime Zhejiang Ocean UniversityZhoushan 316022China Key Laboratory of Offshore engineering Technology of Zhejiang Province Zhoushan 316022China ocean engineering Program Federal University of Rio de JaneiroRio de JaneiroBrazil

In this study,the frequency characteristics of the turbulent wind and the effects of wind-wave coupling on the low-and high-frequency responses of semi-submersible floating offshore wind turbines(FOWT)are investigated.Various wave load components,such as first-order wave loads,combined first-and second-order difference-frequency wave loads,combined first-and second-order sum-frequency wave loads,and first-and complete second-order wave loads are taken into consideration,while different turbulent environments are considered in aerodynamic loads.The com-parison is based on time histories and frequency spectra of platform motions and structural load responses and statistical values.The findings indicate that the second-order difference-frequency wave loads will significantly increase the natural frequency of low-frequency motion in the responses of the platform motion and structure load of the semi-submersible platform,which will cause structural fatigue damage.Under the action of turbulent wind,the influences of second-order wave loads on the platform motion and structural load response cannot be ignored,especially under extreme sea conditions.Therefore,in order to evaluate the dynamic responses of semi-submersible FOWT more accurately,the actual environment should be simulated more realistically.

关键词： turbulence characteristics floating offshore wind turbines second-order hydrodynamic loads low-and high-frequency responses aero-hydrodynamic coupling

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Numerical Investigation of Submarine Hydrodynamics and Flow Field in Steady Turn

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China ocean engineering 2016年第1期30卷 57-68页

作者：曹留帅朱军万文彬 Department of naval architecture and ocean engineering Naval University of Engineering

This paper presents numerical simulations of viscous flow past a submarine model in steady turn by solving the Reynolds-Averaged Navier-Stokes Equations（RANSE） for incompressible, steady flows. The rotating coordinate system was adopted to deal with the rotation problem. The Coriolis force and centrifugal force due to the computation in a bodyfixed rotating frame of reference were treated explicitly and added to momentum equations as source terms. Furthermore, velocities of entrances were coded to give the correct magnitude and direction needed. Two turbulence closure models（TCMs）, the RNG k-ε model with wall functions and curvature correction and the Shear Stress Transport（SST） k-ω model without the use of wall functions, but with curvature correction and low-Re correction were introduced, respectively. Take DARPA SUBOFF model as the test case, a series of drift angle varying between 0° and 16° at a Reynolds number of 6.53×10^6 undergoing rotating arm test simulations were conducted. The computed forces and moment as a function of drift angle during the steady turn are mostly in close agreement with available experimental data. Though the difference between the pressure coefficients around the hull form was observed, they always show the same trend. It was demonstrated that using sufficiently fine grids and advanced turbulence models will lead to accurate prediction of the flow field as well as the forces and moments on the hull.

关键词： submarine hydrodynamics flow field rotating coordinate system Coriolis and centrifugal force

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Study on Far Field Wave Patterns and Their Characteristics of Havelock Form Green Function

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China ocean engineering 2013年第3期27卷 283-298页

作者：许勇董文才肖汶斌 Department of naval architecture & ocean engineering Naval University of Engineering

A new mathematical integral representation including five integrals about the far field wave shape fimction of Havelock form translating-pulsating source is obtained by performing variable substitution. Constant-phase curves and propagation wave patterns are investigated by applying stationary phase analysis method to the new representation. Some findings are summarized as follows：（1） when 0〈r 〈0.25 （where r is the Strouhal number）, three types of stationary phase curves corresponding to three propagation wave patterns such as fan wave pattern, inner V and outer V wave patterns, are found in the integral representation. （2） When r 〉0.25, besides three types of wave patterns such as a ring-faning wave pattern, a fan wave pattern and an inner V wave pattern, a new one called parallel wave pattern is also found which not only exists in the integrals about the ring-fan wave and fan wave, but also in the integrals whose interval is [0, 7＇] ~ In addition, Characteristics about these parallel waves such as mathematical expressions, existence conditions, propagation directions and wave lengths are obtained, and cancellation relationships between these parallel waves are stated, which certificates the fact that there are no parallel waves existing in the far field.

关键词： translating-pulsating source propagation wave patterns constant-phase curves parallel wave pattern

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Numerical Study on Air Turbines with Enhanced Techniques for OWC Wave Energy Conversion

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China ocean engineering 2017年第5期31卷 517-527页

作者： CUI Ying HYUN Beom-Soo KIM Kilwon Department of ocean engineering College of EngineeringOcean University of China Division of naval architecture and ocean engineering Korea Maritime and Ocean University

In recent years,the oscillating water column(OWC) wave energy converter,which can capture wave energy from the ocean,has been widely applied all over the world.As the essential part of the OWC system,the impulse and Wells turbines are capable of converting the low pressure pneumatic energy into the mechanical shaft power.As an enhanced technique,the design of endplate or ring attached to the blade tip is investigated numerically in this paper.3 D numerical models based on a CFD-software FLUENT 12.0 are established and validated by the corresponding experimental results from the reports of Setoguchi et al.(2004) and Takao et al.(2001).Then the flow fields and non-dimensional evaluating coefficients are calculated and analyzed under steady conditions.Results show that the efficiency of impulse turbine with ring can reach up to 0.49 when Ф=1,which is 4% higher than that in the cases for the endplate-type and the original one.And the ring-type Wells turbine with fixed guide vanes shows the best performance with the maximal efficiency of 0.55,which is 22% higher than that of the original one.In addition,the quasi-steady analysis is used to calculate the mean efficiency and output-work of a wave cycle under sinusoidal flow condition.Taking all together,this study provides support for structural optimization of impulse turbine and Wells turbine in the future.

关键词： OWC impulse turbine Wells turbine CFD endplate ring quasi-steady analysis

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Numerical Simulation of the Flow in a Waterjet Intake Under Different Motion Conditions

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Journal of Shanghai Jiaotong university(Science) 2022年第3期27卷 356-364页

作者：许慧丽邹早建 School of naval architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of ocean engineering Shanghai Jiao Tong UniversityShanghai 200240China

By solving the three-dimensional incompressible Reynolds-averaged Navier-Stokes equations,numerical simulations of the viscous flow within a flush type intake duct of a waterjet under different motion conditions are carried out.Therein,the effects of the steering and reversing unit as well as the impeller shaft on the flow field are taken into account.The numerical results show that the static pressure under backward conditions with the reversing jet flow is the lowest,and the cavitations are most likely to occur within the intake duct.The flow field under forward conditions is less uniform because of the shaft,while the velocity uniformity under backward conditions is improved.The shaft rotation causes an asymmetric secondary flow above the shaft under all conditions.The pressure contours under backward conditions with the reversing jet flow are sensitive to the presence of the shaft.This study can provide some references for the design optimization of waterjet propulsion system.

关键词： waterjet intake duct viscous flow numerical simulation

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