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URANS simulations for a free-running container ship:Part 2. Added power

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Journal of Hydrodynamics 2021年第3期33卷 448-467页

作者： Dong-Hwan Kim Yugo Sanada Hamid Sadat-Hosseini Frederick Stern IIHR-Hydroscience and Engineering The University of IowaIowa CityUSA Costal Development and Ocean Energy research Center Korea Institute of Ocean Science and TechnologyBusanKorea Mechanical Engineering University of North TexasDentonUSA

Part 2 reports the validation,local force and local flow study results for the free-running added power simulations whose conditions are the same as the self-propulsion test except for the increased propeller rotational speed and the presence of *** targeting the same mean Froude number in the wave condition,the propeller requires the increased propeller rotational speed for the operation at the low advance ratio due to the added *** test is performed at five different wavelengths in head waves and four different headings in the oblique *** the validation study,the time series of the validation variables is decomposed with discrete Fourier transform to extract the harmonic *** variables are global parameters,including motions,propeller thrust,and torque coefficients,added power variables,and self-propulsion factors which show reasonable agreement against the experiment results and produces a similar error from the self-propulsion *** local force study shows that the added resistance mostly appears at the bow due to the bow plunging during the short head wave and resonance *** contributions of the gravitational force and the buoyant force are found to increase as the stern motion exceeds the bow motion during the long head wave *** oscillation of the propeller performances shows correlation with the first harmonic amplitude of the propeller ***,pitch,and roll decay tests are performed prior to the main test to assess the natural frequencies of the *** as Part 1,a discretized propeller is used.

关键词： Added power unsteady Reynolds-averaged Navier-Stokes(URANS) KRISO Container Ship(KCS) CFDShip-IOWA

A unified approach to output synchronization of heterogeneous multi-agent systems via L2-gain design

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Control Theory and Technology 2017年第4期15卷 340-353页

作者： Shan Zuo Yongduan Song Hamidreza Modares Frank L. Lewis Ali Davoudi School of Automation Engineering University of Electronic Science and Technology of China Chengdu Sichuan China The University of Texas at Arlington research Institute Fort Worth U.S.A.

In this paper, a unified design procedure is given for output synchronization of heterogeneous multi-agent systems （MAS） on communication graph topologies, using relative output measurements from neighbors. Three different control protocols, namely, full-state feedback, static output-feedback, and dynamic output-feedback, are designed for output synchronization. It is seen that a unified design procedure for heterogeneous MAS can be given by formulation and solution of a suitable local L2-gain design problem. Sufficient conditions are developed in terms of stabilizing the local agents＇ dynamics, satisfying a certain small-gain criterion, and solving the output regulator equations. Local design procedures are presented for each agent to guarantee that these sufficient conditions are satisfied. The proposed control protocols require only one copy of the leader＇s dynamics in the compensator, regardless of the dimensions of the outputs. This results in lower-dimensional compensators for systems with high-order outputs, compared to the p-copy internal model approach. All three proposed control protocols are verified using numerical simulations.

关键词： Heterogeneous systems output-feedback output synchronization small-gain theorem

URANS simulations for a free-running container ship:Part 1. Turning-circle

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Journal of Hydrodynamics 2021年第3期33卷 421-447页

作者： Dong-Hwan Kim Yugo Sanada Sungtek Park Hamid Sadat-Hosseini Frederick Stern IIHR-Hydroscience and Engineering The University of IowaIowa CityUSA Costal Development and Ocean Energy research Center Korea Institute of Ocean Science and TechnologyBusanKorea Mechanical Engineering University of North TexasDentonUSA

The incompressible unsteady Reynolds-averaged Navier-Stokes(URANS)simulations are performed for a free-running container ship in maneuvering conditions:the starboard and portside turning circle simulations with 35°rudder *** validation variables include trajectory,motions,and propeller performances,and the prediction shows acceptable agreements against the experimental *** the steady-state part of the turning,the inertial forces balancing the local forces are reported to quantitatively assess the centrifugal force which appears from the force equilibrium between the rudder,propeller,and the *** study on the local flow focuses on finding the correlations between the propeller inflow and the propeller performance to investigate the differences in propeller performances during the portside and starboard *** preliminary simulations,performed with the grid triplet,comprise propeller open-water,resistance,and self-propulsion simulations,from which the validation studies and the studies for the local force and the local flow are fulfilled and applied for the main *** propeller and rudder are fully discretized and controlled,mimicking the ***-set,overset approach and Mentor’s SST model are employed for the free-surface capturing,large motion prediction,and turbulence closure.

关键词： Turning-circle unsteady Reynolds-averaged Navier-Stokes(URANS) KRISO Container Ship(KCS) CFDShip-IOWA

Recent Advancement in Modeling Seafloor Dissipative Mechanism in Shallow Water

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China Ocean Engineering 2008年第1期22卷 1-10页

作者： Philip L.-F.LIU Yong Sung PARK School of Civil and Environmental Engineering Cornell University

In this paper, the recent development in modeling seabed dissipative mechanisms in shallow water is reviewed. Specifically, laminar and turbulent boundary layer solutions as well as viscous mud flow solutions under transient waves are presented. These analytical solutions are compared with experimental data for both solitary waves and cnoidal waves. Very goed agreement is ohtained. The Boussinesq equations with boundary layer effects and the muddy seabed effects are also shown.

关键词： seabed dissipative mechardsms boundary layer Boussinesq equations

Bubbly shock propagation as a mechanism of shedding in separated cavitating flows

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Journal of Hydrodynamics 2017年第6期29卷 907-916页

作者： Harish Ganesh Simo A.Makiharju Steven L.Ceccio University of Michigan Ann ArborUSA University of California BerkeleyUSA

Stable attached partial cavitation in separated flows can transition to cloud shedding, and the mechanism of transition has been attributed to the presence of a re-entrant liquid jet. Our findings have revealed the presence of propagating bubbly shock waves as an alternative dominant mechanism of shedding when the compressibility of the bubbly mixture is appreciable. In the present paper, we discuss dynamics associated with these bubbly shock waves, interaction of shock waves with obstacles in their path, and means to manipulate their properties to control the shedding process by non-condensable gas injection.

关键词： Partial cavitation bubbly shock waves cloud cavitation X-ray densitometry

Frequency-dependent dielectric constant prediction of polymers using machine learning

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npj Computational Materials 2020年第1期6卷 1147-1155页

作者： Lihua Chen Chiho Kim Rohit Batra Jordan P.Lightstone Chao Wu Zongze Li Ajinkya A.Deshmukh Yifei Wang Huan D.Tran Priya Vashishta Gregory A.Sotzing Yang Cao Rampi Ramprasad School of Materials Science and Engineering Georgia Institute of Technology771 Ferst Drive NWAtlantaGA 30332USA Electrical and Computer Engineering University of Connecticut371 Fairfield WayStorrsCT 06269USA Polymer Program Institute of Material ScienceUniversity of Connecticut97 North Eagleville RoadStorrsCT 06269USA Collaboratory for Advanced Computing and Simulations University of Southern CaliforniaLos AngelesCA 90089-0242USA

The dielectric constant(ϵ)is a critical parameter utilized in the design of polymeric dielectrics for energy storage capacitors,microelectronic devices,and high-voltage ***,agile discovery of polymer dielectrics with desirableϵremains a challenge,especially for high-energy,high-temperature *** aid accelerated polymer dielectrics discovery,we have developed a machine-learning(ML)-based model to instantly and accurately predict the frequency-dependentϵof polymers with the frequency range spanning 15 orders of *** model is trained using a dataset of 1210 experimentally measuredϵvalues at different frequencies,an advanced polymer fingerprinting scheme and the Gaussian process regression algorithm.

关键词： dielectric constant polymer

High thermal conductivity of suspended few-layer hexagonal boron nitride sheets

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Nano research 2014年第8期7卷 1232-1240页

作者： Haiqing Zhou Jixin Zhu Zheng Liu Zheng Yan Xiujun Fan Jian Lin Gunuk Wang Qingyu Yan Ting Yu Pulickel M. Ajayan James M. Tour Department of Chemistry Rice University 6100 Main Street Houston Texas 77005 USA Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 537371 Singapore Department of Materials Science and NanoEngineering Rice University 6100 Main Street Houston Texas 77005 USA School of Materials Science and Engineering Nanyang Technological University Nanyang Avenue 639798 Singapore College of Electronic Information and Control Engineering Beijing University of Technology Beijing I00124 China The Smalley Institute for Nanoscale Science and Technology Rice University 6100 Main Street Houston Texas 77005 USA

The thermal conduction of suspended few-layer hexagonal boron nitride （h-BN） sheets was experimentally investigated using a noncontact micro-Raman spectroscopy method. The first-order temperature coefficients for monolayer （1L）, bilayer （2L） and nine-layer （9L） h-BN sheets were measured to be -（3.41 ± 0.12）× 10-2, -（3.15 ± 0.14） × 10-2 and -（3.78 ±0.16）× 10-2 cm-1.K-1, respectively. The room-temperature thermal conductivity of few-layer h-BN sheets was found to be in the range from 227 to 280 W.m-1-K-1, which is comparable to that of bulk h-BN, indicating their potential use as important components to solve heat dissipation problems in thermal management configurations.

关键词： two-dimensional hexagonal boron nitride(h-BN) thermal conductivity Raman spectroscopy

Improving electromechanical output of IPMC by high surface area Pd-Pt electrodes and tailored ionomer membrane thickness

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International Journal of Smart and Nano Materials 2014年第2期5卷 99-113页

作者： Viljar Palmre Seong Jun Kim David Pugal Kwang Kim Department of Mechanical Engineering University of Nevada-RenoRenoNVUSA Department of Mechanical Engineering University of Nevada-Las VegasLas VegasNVUSA

In this study,we attempt to improve the electromechanical performance of ionic polymer–metal composites(IPMCs)by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane *** proper electroless plating techniques,a high dispersion of palladium particles is achieved deep in the ionomer membrane,thereby increasing notably the interfacial surface area of *** membrane thickness is increased using 0.5 and 1 mm thick ionomer *** comparison,IPMCs with the same ionomer membranes,but conventional Pt electrodes,are also prepared and *** electromechanical,mechanoelectrical,electrochemical and mechanical properties of different IPMCs are characterized and *** electron microscopy-energy dispersive X-ray(SEM-EDS)is used to investigate the distribution of deposited electrode metals in the cross section of Pd-Pt *** experiments demonstrate that IPMCs assembled with millimeter thick ionomer membranes and newly developed Pd-Pt electrodes are superior in mechanoelectrical transduction,and show significantly higher blocking force compared to conventional type of *** blocking forces of more than 0.3 N were measured at 4V DC input,exceeding the force output of typical Nafion®117-based Pt IPMCs more than two orders of *** newly designed Pd-Pt IPMCs can be useful in more demanding applications,e.g.,in biomimetic underwater robotics,where high stress and drag forces are encountered.

关键词： ionic polymer-metal composite IPMC electroactive polymer palladium electrode

Evaluating acoustic communication performance of micro autonomous underwater vehicles in confined spaces

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Frontiers of Information Technology & Electronic Engineering 2018年第8期19卷 1013-1023页

作者： Qiu-yang TAO Yue-hai ZHOU Feng TONG Ai-jun SONG Fumin ZHANG School of Electrical and Computer Engineering Georgia Institute of Technology College of Ocean and Earth Sciences Xiamen University Department of Electrical and Computer Engineering The University of Alabama

Micro-sized autonomous underwater vehicles(μAUVs) are well suited to various applications in confined underwater spaces. Acoustic communication is required for many application scenarios of μAUVs to enable data transmission without surfacing. This paper presents the integration of a compact acoustic communication device with a μAUV prototype. Packet reception rate(PRR) and bit error rate(BER) of the acoustic communication link are evaluated in a confined pool environment through experiments while the μAUV is either stationary or *** pinpoint several major factors that impact the communication performance. Experimental results show that the multi-path effect significantly affects the synchronization signals of the communication device. The relative motion between the vehicle and the base station also degrades the communication performance. These results suggest future methods towards improvements.

关键词： Autonomous underwater vehicles Underwater acoustic communications Confined water space