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Coupled two-dimensional discrete element and multibody dynamic modeling for interaction of the soil and rough shaped rigid bodies

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Acta Mechanica Sinica 2022年第7期38卷 148-163,I0004页

作者： Ning Ding Jinyang Liu Caishan Liu Department of Engineering Mechanics School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China State Key Laboratory of Turbulence and Complex System College of EngineeringPeking UniversityBeijing100871China

The study of soil and rigid body system interactions is very important for the exploration of the Moon and Mars *** discrete element method(DEM)is a relatively accurate simulation method to study dry sand soil mechanical ***,it is not suitable for bodies that are in mutual contact,connected due to constraints or have complex inertia properties due to their *** efficient combination of the two-dimensional discrete element and multibody dynamic modeling method is proposed to solve the problem,in which the contacts and frictions among the granular spheres and the multibody system,including the smooth and rough rigid bodies,are taken into *** this work,the soil field is modeled by a two-dimensional DEM,and the dynamics of the constrained rigid body system are modeled by the Cartesian method.A detection algorithm is developed to address the interactions between spherical discrete elements and roughly shaped rigid *** advantage of this coupled method is that it enables the simultaneous capture of both ***,the program is verified by simulation experiments of the three-ball collision and the collision among the rectangular bars and the three *** on this,the movement of the toothed wheel in the granular matter is analyzed,and the results show that the wheel with six teeth and 30°inclination has the fastest forward *** extraterrestrial objects,the wheel grip worsens,but the forward speed first increases and then decreases with decreasing gravity acceleration and loads on wheels,which proves that the coupled two-dimensional DEM and multibody dynamic program is effective in solving engineering problems.

关键词： Discrete element method Multibody dynamic system Rough-shaped rigid body Toothed wheel in granular matter

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Comparative study of Reynolds-averaged Navier–Stokes and partially-averaged Navier–Stokes models for cavitation flows around a hemispherical head-form body

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European Journal of Mechanics, B/Fluids 2025年 113卷

作者： Park, Junyoung Seok, Woochan Department of Marine Convergence Engineering Pukyong National University Busan Korea Republic of Hyundai Maritime Research Institute HD Hyundai Heavy Industries Ulsan Korea Republic of Department of Naval Architecture and Marine System Engineering Pukyong National University Busan Korea Republic of

Cavitation causes the erosion of marine propellers and induces noise and vibration within the mechanical system. In this study, the results of Reynolds-averaged Navier–Stokes (RANS) and partially-averaged Navier–Stokes (PANS) models for detecting cavitation flows around a three-dimensional (3D) hemispherical head-form body were compared. These turbulence models can accurately depict the unsteady characteristics of cavitation flows. To investigate the effect of these turbulence models on flow characteristics, we analyzed the periodic shedding of the sheet and cloud cavitation. In addition to the shape of the cavity around the body, the pressure, velocity, turbulent kinetic energy, and turbulent viscosity were compared to identify the differences between the turbulent models. An open-source platform OpenFOAM was used for this analysis. The results revealed that the pressure coefficient in the PANS model was consistent with the experimental data. Furthermore, the PANS model provided an accurate depiction of the development process of sheet and cloud cavitation. © 2025

关键词： Cavitation Computational Fluid Dynamics (CFD) Hemispherical head-form body OpenFOAM (Open-source Field Operation and Manipulation) Partially-averaged Navier–Stokes (PANS) Reynolds-averaged Navier–Stokes (RANS)

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Formation Control and Collision Avoidance of Multiple USVs Based on Multi-agent Reinforcement Learning

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Journal of Institute of Control, Robotics and systems 2024年第12期30卷 1398-1405页

作者： Koo, Japyeong Kim, Kihun Jung, Jongdae Department of Naval Architecture and Ocean Engineering Chungnam National University Korea Republic of Ocean and Maritime Digital Technology Research Division Korea Research Institute of Ships and Ocean Engineering Korea Republic of Department of Autonomous Vehicle System Engineering Chungnam National University Korea Republic of

In this study, we developed a reinforcement learning-based approach for the cooperative navigation of unmanned surface vehicles (USVs) in marine environments. Specifically, we addressed the formation control and collision avoidance of USVs. To achieve this, we used a virtual leader to coordinate the reference position of each USV so as to maintain a specific formation shape. Additionally, we designed a dedicated reward function within a reinforcement learning framework to simultaneously maintain given formations and maximize collision avoidance. The models were then trained and tested in simulation environments with various obstacles. We evaluated three algorithms for formation control performance and obstacle avoidance: deep Q-network (DQN), multi-agent proximal policy optimization (MAPPO), and multi-agent deep deterministic policy gradient (MADDPG). The results showed that the MAPPO algorithm has higher success rates in collision avoidance and better formation maintenance compared with DQN and MADDPG. © ICROS 2024.

关键词： Unmanned surface vehicles

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Discrete Event Simulation of Aircraft Sortie Generation on an Aircraft Carrier

Discrete Event Simulation of Aircraft Sortie Generation on a...

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2023 Winter Simulation Conference, WSC 2023

作者： Yoon, Hee Chang Oh, Seung Heon Woo, Jong Hun Chung, Jung-Hoon Lee, Hyuk Jung, Sun-Ah Seoul National University Department of Naval Architecture and Ocean Engineering 1th Gwanak-ro Gwanak-Gu Seoul08826 Korea Republic of Korea Institute of Machinery & Materials Mechanical Systems Safety Research Division Department of System Dynamics 156 Gajeongbuk-Ro Yuseong-Gu Daejeon34103 Korea Republic of

ISBN: (纸本)9798350369663

The Sortie Generation Rate (SGR) which refers to the number of sorties that can be generated per unit time, is a key indicator for evaluating the ability of an airbase. However, an aircraft carrier has many constraints compared to a land-based airbase, such as spatial and environmental constraints, making it difficult to apply existing land-based research to analyze aircraft carrier operations. On the other hand, the Sortie Generation Process (SGP) on an aircraft carrier is similar to a logistics/production system in that sorties are generated through aircraft. Therefore, this study proposes a framework for analyzing the SGP on an aircraft carrier using discrete event simulation and defines the classes that make up the simulation. In addition, SGP analysis simulations were implemented using the proposed framework and several experiments were performed to demonstrate the feasibility of applying the proposed framework in practice. © 2023 IEEE.

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Discrete Event Simulation of Aircraft Sortie Generation on an Aircraft Carrier 23

Discrete Event Simulation of Aircraft Sortie Generation on a...

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Proceedings of the Winter Simulation Conference

作者： Hee Chang Yoon Seung Heon Oh Jong Hun Woo Jung-Hoon Chung Hyuk Lee Sun-Ah Jung Department of Naval Architecture and Ocean Engineering Seoul National University Seoul REPUBLIC OF KOREA Mechanical Systems Safety Research Division Department of System Dynamics Korea Institute of Machinery & Materials Daejeon REPUBLIC OF KOREA

ISBN: (纸本)9798350369663

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Comparative Life Cycle Assessment on Various Hydrogen Supply Methods from Overseas

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SSRN 2023年

作者： Lee, Gang Nam Kim, Jong Mu Jung, Kwang Hyo Park, Hyun Department of Ocean System Engineering Jeju National University Jeju-si63243 Korea Republic of Department of Naval Architecture and Ocean Engineering Pusan National University Busan46241 Korea Republic of

With the increasing importance of decarbonization to prevent global climate change, hydrogen supply has received considerable attention from several countries, including Korea and Japan, with increasing demand for the implementation of a hydrogen economy. This study conducted a comprehensive environmental impact assessment of hydrogen supply methods from overseas through life cycle assessment (LCA). The blue hydrogen produced in Australia was considered for import to Korea by ocean shipping. The study also conducted an analysis of the holistic environmental effects in the life cycle of the hydrogen ocean transport for various types of hydrogen storage methods (CH2, LH2, LOHC, LNH3, and LNG), and also alternative marine fuels (MGO, LNG, LPG, CH2, LH2, LNG-LH2, MeOH and LNH3) for ship transportation. Environmental impact performance was presented in terms of global warming potential (GWP), acidification potential (AP), photochemical ozone creation potential (POCP), eutrophication potential (EP), and particulate matter (PM). For the environmental results, sensitivity studies were conducted to analyze the effect of operating distance and cargo tank size when shipping hydrogen through ocean transport, and the GWP results of transportation of green hydrogen and ammonia were also compared to blue hydrogen and ammonia transport. A cost analysis was performed for the overall processes of hydrogen ocean transport, and the results were included in the study with the estimated hydrogen price for each transportation method. © 2023, The Authors. All rights reserved.

关键词： Ammonia

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Determination of cryogenic temperature loads for finite-element model of LNG bunkering ship under LNG release accident

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Curved and Layered Structures 2023年第1期10卷

作者： Nubli, Haris Sohn, Jung Min Kim, Sangjin Department of Marine Design Convergence Engineering Pukyong National University Busan Korea Republic of Department of Naval Architecture and Marine System Engineering Pukyong National University Busan Korea Republic of Department of Marine Environment and Engineering National Sun Yat-sen University Kaohsiung Taiwan

The rising demand for liquefied natural gas (LNG)-fueled ships requires the LNG bunkering facility that partially uses a ship-to-ship operation. The bunkering process of LNG fuel may have a greater risk due to LNG volatility. The cryogenic temperature of LNG poses a threat to the personnel and structural embrittlement to ships. Therefore, cryogenic spill protection optimization was introduced concerning the structural strength analysis using finite element (FE) by utilizing cryogenic temperature loads provided by the computational fluid dynamics (CFD) model of an LNG release. This study aims to build a platform for transferring the temperature load profile from CFD to FE software accurately. The CFD model usually uses a structured Cartesian grid, and the FE method adopts an unstructured tetrahedral or hexahedral mesh. As a result, both configurations store results at different positions, and it is not preferred for the load profile to be transferred directly. The error will be greater due to the variance of positions. Random Forest, a machine learning method, has been employed that uses a regression technique to deal with a continuous variable. An accurate load profile for the FE model can be obtained by adopting decision tree learning in Random Forest. The procedure for determining the temperature load profile is presented in this article. © 2023 the author(s), published by De Gruyter.

关键词： Liquefied natural gas

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Modeling and Performance Estimation for L-Shaped Owc Wave Energy Converters with a Theoretical Correction for Spring-Like Air Compressibility

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SSRN 2024年

作者： Nguyen, Duy Tong Chow, Yi-Chih Lin, Chen-Chou Center for Ocean Energy System National Taiwan Ocean University Keelung Taiwan Department of Mechanical & Mechatronic Engineering National Taiwan Ocean University Keelung Taiwan Department of Systems Engineering & Naval Architecture National Taiwan Ocean University Keelung Taiwan

The investigation of Oscillating Water Columns (OWC) has gained significant attention in recent years thanks to their resilient structural design, allowing them to withstand harsh environmental conditions. This study focuses on the L-shaped OWC (L-OWC) due to its excellent energy capture efficiency. It should be noted that air compressibility plays a significant role in the plenum chamber of the OWC, especially at full scale. The paper proposes a synergistically analytical-numerical modeling approach, facilitating the evaluation of hydrodynamic coefficients and the performance estimation with a theoretical correction for the spring-like air compressibility. The methodology is applied successfully to a model-scale L-OWC design, employing three-dimensional, incompressible-flow simulations combined with an impeller model. The study reveals the hydrodynamic characteristics of the L-OWC: small fluid damping coefficient and large added mass, and hence the possibility that the spring-like air compressibility can be used to raise the efficiency of power capturing. Furthermore, there exists an interval where the air compressibility has a positive effect on the performance, not only having a significantly longer span than that of the conventional OWC but also much more directly matching the period range of high energy potential found in the wave climate of Northeastern Taiwan waters. © 2024, The Authors. All rights reserved.

关键词： Wave energy conversion

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The Effect of a Ship's Acceleration and Deceleration on Parametric Roll Motion in Regular Head Waves at Resonance Conditions

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SSRN 2023年

作者： Pesman, Emre Copuroglu, Hasan Islam Islam Katayama, Toru Department of Naval Architecture and Marine Engineering Surmene Faculty of Marine Sciences Karadeniz Technical University Trabzon Turkey Department of Marine System Engineering Graduate School of Engineering Osaka Metropolitan University Osaka Sakai599-8531 Japan

The effect of a ship's acceleration and deceleration in regular head waves on parametric roll motion is examined experimentally in the study and compared with a mathematical model. Operators queries such as "Should I accelerate or decelerate the ship in resonance condition?" and "Is the magnitude of acceleration or deceleration effective in reducing large roll motion?" are tried to answer. It is well known that waves with lengths similar to that of the ship may suffer parametric roll motion. Additionally, it is possible to say that the encounter frequency itself provides the ship's tuning factor. Since one particular wave is selected with a length equal to the ship's length, the tuning factor in this study at ship operation is the velocity. Results indicate that the amplitudes of roll motion at acceleration and deceleration periods are still large until the acceleration value equals zero. Results also indicate that the magnitude of acceleration or deceleration affects the roll motion. The mathematical model is also solved numerically and compared with experimental results to better understand the effect of acceleration magnitude. © 2023, The Authors. All rights reserved.

关键词： Ships

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Dynamics and Control of Marine Mechatronic Oscillators Using Electromagnetic Coupling and Switching Power Electronics

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SSRN 2024年

作者： Tsakyridis, Georgios Xiros, Nikolaos I. Litsardakis, George Rovithakis, George German Aerospace Center Institute of Space Systems Department of System Analysis Space Segment Bremen Germany Department of Naval Architecture & Marine Engineering University of New Orleans New OrleansLA United States Department of Electrical & Computer Engineering Aristotle University of Thessaloniki Thessaloniki Greece

Developing force control mechanisms employing electromagnetics is on the rise in active control applications for flexible mechanical systems like marine engines and shipboard machinery. Electromagnetic control devices offer superior performance indicators compared to traditional mechanical force actuators in terms of longevity, energy efficiency, maintenance requirements, rapid control response, and high operating speeds. This article investigates the use of magnetic actuation and switching power electronics in addressing the stabilization and tracking control challenges encountered in the dynamics of a mechanical system with a single degree of freedom, comprising mass, spring, and damper elements. Particularly, a linear mechanical oscillator is nonlinearly coupled with an electromagnet and its associated driving circuit via the magnetic field. The electromagnetically actuated mechanical system exhibits characteristics of a differentially flat nonlinear system. A control strategy is suggested for the purpose of tracking reference position trajectories using output feedback linearization. The synthetic linearized control signal is subsequently guided to a DC-DC buck converter, able to regulate the system’s input voltage in a wide range of operation, by switching the duty cycle. The converter is described using a precise electrical model of the system, accounting for parasitic resistances in the inductor, capacitor, and switches. An averaged state space approach is utilized to create a mathematical nonlinear model for the converter which is then linearized by employing the Exact Feedback Linearization technique. By applying optimal control theory, the controller's coefficients are fine-tuned for optimal performance. To assess the proposed method's performance, the dynamics of the compensated mechatronic system is simulated using MATLAB/Simulink. The simulation results demonstrate that the proposed control scheme choice for active control of vibrating mechanical system

关键词： Controllers

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