• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.14-22
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• 2009

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.556-563
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• 2019

The ice keel gouge and seabed interaction is one of the major considerations in the design of an Arctic pipeline system. Ice keel and seabed interaction engineering models based on experimental data, which give an explicit equation for estimating the ice gouging depth, have been suggested. The suggested equations usually overestimate the ice keel gouging depth. In addition, various types of numerical analyses have been carried out to verify the suggested engineering model equations in comparison to the experimental data. However, most of numerical analysis results were also overestimated compared with the laboratory experimental data. In this study, a numerical analysis considering the contact condition and geostatic stress was carried out to predict the ice keel gouging depth and compared with the previous studies. Considering the previously mentioned conditions, more accurate results were produced compared with the laboratory experiment results and the error rate was reduced compared to previous numerical analysis studies.

• Journal of Ocean Engineering and Technology
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• v.25 no.3
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• pp.47-52
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• 2011

3D geometric modeling has a lot of advantages in the field of design and manufacturing. Many manufacturing processes and production lines are using 3D geometric modeling technique. These help reduce the cost and time for manufacturing. The purpose of this study is the realization of a 3D cutting shape for an H-Beam used in ships and ocean plants. The complex 3D cutting shapes could be represented by using the boolean operation of basic figures. Graphic functions with parameters were used to simply define the basic figures. The developed system can show the complex cutting shape of an H-beam simply and quickly. This system can be utilized for the automatic cutting system for an H-beam.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.3
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• pp.176-185
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• 2015

Recently, focus has been placed on ocean energy resources because environmental concerns regarding the exploitation of hydrocarbons are increasing. Tidal current power, one of the ocean energy resources, has great potential worldwide due to its high energy density. The flow velocity is the most crucial factor for the power estimation of TCP(Tidal Current Power) system since the kinetic energy of the flow is proportional to the cube of the flow speed. So sufficient inflow speed to generate electricity from the tidal current power is necessary. A duct system can accelerate the flow velocity, which could expand the applicable area of TCP systems to relatively lower velocity sites. The shapes of the inlet and outlet could affect the flow rate inside the duct. To investigate the performance of the duct, various ducts were preliminary designed considering the entire system that is single-point moored TCP system and a series of simulations were carried out using ANSYS-CFX v13.0 CFD software. This study introduces a ducted turbine system that can be moored to a seabed. A performance estimation and comparison of results with conventional tidal converters were summarized in this paper.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.210-226
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• 2013

Ever since the Arctic region has opened its mysterious passage to mankind, continuous attempts to take advantage of its fastest route across the region has been made. The Arctic region is still covered by thick ice and thus finding a feasible navigating route is essential for an economical voyage. To find the optimal route, it is necessary to establish an efficient transit model that enables us to simulate every possible route in advance. In this work, an enhanced algorithm to determine the optimal route in the Arctic region is introduced. A transit model based on the simulated sea ice and environmental data numerically modeled in the Arctic is developed. By integrating the simulated data into a transit model, further applications such as route simulation, cost estimation or hindcast can be easily performed. An interactive simulation system that determines the optimal Arctic route using the transit model is developed. The simulation of optimal routes is carried out and the validity of the results is discussed.

• International Journal of Ocean System Engineering
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• v.1 no.1
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• pp.1-8
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• 2011

Ocean structures and vehicles are exposed to severe ocean environment conditions such as waves, winds and currents. When such ocean structures and vehicles are designed, an accurate structure analysis is required to keep the system safely. Hydro-elastic analysis is one of key issues to design such structures and vehicles. In many previous investigations, numerical analyses for hydro-elastic problem have been used. In this study, an experimental analysis is carried out and the circular cylindrical shell is considered. Dynamical characteristics for a circular cylindrical shell are identified by experimental vibration analysis in air and water. The natural frequencies and mode shapes are compared in air and water to obtain hydro-elastic effects. Some interesting results are found in the variation of natural frequencies and damping ratios of the circular cylindrical shell for different water contact depths.

• Steel and Composite Structures
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• v.36 no.1
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• pp.31-45
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• 2020

The purpose of this study is to develop an effective iterative two-stage method (ITSM) for structural damage identification of offshore platform structures. In each iteration, a new damage index, Modal Energy-Based Damage Index (MEBI), is proposed to help effectively locate the potential damage elements in the first stage. Then, in the second stage, the beetle antenna search (BAS) algorithm is used to estimate the damage severity of these elements. Compared with the well-known particle swarm optimization (PSO) algorithm and genetic algorithm (GA), this algorithm has lower computational cost. A modal energy based objective function for the optimization process is proposed. Using numerical and experimental data, the efficiency and accuracy of the ITSM are studied. The effects of measurement noise and spatial incompleteness of mode shape are both considered. All the obtained results show that under these influences, the ITSM can accurately identify the true location and severity of damage. The results also show that the objective function based on modal energy is most suitable for the ITSM compared with that based on flexibility and weighted natural frequency-mode shape.

• Geomechanics and Engineering
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• v.19 no.4
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• pp.307-314
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• 2019

Light construction waste (LCW) particles are pieces of light concrete or insulation wall with light quality and certain strength, containing rich isolated and disconnected pores. Mixing LCW particles with soil can be one of the alternative lightweight soils. It can lighten and stabilize the deep-thick soft soil in-situ. In this study, the unconfined compressive strength (UCS) and its mechanism of Construction Waste Stabilized Lightweight Soil (CWSLS) are investigated. According to the prescription design, totally 35 sets of specimens are tested for the index of dry density (DD) and unconfined compressive strength (UCS). The results show that the DD of CWSLS is mainly affected by LCW content, and it decreases obviously with the increase of LCW content, while increases slightly with the increase of cement content. The UCS of CWSLS first increases and then decreases with the increase of LCW content, existing a peak value. The UCS increases linearly with the increase of cement content, while the strength growth rate is dramatically affected by the different LCW contents. The UCS of CWSLS mainly comes from the skeleton impaction of LCW particles and the gelation of soil-cement composite slurry. According to the distribution of LCW particles and soil-cement composite slurry, CWSLS specimens are divided into three structures: "suspend-dense" structure, "framework-dense" structure and "framework-pore" structure.

• Ocean Systems Engineering
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• v.5 no.3
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• pp.181-198
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• 2015

An OSV (Offshore Support Vessel) is being used to install a structure which is laid on its deck or an adjacent transport barge by lifting off the structure with its own crane, lifting in the air, crossing splash zone, deeply submerging, and lastly landing it. There are some major considerations during these operations. Especially, when lifting off the structure, if operating conditions such as ocean environmental loads and lifting off velocity are not suitable, the collision can be occurred due to the relative motion between the structure and the OSV or the transport barge. To solve this problem, this study performs the physics-based simulation of the lifting off step while the OSV installs the structure. The simulation includes the calculation of dynamic responses of the OSV and the structure, including the collision detection between the transport barge and the structure. To check the applicability of the physics-based simulation, it is applied to a problem of the lifting off step by varying the ocean environmental loads and the lifting off velocity. As a result, it is confirmed that the operability of the lifting off step are affected by the conditions.

• Journal of Ocean Engineering and Technology
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• v.33 no.3
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• pp.245-251
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• 2019

When an offshore foundation is exposed to waves and currents, local scour could develop around a pile and even lead to structural failure. Therefore, understanding and predicting the scour due to sediment transport around foundations are important in the engineering design. In this study, the flow and scour around a monopole foundation exposed to a current were investigated using a method that coupled the computational fluid dynamics (CFD) and discrete element method (DEM). The open source computation fluid dynamics library OpenFOAM and a sediment transport library were coupled in the OpenFOAM platform. The incipient motion of the particle was validated. The flow fields and sediment transport around the monopole were simulated. The scour depth development was simulated and compared with existing experimental data. For the upstream scour hole, the equilibrium scour depth could be reproduced qualitatively, and it was underestimated by about 23%.