• Journal of Aerospace System Engineering
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• v.12 no.3
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• pp.58-63
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• 2018

This work dealt with the design and manufacturing of composite blades of a vertical axis wind turbine system. In this work, aerodynamic and structural designs of sandwich composite blades for a vertical axis wind turbine system were performed. First, the aerodynamic and structural design requirements of the composite blades were investigated. After the structural design was complete, a structural analysis of the wind turbine blades was performed using the finite element analysis method. It was performed with the stress and displacement analysis at the applied load condition. A design modification for the structurally weak part was proposed as a result of the structural analysis. Through another structural analysis, it was confirmed that the final designed blade structure is safe.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.88-89
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• 2002

The aims of this study is to realize the structural design for development of a medium scale E-glass/epoxy composite wind turbine blade for a 750KW class horizontal axis wind turbine system. In this study, the various load cases specified by the IEC61400-1 international specification and GL Regulations for the wind energy conversion system were considered, and a specific composite structure configuration which can effectively endure various loads such as aerodynamic and centrifugal loads, loads due to accumulation of ice, hygro-thermal and mechanical loads was proposed. In order to evaluate the structure, the structural analysis for the composite wind turbine blade were peformed using tile finite element method(FEM). In the structural design, the acceptable blade structural configuration was determined through the parametric studies, and the most dominant design parameters were confirmed. In the stress analysis using the FEM, it was confirmed that the blade structure was safe and stable in any various load cases Moreover the safety of the blade root joint with insert bolts, newly devised in this study, was checked against the design fond and the fatigue.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3423-3428
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• 2014

Numerical studies were performed to evaluate the structural safety of a greenhouse under both snow and wind loads. In the case of a wind load, fluid-structure interaction (FSI) method was used to consider the local pressure distributions on the greenhouse-induced by aerodynamic characteristics. The results showed that the maximum stress and deformation occur near the junction of pipe supports and rafters of the roof, where connecting clips are installed. Moreover, the wind load is a more severe condition than a snow load. Overall, these results will be used to design a prefabricated connecting clip with easy installation and low maintenance.

• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.98-106
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• 2013

Seismic fragility curves for an offshore wind-turbine structure were obtained. The dynamic response of an offshore wind turbine was analyzed by considering the nonlinear behavior of layered soil and the added mass effect due to seawater. A pile-soil interaction effect was considered by using nonlinear p-y, t-z curves. In the analysis, the amplification effect of ground acceleration through layered soil was considered by applying ground motion to each of the soil layers. The vertical variation in ground motion was found by one-dimensional free-field analysis of ground soils. Fragility curves were determined by damage levels in terms of tower stress and nacelle displacements that were found from static pushover analysis of the wind-turbine structure.

• Fisheries and Aquatic Sciences
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• v.7 no.4
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• pp.204-214
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• 2004

The effect of wind. stresses on the flow and water quality has been examined, particularly focused on the environment of oyster farms in Gamak Bay, by a two dimensional numerical model. In autumn (wind: $45.0^{\circ}$, 4.3 m/s), the overall flow turned out to be stronger than any other seasons and in addition, a pair of anticlockwise and clockwise vortices has been created at the northwest of the bay. Consequently, the wind in autumn seemed efficient not only for growing oyster but also for reducing the water pollution as the flow becomes much more active. In summer an anoxic condition appeared around the northwest of the bay where the flow is stagnant. According to a field survey, the majority of oyster farms tended to be densely distributed around the areas where DO concentration is high. Furthermore, oyster farms with a high production (over 1,300 kg per hanging string of 100 m) were distributed along with approximately 4 of Ch-a concentration. This suggests that oyster production is closely related to the concentration of DO or Ch-a.

• Journal of Korean Association for Spatial Structures
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• v.15 no.1
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• pp.75-84
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• 2015

This paper presents the dimensionless wall distance, y+ effect on SST turbulent model for wind turbine blade. The National Renewable Energy Laboratory (NREL) Phase VI wind turbine was used for the study, which the wind tunnel and structural test data has publicly available. The near wall treatment and turbulent characteristics have important role for proper CFD simulation. Most of the CFD development in this area is focused on advanced turbulence model closures including second moment closure models, and so called Low-Reynolds (low-Re) number and two-layer turbulence models. However, in many cases CFD aerodynamic predictions based on these standard models still show a large degree of uncertainty, which can be attributed to the use of the $\epsilon$-equation as the turbulence scale equation and the associated limitations of the near wall treatment. The present paper demonstrates the y+ definition effect on SST (Shear Stress Transport) turbulent model with advanced automatic near wall treatment model and Gamma theta transitional model for transition from lamina to turbulent flow using commercial ANSYS-CFX. In all cases the SST model shows to be superior, as it gives more accurate predictions and is less sensitive to grid variations.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.72-77
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• 2019

Vinyl house consists of main rafter, lateral member, clamps and polyethylene film. Many vinyl houses are used to grow fruits, flowers and vegetables in the countryside. Due to climate change, vinyl houses are often destroyed by strong winds or typhoons in summer. Many farmers suffer great economic damage from the collapse of vinyl houses. So it is very important to build a safe vinyl house and find a method to withstand this heavy wind load. In this study, a structural analysis was performed on four types of vinyl houses(10-single-4, 10-single-6, 10-single-7, 10-single-10). In addition, axial force and flexural moment are obtained from the structural analysis of four types of vinyl house. For these four types of vinyl house, structural safety was reviewed by obtaining the combined stress ratio by the strength design method. This structural review showed that the specifications for the vinyl house proposed in the design are not safe. Especially, the result of structural analysis for four types of vinyl house showed that the vinyl house structure constructed as a standard was a very dangerous structure. Therefore, it is necessary to devise diverse methods in order to make vinyl houses structurally safe for heavy wind load in the future. Also a variety of manual development is needed to prevent the collapse of vinyl houses at heavy wind load.

• Journal of fish pathology
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• v.34 no.2
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• pp.243-248
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• 2021

Offshore wind power generation is an energy generation field that is rapidly developing owing to the increasing demand for clean energy. However, the physiological response of fish to the underwater noise generated during construction or operation of wind turbines is unclear. We confirmed the effects of sound pressures of 125, 135, 145, and 155 dB/µPa, including 140 dB/µPa (the standard sound pressure for noise damage recognition in South Korea), through serum analysis in rock bream (Oplegnathus fasciatus). High mortality induced by reduced immunity through artificial infection after stimulation was confirmed. These results suggest that rock bream is negatively affected by the noise generated during the construction of offshore wind power plants.

• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.133-139
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• 2014

Offshore wind turbines have been constructed extensively throughout the world. These turbines are subjected to approximately $10^8$ horizontal load cycles produced from wind, waves, and current during their lifetimes. Therefore, the accumulated displacement of the foundation under horizontal cyclic loading has significant effects on the foundation design of a wind turbine. Akili(2006) and Achmus et al.(2009) performed cyclic triaxial tests on dry sands and proposed an empirical model for predicting the accumulated plastic strain of sands under long-term cyclic loading. In this study, cyclic triaxial tests were performed to analyze the cyclic loading behaviors of dry sands. A total of 27 test cases were performed by varying three parameters: the relative density of the sands, cyclic load level, and confining stress. The test results showed that the accumulated plastic strain increased with an increase in the cyclic load level and a decrease in the relative density of the sand. The confining stress had less effect on the plastic strain. In addition, the plastic strain at the 1st loading cycle was about 57% of the accumulated strain at 1,000 cycles. Finally, the input parameters of the empirical models of Akili(2006) and Achmus et al.(2009) were evaluated by using the relative density of the sand and the cyclic load level.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1764-1769
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• 2014

Numerical investigations have been conducted on the junction that connect the multi-tubular section and the single shell section in order to evaluate applicability of hybrid sections in wind turbine towers instead of conventional single shell towers. Major characteristics in structural details include extension of multi-tubular member into shell end section, installation of wing stiffeners, and different layout of floor beams. Elastic and nonlinear incremental analyses were conducted to examine stress concentration patterns and ultimate behaviors, respectively. Based on evaluation of structural performance due to vertical and horizontal forces, it has been confirmed that installation of floor beams and wing stiffeners sensitively affect ultimate strength of global wind tower.