• Wind and Structures
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• v.30 no.4
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• pp.433-450
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• 2020

The strong turbulence characteristic of typhoon not only will significantly change flow field characteristics surrounding the large-scale wind turbine and aerodynamic force distribution on surface, but also may cause morphological evolution of coast dune and thereby form sand storms. A 5MW horizontal-axis wind turbine in a wind power plant of southeastern coastal areas in China was chosen to investigate the distribution law of additional loads caused by wind-sand coupling movement of coast dune at landing of strong typhoons. Firstly, a mesoscale Weather Research and Forecasting (WRF) mode was introduced in for high spatial resolution simulation of typhoon "Megi". Wind speed profile on the boundary layer of typhoon was gained through fitting based on nonlinear least squares and then it was integrated into the user-defined function (UDF) as an entry condition of small-scaled CFD numerical simulation. On this basis, a synchronous iterative modeling of wind field and sand particle combination was carried out by using a continuous phase and discrete phase. Influencing laws of typhoon and normal wind on moving characteristics of sand particles, equivalent pressure distribution mode of structural surface and characteristics of lift resistance coefficient were compared. Results demonstrated that: Compared with normal wind, mesoscale typhoon intensifies the 3D aerodynamic distribution mode on structural surface of wind turbine significantly. Different from wind loads, sand loads mainly impact on 30° ranges at two sides of the lower windward region on the tower. The ratio between sand loads and wind load reaches 3.937% and the maximum sand pressure coefficient is 0.09. The coupling impact effect of strong typhoon and large sand particles is more significant, in which the resistance coefficient of tower is increased by 9.80% to the maximum extent. The maximum resistance coefficient in typhoon field is 13.79% higher than that in the normal wind field.

• Strategy21
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• s.37
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• pp.5-31
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• 2015

The Republic of Korean Navy (ROKN) started from scratch. However, ROKN demonstrated its Blue Navy capabilities successfully to the entire world by conducting "Operation Early Dawn" at the Aden Bay, Yemen in Jan 2011. On the event of the 70th anniversary of the ROKN, I would like to retrospect past gleaning from voyages and challenges we had in the past. At the very inception of the ROKN, Korean government as well as senior military leaders recognized that it had no time to spare to clean up military those were insinuated deeply by communist agents. It was the top priority of the government. The Mongumpo Operation which was not well known, conducted by ROKN was one of the clean-up drive. The Korean War sometimes called as "a fire from land put-off at the sea". The world famous "Incheon Landing" which reversed war situation from the Nakdong Perimeter also done by Sea Power. ROKN conducted various maritime operations including not only Incheon Landing, but amphibious operation at Hungnam, mine sweeping, sea convoy, Wonsan Withdrawal. On the same day of the Korean War started, 25th June 1950, unless the victory of the ROKNS Baekdusan (PC 701) at the Korean Strait, the waning lamp light of Korea could not be rekindled by the participation of the U.N. The ROKN rescued the 17th regiment of Korean Army from the isolation at the Ongjin Peninsular and transported gold and silver bars stored at the Bank of Korea to the Navy supply deposit in Jinhae safely. ROKN special intelligence unit conducted critical HUMINT which led Incheon Landing success. One of important mission ROKN conducted successfully was not only transporting war fighting materials but also U.S. provided grains to starving Koreans. ROKN participated Vietnam campaign from 1960s and conducted numerous maritime transportation operations supplying materials to Vietnam military forces along the long coastal lines. Experienced Naval Officers and enlisted men who discharged and acquired as merchant marine certificate supported most of the U.S. sea lift operations throughout the Vietnam campaign. ROK-US Combined Forces which had been honed and improved its war fighting capabilities through the Korean War and out of Vietnam jungle playing key deterrent against threat from north Korea. However, those threat level will be completely different when north Korea finish its nuclear weapon ambition. In order to stand firm against north Korean nuclear threat, I would like to expect strong political leadership supporting nuclear submarine for ROKN.

• Journal of Korean Society of Steel Construction
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• v.17 no.4 s.77
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• pp.499-509
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• 2005

The excessive wind-induced motion of tall buildings most frequently result from vortex-shedding-induced across-wind oscillations. This form of excitation is most pronounced for relatively flexible, lightweight, and lightly damped high-rise buildings with constant cross-sections. This paper discusses the aerodynamic means ofmitigating the across-wind vortex shedding induced in such situations. Openings are added in both the drag and lift directions in the buildings to provide pressure equalization. Theytend to reduce the effectiveness of across-wind forces by reducing their magnitudes and disrupting their spatial correlation. The effects of buildings with several geometries of openings on aerodynamic excitations and displacement responses have been studied for high-rise buildings with square cross-sections and an aspect ratio of 8:1 in a wind tunnel. High-frequency force balance testshave been carried out at the Kumoh National University of Technology using rigid models with 24 kinds of opening shapes. The measured model's aerodynamic excitations and displacement were compared withthose of a square cylinder with no openings to estimate the effectiveness of openings for wind-induced oscillations. From these results, theopening shape, size, and location of buildings to reduce wind-induced vortex shedding and responses were pointed out.

• Archives of design research
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• v.19 no.1 s.63
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• pp.293-302
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• 2006

clay cups with handles made in studios in Korea and the United States were selected and analyzed. The shape of cup were fixed to ensure proper comparison between handle size of the cup and position. The variable factors were the thickness of the handle, the number of fingers required to hold the cup, the relationship between the handle's shape and the position of its attachment to the cup, the effect of the handle's setter, the change in shape of the handle's thickness, and the relationship between the cup's weight center and handle. Preference test were designed and tested to the users, and the results were analyzed. The results showed that to make a comfortable handle, it is important to incorporate the shape of the resting hand in the design of the handle. Specifically, the design should be such that the cup can be held comfortably. This is possible if the weight of the cup is spread evenly when several fingers are inside the handle's curve and if such factors as the hand size, the curve of the fingers, and the position that best controls the cup's weight center are carefully considered. At this time, if there is a setter for the thumb, a cup of the same weight can be lifted more lightly. In the design of such a cup, the oval line is drawn by extending the cup's handle toward the direction of the cup's body. If the cup's weight center is located on the oval line, the cup's handle may be said to be effective. In such a case, the nearer the handle is to the cup's body weight center, the less power is needed to lift the cup efficiently. Our test results can be applied as a powerful tools in design and manufacturing cups with handle in terms of artistry and functionality.