https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/59 2026-05-04T21:37:57Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/392 Title: 유입 유동의 가속도가 2D 원형실린더의 항력 및 후류에 미치는 영향 Authors: 손현아; 이승수; 조성락 Abstract: Computational studies of accelerating flow around 2D Circular Cylinder was performed to investigate characteristics of wake field and drag forces. Previous studies had revealed that drag on the cylindrical body in accelerating flow is much greater than that in the flow with constant velocity; however, the underlying physics on the drag increase has not been clearly investigated. In order to investigate the drag increase and its relationship with wake development, this study employed a finite-volume based CFD code, Fluent 13.0 with ？ ？ ？ SST model for turbulence effects. Inflows are modeled with varied accelerations from 0.4905 to ？？？？ ？？？？. The drag computed in the present study is in good agreement with previous studies, and clearly shows the increase compared to the drag on the body in the flow with constant velocity. The results also show that drag crisis observed at high Reynolds number in the case of the flow with constant velocity is also found in the case of accelerating flow. The analysis for wake and recirculation length shows that conventional vortex shedding does not occur even at high Reynolds number and the drag increase is larger at higher acceleration. 2019-01-01T00:00:00Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/391 Title: 극지용 도료의 빙마찰 및 빙마모 시험기법 연구 Authors: 조성락; 오은진; 김철희; 이재만; 김성표 Abstract: This study describes a test method for evaluating the ice friction and abrasion performance of polar coatings. The evaluation methods of physical properties of general coatings for ocean-going vessels and polar coatings for ice-going vessels were investigated and their limitations were analyzed. We have also reviewed previous researches related to the development of polar paints and confirmed the necessity of developing test techniques. A flat steel plate was coated with several types of commercial coating, and cold model ice was used to cause ice friction and abrasion events between coated surface and ice. For evaluation of ice friction and abrasion performances, test procedures such as measurement of coating surface roughness, measurement of frictional force using model ice, implementation of ice abrasion and drying of coating surface were developed. The friction and abrasion characteristics of each coating are analyzed and summarized through the change of friction force and roughness data according to the progress of ice abrasion. 2019-01-01T00:00:00Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/600 Title: 쿼드트리 분할영상의 국부이진화를 통한 팩아이스 집적도 측정 알고리즘 Authors: 이정훈; 변석호; 남종호; 조성락 Abstract: Recently, many research works on the icebreaking vessels have been published as the possibility of passing Arctic routes has been increasing. The model ship test on the pack ice model in the ice basin is actively carried out as a way to investigate the performance of icebreaking vessels. In this test, the concentration of pack ice is important since it directly affects the performance. However, it is difficult to measure the concentration because not only the pack ice has uneven shape but also it keeps floating around in the basin. In this paper, an algorithm to identify the concentration of pack ice is introduced. From a digital image of pack ice obtained in the ice basin, the goal is to measure the area of pack ice using an image processing technique. Instead of the general global binarization that yields numerical errors in this problem, a local binarization technique, coupled with image subdivision based on the quadtree structure, is developed. The concentration results obtained by the developed algorithm are compared with the manually measured data to prove its accuracy. 2017-01-01T00:00:00Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/795 Title: 모형빙 밀도 계측 방법 개선 연구 Authors: 하정석; 강국진; 조성락; 정성엽; 이춘주 Abstract: The Korea Research Institute of Ships & Ocean Engineering (KRISO) has an ice tank to make a test environment similar to the real icein the polar sea in order to carry out model tests. One of the most important task of the ice tank is to generate the model ice to havesimilar material properties as sea ice. The primary properties of sea ice which influence the ice performance of ice breakers andice-strengthened vessels traveling in the polar sea are ice thickness, flexural strength, density, modulus of elasticity and crystalstructure etc. Among them, since the density of model ice influences the buoyance resistance of ice for the ship model, the accuratemeasurement of ice density should be used to obtain the accurate analysis results from the model test. In this paper, some existingmethods to measure the density of model ice are reviewed and a new one is proposed to measure it accurately and easily as possible. In this study, the measuring system including an UTM and several measuring devices was established to obtain the model ice density. Polyethylene and ice specimens are used for a series of repeatable measurement tests. From the results, it was recognized that bothof the displacement method and the weight/weight methods gave the stable and favorable tendency. 2015-01-01T00:00:00Z