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원형 실린더 주위의 유동해석을 통한 URANS 난류 모델 성능 비교
김민재,신지환,권래언,이건철,Kim, Minjae,Shin, Jihwan,Kwon, Laeun,Lee, Kurnchul 한국군사과학기술학회 2014 한국군사과학기술학회지 Vol.17 No.6
In the present study, the flow around a circular cylinder at $Re=3.6{\time}10^6$ is numerically simulated using URANS approach. The objective of this study is to evaluate the turbulence models(Realizable k-${\varepsilon}$, RNG k-${\varepsilon}$) through the prediction of the unsteady flow characteristics around the cylinder. The time-averaged drag coefficients and vortex shedding phenomenon in the wake region are compared to available experimental data and other numerical results. The simulation with Realizable k-${\varepsilon}$ model is found to be more dissipative due to large eddy viscosity predicted in the wake region while the simulation with RNG k-${\varepsilon}$ model predicts a complex vortex shedding phenomenon with more coherent structures realistically.
복합임무 무인수상정의 개발시험평가 및 검증절차에 관한 고찰
박신배(Shin-Bae Park),김원제(Won-Jae Kim),이건철(Kurnchul Lee) 한국해양공학회 2018 韓國海洋工學會誌 Vol.32 No.5
This paper describes the plan and procedure of a development test and evaluation that will be performed to verify the performance and technology of multi-mission unmanned surface vehicles (MMUSVs). In order to verify the design requirement of MMUSVs, we designed and manufactured the common platform of MMUSVs, which have an overall length of8.4 m, a displacement of 3,100 kg, and a speed of more than35 kts. The platform is equipped with several sub-systems, including radar and an EOTS/IRS. The EOTS/IRS, along with the search radar, is used for effective detection, identification, and targeting. The core technologies of MMUSV for DT&E will be investigated. The common platform design technologies, remote operating and control system technologies, autonomous navigation technologies, and unmanned operational technology of sensors and equipment will be studied for the development of the MMUSV’s core technologies. The system will be able to make precise observations and track targets both manually and automatically during day and night conditions. Currently, the verification tests for each of the technologies and for the integrated system are in the pipeline for DT&E, which will be performed next year. Also, software reliability and life tests will be performed.
포텐셜함수 기반 초공동 수중운동체 플레이닝 회피 제어 연구
김선홍(Seonhong Kim),김낙완(Nakwan Kim),김민재(Minjae Kim),김종혁(Jonghoek Kim),이건철(Kurnchul Lee) 한국해양공학회 2018 韓國海洋工學會誌 Vol.32 No.3
In this paper, we focus on planing avoidance control for a supercavitating underwater vehicle based on the potential function method. The planing margin can be calculated using the relative position between the cavity center and vehicle center at the end of the vehicle. The planing margin was transformed into a limit variable such as the pitch angle and yaw angle limit. To prevent the vehicle attitude from exceeding the limit variable, a potential function based planing envelope protection method was proposed. The planing envelope protection system overrides commands from the tracking controller, and the vehicle attitude converges to a desired angle, in which the potential function is minimized. Numerical simulations were performed to analyze the physical feasibility and performance of the proposed method. The results showed that the proposed methods eliminated the planing, allowing the vehicle to follow tracking commands.