Seung-Keon Lee

Shape optimization of an autonomous underwater vehicle with a ducted propeller using computational fluid dynamics analysis

ABSTRACT Autonomous Underwater Vehicles (AUVs) provide a useful means of collecting detailed oceano-graphic information. The hull resistance of an AUV is an important factor in determining the power requirements and range of the vehicle. This paper describes a procedure using Computational Fluid Dynamics (CFD) for determining the hull resistance of an AUV under development, for a given propeller rotation speed and within a given range of AUV velocities. The CFD analysis results reveal the distribution of the hydrodynamic values (velocity, pressure, etc.) around the AUV hull and its ducted propeller. The paper then proceeds to present a methodology for optimizing the AUV profile in order to reduce the total resistance. This paper demonstrates that shape optimization of conceptual designs is possible using the commercial CFD package contained in Ansys™. The optimum design to minimize the drag force of the AUV was identified for a given object function and a set of constrained design parameters

Mathematical Model for Dynamics of Manta-type Unmanned Undersea Vehicle with Six Degrees of Freedom and Characteristics of Manoeuvrability Response

Mathematical model for coupled motions of Manta-type Unmanned Undersea Vehicle(UUV) moving with six degrees of freedom, is formulated. Furthermore, a calculation method for estimating the linear hydrodynamic derivatives acting on UUV, is proposed, and some of the estimated linear hydrodynamic derivatives are compared with results of captive model experiment. Based on linear dynamic model of UUV, a study was made to examine dynamic stability and turning ability in horizontal plane. And directional stability and required elevation rudder angles for neutrally operating in vertical plane, are also discussed.⌌簀؀㘲〮㌻ጀ䝥湥牡氠䕮杩湥敲楮最

Experimental Study on Hydrodynamic Coefficients of Autonomous Underwater Glider Using Vertical Planar Motion Mechanism Test

Received 22 November 2013, revised 30 March 2014, accepted 10 April 2012 Corresponding author Seung-Keon Lee: +82-51-2441, leesk@pusan.ac.kr ◯c 2014, The Korean Society of Ocean Engineers It is noted that this paper is revised edition based on proceedings of KSOE 2013 in Seoul. Original Research Article Journal of Ocean Engineering and Technology 28(2), 119-125, April, 2014 http://dx.doi.org/10.5574/KSOE.2014.28.2.119

A Study on the Korea Marine Accidents and the Countermeasures

As the increase in maritime traffic and leisure, the marine accident risk has increased in the domestic coast. In this study, the cause and the environment of domestic marine accidents from 1990 to 2009 have been investigated and analyzed by using the statistics issues of Korean Maritime Safety Tribunal. Based on the analysis of most domestic marine accidents such as engine damage, collision, capsizing of small vessels, we propose how to use mobile telecommunication terminals for preventing marine accidents and the best countermeasures.

A Study on Changes in Appendage Design for Improvement of Dynamic Stability of Manta-type Unmanned Undersea Vehicle

Proposed Manta-type Unmanned Undersea Vehicle(UUV) turned out to have the tendency of dynamic instability in vertical plane, and moreover to have that of so strong dynamic stability in horizontal plane as to cause another problem in turning motion due to negative value of sway damping lever. The authors discussed the changes in appendage design for improvement of dynamic stability of UUV in vertical and horizontal planes. As a result, the dynamic stability in vertical plane was improved by increasing the area of horizontal stern planes. and the dynamic stability in horizontal plane was also improved by removal of lower vertical plate and by adjusting the area and position of upper vertical plate simultaneously.

The calculation of zig-zag maneuver in regular waves with use of the impulse response functions

Abstract The traditional governing equations for sway–yaw maneuvering motion are a set of ordinary differential equations with constant coefficients. But, as is well known, integro–differential equations with impulse response functions are more strict governing equations that can handle the frequency dependence of hydrodynamic forces. In this paper, the two types of equation are compared and used to calculate the 10°–10° zig-zag maneuver in waves. Differences between the solutions are discussed.

Trend and Review of Corrosion Resistant Alloy (CRA) for Offshore Pipeline Engineering

Offshore fields are increasingly important for the development of offshore resources due to the growing energy needs. However, an offshore field for oil and gas production has difficult development conditions, e.g., high temperature, high pressure, sweet/sour compositions of fluids, etc. Corrosion is one of the biggest issues for offshore pipeli ne engineering. In this study, a Corrosion Resistant Alloy (CRA) pipe for corrosion prevention was investigated through its global demand and trends, and three types of CRA pipelines were introduced with detailed explanations. The usefulness of CRA was also evaluated in comparison to a carbon steel pipeline in terms of the structural strength, cost, and other factors. Offshore pipeline engineering, including mechanical design and verification of the results through an installation analysis based on numerical software, was performed for the carbon steel type and solid CRA type. The results obtained from this study will be useful data for CRA pipeline designers and researchers.

CFD Simulations and Experimental Tests for Three Different Ducted Propellers

In this study, propeller open water characteristics (,  and ) were compared for three different ducted propellers using a Computational Fluid Dynamics (CFD) analysis, as well as an experimental test at a basin. The best shape of the duct was selected from the three types of specially designed ducts based on the CFD analysis results. The same propeller model (Kaplan type propeller) was used inside all three duct models, and the propeller open water characteristics were compared, predominantly at the design speed for an underwater vehicle. Finally, the results of the CFD test simulations for the selected duct case were verified by experimental open water tests in a towing tank.

Study on Parameters for Optimum Design of Integrated Subsea System

Abstract The mitigation of gap between technology and its applicability in the oil and gas industry has led to a rapid development of deepwater resources. Historically, subsea wells have good track records. However, an ever increasing water depths and harsher environmen ts being encountered are currently posing challenges to subsea pro duction. Complex subsea systems are now being deployed in ways rarely encountered in previous development schemes. These incre asingly complex systems present a number of technical challenge s.This study presents the challenges in subsea production systems , considering the technical and safety issues in design and ins tallationassociated with current development modality. Keywords: Subsea control system(SCS, 해저생산제어시스템), Subsea production system (SPS, 해저생산시스템), X-Tree(생산정), Well(유정), Umbilical(생산제어용 유체 공급라인), Subsea control module(SCM, 해저생산제어 모쥴), Fishing friendly structure(FFS, 해저설비보호구조) 1. 서 론 국제 에너지 기구(IEA, International Enery Agency)에 따르면 2010년 현재 일일 석유 생산량은 약 8천9백만 배럴이며 중국, 인도 등 신흥개발도상국의 빠른 경제 성장으로 인해 지속적인 에너지 수요 증가가 예상되고 있으나 2030년 일일 석유생산량이 약 1억배럴 수준으로 예측되고 있어 향후 전세계적인 에너지 공급 부족 현상이 발생할 가능성이 높아지고 있다. 현재 대체 에너지원으로 주목받고 있는 수소, 풍력, 태양열, 지열, 조력 등 신재생 에너지는 2035년까지 약 3배의 수요 증가가 예상(IEA World Energy Outlook, 2010) 되기도 하나, 연료 효율 및 막대한 초기투자비용과 유가 안정에 따른 정책적 지원 감소 등에 따른 영향으로 석유 수요에 영향을 미치기에는 상당한 시간을 필요로 할 것으로 예측되며, 원자력 또한 지난해 일본의 원전 사고 이후 위험 관리 측면에서 부정적인 평가를 받고 있어 과거 경제성 등을 이유로 보류되었던 심해 유전에 대한 개발 요구가 오히려 더욱 증가되고 있는 상황이다(Choi, 2008). 현재 심해 유전개발은 이미 2003년 ChevronTexaco사에서 Gulf of Mexico(GOM) Toledo 지역 최대수심 3052m까지 Drilling에 성공(Offshore, 2005) 함으로써 수심 3000m 시대를 열었으며, 현재도 높은 기술 수준과 Know-how를 보유한 선진 소수업체들이 독점적 위치에서 오일 메이저 업체들과 장기간 관계를 유지하고 있어 초기 기술이전 및 시장진입에 상당한 애로가 예상된다(Devegowa, 2003; Leffler, et al., 2003).심해저 생산 설비 시장은 향후 5~6년간 전 세계적으로 약 40조원의 규모로 예측되고 있으며 중국이나 인도의 경제 성장에 따라 오일 소비량은 더욱 확대될 것으로 예측되고 있다. 현재 일일 생산량 중 약 1천만 배럴 정도가 심해저에서 생산되고 있으며 육상이나 연안의 경우 이미 개발이 성숙단계에 진입하여 획기적인 생산량 증가가 불가능하기 때문에 심해저에 대한 개발 요구는 앞으로 더욱 확대될 전망이나, 국내의 기술력은 거의 전무한 상태이며 최근에서야 정부 주도의 신성장 동력 사업 및 국책과제로 해당 분야에 대한 기술개발이 추진 중인 상황이나 국내 기업의 시장 조기 진입을 위해서는 관련 기술의 체계적인 정리와 소개가 필수적이며 지속적으로 요구되는 시점이다.이에 본 연구에서는 2010년 BP사의 오일유출사건 조사 (Choi, et al., 2011)와 그 동안의 Subsea System에 대한 광범위한 조사와 설계 및 설치 경험을 바탕으로 해저 생산 및 제어 시스템의 특징 및 주요 구성 장비 소개와 설계시 고려되어야 할 요소에 대해 기술하고, 최적설계 수행 결과를 예시하였다. Vol. 49, No. 4, pp. 340-349, August 2012http://dx.doi.org/10.3744/SNAK.2012.49.4.340대한조선학회논문집Journal of the Society of Naval Architects of Korea

Subsea Responses to the BP Oil Spill in the Gulf of Mexico

On April 20, 2010, a well control event allowed hydrocarbon (oil and gas) to escape from the Macondo well onto Deepwater Horizon (DWH), resulting in an exploration and fire on the rig. While 17 people were injured, 11 others lost their lives. The fire continued for 36 hours until the rig sank. Hydrocarbons continued to flow out from the reservoir through the well bore and blowout preventer (BOP) for 87 days, causing an unprecedented oil spill. Beyond Petroleum (BP) and the US federal government tried various methods to prevent the oil spill and to capture the spilled oil. The corresponding responses were very challenging due to the scale, intensity, and duration of the incident that occurred under extreme conditions in terms of pressure, temperature, and amount of flow. On July 15, a capping stack, which is another BOP on top of the existing BOP, was successfully installed, and the oil spill was stopped. After several tests and subsea responses, the well was permanently sealed by a relief well and a bottom kill on September 19. This paper analyzes the subsea responses and engineering efforts to capture the oil, stop the leaking, and kill the subsea well. During the investigation and analysis of subsea responses, information was collected and data bases were established for future accident prevention and the development of subsea engineering.