Eun-Chan Kim

Development of the Ship Resistance Calculation Program for Prediction of Towing Forces for damaged Ships

Abstract − One of the primary purposes of tugs is for the towing of other ships in salvage operations. In orderto conduct such a task safely, the tug should be capable of generating the appropriate towing forces. Thereforethe prediction of resistance against a towed ship during towing operation is a very important and essential pro-cedure. This paper studies the ship resistance calculation program to predict towing force. The calculation pro-gram consists of the functions that calculate basic hull resistance in calm water, added resistance due to wind,drifting, hull roughness, waves, shallow water and currents. All predictions are calculated by statistical andempirical methods by graph or formula. The calculation results made by this program are compared with theresults from the U.S. Navy’s Towing Manual. These results confirm that this computer program is quite capableof appropriately predicting the resistance of damaged ships.Keywords: Salvage(구난), Towing Force(예인력), Prediction(추정), Hull Resistance(선체저항), Addedresistance(부가저항 ), Speed Loss(선속 감소)

A Study on the Hull Resistance Prediction Methods of Barge Ship for Towing Force Calculation of Disabled Ships

Abstract − Most of hull resistance prediction methods which are used to calculate the towing force of disabledships are very simple and old-fashioned. In particular, in cases of barge ships, a method similar to the US NavyTowing Manual is being used. This paper reviewed the US Navy Towing Manual and the notification method ofKorea Ministry of Oceans and Fisheries and proved that these prediction methods are irrational and inaccurate.Furthermore, a new Modified-Yamagata-Barge method is introduced as a more rational and accurate resistanceprediction method which can be applied in case of barge ships. Keywords: Disabled Ship(사고선박), Towing Force(예인력), Barge Ship(바지선), Hull Resistance(선체저항),Frictional Resistance(마찰저항 ), Residual Resistance( 잉여저항) 1. 서론 최근 5년간의 국내 선박의 사고 사례를 보면, 100톤 미만의 소형선박이 약 75%를 차지하며, 선종별로 분류하면 73%가 어선이고, 13%가 예선이나 바지선 등의 특수 소형선이므로 이들에 대한보다 정확한 추정 방법의 정립이 필요하다고 본다.사고 선박의 예인력을 추정하기 위해서는 사고선박 자체의 정수중 선체 저항과 각종 외력에 대한 부가저항, 그리고 여기에 예인삭의 침수부분 저항을 합쳐서 계산하게 된다. 정수중 선체 저항은선박의 침수 부분의 형상에 대한 저항으로, 가장 기본이 되는 저항 성분이다. 외력에 대한 부가저항은 바람, 표류력, 선체표면 거칠기, 선체 파손, 프로펠러 고착, 파랑, 천수효과, 조류 등을 들 수있는데[3], 그 크기는 거친 해상상태의경우정수중선체 저항값을 상회할 수도 있다. 예인삭 저항은 예인 방법에 따라 각각 발생하는 예인삭의 침수 부분 저항을 합산하여 구하게 되는데, 대부분의 경우 선체 저항의 10% 미만의 값으로서, 큰 비중을 차지하지는 않는다.본 논문에서는 바지선의 선체 저항값을 추정하는 기존의 방법들을비교하고, 합리적이고도 정확도가 높은 새로운 방법을 제시하고자한다.본 논문은 서로 다른 선체 저항 추정 방법을 비교하는 것으로서,각 방법에서 사용하는 기호와 단위를 그대로 쓰는 것이 적절하다고 판단하여 각각 원래의 기호와 단위를 표현하다 보니, 함께 묶는것이 도리어 혼란을 주므로, 기호와 단위 설명은 따로 모아 정리하지 않고 각각의 본문에서 설명하였다.

A Study on the Simplified Prediction Method of Air Resistance for Towing Force Calculation of Disabled Ships

− Ships sailing the seas encounter air resistance. The air resistance depends on the shape of the abovewater hull, the ship speed, the wind speed and wind direction. The experimental or statistical methods which are used to predict the air resistance are one of the essential procedures of the calculation of the towing force of the disabled ships. This paper shows simplified air resistance prediction method using the variables of the projected area of the above-water hull, the speed of the ship, the wind speed and its direction. These methods have been applied to the existing computer program which had been set up to predict the towing force of the disabled ships.

Development of Resistance Prediction Method for the Effect of Drifting Angle at the Towing Operation of a Disabled Ship

해상에서 사고선박을 예인하기 위해서는 파랑과 바람 등 각종 외력의 상태와 표류각 등 선체 자체의 상태에 대한 피예인선의 저항 증가를 정확하게 추정하여야 한다. 대부분의 사고 선박은 선체 정면 방향으로 예인되지 못하고 일반적으로 표류각 만큼 기울어진 상태로 예인된다. 이러한 표류각에 의한 저항 증가는 무시할 수 없는 정도이다. 본 논문에서는 기존의 각종 표류각에 의한 저항 증가 추정 방법을 고찰하였다. 또한 표류각에 대한 새로운 방법 즉 정면-측면 투영면적비율 방법과 다중회귀분석에 의한 경험식 방법을 도출하였다. 이 정면-측면 투영면적 비율방법은 예인상태 추정 프로그램에 적용되었고, 이 방법은 실제 상황에서 유용한 방법이라 확인되었다.Abstract − When a disabled ship is being towed in a seaway, the resistance increase of the towed ship caused byboth the external conditions such as wave and wind and the hull conditions such as drifting angle, should be accu-rately predicted. Most of the disabled ships cannot be towed in the front direction of hull, but they are usually towed indrifted direction with some drifting angle. In this sense, the resistance increase caused by the drifting angle is not anelement to be ignored. In this paper, various methods for prediction of the resistance increase caused by the driftingangle are studied. In addition, new prediction methods such as front-lateral projected ratio method and empiricalformula method by multiple regression analysis have been derived. The front-lateral projected area ratio methodhas been applied to a computer program for prediction of the towing condition, and this method has been approvedto be a useful method in practical situations.Keywords: Towed Ship(피예인선), Tug Boat(예인선), Resistance Increase(저항증가), Drifting Angle(표류각),Disabled Ship(사고선박)

Consideration on the environmental acceptability and biological effectiveness of the electrochemical disinfection system for ballast water management

This paper considers the matter of safety, environmental acceptability, practicability, and biological effectiveness for the electrochemical disinfection system, Electro-CleanTM. This electrochemical disinfection system uses various active substances produced from electrolysis of sea water. These active substances attack simultaneously an organism or organisms for disinfection so that synergy effect can be expected. Active substances are not added to the system but produced during electrolysis of sea water. Some of active substances with a lifetime in nanoseconds like as Hydroxyl Radical are not remain until to ballast tank in a ship. The other active substances remain in the ballast tank water and the discharge water but concentration of the active substances are not so high. So treated ballast water can be discharged into the environment without any conditioning. There are no waste streams that have to be disposed of and require special concern during the system operation. Biological efficacy tests are conducted for this electrochemical disinfection system. The biological efficacy of the Electro-CleanTM System was tested using marine organisms which consisted of three groups such as 10-50 mum, ges50 mum and bacteria .

Development of technologies on test facility and procedures for the land-based test as a type approval test at ballast water treatment system

The international convention for the control and management of ships ballast water & sediments was adopted at a diplomatic conference of IMO at 2004. Following to the Convention, fourteen guidelines were developed by IMO. The efficacy of ballast water management systems should be evaluated by administration in accordance with Guidelines for approval of ballast water management systems(G8). This guideline includes general requirements concerning design and construction, technical procedures for evaluation and the procedure for issuance of the type approval of ballast water management systems requires both land-based and shipboard testing. This paper considers the matter of facility and procedures for the land-based test as a type approval test. KORDI (Korea Ocean Research & Development Institution) is the designated Organization for land-based and shipboard testing for type approval of ballast water management systems in the Republic of Korea. When the testing body reviewed the various possibilities for the construction of a land-based test site, we found it not easy and very costly to pump sea water or fresh water containing high density of micro-organisms to an in-land test site. Therefore, it was decided to build a test barge dedicated for land-based tests. The barge was designed very similar to an actual ship with ballast tanks and its ballasting and de-ballasting method. The barge ship is composed of four 200 m3 tanks and a ballast water management system that is capable of pumping 300 tons of ballast water per hour with each pipe. A blower system is installed for the cleaning of the sampling tanks. There are four tanks of 2 m3 to control the dosage and each tank has an attached output valve to allow the possibility of sampling.

Development of Prediction Program of Added Resistance Due to Waves at the Towing Condition of a Disabled Ship Using ISO 15016 Analysis Method

해상에서 사고선박을 예인할 때 피예인선의 저항을 추정하는 것은 중요한 과정의 하나이다. 피예인선에는 선체 자체의기본 저항 외에 각종 부가저항이 있는데, 가장 큰 성분중의 하나로 파랑에 의한 부가저항을 들 수 있다. 본 논문에서는ISO 15016 표준의 이론해석 방법에 의해 사고 선박 예인시 파랑중 부가저항을 추정하는 알고리즘을 정립하고, 이를 전산 프로그램으로 구현하였다. 예제 선박의 계산 결과를 기존의 표준 결과와 비교하였고, 이 알고리즘과 전산 프로그램은 실제로 사고 선박의 저항과 이에 따른 예인력 추정시 사용하기에 적절한 것으로 판단되었다.Abstract − It is one of the important processes to predict the resistance of the towed ship when towing a disabledship on the sea. Besides the basic resistance of hull itself, there are various added resistance, especially the addedresistance due to waves can be considered one of the biggest component. In this paper, the algorithm which predictthe added resistance due to waves of a disabled ship by theoretical analysis method of ISO 15016 standard wasestablished, and realized as a computer program. The calculated result for an example ship was compared withexisting standard one, and it is considered that this algorithm and computer program are appropriate to use for pre-dicting the resistance and towing force of the disabled ship actually.Keywords: Added Resistance(부가저항), Towed Ship(피예인선 ), Wave(파랑), Wind Wave(풍파), Swell(너울)

Development of Prediction Program for the Towing Condition Associated with Various Towing Operations of a Disabled Ship

− When a disabled ship is being towed in a seaway, the speed and direction of the towed ship are estimated by using the towing force and direction of the selected tug boats at the predicted sea conditions including the wind and currents. In this paper, prediction method at the towing conditions of the various towing operations for a disabled ship are studied. The proposed calculation method suggests firstly the method to import the speed and resistance of the forward direction of the towed ship calculated by the existing computer program, second, the method to calculate the speed and resistance of the towed direction of the towed ship acquired from the selected tug boats at the initial towing conditions and lastly, the method to calculate the speed and resistance of the towed direction for the towed ship at the stable towing conditions. These calculation methods have been applied to the computer program and this program has been approved to be a useful program, capable of appropriately predicting the towed ship’s conditions.

Analysis method and the related computer program to predict the towing condition of a towed vessel using multiple tugboats and pushers

When towing a disabled vessel using one or multiple tugboats and/or pushers, it is important to estimate the direction and speed of the towed vessel, and the towing forces of tugboats and/or pushers each. This paper studies the prediction methods of hull resistance in calm water and added resistance due to external forces, that is, wave, wind, drifting, hull roughness, propeller locking and shallow water effect for the towed vessel. Although it is good to use the value of a model test results for hull resistance in calm water, as it takes a lot of cost and time, statistical analysis method was used. Various empirical methods including KRISO regression formulae were adopted to predict the hull resistance in calm water. For added resistance due to external forces, ISO 15016:2002 method was adopted for the added resistance due to waves, JTTC and Blendermann Chart were done for the added resistance due to wind, SR208 and KRISO method were done for the added resistance due to drifting, ITTC-78 method was done for the added resistance due to hull surface roughness, USCG Towing Manual method was done for the added resistance due to propeller locking, and Lackenby method was done for the speed loss due to shallow water effect. Also, in this paper, the towing position, direction and force of tugboats and/or pushers were defined, whereby how to calculate the towing force and yawing moment on the towed vessel was established. And then, by finding out the state where the sum of towing force of the forward direction of tugboats and/or pushers and the whole resistance of the towed vessel become the same, and the stable state where the sum of the yawing moment of tugboats and/or pushers becomes 0, the method of estimating the forward direction and velocity of the towed vessel was established. All of these analysis methods were made into a computer program, and especially by providing GUI environments, they were made easy for users to use. If the program developed through this paper is used, it is considered that the situation of towing the disabled vessel could be quickly and exactly simulated in advance in the real salvage site.

Establishment of Integrated Information System for Ballast Water Management

Collection and management of various information related to the ballast water are the essential compo- nents for the efficient implementation of the IMO Ballast Water Management Convention. Based upon the ballast water risk assessment and information system developed by other states, regions or even at global level, an inte- grated information system has been established to be applied to our domestic ports. The integrated information sys- tem is composed of four DataBases (DB) which are the Shipping DB, Ballast water DB, Port Environment DB and Species DB. The Shipping DB has been established based on the data collected from the Port Management Infor- mation System (Port-MIS). For the Ballast water DB, Ballast water has only been estimated by the loading/unload- ing of the cargoes as the convention has not come into effect yet. The Port Environment DB and Species DB are being established based on the reference documents and existing and newly collected monitoring data. From these DB, the integrated information system will be able to provide a base for the information search, statistic analysis and risk assessment of ballast water. Once the convention comes into effect, this integrated information system will be applied to manage the domestic ballast water discharge and also the port management.