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Results
Computation On Added Resistance Based On Near-Field And Far-Field Methods
Seo, Min-Guk (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Park, Dong-Min (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Kim, Kyong-Hwan (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Kim, Yonghwan (Department of Naval Architecture and Ocean Engineering, Seoul National University)
ABSTRACT This paper presents a comparison of the computation results of added resistance on ships in waves. Recently, the design of ships with less green-house gas is one of great interest in naval architecture fields. Ship designers need to find optimum hull forms with minimum resistance in ocean waves. Therefore, an accurate computation of added resistance is getting more important for the prediction of power increase on ships in random ocean waves. This study focuses on the numerical computation of added resistance in different methods. To calculate added resistance on ships in waves, three different methods are considered. One is a direct pressure integration method, another is a momentum conservation method, and the other is a radiated energy method. The direct pressure integration method and the momentum conservation method are combined with a higher-order Rankine panel method, and the radiated energy method and the momentum conservation methods are combined with the strip method. The computational results are validated by comparing them with experimental data on Wigley hull models, Series 60 hulls, and S175 containership. Reasonable agreements are observed for all the models. The study is also extended to the analysis of added resistance in short wave range. To complement the results of added resistance in short wave, the established asymptotic calculation methods are examined. INTRODUCTION When a ship navigates in waves, the ship's forward speed decreases compared to that in calm sea because of the added resistance. It is reported that the magnitude of added resistance is about 15–30% of a calm-water wave resistance (Arribas, 2007). An accurate prediction of added resistance, therefore, is important in the design of a ship with propulsion power. Moreover, in recent years, discussions at International Maritime Organization (IMO) have resulted in the development of an Energy Efficiency Design Index (EEDI) to measure how much green-house gas a ship emits per unit transport provided and to restrict green-house gas emissions from ships.
- Transportation > Marine (1.00)
- Transportation > Freight & Logistics Services > Shipping (0.69)
Study On the Effect of Density Ratio of Liquid And Gas In Sloshing Experiment
Ahn, Yangjun (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Kim, Sang-Yeob (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Kim, Kyong-Hwan (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Lee, Sang-Woo (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Kim, Yonghwan (Department of Naval Architecture and Ocean Engineering, Seoul National University) | Park, Jong-Jin (Samsung Heavy Industry)
ABSTRACT: This paper presents the results of the sloshing experiments having fluids in a model tank with various density ratios. The experimental modeling is performed with mixed gas of sulfur hexafluoride (SF6) and nitrogen (N2), because the modeling consisting water and air is not considered representative enough to estimate sloshing pressure in an actual LNG cargo tank. Two-dimensional model and 1/50-scale three-dimensional model tank have been manufactured, and three different filling levels are considered with the irregular motions. Each condition has five different density ratios using different composition of gas. The decrease of sloshing pressure is predicted when the density ratio increases. INTRODUCTION Sloshing in LNG carriers can lead to large impacts on the containment system. It is important to assess these impact pressures and forces for adequate design of containers. Because of stochastic character of sloshing, experimental analysis is mainly recommended by ship classification societies (ABS, 2006; DNV, 2006). An experimental system for sloshing has been settled down in Seoul National University (SNU) to predict pressure impacts (AMEC, 2010). Dimensionless numbers for this application have been studied, but none of them have drawn a complete conclusion. Global behavior of the fluids is governed by the Froude number, so the ullage pressures should be Froude scaled (Bass et al., 1980). The local behavior, however, needs another scaling law. To find out appropriate scaling law for local phenomenon of sloshing, analytic, numerical (Braeunig et al., 2009), and experimental studies have been conducted. Acoustic scaling including the density ratio has been theoretically identified, which is to be relevant as well as Froude scaling to the sloshing problem (Dias et al., 2007). During the impact, transfer of momentum between liquid and gas is occurred, so the den density ratio has an influence on the impact pressure.
- Europe (0.68)
- North America > United States (0.28)
- Asia > South Korea > Seoul > Seoul (0.25)
- Research Report > New Finding (0.86)
- Research Report > Experimental Study (0.54)
- Energy > Oil & Gas > Midstream (1.00)
- Transportation > Freight & Logistics Services > Shipping > Tanker (0.34)