Estimation of Added Mass and Radiation Damping of Large Ocean Observation Buoy Using Numerical Analysis

Kim, D.; Shim, J.-S.; Min, Y.; Min, I.K., and Lim, H.S., 2021. Estimation of added mass and radiation damping of large ocean observation buoy using numerical analysis. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 221–225. Coconut Creek (Florida), ISSN 0749-0208. A vane is to be installed to control the yawing behavior of a large ocean observation buoy (LOOB). The role of the vane is to control the yaw motion of the one-point mooring LOOB against current and waves. The lengths of the vanes were 0.8, 1.6, and 2.0 m, and the added mass tensor (6 × 6) and radiation damping tensor (6 × 6) at that time were estimated using computational fluid dynamics. In addition, the added mass tensor and radiation damping tensor according to the wave frequency domain are presented. Estimating the added mass and radiation damping of LOOB is important because it presents the hydrodynamic relationship between the structure and fluid. As a result of the analysis, the added mass was almost unchanged in other components except m66. On the other hand, m66 was proportional to the length of vane. When the length of the vane is 0.8 m, the maximum added mass is 1.28 × 104 kg (wave frequency 3.7 rad/s), and when the lengths are 1.6 and 2.0 m, it increases to 2.79 × 104 and 3.58 × 104 kg, respectively. This means that the length of the vane affects the resistance to rotational motion. In the case of radiation damping, the results were that the length of the vane and the radiation damping (component c66) were proportional. However, there is no significant difference depending on the length of the vane in the other components (c11 to c55). Radiation damping (c66) increased to 1.12 × 104, 3.56 × 104 and 4.46 × 104 kg, according to the length of the vane. In conclusion, it can be seen that the longer the vane, the better the yaw control effect. However, as the length of the vane increases, the geometric asymmetry of the LOOB increases. In addition, it can be cause fatal damage to small boats berthing the LOOB. Therefore, it is necessary to optimally design it by considering the advantages and disadvantages according to the length of the vane.