International Maritime Organization (IMO)'s recent Energy Efficiency Design Index (EEDI) regulation for new ships has increased interests in ship efficiency. As a results ship added resistance is one of the key consideration in designing a highly efficient ship and many experiments and numerical methods are conducted to predict the added resistance. In this study the motion response and the added resistance of the LNG carrier in head waves were computed using the commercial computational fluid dynamics (CFD) code Star-CCM+. Unsteady Reynolds Averaged Navier-Stokes equation (RANS) was numerically solved and the volume of fluid (VOF) approach was used to simulate the flows. The wavelengths varied from half the ship length to twice the ship length and the design speed was selected for the velocity. The heave and pitch motions were calculated along with the added resistance and the wave contours were obtained. Several grid tests were conducted to achieve the converged motion and resistance values. The calculated results were compared and validated with the experimental results.
International Maritime Organizations (IMO) has released Energy Efficiency Design Index (EEDI) regulation recently. This regulation caused ship building companies to build more efficient ships and to achieve this goal, reducing added resistance became necessary. Accurate prediction of the added resistance of the ship is needed since it could give variety of information about the efficient hull shapes. As a results, predicting added resistance became one of the highly interested domain in seakeeping problems.
Traditionally, potential based numerical methods and experimental studies are applied to predict the added resistance more correctly. Seo et al. (2014) predicts the added resistance with potential based methods and Lee et al. (2016) investigated the added resistance by model tests. However, potential based methods have limitations since it has difficulty in considering the nonlinear effects and the viscosity effects. Experiments are desirable and needed, but the expenses are rather expensive than the computational methods.
Nowadays, development of computers gave rise to new field called Computational Fluid Dynamics (CFD). CFD has gained interests since it could consider nonlinear effects and viscous effects. Nonlinear effects are especially important for short wavelengths and the viscous effects are more realistic than the inviscid model. However, the computation time is still a major issue in CFD since most of the simulation still needs a lot of computation time compared to the potential based methods. Many studies have been made using CFD methods. Sadat-Hosseini et al. (2013) compared the motion and added resistance of the KVLCC2 and Tezdogan et al. (2015) estimated the added resistance of the KRISO Container Ship (KCS) by using full scale model with commercial code, Star-CCM+. Yang et al. (2015) applied Cartesian-grid-based method to the added resistance calculation. Also, Yang and Kim (2017) predicted added resistance in short waves for the hull with several different bow shapes using CFD and showed promising results.
In this study, CFD method was used to analyze the motion and the added resistance of a given ship with head sea conditions. As CFD results are very dependent on generated grids, several tests are done on mesh generations to show the convergence of the results. Also, calculated results are validated with the experimental results. Finally, wave contours and time signals obtained are shown and analyzed.
