Abstract
In this study, the hull form optimization process to minimize resistance of KCS (KRISO containership) at Fn=0.26 is described. The bow hull form of KCS was modified by varying such design parameters as sectional area curve (SAC), section shape, bulb breadth, and bulb height using multiple parametric modification curves devised by the authors. The resistance performances of modified hull forms were analysed by the viscous flow Reynolds-Averaged Navier–Stokes (RANS) solver of WAVIS ver.2.2. With a view to saving computational time during iterative analyses in the optimization process, the sinkage and trim were set to the fixed values which had been obtained for the original hull form with free condition. The validity of such constant sinkage/trim was then verified by conducting analysis for the optimal hull form with free condition. Optimization to minimize the cost function of the total resistance coefficient of model CTM was performed by sequential quadratic programming (SQP), which is one of the gradient-based local optimization methods. Utilization of parallel computing led to the simultaneous calculation of the gradient, thereby speeding up the whole optimization process. At the design speed of 24 knots, the optimal hull yielded CTM reduction by 1.8%, which is extrapolated to 3.1% reduction of effective power PE in full scale.
Highlights
With a view to reducing the greenhouse gas (GHG) emission from newly built ships, the International Maritime Organization (IMO) established the Energy Efficiency Design Index (EEDI) regulation, which mandates stepwise reinforcement of GHG emission allowance every five years
Compared to the conventional parametric modification function presented in Kim et al [16] and Kim [42], this method has the advantages in terms of improved fairness and constraint satisfaction under wider range of hull form variation
The present study is aimed at combining such cutting-edge hull form modification method with free-surface Reynolds-Averaged Navier–Stokes (RANS) solver to present an example of hull form optimization study which is readily applicable in industry
Summary
With a view to reducing the greenhouse gas (GHG) emission from newly built ships, the International Maritime Organization (IMO) established the Energy Efficiency Design Index (EEDI) regulation, which mandates stepwise reinforcement of GHG emission allowance every five years. Compared to the conventional parametric modification function presented in Kim et al [16] and Kim [42], this method has the advantages in terms of improved fairness and constraint satisfaction under wider range of hull form variation. The present study is aimed at combining such cutting-edge hull form modification method with free-surface RANS solver to present an example of hull form optimization study which is readily applicable in industry. Toward this end, the present study carried out an optimization study for forebody hull form of KCS (KRISO containership). The CTM was extrapolated to full scale effective power PE by the 2-D extrapolation of the ITTC 1978 performance prediction method
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