The effect of loading conditions and ship speed on the wind and air resistance of a containership

Abstract

Although air resistance is relatively low in comparison to the total resistance of a ship, in the case of containerships, it can vary depending on the loading conditions and the layout of the stored containers. Over the years, containerships have increased in size and thus the air resistance has increased due to the increased windage area. The present study aims to assess the effect of different container configurations and trim on wind and air resistance as well as the influence of ship speed on air resistance. Numerical simulations based on viscous flow around a post Panamax 6750-TEU containership were conducted for open sea conditions. The verification studies for the grid size and time step were conducted and a validation study was performed using the available experimental results. The numerical results are reported with the non-dimensionalized wind load coefficients using the ITTC recommendations for the determination of the representative wind velocity. It is shown that the trim angle has the greatest influence on the moment coefficient, while the largest air resistance is obtained for the empty containership. The results also show that trim by bow causes lower values of air resistance, while trim by stern leads to higher values in comparison to an even keel condition. Finally, the portion of air resistance in the total resistance varies from 3.5% up to 5.8% for container configurations 9 and 2, respectively.