Study on the Estimation Method of Wind Resistance Considering Self-Induced Wind by Ship Advance Speed

Abstract

A numerical analysis of the wind load for the purpose of evaluating the wind resistance acting on a ship and the validity of the wind profile applied to determine the wind load coefficient were conducted. Through the evaluation of estimation results by a wind tunnel test, CFD analysis, and present semi-empirical formulae, it was recognized that the difference in estimation of ship resistance due to wind could not be ignored. In order to identify the main causes of the difference, extensive analyses were performed for a container, tanker, and LNG carrier. In particular, the estimation results for a container ship with two islands showed unreliable results. The main reason for the difference is that each method reflects the wind speed in the vertical direction differently, and the wind profile applied when considering the self-induced wind effect is not a uniform wind profile. In the calculation of wind resistance by self-induced wind, wind resistance estimation results differed by about 1.5% to 3.4% depending on the application of uniform or non-uniform wind profile. The total wind resistance acting on the vessel shall be divided into wind resistance from a stationary vessel without speed and wind resistance caused by the forward speed of the vessel in no wind conditions. Therefore, it is reasonable to apply a uniform wind profile to estimate wind resistance caused by the ship’s forward speed, while a wind profile that reflects the effect of changes in the ship’s vertical speed should be applied to estimate the wind resistance caused by the ship’s forward speed.

Keywords

• wind load coefficient
• uniform wind profile
• self-induced wind
• numerical analysis