Recently, demands for reduction of added resistance by marine environment on ships are rapidly increasing in many shipping and/or shipbuilding companies to reduce operational cost and prepare regulations on the reduction of the greenhouse gas emission and enlarging CO2 emissions trading market. A fundamental step to minimizing added resistance is to estimate the vessel's added resistance appropriately. Therefore, the precise prediction of added resistance is of great importance for developing the high efficient and low fuel consuming vessel. The added resistance of ships is mainly caused by wind and waves. The wind resistance becomes more prominent in containership, tanker and LNG Carrier. In estimating added resistance due to wind, it is crucial to understand their characteristics and consider their corresponding effects accurately on the powering performance of a ship. Therefore wind measurement and correction have to be carefully carried out for accurate assessment of ship's speed performance.
In the shipping industry, there has been a growing awareness of weather effects on evaluating the powering performance of commercial ships since the EEDI has become mandatory technical measure for new ships by IMO. Estimation of the wind effect is important for the powering performance analysis and calculation of economical cost for energy efficient operation of the ships.
Ships meet various external forces during speed trials at sea caused by environmental conditions such as wind, waves, current, water depth, air temperature and water temperatures. For very large commercial ships the small wave height produces a negligible effect when compared to the added resistance caused by the wind (Fujiwara-Ueno and Ikeda, 2006). During speed trials, it is common that the wind speed and directions change significantly. Therefore, accurate and reliable onboard measurement of the wind speed and direction is essential for the evaluation of the wind resistance.
In this study, a number of wind measurements on foremast and radar mast for large container vessel, tanker and LNG carrier were performed during the sea trials. Also, the ultrasonic anemometer in addition to the ship's own anemometer was installed on radar mast to check the measurement quality from the different anemometers. Based on these measurements, the important wind parameters are investigated, such as the influence of the wind measurement locations, the characteristics of relative wind direction depending on ship headings, and fluctuation of true wind direction.
