CFD Analysis of Flow Fields under Bow Bottom of Ships in Full-Scale

Ship's speed through water is one of the most important factors in the energy efficiency evaluations of ships in operation. Recently ship performance monitoring systems are being installed in the wide variety of ships for efficient operations and ship's speed through water is usually measured using the Doppler speed log system. The measuring accuracy of the Doppler speed log systems, however, may not be sufficient for the evaluations of various energy-saving measures since the measuring locations are 3 to 20 meters below the bow bottom of ships where the water speed may be affected by the local disturbances of a ship hull. In this study, in order to investigate the properties of velocity distributions under bow bottom of ships, the flow fields of full scale ships are simulated using CFD approach. The computed results for a blunt ship and a slender ship in laden and ballast conditions with various ship speeds are presented. It is shown that the properties of the disturbance velocity due to a ship hull depend on ship's draft and ship speeds differently with a ship type.