CFD-BASED SIMULATION OF THE FLOW AROUND A SHIP IN OBLIQUE MOTION AT LOW SPEED

Ships tend to maneuver in oblique motion at low speed in situations such as turning in a harbor, or during offloading, dynamic positioning and mooring processes. The maneuverability criteria proposed by IMO are valid for ships sailing with relatively high speeds and small drift angles, which are inadequate to predict ship maneuverability in low speed condition. Hydrodynamic performance of ships maneuvering at low speed is needed to know for safety issues. A CFD-based method is employed to predict the flow around an Esso Osaka bare hull model in oblique motion at low speed, where the drift angle varies from 0 degrees to 180 degrees. The URANS method with the SST k-omega model is used for simulating ship flows with drift angles 0 degrees similar to 30 degrees and 150 degrees similar to 180 degrees, and DES method for simulating ship flows with drift angles 40 -150. Verification and validation studies are conducted for drift angles of 0 degrees and 70 degrees. The vortex structures at typical drift angles of 0 degrees, 30 degrees, 50 degrees, 70 degrees, 90 degrees and 180 degrees are analyzed. The effects of drift angle and ship speed are demonstrated.