Numerical Study on Characteristics of Separated Flows around an Extremely Blunt Ship with and without a Stern Tunnel

Abstract

A novel ship concept which is called ULBS (Ultra Large Block coefficient ship) to reduce CO2 emission form sea transportation is under investigation at Yokohama National University. Since ULBS is supposed to have a very blunt hull and use of various flow control devices are essential for better hydrodynamic performance, flow field analysis around a ship is crucial for a design of ULBS. Computational Fluid Dynamics (CFD) is expected to be an efficient design tool for unconventional hull forms such as ULBS. To investigate the flow characteristics of ULBS, free surface viscous flows around the ship with and without a stern tunnel are computed. Total resistance coefficients are compared with each other and with experimental data. Grid convergence study is performed with respect to resistance for the verification of the results.The three dimensional vortical structures in the stern of the two hulls are analyzed and compared with each other. Large scale flow separations behind the stern due to the bluntness of a hull and effects of a stern tunnel to flow fields are discussed.