Numerical study of the propeller-induced exciting force under the open freedom condition

Abstract

A ship is certain to generate heave and trim in an actual navigation process. To investigate the difference between the hydrodynamic performance after a change in hull gesture and the value calculated based on the constrained model using the method of RANS, a 6-degrees of freedom (DOF) movement model and a superposed rotation model were adopted for a numerical self-propelled experiment under the state of fixation and the state of open DOF. KCS ship and KP505 propeller were used as the research objects. The transfer of numerical values for unsteady flow fields was implemented via overset grid technology. Comparative analysis of the streaming field around a hull and the propeller-induced exciting force was conducted. Compared with the fixation state, the buried bow of the ship is trimmed under open DOF, which leads to differences in wake flow field and bow wave. Compared with the state of open DOF, excessive prediction of the stern fluctuating pressure is observed when a numerical self-propelled experiment is conducted on the basis of a fixed model.