| The energy saving of ships has become an important task in shipbuilding and shipping field of the world. It relates to the fuel saving, the cost reduction of transportation, environment protection and profit increase of the enterprise. Installing the energy saving appendages in ships is an effective method for the energy saving, which have characteristics of significant energy saving effect, simple structure and low cost. The energy saving device was studied by a numerical method and the influence of the energy saving device on ship wake was analyzed from the point of flow field details, which had an important theory meaning and engineering value. Based on surface panel method and CFD technique, the unsteady interaction between hull, energy saving appendages and propeller was studied in the paper. The purpose of the paper was to obtain a numerical analyzing method of hydrodynamic performances of energy saving devices.Firstly, this paper studied the prediction method of the propeller performance in viscous flow field, which was based on sliding mesh technique. And the paper used the CFD pre-processor to partition the flow filed mesh and generate multi-block hybrid mesh. Key factors that influenced the precision of calculation were analyzed which included the disposal method of flow field mesh based on the sliding mesh technique, the modeling method of three dimensional propeller geometry model, the wall Y+ value and the judgmental method of calculation stability. The influences of different turbulence models on prediction results were analyzed. The unsteady hydrodynamic performance of DTRC4842 and PHS propeller in uniform wake was predicted. And the unsteady hydrodynamic performance of Seiun-Maru HSP propeller in non-uniform wake was also predicted. Secondly, in order to get the suitable numerical prediction method of flow field of the full form ship, the modeling method of ship geometry model was discussed in the paper. And the influences of mesh partition methods on calculation results were compared and analyzed in details. The applicability of different turbulence models which were used to predict the viscous flow field of full form ship was studied. The mesh partition methods and turbulence models were obtained by comparing the numerical results and experimental results. The wake fractions on the propeller disc of a certain chemical tanker and a container vessel were simulated to validate the applicability of the mesh partition methods and turbulence models.Thirdly, the paper studied the hydrodynamic performance of three cases, which included ship without propeller, propeller without ship and ship with propeller. The paper analyzed the influence on the ship hull and propeller caused by the unsteady interaction between ship and propeller. The flow field disposal methods and mesh partition methods were the same as methods of predicting the propeller performance and the flow field of full form ship. This paper used GAMBIT, Tgrid and ICEM CFD to partition the flow filed mesh. The Detached Eddy Simulation turbulence model was chosen in the study.Finally, based on the prediction of the wake of one full form ship, the pre-position duct of propeller, compensating duct and diversion fin were designed which based on the water tracks distribution characteristic through ship hull. And the influences of the appendages on the wake were predicted and analyzed. The characteristics of flow field were found which decided the energy saving effect. The working mechanism of energy saving appendages was analyzed from the flow field details. Combined with the experimental wake of the naked hull and calculation wake of hulls with three type energy saving devices, the energy saving effect of the three types energy saving devices was predicted using surface panel method theory and CFD technique. A numerical study method of pre-propeller energy saving devices was obtained which could be used to design energy saving devices and predict the energy saving effect based on surface panel method theory and CFD technique.
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