Numerical Computation is a crucial tool to design ship performance including energy saving devices (ESDs). A procedure to design ESDs through the computational methods is proposed in this paper. The procedure consists of two steps. In the first step, the simple computational method based on inviscid panel method including the shed vortex sheet to estimate the axial force acting on rudder and ESDs. The computational time and input procedures for prediction of the better ESDs for propulsive performance from the many geometries are very small. After the first step, the performance of chosen ESDs attached on the ship model are tested by RANS solver based procedure. In the second step, the commercial software FINEMarine ver 5.2 is used to solve the flow around hull, propeller, rudder and ESDs. The rotating propeller is modeled by the body force distribution using total velocity in computation. The procedure is validated through the towing tank experiment. In the experiment, Japan Bulk Carrier model is used as an example hull geometry. The resistance test, self-propulsion test and SPIV measurement around propeller and ESDs are carried out in the experiment.
In order to improve the ship propulsive performance, researches are accelerated in not only the hull form optimization to get the high performance ship, but also the development of various energy saving devices (ESD) due to EEDI regulation to Carbon Dioxide emission.
At the final design stage of hull form and ESD, the model tests in towing tank are required to confirm the expected improvement of propulsive efficiency. But in the early and middle stage, it is difficult to conduct the tests using large model and various ESDs to verify and compare the efficiency due to the high cost and required time.
On the other hand, due to the recent development of computational resources and computational fluid dynamics (CFD), the computation of flow around fully appended ship hull and ESD with complicated geometry can be conducted using in-house codes, open source codes or commercial codes. Then, the procedure by utilizing them might be promising for quick response design to screen many candidates of ESDs. There are many method using numerical computation to solve the flow field and hydrodynamic forces acting on the hull, propeller, rudder and ESDs to consider the interaction. In this paper, two-step procedure is introduced. First, the potential based panel method is used to design ESD geometries in order to save computational time. Next in the middle stage, Navier-Stokes based CFD is used to evaluate the precise flow field to treat the interaction among hull, propeller, rudder and ESDs, and to modify the ESD geometries.