AN INVESTIGATION ON ITTC 78 SCALING METHOD FOR UNCONVENTIONAL PROPELLERS

Paper i proceeding, 2016

The effort to find solutions to the environmental and energy saving problems regarding the operation of ships is always a matter of concern. Several new unconventional propeller designs have been introduced in recent years. These unconventional propellers are de- signed with non-planar lifting surfaces and a design approach to improve the energy efficiency by reducing the tip vortex loss and having a better lift/drag ratio. Suspicions have been raised that the standard methods for evaluation of model tests such as the ITTC 78 method does not take the full effect of unconventional propellers in to account [1]. In the present investigation, the performance of two propellers (one conventional and one unconventional) are analyzed us- ing CFD (RANS) in model and full scale in different operating conditions (open-water and behind a hull). The validation studies are performed in model scale and compared with the ex- perimental data. Further the computations are extended to full scale to study the scaling effects on the propulsive efficiency and different propulsive coefficients. The outcome is compared with the predictions from ITTC 78 method applied on different geometries and conditions.