The 12th International Conference on Hydrodynamics
18 – 23 september 2016, Egmond aan Zee, The Netherlands
Home Program Author Index Search

AN INVESTIGATION ON ITTC 78 SCALING METHOD FOR UNCONVENTIONAL PROPELLERS


Go-down ichd2016 Tracking Number 142

Presentation:
Session: Ship hydromechanics resistance II
Room: Room 1
Session start: 14:00 Mon 19 Sep 2016

Surya Kiran Peravali   peravali.suryakiran@gmail.com
Affifliation:

Rickard Bensow   rickard.bensow@chalmers.se
Affifliation:

Walter Gyllenram   walter.gyllenram@smhi.se
Affifliation:

Abolfazl Shiri   abolfazl.shiri@sspa.se
Affifliation:


Topics: - Ship hydrodynamics resistance, propulsion, powering, seakeeping, manoeuvrability, slamming, sloshing, impact, green water

Abstract:

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 the recent years. These unconventional propellers are designed 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 using 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 experimental 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. The RANS assessment showed additional scaling effect for the present unconventional propeller compared to the conventional propeller. At the design condition the RANS study estimates the unconventional propeller has lower effective wake and hull efficiency compared with the conventional propeller. However, the propeller efficiency and total efficiency is higher for the unconventional propeller. The CFD estimations in full scale contradict the estimations from the ITTC 78 method. In this paper, the differences between the CFD and ITTC 78 method are presented and the areas of further research are identified.