Abstract

In this study the effect of energy saving devices (ESDs) on the forces, motions and flow field around the stern of KRISO Very Large Crude-oil Carrier2 (KVLCC2) was investigated by using Experimental Fluid Dynamics (EFD) method in regular head waves of λ/L=0.6, 0.85, 1.1, 1.35 and 1.6 for an amplitude of 3cm. Various energy-saving rudders were installed downstream of the propeller and their performance in waves investigated. The flow field was measured by Stereo-Particle Image Velocimetry (SPIV) system on two transverse planes (upstream and downstream of propeller and rudders) to understand the effect of rudders on the flow field.

INTRODUCTION

In order to combat the production of greenhouse gas (GHG) emissions from the shipping industry, the International Maritime Organization (IMO) introduced the Energy Efficiency Design Index (EEDI) for all new ships. In order to meet this requirement, one of the measures has been to explore the use of ESDs. The ESDs are categorized into three major classes; those installed upstream of the propeller, those installed at the propeller station and those installed downstream of the propeller (Carlton, 2012). The ultimate goal is to improve the inflow into the propeller and trying to recover the lost energy in the ship hull wake field and propeller slipstream.

The topic of ESDs has been studied by many researchers in order to improve the propulsive efficiency of the ships at sea. However, most of the studies have been conducted in calm water but have rarely been done in waves. Celik (2007), numerically studied the effect of a wake equalizing duct (WED) on the propulsion performance of a chemical tanker using Reynolds Averaged Navier-Stokes (RANS) method and reported a maximum gain of about 10% propulsive efficiency as well as an additional positive thrust by using an appropriate WED design. IHI Marine United Inc. (IHIMU) employed a Semicircular Duct in full scale ships and verified its energy-saving principles using both Computational Fluid Dynamics (CFD) and Particle Imaging Velocimetry (PIV) methods (Inukai et al., 2017). The hydrodynamic design of a pre-swirl stator (PSS) with radially variable pitch which is paired with a conventional propeller is described by Saettone et al., (2016). They investigated the designs and configurations for the propeller and stator in different operating conditions using vortex-lattice method and CFD-based approach to explain the influence of the stator on the propeller. Karim and Naz (2017) studied the flow field around a ship hull including selfpropulsion characteristics at varying rudder positions. They concluded that the effect of the rudder decreases with increase in the rudder's longitudinal distance from the propeller.

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