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ABSTRACT
To get a more uniform wake, placing several flow control devices in front of the propeller location may be a good choice. Most of these devices are used to improve propulsive efficiency, but some of them aim at improving other hydrodynamic characteristics, such as the cavitation behavior, vibration level, maneuverability, and so on. The most commonly used control devices are the wake equalizing ducts (WED hereafter), Grothues spoilers, stator fins, or different combinations of them. The goal of this paper is to calculate via software Ansys 13(TM) the influence of placement of a WED to an existing ship over the propeller efficiency in terms of propulsion. The wake equalizing duct (WED) is one of the most commonly used energy saving devices for improving the propulsion performance of a ship; and reducing the propeller-excited vibrations and viscous resistance forces. In this paperwork two versions of an existing ship in normal version and retrofitted with WED device were analyzed in order to demonstrate the influence on the WED device on the propeller efficiency. It was demonstrated that the propulsion is increased with 4.64% which is very well in line with the results of other researchers which are crediting the WED influence somewhere in between 5 to 10%. Moreover it became obvious that the WED device is transferring some of the streamlines which in the WED free after body would simply pass beside the propeller, to the propeller fluid domain improving by this the overall efficiency of the propeller. This is demonstrating beyond any reasonable doubt that WED device is improving the performance of the propeller and the choice of retrofitting a ship with such a device may trigger fuel savings along with a less environment impact.
Keywords: Wake Equalizing Duct; Propeller Efficiency; Maritime Ships; Finite Volume Analysis.
1. INTRODUCTION
Extensive studies proved that the propeller represents the main source of vibration and noise aboard ships.
Lowering the vibration level can be done in two ways: either by improving the propeller design or by optimizing the wake field behind the ship hull. Because the first method requires validation in the cavitation tunnel which is rather expensive and time consuming, the attention focused towards improving the ship wake. A more uniform wake can be regarded as a...