Abstract
The propeller jet from a ship has a significant component directed upwards towards the free surface of the water, which can be used for ice management. This paper describes a comprehensive laboratory experiment where the operational factors affecting a propeller wake velocity field were investigated. The experiment was conducted using a steady wake field to investigate the characteristics of the axial velocity of the fluid in the wake and the corresponding variability downstream of the propeller. The axial velocities and the variability recorded were time-averaged. Propeller rotational speed was found to be the most significant factor, followed by propeller inclination. The experimental results also provide some idea about the change of the patterns of the mean axial velocity distribution against the factors considered for the test throughout the effective wake field, as well as the relationships to predict the axial velocity for known factors.
Highlights
Propeller wake wash can be used as a means of clearing pack ice and small ice masses from the vicinity of offshore installations and shipping channels
A total of 18 propeller conditions comprising different combinations of the three factors were used to create an experimental plan with the Design Expert 10.0 software for a Center Composite Design (CCD) of the Response Surface Methodology
A decision was made to assume longitudinal symmetry about the mid plane and only to survey half the width of wake field based on empirical analyses performed by earlier researchers [8,9,11,14,16,17,18,19,20], who reported the axisymmetric nature of the wake velocity distribution for the far zone downstream of propeller wake
Summary
Propeller wake wash can be used as a means of clearing pack ice and small ice masses from the vicinity of offshore installations and shipping channels. In a full-scale study of various pack ice management techniques performed offshore Newfoundland, propeller wake wash was found to have an appreciable degree of success [1]. In more recent studies of ice management techniques, the wake of an azimuth thruster was shown to be useful for ice breaking [2,3], in addition to clearing ice from designated areas. The application of propeller wake wash as an ice management tool has been investigated at a model tank scale by Ferrieri [4], where change in ice concentration was investigated as a function of the factors affecting propeller wake wash. Bastin [5] developed a simple mathematical model of propeller wake wash based on Ferrieri’s experimental results
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