Experimental Analysis of the Near Wake from a Ducted Thruster at True and Near Bollard Pull Conditions Using Stereo Particle Image Velocimetry (SPIV)

Abstract

Thrusters working at low advance coefficients are employed in a wide range of offshore and marine applications on Floating, Production, Storage, and Offloading (FPSO) systems; shuttle tankers; tug boats; and mobile offshore units. Therefore, an understanding of the flow around the thrusters is of great practical interest. Despite this interest, there is lack of knowledge in the description of the hydrodynamic characteristics of a ducted thruster’s wake at bollard pull and low advance coefficient values. This work was aimed at providing detailed data about the hydrodynamic characteristics of a Dynamic Positioning (DP) thruster near wake flow at different low advance coefficient values. Wake measurements were made during cavitation tunnel tests carried out on a ducted propeller model at the Italian Ship Model Basin (INSEAN), Rome, Italy. Through these experiments, the DP thruster near wake velocity components at different downstream axial planes, up to 1.5 diameters downstream, were obtained using a Stereoscopic Particle Image Velocimetry (SPIV) system. These experiments were carried out at different advance coefficient (J) values [bollard pull (J=0), J=0.4 and J=0.45].