The safe navigation of the Icebreaking Emergency & Evacuation Vessel on the sea basin around the Kashagan field in the Northern Caspian Sea was central to the cooperative research project between AGIP KCO, Navalprogetti and University of Trieste. Although the project focused on the ice-going capability, it also provided an opportunity to investigate the hydrodynamics of the vessel moving in very shallow water.

This paper highlights main aspects of the shallow and ultra-shallow water effects on characteristics of resistance, hull-propeller interaction and propulsive qualities of an icebreaking vessel at subcritical speeds through a huge experimental campaign carried out at both model- and full-scale carried at and with support of the KSRC.

Because of thrust deduction increase and wake fraction oscillation even at subcritical speeds, a substantial decrease of propulsive efficiency was ascertained, particularly in ultra-shallow water. Accurate self-propulsion tests carried out following the ‘hybrid method’ of KSRC allowed assessment of the net thrust and rope pull capability with accuracy required to operate safely in the harsh environment of the Northern Caspian Sea. Discrepancies in wake fraction between starboard and port propeller were dramatic, mainly due to flow-back effects. Dependencies of wake fraction and thrust deduction factor in deep and shallow waters are discussed too as well as the scale effect on the wake.

Finally, the icebreaking capability of the IBEEV was determined after identification of the experimental lines for total resistance in level ice in both deep and shallow water. To this end, the bollard pull was converted into net thrust by introducing the thrust deduction factor in the speed range of interest.