In this paper we will look at the effectiveness of a non-invasive means of measuring key dynamic characteristics of a tug and tow system for complete voyages. Thereafter, we will use this information to drive a numerical simulation of the towline. A prototype, compact, and rugged test sensor suite was installed on both a tug and barge for an inshore waters tow on the West Coast UK. This data was post-processed and fed into a lumped mass numerical model of the system. Initially only GPS position data is used and the effects and importance of processing higher resolution surge, heave, and sway data will be checked. Conclusions are drawn which will be used to guide further research in this area.
The use of tugs drawn from the spot market for coastal tows is a well established practice. However the criteria governing the suitability of tug selection vary between approving authorities with disagreements evident on the effectiveness of smaller tugs below a bollard pull range of 50 Te. A technical review of these differing assessments is problematic due to a lack of comprehensive field data for such tows. Extensive research has been carried out on various aspects of towline dynamics during such operations some of which is validated by full scale sea trials. However, a common feature of these full scales trials is the lack of a full dataset for the complete tug and tow system covering all 6 degrees of freedom (DOF) principally due to technology available at the time. It is proposed that a system that can be quickly and easily set up on tug and tow at short notice, commensurate with the window of opportunity typically presented for such marine operations would allow more extensive field data to be gathered.