Author(s): Robert Ettema; Hung-Pin Huang
Keywords: No Keywords
Abstract: The effects of vessel transit on ice-cover formation pose important concerns for winter use of heavily trafficked navigation channels. Of prime concern is the likelihood that such channels to become clogged with broken ice. Results are reported of a laboratory study aimed at determining the effects of frequent vessel transit on ice-cover formation over navigation channels. The study entailed extensive experimentation carried out with an ice tank and two hulls of very different shapes. One hull, herein called the wedge hull, was used to simulate the hull shape of a typical ship. The second hull, herein called the tow hull, was used to simulate the flat-bottomed, shallow-draft hull of a typical river tow-barge. It was found that the two di fferent hull shapes 1ed to di fferent patterns of ice formation. Transits by the wedge hull resulted in a more-or-less uniform accumulation of brash ice along tracks opened through ice covers grown over the ice tank. The volume of ice produced by transiting increased almost log-linearly with increasing transit frequency. At most, transiting led to a doubling in the volume of ice grown along the area of the channel opened by transiting. Also, it was found that the median size of brash-ice fragments formed in the track decreased log-linearly with increasing transit frequency. Transits by the tow hull were dominated by that hull's propensity to entrap ice under-hull and transport it along tracks opened through the ice tank. As a result, tow transiting led to the formation of thick localized accumulations of brash ice that are herein termed plugs as they potentially may impede further transiting.