Cutting ice with "high" pressure water jets

The potential of "high" pressure water jets to cut slots in an ice sheet, primarily for possible use as an assist to ice breaking, has been under investigation by the Division of Mechanical Engineering of the National Research Council of Canada. In the field, slots have been cut into and through fresh water ice, about 0.7 m thick with water jets applying up to about 260 kW of power to the ice. Each ice sheet consisted of a clear bottom layer and multiple upper layers of opaque white ice. The ice temperature just below the top surface ranged from - 210 C to 00 C. In the laboratory, cuts to more than 17 cm were made in artificially grown, essentially clear, fresh water ice, and cuts to almost 25 cm were made in a simulated sea ice. Up to 50 kW was applied to the fresh water ice and up to 31 kW was applied to the simulated sea ice. This report describes the ice cutting performance of small to moderate scale water jets. The majority of cuts produced a narrow, clean kerf, indicative of erosion in a ductile material, while other cuts produced a wide spalled trench, indicative of spalling in a brittle material. Still others produced a combination of the two modes of cutting, with a wide, shallow trench and a narrow, deep kerf below the trench. In many cases the ice was also crazed extensively by the water jet. The causes and the effects of these characteristics on ice cutting performance are discussed, along with the effects of jet traverse speed, nozzle diameter, nozzle pressure, nozzle standoff, ice characteristics and the overall scale of the system. An empirical relationship, derived by regression analysis, is presented correlating the jet penetration to the power in the jet, the jet traverse speed, the nozzle standoff and the estimated ice temperature.