Warm Model Ice and Propeller Interaction, Capturing the Driving Mechanics?

In the drive to design robust and more efficient propellers, the need to understand propeller-ice interaction is increasing. Traditionally MARIN has built up this kind of propeller design knowledge by developing and testing large systematic propeller series, such as the classic Wageningen B-series and the recent C- and D-series. With systematic variations of blade number, area, pitch and profiles it can be investigated how these parameters influence the design and how the most efficient designs for operation in open water and in ice can be reached. This is becoming especially important for the lower ice class propellers, which are rarely sailing in ice covered areas. Apart from this, these designs should be optimized for low noise emission as well, to ensure application in the sensitive Arctic environment. When both milling and crushing loads can be captured using a warm model ice, the testing of such a large systematic propeller series becomes possible without the use of an ice basin.
In the present paper an evaluation is presented, showing the results of a first series of testing that was carried out with a warm model ice. The test set-up used is one that has also been used for the same kind of tests in a real ice basin. The warm model ice was designed to resemble the correct crushing strength at model scale. The warm ice samples are fed into the propeller, while at the same time the load on one of the propeller blades is recorded with a 6C-load transducer. At the same time the impact is recorded with a high speed video camera. To enable a detailed analysis, the force vector is plotted on the high speed recording. The force vector can be derived using a centre of pressure method. In this way an evaluation can be made if the captured phenomena are indeed similar to those that can be expected from real (model-)ice.