Marine propeller-ice interaction simulation and blade flexibility effect on contact load

Operating ships in ice covered seas will definitely cause propeller and ice come to interact. The propeller-ice contact problem was widely studied in 1990's. The research resulted to simulation models for the contact process and contact load calculation. These models were developed on assumption of rigid propeller blade. Ice was modelled as mass object with inertia and certain shape, where the propeller blade contacted, causing contact pressure and forces acting on the blade and ice. Significant outcome from these models was that propeller rotational speed, propeller pitch and advance speed in relation to the ice block were dominating factors contributing to the contact load magnitude, direction and duration. The contact loads are significant so propeller blade is expected to deform under such loading. The effect of the blade flexibility on the contact load behaviour can be studied with combining the contact load model and finite element method model of the propeller blade. A state of the art approach is taken as follows: a) simulate propeller-ice contact with rigid, undeformed blade b) calculate blade ice load by ice class rule formula or from contact load model c) use this loading with FEM as static load to determine the propeller blade deformation d) use the resulting deformed blade geometry for propeller-ice contact model. The magnitude of the effect of blade flexibility to ice contact load can be determined this way. If need arises, more advanced methods can be applied to the problem.