ABSTRACT

In ice milling condition, the ice-class propeller will suffer extreme ice loads, which pose a threat to the safe operation of propeller. By using ANSYS/LS-DYNA, this paper introduces a numerical method to predict ice contact dynamic loads and propeller strength. In the simulation of a certain operational condition, the characteristics of ice failure processes, dynamic loads, blade stress, and the deformation of the propeller are analyzed. The effects of depth of cut on the numerical results are studied. The results show that the stress of the propeller is great in ice milling condition and mainly concentrates in the leading edges of propeller tip.

INTRODUCTION

With the development of Arctic sea Route and exploitation of polar resource, the number of ice-going ship continues to increase. The propeller, as vital components for ice-going ship, has a significant effect on the vessel's safety navigation. When ice-going ships navigate in ice covered waters, the submerged piece or pieces of ice may approach and contact the propeller. In this process, the propeller blades will suffer extreme loads. Ice load and hydrodynamic load are two main loads to the propeller during the interaction among ice, propeller and water, which will cause the deformation and damage of propeller blades. Evaluation of propeller strength plays a crucial role to the design and safe operation of ice-class propellers.

The study of propeller strength in this condition shows its importance to the design of ice class propeller. The characteristics of propeller dynamic forces have been reported. However, certain mechanisms are not fully understood and are still under discussion. In most cases, the researches (i.e. Searle et al., 1999; Moores, 2002; Wang et al., 2005) of propeller-ice contact problem are based on experimental measurements. Due to the technical difficulties, experimental measurements can only be done in certain condition, and detailed description of the load distribution is not available. For the complexity of propeller-ice interaction, numerical simulations have historically been based on some empirical interaction models(i.e. Kotras et al.,1985; Veitch, 1995; Jones et al., 1997; Soininen, 1998) without much consideration of detailed ice mechanics, so their applications are limited to specific conditions. Numerical simulation is nonetheless an effective method. With the development of computer technology and numerical techniques, Finite Element Method (FEM) has been used to model the propeller-ice interaction by scholars. Lee (2007) discussed some concerns on general practice on ice propeller strength assessment according to IACS URI3 Rule by using FEM. Based on FEM, Vroegrijk et al. (2014) proposed a new material model to describing the orthotropic rate-dependent properties of sea ice, focusing on propeller-ice interaction.

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