RIASSUNTO
ABSTRACT
Icing affects the stability of the ship and increases the ice resistance, and poses a major threat to the ship navigation. The existing studies on ship icing focus more on the freezing of supercooled water droplets but ignore the microscopic growth process of ice. This paper realized the simulation and visualization of the sea ice crystal growth using Python programming tool, based on Wheeler’s phase field model. The coupled equations were solved by the finite difference method. The simulation results were compared with the microscopic observation results and the real snow crystals in nature, and the reliability of the numerical method was verified. This paper also described the icing principle and explained the changing process of the crystal growth. The effects of various parameters on the growth and final morphology of ice crystals were analyzed by analyzing the sensitivity of the important model parameters. The accurate simulation of ice crystal growth can provide the understanding of the recalescence stage of the freezing water droplets and present a theoretical basis for polar ship’s anti icing / deicing design and safety.
INTRODUCTION
In an arctic environment, wave impact and splash can significantly affect ice accretion on a marine structure. The vessels and offshore structures will face the problem of icing and ice accumulation in cold seas and ocean regions. According to a report by Dehghanisanij(2017), the phenomenon of icing has led many fishing vessels of small and medium sizes to be lost at sea and has adversely affected the stability and movement of small cargo ships. Therefore, it is significant to develop a good understanding of the icing mechanisms. Most of the existing research on ship icing focuses on the prediction of icing amount and the freezing of supercooled water droplets. Ryerson (2011) provided a framework for assessing the relative threat of ice accumulation types, such as superstructure ice, glaze, rime, frost, and snow, to the safety of platform functions. Kulyakhtin et.al (2014) simulated droplet impingement on a cylinder and investigated the ability of different turbulence models to predict the collision efficiency and the droplet distribution in the wake. Yao et.al (2018) studied the impact and freezing process of a water droplet on a cold surface experimentally and numerically, the dendrite growth stage of water droplet freezing was neglected.