船体在海水中流动加速腐蚀数值分析

Numerical analysis of flow-accelerated corrosion of a hull in the marine environment

为了预测动态海洋环境下船体表面的腐蚀速度,同时为防腐设计提供可靠的参考,本文采用数值模拟的方法建立了流动加速腐蚀计算模型。首先对船体周围的海水流场建立了CFD模型,并进行了计算,得到了速度、压力、氧浓度分布等流场信息;然后根据这些信息建立了船体在流动海水中的FAC模型,并进行求解,得到了船体表面各点的传质系数和腐蚀速度分布。结果表明:船体后部和侧后部因为氧的浓度较大,其腐蚀速度明显比其部位大,而且随着流速的增大,腐蚀速度也变大,在没有保护涂层的情况下,最大腐蚀速度可达22 mm/a,比静态条件下大得多,因此当采用阴极保护时,应充分考虑这些部位,以便合理地布置阳极位置。

To predict the corrosion rate of a hull surface in the dynamic marine environment and provide a reliable reference for anticorrosion design,a calculation model of flow-accelerated corrosion is established in this paper using numerical simulation.First,a computational fluid dynamics model is established for the seawater flow field around the hull;flow field information including velocity,pressure,and oxygen concentration distribution are obtained by calculation.Then,a flow-accelerated corrosion model of the hull in seawater is established based on these parameters.Finally,the model is solved,and the mass transfer coefficient and corrosion rate distribution of all points on the hull surface are obtained.Results show that the corrosion rates at the rear and lateral rear parts of the hull are significantly higher than those at the other parts owing to a higher concentration of oxygen at these parts.The corrosion rate increases with the increase of flow velocity.The maximum corrosion rate can be up to 22 mm/a under a no protective coating condition,and is much higher than that under the static state condition.Therefore,these two parts should be taken into full consideration so as to arrange the anode position rationally when cathodic protection is adopted.