无结构网格二维海洋模式的正压梯度力算法改进

Algorithm Improvement of Barotropic Force in an Unstructured Grid Two-dimensional Ocean Model

基于一套自主研制的无结构网格二维河口海洋数值模式A2D,在大圆湖理想模型下,通过与解析解进行比较分析,采用不同架构配置,改进设计正压梯度力计算方法。改进后的算法中引入了从算架构的配置,以配合主算架构,得到更佳的稳定性。通过水位场平面分布与单点过程线可以发现,三组试验的算法均获得了较好的精度和比原算法更好的稳定性,其中TSNS配置算法(中心点计算水位、边中点计算流速的主算架构,配合节点计算水位、边中点计算流速的从算架构)由于其主算架构更接近结构网格下的C网格,在守恒性、移动潮滩边界处理等方面具有一定优势和便利性,有利于在实际海洋中的计算。将TSNS配置算法在江浙沿海进行试算,水位验证结果与实测基本符合,与原A2D模式计算水位之间无显著差异。TSNS算法在稳定性方面的改进,有助于提升模式升级为三维后的稳定性,为今后模式成功升级为三维打下基础。

Based on A2D, an independently developed unstructured grid two-dimensional ocean model, and by comparison with analytical solution under an ideal Model Great Lake, the algorithm of barotropic force was improved via employing different computational designs. In the improved algorithm, an assistant design was introduced to cooperate with the major design in order to acquire better stability. Results of elevation field and site time series showed that algorithms of three experiments got satisfactory accuracy and better stability. The TSNS algorithm was among the three, in which the major design solves elevation at centroid and velocity at mid-point of side, and the assistant design solves elevation at node and velocity at mid-point of side. Due to the similarity of its major design to C-grid design in a structured grid, the TSNS algorithm had advantages in conservation and movable tide-flat boundary treatments, which made the algorithm easier to apply for real ocean simulations. The TSNS algorithm was applied to the simulation in real sea near Jiangsu and Zhejiang. The simulated elevation had a good agreement with observed data, and was similar with results from the original A2D model. The improvement in stability will help TSNS algorithm get better stability in three-dimensional upgraded version, and will be the foundation of a successful three-dimensional version in future.