基于IDDES方法的模型尺度和实尺度VLCC阻力预报与流场分析

随着CFD技术的发展和计算机运算能力的提高,CFD在船舶设计中发挥着越来越重要的作用。目前CFD对于船舶阻力的计算基本集中在模型尺度,一方面因为实尺度缺乏相关的实验数据,导致缺乏对实尺度高雷诺数下近壁面湍流模型和壁面函数的探索;另一方面也是因为在实尺度计算中,非定常特征更加明显,数值计算的复杂性会大大增加,传统的RANS方法处理起来较为困难。该文应用基于OpenFOAM开发的船舶与海洋工程水动力求解器naoe-FOAMSJTU,应用改进的DES模型—IDDES,采用CFD方法同时对模型尺度和实尺度的32万吨VLCC进行阻力预报,并分别与RANS的计算结果、实验结果/三因次换算结果进行比较分析。在实尺度计算中考虑到表面粗糙度的影响,采用带粗糙度补贴的壁面函数进行近壁面处理。该文探讨了采用IDDES方法在船模和实船阻力预报中的可行性,同时也对实尺度和模型尺度下的流场进行了讨论与对比分析。

Model-and Full-scale VLCC resistance prediction and flow field analysis based on IDDES method

With the development of CFD technology and the improvement of computing capacity,CFD is playing an increasingly important role in ship design.However,at present CFD computations of ships are typically performed in model scale due to the lack of experimental results in full-scale,and the increasingly complexity of numerical simulation at very high Reynolds numbers that RANS is hard to solve.In this paper,a RANS/DES solver for naval architecture and ocean engineering named naoe-FOAM-SJTU,which is developed from OpenFOAM,is applied to carry out the numerically simulation of modeland full-scale VLCC.For model scale computation results,we adopt the three-dimensional extrapolation method to get full-scale resistance,and also full-scale calculation is carried out by CFD method at the cruise speed directly.Results are compared with the experimental results/three-dimensional extrapolation results.The effect of surface roughness is considered in full-scale computations.Analysis results show reliability and validity of our IDDES method in ship resistance prediction.This paper also made a discussion on comparison of flow fields of model-and full-scale VLCC.