基于高斯近似和NSGA-Ⅱ的伴流螺旋桨优化

Optimization of wake propeller based on Gaussian approximation and NSGA-II

  • 摘要:
      目的  为改进船舶推进性能,提高船舶效能,克服螺旋桨参数众多、建模繁琐、水动力数值计算收敛速度慢、伴流场的湍流效应等问题,提出一套螺旋桨高效优化方法。
      方法  首先,将基于非均匀有理B样条的自由曲面变形(NFFD)技术构建的参数化螺旋桨作为输出,利用CFD数值仿真对螺旋桨性能特征进行预报。然后,基于仿真数据建立螺旋桨性能高斯近似预测模型,建立以提高效率、降低扭矩系数为目标的优化模型,利用二代非支配排序遗传算法(NSGA-Ⅱ)得到最优解。
      结果  结果显示,在均匀流场和船后伴流场下,螺旋桨的优化结果有着相似规律,即桨叶宽度和厚度均呈减小的趋势,倾斜角呈增大趋势,但由于在船后伴流场下流速会降低,因而桨叶宽度和厚度的减小以及倾斜角的增加幅度相对于均匀流场下的小。
      结论  采用所构建的方法可以实现均匀流场和船后伴流场下螺旋桨的高效优化设计。

     

    Abstract:
      Objectives  In order to improve ship propulsion performance and efficiency, and overcome such obstacles as numerous propeller parameters, complicated modeling, slow convergence of hydrodynamic numerical calculations and turbulent wake field effects, this paper proposes an efficient propeller optimization method.
      Methods  A parameterized propeller constructed with non-uniform rational B-spline based free form deformation (NFFD) technology is used as the output. The CFD numerical simulation is applied to predict its performance characteristics and the Gaussian approximate prediction model of the propeller performance is established based on the simulation data. The optimization model aims to improve efficiency and reduce the torque coefficient by using the second-generation non-dominated sorting genetic algorithm (NSGA-II) method to obtain the optimal solution.
      Results  The results show that under the uniform flow field and wake field behind the ship, the optimization results of the propeller have similar laws; that is, the blade width and thickness of the propeller show a decreasing trend, while the inclination angle shows an increasing trend. The flow velocity decreases in the wake field behind the ship, so the reduction in width and thickness and increase in inclination angle of the propeller blade are smaller than those in the uniform flow field.
      Conclusion  The method proposed in this paper can be used to achieve the more efficient optimization design of propellers under uniform flow fields and wake fields behind ships.

     

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