Development of Computational Method for Calculating Ship Viscous Flow at Full-Scale Reynolds Number

下一代舰船的设计将与目前使用的舰船大不相同。因此，更多创新的设计理念将应用于设计更高性能和整体运营效益的船舶。在这类船型的设计中，过去50年来发展起来的现有设计数据库中的大部分并不直接适用。由于通过模型研究快速扩展设计数据库的成本过高，因此开发基于仿真的设计工具的动机非常强烈，这些工具能够减少或消除对模型规模测试和将结果外推到全尺寸的需求。这是计算流体动力学（CFD）进一步发展的重要背景；然而，许多CFD方法，特别是基于reynolds -average Navier-Stokes （RaNS）方程方法的CFD方法，在全尺寸船舶流模拟中仍然存在困难。本文研究了在考虑考虑表面粗糙度效应的近壁流动建模的基础上，发展全尺寸湍流条件下船舶粘性流动模拟的计算方法。主要目标有两个方面：(1)发展适用于全尺寸流动模拟的RaNS方程方法；(2)研究合适的全尺寸Rn物理模型。特别地，两点壁面函数方法的有效性和优势已经被研究和扩展，包括表面粗糙度对流动和阻力的影响。本文提出的中尺度船舶流动数值模拟方法是在前人研究方法的基础上进行扩展的，结合标准的κ-ε模型，可以采用两种近壁模型，即双层法和两点壁面函数法，其中两点壁面函数法在实际设计中更为适用。

Ship designs in next generation will be dramatically different from those currently in use. As such, more innovative design concepts will be applied for design of ships with higher performance and overall operation benefit. In the design of such hull forms, much of the current design database, which has been developed over the past 50 years is not directly applicable. Since it will be prohibitively expensive to quickly expand the design database through model studies, there is strong motivation to develop simulation-based design tools, which are able to diminish or eliminate need for model-scale tests and extrapolation of the results to full scale. This is an important background of further development of Computational Fluid Dynamics (CFD) ; however many CFD methods especially for those based on Reynolds-averaged Navier-Stokes (RaNS) equation method, still suffer difficulties in full-scale ship-flow simulation.The present study concerns development of computational method for simulation of ship viscous flow at full-scale Rn in conjunction with consideration of near-wall flow modeling including surface roughness effects. The main objectives are two folds : (1) development of RaNS equation method applicable to full-scale flow simulation; and (2) investigation on appropriate physical model for full-scale Rn. In particular, the validity and advantage of two-point wall-function approach^<3)> has been investigated and extended for inclusion of surface roughness effects on flow and resistance. The present numerical method for Mi-scale ship-flow simulation is based on extension of method developed by the present investigators, such that, in association with standard κ-ε model, two near-wall models can be employed, i. e., two-layer method and two-point wall-function method with capability to include surface roughness effects, where the latter has been shown more suitable in practical design use.