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

下一代的船舶设计将与目前使用的截然不同。因此，更多的创新设计理念将被应用于具有更高性能和整体运营效益的船舶设计。在这种船型的设计中，许多现有的设计数据库并不直接适用，这些数据库是在过去50年中发展起来的。由于通过模型研究快速扩展设计数据库的费用将高得令人望而却步，因此有强烈的动机开发基于模拟的设计工具，这些工具能够减少或消除对模型规模试验和结果全面外推的需要。这是计算流体力学(CFD)进一步发展的重要背景，然而，许多CFD方法，特别是基于雷诺平均N-S方程(RANS)方法的CFD方法，在全尺度船舶流动模拟中仍然存在困难。本研究旨在结合考虑表面粗糙度影响的近壁流动模拟，发展全尺度船舶粘性流动模拟的计算方法。主要目标有两个方面：(1)发展适用于全尺度流动模拟的RANS方程方法；(2)研究适用于全尺度RN的物理模型。特别研究了两点壁函数法的有效性和优越性，并将其推广到考虑表面粗糙度对流动和阻力的影响。本文提出的小尺度船舶流动数值模拟方法是对现有方法的扩展，结合标准的κ-ε模型，可采用两种近壁模型，即两层法和两点壁函数法，具有考虑表面粗糙度影响的能力，后者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.