DEVELOPMENT OF OPTIMIZATION PROCEDURE IN COMPUTATIONAL HYDRODYNAMICS

本研究的目的是将计算流体力学和非线性规划的科学方法应用于船型设计问题。在1994-1995年的研究期间，在船体阻力和流动的CFD预报、粘性流动反问题的新公式、最优化问题在船型改进中的应用、船模验证试验等方面取得了新的进展。在1993财政年度，改进了船体单位变形灵敏度系数的公式，并实现了B-Spline函数在船型表达式中的实现。这些改进被用于最小化二维体粘性阻力的优化问题。尝试用数学公式将二维方法扩展到三维问题。为了检验计算网格和计算结果的有效性，还尝试了三维计算机图形工具的发展。上一个1994财政年度一直致力于改进二维基本问题和三维高级问题的研究。在计算问题中，一个反问题描述了船体上的压力分布和/或尾流区的速度分布，以获得合适的机身形状。计算结果表明，该方法可以安全地推广到实际的三维船舶问题。第二个尝试是将优化方法应用于实际船型的兴波阻力最小化问题，将B-样条函数应用于船体表示，并采用线性兴波阻力计算方法。已成功开发了多种图形模块，用于船体外形和计算网格的表示以及计算结果的验证。这些模块也可用于解决其他船体结构问题。

The objectives of the present research are to apply the scientific procedures of computational fluid dynamics and the nonlinear programming to the ship form design problem. During the research period of 1994 to 1995, developments have been made on CFD predictions of ship resistance and flow, a new formulation of inverse prblem in viscous flow, applications of optimization problem to the improvement of ship form, and validation experiments using ship models.In the 1993 fiscal year, improvements were made on the formulation of the sensitivity coefficients due to unit deformation of a body, and implimentation of B-spline function for the body form expression. These improvements were utilized in the optimization problem for minimizing 2-D body viscous resistance. Mathematical formulations was attempted to extend the 2-D method to 3-D problem. Developments on 3-D computer graphic tools were also attempted to examine the validity of the computational grids and the computational results.The last 1994 fiscal year has been devoted to the researches of improvement of the 2-D fundamental problem, and the 3-D advanced problems.In the computational problem, an inverse problem specifying the pressure distribution on the body hull and/or the velocity profile in the wake region for obtaining the proper body shape. The computational results have revealed that this method will safely be extented to 3-D actual ship problem. The second attempt is an application of the optimization method to the wave-resistance minimization problem for practical ship forms, by applying the B-spline function to ship hull presentation and by using linear wave resistance calculation methods. The results have been validated well by model ship experiments.Many graphic modules have successfully been developed for the presentation of the ship hull form and computational grids, and for the validation of the computational results. These modules can also be used for other ship hull configuration problems.