Developing Expression Method of Ship Hull Forms and Improvement of Ship Performance in Waves

我们完成了两年(1999-2000)的研究项目“船型表达方法的发展与船舶在波浪中的性能改进”。得出的主要结论如下：(1)明确了影响船舶在波浪中耐波性的主要参数是前后半体的垂直棱体系数和前半体的水平面面积系数。(2)为了准确估计船首形状和非线性定常扰动的影响，必须考虑船体线型光顺的影响。因此，我们研究了用B-Spline函数来描述船体线型的方法。(3)检验了现有理论对高速船舶耐波性评估的有效性。条带理论适用于航速小于Fn=0.4的情况。高速细长体理论是估算…最有用的方法更重要的是高速船舶的耐波性。通过将尾部作为干面处理，使朗肯面元法的计算结果得到了很大的改善。但对辐射力的精确估计是不够的。(4)与常规舰船相比，三维估计理论的估计精度相差不大。然而，船头的定常扰动对非定常波场有很大的影响。提出了考虑非线性定常扰动影响的非定常力估计方法，并通过与试验结果的比较，证实了该方法比现有方法更准确。(6)频域估计方法不足以估计随时间变化的非线性水动力。因此，我们尝试在时间域上发展估算方法，以开发出优良的船型。目前，对于一艘优良的常规船舶，用新开发的方法可以得到与现有方法相同的精确结果。较少

We have performed the Research Project titled "Developing Expression Method of Ship Hull Forms and Improvement of Ship Performance in Waves" for two years (1999-2000). The main conclusions obtained in this study are summarized as follows :(1) We make clear that the parameters which strongly affected the seakeeping qualities of ship in waves are the vertical prismatic coefficients of the fore and the aft half body and the water plane area coefficient of the fore half body.(2) It is necessary to take into account the lines fairing of a ship hull form to estimate accurately the effect of bow form and the nonlinear steady disturbance. Therefore, we have investigate the method to describe the lines of the ship hull form by using the B-spline function.(3) We have examined the validity of the existing theories estimating the seakeeping qualities of a high-speed vessel. Strip theory is valid for ship speed less than Fn=0.4. High-speed slender-body theory is the most useful method for estimatio … More n of seakeeping qualities of high-speed vessel. The results of Rankine panel method are much improved by dealing with the transom stern as the dry surface. However, it is not enough for accurate estimation of radiation forces.(4) The differences of estimation accuracies due to 3-D estimation theories are small with respect to a fine conventional ship. However, the steady disturbance due to a bow strongly affects the unsteady wave field. Thereby, the Rankine panel method is recommended for estimation of seakeeping qualities because it can easily take into account the effect of steady disturbance.(5) We have developed the estimation method of unsteady forces that takes into account the effect of nonlinear steady disturbance, and have confirmed that it is more accurate method than the existing methods by comparing with the experimental results.(6) The estimation methods in frequency domain are not enough for estimating the nonlinear hydrodynamic forces depending on a time. Therefore, we have tried to develop the estimation method in time domain for developing the excellent ship hull form. At present, we can get the same accurate results as the existing method by using the newly developed method for a fine conventional ship. Less