典型海况下的船型优化研究

发布时间：2018-07-30 08:49

【摘要】：传统的船型优化一般基于静水阻力最低，以静水中的快速性来衡量船型的好坏。而实际上，一艘船舶在其营运的绝大多数时间内都是在不同海况下航行的，船舶会受到由于波浪引起的阻力增值，静水中快速性好的船其波浪中的快速性不一定也是好的。此外，降低船舶的航行阻力、减少主机功率也是减小燃油消耗、降低碳排放的关键。本文以一艘30万吨级的油船作为研究对象，以波浪中的总阻力最低作为目标函数，通过构建基于静水阻力和波浪增阻的集成优化系统实现了船型的自动优化，得到了波浪中总阻力最低的船型，并通过数值计算和模型试验结果的对比分析验证了优化结果。首先，在系统梳理静水阻力和波浪增阻的数值计算方法及船型优化研究现状的基础上，提出了基于CAD与CFD相结合的SBD（Simulation Based Design）技术开发波浪中总阻力最低的船型集成优化系统的研究目标。其次，论证了波浪中总阻力最低的船型集成优化系统中采用静水阻力和波浪增阻的数值预报方法，并检验了阻力数值预报精度和反映船型变化的灵敏度，结果表明所采用计算方法虽存在一定的误差，但都能正确的预报出船体阻力随船型变化的趋势。第三，，为实现波浪增阻计算软件在船型自动优化过程中的集成应用，开发了专门的增阻计算前处理接口程序，实现了常用标准几何模型向增阻计算所需几何模型的快速转换。通过若干案列的几何模型拟合度分析和增阻计算结果对比，检验了接口程序的精度和实用性，同时也证明了采用三次B样条曲线拟合船体曲线的适用性。第四，针对一艘30万吨级油船，在Friendship软件中构建了全参数化模型，开发了基于波浪中总阻力（含静水阻力和波浪增阻）的集成优化系统。经试验设计方法和遗传算法二次优化得到了波浪中总阻力小的新改船型。并通过与原型及原改型的数值计算结果和模型试验结果的对比，检验了船型集成优化系统的可行性。参数化船型自动集成优化系统突破了以往船型优化主要依赖设计者经验的传统模式，大大提高了优化效率。最后，针对短波增阻精确预报这一波浪增阻数值计算难点，结合重叠网格技术，采用Level set方法捕捉自由面，应用SSTk湍流模型封闭并求解RANS方程和运动方程，获得了船舶在静水中和波浪中航行时所受到的阻力，初步探索了短波增阻的全粘流数值模拟方法。此外，通过实例对其精确度进行了验证，发现计算结果与试验结果相比尚存在一定的差距，有待进一步的研究。
[Abstract]:The traditional ship shape optimization is generally based on the lowest static water resistance, and the ship shape is measured by the speed in the still water. In fact, a ship is sailing in different sea conditions for most of its operation. The ship will be increased by the resistance caused by the wave, and the speediness of the ship with a good speed in the still water is not fast. In addition, reducing the resistance of the ship and reducing the power of the host are also the key to reduce fuel consumption and reduce carbon emissions. In this paper, a 300 thousand ton tanker is taken as the research object, with the minimum total resistance in the wave as the objective function, the integrated optimization system based on the static water resistance and wave resistance increase is realized. The ship shape is automatically optimized, and the ship hull with the lowest total resistance is obtained. The optimization results are verified through numerical analysis and comparative analysis of the model test results.
First, on the basis of the numerical calculation method of static water resistance and wave resistance increasing and the status of ship shape optimization, the goal of developing the ship type integrated optimization system based on the SBD (Simulation Based Design) technology based on CAD and CFD is proposed to develop the lowest total resistance of the wave in the wave.
Secondly, the numerical prediction method of static water resistance and wave increasing resistance in the ship type integrated optimization system with the lowest total resistance in the wave is demonstrated, and the numerical prediction precision of resistance and the sensitivity of the ship shape change are tested. The results show that although there is a certain error in the calculation method, the hull resistance can be correctly predicted with the ship. The trend of type change.
Third, in order to realize the integrated application of the wave increase resistance calculation software in the automatic optimization of the ship type, a special preprocessing interface program is developed, which realizes the rapid conversion of the common standard geometric model to the geometric model of the increase resistance calculation. The accuracy and practicability of the interface program are verified, and the applicability of the three B spline curve fitting hull curve is also proved.
Fourth, for a 300 thousand ton tanker, a fully parameterized model is built in Friendship software, and an integrated optimization system based on the total resistance in the wave (including static water resistance and wave resistance) is developed. The new modified ship model is obtained by the experimental design method and the genetic algorithm in two times. The feasibility of the ship type integrated optimization system is tested by the comparison between the numerical results and the model test results. The parametric ship type automatic integration optimization system breaks through the traditional model which mainly depends on the designer experience of the previous ship shape optimization, and greatly improves the optimization efficiency.
Finally, in order to predict the difficulty of the numerical calculation of the wave increasing resistance accurately, the Level set method is used to capture the free surface, and the SSTk turbulence model is used to seal and solve the RANS equation and motion equation, and the resistance of the ship to the navigation in the still water and the waves is obtained. In addition, the accuracy of the numerical simulation is verified by an example. It is found that there is still a gap between the calculated results and the experimental results, which needs further study.
【学位授予单位】：中国舰船研究院
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U662

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