IBM-VOF数值模拟方法在船舶水动力分析运用

发布时间：2019-01-05 15:57

【摘要】：船舶与海洋工程水动力系数测试已从主要依靠物模试验发展到运用计算流体力学(CFD,Computational Fluid Dynamics)数值求解方法。其中,船舶在自由液面运动属于复杂边界流固耦合问题,需要处理自由表面边界及船舶剖面边界,是数值计算方法中的重点和难点之一。不同于一般贴体网格计算流体数值模拟方法,本文基于笛卡儿网格,结合浸入边界法(IBM,Immersed boundary method)和流体体积法(VOF,Volume of fluid)建立了新型的水、气和固伪三相流数值水池求解器,以进行船舶与海洋工程“仿物理”数值模拟实验。在IBM-VOF数值模型中,基于笛卡尔网格系统采用压力增量投影法求解N-S方程,并应用IBM算法虚拟船舶表面边界条件,利用PLIC-VOF(PLIC,Piecewise Line Interface Calculation)方法追踪更新网格流体体积所占比例F,模拟流场中自由表面变化。为了避免求解复杂船型型线边界表面压力引起的数值偏差,在处理船舶与海洋结构物所受表面边界力时本文创新性采用IBM体积力求解方法。为了验证算法的适应性,本文基于IBM-VOF数值模型在数值水池中对S60船模典型船舯剖面进行垂向、横向和横摇强迫振荡数值试验,计算结果表明,船型剖面的附加质量和阻尼系数与前人CFD-RANS数值方法计算结果与实验数据非常吻合。这说明IBM-VOF数值模型能够很好地解决船型剖面水动力仿真计算问题。基于此,本文应用IBM-VOF数值模型开展典型船舶模型水动力分析仿真应用。首先,对S60船模三个特殊典型剖面进行横摇振荡仿真试验,研究其摇荡幅值变化、周期变化、附体加载下船型剖面所受流体水动力变化,通过与CFD-RANS数值计算结果比较,进一步验证了IBM-VOF方法在处理二维船型剖面水动力性能的可靠性和准确性。最后,结合切片理论,利用IBM-VOF数值模型对S175三维集装箱船进行水动力数值模拟计算。计算结果表明基于IBM-VOF方法的S175船舯横剖面切片水动力系数与基于CFD-RANS数值方法计算结果基本一致;同时,与基于AQWA软件计算的S175三维集装箱船水动力系数比较分析可知,IBM-VOF方法能够完整考虑船舶在垂荡等运动中的粘性、涡泄等非线性因素影响,因此计算结果更贴近实际情况,这表明本文IBM-VOF方法在解决船舶与海洋工程实际水动力性能问题具有可行性和有效性,有助于船舶数值水池的工程应用和扩展,也为准确预报船舶耐波性提供一种新的可能性。
[Abstract]:The hydrodynamic coefficient measurement of ship and ocean engineering has developed from mainly relying on physical model test to using computational fluid dynamics (CFD,Computational Fluid Dynamics) numerical solution method. Among them, the ship moving in the free liquid surface is a complicated boundary fluid-solid coupling problem, which needs to deal with the free surface boundary and the ship section boundary, which is one of the key and difficult points in the numerical calculation method. In this paper, a new type of water is established based on Cartesian meshes and immersion boundary method (IBM,Immersed boundary method) and fluid volume method (VOF,Volume of fluid), which is different from the general fluid numerical simulation method of body-fitted meshes. A numerical tank solver for gas and solid pseudo-three-phase flow is used to simulate the ship and ocean engineering. In the IBM-VOF numerical model, the pressure increment projection method is used to solve the N-S equation based on the Cartesian grid system, and the IBM algorithm is used to simulate the ship's surface boundary condition, and PLIC-VOF (PLIC,) is used to solve the N-S equation. The Piecewise Line Interface Calculation) method tracks the fraction of fluid volume in the updated grid and simulates the free surface variation in the flow field. In order to avoid solving the numerical deviation caused by the boundary pressure of complex ship form line, the IBM volume method is innovatively used to solve the surface boundary force between ship and ocean structure. In order to verify the adaptability of the algorithm, the vertical, transverse and rolling forced oscillations of the typical midship section of S60 ship model are carried out in a numerical pool based on the IBM-VOF numerical model. The results show that, The additional mass and damping coefficient of the ship profile are in good agreement with the experimental data. This shows that the IBM-VOF numerical model can solve the hydrodynamic simulation problem of ship profile. Based on this, the IBM-VOF numerical model is used to simulate the hydrodynamic analysis of typical ship model. First of all, three typical sections of S60 ship model are tested by rolling oscillation simulation test, and the variation of rocking amplitude, period and hydrodynamic changes of ship profile subjected to appendage loading are studied. The results are compared with the results of CFD-RANS numerical calculation. The reliability and accuracy of the IBM-VOF method in dealing with the hydrodynamic performance of two-dimensional ship profile are further verified. Finally, based on slice theory, the hydrodynamic numerical simulation of S175 3D container ship is carried out by using IBM-VOF numerical model. The results show that the hydrodynamic coefficients of S175 ship midship section based on IBM-VOF method are in good agreement with those based on CFD-RANS method. At the same time, comparing with the hydrodynamic coefficients of S175 container ship calculated by AQWA software, it is found that the IBM-VOF method can fully consider the influence of nonlinear factors such as viscosity, vortex discharge and so on. Therefore, the calculation results are closer to the actual situation, which shows that the IBM-VOF method in this paper is feasible and effective in solving the actual hydrodynamic performance problems of ship and ocean engineering, and is helpful to the engineering application and expansion of ship numerical pool. It also provides a new possibility for accurate prediction of ship's wave-resistance.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U661.1

【参考文献】