A zonal hybrid approach coupling FNPT with OpenFOAM for modelling wave-structure interactions with action of current
A zonal hybrid approach coupling FNPT with OpenFOAM for modelling wave-structure interactions with action of current
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DOI：
10.12989/ose.2018.8.4.381
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发表时间：
2018-12
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影响因子：
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通讯作者：
Qian Li;Jinghua Wang;S. Yan;Jiaye Gong;Q. Ma
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文献类型：
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作者：
Qian Li;Jinghua Wang;S. Yan;Jiaye Gong;Q. Ma
本文提出了一种混合数值方法，结合了两相纳维-斯托克斯模型（NS）和完全非线性势理论（FNPT），用于模拟波-结构相互作用。前者控制结构附近的计算域，其中粘性和湍流效应非常显着，并通过 OpenFOAM/InterDyMFoam 进行求解，该方法利用有限体积法 (FVM) 和流体体积 (VOF) 进行相识别。后者涵盖了域的其余部分，其中流体可被视为不可压缩、无粘性和无旋，并使用准任意拉格朗日-欧拉有限元法 (QALE-FEM) 进行求解。这两个模型使用区域（空间分层）方法弱耦合。考虑到两个根本不同的模型控制的两个不同子域之间的边界处解的不一致，引入了松弛（过渡）区，其中速度、压力和表面高程被视为两个模型解的加权和。为了应对相关挑战并最大限度地提高计算效率，QALE-FEM 得到了进一步发展。其中包括任意拉格朗日-欧拉 FNPT 的推导以及应用稳健的梯度计算方案来估计速度。该混合模型适用于对带有或不带有跟随电流的单向波作用的固定水平圆柱体进行数值模拟。讨论了收敛性、弛豫区的优化、精度和计算效率。尽管使用分区方法的弱耦合的想法并不新鲜，但本混合模型是第一个将 QALE-FEM 与 OpenFOAM 求解器耦合和/或应用于数值模拟存在电流的波结构相互作用的模型。
This paper presents a hybrid numerical approach, which combines a two-phase Navier- Stokes model (NS) and the fully nonlinear potential theory (FNPT), for modelling wave-structure interaction. The former governs the computational domain near the structure, where the viscous and turbulent effects are significant, and is solved by OpenFOAM/InterDyMFoam which utilising the finite volume method (FVM) with a Volume of Fluid (VOF) for the phase identification. The latter covers the rest of the domain, where the fluid may be considered as incompressible, inviscid and irrotational, and solved by using the Quasi Arbitrary Lagrangian- Eulerian finite element method (QALE-FEM). These two models are weakly coupled using a zonal (spatially hierarchical) approach. Considering the inconsistence of the solutions at the boundaries between two different sub-domains governed by two fundamentally different models, a relaxation (transitional) zone is introduced, where the velocity, pressure and surface elevations are taken as the weighted summation of the solutions by two models. In order to tackle the challenges associated and maximise the computational efficiency, further developments of the QALE-FEM have been made. These include the derivation of an arbitrary Lagrangian- Eulerian FNPT and application of a robust gradient calculation scheme for estimating the velocity. The present hybrid model is applied to the numerical simulation of a fixed horizontal cylinder subjected to a unidirectional wave with or without following current. The convergence property, the optimisation of the relaxation zone, the accuracy and the computational efficiency are discussed. Although the idea of the weakly coupling using the zonal approach is not new, the present hybrid model is the first one to couple the QALE-FEM with OpenFOAM solver and/or to be applied to numerical simulate the wave-structure interaction with presence of current.