非线性波浪与可渗结构相互作用的SPH模型

发布时间：2019-07-05 18:14

【摘要】：波浪与可渗结构的相互作用包含波浪反射、透射、越浪和破碎等水动力过程,涉及到湍流、渗流和耗散等多种非线性物理效应,是一个作用机理十分复杂的非线性渗流力学问题。近年来随着全球气候变暖和海平面上升,海岸防护结构面临的海洋灾害威胁也日益加剧,开展波浪与可渗结构的相互作用研究具有十分重要的科学意义和工程应用价值。本文在修正光滑粒子流体动力学(SPH)方法核函数连续性的基础上,通过提出-种新的固壁粒子压力计算模式,解决了原SPH方法存在的边界处粒子分布紊乱、固壁边界附近压力场震荡以及流体粒子与固边界分离或穿透固边界问题。基于MPI空间域分解和OpenMP数据分解的耦合算法,结合动态负荷平衡技术,提出了适合现代计算集群资源配置的混合MPI-OpenMP并行算法,解决了三维SPH数学模型计算效率低的瓶颈问题。提出了适合无网格粒子法的主动吸收式造波边界条件、周期性侧边界条件和人工粘性消波边界条件,建立了基于SPH算法的周期波数值波浪水槽/水池。基于所建立的SPH数值波浪水槽/水池,结合非线性渗流本构关系,建立了模拟非线性波浪在多孔介质结构中流动的二维和三维湍流模型。推导了多孔介质内流体运动的体平均/Favre平均形式的双平均湍流控制方程(VAFANS),湍流应力采用亚粒子紊流模式来模拟,引入非线性渗流阻力项以反映介质固体骨架对孔隙内流体的阻力作用。通过在计算域内设置定义孔隙率信息的背景网格和引入表征密度的概念,将自由流动区域和不同孔隙率的渗流区域内的流体运动控制方程形式统一,避免在整个计算域内使用不同形式的控制方程导致的不同介质界面附近的压力震荡及速度跳跃现象。提出了不同介质界面处的过渡区边界条件和适合的过渡区宽度,保证了多孔介质界面处流场和压力场的计算精度。数值计算结果表明：所建立的二维SPH渗流模型比其它数值模型能更精确地模拟出溃坝波在可渗坝体内的传播、波浪在不同可渗性海床上的衰减、波浪透过可渗潜堤或出水堤时的变形、翻卷、破碎和越浪过程以及可渗结构附近的流场和湍流能分布特性。所建立的三维SPH渗流模型能够精确模拟溃坝波冲击可渗方柱、孤立波在可渗突堤处的绕射,以及周期波作用下分段式离岸潜堤附近的三维水动力特性,可精确捕捉到波浪在可渗结构周围复杂的波面演化过程以及平均水位和波生流空间分布特性。
文内图片：

图片说明：斥力边界布置
[Abstract]:The interaction between wave and permeable structure includes hydrodynamic processes such as wave reflection, transmission, wave crossing and breakage, which involves many nonlinear physical effects, such as turbulence, seepage and dissipation, and is a nonlinear seepage mechanics problem with complex action mechanism. In recent years, with the global warming and sea level rise, the threat of marine disasters faced by coastal protection structures is becoming more and more serious. It is of great scientific significance and engineering application value to study the interaction between waves and permeable structures. In this paper, on the basis of modifying the continuity of kernel function of smooth particle hydrodynamics (SPH) method, a new calculation model of solid wall particle pressure is proposed to solve the problems of particle distribution disorder at the boundary of the original SPH method, the shock of pressure field near the solid wall boundary and the separation or penetration of fluid particles from the solid boundary. Based on the coupling algorithm of MPI spatial domain decomposition and OpenMP data decomposition, combined with dynamic load balancing technology, a hybrid MPI-OpenMP parallel algorithm suitable for modern computing cluster resource allocation is proposed, which solves the bottleneck problem of low computational efficiency of 3D SPH mathematical model. The active absorption wave generation boundary conditions, periodic side boundary conditions and artificial viscous wave elimination boundary conditions suitable for meshless particle method are proposed, and the periodic wave numerical wave flume / pool based on SPH algorithm is established. Based on the SPH numerical wave flume / pool and the nonlinear seepage constitutive relation, a two-dimensional and three-dimensional turbulence model is established to simulate the flow of nonlinear waves in porous media structures. The double average turbulence governing equation (VAFANS), turbulent stress in the form of volume average / Favre average is deduced. The subparticle turbulence model is used to simulate the turbulent stress, and the nonlinear seepage resistance term is introduced to reflect the resistance effect of the solid skeleton of the medium on the fluid in the pore. By setting the background grid defining porosity information in the computational domain and introducing the concept of characterization density, the governing equations of fluid motion in the free flow region and the seepage region with different porosity are unified, so as to avoid the pressure shock and velocity jump near the interface of different media caused by different forms of governing equations in the whole computational domain. The boundary conditions of the transition zone and the suitable width of the transition zone at the interface of different media are put forward, which ensures the calculation accuracy of the flow field and pressure field at the interface of porous media. The numerical results show that the two-dimensional SPH seepage model can simulate the propagation of dam-break wave in permeable dam more accurately than other numerical models, the attenuation of wave on different permeable sea bed, the deformation, roll-up, breakage and surging process of wave passing through permeable dike or outlet embankment, as well as the distribution characteristics of flow field and turbulent energy near permeable structure. The three-dimensional SPH seepage model can accurately simulate the seepage square column of dam-break wave impact, the diffraction of solitary wave at the permeable embankment, and the three-dimensional hydrodynamic characteristics near the segmented offshore submersible embankment under the action of periodic wave. The complex wave surface evolution process and the spatial distribution characteristics of average water level and wave-generated current around the permeable structure can be accurately captured.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TV139.2

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