水底管道抛石加固过程的DEM-SPH耦合分析

水底管道的抛石加固过程是典型的颗粒-流体耦合问题.采用DEM-SPH耦合方法模拟颗粒-流体系统,其中离散元方法(DEM)用于模拟落石,光滑粒子流体动力学方法(SPH)用于模拟流体.通过三维Voronoi切割算法生成不规则形状的多面体,并基于闵可夫斯基原理构造扩展多面体形态的落石单元.通过SPH的边界排斥力模型计算颗粒与流体间的作用力,从而建立DEM-SPH耦合方法.采用该方法模拟溃坝与楔形块入水的过程,将计算结果与试验结果及其他数值结果进行对比分析,分别验证了 SPH与DEM-SPH耦合方法的合理性.建立锥形结构模拟卸料斗和水底管道,采用DEM-SPH耦合方法模拟落石通过卸料斗入水并与水底管道相互作用的过程,确定了落石和水对管道的作用力,并分析了卸料斗静止与运动时的落石堆积情况.以上研究表明,DEM-SPH方法可有效模拟颗粒材料、水和工程结构的相互作用,可进一步应用于水下抛石过程的结构和参数设计.

Coupled DEM-SPH simulations of rock dumping in waters for pipeline reinforcement process

Rock dumping,including falling into the water and impacting on the pipeline,is a typical particle-fluid coupling system.The fluid-solid coupling model can be adopted to simulate the particle-fluid system,in which the discrete element method (DEM) is used to simulate the rocks and the weakly compressible smooth particle hydrodynamic method (SPH) is used to simulate the water.The irregularly shaped polyhedra are generated with the 3D Voronoi tessellation algorithm,where the dilated-polyhedron-shaped rocks can be generated according to the Minkowski sum theory.The repulsive force model in the SPH is employed to calculate the interaction between the dilated polyhedra and SPH particles.Accordingly,the DEM-SPH coupling method can be established.The dam break and free-falling of a wedge into water are simulated to validate the SPH and DEM-SPH coupling method.The discharge hopper and the submarine pipe are constructed by the cone-tube structure.The contact model between the dilated polyhedron and cone-tube structure is investigated by the simulation of the rocks free-falling from the discharge hopper into the cylindrical container.The rocks dumping into the water and interacting with the submarine pipe are simulated with the DEM-SPH coupling method.The interacting force on the pipe from the rocks and water is determined,while the rock accumulations are analyzed.The results indicate that the proposed DEM-SPH coupling method is an effective approach to simulate the interaction between granular material,water,and engineering structure,and can be further applied in the structure and parameter design of the rock dumping process.