基于格子Boltzmann方法的三维溃坝数值模拟
Three-dimensional Numerical Simulation of Dam Break Based on Lattice Boltzmann Method
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摘要: 为了模拟溃坝水流的流动过程,在基于格子Boltzmann方法(LBM)的基础上采用壁面适应局部涡流黏度的大涡模拟模型,引入自由滑移法处理固壁边界条件,模拟瞬时全溃坝以及瞬时局部溃坝水流的流动过程,并就瞬时全溃坝时两种消能坎的消能效果进行比较。数值模拟结果表明:基于LBM方法的数值模拟方法可以准确模拟瞬时全溃坝水流演进过程中流体自由表面的流动情况以及速度变化规律;瞬时局部溃坝在0.38 s到达障碍物时障碍物周围水深爬高后绕障碍物流动,水流对障碍物的作用力体现了水流流动的不稳定性;溃坝时在坝前设障碍物可以明显观察到液体撞击障碍物后的飞溅程度和形成的水舌,通过两种不同消能坎下流体撞击壁面后产生的压强可以判断有孔障碍物的消能能力更好,水流对无孔障碍物作用力更大。研究结果可为进一步研究LBM方法与VOF法相结合捕捉流体自由面变形及飞溅提供参考。Abstract: In order to simulate the flow process of dam break flow,a large eddy simulation model based on Lattice Boltzmann Method(LBM)is adopted to adapt the wall viscosity. The free slip method is introduced to deal with the wall fixed boundary conditions. The flow process of instantaneous total dam break and instantaneous local dam break flow is simulated. The energy dissipation effects of the two kinds of energy dissipation sills are compared. The numerical simulation results show that:the LBM-based numerical simulation method can accurately simulate the flow situation and velocity variation law of the fluid free surface in the instantaneous dam break flow evolution process. When the instantaneous local dam break reaches the obstacle at 0.38 s,the water depth around the obstacle climbs and flows around the obstacle,and the force of the flow on the obstacle reflects the instability of the flow;the flow breaks through the dam. When the barrier is set in front of the dam,the splashing degree and the water tongue is formed after the liquid impacts the obstacle can be observed obviously. According to the pressure generated by the fluid impacting the left wall under two different energy dissipation sills,it can be judged that the energy dissipation capacity of the porous barrier is better,and the strength requirement of the structure without porous barrier is higher under the flow force. The results can provide a reference for a further study of LBM method combined with VOF method to capture free surface deformation and splash.