泥石流冲击桥墩绕流过程模拟与试验分析

Numerical Simulation and Experiment Analyses of Debris Flow Movement around Bridge Pier

泥石流与桥墩动力相互作用包括泥石流对桥墩的冲击淤埋作用及桥墩对泥石流运动过程的反向影响,其中涉及复杂的流固耦合,是学术界关注的热点问题。为研究泥石流绕流桥墩过程,在纳维斯托克斯方程的基础上结合深度平均理论,考虑泥石流固液两相的特点,构建了泥石流-桥墩流固耦合物理模型,并基于有限体积法建立时间和空间尺度上具有2阶精度的高效数值算法,实现了泥石流绕桥墩运动全程模拟,与室内试验成果进行了对比验证。结果表明:不同粘度的泥石流冲击桥墩绕流过程有显著不同,相同初始条件下粘性泥石流堆积厚度较大,运动速度较小,堆积范围较小;反之,稀性泥石流堆积厚度较小,运动速度较大,堆积范围也较大。数值模拟结果与室内模型试验非常接近,验证了物理模型的适用性。

The dynamic interactions between debris flow and piers comprise the impact of debris flow on piers and the resulting reverse effects of piers on the mobility of debris flow,involving complex fluid-solid coupling,and it is one of the most concerns in academic society.To investigate the behavior of debris flow moving around bridge piers,a two-dimensional physical model of debris flow-bridge pier was constructed based on Navier-Stokes equations combined with depth-averaged theory,where the characteristics of solid-fluid two-phase debris flow were included in the study.An efficient numerical algorithm with two-order precision on the time and space scales was established based on finite volume method to simulate the process of debris flow with varied viscosities striking bridge piers.Results showed that the high solid volume fraction could reduce the debris flow mobility and affect deposition shape of debris flow significantly;Viscous debris flow led to greater thickness in debris accumulation at flume outlet but smaller size of debris fan,and a higher kinematic velocity than micro-viscous debris flow under the same initial conditions.The result of numerical simulation was consistent with that of laboratory tests,suggesting the applicability of the proposed physical model.