基于沿程坐标积分模式颗粒流与结构物阵列相互作用的数值模拟

近年来, 由颗粒物质流动主导的泥石流、滑坡等自然灾害评估及其防护工作越来越受到人们的关注. 本文基于沿程坐标积分模式建立了陡峭地形条件结构物作用下颗粒流运动的数值模型, 可以较为准确地表征陡峭地形情形结构物影响下颗粒流的流态特征和运动过程, 尤其是相互作用过程中激波结构的形成与演化, 颗粒流的反射、绕射和爬升等动力效应. 通过数值模拟研究了颗粒流与不同分布密度四面体结构物阵列相互作用时的流态演化与堆积形貌, 提出了新型偏转效率无量纲指标, 结合流通效率, 定量评估了四面体结构物阵列对颗粒流流通距离和侧向铺展特征的影响. 结果表明, 单个四面体结构物对颗粒流的作用包括耗散作用和偏转作用两种模式, 其中偏转作用尤为显著; 结构物阵列对颗粒流产生综合的耗散和偏转作用, 通过多级作用形成系列的弓形激波耗散颗粒流能量, 通过偏转作用分隔和改变颗粒流路径, 增强耗散作用, 调控堆积形态, 可望对下游地区产生显著的防护效果. 

NUMERICAL STUDY OF INTERACTION BETWEEN GRANULAR FLOW AND AN ARRAY OF OBSTACLES BY A BED-FITTED DEPTH-AVERAGED MODEL

The impact of granular flow such as debris flow and landslide, and how to design obstacles to deflect granular hazard, are becoming more and more important recently. In this study a bed-fitted depth-averaged model is established to simulate the interaction between granular flow and obstacles on steep terrains, which is able to simulate the birth and evolution of shock wave, reflection, bypass and runup during interaction between granular flow and obstacles on steep terrains. A series of numerical simulations concerning granular flows interacting with an array of tetrahedral obstacles of different distributions were conducted. A new dimensionless index called deflection efficiency was proposed, and the effects of tetrahedral obstacle arrays on the flow distance and lateral spreading characteristics of granular flow were quantitatively evaluated. A single tetrahedral obstacle plays a role of dissipation and deflection on granular flow, the latter of which even more obviously changes the granular flow pattern. An array of tetrahedral obstacles shows a comprehensive action of dissipation and deflection on granular flow, where multilevel actions dissipate energy in granular flow through bow shocks, and the splitting and changing actions on the flow path deflect granular flow. The obstacle system could control the final deposit to produce a protection region downstream.