The generation of a rarefaction wave at the initiation of discharge from a storage silo is a phenomenon of scientific and practical interest. The effect, sometimes termed the dynamic pressure switch, may create dangerous pulsations of the storage structure. Owing to the nonlinearity, discontinuity, and heterogeneity of granular systems, the mechanism of generation and propagation of stress waves is complex and not yet completely understood.

The present study conducted discrete element simulations to model the formation and propagation of a rarefaction wave in a granular material contained in a silo. Modeling was performed for a flat-bottom cylindrical container with diameter of 0.1 or 0.12 m and height of 0.5 m. The effects of the orifice size and the shape of the initial discharging impulse on the shape and extent of the rarefaction wave were examined. Positions, velocities, and forces of particles were recorded every 10⁻⁵ s and used to infer the location of the front of the rarefaction wave and loads on construction members. Discharge through the entire bottom of the bin generates a plane rarefaction wave that may be followed by a compaction wave, depending on the discharge rate. Discharge through the orifice generates a spherical rarefaction wave that, after reflection from the silo wall, travels up the silo as a sequence of rarefaction–compaction cycles with constant wavelength equal to the silo diameter. During the travel of the wave along the bin height, the wave amplitude increases with the distance traveled. Simulations confirmed earlier findings of laboratory and numerical (finite element method) experiments and a theoretical approach, estimating the speed of the front of the rarefaction wave to range from 70 to 80 m/s and the speed of the tail to range from 20 to 60 m/s.

从存储筒仓中放电开始产生稀疏波是一种科学和实际意义的现象。这种效应有时称为动态压力开关，可能会在存储结构上产生危险的脉动。由于颗粒系统的非线性，不连续性和非均质性，应力波的产生和传播机理很复杂，尚未完全理解。

本研究进行了离散元素模拟，以对筒仓中包含的颗粒状材料中稀疏波的形成和传播进行建模。对直径为0.1或0.12 m，高度为0.5 m的平底圆柱形容器进行建模。研究了节流孔的大小和初始放电脉冲的形状对稀疏波的形状和程度的影响。每10 ^-5记录一次粒子的位置，速度和力 s并用于推断稀疏波前部的位置和建筑构件上的载荷。穿过仓的整个底部的放电会产生平面稀疏波，取决于放电速率，紧随其后的是压实波。通过孔口的放电会产生一个球形稀疏波，该稀疏波在从筒仓壁反射后，沿着一系列恒定频率等于筒仓直径的稀疏-压缩循环，沿着筒仓向上传播。在波沿仓高行进期间，波幅随行进距离而增加。模拟结果证实了实验室和数值（有限元方法）实验的早期发现以及一种理论方法，