Research On The Impact Of The Flow Properties Of Two-dimensional Granular Flow Of Random Force Field

Granular flow exists extensively in nature, which is different from normal gas and liquid flow. The granular flow is always divided into dilute and dense flow states, and the dilute-dense flow transition is easily found. In this dissertation, granular flow driven by self-gravity in a two-dimensional channel with an external random force field is investigated by molecular dynamics simulation. The results show that different flow states and their transitions can be controlled by adjusting external random force field.First, the influence of height of external random force field on granular flow is studied. At the range of low height of external random force field, an increase of height results in decrease of both the maximum dilute flow rate and the dense flow rate, while they increase with increase of height at the range of high height of external random force field, Second, the effect of intensity of external random force field on granular flow is then conducted. The dilute-dense flow transition still exists when the intensity of external random force field is less than the critical value frc. Furthermore, the area of metastable dilute flow state and unstable dense flow state shrinks when the intensity of external random force field increases. At the point of the critical external random force field, the characteristic of dilute-dense flow transition disappears and the metastable dilute flow state, the unstable dense flow state and the stable dense flow state converges together. When the intensity of external random force field is larger than frc, granular flow goes in a mixed flow state having both the dilute and dense flow states.Two competing effects of external random force field, increasing energy effect and dissipation energy effect, are thus proposed to explain the observed results. The former is to increase averaged particles’ kinetic energy, and the latter is to reduce the consistency of granular low and decrease averaged particles’kinetic energy. At the range of low intensity of external random force field, the dissipation energy effect plays main role, which leads to decrease of the maximum dilute flow rate in dilute flow state. In dense flow state, increasing energy effect takes main effect, which results in increase of the dense flow rate. When external random force field is large enough, increasing energy effect takes absolutely effect, and the flow rate increases with an increase of external random force field.