DPTM simulation of aeolian sand ripple

Aeolian sand ripple and its time evolution are simulated by the discrete particle tracing method (DPTM) presented in this paper. The difference between this method and the current methods is that the former can consider the three main factors relevant to the formation of natural aeolian sand ripples,which are the wind-blown sand flux above the sand bed formed by lots of sand particles with different di-ameters,the particle-bed collision and after it the rebound and ejection of sand particles in the sand bed,the saltation of high-speed sand particles and the creep of low-speed sand particles,respectively. The simulated aeolian sand ripple is close to the natural sand ripple not only in basic shape and characteristic,particle size segregation and stratigraphy,but also in formation stages. In addition,three important speeds can be obtained by this method,which are the propagation speed of the saturated aeolian sand ripple and the critical frictional wind speeds of emergence and disappearance of sand ripple.

COREX熔化气化炉物料运动行为

基于离散元方法，建立了二维扁平熔化气化炉的离散元模型，应用此模型从颗粒尺度对物料运动流型、速度场以及空隙度分布进行了研究。结果表明：采用加入示踪颗粒的方法，对颗粒运动流型进行分析，示踪颗粒层逐渐由直线型变为两侧向下弯曲型；从物料速度场分布可以看出，炉内存在死料柱区、活塞流区以及管道流区等运动区域。回旋区对炉内竖直方向速度分布的影响限于距炉缸底部上方0．18m处，回旋区半径的减小导致炉内颗粒活跃区域缩小，死料柱区高度增加；炉内物料运动存在一定的偏析现象，该现象也可从空隙度分布看出。炉内死料柱区空隙度为0．37左右，回旋区处为0．65左有，位于自由空间下方和死料柱区以及回旋区之间的活塞流区空隙度在O．37～0．65之间。