DEM-CFD simulation for mixing process of binary particles with large size difference in a bubbling fluidized bed

In practical applications of fluidized beds, the size of solid materials is not uniform and large solids coexist with small solids. The large size difference significantly influences the mixing and segregation phenomena in the beds. However, these behaviors are not fully understood. In the present study, a large-scale DEM-CFD coupling simulation (1) for a pseudo-2D bubbling fluidized bed of binary particles with large size difference is performed. Momentum exchange between larger particles and fluid is expressed by fictitious particle method by Tsuji et al. (2). A particle mixture consists of two kinds of spherical particles with 1 mm diameter and 2500 kg/m3 density and 20 mm diameter and 1600 kg/m3 density. The number of the smaller particles is twenty five million and that of the larger particles is five hundred. The particle mixture is initially in completely separated state, and mixing process of the particles is investigated. The snapshot of the simulation result is shown in Fig. 1. We can observe that the large particles are mixed by bubbles occurring in the bed. Please click Additional Files below to see the full abstract

Seismic exploration at Fuji volcano with active sources : The outline of the experiment and the arrival time data

Fuji volcano (altitude 3,776m) is the largest basaltic stratovolcano in Japan. In late August and early September 2003, seismic exploration was conducted around Fuji volcano by the detonation of 500 kg charges of dynamite to investigate the seismic structure of that area. Seismographs with an eigenfrequency of 2 Hz were used for observation, positioned along a WSW-ENE line passing through the summit of the mountain. A total of 469 seismic stations were installed at intervals of 250-500 m. The data were stored in memory on-site using data loggers. The sampling interval was 4 ms. Charges were detonated at 5 points, one at each end of the observation line and 3 along its length. The first arrival times and the later-phase arrival times at each station for each detonation were recorded as data. P-wave velocities in the surface layer were estimated from the travel time curves near the explosion points, with results of 2.5 km/s obtained for the vicinity of Fuji volcano and 4.0 km5/s elsewhere