Experimental measurements of particle collision dynamics in a pseudo-2D gas-solid fluidized bed

- Particle-particle collisions are identified by particle trajectories obtained from optimized PTV measurements.
- Detailed comparison is conducted between experiments and the theoretical collision model in terms of collision frequency.
- Granular temperature is analyzed at microscopic and macroscopic scales.
- Particle impact velocity correlates linearly with the square root of granular temperature

Based on particle tracking velocimetry (PTV) measurements by Hagemeier et al. (2014), the particle tracking approach is further optimized to accurately measure complex granular flows in a pseudo-2D fluidized bed. The particle granular temperature, particle collision frequency and impact velocity are systematically investigated under various operation conditions. Collision events are identified by a self-developed algorithm based on the variation of individual particle trajectories obtained from PTV measurements.The circulation pattern of particles in the fluidized bed can be well represented using the time-averaged volumetric flux of particles. The evaluation of granular temperature depends on the size of the investigation region. The value of granular temperature and the corresponding anisotropy significantly decrease as the size of the investigation region varies from 45 times particle diameter to 6 times particle diameter. Compared to the collision model of the kinetic theory of granular flow, the experimental collision frequency tends to be relatively constant or even decrease after exceeding a critical solid volume fraction. This is a result of competing contributions of increasing solid volume fraction and decreasing granular temperature. The average impact velocity correlates linearly with the average square root of granular temperature. The slope of this linear equation depends on the location within the fluidized bed.

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