LDV measurements of an air-solid two-phase flow in a vertical pipe

Abstract

Measurements of air and solid-particle velocities were made in a vertical pipe two-phase flow by the use of a laser-Doppler velocimeter (LDV). Five kinds of plastic particles, diameters of which ranged from about 3 mm to 200 μm, were transported in a vertical pipe of 30 mm inner diameter. It was found that, the smaller the particle size, the flatter was the mean air velocity distribution for the same mass flow ratio of solids to air. Large particles increased air turbulence throughout the pipe section, while small particles reduced it. Both effects of promotion and suppression of turbulence were observed at the same time in the presence of particles of medium size, that is, the turbulence was increased around the pipe centre and reduced near the wall. The frequency spectrum of air turbulence normalized by the turbulence intensity was not changed by the large particles. In the presence of the small particles, the higher-frequency parts of the spectrum increased.

Numerical simulation and validation of dilute turbulent gas–particle flow with inelastic collisions and turbulence modulation

“…The solution has been verified to be grid independent by checking that an increase in the number of grid points had a negligible effect on the computed profiles. Experimental data [12] r/R √ Θ s /U cl Fig. 5.…”

“…The production rate of fluctuating kinetic energy in the solid-phase is exclusively due to the kinetic and collisional stress tensors acting upon the mean velocity gradient. There is no production rate related to concentration gradients as suggested by the general form in (12). This is a direct result of the kinetic theory approach.…”

“…Predicted mean velocities and turbulence intensity profiles are compared with a single set of measurements of Tsuji et al [12]. The representative case chosen for validation comprises polystyrene beads with density ρ s = 1020 kg/m 3 and diameter d s = 200 µm.…”

“…Turbulent gas-solid flow in a vertical pipe is chosen as the test case for validation of two-fluid model performance. The simulation results are compared with existing experimental data [12] obtained from laser Doppler velocimetry (LDV).…”

Numerical and experimental study of horizontal pneumatic transportation of spherical and low-aspect-ratio cylindrical particles

“…Lun [20] compared simulation results of mean gas and particle velocities and carrier phase turbulence intensity with the experimental measurements of Tsuji et al [21] for a dilute steady state flow in vertical pneumatic conveying. A modified k- turbulence model was used to take into account the effect of particles on the fluid phase turbulence level.…”