Estudo da dinâmica de partículas em tambores rotatórios empregando a abordagem numérica lagrangeana

Abstract

The understanding of the behavior of the particles inside the rotating drum is fundamental for the improvement of its efficiency. By allowing the individual monitoring of each particle, the Lagrangean numerical approach is an excellent tool to aid studies in particulate systems. Thus, the purpose of this work was to determine the combinations of the numerical parameters of the Lagrangean approach that best represent the dynamics of the particles inside a rotating drum for different types of materials under different operating conditions. Experimental methodologies for the determination of the coefficients of restitution, static friction and rolling friction were tested and validated for particle-particle and particle-wall interactions. The experimental values of these coefficients were applied in the model to verify if they would be representative in a bulk effect in the rotatory drum. A calibration process was also performed to determine the best combination of parameters and to compare it with the results of the experimental coefficients. The experimental apparatus used was suitable for the measurement of each of the coefficients. Since the value of the coefficient of restitution depends on the thickness of the material in which the particles are colliding, while in order to determine the coefficient of static friction correctly it is necessary to use the glued spheres to avoid rolling and to ensure correct measurement of the parameter. The values found in the calibration and the values of the measured parameters showed good agreement when compared with the experimental data and the Eulerian approach reported in the literature, for materials of different physical properties under different operating conditions. These were also able to successfully describe the transitional phenomena of different flow regimes. The values found in the calibration process were: 0.80 and 0.50 for the coefficient of static friction, 0.03 and 0.06 for the coefficient of rolling friction, particle-particle and particle-wall respectively, while for the measured experimentally were 0.80 and 0.49 for particle-particle and particle-wall static friction and 0.011 and 0.054 for particle-particle and particle-wall friction respectively. The results were close, showing that the calibration process was able to preserve the physical meanings of the parameters.