Análise espectral de sinais de flutuação de pressão obtidos da fluidodinâmica computacional de leitos fluidizados

Abstract

In this study, spectral analyses of pressure fluctuation signals obtained from computational simulations of fluidized beds were done. The simulations were performed using ANSYS FLUENT 14.0. The multiphase model employed was the Euler-granular two-fluid model (TFM). The solid stresses were modeled by the kinetic theory of granular flows (KTGF). Two beds were simulated, a two-dimensional bed in fast fluidization regime and a three-dimensional bed in bubbling and turbulent regimes, both with Geldart-B particles. The pressure fluctuation signals generated by numerical simulations were analyzed via power spectral density. The minimum simulation periods to generate statistically significant signals were identified, as well as the minimum sampling rate required for the processing of signals, which were found equal to 325 and 250 Hz, respectively. In the 3D bed, the bubbling system was characterized by peaks at frequencies of 1.5 and 2.2 Hz, while the fast fluidization regime simulated in 2D was characterized by a peak at a frequency of 0.12 Hz, which may be related to the rate of motion of clusters. A major difference between the power spectra of bubbling and turbulent regimes was observed. In the bubbling regime, two frequency peaks may be identified, while in turbulent regime only one frequency peak appears.