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12th Spring School on Transition and Turbulence
Comparison between CFD models coupled to an acoustic pressure model to represent gas-solid flows in a CFB riser under the influence of ultrasound
Vivien Rossbach , SC
Co-Authors: Vivien Rossbach, Sarah Laysa Becker, Natan Padoin, Henry França Meier, Cíntia Soares
Presenter: Vivien Rossbach
Ultrasonic waves applied in CFB risers can improve gas-solids mixture in the radial direction, which is necessary to improve phase contact in chemical processes. CFD models are widely used to represent gas-solid flows in CFB risers and the acoustic field generated in the gas flow can be obtained using the LES approach. In this study, k-ε and Reynolds stress (RSM) turbulence models, Gidaspow and EMMS drag models were used to describe the gas-solid flow in a lab-scale CFB riser subject to an acoustic field with a frequency of 40 kHz and an input power of 10 W. The acoustic field was obtained for the gas flow at a velocity of 8.3 m/s without particles using LES and RANS approaches. RSM and k-ε models combined with the EMMS model have a good agreement with the experimental data of solid velocity and volume fraction. The k-ε/EMMS model was chosen because of its lower computational cost. The pressure profiles in front of the transducers in the stagnant medium are different using k-ε and LES models and it explains the pressure drop with the k-ε model higher than in experiments. The results show that the solids flow impact the acoustic field and the RANS approach can be used to represent the gas-solid flow subject to an acoustic field.
circulating fluidized bed (CFB), Acoustic field, Computational fluid dynamics (CFD), gas-solid dispersion