Chapter 4
Modelling Dynamically Structured
Fluidisation
In this chapter, the structured flow is simulated using both a Lagrangian and Eulerian approach for the solid phase. The discrete model presents a flow pattern of
bubbles in quantitative agreement with experimentally witnessed flows. The distinctive features, such as shifting nucleation sites of bubbles and interphase coupling, are
shown induced by the sharp changes of solid stress, which are created by alternating
granules between fluid-like and solid-like states. These numerical results, thus, reveal
the essential role of solid friction in reproducing and stabilising the structured flows.
As a proof of concept, the structured flow is also applied to evaluate a Eulerian approach, such as two-fluid models, working as a rigorous validation tool. The
model predicts the bubbling properties but fails to capture the correct appearance
and physics of the structured flows, under any of its typical implementations of
closures. The discrepancy suggests the absence of a proper closure to bridge the
rapid, dilute flow regime and the slow, quasi-static flow regime. This underscores
the value in investigating pulsation-induced patterns as a prime manifestation of the
physics underpinning fluidisation and highlights the direction for improving current
practices.
The chapter is adapted from the published articles:
Wu, K., de Martín, L., Mazzei, L. & Coppens, M.-O. (2016). Pattern formation in
fluidised beds as a tool for model validation: a two-fluid model based study. Powder
Technology, 295, 35–42.
Wu, K., de Martín, L., & Coppens, M.-O. (2017). Pattern formation in pulsed gassolid fluidised beds—The role of granular solid mechanics. Chemical Engineering
Journal, 329, 4–14.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
K. Wu, Dynamically Structured Flow in Pulsed Fluidised Beds, Springer Theses,
https://doi.org/10.1007/978-3-030-68752-6_4
89
Modelling Dynamically Structured
Fluidisation
In this chapter, the structured flow is simulated using both a Lagrangian and Eulerian approach for the solid phase. The discrete model presents a flow pattern of
bubbles in quantitative agreement with experimentally witnessed flows. The distinctive features, such as shifting nucleation sites of bubbles and interphase coupling, are
shown induced by the sharp changes of solid stress, which are created by alternating
granules between fluid-like and solid-like states. These numerical results, thus, reveal
the essential role of solid friction in reproducing and stabilising the structured flows.
As a proof of concept, the structured flow is also applied to evaluate a Eulerian approach, such as two-fluid models, working as a rigorous validation tool. The
model predicts the bubbling properties but fails to capture the correct appearance
and physics of the structured flows, under any of its typical implementations of
closures. The discrepancy suggests the absence of a proper closure to bridge the
rapid, dilute flow regime and the slow, quasi-static flow regime. This underscores
the value in investigating pulsation-induced patterns as a prime manifestation of the
physics underpinning fluidisation and highlights the direction for improving current
practices.
The chapter is adapted from the published articles:
Wu, K., de Martín, L., Mazzei, L. & Coppens, M.-O. (2016). Pattern formation in
fluidised beds as a tool for model validation: a two-fluid model based study. Powder
Technology, 295, 35–42.
Wu, K., de Martín, L., & Coppens, M.-O. (2017). Pattern formation in pulsed gassolid fluidised beds—The role of granular solid mechanics. Chemical Engineering
Journal, 329, 4–14.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
K. Wu, Dynamically Structured Flow in Pulsed Fluidised Beds, Springer Theses,
https://doi.org/10.1007/978-3-030-68752-6_4
89