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5 The Role of Solid Mechanics in Stabilising Structured Flows
pulsed by gas at low frequencies, gas-driven bubble patterns emerge in an environment corresponding to dense frictional granular flow, thus introducing different
underlying physics. In relation to modelling practices, it has become clear that a
correct representation of local solid stresses, especially the frictional contribution
that serves to bridge the kinetic regime and the plastic regime, is essential to capture
gas-driven patterns in dynamic pulsed fluidised beds.
5.6 Conclusions
In conclusion, the Eulerian-Lagrangian approach is able to successfully represent
the physics underlying pattern formation in quasi-2D, pulsed, gas-solid fluidised
beds. The comparison studies reveal that solid mechanics are necessary to capture
sustained, structured bubble patterns. Spatiotemporal patterns emerge during a
dynamic transition between solid-like and fluid-like behaviour. The deficiency of
the classic Eulerian-Eulerian approach in describing dense frictional flow leads
to particular challenges when simulating pattern formation. So far, it is unclear
how more advanced formulations would perform, but such a dynamic transitional
flow provides an excellent benchmark to validate and develop better closures and
continuum models. A rheological formulation capable of capturing characteristic
features of a dynamic bubble pattern, such as its appearance, bubble size, and wavelength, should be able to reproduce transitions between dilute and dense, quasi-static
flows.
Besides, the computational results also reveal the potential of dynamically structured flows to design a new category of gas-solid reactors sitting between fixed
beds and vigorously fluidised beds. With periodically transitioning across different
flow regimes, the particulate phase grows microstructures that impede interference
of neighbouring bubbles and compartmentalise the domain into a series of identical
reactors. In each unit, solid mixing and movement profiles are tightly associated with
size and pitch of bubbles, and fully controllable via modulating the oscillatory flow
rate. Considering similar solid mixing profiles and uniform interphase contact time,
one should also expect to attain control over transport processes when operating with
highly structured flows.
5 The Role of Solid Mechanics in Stabilising Structured Flows
pulsed by gas at low frequencies, gas-driven bubble patterns emerge in an environment corresponding to dense frictional granular flow, thus introducing different
underlying physics. In relation to modelling practices, it has become clear that a
correct representation of local solid stresses, especially the frictional contribution
that serves to bridge the kinetic regime and the plastic regime, is essential to capture
gas-driven patterns in dynamic pulsed fluidised beds.
5.6 Conclusions
In conclusion, the Eulerian-Lagrangian approach is able to successfully represent
the physics underlying pattern formation in quasi-2D, pulsed, gas-solid fluidised
beds. The comparison studies reveal that solid mechanics are necessary to capture
sustained, structured bubble patterns. Spatiotemporal patterns emerge during a
dynamic transition between solid-like and fluid-like behaviour. The deficiency of
the classic Eulerian-Eulerian approach in describing dense frictional flow leads
to particular challenges when simulating pattern formation. So far, it is unclear
how more advanced formulations would perform, but such a dynamic transitional
flow provides an excellent benchmark to validate and develop better closures and
continuum models. A rheological formulation capable of capturing characteristic
features of a dynamic bubble pattern, such as its appearance, bubble size, and wavelength, should be able to reproduce transitions between dilute and dense, quasi-static
flows.
Besides, the computational results also reveal the potential of dynamically structured flows to design a new category of gas-solid reactors sitting between fixed
beds and vigorously fluidised beds. With periodically transitioning across different
flow regimes, the particulate phase grows microstructures that impede interference
of neighbouring bubbles and compartmentalise the domain into a series of identical
reactors. In each unit, solid mixing and movement profiles are tightly associated with
size and pitch of bubbles, and fully controllable via modulating the oscillatory flow
rate. Considering similar solid mixing profiles and uniform interphase contact time,
one should also expect to attain control over transport processes when operating with
highly structured flows.