(i)    Experimental:

• A transparent experimental setup with adjustable geometry (Fig. left)
• High-speed pressure measurements
• High-speed video camera

(ii)    Modelling and simulation

• DPM (Coupling of Computational Fluid Dynamics and Discrete Element Method, Fig. right)

The bed behaviour was characterized experimentally by means of high speed recordings and the Fast-Fourier-Transformation of the measured pressure drop time series. A regime map was constructed, where the location of the domain of the dense spouting and the transition lines between other regimes can be obtained. Investigations on the effect of the shape of the central profile, the angle of the prismatic apparatus region and draft plates on the flow stability were performed.

DPM-simulations were performed at the gas flow rate corresponding to the spouting initiation, to the upper end of the spouting domain and to the instable region. The simulations predict well the expansion of the particle bed, the particle flow patterns and characteristic pressure drop fluctuations of all studied regimes. Single sharp peaks in the FFT power plots, characteristic to the stable dense spouting, were obtained, with a good agreement in the frequency of the pressure fluctuations. The irregular pressure behavior resulting in many additional peaks in FFT plots were also predicted accurately by the DPM model. The comparison of chaotic properties obtained with Deterministic Chaos Theory showed also a good agreement with experiments. The identified flow mechanisms governing the spouting termination are the growing spout instability by alternating spout deflections and incoherence.

The obtained results were condensed in an optimized geometry design, providing the significant improved spouting stability.