Rheological behaviour and runout of short-lived, fast-moving flows of hot dense suspensions

Laurence Girolami (1) , Frederic Risso (2)

1 GéHCO EA6293 - GéoHydrosystèmes COntinentaux
2 IMFT - Institut de mécanique des fluides de Toulouse

This study aims at extending the previous work of Girolami et al. [11-13] which is still suffering from a lack of reliable predictions for the description of hot, dense suspensions obtained by fluidizing with air a bed of fine solid particles, originally cohesive at room temperature, then released down a rectangular flume. Here, we first present the effective viscosities of the suspensions which increase as a power law of the particle volume fraction Φs. Thus, we show that their rheological behaviour is solely controlled by Φs and its value at packing Φpacking , whatever the material involved in the mixture. Finally, we present a new modeling of the flows runout and highlight that the flows duration is solely controlled by the settling time (i.e. the time necessary for a suspension of a given Φs to settle at a velocity U sed over a distance h exp equals to the expansion height), the initial suspension geometry a, and the key parameter Φs /Φpacking. This prediction allows to distinguish two different flow regimes, with a transition around Φs /Φpacking ≃ 0.85, which seems to be correlated to the variations of the mixture rheology.

Mots clés: Dense suspensions; rheological behaviour; particle sedi- mentation; high temperature; runout prediction; scaling laws

Domaines: Mécanique [physics]

Laurence Girolami, Frederic Risso. Rheological behaviour and runout of short-lived, fast-moving flows of hot dense suspensions. Journal of Energy Challenges and Mechanics, 2018. ⟨hal-02171790⟩