BITS Faculty Publications

Permanent URI for this communityhttp://localhost:4000/handle/123456789/1867

Browse

Has files: NoSubject: search.filters.subject.CFD simulation

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Reinterpretation of the Geldart A powder classification based on Eulerian–Eulerian CFD simulation
    (De Gruyter, 2022-07) Sande, Priya Christina
    Geldart classified powders into four categories and assigned each category its own unique characteristic. Geldart A particles, being easily aeratable, show a unique feature of ‘Homogenous expansion’ before bubbling. In this work, an additional feature for the Geldart chart is proposed which adds significant utility for the processing of Geldart A particles. CFD was used to characterize the entire Geldart A region of the Geldart chart based on detailed fluidization behavior. For this, Eulerian–Eulerian Two-fluid model (TFM) simulations were conducted for 25 particle systems across the entire span of the Geldart A region. The simulations (Solid volume fraction (SVF) contours) of bed evolution, taken before the appearance of multiple bubbles, were analyzed in detail. The particle systems were then sub-categorized into Red (5% average bed expansion), Orange (12.5% average bed expansion), and Green (30% average bed expansion) sub-types. The sub-types were plotted on Geldart chart, and for the first time a continuum heat map was generated, from which the ‘level of fluidizability’ of all Geldart A powders can be conveniently gaged. The map can be used for a more informed choice of powder for various industrial applications. Also, the A/B boundary proposed by Verloop was found to be a better fit for our proposed continuum when compared to the original Geldart A/B boundary. The 2D Simulation results performed in this work, found adequate validation against experimental findings in literature. Further, fine mesh 2D simulation results compared well with 3D simulations for dense bed, and were thereby deemed adequate for revealing dense bed behavior before onset of multiple bubbles.
  • No Thumbnail Available
    Item
    Mesh size effect on CFD simulation of gas-fluidized Geldart A particles
    (Elsiever, 2014) Sande, Priya C; Ray, Saumi
    We investigate the effect of mesh size on CFD simulations of a lab-scale sized fluidized bed of Geldart A particles using two-fluid model (TFM), specifically for homogeneous expansion and transition to bubbling. For the first time we have shown a set of lab-scale domain size fine mesh simulations. In this context transient bed voidage profiles have been analyzed in detail. TFM follows the Eulerian–Eulerian approach which has the advantage of being less computationally expensive than Eulerian–Lagrangian approach for an engineering scale. Mesh size has a drastic effect on minimum bubbling velocity. With mesh refining, the observed minimum bubbling velocity approaches its experimental value. On reducing mesh size even up to 1 mm × 1 mm, there was no improvement in capturing homogeneous expansion. Fine mesh simulation revealed void structures and could predict the bubbling transition, though the homogeneous expansion captured was not as much as experimentally observed. Review of several simulations across all the mesh sizes studied, revealed the presence of persisting dilute regions getting triggered around experimental minimum bubbling velocity. Theses persisting dilute regions seem to signal the presence of the bubbling regime. The effect of commonly used drag laws was also studied and it was found that the Gidaspow and Syamlal O'Brien drag laws manifested the dilute region markers at 8 mm/s while for the Wen Yu drag law this value was 10 mm/s. The effect of frictional stress and wall boundary condition for both phases was qualitatively assessed. Omitting frictional stress or changing no-slip to free-slip boundary condition for gas phase had the effect of delaying minimum bubbling velocity.