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Reverse buoyancy as a consequence of cyclic fluidization

Reverse buoyancy as a consequence of cyclic fluidization. Gustavo Gutiérrez USB Oliver Pozo UNSA Leonardo Reyes USB Ricardo Paredes V. IVIC James Drake and Edward Ott UMD. y o w 2 cos w t. Intruso. SEGREGATION Brazil-nut problem. Intruder. Rosato et al, 1987. Intruso.

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Reverse buoyancy as a consequence of cyclic fluidization

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  1. Reverse buoyancy as a consequence of cyclic fluidization Gustavo Gutiérrez USB Oliver Pozo UNSA Leonardo Reyes USB Ricardo Paredes V. IVIC James Drake and Edward Ott UMD

  2. yow 2cosw t Intruso SEGREGATIONBrazil-nut problem Intruder Rosato et al, 1987

  3. Intruso SEGREGATIONReverse Buoyancy yow 2cosw t Light Heavy Shinbrot and Muzzio 1998

  4. Reverse Brazil-nut effect time Breu et al, 2003

  5. Reverse buoyancy ri  rm ri  rm yow 2cosw t yow 2cosw t

  6. Displacement of the intruder t=3.83s t=5.27s t=0.0s light heavy t=0.77s t=1.0s t=0.0s time

  7. Vertical Displacement Heavy intruder Light intruder

  8. Vertical velocity vs. density ratio

  9. F’B F’B : Buoyancy force : Weight m V’ F’W F’W F’ F’ MODEL The granular medium fluidizes in part of the cycle : Drag force (The reference frame is located on the container)

  10. Cyclic fluidization Gcoswt t/2 t Evesque, Rajchenbach and de Gennes 1998

  11. MODEL This equation is valid when the granular medium is fluidized, otherwise the medium behaves like a solid.

  12. GAP

  13. Gap for different grains subjected to vertical vibrations(Amplitud 8.5 mm y frecuency 11.7 Hz ) Black spherica seeds Model Rice Inelastic sphere Mustard seeds Glass spheres (diameter: 300 - 350mm) Sánchez et al, 2003

  14. Column of spheres Luding et al 1994

  15. Air flow Q Porous piston h k= permeability A= transversal area P= pressure s m= viscosity of air Acoswt Kroll 1954 / Reyes et al 2003

  16. ; Comparison of the model with the experimental results Heavy intruder Light intruder

  17. PREDICTION OF THE MODEL

  18. Comparison of the model with the experimental results

  19. CONCLUSION • Assuming that cyclic fluidization occurs, for a granular system subjected to vertical sinusoidal vibrations, we have formulated a simple quantitative model for reverse buoyancy. • The model gives the rising and the sinking velocity of an spherical intruder as a function of the ratio between the density of the object and that of the medium. • We obtain a very good qualitative and quantitative agreement between the theoretical model proposed and our experimental findings.

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