Convection in highly fluidized three-dimensional granular beds.
Free, buoyancy-driven convection has been observed experimentally in three-dimensional highly fluidized granular flows for the first time. Positron emission particle tracking was used to determine the position of a tracer grain in a vibrofluidized bed, from which packing fraction distributions as well as the velocity fields could be determined. The convection rolls, although small compared to the magnitude of velocity fluctuations (<5%), were consistently observed for a range of grain numbers and shaker amplitudes. Density variations are a signature of free convection and, with negative temperature gradients also present, were interpreted as the mechanism by which the convection rolls were initiated.
Wildman
R D
RD
Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leics. LE11 3TU, United Kingdom.
Huntley
J M
JM
Parker
D J
DJ