Axial band scaling for bidisperse mixtures in granular tumblers.
نویسندگان
چکیده
Axial banding in rotating tumblers has been experimentally observed, but the dependence of band formation on the relative concentration of the bidisperse particles has not been thoroughly examined. We consider axial band formation and coarsening for dry and liquid granular systems of bidisperse mixtures of glass beads where the small particle volume fraction ranges from 10% to 90% in half-filled tumblers for several rotation rates. Single bands form for small particle volume fractions as low as 10% and as high as 90%, usually near the end walls. Band formation along the entire length of the tumbler is less likely at very low or very high volume fractions. After many rotations the segregation pattern coarsens, and for small particle volume fractions of 50% and greater, the coarsening is logarithmic. For very low or very high small particle volume fractions, the rate of coarsening is either not logarithmic or coarsening does not occur within the duration of the experiment (600 rotations). When bands form, the width of the band for either the small or large particles scales with the tumbler diameter.
منابع مشابه
Granular coarsening: phase space and evolution analogies.
Various aspects of axial banding of size-varying bidisperse granular mixtures in cylindrical tumblers have been documented repeatedly over a decade or so, but the dependence of surface band formation on the relative concentration of particles and rotation rate has not been thoroughly examined. Coarsening patterns analogous to nucleation and spinodal decomposition occur as the relative concentra...
متن کاملOnset mechanism for granular axial band formation in rotating tumblers.
The mechanism for band formation of a granular mixture in long rotating tumblers is unresolved 70 years after the phenomenon was first observed. We explore the onset mechanism for axial segregation of a bidisperse mixture of particles of different sizes using the discrete element method. End walls initiate axial band formation via an axial flow due to friction at the end walls. The nonuniform d...
متن کاملInversion of band patterns in spherical tumblers.
Bidisperse granular mixtures in spherical tumblers segregate into three bands: one at each pole and one at the equator. For low fill levels, large particles are at the equator; for high fill levels, the opposite occurs. Segregation is robust, though the transition depends on fill level, particle size, and rotational speed. Discrete element method simulations reproduce surface patterns and revea...
متن کاملSurface roughness effects in granular matter: influence on angle of repose and the absence of segregation.
We investigate the effect of nanoscale variations in the surface roughness of individual particles on macroscale granular flow characteristics. Experiments were conducted in circular rotating tumblers with smooth and rough 2 and 3 mm steel particles. The smooth beads had a rms surface roughness of approximately 30 to 60 nm; rough beads had a surface roughness of approximately 240 to 350 nm. The...
متن کاملGranular axial band formation in rotating tumblers: a discrete element method study
The onset mechanism for band formation of a granular mixture in long rotating tumblers is still largely unresolved. We study this issue for axial segregation of binary mixtures having different size particles, using discrete element method simulations. Endwalls initiate axial segregation via an axial flow due to friction. The non-uniform distribution of axial velocity in the flow together with ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Physical review. E, Statistical, nonlinear, and soft matter physics
دوره 78 3 Pt 1 شماره
صفحات -
تاریخ انتشار 2008