01465nas a2200169 4500008004100000022001400041245007800055210006900133260007900202300001100281490000700292520083600299100001601135700001801151700002101169856010501190 2014 eng d a1539-375500aSpontaneous jamming and unjamming in a hopper with multiple exit orifices0 aSpontaneous jamming and unjamming in a hopper with multiple exit aONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USAbAMER PHYSICAL SOCcAUG a0202010 v903 a

We show that the flow of granular material inside a two-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For hoppers with small orifice widths, intermittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e., avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the interorifice distance. The unjamming is driven primarily by fluctuations alone when the interorifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow to unjam.

1 aKunte, Amit1 aDoshi, Pankaj1 aOrpe, Ashish, V. uhttps://library.ncl.res.in/content/spontaneous-jamming-and-unjamming-hopper-multiple-exit-orifices-001322nas a2200181 4500008004100000022001400041245006400055210006200119260007900181300001100260490000700271520067500278100002600953700002500979700002301004700001801027856009501045 2015 eng d a1539-375500aSelf-similar rupture of thin free films of power-law fluids0 aSelfsimilar rupture of thin free films of powerlaw fluids aONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USAbAMER PHYSICAL SOCcAUG a0230140 v923 a

The rupture of a thin free film of a power-law fluid under the competing influences of destabilizing van der Waals pressure and stabilizing surface tension pressure is analyzed. In such a fluid, viscosity decreases with the deformation rate raised to the n - 1 power where 0 < n <= 1 (n = 1 for a Newtonian fluid). When 6/7 < n <= 1, film rupture occurs under a balance between van der Waals pressure, inertial stress, and viscous stress. When n < 6/7, however, the dominant balance changes: Viscous stress becomes negligible and the film ruptures under the competition between van der Waals pressure, inertial stress, and surface tension pressure.

1 aThete, Sumeet, Suresh1 aAnthony, Christopher1 aBasaran, Osman, A.1 aDoshi, Pankaj uhttps://library.ncl.res.in/content/self-similar-rupture-thin-free-films-power-law-fluids-102064nas a2200169 4500008004100000022001400041245006900055210006900124260000800193300001100201490000700212520151400219100002601733700002101759700001801780856009601798 2018 eng d a1070-663100aSpreading dynamics of superposed liquid drops on a spinning disk0 aSpreading dynamics of superposed liquid drops on a spinning disk cJAN a0121100 v303 a

We have experimentally studied simultaneous spreading of superposed drops of two Newtonian liquids on top of a horizontal spinning disk using the flow visualization technique. An inner drop of high surface tension liquid is placed centrally on the disk followed by a drop of outer liquid (lower surface tension) placed exactly above that. The disk is then rotated at a desired speed for a range of volume ratios of two liquids. Such an arrangement of two superposed liquid drops does not affect the spreading behavior of the outer liquid but influences that of the inner liquid significantly. The drop spreads to a larger extent and breaks into more fingers (Nf) as compared to the case where the same liquid is spreading in the absence of outer liquid. The experimentally observed number of fingers is compared with the prediction using available theory for single liquid. It is found that the theory over-predicts the value of Nf for the inner liquid while it is covered by an outer liquid. We provide a theoretical justification for this observation using linear stability analysis. Our analysis demonstrates that for small but finite surface tension ratio of the two liquids, the presence of the outer interface reduces the value of the most unstable wave number which is equivalent to the decrease in the number of fingers observed experimentally. Finally, sustained rotation of the disk leads to the formation of droplets at the tip of the fingers traveling outwards. Published by AIP Publishing.

1 aSahoo, Subhadarshinee1 aOrpe, Ashish, V.1 aDoshi, Pankaj uhttps://library.ncl.res.in/content/spreading-dynamics-superposed-liquid-drops-spinning-disk