Vutukuri, Hanumantha Rao

etd@IISc Electronic Theses and Dissertations at Indian Institute of Science

Abstract Granular materials are large collect~on of dlscrete particles havlng vanety of slzes and shapes However, even when the mterachons between the granular materlal at the rmcroscoplc level are slmple, such as hard sphere lnelastlc colhslons, the collective behav~or 1s complex and lnterestlng phenomena are observed at the macroscopic scale The present work is concerned wlth the study the macroscopic properties of gravlty- dnven and sheared granular flows in rapld flow reglme uslng event-dnven hard dlsk molecular dynamlc slmulaUons In the present study, the granular matter has been modelled as rough and lnelastlc hard disks The event-dnven s~mulahon has been developed for the gravlty-dnven flow through vert~cal channels and Couette flows In vert~cal chute flows, the veloclty profiles obtaned from the slmulat~ons confirm the existence of shear layers near the walls In the hlgh dens~ty l ~ m t  The vanatlon of shear layer thlckness wlth channel wldth, roughness of the wall, partlcle roughness, coefficlent of restltutlon, acceleratlon due to gravlty and area fractlon has been stud- led The thlckness of the shear zones that are created at the walls was found to be Independent of the wldth of the channel(Pou11quen and Gutframd, 1996), and equal to approximately 6 partlcle diameters It has been observed that the shear layer tkckness Increases wlth the wall roughness parameter(Natarajan et a1 , 1995) The mean veloc- ~ t y  decreases wlth lncreaslng area fractlon It 1s found that the shear layer thlckness 1s Independent of the partlcle roughness parameter, normal coefficlent of restltuhon of the part~cle and acceleratlon due to gravlty for the glven condltlons The effect of the solid fractlon on the shear layer thlckness, stress, mean velociues and granular temperature has been studled At k g h  densltles a plug flow type mean veloclty pro- files and at low denslues parabolic profiles are observed Equlpart~t~on of energy has been found not to be valld for these cases The asymmetry of the angular veloclty profile along the wldth of channel 1s obtaned and the simulat~on results are found to be In good agreement wlth vortlclty expression except near the walls The anlsotroplc behavlor of the granular temperature IS obtaned and granular temperature m stream wlse direcuon 1s h ~ g h  compared to the crosswlse direction It has been found that the area frachon IS low near the walls where the granular temperature 1s hlgh The non- Gausslan dlstnbutlon of fluctuabng veloc~tles in stream wlse and crosswlse dlrect~ons has been observed The total shear stress profile IS llnear and total normal stress m cross-stream direction IS constant along the wldth of the channel Quahtaave agree- ment 1s found for the total cross-stream normal stress wlth the pred~cQons of lunetlc theory model by Jenluns and Rchman (1985), but the total shear stress from the pre- d~ctions is slightly larger than the simulat~on results near the walls because of shear layers near the walls In shear dnven granular flow simulahons, the non-equipartifion of energy and anisotropic behav~or of granular temperature are observed The mean velocity profiles from sirnulabon shows slip at both the solld walls and the regions with larger shear in the wall v~cinlty Corresponding to the hlgh shear zones are reglons of low den- s ~ t y  and large granular temperature The total shear and cross-stream normal stresses obtained from the simulat~on are in agreement with theoretical predictions using the Jenluns and fichman (1985) model Bagnold (1954) consbtut~ve law was examned w ~ t h  s~mulation and shows exactly fit the simulation results w ~ t h  conshtutive relabon and the non-Gaussian distribution of fluctuatmg veloc~ties 1s observed 

Simulations Of Two Dimensional Gravity-Driven And Shear-Driven Rapid Granular Flows

http://etd.iisc.ac.in/static/etd/abstracts/1767/G19731-Abs.pdf

Simulations Of Two Dimensional Gravity-Driven And Shear-Driven Rapid Granular Flows

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etd@IISc Electronic Theses and Dissertations at Indian Institute of Science