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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : The influence of particle density and fluid viscosity on the rheological behaviour of dense granular...
The influence of particle density and fluid viscosity on the rheological behaviour of dense granularfluid involved in flow phenomena
Author : ANNA MARIA PELLEGRINO(1) & LEONARDO SCHIPPA(1)
ABSTRACT
Suspensions of solid particles are commonly encountered in natural flows. Typical examples include soil avalanches,
rock-falls, debris flows and torrential process, which cause disasters and catastrophes. A laboratory activity on high
concentrated granular-fluid mixtures was carried out in order to study the flow behavior of natural materials involved in
fast-moving phenomena. We transferred the approach using for dry granular media (i.e., a frictional rheology) to wet
suspensions, using different combinations of granulars and viscous fluid sheared with two pressure-imposed
rheometers. The shear stress as a function of the shear rate at imposed values of the normal stress was measured for
granular-fluid mixtures with particles denser than interstitial fluid in order to investigate how the particles weight (i.e., the
sedimentation) affects the experimental results. The suspensions considered exhibit a viscoplastic behavior similarly to
granular media and they are fully characterized by the evolution of the friction coefficient and the volume fraction
with a dimensionless viscous number Iv. In particular, we have different -Iv curves each one associated to a different
value of the pressure imposed. The effects of the gravity seems more relevant in case of low value of vertical pressure
imposed. Indeed, when the imposed normal stress is reduced, the relative density play a relevant role. Moreover, also
the interstitial fluid viscosity affects the results, influencing the value of the static friction coefficient 1 (i.e., =1 at Iv0)
and the value of the maximum concentration of the mixture during the shearing m (i.e., = m at Iv0).
File Size : 749,716 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 13/08/2015
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