XXVIII IAHR Congress, Graz, 1999 - proceedings -

Granular system rheology and mechanics: experiments


1) Dep. of Civil Engineering, University of Parma,

Viale delle Scienze, I-43100 Parma

2) DISTART, University of Bologna,

Viale Risorgimento,2, I-40136 Bologna


In the present paper we report the experimental activity carried out in a rotating drum partially filled with grains or glass beads. Experiments give information about rheology through velocity profiles and through the velocity covariance tensor structure. We used a LDV system for measuring the velocity of the grains in several points along three vertical sections. The data were elaborated in order to obtain for all the experiments the velocity and pseudotemperature profiles; for a subset of the experiences an oversized set of data were elaborated to obtain the velocity covariance. The velocity covariance is not collinear with the velocity of deformation tensor. A first attempt to justify the rotation of the tensor axes as a consequence of some free surface perturbations slowly moving upstream has not been successful. In order to better evaluate the correlation between the free surface perturbations and the mean velocity profile perturbations, we started to use a PIV technique. The application of such a technique for grain systems is still in progress. The data were even used to obtain the grain volume concentration, with good results.

Keywords: rheology of granular systems, debris flows, experiments