GRAIN-FLUID INTERACTION IN COUETTE FLOW

Abstract

This paper is a continuation of the papers of Bakker & Van Kesteren (1986) and Bakker et al. (1988). In this paper the results are presented of ring shear tests on mixture of oil and spheres with the same density (880 kg/m3). In order to study in detail the behaviour of a sand water mixture at high concentrations in a Couette like shearflow in the viscous regime the graindiameter and viscosity are enlarged by a factor 100: respectively 15 mm and 10-4 mJ/s. The test are executed in the so called grain carrousel with shear rates up to 75 s-1 (Bagnoldnumber N=240). The experimental set up is such that only constant volume test could be performed. The test results indicate that at concentration below 30% (vol.) no dispersive stresses are generated. At higher concentrations the generated dispersive stresses increases with concentration and shearrate. From videofilms it was observed that the grains are moving in layers with only small mutual exchange (grainswop).