Experimental and analytical investigations of granular-fluid mixtures down inclines

Granular-fluid mixtures flowing down an incline in the grain-inertia regime were studied experimentally and analytically. The equations of motion are based on the kinetic theory for granular flow. The boundary conditions are formulated following two methods. The first is a simple mechanical approach based on the energy exchange at the wall. The other is based on the kinetic theory for granular flow. Solutions for dry granular flow down a chute are studied in order to compare both methods. The extension of the kinetic theory presented here, includes drag forces resulting from the interstitial fluid that cushions interparticle collisions and particle-wall collisions. Frictional stresses, produced when long term contacts are present, and fluid turbulent fluctuations are introduced in the model.The results are compared with measurements from an experimental chute in which the inclination, the solids flow rate and fluid flow rate are all varied. The theory is found to give a good qualitative account of the observed behaviour. Finally an application of the model to the description of the mechanical behaviour of the Nevado del Ruiz 1985 debris flow is attempted