Particle shape and residence time of granular materials in a rotating tilted cylinder

The residence time of particles in a rotating tilted cylinder was investigated experimentally for various particle shapes and concentrations. In the single particle movement, the residence time relates to to tan ω0, where ω0 is the average angle in a horizontal cylinder up to which the particle is lifted by the rotation of the cylinder. The motion of the single particle is modeled and an investigation is made into the effect of the particle concentration on the residence time. The residence time can be expressed in terms of tan ω0 and the rotational frequency of the cylinder. The boundary between the uniform acceleration motion and the uniform velocity motion is found to exist at tan ω0 ≃ 0.25. A similar boundary also exists in the case of multiparticle flows. The residence time of particles increases exponentially with respect to the particle hold-up or the average area fraction of particles in the multi-particle flow. Particles with larger contact area on the cylinder wall seem insensitive to the interaction among themselves.