Frictionless conveying of frictional materials
Following a brief review of the technology and previous analyses of vibratory conveying of granular materials, a general solution is derived for a well-known rigid-slab model of slide-conveying in open and closed conduits, with Coulomb friction at the walls. The solution is applied to periodic rectangular-wave and sinusoidal forcing, and it is shown that the rectangular-wave forcing admits ideal cycles in which the kinematically optimal transport is also thermodynamically optimal, in the sense that no energy is dissipated by sliding friction.
Experimental study on the vibrational transport of bulk solids
Abstract The sliding regime in vibrational transport was investigated on a laboratory-scale vibrating conveyor driven by a pneumatic ball vibrator. It was found in the literature dealing with the theoretical basis that the Blekhman and Dzhanelydze diagram is suitable for presenting visually the systematic sliding regimes and for identifying the operating conditions which occur in practice, depending on the parameters of the vibrating device (α — inclination angle, β — azimuth angle of excitation) and on the friction coefficient (f o ) of the material transported. Experiments were carried out using different sorts of model materials and the delivery speed values were measured and compared with the formula derived from theory. The accuracy of this formula is found to be good in practice. Nevertheless, an improvement of the calculation seems to be necessary in order to take into account some other parameters of the materials and technology that can influence the transport. According to the results of the dynamic and transport test of the conveyor driven by pneumatic ball vibrator, the delivery (mass flow) can be controlled easily in the range below resonance, and continuous operation of plant equipment used in the processing of granular materials (drying, granulation, cooling, etc.) can be based on this principle.
Efficient computer simulation of moving granular particles
Abstract A two-dimensional model for computing contacts and motions of granular particles of different shapes, sizes and material properties is presented. The primary aim of this model is to achieve a high degree of computational efficiency, to allow simulations to be performed very rapidly on a modest sequential machine. The important features of the model are (i) a polar representation of particle shape, (ii) a simple algorithm for contact detection, (iii) a binary collision model using momentum exchange as the describing feature, (iv) energetic coefficients of restitution selected pseudo-randomly, (v) a Coulomb friction approximation to describe slip at impact, and (vi) an optimized move-update algorithm. Results in satisfactory agreement with analytical solutions and existing, less efficient computer simulations are presented.