PurposeThe main purpose of this paper is to derive a set of similarity principles for discrete element modelling so that a numerical model can exactly reproduce the physical phenomenon concerned.Design/methodology/approachThe objective is achieved by introducing the concepts of particle “strain” and “stress” so that some equivalence between the physical system and the numerical model can be established.FindingsThree similarity principles, namely geometric, mechanical and dynamic, under which the numerical model can exactly reproduce the mechanical behaviour of a physical model are proposed. In particular, the concept of the scale invariant interaction law is further introduced. The scalability of a number of most commonly used interaction laws in the discrete element modelling is examined.Research limitations/implicationsThis is a preliminary research for a very important and challenging topic. More research, particularly in the understanding of the convergent properties of discrete element models, is needed.Originality/valueThe paper provides some important theoretical guidances to computational modelling of particle systems using discrete element techniques.
Extraction of juice from shredded sugar cane is commonly performed using sets of counter-rotating rolls. Increases in crushing rate through factory mills have traditionally been achieved by increasing blanket thickness rather than roll surface speed due to concerns regarding loss of extraction efficiency at higher rolling speeds. Recent factory experience has shown that good extraction performance can be achieved at higher speeds than previously thought, provided that adequate drainage of expressed juice away from the rolls is provided. This study uses finite element methods to predict internal energy dissipation levels due to solid matrix deformation and liquid flow during rolling of prepared sugarcane, and to compare milling parameters for thick blanket, low speed rolling versus thin blanket, high speed rolling. The finite element results suggest that higher roll speeds and thinner blankets (than those currently used in industry practice) would maintain crushing rates and juice extraction levels while reducing roll load, torque, and power consumption, and decreasing frictional sliding between rolls and cane blanket.
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