Consolidated flow concepts

Several consolidated flow concepts (CFCs) of advanced reprocessing have been proposed. The overall goal of a CFC could be attained by a combination of the performance of constituent elemental processes of the CFC. Technologically, it seems inappropriate to discuss the proposed CFCs in detail, because the elemental separation technologies are still evolving and immature, and some may be replaced by others in some cases. Three CFCs are, therefore, briefly explained here for comparison. 

The pile of solid particles concept is useful for either consolidated or unconsolidated media as a basis for analyzing the flow process, because many consolidated media are actually made up of individual particles that... 

It is convenient to introduce the concepts of material flow function, FF, and flow factor, ff. The material flow function, FF, relates the unconfined yield stress, To, to the corresponding major consolidating stress, cri, and is determined experimentally from the yield locus of the material, as shown in Fig. 8.9. The material flow function is presented as a plot of To versus flow factor, ff, is defined by... 

The bathtub effect occurs, in part, because most wastes have much higher hydraulic conductivities than the natural material into which they are placed they may also have very different unsaturated soil—moisture characteristics. The hydraulic conductivity of some wastes can be reduced by compaction. The bathtub effect also occurs because more infiltration enters the disposal excavation than would under normal undisturbed conditions. Trench covers may be constructed to achieve the desired hydraulic conductivity and to limit infiltration for the required period of containment or until compaction of the wastes occurs however, it is difficult to maintain the trench covers. The covers must withstand attack by plants, weather (freeze—thaw, wet—dry), erosion, and strains caused by consolidation within the trench. Most trench covers are not capable of meeting these demanding requirements without costly long-term maintenance programs. The cover should be designed to allow for expected consolidation and to utilize hydro-geological concepts of saturated and unsaturated flow systems present at the site. 

The dimensional and mechanical stability of materials is of paramount importance to their use in the everyday world where they may encounter a wide variation in temperature through design or by accident. Many polymers are processed at elevated temperatures so as to enable them to flow and be more amenable to fabrication. Food items are cooked, pasteurised or otherwise heated or frozen. Ceramics are fired so as to consolidate their final structure. The relationship between a material s dimensional and mechanical properties and its temperature is studied by the techniques described within this chapter and, due to common concepts, the effect of heat on the electrical properties of materials is also considered. 

Since the basic concept behind the creation of high performance fibres is the exploitation of molecular alignment, the term self-reinforcement has also often been used to describe the creation of polymer structures with mechanical properties that are superior to those of the isotropic polymer, for example achieved by rapid extension of melts [11] or by flow-induced crystallisation [12-14]. These and the multitude of other routes to the orientation of polymers in a solid state, and thus increased mechanical properties [15-18], are no less valid, but are not the focus of this review and will not be further described here. This review will focus on the combination of fibrous or tape-like reinforcements and the technology used to consolidate these in thermoplastic matrices to create fibre-reinforced composites. 

The well-known failure hypotheses of Tresca, Coulomb-Mohr and the yield locus concept of Jenike [1] and Schwedes [2] as well as the Warren-Spring-Equations [3 to 7] were specified from Molerus [8, 9] by the cohesive steady-state flow criterion. The consolidation and non-rapid, frictional flow of fine and cohesive particulate solids was explained by acting adhesion forces in particle contacts [8]. 

There are various conceptual ways of describing a porous medium. One concept is a continuous solid with holes in it. Such a medium is referred to as consolidated, and the holes may be unconnected (impermeable) or connected (permeable). Another concept is a collection of solid particles in a packed bed, where the fluid can pass through the voids between the particles, which is referred to as unconsolidated. Both of these concepts have been used as the basis for developing the equations which describe fluid flow behaviour. ... 

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