Systems Newtonian

The flow of compressible and non-compressible liquids, gases, vapors, suspensions, slurries and many other fluid systems has received sufficient study to allow definite evaluation of conditions for a variety of process situations for Newtonian fluids. For the non-Newtonian fluids, considerable data is available. However, its correlation is not as broad in application, due to the significant influence of physical and rheological properties. This presentation is limited to Newtonian systems, except where noted. 

Dodge, D.W. and Metzner, A.B., Turbulent flow of non-Newtonian systems, AIChE Journal, 5, pp. 189-204 (1959). 

Different types of liquid crystals exhibit different rheological properties [16,17]. With an increase in organization of the microstructure of the liquid crystal its consistency increases and the flow behavior becomes more viscous. The coefficient of dynamic viscosity r, although a criterion for the viscosity of ideal viscous flow behavior (Newtonian systems), is high for cubic and hexagonal liquid crystals but fairly low for lamellar ones. However, the flow characteristics are not Newtonian but plastic or pseudoplastic, respectively. 

Non-Newtonian Systems. Although the determination of the required properties is straightforward for liquids, the situation is much more complex for non-Newtonian systems such as gels, emulsions, and slurries. As indicated earlier, there is a significant effort under way to prepare slurries of solids in liquid fuels to increase the volumetric energy of such fuels. These slurries must be stabilized as gels or emulsions to prevent solid separation. It therefore seems worthwhile to discuss the preparation of such slurries as well as the techniques used to measure some of the properties required to characterize these systems. 

The distinguishing feature of non-Newtonian systems is seen to be that the colloidal rather than the molecular properties are of significance. Philippoff (P4) has summarized the properties of the colloidal particles which are relevant in determining their rheological behavior as follows ... 

The completely general case is that of a fluid for which the relationship between shear stress and rate of shear is not linear and may also depend on both the duration of the shear and the extent of the deformation produced. Thus it is possible to divide non-Newtonian systems into three broad categories ... 

It has been pointed out by Weltmann (W4) that the complexity of some non-Newtonian systems leads to unusual changes in fluid properties with temperature. This may occur, for example, if solids tend to go in or out of solution or if the solids are more completely dispersed at the higher temperature. Most non-Newtonian fluids, however, do not show such unusual effects, and the changes in fluid properties with temperature and concentration of material in suspension or solution may be summarized as follows. 

Solution of forced convection problems for flow in non-Newtonian systems. 

We have already devoted a considerable amount of space to our discussion of viscosity without ever venturing beyond Newtonian systems. At least as much —probably more —could be said about non-Newtonian systems. 

Dodge DW, Metzner AB (1959) Turbulent flow of non-Newtonian system AIChE J 5 189... 

The situation, one hundred years on, could hardly be more different. The interpretation of quantum mechanics, which came to replace the Newtonian system, is as hotly disputed as ever and the common ground with the theory of relativity remains elusive and vague. The reason for the discord must lie somewhere in the transition from the classical to the new non-classical paradigm. What is proposed here, is to retrace the steps that led to the emergence of the new theoretical models, in an attempt to identify the point of conceptual bifurcation. 

In extending the work to non-Newtonian systems, a series of water-in-oil emulsions was used. These were prepared using the following formulations ... 

The non-Newtonian systems used were carboxymethylcellulose (0.5-2.0%) and polyacrylamide (0.5-1.5%) solutions. 

Fumed silica bears the properties of an effective thickener which will not undergo swelling and exhibits chemically inertness. Additionally, thickening by fumed silica results in a non Newtonian system commonly accompanied by a yield point, shear thinning and thixotropy. Thus, fumed silica solves in an excellent manner the requirements of reversible shear thinning under high shear stress but a distinct yield point or high viscosity at lower shear stresses. 

---