Time independent fluids

Abstract

Time independent or purely viscous fluids are those whose viscosity is not dependent on their duration of flow, which means that the well known thixotropic materials, such as some kinds of paints, lie outside this class. This class of fluids, however, does include the best understood sub-group, the newtonian fluids. The flow of these particular fluids is well understood but as they form only a small part of a whole gamut of flow behaviour, it is important both to industry and in everyday life that the lesser documented fluids be studied and their properties understood. Sometimes the properties of fluids are a nuisance, at other times an advantage-if there were no such thing as Bingham plastic behaviour, how could striped toothpastes exist?Before going on to describe the particular properties of the time independent fluids, it is instructive to learn what relationship they bear with respect to other types of fluids. The four groups are as follows:(1) Time independent or purely viscous fluids: (a) newtonian fluids, (b) non-newtonian fluids.( 2 ) Time dependent fluids: (a) thixotropic fluids, (b) negative thixotropic fluids.(3) Viscoelastic fluids.(4) Complex rheological fluids: these exhibit a combination of properties from at least any two of the above. It should be understood that it is far easier to invent groups of fluids than it is to fit any specific fluid into a particular group.Details of the other types of fluid may be found in some of the references given.

Acoustic Heating Produced in the Thermoviscous Flow of a Shear-Thinning Fluid

“…P is the tensor of viscous stress. In the model of a shear-thinning fluid, the viscous stress tensor relates to the shear rate in the following manner (Collyer, 1973;Wilkinson, 1960):…”

“…Time-independent fluids constitute the class of fluids characterized by the fact that their shear rate depends only on the shear stress and is a single valued function of it (Collyer, 1973;Cheremisihoff, 1988;Wilkinson, 1960). Solutions of melts of high molecular weight, particular high polymers and suspensions of solids in liquids fall into this group.…”

“…They require accurate estimations of heating during medical therapy which applies sound of different kinds including nonperiodic ones, in particular, impulses (Hartman et al, 1992;Rudenko, 2007). Not only biological, but many technical liquids belong to the shear-thinning group, such as the already mentioned dilute solutions of high polymers, printing ink, soap solution and glycerol, cellulose, acetate and napalm, paper pulp and detergent slurries, as well as many food products like mayonnaise (Collyer, 1973). Some of them are very shear-thinning fluids, for example, concentrated cement slurries, mineral suspensions, oil-well cements (Barnes, 1999;Roberts et al, 2001).…”

Generation of the vorticity mode by sound in a Bingham plastic

“…Newtonian fluids have a viscosity independent on the shear rate [1]. Fluids whose viscosity is a single valued function of the shear rate are termed non-newtonian fluids [2].…”

“…In contrast with newtonian fluids, the non-newtonian properties are caused by the viscous dissipation of energy due to collisions between large particles, or to the distortion of or collision between colloidal structures. Within this group there are three main types: Bingham plastic and plastic behavior, shear-thinning behavior and shear-thickening behavior [1][2][3][4][5]. An ideal Bingham plastic material is characterized by the fact that the shear rate is proportional to the shear stress after a finite value of shear stress has been attained [1,3].…”