Liquid, elastic

Lodge, A. S., 1964. Elastic Liquids, Academic Press, London. 

Lodge AS (1964) Elastic liquids. Academic Press, New York... 

In summary, we have commented briefly on the microscopic applications of NMR velocity imaging in complex polymer flows in complex geometries, where these applications have been termed Rheo-NMR [23]. As some of these complex geometries can be easily established in small scales, NMR velocimetry and visc-ometry at microscopic resolution can provide an effective means to image the entire Eulerian velocity field experimentally and to measure extensional properties in elastic liquids non-invasively. 

Measurements suggest that the pressure loss for laminar flow of power law fluids through a sudden contraction is not significantly different from that for Newtonian flow [Skelland (1967)]. This statement applies to inelastic power law fluids in the case of elastic liquids, very high contraction pressure losses occur as discussed in Section 3.10. 

In the case of highly elastic liquids mixed by a Rushton turbine, flow reversal may occur in the low Reynolds number region, ReM< 30, leading to values of the power number as much as 60 per cent higher than for inelastic liquids. In the intermediate region, 50 1000, the power... 

Mixing of elastic liquids is very strongly dependent on the type of mixer and the tank geometry, as well as the rheological properties of the liquid so that at a particular value of ReM the power drawn may be lower or higher than that for a Newtonian liquid. 

Constitutive equations for the Rouse and Zimm models have been derived, and are found to be expressible in the form of Lodge s elastic liquid equation [Eq.(6.15)], with memory function given by (101) ... 

Lodge,A.S. Elastic liquids. New York Academic Press 1964. 

Tanner,R.I., Simmons,J.M. Combined simple and sinusoidal shearing in elastic liquids. Chem. Eng. Sci. 22,1803-1815 (1967). 

A sharp decrease in wall friction in the flow of visco-elastic liquids (including chemically reactive liquids) leads to the formation of low pressure zones. The gas flows into these zones, which leads to disruption of the liquid stream in nozzle 5. Additional gas blown into the disrupted liquid stream through the ring gaps by pipelines 11 and 15 causes separation of the liquid into smaller droplets, thus improving spray dispersion. 

It was established experimentally that a jet-type of flow appears when the characteristic size of the stream is less than the minimal gap between the walls of the mold.277 This proves that the cause is related to the ratio between the size of the injection nozzle and the coefficient of swelling of the elastic liquid moving inside the mold rather than to the axial momentum of the moving liquid. This conclusion is also supported by evidence that highly filled polymers, which are less elastic than pure melts, form jet-like patterns at lower flow speeds. 

The viscoelastic properties are highly temperature-dependent so that the maximum temperature should be always specified and taken into account. Polymers at room temperature behave by different ways i.e. hard solids, elastic liquids, rubbers, etc [1,7]. 

Figure 6.16 The centrifugal effect in a non-elastic liquid (a), and the Weissenberg effect in in a viscoelastic liquid (b).

Viscolelastic materials can be divided into viscoelastic solids and viscoelastic, or simply elastic, liquids. All viscoelastic liquids are non-Newtonian, but not all non-Newtonian liquids are viscoelastic. Non-Newtonian liquids show nonlinear rheological behavior, and this may be time dependent (Barnes et al., 1989). 

Elastic liquids of relatively low viscosity these liquids have to be confined in the measuring devices in order to prevent flow under the action of gravitational forces. 

The limiting value of the creep is equal to 00 = a0/E = Voigt-Kelvin element is only able to describe qualitatively the creep behaviour of rubberlike materials with a limited creep and not the creep of an elastic liquid. In general the creep compliance may be expressed as... 

For mobile liquids, the use of this kind of controllable instruments is practically impossible. For these liquids, the non-controllable measurement techniques are available only and in general an apparent transient viscosity will be obtained. Nevertheless these measurements are still of great value, because in many cases they approximate industrial process conditions. Mostly used is the spinning line rheometer, where an elastic liquid is pressed through a spinneret and the liquid is pulled from the die by winding the filament around a rotating drum or by sucking the tread into a capillary tube. This is schematically shown in Fig. 15.25. A serious problem is the translation of the obtained data to the extensional viscosity. Many other non-controllable devices are discussed by,... 

Newtonian liquid visoo-elastic liquid (creeping) solid... 

As with solid-gas systems, food analysis is one of the widest fields of application of US-based detection since typical foods such as ice cream or whipped cream consist of air bubbles distributed in a visco-elastic liquid [137]. 

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