Viscosity Bulk dynamic

The energetics and kinetics of film formation appear to be especially important when two or more solutes are present, since now the matter of monolayer penetration or complex formation enters the picture (see Section IV-7). Schul-man and co-workers [77, 78], in particular, noted that especially stable emulsions result when the adsorbed film of surfactant material forms strong penetration complexes with a species present in the oil phase. The stabilizing effect of such mixed films may lie in their slow desorption or elevated viscosity. The dynamic effects of surfactant transport have been investigated by Shah and coworkers [22] who show the correlation between micellar lifetime and droplet size. More stable micelles are unable to rapidly transport surfactant from the bulk to the surface, and hence they support emulsions containing larger droplets. 

Effectiveness of a crude oil demulsifier is correlated with the lowering of shear viscosity and dynamic tension gradient of the oil-water interface. Using the pulsed drop technique, the interfacial dilational modulii with different demulsifiers have been measured. The interfacial tension relaxation occurs faster with an effective demulsifier. Electron spin resonance with labeled demulsifiers indicate that the demulsifiers form reverse micelle like clusters in bulk oil. The slow unclustering of the demulsifier at the interface appears to be the rate determining step in the tension relaxation process. 

In the fee lattice chain modeP the approach has been slightly different, since it has a fixed bond length. First one determines the most likely end-to-end distance of segments of two to five monomers. Then for a bulk system, one can calculate the occupancy required on the lattice to match the experimental density, and choose the monomer-to-bead ratio, which gives occupancy of 70 -90% in order to represent bulk dynamic behaviour. Finally a bond angle potential is adjusted to achieve the correct mean squared end-to-end distance. The time step can then be calibrated against diffusion or viscosity data, or from Molecular Dynamics simulations. ... 

Dynamic viscosity of the liquid carrier Shear spin viscosity Second coefficient of viscosity Bulk spin viscosity... 

The Effect of Bulk Dynamic Viscosity on Film Drainage Rate... 

Here we will not go through the detailed calculations that lead to the Enskog theory values for the transport coeflicients of shear viscosity, bulk viscosity, and thermal conductivity appearing in the Navier-Stokes hydro-dynamic equations. Instead we shall merely cite the results obtained and refer the reader to the literature for more details. One finds that the coefficient of shear viscosity 17 is given by ... 

The product / det det h s the dimensions of dynamic viscosity. The ratio of this product to the bulk dynamic viscosity characterizes the change in mechanical properties of the liquid in the process of separating the bodies. For steel disks, the thickening factor" (with det 10 F = 3900 dyn/cm ) has... 

J4 = Colburn factor given by equation proposed by Pierce length of tube, m = Prandtl number Reynolds number = velocity, m/sec p = dynamic viscosity, sPa (pascal-sec) p = density, kg/m b = evaluate at bulk temperature w = evaluate at wall temperature kg = kilogram... 

The relationship of isoviscosity calculated by Eq (5) and a distance apart from the solid surface is shown in Fig. 7. For different kinds of solid materials with different surface energy, the isoviscosity becomes very large as the film thickness becomes thinner. It increases about several to more than ten times that of bulk fluid when it is close to the solid surface. In the thick film region, the isoviscosity remains a constant, which is approximately equal to the dynamic viscosity of bulk liquid. Therefore, the isoviscosity of lubricant smoothly... 

For effective demulsification of a water-in-oil emulsion, both shear viscosity as well as dynamic tension gradient of the water-oil interface have to be lowered. The interfacial dilational modulus data indicate that the interfacial relaxation process occurs faster with an effective demulsifier. The electron spin resonance with labeled demulsifiers suggests that demulsifiers form clusters in the bulk oil. The unclustering and rearrangement of the demulsifier at the interface may affect the interfacial relaxation process. 

Viscosity, defined as the resistance of a liquid to flow under an applied stress, is not only a property of bulk liquids but of interfacial systems as well. The viscosity of an insoluble monolayer in a fluid-like state may be measured quantitatively by the viscous traction method (Manheimer and Schechter, 1970), wave-damping (Langmuir and Schaefer, 1937), dynamic light scattering (Sauer et al, 1988) or surface canal viscometry (Harkins and Kirkwood, 1938 Washburn and Wakeham, 1938). Of these, the last is the most sensitive and experimentally feasible, and allows for the determination of Newtonian versus non-Newtonian shear flow. 

An LDPE resin was used for this study. The resin had a melt index of 2.0 dg/min (2.16 kg, 190 °C) and a solid density of 0.922 g/cmT The shear viscosity was reported previously [37] thermal properties are provided in Chapter 4 bulk density as a function of temperature and pressure is provided in Fig. 4.4 and the coefficients of dynamic friction are provided in Appendix A5. The lateral stress ratio was measured at 0.7 [38] using the device shown in Fig. 4.8. 

Here pg and p f are the mass densities of the gel and the solvent, respectively, K is a bulk modulus, c0 is the speed of sound, and i s is the solvent shear viscosity. The solvent bulk viscosity has been neglected. The terms proportional to / arise from an elastic coupling in the free energy between the density deviation of gel and that of solvent The p in Eq. (6.1) coincides with the shear modulus of gels treated so far. We neglect the frequency-dependence of the elastic moduli. It can be important in dynamic light scattering, however, as will be discussed in the next section. 

The dissipation function, also called viscous dissipation, represents the irreversible conversion of kinetic energy into thermal energy. Since the dynamic viscosity p, is positive and all the terms are squared, the first two terms of the dissipation must be always positive. The bulk viscosity can be negative the Stokes hypothesis (Section 2.11) says that k = —2p/3. It turns out that the necessary condition for the dissipation function to be positive is that... 

Fig. 2.17 Frequency dependence of dynamic shear moduli computed using a model for the linear viscoelasticity of a cubic phase based on slip planes, introduced by Jones and McLeish (1995). Dashed line G, solid line G".The bulk modulus is chosen to be G — 105 (arb. units). The calculation is for a slip plane density AT1 - 10 5 and a viscosity ratio rh = = 1, where rjs is the slip plane viscosity and t] is the bulk viscosity. The strain...

Unlike in three dimensions, where liquids are often considered incompressible, a surfactant monolayer can be expanded or compressed over a wide area range. Thus, the dynamic surface tension experienced during a rate-dependent surface expansion, is the result of the surface dilational viscosity, the surface shear viscosity, and elastic forces. Often, the contributions of shear and/or the dilational viscosities are neglected during stress measurements of surface expansions. Isolating interfacial viscosity effects is difficult because, since the interface is connected to the substrate on either side of it, the interfacial viscosity is coupled to the two bulk viscosities. 

The bulk rheological properties of the PFPEs, including the melt viscosity (p), storage modulus (G ), and loss modulus (G"), were measured at several different temperatures via steady shear and dynamic oscillation tests. Note that we denoted p as melt viscosity and r as solution viscosity. An excellent description of the rheology is available in Ferry [99]. 

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