Mixing behavior, fluid

New solvents should be examined for compatibility with photochemistry. Laser light scattering is used with a variable-volume view cell in an almost fully automated setup for accurately determining the phase behavior of pure or mixed fluids. The automated light-scattering techniqne yields good data, is relatively quick, and is non-labor inten-... 

LAMINAR FLOW. A condition of fluid flow in a closed conduit in which the fluid panicles or "streams tend to move parallel to the flow axis and not mix. This behavior is characteristic of low flow rates and high viscosity fluid flows. As the flow rate increases (or viscosity significantly decreasesi. the streams continue to flow parallel until a velocity is reached where the streams waver and suddenly break into a diffused pattern. This point is called the critical velocity. See also Turbulent Flow. 

Capillary forces in mixed fluid phase conditions are inversely proportional to the curvature of the interface. Therefore, menisci introduce elasticity to the mixed fluid, and mixtures of two Newtonian fluids exhibit global Maxwellian response. For more details see Alvarellos [1], his behavior is experimentally demonstrated with a capillary tube partially filled with a water droplet. The tube is tilted at an angle (3 smaller than the critical angle that causes unstable displacement. Then, a harmonic excitation is applied to the tube in the axial direction. For each frequency, the amplitude of the vibration is increased until the water droplet becomes unstable and flows in the capillary. Data in Figure 3 show a minimum required tube velocity between 40 and 50 Hz. This behavior indicates resonance of the visco-elastic system. The ratio of the relaxation time and characteristic time for pure viscous effect is larger than 11.64. 

The nature of mixed fluid solvent systems and their role in various supercritical fluid applications is complicated by the increased complexity of the phase behavior. Several different types of mixed fluid phase behavior have been identified (17,18), some of... 

We have considered the situation of only one phase for any mixture composition this means that there is no surface tension and the fluid behavior is completely characterized by the turbulent flow described by the mass and momentum balance equations. To solve these equations, one needs to model the diffusional mixing of the species present in the system and to identify local values of the thermodynamic and transport properties, as considered in Section 3.2. Here we just point out that once the methods for predicting local values of fluid density and viscosity have been worked out, one should be able to integrate Eqs. (10) and (11). 

Bellan J. Supercritical (and subcritical) fluid behavior and modeling drops, streams, shear and mixing layers, jets and sprays. Prog Energy Combust Sci 2000 26 329-366. 

Equations 34 through 39 constitute a rational set of mixing rules, based in part upon the accumulated experience of many investigators with special cases of the cubic equation. Although the rules are reasonable, and in some cases (notably for b) have even been accorded theoretical significance, they must be regarded in fact as no more than useful empiricisms, for the cubic equation itself is no more than a useful (albeit often surprisingly powerful) approximator of real-fluid behavior. 

Solid particles, which adhere to fluid-fluid surfaces so that part of their surface is exposed to one fluid and part to the other fluid, exhibit a finite contact angle at the relevant surface. For almost three-quarters of a century, it has been known that such particles may have a drastic effect on the behavior of dispersions formed by mixing fluids. Two of the earliest publications are those of Ramsden [140] and Pickering [141] concerning the effect of particles on oil-water emulsion behavior. A few years later, Bartsch [142] described the stabilizing effect of hydrophobed mineral particles on froths formed by aqueous solutions of 3-methylbutanol. 

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