Surfactant turbulent flow

Hetsroni G, Mosyak A, Bemheim-Groswasser A, Talmon Y, Zakin JL (2003c) The effect of cationic surfactant on turbulent flow patterns. J Heat Transfer ASME 125 947-950 Hetsroni G, Mosyak A, Segal Z, Pogrebnyak E (2002a) Two-phase flow patterns in paradel microchannels. Int J Multiphase Flow 9 341-260... 

Malyusov ei al. (M6), 1955 in very short wetted-wall columns (no rippling) (3) flowing over spheres. Entry and end effects studied, also effects of adding surfactant. Study of distillation in wetted-wall columns, taking into account the effects of laminar and turbulent flow of vapor phase. 

Emulsion aging rates increase with temperature. Aging rates in turbulent flow appear to become arrested after a certain point, generally being less than the rates observed in laminar flow. Aging rates are suppressed by increased surfactant concentration as a result of the anticoalescence action of the surfactant. 

There are many factors that determine whether a collision results in a coalescence. The processes by which two drops coalesce are those of film thinning and final rupture of the intervening film. These processes are determined by factors such as surfactants, mass transfer, surface tension gradients, physical properties, Van der Waals forces, and double-layer forces. In a turbulent flow field the situation is more involved.The droplets must first collide and remain in contact for a sufficient time for the coalescence to take place. A realistic coalescence efficiency will account for these factors. 

Such systems can form the thread-like micelles necessary for surfactant solutions to be DR under the shearing conditions in turbulent flows. The thread-like micelles align themselves along the flow direction causing DR of the solution. Details of microstructures DR of aqueous cationic surfactant solutions vary with surfactant chemical structure and concentration, counterion chemical structure and... 

Turbulent streaks in Newtonian flows have an average spacing of 100 in units. In polymer or surfactant DR flows, the spacing is increased and the streaks are more persistent and more stable. ... 

Because of the interaction of the two complicated and not well-understood fields, turbulent flow and non-Newtonian fluids, understanding of DR mechanism(s) is still quite limited. Cates and coworkers (for example, Refs. " ) and a number of other investigators have done theoretical studies of the dynamics of self-assemblies of worm-like micelles. Because these so-called living polymers are subject to reversible scission and recombination, their relaxation behavior differs from reptating polymer chains. An additional form of stress relaxation is provided by continuous breaking and repair of the micellar chains. Thus, stress relaxation in micellar networks occurs through a combination of reptation and breaking. For rapid scission kinetics, linear viscoelastic (Maxwell) behavior is predicted and is observed for some surfactant systems at low frequencies. In many cationic surfactant systems, however, the observed behavior in Cole-Cole plots does not fit the Maxwell model. 

Drag reduction in turbulent flows of dilute high-polymer of surfactant solutions is a striking... 

Tubular Precipitator. This type of continuous operation may be employed to reduce polydispersity of precipitates (Raphael et al. 1997 Raphael and Rohani 1999). The tubular precipitator may operate either under the turbulent flow or laminar flow regime. The reactants are added into the inlet section equipped with static mixers and may also enter as a multi-port feed along the length of the tubular precipitator. If the reactant feeding streams are too concentrated or if too excessive formation of precipitate occurs in the inlet section of the precipitator, a third stream of solvent is also fed to dilute the flowing suspension. The latter may contain a protective colloid or surfactant that prevent agglomeration of precipitate. 

POLYMER AND SURFACTANT DRAG REDUCTION IN TURBULENT FLOWS... 

Surfactant solutions containing TLMs that resemble polymer chains may reduce friction energy loss in turbulent flows by up to 90% at relatively low surfactant concentrations under appropriate flow and temperature conditions. 

Small-angle neutron scattering (SANS) [Cates and Candau, 1990 Rehage and Hoffmann, 1991] and cryo-TEM studies [Hoffmann et al., 1985] have shown that surfactant solutions with vesicle structures in the quiescent state can transform to TLMs under shear, accounting for the rare and unexpected observations that solutions with vesicle structures can be DR in turbulent flow flelds [Zheng et al., 2000]. 

Turbulent drag reduction in homogeneous flows by polymer or surfactant additives is a striking phenomenon with both theoretical and practical implications. On the theoretical side, it remains a challenge to fully understand the drag reduction mechanism and the interaction details between DRAs and the turbulent flow field. New methods, especially computational ones, have been developed to solve this problem, such as direct numerical simulations and stochastic simulations. On the application... 

Gasljevic, K., An experimental investigation of drag reduction by surfactant solutions and of its implementation in hydronic systems (turbulent flow, heat transfer), Ph.D. dissertation, Department of Mechanical Engineering. University of Cahfomia at Santa Barbara, 1995. 

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