Fluid mechanics effects

These observations imply that both fluid-mechanical effects and surface-force effects control the particle release. 

Flat flames can be made to impinge onto surfaces. Such strained flames can be used for a variety of purposes. On the one hand, these flames can be used in the laboratory to study the effects of strain on flame structure, and thus improve understanding of the fluid-mechanical effects encountered in turbulent flows. It may also be interesting to discover how a cool surface (e.g., an engine or furnace wall) affects flame structure. Even though the stagnation-flow situation is two-dimensional in the sense that there are two velocity components, the problem can be reduced to a one-dimensional model by similarity, as addressed in the book. 

Surface tension gradient effects add to the better known phenomena of density-gradient-driven convection, concentration-gradient-driven diffusion and electrical-potential-gradient-driven ion migration, which appear in the existing theory of cells and electrodes. The potential difference of a working cell is affected by all the near electrode effects mentioned here. The experimental and analytical difficulty is to separate the variables. Indeed the fluid mechanical effects stir the electrochemical reaction, and make cause and effect difficult to discern. 

These great differences are due to "sweep," "adverse mobility ratios," "conformance," and other fluid mechanical effects (see next section) that are exacerbated by the natural heterogeneities in porous rocks and whose alleviation is the purpose of sweep and mobility control technology. 

The CO2 flow velocity and compressibility were not taken into account in the purely kinetic equation (5-45). Taking into account the fluid mechanics effects leads to the following correction of formula (5-50) for characteristic VT-relaxation time (Fridman, 1986) ... 

Clearly, as discussed in some detail by Orrin et al (11), fluid mechanical effects are not the whole story when one is using the plasma jet as a source of ignition. Figure 2(B) show a series of photographs of ignition by a plasma jet and for comparison (Figure 2(C)) by a conventional spark in a combustion bomb containing a methane-air mixture at four atmospheres pressure. 

Electrospinning a polymer solution could produce thin fibers with a variety of cross-sectional shapes. Branched fibers, flat ribbons, ribbons with other shapes, and fibers that were split longitudinally from larger fibers were observed. The transverse dimensions of these asymmetric fibers were typically 1000 to 2000 nm, measured in the widest direction. The observation of fibers with these cross-sectional shapes from a number of different kinds of polymers and solvents indicated that fluid mechanical effects, electrical charge carried with the jet, and evaporation of the solvent all contributed to the formation ofthe fibers. ... 

Advances in Engineering Fluid Mechanics Effect of Surfactants on Polymer Viscosity... 

The NPSHr of reciprocating pumps is usually calculated for incipient cavitation conditions from the maximum entry pressure losses [18, 19], which are largely dictated by the characteristics of the suction check valve. The manufacturer s NPSHr data are in general based on these fluid mechanical effects. Typical values for the NPSHr range between 1 and 3 m for liquid CO2 (this corresponds to a pressure requirement of between 0.1 and 0.3 bar). 

As soon as one is concerned with wrinkled fronts and/or inhomogeneous flows, the flame cannot be described by a pure reaction-diffusion model. Because of the gas expansion produced by the temperature increase in the preheated zone, the streamlines are deflected across the tilted front and a strong coupling with hydrodynamics is developed. When the size A of the wrinkles of the front is large compared to the flame thickness d, the corresponding fluid mechanical effects can be splitted in two distinct parts ... 

McGillicuddy, J.W., Chambers, S.D., Galligan, D.T., Hirschl, R.B., Bartlett, R.H., and Cook, K.E. 2005. In vitro, fluid mechanical effects of thoracic artificial lung compliance. ASAIO J 51 789-94. 

The drag coefficients for disks (flat side perpendicular to the direction of motion) and for cylinders (infinite length with axis perpendicular to the direclion of motion) are given in Fig. 6-57 as a Function of Reynolds number. The effect of length-to-diameter ratio for cylinders in the Newton s law region is reported by Knudsen and Katz Fluid Mechanics and Heat Transfer, McGraw-Hill, New York, 1958). 

In some cases, the ventilation process in the room can be simplified and mechanisms of air and contaminant movement under the influence of each of the above factors can be described using simplified theoretical principles of fluid mechanics, empirical data, and observations from numerous research studies. In general, the ventilation process in a room is complex and different factors have a joint effect on airflow patterns and characteristics, in continued spaces and in industrial buildings particularly. 

Sawyer, R. A. 1963. Two-dimensional reattaching jet flows including the effects of curvature on entrainment. Journal of Fluid Mechanics, vol. 17, pp. 481-498. 

One of the common problems associated with underwater pelletizers is the tendency of the die holes to freeze off. This results in nonuniform polymer melt flow, increased pressure drop, and irregular extrudate shape. A detailed engineering analysis of pelletizers is performed which accounts for the complex interaction between the fluid mechanics and heat transfer processes in a single die hole. The pelletizer model is solved numerically to obtain velocity, temperature, and pressure profiles. Effect of operating conditions, and polymer rheology on die performance is evaluated and discussed. 

P. Clavin and F.A. Williams. Effects of molecular diffusion and of thermal expansion on the structure and dynamics of premixed flames in turbulent flows of large scale and low intensity. Journal of Fluid Mechanics, 116 251-282,1982. 

The NACE Landrum Wheel velocity test, originally TM0270-72, is typical of several mechanical-action immersion test methods to evaluate the effects of corrosion. Unfortunately, these laboratory simulation techniques did not consider the fluid mechanics of the environment or metal interface, and service experience very seldom supports the test... 

In order to accurately describe such oscillations, which have been the center of attention of modern liquid state theory, two major requirements need be fulfilled. The first has already been discussed above, i.e., the need to accurately resolve the nonlocal interactions, in particular the repulsive interactions. The second is the need to accurately resolve the mechanisms of the equation of state of the bulk fluid. Thus we need a mechanistically accurate bulk equation of state in order to create a free energy functional which can accurately resolve nonuniform fluid phenomena related to the nonlocality of interactions. So far we have only discussed the original van der Waals form of equation of state and its slight modification by choosing a high-density estimate for the excluded volume, vq = for a fluid with effective hard sphere diameter a, instead of the low-density estimate vq = suggested by van der Waals. These two estimates really suggest... 

An alternative to the rotating disk method in a quiescent fluid is a stationary disk placed in a rotating fluid. This method, like the rotating disk, is based on fluid mechanics principles and has been studied using benzoic acid dissolving into water [30], Khoury et al. [31] applied the stationary disk method to the study of the mass transport of steroids into dilute polymer solutions. Since this method assumes that the rotating fluid near the disk obeys solid body rotation, the stirring device and the distance of the stirrer from the disk become important considerations when it is used. A similar device was developed by Braun and Parrott [32], who used stationary spherical tablets in a stirred liquid to study the effect of various parameters on the mass transport of benzoic acid. 

In a biphasic solid-liquid medium irradiated by power ultrasound, major mechanical effects are the reduction of particles size leading to an increased surface area and the formation of liquid jets at solid surfaces by the asymmetrical inrush of the fluid into the collapsing voids. These liquid jets not only provide surface cleaning but also induce pitting and surface activation effects and increase the rate of phase mixing, mass transfer and catalyst activation. 

An important concept in fluid mechanics is the hydrodynamic boundary layer (also known as Prandtl layer) or region where the effective disturbance... 

Komori, S., J. C. R. Hunt, K. Kanzaki, and Y. Murakami (1991b). The effects of turbulent mixing on the correlation between two species and on concentration fluctuations in non-premixed reacting flows. Journal of Fluid Mechanics 228, 629-659. 

The vanishing effect of molecular diffusivity on turbulent dispersion Implications for turbulent mixing and the scalar flux. Journal of Fluid Mechanics 359, 299-312. 

To examine the effect of turbulence on flames, and hence the mass consumption rate of the fuel mixture, it is best to first recall the tacit assumption that in laminar flames the flow conditions alter neither the chemical mechanism nor the associated chemical energy release rate. Now one must acknowledge that, in many flow configurations, there can be an interaction between the character of the flow and the reaction chemistry. When a flow becomes turbulent, there are fluctuating components of velocity, temperature, density, pressure, and concentration. The degree to which such components affect the chemical reactions, heat release rate, and flame structure in a combustion system depends upon the relative characteristic times associated with each of these individual parameters. In a general sense, if the characteristic time (r0) of the chemical reaction is much shorter than a characteristic time (rm) associated with the fluid-mechanical fluctuations, the chemistry is essentially unaffected by the flow field. But if the contra condition (rc > rm) is true, the fluid mechanics could influence the chemical reaction rate, energy release rates, and flame structure. 

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