Swirl parameters

Manglik and Bergles [272,273] made an extensive review on the study of laminar and turbulent flow in circular ducts with inserted tape. For laminar flow, the dimensional swirl parameter Sw was incorporated in the correlation of friction factor. This parameter considers the thickness of inserted tape 8,... 

Dimensionless mean drop size Swirl parameter... 

For a certain value of swirl flow rate, the swirl velocity should be equal to the circumferential velocity of the rotary cup. It is assumed that at this flow rate the relative velocity between the thread and the ambient air is very low. Based on the geometry of the gas distributor and the swirl flow rate, the swirl velocity around the LamRot can be estimated. The swirl parameter of the swirl chamber is A =4.94 and defined in (22.16). 

Typical re-entrant piston-bowl design for a small, high-speed direct-injection Cl engine. (From Kook, S., Bae, C., Miles, P.C., Choi, D., Bergin, M., and Reitz, R.D., The Effect of Swirl Ratio and Fuel Injection Parameters on CO emission and Fuel Conversion Efficiency for High-Dilution, Low-Temperature Combustion in an Automotive Diesel Engine, SAE, 2006-01-019 2006. With permission.)... 

In fan spray atomization, the effects of process parameters on the mean droplet size are similar to those in pressure-swirl atomization. In general, the mean droplet size increases with an increase in liquid viscosity, surface tension, and/or liquid sheet thickness and length. It decreases with increasing liquid velocity, liquid density, gas density, spray angle, and/or relative velocity between liquid and surrounding air. 

Figure 17.1 (a) Countercurrent Swirl Combustor experimental facility (6) isometric view of the burner and (c) cross-sectional view of the burner indicating relevant parameters... 

The trend observed in Fig. 17.5 illustrates the importance of swirl. The image sequence corresponds to data points using front swirl angles of 31°, 41°, and 68° with all other parameters fixed 4> = 0.68, RMS = 0.1, L = 12 in. (30.48 cm), total mass flow rate of 0.03 kg/s, and rear swirl angle of 85°). The chamber averaged swirl is defined as the sum of the front and rear drive angular momentum divided by the chamber radius and total mass flow. This provides a measure of the swirl experienced by the combustion chamber confined flow and allows comparison between different test conditions. The flame speed ratio... 

Little is known about the interactions between the transport properties in the melt and the production of defects at the melt-crystal interface. An exception is the swirl microdefect seen during processing of dislocation-free silicon wafers (118). The origins of this defect (119) are related to temperature oscillations and remelting of the interface. Kuroda and Kozuka (120) have studied the dependence of temperature oscillations on operating parameters in a CZ system but have not linked the oscillations to convective instabilities in the melt. 

Macroemulsions are in a nonequilibrium state and their properties depend not only on parameters such as temperature and composition but also on the method of preparation. This leads to a high level of complexity when it comes to scientific experimental studies or practical applications. Recipes which work at one place often do not lead to the same result in another laboratory, because seemingly insignificant details have a big effect. How oil and water are mixed if, for instance, they are shaken or swirled or if air is bubbled through, and the wetting behavior of the vessel, can change the outcome dramatically. 

In studies that involve the CFD analysis of turbulent fluid flow, the k-t model is most frequently used because it offers the best compromise between width of application and computational economy (Launder, 1991). Despite its widespread popularity the k-e model, if used to generate an isotropic turbulent viscosity, is inappropriate for simulation of turbulent swirling flows as encountered in process equipment such as cyclones and hydrocyclones (Hargreaves and Silvester, 1990) and more advanced turbulence models such as the ASM or the RSM should be considered. Because these models are computationally much more demanding and involve an increased number of empirical parameters compared to the k-e model, other strategies have been worked out (Boysan et al, 1982 Hargreaves and Silvester, 1990) to avoid the isotropic nature of the classical k-e model. 

Parameters that most influence the behavior of a spray are the viscosity, the thixotropy, the surface tension, and the density. Modification of the swirl chamber and the inlet channels makes it possible to adjust the spray performance to the patient s requirements (Fig. 3). The particle size distribution can be altered by varying the dimensions and the geometry of the orifice, as well as the pressure build-up in the volume chamber prior to dispensing. One of the major criteria is to keep the fraction of extremely small particles very low to avoid partial inhalation of the drug formulation. 

Turbine designs are intermediate between paddles and propellers. Turbines are effective mixers over a wide viscosity range and provide a very versatile mixing tool. The ratio of radial to tangential flow, the predominating parameters with this impeller, increases as the operating speed increases. Pitched-blade turbines are sometimes used to increase axial flow. Baffles must be used to limit swirling unless the turbine is shrouded. 

This turbulence model is similar to the standard k-s model, but with altered model parameter values and the effect of swirl on turbulence is included in the RNG mode intending to enhance the accuracy of swirling flow simulations. 

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