Jet model

FIGURE 10.71 The ratio of the horizontal component of the fluid velocity to its local maximum u/ u, as a function of t), at x = 0.75 m for the experimental results, the numerical results obtained using the commercial package for the offset and equivalent wall jet models, and the original and modified Verhoff empirical formulae. 

Cipollina, A., Bonfiglio, A., Micale, G., Brucato, A. Dense jet modelling applied to the design of dense effluent diffusers. Desalination 167, 459—468 (2004)... 

The numerical jet model [9-11] is based on the numerical solution of the time-dependent, compressible flow conservation equations for total mass, energy, momentum, and chemical species number densities, with appropriate in-flow/outfiow open-boundary conditions and an ideal gas equation of state. In the reactive simulations, multispecies temperature-dependent diffusion and thermal conduction processes [11, 12] are calculated explicitly using central difference approximations and coupled to chemical kinetics and convection using timestep-splitting techniques [13]. Global models for hydrogen [14] and propane chemistry [15] have been used in the 3D, time-dependent reactive jet simulations. Extensive comparisons with laboratory experiments have been reported for non-reactive jets [9, 16] validation of the reactive/diffusive models is discussed in [14]. 

For their heuristic value, two superficially different explanations are proposed to explain the potential to react. On the one hand, the experimental endotherm of the reaction at the equivalence point is shown to be quite consistent with the heat flowing in the hot core of the jet, for a jet model consistent with what we might expect. On the other hand, for the same heat flow and jet model, the yield is shown to be consistent with the flow rate of e.g., ions at the point of mixing and it may equally well be postulated that the ions or some other identifiable species are in fact an active ingredient being titrated. 

A jet model of flow around balls in a porous layer was proposed in [153]. Such flow is characterized by a decrease of the drag due to the suppression of wakes. For a sufficiently close packing ( > 0.35), the layer becomes steady-state. For the drag coefficient of a ball in such a system, the following empirical formula was proposed ... 

Much of the available research agrees that supercritical jets typically behave similar to turbulent gas jets, specifically variable-density gas injection. Chehroudi et al. [6] first found favorable comparison between measured transcritical (Type II or IV) jet spreading angles and those of variable-density gas jets. Barata et al. [7] used numerical variable-density gas jet models to predict experimental results, and found good agreement. 

Branam and Mayer [8] have compared supercritical core length measurements to those of variable-density gas jets, and found that the two matched well. However, the authors believed that more parameters were needed to be able to accurately predict transcritical core lengths, as Reynold s number was the sole parameter used in their gas jet model. They considered quantities such as the density ratio and reduced temperature and pressure to be important. 

The possibility of coupling the model to source term models or the integration of source term models (such as jet models and pool evaporation) should also be addressed here. 

Mathematical models for droplet vaporization and condensation have also been developed by Hewitt and Pattison (1992), with the aim of incorporating the aerosol model into a heavy gas dispersion model. Woodward and Papadourakis (1991) have presented a two-phase jet model, including a description of droplet vaporization. Woodward et al. (1995) have devel-... 

The wall-jet model corresponds to a tangential reflection of the droplets and leads to a droplet flow over the surface. No direct droplet-wall contact occurs, meaning that the wall-jet model conforms to a droplet flow during film boiling. 

The use of the stationary jet model JET 1 makes it possible to calculate, to within 20% the distance along the axis at which the conentration is equal to the LFL amd also the volume of the flammable mixture formed. 

Forest, M.G. and Wang, Q. 1990 Change-of-type behavior in viscoelastic slender jet models. Theoret. Comput. Fluiud Dynam., 2, pp. 1-25. 

In addition to its use as a pure friability test, this type of test has also been used in the above-mentioned grid-jet modeling approach of Ghadiri and coworkers (Ghadiri et al., 1992a, 1994, 1995 Boerefijn et al., 1998, 2000). In this approach the particles were fed in a single array to the eductor. 

Bittorf and Kresta (2002) have applied a wall jet model successfiiUy to predict the cloud height data of Hicks et al. (1997) and Bnjalski et al. (1999). The proposed model for purely axial impellers (i.e., A310 or HE3) is... 

Figure 5.6 Some of the most beneficial research with physical models has been accomplished with wind tunnels. Here a ram jet model is being studied in a 10 ft. X 10 ft. test section. (Courtesy of the National Aeronautics and Space Administration.)...

---