Kelvin-Helmholtz Rayleigh-Taylor

Beale, J.C., and R. D. Reitz. 1999. Modeling spray atomization with the Kelvin-Helmholtz/Rayleigh-Taylor hybrid model. Atomization Sprays 9(6) 623-50. 

As described previously, in the atomization sub-model, 232 droplet parcels are injected with a size equal to the nozzle exit diameter. The subsequent breakups of the parcels and the resultant droplets are calculated with a breakup model that assumes that droplet breakup times and sizes are proportional to wave growth rates and wavelengths obtained from the liquid jet stability analysis. Other breakup mechanisms considered in the sub-model include the Kelvin-Helmholtz instability, Rayleigh-Taylor instability, 206 and boundary layer stripping mechanisms. The TAB model 310 is also included for modeling liquid breakup. 

However numerical simulations of early supernova-driven winds fail to find any evidence for substantial gas ejection from luminous ( L ) galaxies. One can ask what is wrong with the hydrodynamic simulations Certainly, the simulations lack adequate resolution. Rayleigh-Taylor instabilities enhance wind porosity and Kelvin-Helmholtz instabilities enhance wind loading of the cold interstellar medium. Both effects are certain to occur and will enhance the wind efficacity. Yet another omission is that one cannot yet resolve the motions of massive stars before they explode. This means that energy quenching is problematic and the current results are inconclusive for typical massive galaxies. 

Figure 11 Phenomena connected with drop breakup (a) deformation (splitting) of droplets, (b) deformation into lenticular shape, (c) development and separation of the boundary layer, (d) velocity distribution near the separation point of the boundary layer, (e) Kelvin Helmholtz instability, and (f) Rayleigh Taylor instability, pi < P2-...

It is anticipated that the results of calculations will show the governing mechanisms of primary atomization. They will indicate the relative importance of turbulence, the Kelvin-Helmholtz instability, the Rayleigh-Taylor instability, the initial perturbation level (attributable to cavitation or oscillations in fuel injection equipment), and other phenomena. The quantitative detail of the simulations will provide information and inspiration for the construction of a new generation of spray models. The proposed code can be used for other kinds of simulations, including wall impingement, liquid film flow, and impinging injections. 

Kelvin-Helmholtz, 39-42, 48 pyroacoustic, 66, 67, 69, 71 Rayleigh-Taylor, 39, 41, 42, 322 shear-layer, 201, 209 swirling, 124 surface, 322... 

S. S. Yoon, R. A. Jepsen, S. C. James, J. Liu, G. Aguilar Are drop-impact phenomena described by Rayleigh-Taylor or Kelvin-Helmholtz theory . Drying Technol., 27, 316-321 (2009). 

Fig. 9.1 Schematic illustration of a drop breakup caused by Kelvin-Helmholtz (KH) or Rayleigh-Taylor (R-T) instabilities. The breakup mechanisms are ciassified with respect to the (increasing) Weber number as bag, stripping (shear) and catastrophic breakup...

Kelvin-Helmholtz instability arises because of shear along an interface between two different fluids. Being related to turbulence and transition phenomena, it also describes the onset of ocean wave formation, jetting instabilities, and cloud formation. In microfluidics, it is commonly seen in fluid-fluid interfaces. It is not to be confused with Rayleigh-Taylor or Rayleigh instability ( Rayleigh-Taylor instability). 

Assume that the peak is characterized by the critical condition for Kelvin-Helmholtz instability and for this critical wavelength the fastest growing wavelength from Rayleigh-Taylor instability can be used. Show that it can be used to obtain a correlation for the peak heat flux. Also assume where needed that... 

Breakup of the melt is thought to be governed by hydrodynamic instabilities, notably the Rayleigh-Taylor and Kelvin-Helmholtz instabilities. These breakup processes are driven by relative velocity differences or accelerations between the melt and the water and steam. 

The Kelvin-Helmholtz instability is similar to the Rayleigh-Taylor instability, except that the former allows a relative velocity between the fluids, u. Using the same concept of Grace et al. (1978), Kitscha and Kocamustafaogullari (1989) applied the Kelvin-Helmholtz instability theory to model the breakup of large bubbles in liquids. Wilkinson and van Dierendonck (1990) applied the critical wavelength to explain the maximum stable bubble size in high-pressure bubble columns ... 

The comparison of experimental maximum bubble sizes and the predictions by various instability theories is shown in Fig. 11. The internal circulation model can reasonably predict the observed pressure effect on the maximum bubble size, indicating that the internal circulation model captures the intrinsic physics of bubble breakup at high pressures. The comparison of the predictions by different models further indicates that bubble breakup is governed by the internal circulation mechanism at high pressures over 1.0 MPa, whereas the Rayleigh-Taylor instability or the Kelvin-Helmholtz instability is the dominant mechanism at low pressure. 

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