Helical modes in combined Rayleigh–Taylor and Kelvin–Helmholtz instability of a cylindrical interface

Vadivukkarasan, M.; Panchagnula, Mahesh V.

doi:10.1177/1756827716642159

Cited by 19 publications

(5 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This also suggests the possibility of hybrid KH-RT instability where RT waves are modulated on the crest of KH waves (Zhao et al 2014;Mitkin & Theofanous 2017;Sharma et al 2021c) and appear as front-surface corrugations. It is worth noting that the 'hybrid KH-RT' mechanism referred to here is different from the 'combined KH-RT' mechanism studied by Vadivukkarasan & Panchagnula (2016 in which the KH and the RT instabilities occur simultaneously as equal contributors to the destabilization process. Whereas, in the hybrid KH-RT mechanism, the KH waves appear first, leading to an increase in the area of the air-liquid interface normal to the airflow direction, which provides a suitable platform for the subsequent occurrence of RT instability.…”

Section: Stage Ii: Rt Instability Asmentioning

confidence: 78%

Shock-induced aerobreakup of a polymeric droplet

et al. 2023

View full text Add to dashboard Cite

Droplet atomization through aerobreakup is omnipresent in various natural and industrial processes. Atomization of Newtonian droplets is a well-studied area; however, non-Newtonian droplets have received less attention despite their being frequently encountered. By subjecting polymeric droplets of different concentrations to the induced airflow behind a moving shock wave, we explore the role of elasticity in modulating the aerobreakup of viscoelastic droplets. Three distinct modes of aerobreakup are identified for a wide range of Weber number $({\sim }10^2\unicode{x2013}10^4)$ and elasticity number $({\sim }10^{-4}\unicode{x2013}10^2)$ variation: these modes are vibrational, shear-induced entrainment and catastrophic breakup modes. Each mode is described as a three-stage process. Stage I is droplet deformation, stage II is the appearance and growth of hydrodynamic instabilities and stage III is the evolution of liquid mass morphology. It is observed that elasticity plays an insignificant role in the first two stages but a dominant role in the final stage. The results are described with the support of adequate mathematical analysis.

show abstract

Section: Stage Ii: Rt Instability Asmentioning

confidence: 78%

Shock-induced aerobreakup of a polymeric droplet

et al. 2023

View full text Add to dashboard Cite

show abstract

“…A complete understanding of the relation between the RTI and the KHI is important in understanding the hydrodynamic instability-driven mixing processes. In addition to the growth rate and final state, some studies have been made on the early linear and early nonlinear evolution of the coupled instability [39][40][41][42][43][44][45][46][47][48][49] . Both the instability modes and devolution processes that may be manifested when two such mechanisms occur simultaneously are of current interest.…”

Section: Introductionmentioning

confidence: 99%

“…Akula et al 43 showed that the superposition of shear on RTI at small Atwood number increases the mixing width and growth rate at early times. Vadivukkarasan et al [44][45][46] described the 3D destabilization characteristics of cylindrical and annular interfaces under the combined RTKHI, and the effects of various parameters on the most unstable wavenumbers were studied. Sarychev et al 47 found that an undulating topography on the interface coating/base material is resulted from the coupled RTKHI.…”

Section: Introductionmentioning

confidence: 99%

Effects of the initial perturbations on the Rayleigh-Taylor-Kelvin-Helmholtz instability system

Chen,

Xu,

Zhang

et al. 2021

Preprint

View full text Add to dashboard Cite

In the paper, the effects of initial perturbations on the Rayleigh-Taylor instability (RTI), Kelvin-Helmholtz instability (KHI), and the coupled Rayleigh-Taylor-Kelvin-Helmholtz instability (RTKHI) systems are investigated using a multiple-relaxation-time discrete Boltzmann model. Six different perturbation interfaces are designed to study the effects of the initial perturbations on the instability systems. It is found that the initial perturbation has a significant influence on the evolution of RTI. The sharper the interface, the faster the growth of bubble or spike. While the influence of initial interface shape on KHI evolution can be ignored. Based on the mean heat flux strength D 3,1 , the effects of initial interfaces on the coupled RTKHI are examined in detail. The research is focused on two aspects: (i) the main mechanism in the early stage of the RTKHI, (ii) the transition point from KHI-like to RTI-like for the case where the KHI dominates at earlier time and the RTI dominates at later time. It is found that the early main mechanism is related to the shape of the initial interface, which is represented by both the bilateral contact angle θ 1 and the middle contact angle θ 2 . The increase of θ 1 and the decrease of θ 2 have opposite effects on the critical velocity. When θ 2 remains roughly unchanged at 90 degrees, if θ 1 is greater than 90 degrees (such as the parabolic interface), the critical shear velocity increases with the increase of θ 1 , and the ellipse perturbation is its limiting case; If θ 1 is less than 90 degrees (such as the inverted parabolic and the inverted ellipse disturbances), the critical shear velocities are basically the same, which is less than that of the sinusoidal and sawtooth disturbances. The influence of inverted parabolic and inverted ellipse perturbations on the transition point of the RTKHI system is greater than that of other interfaces: (i) For the same amplitude, the smaller the contact angle θ 1 , the later the transition point appears; (ii) For the same interface morphology, the disturbance amplitude increases, resulting in a shorter duration of the linear growth stage, so the transition point is greatly advanced.

show abstract

“…As mentioned earlier, the finite amplitude of waves on the jet surface as well as jet flapping may trigger the RT instability leading to the generation of droplets and ligaments. However, the possibility of combined action of both instabilities has been discussed by Vadivukkarasan and Panchagnula 25 who developed a three-dimensional temporal stability model for the growth of the instability and identified short wavelength helical mode when both KH and RT mechanisms are active on the cylindrical liquid jet. Recently, Matas and Cartellier 26 recognized the flapping instability as a mechanism leading to oscillation of the tail of the liquid jet near the breakup point.…”

Section: Introductionmentioning

confidence: 99%

Liquid jet breakup unsteadiness in a coaxial air-blast atomizer

Kumar

Sahu

2018

International Journal of Spray and Combustion Dynamics

View full text Add to dashboard Cite

The aim of this paper is to experimentally characterize the liquid jet breakup unsteadiness in a coaxial air-blast atomizer. The current research focuses on the measurement of the fluctuations of the jet breakup length and the flapping instability of the liquid jet, which contribute to the downstream fluctuations of the spray characteristics. The optical connectivity technique was used to measure the instantaneous breakup length of the water jet. Also, time resolved shadowgraph images of the primary jet breakup process were captured by high-speed imaging to characterize the jet instabilities at different axial locations from the atomizer exit. Experiments were performed for a wide range of air-to-liquid momentum flux ratio (M) and aerodynamic Weber number (We g) corresponding to membrane-and/or fiber breakup mode of the jet disintegration process. The mean jet breakup length was found to vary inversely with M through a power law relation in agreement with the literature, while the breakup length fluctuations were found to first decrease and then increase with M. In order to capture the unsteady dynamics of the jet breakup process, the proper orthogonal decomposition analysis of the optical connectivity images was performed. The jet flapping and the fluctuations of the jet breakup length were identified as the second and the third spatial proper orthogonal decomposition modes, respectively, for all operating conditions of the atomizer. The amplitude and the frequency of the instabilities were measured by temporal tracking of the liquid-air interface on the shadowgraph images. The disturbance close to the injector exit corresponds to the Kelvin-Helmholtz instability, while close to the jet breakup point the jet exhibits the flapping instability, which is characterized by lateral oscillation of the jet about the atomizer axis. The influence of the liquid jet Reynolds number and momentum flux ratio on the KH and the flapping instabilities are examined.

show abstract

Helical modes in combined Rayleigh–Taylor and Kelvin–Helmholtz instability of a cylindrical interface

Cited by 19 publications

References 32 publications

Shock-induced aerobreakup of a polymeric droplet

Shock-induced aerobreakup of a polymeric droplet

Effects of the initial perturbations on the Rayleigh-Taylor-Kelvin-Helmholtz instability system

Liquid jet breakup unsteadiness in a coaxial air-blast atomizer

Contact Info

Product

Resources

About