Droplet aerobreakup under the shear-induced entrainment regime using a multiscale two-fluid approach

Nykteri, Georgia; Gavaises, Manolis

doi:10.1103/physrevfluids.6.084304

Cited by 13 publications

(7 citation statements)

References 68 publications

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“…Note that the normal SW, and thus the post-shock air flow, moves in the positive z-axis direction. Furthermore, based on previous numerical simulations conducted for similar flow configurations [14], the spatial domain size is chosen such that −21 < z/d 0 < 26 and r/d 0 < 10, where d 0 stands for the initial diameter of the spherical droplet, which represents the natural reference length of the problem. The shock tube is divided into two parts by means of a virtual cross diaphragm, which is initially located at z/d 0 = −2 (upstream of the droplet).…”

Section: Case Studymentioning

confidence: 99%

“…From a numerical point of view, since the droplet aerobreakup under the SIE regime is characterized by a broad range of spatial and temporal scales, the accurate capture of the droplet deformation and fragmentation is particularly demanding in terms of computational power. Nevertheless, computational fluid dynamics (CFD) simulations have been effectively conducted to predict the early stages of the breakup process induced by the impact of a traveling SW. Due to the high computational cost of fully three-dimensional (3D) simulations, several numerical studies have dealt with two-dimensional shock/liquid column interactions [10][11][12][13][14]. In order to make them affordable, in the context of preliminary analyses, 3D computations have been most often conducted by neglecting the effects of molecular viscosity, while resolving the Euler equations [15,16].…”

Section: Introductionmentioning

confidence: 99%

“…The governing equations consist of two continuity equations for the two different phases, the mixture momentum and energy equations, and the volume fraction advection equation [16,18]. As far as turbulence modeling is concerned, either under-resolved direct numerical simulation (DNS) or large eddy simulation (LES) approaches are usually followed [6,14].…”

Section: Introductionmentioning

confidence: 99%

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Computational Evaluation of Shock Wave Interaction with a Liquid Droplet

2022

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This article represents the natural continuation of the work by Rossano and De Stefano (2021), dealing with the computational fluid dynamics analysis of a shock wave interaction with a liquid droplet. Differently from our previous work, where a two-dimensional approach was followed, fully three-dimensional computations are performed to predict the aerodynamic breakup of a spherical water body due to the impact of a traveling shock wave. The present engineering analysis focuses on capturing the early stages of the breakup process under the shear-induced entrainment regime. The unsteady Reynolds-averaged Navier–Stokes approach is used to simulate the mean turbulent flow field in a virtual shock tube device with circular cross section. The compressible-flow-governing equations are numerically solved by means of a finite volume method, where the volume of fluid technique is employed to track the air–water interface. The proposed computational modeling approach for industrial gas dynamics applications is verified by making a comparison with reference numerical data and experimental findings, achieving acceptably accurate predictions of deformation and drift of the water body without being computationally cumbersome.

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Section: Case Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Computational Evaluation of Shock Wave Interaction with a Liquid Droplet

2022

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“…Therefore, the sub-grid scale mechanisms that are considered for the local interface formation are the effects of turbulence, the sub-grid scale droplet collision and coalescence, and the secondary breakup. The appropriate closure relations for each mechanism are based on models that are validated in the literature for similar flow conditions; the implemented sub-grid scale models and their limitations are discussed in detail in [46].…”

Section: σ-υ Model Transport Equationsmentioning

confidence: 99%

Numerical modeling of droplet rim fragmentation by laser-pulse impact using a multiscale two-fluid approach

Nykteri

Gavaises

2022

Phys. Rev. Fluids

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The present work examines the rim fragmentation of a millimeter-sized methyl-ethyl-ketone (MEK) droplet imposed by the impact of different millijoule nanosecond laser beams that correspond to droplet propulsion velocity values between 1.76 m/s and 5.09 m/s. The numerical investigation is conducted within a physically consistent and computationally efficient multiscale framework, using the Σ-Υ two-fluid model with dynamic local topology detection. Overall, the macroscopic droplet expansion and the obtained deforming shape show good agreement with the experimental observations. The influence of the laser beam energy on the droplet deformation and the evolution of the detached fragments from the rim is demonstrated. The physical mechanisms that determine the droplet expansion, including the expansion velocity and expansion rate, along with the effect of the surrounding air flow on the detached fragments, are addressed. Despite the visualization limitations inside the polydisperse cloud of fragments in the experimental results at higher laser energy, the evolution of fragments during the fragmentation process is quantified for the first time, and size distributions are obtained within the multiscale framework.

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“…Dorschner et al (2020) pointed out that the time of primary breakup is related to the Weber number but the time interval between the secondary and third breakups is independent of the Weber number. Nykteri & Gavaises (2021) showed that the symmetrical recirculation zone near the droplet equator is the main reason for the flattening of the droplet profile in the early stage of deformation. The vorticity field and pressure field of the droplet explained the appearance and evolution of surface structure, demonstrating that pressure is the primary inducement for the formation of droplet protrusion (Meng & Colonius 2015).…”

Section: Introductionmentioning

confidence: 99%

On shock induced aerobreakup of a wall-attached droplet

Guo,

Kang,

et al. 2023

J. Fluid Mech.

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An experimental study on the aerobreakup of a wall-attached droplet induced by a shock wave is carried out in this work. The shock wave and the post-wave air stream are generated by a shock tube facility, and the dynamics of droplet breakup are captured through high-speed imaging from the side, the oblique front and the back views, respectively. The wall-attached droplets with different wettabilities are considered, including the hydrophobic, hemispherical and hydrophilic ones. For the convenience of analysis, droplets with different wettabilities are unified with the same equivalent radius and, thus, the same Weber number and Reynolds number. Different from the evolution of a free spherical droplet, it is observed that the hydrophobic droplet can develop ‘peak’ structures on the windward and leeward sides, respectively; while the hemispherical and hydrophilic droplets leave a liquid film on the wall. The occurrence of ‘peak’ structures is caused by the local standing vortex on the droplet windward and leeward sides, and the residual of a liquid film on a solid wall is related to the boundary layer near the wall. Through comparing the height, width and advancing distance of droplet deformation between the spherical droplet and the wall-attached droplets with different wettabilities, it is found that the wall will inhibit the deformation and fragmentation of droplets on the flow direction. The ‘peak’ and film structures are responsible for the deviation of the dimensionless width between spherical and wall-attached droplets. The ‘lip’ structure is related to the recirculation flow at the rear of the droplet, which causes the reverse of velocity on the surface. The radius of the ‘lip’ decreases with the decrease of contact angle. The Rayleigh–Taylor (R–T) and Kelvin–Helmholtz (K–H) instabilities of wall-attached and spherical droplets are also studied by experiments and theoretical analysis. With the decrease of contact angle, the development of the K–H instability hardly changes, while the R–T instability results in a smaller wavelength of perturbation on the windward side. This study is expected to give some guidance for regulating the aerodynamic fragmentation of droplets in engineering applications.

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Droplet aerobreakup under the shear-induced entrainment regime using a multiscale two-fluid approach

Cited by 13 publications

References 68 publications

Computational Evaluation of Shock Wave Interaction with a Liquid Droplet

Computational Evaluation of Shock Wave Interaction with a Liquid Droplet

Numerical modeling of droplet rim fragmentation by laser-pulse impact using a multiscale two-fluid approach

On shock induced aerobreakup of a wall-attached droplet

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