Numerical Investigation of the Aerodynamic Droplet Breakup at Mach Numbers Greater Than 1

Stefanitsis, Dionisis; Koukouvinis, Phoevos; Νikolopoulos, Nikos; Gavaises, Manolis

doi:10.1061/(asce)ey.1943-7897.0000720

Cited by 15 publications

(7 citation statements)

References 61 publications

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“…A two phase numerical set up, similar to the present work, employed in the work of Stefanitsis et. al [40] was shown to have a good agreement with simulation results of Meng et. al [9].…”

Section: Two Phase Simulationsupporting

confidence: 71%

“…2b, computational domain dimensions are expressed as a product of droplet diameter, D d . Similar to the single phase flow, block meshing was employed, wherein a region of 4D d length and 2D d height around the droplet was uniformly meshed with cell density of 100 cells per diameter, similar to the grid density reported in the work of Stefnitsis [40] and Meng et. al [9], while progressively coarsening the mesh approaching the pressure outlet boundaries.The results reported in the present work are based on the simulations conducted on a computational mesh with ∼350,000 orthogonal elements.…”

Section: Two Phase Simulationmentioning

confidence: 99%

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Single and two-phase fluid droplet breakup in impulsively generated high-speed flow

Leung¹,

Gurunadhan²,

Menon³

2022

Preprint

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Aerobreakup of fluid droplets under the influence of impulsively generated high-speed gas flow using an open-ended shock tube is studied using experiments and numerical simulations. Breakup of mm-sized droplets at high Weber number was analyzed for water and two-phase nanofluids consisting of dispersions of Al2O3 and TiO2 nanoparticles in water with high loading of 20 and 40 weight% respectively. Droplet breakup is visualized using high-speed imaging in the experimental setup, where an open ended shock tube generates impulsive high-speed flow impinging on a droplet held stationary using an acoustic levitator. Axisymmetric simulations using the Volume of Fluid technique are conducted to capture the gas dynamics of the flowfield and droplet deformation at the initial stages. Fluid droplets are subject to a transient flow field generated by the open ended shock tube, characterized by a propagating incident shock wave, a recirculating vortex ring, and standing shock cells. Droplet breakup for all fluids proceeds through an initial flattening of the droplet followed by generation of a liquid sheet at the periphery in the presence of a curved, detached shock front at the leading edge. The breakup appears to follow a sheet stripping process whereby stretched ligaments undergo secondary atomization through viscous shear. Mist generated in the wake of the droplet appears to expand laterally due to the unconstrained expansion of the high-speed gas jet. The breakup morphology of droplets for all fluids appears consistent with previous observations using conventional shock tubes. Lateral deformation of the coherent droplet mass is observed to be higher for nanofluids as compared to water. This is attributed to higher viscosity and Ohnesorge number of

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“…A two phase numerical set up, similar to the present work, employed in the work of Stefanitsis et. al [40] was shown to have a good agreement with simulation results of Meng et. al [9].…”

Section: Two Phase Simulationsupporting

confidence: 71%

Section: Two Phase Simulationmentioning

confidence: 99%

Single and two-phase fluid droplet breakup in impulsively generated high-speed flow

Leung¹,

Gurunadhan²,

Menon³

2022

Preprint

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show abstract

“…From a numerical point of view, since the droplet aerobreakup under the SIE regime is characterized by a very broad range of spatial and temporal scales, the accurate prediction of the droplet deformation and fragmentation is particularly demanding in terms of computing power. Due to the high computational cost of fully three-dimensional (3D) simulations, several CFD studies have been conducted in two spatial dimensions, by considering that the shear-induced breakup of a cylindrical liquid column [10][11][12]. Twodimensional simulations have been mostly focused on the early stages of the breakup process, without investigating the droplet fragmentation and the subsequent mist development [13,14].…”

Section: Introductionmentioning

confidence: 99%

Hybrid VOF–Lagrangian CFD Modeling of Droplet Aerobreakup

Rossano

Stefano

2022

Applied Sciences

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A hybrid VOF–Lagrangian method for simulating the aerodynamic breakup of liquid droplets induced by a traveling shock wave is proposed and tested. The droplet deformation and fragmentation, together with the subsequent mist development, are predicted by using a fully three-dimensional computational fluid dynamics model following the unsteady Reynolds-averaged Navier–Stokes approach. The main characteristics of the aerobreakup process under the shear-induced entrainment regime are effectively reproduced by employing the scale-adaptive simulation method for unsteady turbulent flows. The hybrid two-phase method combines the volume-of-fluid technique for tracking the transient gas–liquid interface on the finite volume grid and the discrete phase model for following the dynamics of the smallest liquid fragments. The proposed computational approach for fluids engineering applications is demonstrated by making a comparison with reference experiments and high-fidelity numerical simulations, achieving acceptably accurate results without being computationally expensive.

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“…However, due to the significant computational cost, these DNS studies are restricted to the demonstration of the early-stage instabilities on the coherent droplet surface and do not examine the later-stage fragmentation and mist development, which is the main objective of the current simulations. On the contrary, the utilized spatial resolution of 100 and 200 cells per original diameter is commonly selected in the literature, for instance in the simulations of [26], [42], [44], [47], and is proven to capture accurately the macroscopic deformation of the coherent droplet surface, while the investigation of the Kelvin-Helmholtz instabilities remains out of scope in the present study.…”

Section: B Problem Definition and Simulation Setupmentioning

confidence: 99%

“…Liu et al [43] conducted both axisymmetric and three-dimensional simulations to examine the aerobreakup mechanism under supersonic conditions and identified significant details of the liquid stripping and the vortices development at the early stages of aerobreakup. In an attempt to investigate water dispersion, Stefanitsis et al [44] proposed a coupled VOF/Lagrangian approach to simulate the coherent droplet and the produced droplets cloud, respectively. The obtained results predict the detachment of microscale droplets from the coherent droplet periphery, as depicted in the experimental visualizations of Theofanous et al [22] with, however, a lack of physical input for the sizes of the produced Lagrangian particles.…”

Section: Introductionmentioning

confidence: 99%

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

Nykteri

Gavaises

2021

Phys. Rev. Fluids

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A droplet exposed to a high-speed gas flow is subject to a rapid and violent fragmentation, dominated by a widespread mist of multiscale structures that introduce significant complexities in numerical studies. The present work focuses on capturing all stages of the aerodynamic breakup of a waterlike droplet imposed by three different intensity shock waves, with Mach numbers of 1.21, 1.46, and 2.64, under the shear-induced entrainment regime. 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 breakup of the deforming droplet and the subsequent dispersion of the produced mist show good agreement with available experimental studies in the literature. The major features and physical mechanisms of breakup, including the incident shock wave dynamics and the vortices development, are discussed, and verified against the experiments and the theory. While the experimental visualizations inside the dense mist are restricted by the capabilities of the diagnostic methods, the multiscale two-fluid approach provides insight into the mist dynamics and the distribution of the secondary droplets under different postshock conditions.

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Numerical Investigation of the Aerodynamic Droplet Breakup at Mach Numbers Greater Than 1

Cited by 15 publications

References 61 publications

Single and two-phase fluid droplet breakup in impulsively generated high-speed flow

Single and two-phase fluid droplet breakup in impulsively generated high-speed flow

Hybrid VOF–Lagrangian CFD Modeling of Droplet Aerobreakup

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

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