Receptivity to forcing disturbances in subcritical liquid sheet flows

Pia, Alessandro Della; Chiatto, Matteo; Luca, Luigi De

doi:10.1063/5.0044322

Cited by 14 publications

(10 citation statements)

References 28 publications

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“…Note also that the harmonically forcing transverse velocity represented by is analogous to that adopted by Schmidt & Oberleithner (2020) and Della Pia et al. (2021) in two-dimensional viscous nonlinear simulations, while Torsey et al. (2021) considered sinusoidal ambient pressure perturbations.…”

Section: Theoretical and Numerical Modellingmentioning

confidence: 98%

“…Both the natural and forced responses of a gravitational liquid sheet, interacting with an unconfined gaseous ambient, are analysed by means of a linear inviscid one-dimensional model, described in detail in previous contributions (Della Pia et al. 2020, 2021). Despite the simplifying assumptions, the predictions of this model were found to be valuable compared with two-phase numerical simulations carried out with a volume-of-fluid (VOF) code (Popinet 2003, 2009).…”

Section: Theoretical and Numerical Modellingmentioning

confidence: 99%

“…The eigenvalues equation becomes singular, and the condition removing this singularity constitutes the required second boundary condition (Della Pia et al. 2021) where , and is the critical station, i.e. the location where the local Weber number is equal to unity The role of the critical station in the selection mechanism of the global mode (i.e.…”

Section: Theoretical and Numerical Modellingmentioning

confidence: 99%

“…2018; Kitsikoudis et al. 2021) and unconfined gaseous ambient (Schmidt & Oberleithner 2020; Della Pia, Chiatto & de Luca 2021; Torsey et al. 2021), both in supercritical () and subcritical () regimes.…”

Section: Introductionmentioning

confidence: 99%

“…Focusing on the flow transition from the supercritical to subcritical regime, the recent numerical investigation by Della Pia et al. (2021), who provided a simplified one-dimensional model of the dynamics of a sheet of finite length accounting for the coupling between the curtain motion and the surrounding gaseous environment, highlighted the discontinuity (jump) of the flow natural frequency when the Weber number reduces below the critical threshold . On the other hand, Torsey et al.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Natural frequency discontinuity of vertical liquid sheet flows at transcritical threshold

Chiatto

Pia

2022

J. Fluid Mech.

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The natural and forced dynamic response of a gravitational plane liquid sheet (curtain) of finite length interacting with an unconfined gaseous ambient is numerically and experimentally investigated. The global eigenvalue spectrum obtained by means of a linear inviscid one-dimensional model, accounting for the coupling between the curtain motion and the ambient pressure disturbances, clearly shows an abrupt increase (jump) in the characteristic natural frequency of the flow when the supercritical ( $We>1$ ) to subcritical ( $We<1$ ) transition occurs, with the Weber number $We$ defined as the ratio between inertia and capillary forces. On the other hand, the numerical simulation of the forced sheet response does not show any discontinuity between supercritical and subcritical conditions, as recently found by Torsey et al. (J. Fluid Mech., vol. 910, 2021, pp. 1–14) in the case of an infinite liquid sheet subjected to imposed ambient pressure disturbances not coupled with the curtain motion. It is argued that the forced liquid sheet behaviour varies continuously in shape and amplitude between the two regimes, not depending on the specific liquid–gas interaction model considered, whilst the natural frequency of the finite flow system does undergo a discontinuity, which can be theoretically predicted by the model of sheet–ambient interaction employed here. As a major result, the experimental evidence of the natural frequency jump is for the first time provided as well.

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Section: Theoretical and Numerical Modellingmentioning

confidence: 98%

Section: Theoretical and Numerical Modellingmentioning

confidence: 99%

Section: Theoretical and Numerical Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Natural frequency discontinuity of vertical liquid sheet flows at transcritical threshold

Chiatto

Pia

2022

J. Fluid Mech.

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On the shapes of liquid curtains flowing from a non-vertical slot

Della Pia,

Antoniades,

Ioannidis

et al. 2023

J. Fluid Mech.

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A theoretical and experimental investigation of two-dimensional (2-D) liquid curtains (gravitationally thinning liquid sheets) is provided under conditions where the curtain issues from a thin slot whose centreline is inclined with respect to the vertical. This analysis is motivated in part by recent works where it has been proposed that oblique liquid curtains (those exiting a non-vertical slot) may bend upwards against gravity when the relevant Weber number at the slot is less than unity ( $We <1$ ). By contrast, Weinstein et al. (J. Fluid Mech., vol. 876, 2019, R3) have proposed that such $We<1$ curtains must be vertical and downward falling regardless of the inclination of the slot. Under low-Reynolds-number ( $Re$ ) conditions typical of liquid film coating operations, our experiments show that the curtain shape follows the classic ballistic (parabolic) trajectory in the supercritical regime ( $We>1$ ). In subcritical conditions ( $We<1$ ), experiments show that the downward-falling curtain is vertical except in a relatively small region near the slot, where the combined effects of viscosity and surface tension induce the so-called teapot effect. These experimental results are confirmed by 2-D numerical simulations, which predict the curtain behaviour ranging from highly viscous ( $Re = O(1)$ ) to nearly inviscid conditions. The one-dimensional (1-D) inviscid model of Weinstein et al. is recast in a different form to facilitate comparisons with the 2-D model, and 1-D and 2-D results agree favourably for supercritical and subcritical conditions. Despite the large parameter range explored, we have found no evidence that upward-bending curtains exist in an oblique configuration.

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Spatio-temporal dynamics and disintegration of a fan liquid sheet

et al. 2021

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The dynamic behavior and disintegration mechanisms of a fan liquid sheet in a quiescent atmosphere are investigated over a broad range of differential injection pressures up to Δp≈70 bar through experiments, proper orthogonal decomposition (POD) and spectral analyses, and linear stability analysis (LSA). By fan liquid sheet, we mean a diverging and attenuating liquid stream emanating from a flat fan nozzle with high velocity. High spatiotemporal resolution backlit images reveal the formation-growth-fragmentation process of bag-like structures along the fan liquid sheets, which we predict to be responsible for the overall breakup of the sheets through a mechanism known as “wavy corridor.” Therefore, we propose a conjugate model based on LSA to take into account the role of different shear and surface tension-driven instabilities in defining the liquid sheet intact radius and primary droplet sizes. The predictions of LSA from the dynamic features of the liquid sheets, which mainly depend on the sheet Weber number We, are consistent with the quantitative results obtained from the POD and spectral analyses of the images. While the Strouhal number St and the intact radius R of the fan liquid sheets reduce like We−1/3 with increasing We, the volume median diameter of primary droplets decreases like We−11/12. An image feature consolidation technique along with a machine-learning technique, receiver operating characteristic curve analysis, was used to estimate the mean diameter of spray droplets with a large range of sizes.

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Receptivity to forcing disturbances in subcritical liquid sheet flows

Cited by 14 publications

References 28 publications

Natural frequency discontinuity of vertical liquid sheet flows at transcritical threshold

Natural frequency discontinuity of vertical liquid sheet flows at transcritical threshold

On the shapes of liquid curtains flowing from a non-vertical slot

Spatio-temporal dynamics and disintegration of a fan liquid sheet

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