Selection of solitary waves in vertically falling liquid films

Kofman, Nicolas; Ruyer-Quil, Christian; Mergui, Sophie

doi:10.1016/j.ijmultiphaseflow.2016.04.006

Cited by 8 publications

(3 citation statements)

References 29 publications

(44 reference statements)

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“…Building upon this observation, forcing the formation of rivulets is advantageous if one wishes to accelerate the drainage. Similar effects exist when waves run down at the surface of a liquid film flowing down an inclined plane (Kofman et al 2016). Such a modification of the mean flow is also a key to the saturation of hydrodynamic instabilities like the vortex shedding in the wake flow behind a cylinder (Maurel et al 1995;Mantič-Lugo et al 2014).…”

Section: Nonlinear Simulations At the Top Of The Cylindermentioning

confidence: 83%

Three-dimensional Rayleigh–Taylor instability under a unidirectional curved substrate

et al. 2017

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We investigate the Rayleigh–Taylor instability of a thin liquid film coated on the inside of a cylinder whose axis is orthogonal to gravity. We are interested in the effects of geometry on the instability, and contrast our results with the classical case of a thin film coated under a flat substrate. In our problem, gravity is the destabilizing force at the origin of the instability, but also yields the progressive drainage and stretching of the coating along the cylinder’s wall. We find that this flow stabilizes the film, which is asymptotically stable to infinitesimal perturbations. However, the short-time algebraic growth that these perturbations can achieve promotes the formation of different patterns, whose nature depends on the Bond number that prescribes the relative magnitude of gravity and capillary forces. Our experiments indicate that a transverse instability arises and persists over time for moderate Bond numbers. The liquid accumulates in equally spaced rivulets whose dominant wavelength corresponds to the most amplified mode of the classical Rayleigh–Taylor instability. The formation of rivulets allows for a faster drainage of the liquid from top to bottom when compared to a uniform drainage. For higher Bond numbers, a two-dimensional stretched lattice of droplets is found to form on the top part of the cylinder. Rivulets and the lattice of droplets are inherently three-dimensional phenomena and therefore require a careful three-dimensional analysis. We found that the transition between the two types of pattern may be rationalized by a linear optimal transient growth analysis and nonlinear numerical simulations.

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Section: Nonlinear Simulations At the Top Of The Cylindermentioning

confidence: 83%

Three-dimensional Rayleigh–Taylor instability under a unidirectional curved substrate

et al. 2017

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“…Inlet operating conditions for both heat exchangers are selected according to the operating conditions of a 5 kW cold production absorption chiller prototype [16]. In counter-current configurations, besides modifying (𝛿) , (𝜏 𝑖 ) can increase the amplitude of surface waves at the liquidvapor interface [9]. Flooding appears when these waves may obstruct the vapor flow and lead to the entrainment of liquid in the vapor flow.…”

Section: 𝜕𝑃 𝜕𝑥mentioning

confidence: 99%

“…Conversely, in counter-current flow, it leads to an increase in the average film thickness [7]. Regarding interfacial waves, high vapor Reynolds numbers tend to decrease their amplitude in co-current flow [8] while in counter-current flows, they lead to an increase [9], contributing to the flooding phenomenon [10].…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of a confined falling liquid film sheared by a gas flow in a plate heat exchanger of an NH₃/H₂0 absorption chiller

Sleiman,

Collignon,

Phan

et al. 2024

J. Phys.: Conf. Ser.

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In recent years, the demand for cooling has seen a substantial increase, primarily due to rising summertime temperatures. Conventional mechanical compression air conditioners have played a predominant role in fulfilling this demand, albeit at the cost of significant electricity consumption. In response, absorption chillers have emerged as an eco-friendly alternative, powered by sustainable heat sources like solar energy or industrial waste heat. The present work is conducted within the framework of developing compact absorption chillers incorporating plate heat exchangers. It builds upon prior research by improving an existing numerical model for falling film plate heat exchangers within an NH3/H2O absorption chiller. This former numerical model evaluates the coupled heat and mass transfer between the liquid film and the vapor flow while excluding hydrodynamic interactions at the liquid-vapor interface. The current investigation aims to address compactness and cost-efficiency limitations in absorption chillers. The consequences of operation within confined spaces were numerically evaluated. An innovative analytical model was developed to quantify the influence of the interactions at the liquid-vapor interface. Shear stress and interfacial perturbations were considered compared to the classical Nusselt model, enabling the evaluation of the changes in the average film thickness and the flooding phenomenon. This analytical model was then added to the previously developed heat and mass transfer model. The numerical model was applied to both the desorber and absorber units. The results show that increased confinement has minimal effects on the transfer coefficients. Additionally, an approach is suggested for estimating flooding in confined spaces and the results are compared with various correlations available in the literature.

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Evolution mechanism of solitary waves on the inviscid film flow under an electrostatic field

et al. 2018

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Selection of solitary waves in vertically falling liquid films

Cited by 8 publications

References 29 publications

Three-dimensional Rayleigh–Taylor instability under a unidirectional curved substrate

Three-dimensional Rayleigh–Taylor instability under a unidirectional curved substrate

Numerical modeling of a confined falling liquid film sheared by a gas flow in a plate heat exchanger of an NH₃/H₂0 absorption chiller

Evolution mechanism of solitary waves on the inviscid film flow under an electrostatic field

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Selection of solitary waves in vertically falling liquid films

Cited by 8 publications

References 29 publications

Three-dimensional Rayleigh–Taylor instability under a unidirectional curved substrate

Three-dimensional Rayleigh–Taylor instability under a unidirectional curved substrate

Numerical modeling of a confined falling liquid film sheared by a gas flow in a plate heat exchanger of an NH3/H20 absorption chiller

Evolution mechanism of solitary waves on the inviscid film flow under an electrostatic field

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Numerical modeling of a confined falling liquid film sheared by a gas flow in a plate heat exchanger of an NH₃/H₂0 absorption chiller