This study is devoted to the investigation, by means of direct numerical simulation, of the interaction between turbulent motions and the pseudo-boiling process. To this end, fully resolved data of a transcritical nitrogen jet are used, obtained via high order methods and using detailed thermodynamic and transport properties. A laminar pseudo-boiling process is simulated in a quiescent setting and used as a consistent reference to shed light on the mutual effects of the jet evolution and thermodynamic non-linearities. In the turbulent scenario, pseudo-boiling is shown to be faster, in an average sense, to the laminar reference case. A consistent definition of the pseudo-boiling rate, based on the concept of the displacement speed, commonly used in premixed flame propagation, is introduced and, for a better physical interpretation, split into a normal diffusion component and a curvature component. The pseudo-boiling rate is statistically analyzed to evaluate the rate of mass transfer from the liquid-like state to the gas-like state during the jet evolution. Normal diffusion is found to be the dominant component of the pseudo-boiling rate, while the curvature component is shown to have a role only when warm fluid pockets are deeply entrained in the jet cold core.

Characterization of pseudo-boiling in a transcritical nitrogen jet / Lapenna, Pasquale Eduardo. - In: PHYSICS OF FLUIDS. - ISSN 1070-6631. - 30:7(2018). [10.1063/1.5038674]

Characterization of pseudo-boiling in a transcritical nitrogen jet

Lapenna, Pasquale Eduardo
Primo
2018

Abstract

This study is devoted to the investigation, by means of direct numerical simulation, of the interaction between turbulent motions and the pseudo-boiling process. To this end, fully resolved data of a transcritical nitrogen jet are used, obtained via high order methods and using detailed thermodynamic and transport properties. A laminar pseudo-boiling process is simulated in a quiescent setting and used as a consistent reference to shed light on the mutual effects of the jet evolution and thermodynamic non-linearities. In the turbulent scenario, pseudo-boiling is shown to be faster, in an average sense, to the laminar reference case. A consistent definition of the pseudo-boiling rate, based on the concept of the displacement speed, commonly used in premixed flame propagation, is introduced and, for a better physical interpretation, split into a normal diffusion component and a curvature component. The pseudo-boiling rate is statistically analyzed to evaluate the rate of mass transfer from the liquid-like state to the gas-like state during the jet evolution. Normal diffusion is found to be the dominant component of the pseudo-boiling rate, while the curvature component is shown to have a role only when warm fluid pockets are deeply entrained in the jet cold core.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11573/1151465
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