Viscoacoustic squeeze-film force on a rigid disk undergoing small axial oscillations

Ramanarayanan, S.; Coenen, Wilfried; Sánchez Pérez, Antonio Luis

Publication:
Viscoacoustic squeeze-film force on a rigid disk undergoing small axial oscillations

dc.affiliation.dpto	UC3M. Departamento de Ingeniería Térmica y de Fluidos	es
dc.affiliation.grupoinv	UC3M. Grupo de Investigación: Mecánica de Fluidos	es
dc.contributor.author	Ramanarayanan, S.
dc.contributor.author	Coenen, Wilfried
dc.contributor.author	Sánchez Pérez, Antonio Luis
dc.date.accessioned	2023-01-25T08:57:58Z
dc.date.available	2023-01-25T08:57:58Z
dc.date.issued	2022-02-25
dc.description.abstract	This paper investigates the air flow induced by a rigid circular disk or piston vibrating harmonically along its axis of symmetry in the immediate vicinity of a parallel surface. Previous attempts to characterize these so-called 'squeeze-film' systems largely relied on simplifications afforded by neglecting either fluid acceleration or viscous forces inside the thin enclosed gas layer. The present viscoacoustic analysis employs the asymptotic limit of small vibration amplitudes to investigate the flow by systematic reduction of the Navier-Stokes equations in two distinct flow regions, namely, the inner gaseous film where streamlines are nearly parallel to the confining walls and the near-edge region of non-slender flow that features gas exchange with the surrounding stagnant atmosphere. The flow in the gaseous film depends on the relevant Stokes number, defined as the ratio of the characteristic viscous time across the film to the characteristic oscillation time, and on a compressibility parameter, defined as the square of the ratio of the acoustic time for radial pressure equilibration to the oscillation time. A Strouhal number based on the local residence time emerges as an additional governing parameter for the near-edge region, which is incompressible at leading order. The method of matched asymptotic expansions is used to describe the solution in both regions, across which the time-averaged pressure exhibits comparable variations that give opposing contributions to the resulting time-averaged force experienced by the disk or piston. A diagram structured with the Stokes number and compressibility parameter as coordinates reveals that this steady squeeze-film force, typically repulsive for small values of the Stokes number, alternates to attraction across a critical separation contour in the parametric domain that exists for all Strouhal numbers. This analysis provides, for the first time, a unifying viscoacoustic theory of axisymmetric squeeze films, which yields a reduced parametric description for the time-averaged repulsion/attraction force that is potentially useful in applications including non-contact fluid bearings and robot locomotion.	en
dc.format.extent	33
dc.identifier.bibliographicCitation	Ramanarayanan, S., Coenen, W. & Sánchez, A. (2021). Viscoacoustic squeeze-film force on a rigid disk undergoing small axial oscillations. Journal of Fluid Mechanics, 933.	en
dc.identifier.doi	https://doi.org/10.1017/jfm.2021.1072
dc.identifier.issn	0022-1120
dc.identifier.publicationfirstpage	A15-1
dc.identifier.publicationlastpage	A15-33
dc.identifier.publicationtitle	Journal of Fluid Mechanics	en
dc.identifier.publicationvolume	933
dc.identifier.uri	https://hdl.handle.net/10016/36357
dc.identifier.uxxi	AR/0000031165
dc.language.iso	eng	en
dc.publisher	Cambridge University Press	en
dc.rights	© The Author(s), 2021. Published by Cambridge University Press	en
dc.rights	Atribución 3.0 España	*
dc.rights.accessRights	open access	en
dc.rights.uri	http://creativecommons.org/licenses/by/3.0/es/	*
dc.subject.eciencia	Física	es
dc.subject.eciencia	Ingeniería Mecánica	es
dc.subject.other	General fuid mechanics	en
dc.subject.other	Lubrication theory	en
dc.title	Viscoacoustic squeeze-film force on a rigid disk undergoing small axial oscillations	en
dc.type	research article	*
dc.type.hasVersion	VoR	*
dspace.entity.type	Publication