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Hele-Shaw flow

About: Hele-Shaw flow is a research topic. Over the lifetime, 5451 publications have been published within this topic receiving 151320 citations.


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Journal ArticleDOI
TL;DR: In this article, the authors performed laser-Doppler velocity measurements adjacent to the bounding walls of 3D backward-facing step flow for the purpose of mapping the boundaries of the reverse flow regions that develop in this geometry (adjacent to the sidewalls, the flat wall and the stepped wall) as a function of the Reynolds number.

87 citations

Journal ArticleDOI
TL;DR: In this article, an inclined chute facility and its associated diagnostics has been developed and utilized to study the flow of granular materials and a variety of flow regimes and flow phenomena were observed.

87 citations

Journal ArticleDOI
TL;DR: In this article, the presence of finite-size particles in a channel flow close to the laminar-turbulent transition is simulated with the force coupling method which allows two-way coupling with the flow dynamics.
Abstract: The presence of finite-size particles in a channel flow close to the laminar-turbulent transition is simulated with the Force Coupling Method which allows two-way coupling with the flow dynamics. Spherical particles with channel height-to-particle diameter ratio of 16 are initially randomly seeded in a fluctuating flow above the critical Reynolds number corresponding to single phase flow relaminarization. When steady-state is reached, the particle volume fraction is homogeneously distributed in the channel cross-section (ϕ ≅ 5%) except in the near-wall region where it is larger due to inertia-driven migration. Turbulence statistics (intensity of velocity fluctuations, small-scale vortical structures, wall shear stress) calculated in the fully coupled two-phase flow simulations are compared to single-phase flow data in the transition regime. It is observed that particles increase the transverse r.m.s. flow velocity fluctuations and they break down the flow coherent structures into smaller, more numerous and sustained eddies, preventing the flow to relaminarize at the single-phase critical Reynolds number. When the Reynolds number is further decreased and the suspension flow becomes laminar, the wall friction coefficient recovers the evolution of the laminar single-phase law provided that the suspension viscosity is used in the Reynolds number definition. The residual velocity fluctuations in the suspension correspond to a regime of particulate shear-induced agitation.

87 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that the force on a plate held perpendicular to a stream of velocity U is 8πμCU, μ being the viscosity of the fluid and C the electrical capacity of a conductor of the same shape as the plate.
Abstract: In certain cases of slow viscous flow round thin plates the solution of Stokes equations can be reduced to a solution of Laplace's equation with simple boundary conditions, the flow being thus relatable to the potential distribution in an electrostatic position. It is shown that the force on a plate held perpendicular to a stream of velocity U is 8πμCU, μ, being the viscosity of the fluid and C the electrical capacity of a conductor of the same shape as the plate. The rate of flow of fluid through an elliptic aperture in a thin w-all is shown to be 2S2/3πμs times the pressure difference between the two sides, S being the area of the aperture and s its perimeter. A simple expression is also derived for the torque on an elliptic plate rotating about its minor axis. Approximate methods for dealing with the flow past plates of complicated shapes are described, and the case of a paddle-type viscometer is treated as an example.

86 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of lung rhythmical expansion on gas mixing and aerosol dispersion and deposition can be studied using a fluid-mechanical model for an alveolated respiratory unit.
Abstract: Alternating shear flow over a self-similar, rhythmically expanding hemispherical depression is investigated. It provides a fluid-mechanical model for an alveolated respiratory unit, by means of which the effect of lung rhythmical expansion on gas mixing as well as aerosol dispersion and deposition can be studied. The flow is assumed to be very slow and governed by the quasi-steady linear Stokes equations. Consequently, superposition of the following two cases provides an easy route toward characterizing the aforementioned flow field. The first case treats the flow field that is generated by a rhythmically expanding spherical cap (the alveolus). The cap is attached at its rim to a circular opening in an expanding unbounded plane bounding a semi-infinite fluid region. The rate of expansion of the cap and the plane are chosen such as to maintain the system's configurational self-similarity. The second case addresses the flow disturbance that is generated by an alternating shear flow encountering a rigid hemispherical cavity in a plane bounding a semi-infinite fluid domain. For the first case, a stream-function representation employing toroidal coordinates furnishes an analytical solution, whereas the second case was solved numerically by Pozrikidis (1994). Linear superposition of the two flow cases results in particularly rich streamline maps. In the symmetry plane (bisecting the cap and parallel to the mean shear flow), for a certain range of shear to expansion-rate ratios, the streamline maps are self-similar and display closed orbits and two internal stagnation points. One of the stagnation points is a'centre' surrounded by closed streamlines whereas the other constitutes a 'saddle point'. For other planes, no stagnation points exist in the field, but the streamlines associated with the saddle point display complex looping patterns. These unique flow structures, when subjected to a small perturbation (e.g. a small asynchrony between ductal and alveolar entering flows) cause highly complex stochastic particle trajectories even in the quasi-static Stokes alveolar flow. The observed irreversible flow phenomena in a rhythmically expanding alveolus may be partially responsible for the 'stretch-and-fold' flow mixing patterns found in our recent flow visualization studies performed in excised animal lung acini.

86 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202339
202282
202120
202013
20199
201829