Li, Qing and Abbas, Micheline and Morris, Jeffrey F. and Climent, Éric and Magnaudet, Jacques Nearwall dynamics of a neutrally buoyant spherical particle in an axisymmetric stagnation point flow. (2020) Journal of Fluid Mechanics, 892. A32. ISSN 00221120

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Official URL: https://doi.org/10.1017/jfm.2020.185
Abstract
The motion of a neutrally buoyant spherical particle along the axis of an axisymmetric stagnation point flow at a rigid and smooth flat wall (Hiemenz–Homann flow) is investigated in the presence of lowtomoderate inertia effects. The particle dynamics is elucidated using numerical simulation. At distances large compared to the characteristic thickness of the boundary layer \delta=(\nu/B)^{1/2}, with \nu the kinematic viscosity and B the strain rate of the carrying flow, the particle decelerates as it approaches the wall, due to the ambient pressure increase toward the stagnation point. In this part of the path, its velocity is nearly identical to that of the local undisturbed fluid at the position of its centre. Relative motion between the particle and fluid increases as the wall–particle gap reduces, due to wallinduced hydrodynamic interaction forces. Two distinct evolutions of the net force on the particle are observed, depending on the relative particle size, a/\delta=Re^{1/2}, where a is the particle radius and Re=2Ba^2/\nu is the Reynolds number. For a/\delta=2, the force decays monotonically to zero, while it undergoes a sharp rise before returning to zero for larger particles. In the latter case, the particle retains a sufficient velocity even for very small gap widths such that, under usual roughness levels, a rebounding collision would occur. The stress profiles at the particle surface are investigated to separate the various contributions to the hydrodynamic force. Theoretical predictions for nearwall viscous and inertial forces available in the creepingflow and lowbutfinite Reynoldsnumber limits, respectively, are used to pinpoint the origin of the dominant inertia effect that controls the particle dynamics when the particle gets very close to the wall.
Item Type:  Article 

HAL Id:  hal02735362 
Audience (journal):  International peerreviewed journal 
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Institution:  French research institutions > Centre National de la Recherche Scientifique  CNRS (FRANCE) Université de Toulouse > Institut National Polytechnique de Toulouse  Toulouse INP (FRANCE) Université de Toulouse > Institut National des Sciences Appliquées de Toulouse  INSA (FRANCE) Université de Toulouse > Université Toulouse III  Paul Sabatier  UT3 (FRANCE) Other partners > City University of NewYork  CUNY (USA) 
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Funders:  IDEXUNITI Toulouse 
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Deposited On:  08 Apr 2020 13:59 
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