Journal ArticleDOI
Unsteady flow about a sphere at low to moderate Reynolds number. Part 2. Accelerated motion
Eugene J. Chang,Martin R. Maxey +1 more
TLDR
In this paper, a full numerical simulation based on spectral methods is used to investigate linearly accelerating and decelerating flows past a rigid sphere, and the authors find that the viscous force on the sphere decays in a power law manner after acceleration or deceleration ends, followed by rapid convergence at later times to the steady state.Abstract:
A full numerical simulation based on spectral methods is used to investigate linearly accelerating and decelerating flows past a rigid sphere. Although flow separation does not occur at Reynolds numbers below 20 for a steady flow, in the linearly decelerating flow separation is observed at much lower Reynolds numbers with complete detachment of vorticity possible in certain cases. The existence of a large recirculation region contributes to the result that a negative viscous force on the sphere is possible. The contribution of the pressure to the force includes a component that is well described by the inviscid added-mass term in both the accelerating and decelerating cases. The force on the sphere is found in general to initially decay in a power law manner after acceleration or deceleration ends followed by rapid convergence at later times to the steady state. For the cases examined this convergence is found to be exponential except for those in which the sphere is brought to rest in which case the convergence remains algebraic. This includes the special case of an infinite acceleration or deceleration where the free stream velocity is impulsively changed.read more
Citations
More filters
Journal ArticleDOI
The Motion of High-Reynolds-Number Bubbles in Inhomogeneous Flows
Jacques Magnaudet,Ian Eames +1 more
TL;DR: In this article, a trident approach consisting of experimental, analytical, and numerical work has given a clearer description of the hydrodynamic forces experienced by isolated bubbles moving either in inviscid flows or in slightly viscous laminar flows, and a significant part of the paper is devoted to a discussion of drag, added mass force, and shear-induced lift experienced by spheroidal bubbles moving in inertially dominated, time-dependent, rotational, nonuniform flows.
Journal ArticleDOI
The lift force on a spherical bubble in a viscous linear shear flow
TL;DR: In this paper, the authors studied the lift force experienced by a spherical bubble moving steadily in a viscous linear shear flow and provided a complete description of the lift forces experienced by the bubble and of the mechanisms responsible for this force over a wide range of Reynolds number (0.1[les]Re[les ]500, Re being based on the bubble diameter) and shear rate.
Journal ArticleDOI
Inertial effects in suspension and porous-media flows
Donald L. Koch,Reghan J. Hill +1 more
TL;DR: In this paper, the authors review recent applications of computational fluid dynamics to simulate the motion in particle suspensions with both inertia and vorticity in the continueous phase, and discuss two special cases of inertial suspensions, for which detailed kinetic theories have been developed.
Journal ArticleDOI
Velocity fidelity of flow tracer particles
TL;DR: In this paper, a simple, unified method for estimating the cut-off frequency, or cutoff size, of a solid particle or a contaminated micro-bubble in gas or liquid flow is developed.
Journal ArticleDOI
Bubble friction drag reduction in a high-Reynolds-number flat-plate turbulent boundary layer
TL;DR: In this article, the authors showed that at the lowest test speed and highest air injection rate, buoyancy pushed the air bubbles to the plate surface where they coalesced to form a nearly continuous gas film that persisted to the end of the plate with near-100% skin-friction drag reduction.
References
More filters
Journal ArticleDOI
Equation of motion for a small rigid sphere in a nonuniform flow
Martin R. Maxey,James J. Riley +1 more
TL;DR: In this paper, the forces on a small rigid sphere in a nonuniform flow are considered from first prinicples in order to resolve the errors in Tchen's equation and the subsequent modified versions that have since appeared.
Journal ArticleDOI
The hydrodynamic force on a rigid particle undergoing arbitrary time-dependent motion at small Reynolds number
TL;DR: In this article, the hydrodynamic force acting on a rigid spherical particle translating with arbitrary time-dependent motion in a timedependent flowing fluid is calculated to O(Re) for small but finite values of the Reynolds number, Re, based on the particle's slip velocity relative to the uniform flow.
Journal ArticleDOI
Flow past a sphere with an oscillation in the free-stream velocity and unsteady drag at finite Reynolds number
Renwei Mei,Ronald J. Adrian +1 more
TL;DR: In this article, a matched asymptotic solution is obtained for the frequency-dependent (or the acceleration-dependent) part of the unsteady flow at very small frequency, w, under the restriction St % Re 4 1, where St is the Strouhal number.
Journal ArticleDOI
Fourier Series on Spheres
TL;DR: In this article, the spectral methods for numerical solution of problems in spherical (and spheroidal) geometries are discussed and a new class of expansions based on special Fourier series are shown to lead to efficient and accurate simulations.
Journal ArticleDOI
Calculation of the steady flow past a sphere at low and moderate Reynolds numbers
S. C. R. Dennis,J. D. A. Walker +1 more
TL;DR: In this paper, the steady axially symmetric incompressible flow past a sphere is investigated for Reynolds numbers, based on the sphere diameter, in the range 0·1 to 40.
Related Papers (5)
Equation of motion for a small rigid sphere in a nonuniform flow
Martin R. Maxey,James J. Riley +1 more