Numerical study of equilibrium radial positions of neutrally buoyant balls in circular Poiseuille flows

2021 ◽  
Vol 33 (3) ◽  
pp. 033301
Author(s):  
Tsorng-Whay Pan ◽  
Ang Li ◽  
Roland Glowinski
Keyword(s):  
Numerical Study ◽  
Neutrally Buoyant ◽  
Poiseuille Flows

Suspensions with a tunable effective viscosity: a numerical study

2012 ◽  
Vol 693 ◽  
pp. 345-366 ◽  
Author(s):  
L. Jibuti ◽  
S. Rafaï ◽  
P. Peyla
Keyword(s):  
Effective Viscosity ◽  
Volume Fraction ◽  
Numerical Study ◽  
Spherical Particles ◽  
Dimensionless Number ◽  
Particle Rotation ◽  
Concentrated Suspensions ◽  
Sheared Suspensions ◽  
Neutrally Buoyant ◽  
Universal Behaviour

AbstractIn this paper, we conduct a numerical investigation of sheared suspensions of non-colloidal spherical particles on which a torque is applied. Particles are mono-dispersed and neutrally buoyant. Since the torque modifies particle rotation, we show that it can indeed strongly change the effective viscosity of semi-dilute or even more concentrated suspensions. We perform our calculations up to a volume fraction of 28 %. And we compare our results to data obtained at 40 % by Yeo and Maxey (Phys. Rev. E, vol. 81, 2010, p. 62501) with a totally different numerical method. Depending on the torque orientation, one can increase (decrease) the rotation of the particles. This results in a strong enhancement (reduction) of the effective shear viscosity of the suspension. We construct a dimensionless number $\Theta $ which represents the average relative angular velocity of the particles divided by the vorticity of the fluid generated by the shear flow. We show that the contribution of the particles to the effective viscosity can be suppressed for a given and unique value of $\Theta $ independently of the volume fraction. In addition, we obtain a universal behaviour (i.e. independent of the volume fraction) when we plot the relative effective viscosity divided by the relative effective viscosity without torque as a function of $\Theta $. Finally, we show that a modified Faxén law can be equivalently established for large concentrations.

scholarly journals A numerical study of the motion of a neutrally buoyant cylinder in two dimensional shear flow

2013 ◽  
Vol 87 ◽  
pp. 57-66 ◽  
Author(s):  
Tsorng-Whay Pan ◽  
Shih-Lin Huang ◽  
Shih-Di Chen ◽  
Chin-Chou Chu ◽  
Chien-Cheng Chang
Keyword(s):  
Shear Flow ◽  
Numerical Study ◽  
Two Dimensional ◽  
Neutrally Buoyant

scholarly journals The motion of a neutrally buoyant particle of an elliptic shape in two dimensional shear flow: A numerical study

2015 ◽  
Vol 27 (8) ◽  
pp. 083303 ◽  
Author(s):  
Shih-Lin Huang ◽  
Shih-Di Chen ◽  
Tsorng-Whay Pan ◽  
Chien-Cheng Chang ◽  
Chin-Chou Chu
Keyword(s):  
Shear Flow ◽  
Numerical Study ◽  
Two Dimensional ◽  
Neutrally Buoyant

scholarly journals Dynamic Self-Assembly of Spinning Particles

2006 ◽  
Vol 129 (4) ◽  
pp. 379-387 ◽  
Author(s):  
Eric Climent ◽  
Kyongmin Yeo ◽  
Martin R. Maxey ◽  
George E. Karniadakis
Keyword(s):  
Reynolds Number ◽  
Self Assembly ◽  
Numerical Study ◽  
Magnetic Torque ◽  
Magnetic Attraction ◽  
Air Interface ◽  
Neutrally Buoyant ◽  
Individual Particles ◽  
Characteristic Scales ◽  
Number Of Particles

This paper presents a numerical study of the dynamic self-assembly of neutrally buoyant particles rotating in a plane in a viscous fluid. The particles experience simultaneously a magnetic torque that drives their individual spinning motion, a magnetic attraction toward the center of the domain, and flow-induced interactions. A hydrodynamic repulsion balances the centripetal attraction of the magnetized particles and leads to the formation of an aggregate of several particles that rotates with a precession velocity related to the inter-particle distance. This dynamic self-assembly is stable (but not stationary) and the morphology depends on the number of particles. The repulsion force between the particles is shown to be the result of the secondary flow generated by each particle at low but nonzero Reynolds number. Comparisons are made with analogous experiments of spinning disks at a liquid–air interface, where it is found that the variation in the characteristic scales of the aggregate with the rotation rate of individual particles are consistent with the numerical results.

Experimental and Numerical Studies of Cold Inflow at the Exit of Buoyant Channel Flows

1987 ◽  
Vol 109 (2) ◽  
pp. 392-399 ◽  
Author(s):  
Vijay Modi ◽  
K. E. Torrance
Keyword(s):  
Boundary Layer ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Critical Value ◽  
Ambient Fluid ◽  
Buoyant Jet ◽  
Wall Boundary Layer ◽  
Numerical Studies ◽  
Turbulent Flow Regime ◽  
Neutrally Buoyant

Experimental and numerical studies of the separation of a smooth attached buoyant flow from the inner wall of a duct, as the duct discharges into a quiescent environment, are reported. The associated penetration of neutrally buoyant ambient fluid into the duct is called cold inflow. The experimental study was carried out for air flows over ranges of Reynolds and Froude numbers, based on duct radius, of Re = 2400 to 3300 and Fr = 0.68 to 2.69. The experiments provide information on the onset and extent of cold inflow in a turbulent flow regime. Spatial profiles of fluctuating temperature reveal a wedge-shaped cold inflow region at the wall near the exit when Fr is decreased below a critical value. The numerical study examines the influence of Re and Fr on the structure of the cold inflow phenomenon at moderate Reynolds numbers (Re = 200 to 500 and Fr = 1 to 5). Steady-state, two-dimensional, laminar flow solutions reveal a region of downward-flowing cold air near the wall of the duct which leads to premature separation of the wall boundary layer. The separated boundary layer merges into the buoyant jet above the duct exit.

A numerical study of the dynamics of a particle settling at moderate Reynolds numbers in a linearly stratified fluid

2014 ◽  
Vol 750 ◽  
pp. 5-32 ◽  
Author(s):  
A. Doostmohammadi ◽  
S. Dabiri ◽  
A. M. Ardekani
Keyword(s):  
Settling Velocity ◽  
Peak Velocity ◽  
Numerical Study ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Stratified Fluid ◽  
Settling Particle ◽  
Settling Behaviour ◽  
Prandtl Numbers ◽  
Neutrally Buoyant

AbstractIn this paper, the transient settling dynamics of a spherical particle sedimenting in a linearly stratified fluid is investigated by performing fully resolved direct numerical simulations. The settling behaviour is quantified for different values of Reynolds, Froude and Prandtl numbers. It is demonstrated that the transient settling dynamics is correlated to the induced Lagrangian drift of flow around the settling particle. A simplified model is provided to predict the maximum velocity of the settling particle in linearly stratified fluids. The peak velocity can be followed by the oscillation of the settling velocity and the particle can even reverse its direction of motion before reaching to its neutrally buoyant level. The frequency of oscillation of settling velocity scales with the Brunt–Väisälä frequency and the motion of the particle can lead to the formation of secondary and tertiary vortices following the primary vortex.

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