On the anisotropic response of a Janus drop in a shearing viscous fluid

2015 ◽  
Vol 770 ◽  
Author(s):  
Misael Díaz-Maldonado ◽  
Ubaldo M. Córdova-Figueroa
Keyword(s):  
Shear Flow ◽  
Velocity Gradient ◽  
External Flow ◽  
Bodies Of Revolution ◽  
Internal Interface ◽  
Equal Radius ◽  
Fluid Drop ◽  
Resistance Matrix ◽  
Shearing Motion ◽  
Unbounded Fluid

The force and couple that result from the shearing motion of a viscous, unbounded fluid on a Janus drop are the subjects of this investigation. A pair of immiscible, viscous fluids comprise the Janus drop and render it with a ‘perfect’ shape: spherical with a flat, internal interface, in which each constituent fluid is bounded by a hemispherical domain of equal radius. The effect of the arrangement of the internal interface (drop orientation) relative to the unidirectional shear flow is explored within the Stokes regime. Projection of the external flow into a reference frame centred on the drop simplifies the analysis to three cases: (i) a shear flow with a velocity gradient parallel to the internal interface, (ii) a hyperbolic flow, and (iii) two shear flows with a velocity gradient normal to the internal interface. Depending on the viscosity of the internal fluids, the Janus drop behaves as a simple fluid drop or as a solid body with broken fore and aft symmetry. The resultant couple arises from both the straining and swirling motions of the external flow in analogy with bodies of revolution. Owing to the anisotropic resistance of the Janus drop, it is inferred that the drop can migrate lateral to the streamlines of the undisturbed shear flow. The grand resistance matrix and Bretherton constant are reported for a Janus drop with similar internal viscosities.

A Novel Method to Order Nanowire Based on Macrofludic System

2014 ◽  
Vol 1015 ◽  
pp. 32-36
Author(s):  
Ting Zhong Xu ◽  
Hebibul Rahman ◽  
Li Bo Zhao ◽  
Yu Long Zhao ◽  
Zhuang De Jiang
Keyword(s):  
Molecular Dynamics ◽  
Shear Flow ◽  
Velocity Gradient ◽  
Rotational Speed ◽  
Md Simulation ◽  
Bulk Material ◽  
Economical Method ◽  
Uniform Velocity ◽  
Novel Method

The rheology of nanowires (NWs) and nanotubes (NTs) in shear flow has been analyzed by molecular dynamics (MD) simulation and macrofludic simulation. A method based on macrofludic system for aligning NWs and NTs is demonstrated. In this method, vortex is generated near the surface of a plane by using a mushroom like turnplate. Then a uniform velocity gradient was generated on the surface of the plane. Through controlling the rotational speed of the turnplate, the rheology of NWs and NTs in suspension can be easily controlled. So it provides a more effective and economical method for the alignment of NWs and NTs, as well as forming the anisotropy NWs and NTs bulk material.

Flow induced crystallization of LDPE nanocomposites: A rheological and morphological characterization

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Fiorenza Azzurri ◽  
Paola Stagnaro ◽  
Lucia Conzatti ◽  
Dario Cavallo ◽  
Luca Repetto ◽  
...  
Keyword(s):  
Shear Flow ◽  
Flow Direction ◽  
Crystallization Rate ◽  
Morphological Characterization ◽  
External Flow ◽  
Nucleation Density ◽  
Induced Crystallization ◽  
Flow Induced Crystallization ◽  
Nucleating Effect

AbstractThe flow induced crystallization behaviour of a LDPE:PE-g-MA:D72T 90:9:1 nanocomposite has been investigated by in-situ Rheo-SALS technique and data have been compared with those obtained from a reference LDPE:PE-g-MA 90:9 sample. Rheo SALS results, confirming thermal analysis findings, indicate that under mild shear flow fields the organoclay exhibits a negligible nucleating effect. Both nucleation density and, as a consequence, crystallization rate, are not appreciably affected by the application of external flow field for both the examined systems, revealing that no evident synergic effects between the organoclay and the shear flow are present. On the other hand, Rheo SALS analysis indicates that the nanocomposite submitted to flow exhibits a higher level of crystal orientation. TEM morphological analyses support this observation suggesting that the orientation of the nanofiller along the flow direction templates the growth of oriented crystals.

scholarly journals The kinematics of the reduced velocity gradient tensor in a fully developed turbulent free shear flow

2015 ◽  
Vol 767 ◽  
pp. 627-658 ◽  
Author(s):  
P. K. Rabey ◽  
A. Wynn ◽  
O. R. H. Buxton
Keyword(s):  
Shear Flow ◽  
Strain Rate ◽  
Velocity Gradient ◽  
Mixing Layer ◽  
Joint Probability ◽  
Strain Rate Tensor ◽  
Gradient Tensor ◽  
Local Isotropy ◽  
Velocity Gradient Tensor ◽  
Kinematic Behaviour

AbstractThis paper examines the kinematic behaviour of the reduced velocity gradient tensor (VGT),$\tilde{\unicode[STIX]{x1D608}}_{ij}$, which is defined as a$2\times 2$block, from a single interrogation plane, of the full VGT$\unicode[STIX]{x1D608}_{ij}=\partial u_{i}/\partial x_{j}$. Direct numerical simulation data from the fully developed turbulent region of a nominally two-dimensional mixing layer are used in order to examine the extent to which information on the full VGT can be derived from the reduced VGT. It is shown that the reduced VGT is able to reveal significantly more information about regions of the flow in which strain rate is dominant over rotation. It is thus possible to use the assumptions of homogeneity and isotropy to place bounds on the first two statistical moments (and their covariance) of the eigenvalues of the reduced strain-rate tensor (the symmetric part of the reduced VGT) which in turn relate to the turbulent strain rates. These bounds are shown to be dependent upon the kurtosis of$\partial u_{1}/\partial x_{1}$and another variable defined from the constituents of the reduced VGT. The kurtosis is observed to be minimised on the centreline of the mixing layer and thus tighter bounds are possible at the centre of the mixing layer than at the periphery. Nevertheless, these bounds are observed to hold for the entirety of the mixing layer, despite departures from local isotropy. The interrogation plane from which the reduced VGT is formed is observed not to affect the joint probability density functions (p.d.f.s) between the strain-rate eigenvalues and the reduced strain-rate eigenvalues despite the fact that this shear flow has a significant mean shear in the cross-stream direction. Further, it is found that the projection of the eigenframe of the strain-rate tensor onto the interrogation plane of the reduced VGT is also independent of the plane that is chosen, validating the approach of bounding the full VGT using the assumption of local isotropy.

Response behaviour of hot wires in shear flow

1971 ◽  
Vol 47 (3) ◽  
pp. 449-468 ◽  
Author(s):  
F. B. Gessner ◽  
G. L. Moller
Keyword(s):  
Shear Flow ◽  
Velocity Gradient ◽  
Response Curves ◽  
Mean Velocity ◽  
General Applicability ◽  
Response Characteristics ◽  
Response Behaviour ◽  
Intensity Measurements ◽  
Temperature Distributions ◽  
Infrared Microscope

The response characteristics of a hot wire operated at constant temperature and exposed to a mean-velocity gradient along its length are examined both analytically and experimentally. The shear sensitivity of local wire temperature distributions, as measured with an infrared microscope, are compared with predicted temperature distributions in order to select a convective heat transfer correlation which can be applied locally along a wire in shear flow. On the basis of this correlation, the steady-state and dynamic response behaviour of platinum and tungsten wires in shear flow are examined by means of computer-generated data. Response curves of general applicability are presented which can be used to correct local mean-velocity and turbulence intensity measurements whenever a mean-velocity gradient exists along a wire.

Binary collision of drops in simple shear flow by computer-assisted video optical microscopy

1998 ◽  
Vol 357 ◽  
pp. 1-20 ◽  
Author(s):  
S. GUIDO ◽  
M. SIMEONE
Keyword(s):  
Shear Flow ◽  
Optical Microscopy ◽  
Velocity Gradient ◽  
Contact Region ◽  
Rare Event ◽  
Major Axis ◽  
Immiscible Liquid ◽  
Computer Assisted ◽  
Simple Shear Flow ◽  
Gradient Direction

The collision of two equi-sized drops immersed in an immiscible liquid phase undergoing a shear flow in a parallel plate apparatus has been investigated over a range of capillary numbers. The drops were observed along the vorticity direction of shear flow by video enhanced contrast optical microscopy. Images of the colliding drops were processed by image analysis techniques. The distance Δy between the drop centres along the velocity gradient direction was measured as a function of time during approach, collision and separation of the two drops. It was found that Δy increases irreversibly after collision, thus providing a mechanism for drop dispersion in a concentrated system. Drop shape evolution during collision was characterized by measuring a deformation parameter and the angle made by the drop major axis with respect to the velocity gradient direction. The extent of the near-contact region when the drops are sliding on each other was also estimated. Coalescence was a rare event and was observed in the extensional quadrant of the shear flow. The experimental results show good agreement with numerical simulations recently reported in the literature.

An Alternate Approach to the Problem of Stokes’ Flow

1967 ◽  
Vol 34 (1) ◽  
pp. 8-10
Author(s):  
F. Pollock ◽  
R. E. Struzynski
Keyword(s):  
Shear Flow ◽  
Green’S Function ◽  
Flow Pattern ◽  
Green's Function ◽  
Stokes Flow ◽  
Poiseuille Flow ◽  
External Flow ◽  
Uniform Flow ◽  
Uniqueness Of Solution ◽  
Linear Shear

The problem of Stokes’ flow for a sphere in arbitrary external flow pattern is solved using a particular scalar Green’s function. By this method, the uniqueness of solution is clearly shown, and arbitrary flows (linear shear flow, Poiseuille flow, and so on) are seen to be as straightforward as simple uniform flow.

scholarly journals Ferrocholesteric–ferronematic transitions induced by shear flow and magnetic field

2017 ◽  
Vol 8 ◽  
pp. 2552-2561 ◽  
Author(s):  
Dmitriy V Makarov ◽  
Alexander A Novikov ◽  
Alexander N Zakhlevnykh
Keyword(s):  
Magnetic Field ◽  
Shear Flow ◽  
Velocity Gradient ◽  
Orientation Angle ◽  
Helical Structure ◽  
Shear Velocity ◽  
Critical Magnetic Field ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
The Magnetic Field

We study the unwinding of the ferrocholesteric helical structure induced by a combined action of a magnetic field and a shear flow. Both influences are able to induce the ferrocholesteric–ferronematic transition independently; however, the differences between the magnetic field orientation and the flow alignment direction lead to a competition between magnetic and hydrodynamic mechanisms of influence on the ferrocholesteric structure. We analyze various orientations of a magnetic field relative to the direction of a shear flow. The pitch of the ferrocholesteric helix is obtained as function of the strength and the orientation angle of the magnetic field, the shear velocity gradient and a reactive parameter. Phase diagrams of ferrocholesteric–ferronematic transition and the pitch of the ferrocholesteric helix as functions of the material and the governing parameters are calculated. We find out that imposing a shear flow leads to a shift of the magnetic field threshold. The value of the critical magnetic field depends on the magnetic field orientation, the velocity gradient, and the viscous coefficients. We show that the interplay of a magnetic field and a shear flow can induce reentrant orientational transitions that are ferrocholesteric–ferronematic–ferrocholesteric.

Experiments on nearly homogeneous turbulent shear flow

1970 ◽  
Vol 41 (1) ◽  
pp. 81-139 ◽  
Author(s):  
F. H. Champagne ◽  
V. G. Harris ◽  
S. Corrsin
Keyword(s):  
Shear Stress ◽  
Energy Transfer ◽  
Shear Flow ◽  
Velocity Gradient ◽  
Turbulent Velocity ◽  
Wave Number ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Principal Axes ◽  
The Mean

With a transverse array of channels of equal widths but differing resistances, we have generated an improved approximation to spatially homogeneous turbulent shear flow. The scales continue to grow with downstream distance, even in a region where the mean velocity gradient and one-point turbulence moments (component energies and shear stress) have attained essentially constant values. This implies asymptotic non-stationarity in the basic Eulerian frame convected with the mean flow, behaviour which seems to be inherent to homogeneous turbulent shear flow.Two-point velocity correlations with space separation and with space-time separation yield characteristic departures from isotropy, including clear ‘upstream–downstream’ unsymmetries which cannot be classified simply as axis tilting of ellipse-like iso-correlation contours.The high wave-number structure is roughly locally isotropic although the turbulence Reynolds number based on Taylor ‘microscale’ and r.m.s. turbulent velocity is only 130. Departures from isotropy in the turbulent velocity gradient moments are measurable.The approximation to homogeneity permits direct estimation of all components of the turbulent pressure/velocity-gradient tensor, which accounts for inter-component energy transfer and helps to regulate the turbulent shear stress. It is found that its principal axes are aligned with those of the Reynolds stress tensor. Finally, the Rotta (1951, 1962) linear hypothesis for intercomponent energy transfer rate is roughly confirmed.

Particle Motions in Sheared Suspensions. XXVIII. Configurations of Coiled Fibers in Shear Flow

1975 ◽  
Vol 53 (18) ◽  
pp. 2689-2694 ◽  
Author(s):  
A. Okagawa ◽  
S. G. Mason
Keyword(s):  
Steady State ◽  
Shear Flow ◽  
Velocity Gradient ◽  
Spherical Symmetry ◽  
Orthogonal Axis ◽  
The Third ◽  
End To End ◽  
Sheared Suspensions

The coiling of elastomer filaments in liquids undergoing shear flow was studied experimentally. In the steady state the rotating coils were stretched along the axes of flow and vorticity, compacted along the third orthogonal axis, and became progressively more entangled as the velocity gradient increased. Although the coils did not possess spherical symmetry, the distribution of end-to-end distances and maximum projected dimensions projected on a given axis or plane corresponded closely to random coiling statistics.

scholarly journals On the hydrodynamics of ‘slip–stick’ spheres

2008 ◽  
Vol 606 ◽  
pp. 115-132 ◽  
Author(s):  
JAMES W. SWAN ◽  
ADITYA S. KHAIR
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Spherical Particle ◽  
Stokes Flow ◽  
Velocity Gradient ◽  
Slip Length ◽  
Rotational Velocity ◽  
Spherical Particles ◽  
Force Density ◽  
Translational Velocity

The breakdown of the no-slip condition at fluid–solid interfaces generates a host of interesting fluid-dynamical phenomena. In this paper, we consider such a scenario by investigating the low-Reynolds-number hydrodynamics of a novel ‘slip–stick’ spherical particle whose surface is partitioned into slip and no-slip regions. In the limit where the slip length is small compared to the size of the particle, we first compute the translational velocity of such a particle due to the force density on its surface. Subsequently, we compute the rotational velocity and the response to an ambient straining field of a slip–stick particle. These three Faxén-type formulae are rich in detail about the dynamics of the particles: chiefly, we find that the translational velocity of a slip–stick sphere is coupled to all of the moments of the force density on its surface; furthermore, such a particle can migrate parallel to the velocity gradient in a shear flow. Perhaps most important is the coupling we predict between torque and translation (and force and rotation), which is uncharacteristic of spherical particles in unbounded Stokes flow and originates purely from the slip–stick asymmetry.

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