Cross-stream migration of droplets in a confined shear-thinning viscoelastic flow: Role of shear-thinning induced lift

2020 ◽  
Vol 32 (9) ◽  
pp. 092007 ◽  
Author(s):  
S. Hazra ◽  
S. K. Mitra ◽  
A. K. Sen
Keyword(s):  
Shear Thinning ◽  
Viscoelastic Flow ◽  
Stream Migration

Haemorheological Effects on Thrombocyte Adhesion and Aggregation Found Under Controlled Flow Conditions

1979 ◽  
Author(s):  
P.D. Richardson
Keyword(s):  
Rate Of Change ◽  
Continuous Observation ◽  
Flow Conditions ◽  
Wide Range ◽  
Stream Migration ◽  
Local Shear ◽  
Videotape Recording ◽  
Controlled Flow ◽  
A Site

Thrombocyte adhesion and aggregation in a vessel or on a chamber wall can be measured most readily if the flow is controlled and steady, and continuous observation is used. Videotape recording is very helpful for subsequent quantification of the dynamics. The adhesion of each thrombocyte can occur for a finite time interval:this interval has been observed to have a wide range. Platelets which escape often leave open a site which attracts other platelets preferentially. The rate of change of adhesion density (platelets/mm2) is affected by the local shear rate and the shear history upstream. Aggregation is affected similarly, and also proceeds with some platelet turnover. The role of erythrocytes in facilitating cross-stream migration of thrombocytes (which can enhance the growth rate of large thrombi) appears due in part to convective flow fields induced by the motion of erythrocytes in a shear flow, which can be demonstrated theoretically and experimentally. Observations of the phenomenlogy of adhesion and aggregation under controlled flow conditions and comparison with fLu id-dynamically based theory allows representation in terras of a small number of parameters with prospects of prediction of behaviour over a wide range of haemodynamic conditions; biochemical changes lead to changes in values of the parameters, so that activating agents and inhibiting agents modify values in different directions.

Role of Functionality in Cross-Stream Migration, Structures, and Dynamics of Star Polymers in Poiseuille Flow

2020 ◽  
Vol 53 (22) ◽  
pp. 9993-10004
Author(s):  
Aiqing Liu ◽  
Zhenyue Yang ◽  
Lijun Liu ◽  
Jizhong Chen ◽  
Lijia An
Keyword(s):  
Poiseuille Flow ◽  
Star Polymers ◽  
Stream Migration

scholarly journals String formation in sheared suspensions in rheologically complex media: The essential role of shear thinning

2014 ◽  
Vol 58 (1) ◽  
pp. 237-254 ◽  
Author(s):  
Sylvie Van Loon ◽  
Jan Fransaer ◽  
Christian Clasen ◽  
Jan Vermant
Keyword(s):  
Essential Role ◽  
Shear Thinning ◽  
Complex Media ◽  
String Formation ◽  
Sheared Suspensions

Role of shear-thinning on the dynamics of rinsing flow by an impinging jet

2012 ◽  
Vol 24 (9) ◽  
pp. 093102 ◽  
Author(s):  
Travis W. Walker ◽  
Tienyi T. Hsu ◽  
Curtis W. Frank ◽  
Gerald G. Fuller
Keyword(s):  
Impinging Jet ◽  
Shear Thinning

A numerical study of viscoelastic effects in chaotic mixing between eccentric cylinders

2000 ◽  
Vol 412 ◽  
pp. 197-225 ◽  
Author(s):  
YURUN FAN ◽  
ROGER I. TANNER ◽  
NHAN PHAN-THIEN
Keyword(s):  
Shear Thinning ◽  
Periodic Points ◽  
Deborah Number ◽  
Viscoelastic Flow ◽  
Chaotic Mixing ◽  
Periodic Flow ◽  
Passive Tracer ◽  
Newtonian Flow ◽  
Transient Period ◽  
The Mean

In this paper, we are concerned with the effect of fluid elasticity and shear-thinning viscosity on the chaotic mixing of the flow between two eccentric, alternately rotating cylinders. We employ the well-developed h-p finite element method to achieve a high accuracy and efficiency in calculating steady solutions, and a full unsteady algorithm for creeping viscoelastic flows to study the transient process in this periodic viscoelastic flow. Since the distribution of periodic points of the viscoelastic flow is not symmetric, we have developed a domain-search algorithm based on Newton iteration for locating the periodic points. With the piecewise-steady approximation, our computation for the upper-convected Maxwell fluid predicts no noticeable changes of the advected coverage of a passive tracer from Newtonian flow, with elasticity levels up to a Deborah number of 1.0. The stretching of the fluid elements, quantified by the geometrical mean of the spatial distribution, remains exponential up to a Deborah number of 6.0, with only slight changes from Newtonian flow. On the other hand, the shear-thinning viscosity, modelled by the Carreau equation, has a large impact on both the advection of a passive tracer and the mean stretching of the fluid elements. The creeping, unsteady computations show that the transient period of the velocity is much shorter than the transient period of the stress, and from a pragmatic point of view, this transient process caused by stress relaxation due to sudden switches of the cylinder rotation can be neglected for predicting the advective mixing in this time- periodic flow. The periodic points found up to second order and their eigenvalues are indeed very informative in understanding the chaotic mixing patterns and the qualitative changes of the mean stretching of the fluid elements. The comparison between our computations and those of Niederkorn & Ottino (1993) reveals the importance of reducing the discretization error in the computation of chaotic mixing. The causes of the discrepancy between our prediction of the tracer advection and Niederkorn & Ottino's (1993) experiment are discussed, in which the influence of the shear-thinning first normal stress difference is carefully examined. The discussion leads to questions on whether small elasticity of the fluid has a large effect on the chaotic mixing in this periodic flow.

Simulations of three-dimensional viscoelastic flows past a circular cylinder at moderate Reynolds numbers

2010 ◽  
Vol 651 ◽  
pp. 415-442 ◽  
Author(s):  
DAVID RICHTER ◽  
GIANLUCA IACCARINO ◽  
ERIC S. G. SHAQFEH
Keyword(s):  
Circular Cylinder ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Viscoelastic Flow ◽  
Dimensional Structure ◽  
Recirculation Region ◽  
Viscoelastic Flows ◽  
Cylinder Wake ◽  
Complex Flows

The results from a numerical investigation of inertial viscoelastic flow past a circular cylinder are presented which illustrate the significant effect that dilute concentrations of polymer additives have on complex flows. In particular, effects of polymer extensibility are studied as well as the role of viscoelasticity during three-dimensional cylinder wake transition. Simulations at two distinct Reynolds numbers (Re = 100 and Re = 300) revealed dramatic differences based on the choice of the polymer extensibility (L2 in the FENE-P model), as well as a stabilizing tendency of viscoelasticity. For the Re = 100 case, attention was focused on the effects of increasing polymer extensibility, which included a lengthening of the recirculation region immediately behind the cylinder and a sharp increase in average drag when compared to both the low extensibility and Newtonian cases. For Re = 300, a suppression of the three-dimensional Newtonian mode B instability was observed. This effect is more pronounced for higher polymer extensibilities where all three-dimensional structure is eliminated, and mechanisms for this stabilization are described in the context of roll-up instability inhibition in a viscoelastic shear layer.

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