Measuring Normal Stress Differences in Polymer Melt Shear Flow

1989 ◽  
Vol 33 (6) ◽  
pp. 843-864 ◽  
Author(s):  
J. Meissner ◽  
R. W. Garbella ◽  
J. Hostettler
Keyword(s):  
Shear Flow ◽  
Normal Stress ◽  
Polymer Melt ◽  
Normal Stress Differences

On the measurement of normal stress differences in steady shear flow

1981 ◽  
Vol 20 (3) ◽  
pp. 247-260 ◽  
Author(s):  
A. S. Lodge ◽  
T. H. Hou
Keyword(s):  
Shear Flow ◽  
Normal Stress ◽  
Steady Shear ◽  
Steady Shear Flow ◽  
Normal Stress Differences

scholarly journals Padé approximant for normal stress differences in large-amplitude oscillatory shear flow

2018 ◽  
Vol 30 (4) ◽  
pp. 040910 ◽  
Author(s):  
P. Poungthong ◽  
C. Saengow ◽  
A. J. Giacomin ◽  
C. Kolitawong ◽  
D. Merger ◽  
...  
Keyword(s):  
Shear Flow ◽  
Normal Stress ◽  
Large Amplitude ◽  
Padé Approximant ◽  
Oscillatory Shear ◽  
Large Amplitude Oscillatory Shear ◽  
Pade Approximant ◽  
Oscillatory Shear Flow ◽  
Normal Stress Differences

Determination of normal stress differences in steady shear flow

1968 ◽  
Vol 7 (4) ◽  
pp. 368-379 ◽  
Author(s):  
A. Kaye ◽  
A. S. Lodge ◽  
D. G. Vale
Keyword(s):  
Shear Flow ◽  
Normal Stress ◽  
Steady Shear ◽  
Steady Shear Flow ◽  
Normal Stress Differences

Inertial effects on the rheology of a dilute emulsion

2010 ◽  
Vol 646 ◽  
pp. 255-296 ◽  
Author(s):  
R. VIVEK RAJA ◽  
GANESH SUBRAMANIAN ◽  
DONALD L. KOCH
Keyword(s):  
Shear Flow ◽  
Normal Stress ◽  
Simple Shear ◽  
Reynolds Numbers ◽  
Reciprocal Theorem ◽  
Simple Shear Flow ◽  
Ohnesorge Number ◽  
Linear Flow ◽  
Bulk Stress ◽  
Normal Stress Differences

The behaviour of an isolated nearly spherical drop in an ambient linear flow is examined analytically at small but finite Reynolds numbers, and thereby the first effects of inertia on the bulk stress in a dilute emulsion of neutrally buoyant drops are calculated. The Reynolds numbers, Re = a2ρ/μ and $\hat{\Rey} \,{=}\, \dot{\gamma}a^2\rho/\hat{\mu}$, are the relevant dimensionless measures of inertia in the continuous and disperse(drop) phases, respectively. Here, a is the drop radius, is the shear rate, ρ is the common density and and μ are, respectively, the viscosities of the drop and the suspending fluid. The assumption of nearly spherical drops implies the dominance of surface tension, and the analysis therefore corresponds to the limit of the capillary number(Ca) based on the viscosity of the suspending fluid being small but finite; in other words, Ca ≪ 1, where Ca = μa/T, T being the coefficient of interfacial tension. The bulk stress is determined to O(φRe) via two approaches. The first one is the familiar direct approach based on determining the force density associated with the disturbance velocity field on the surface of the drop; the latter is determined to O(Re) from a regular perturbation analysis. The second approach is based on a novel reciprocal theorem formulation and allows the calculation, to O(Re), of the drop stresslet, and hence the emulsion bulk stress, with knowledge of only the leading-order Stokes fields. The first approach is used to determine the bulk stress for linear flows without vortex stretching, while the reciprocal theorem approach allows one to generalize this result to any linear flow. For the case of simple shear flow, the inertial contributions to the bulk stress lead to normal stress differences(N1, N2) at O(φRe), where φ(≪1) is the volume fraction of the disperse phase. Inertia leads to negative and positive contributions, respectively, to N1 and N2 at O(φRe). The signs of the inertial contributions to the normal stress differences may be related to the O(ReCa) tilting of the drop towards the velocity gradient direction. These signs are, however, opposite to that of the normal stress differences in the creeping flow limit. The latter are O(φCa) and result from an O(Ca2) deformation of the drop acting to tilt it towards the flow axis. As a result, even a modest amount of inertia has a significant effect on the rheology of a dilute emulsion. In particular, both normal stress differences reverse sign at critical Reynolds numbers(Rec) of O(Ca) in the limit Ca ≪ 1. This criterion for the reversal in the signs of N1 and N2 is more conveniently expressed in terms of a critical Ohnesorge number(Oh) based on the viscosity of the suspending fluid, where Oh = μ/(ρaT)1/2. The critical Ohnesorge number for a sign reversal in N1 is found to be lower than that for N2, and the precise numerical value is a function of λ. In uniaxial extensional flow, the Trouton viscosity remains unaltered at O(φRe), the first effects of inertia now being restricted to O(φRe3/2). The analytical results for simple shear flow compare favourably with the recent numerical simulations of Li & Sarkar (J. Rheol., vol. 49, 2005, p. 1377).

Possible Systematic Error in the Measurement of Normal Stress Differences in Polymer Solutions in Steady Shear Flow

Nature ◽  
1968 ◽  
Vol 217 (5123) ◽  
pp. 55-56 ◽  
Author(s):  
J. M. BROADBENT ◽  
A. KAYE ◽  
A. S. LODGE ◽  
D. G. VALE
Keyword(s):  
Shear Flow ◽  
Systematic Error ◽  
Normal Stress ◽  
Polymer Solutions ◽  
Steady Shear ◽  
Steady Shear Flow ◽  
Normal Stress Differences

Measurements of first and second normal stress differences in a polymer melt

2008 ◽  
Vol 148 (1-3) ◽  
pp. 41-46 ◽  
Author(s):  
E.A. Jensen ◽  
J.deC. Christiansen
Keyword(s):  
Normal Stress ◽  
Polymer Melt ◽  
Normal Stress Differences
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