Molecular weight dependence of the critical strain rate for flexible polymer solutions in elongational flow

1992 ◽  
Vol 25 (25) ◽  
pp. 7060-7062 ◽  
Author(s):  
Malika J. Menasveta ◽  
David A. Hoagland
Keyword(s):  
Molecular Weight ◽  
Strain Rate ◽  
Critical Strain ◽  
Polymer Solutions ◽  
Elongational Flow ◽  
Flexible Polymer ◽  
Molecular Weight Dependence ◽  
Critical Strain Rate

scholarly journals Primary Transverse Crevasses

1969 ◽  
Vol 8 (52) ◽  
pp. 107-129 ◽  
Author(s):  
G. Holdsworth
Keyword(s):  
Strain Rate ◽  
Longitudinal Strain ◽  
Critical Strain ◽  
Strain Rates ◽  
A Value ◽  
Regional Strain ◽  
Critical Strain Rate ◽  
Rate Gradient ◽  
Lines Of Evidence ◽  
Longitudinal Strain Rate

Measurements of strain-rates on a temperate glacier in a region of initial transverse fracturing indicate a critical strain-rate of 3.5±0.5 × 10−5d−1, associated with a regional strain-rate gradient of 5 × 10−8d−1m−1. At only one section of the glacier is the theoretical longitudinal strain-rate (Nye, 1959[c]) in approximate agreement with the value measured at the surface at that point. Corresponding measurements on a polar glacier (temperature −27.9°C at 10 m depth during the summer) indicate that the critical strain-rate is about 0.6±0.05 × 10−5d−1, which is associated with a gradient of strain rate of about 3 × 10−9d−1m−1. At one section there is close agreement between the theoretical and measured longitudinal strain-rate. For the temperate glacier crevasse depths ranged from 23.5 to 28 m; in the polar glacier one crevasse was 23.9±0.5 m deep, assuming a wedge form. Only an approximate agreement with the measured values of depth is obtained by using the regional strain-rate values in Nye’s crevasse-depth formula.Over a distance of 1.2 km the temperate glacier transverse crevasse spacings are very variable, ranging from 30 m to 96 m, but initially the spacings range from 55 m to 96 m, and for the first four cases the spacingsvaries from 2.7dto 3.3d, wheredis the crevasse depth. In the cold ice, crevasse spacings are far more uniform, ranging from 57 m to 66 m. A value ofs≈ 2.5dis obtained in only one case. This greater uniformity of spacing may be explained in terms of the dynamics of flow. Despite large differences in thermal, dimensional and strain-rate parameters between the two glaciers, (1) the crevasse depths are closely similar, and (2) the spacings of crevasses are similar. It has been demonstrated from two lines of evidence that the assumption that the strain on an intercrevasse block is negligible is not correct. The direction of the principal extending strain-rate is, in the most reliable cases, perpendicular to the crevasse traces within 2° to 7°.

Characterization of the interactions of two unequal co-rotating vortices

2010 ◽  
Vol 646 ◽  
pp. 233-253 ◽  
Author(s):  
LAURA K. BRANDT ◽  
KEIKO K. NOMURA
Keyword(s):  
Strain Rate ◽  
Critical Strain ◽  
Scaling Analysis ◽  
Rate Parameter ◽  
Critical Aspect ◽  
Critical Strain Rate ◽  
Single Compound ◽  
Compound Vortex ◽  
Strain Rate Parameter

The interactions and merging of two unequal co-rotating vortices in a viscous fluid are investigated. Two-dimensional numerical simulations of initially equal-sized vortices with differing relative strengths are performed. In the case of equal-strength vortices, i.e. symmetric vortex pairs (Brandt & Nomura, J. Fluid Mech., vol. 592, 2007, pp. 413–446), the mutually induced strain deforms and tilts the vortices, which leads to a core detrainment process. The weakened vortices are mutually entrained and rapidly move towards each other as they intertwine and destruct. The flow thereby develops into a single compound vortex. With unequal strengths, i.e. asymmetric pairs, the disparity of the vortices alters the interaction. Merger may result from reciprocal but unequal entrainment, which yields a compound vortex; however other outcomes are possible. The various interactions are classified based on the relative timing of core detrainment and core destruction of the vortices. Through scaling analysis and simulation results, a critical strain rate parameter which characterizes the establishment of core detrainment is identified and determined. The onset of merging is associated with the achievement of the critical strain rate by ‘both’ vortices, and a merging criterion is thereby developed. In the case of symmetric pairs, the critical strain rate parameter is shown to be related to the critical aspect ratio. In contrast with symmetric merger, which is in essence a flow transformation, asymmetric merger may result in the domination of the stronger vortex because of the unequal deformation rates. If the disparity of the vortex strengths is sufficiently large, the critical strain rate is not attained by the stronger vortex before destruction of the weaker vortex, and the vortices do not merge.

Molecular weight dependence of intrinsic viscosity of polymer solutions

1952 ◽  
Vol 9 (4) ◽  
pp. 381-384 ◽  
Author(s):  
W. R. Krigbaum ◽  
L. Mandelkern ◽  
P. J. Flory
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Polymer Solutions ◽  
Molecular Weight Dependence

scholarly journals Molecular Weight Dependence of Critical Amplitudes in Polymer Solutions

1981 ◽  
Vol 13 (12) ◽  
pp. 1119-1123 ◽  
Author(s):  
Kenji Shinozaki ◽  
Takuhei Nose
Keyword(s):  
Molecular Weight ◽  
Polymer Solutions ◽  
Molecular Weight Dependence ◽  
Critical Amplitudes
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