Elastic instabilities in planar elongational flow of monodisperse polymer solutions
We investigate purely elastic flow instabilities in the almost ideal planar stagnation point elongational flow field generated by a microfluidic optimized-shape cross-slot extensional rheometer (OSCER). We use time-resolved flow velocimetry and full-field birefringence microscopy to study the behavi...
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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Nature Publishing Group
2017
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| Online Access: | http://hdl.handle.net/1721.1/108525 https://orcid.org/0000-0001-8323-2779 |
| _version_ | 1826209447293222912 |
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| author | Haward, Simon J. Shen, Amy Q. McKinley, Gareth H |
| author2 | Massachusetts Institute of Technology. Department of Mechanical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Mechanical Engineering Haward, Simon J. Shen, Amy Q. McKinley, Gareth H |
| author_sort | Haward, Simon J. |
| collection | MIT |
| description | We investigate purely elastic flow instabilities in the almost ideal planar stagnation point elongational flow field generated by a microfluidic optimized-shape cross-slot extensional rheometer (OSCER). We use time-resolved flow velocimetry and full-field birefringence microscopy to study the behavior of a series of well-characterized viscoelastic polymer solutions under conditions of low fluid inertia and over a wide range of imposed deformation rates. At low deformation rates the flow is steady and symmetric and appears Newtonian-like, while at high deformation rates we observe the onset of a flow asymmetry resembling the purely elastic instabilities reported in standard-shaped cross-slot devices. However, for intermediate rates, we observe a new type of elastic instability characterized by a lateral displacement and time-dependent motion of the stagnation point. At the onset of this new instability, we evaluate a well-known dimensionless criterion M that predicts the onset of elastic instabilities based on geometric and rheological scaling parameters. The criterion yields maximum values of M which compare well with critical values of M for the onset of elastic instabilities in viscometric torsional flows. We conclude that the same mechanism of tension acting along curved streamlines governs the onset of elastic instabilities in both extensional (irrotational) and torsional (rotational) viscoelastic flows. |
| first_indexed | 2024-09-23T14:22:39Z |
| format | Article |
| id | mit-1721.1/108525 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T14:22:39Z |
| publishDate | 2017 |
| publisher | Nature Publishing Group |
| record_format | dspace |
| spelling | mit-1721.1/1085252022-10-01T20:57:08Z Elastic instabilities in planar elongational flow of monodisperse polymer solutions Haward, Simon J. Shen, Amy Q. McKinley, Gareth H Massachusetts Institute of Technology. Department of Mechanical Engineering McKinley, Gareth H We investigate purely elastic flow instabilities in the almost ideal planar stagnation point elongational flow field generated by a microfluidic optimized-shape cross-slot extensional rheometer (OSCER). We use time-resolved flow velocimetry and full-field birefringence microscopy to study the behavior of a series of well-characterized viscoelastic polymer solutions under conditions of low fluid inertia and over a wide range of imposed deformation rates. At low deformation rates the flow is steady and symmetric and appears Newtonian-like, while at high deformation rates we observe the onset of a flow asymmetry resembling the purely elastic instabilities reported in standard-shaped cross-slot devices. However, for intermediate rates, we observe a new type of elastic instability characterized by a lateral displacement and time-dependent motion of the stagnation point. At the onset of this new instability, we evaluate a well-known dimensionless criterion M that predicts the onset of elastic instabilities based on geometric and rheological scaling parameters. The criterion yields maximum values of M which compare well with critical values of M for the onset of elastic instabilities in viscometric torsional flows. We conclude that the same mechanism of tension acting along curved streamlines governs the onset of elastic instabilities in both extensional (irrotational) and torsional (rotational) viscoelastic flows. 2017-05-01T13:31:06Z 2017-05-01T13:31:06Z 2016-09 2016-06 Article http://purl.org/eprint/type/JournalArticle 2045-2322 http://hdl.handle.net/1721.1/108525 Haward, Simon J.; McKinley, Gareth H. and Shen, Amy Q. “Elastic Instabilities in Planar Elongational Flow of Monodisperse Polymer Solutions.” Scientific Reports 6 (September 2016): 33029. © 2016 The Authors https://orcid.org/0000-0001-8323-2779 en_US http://dx.doi.org/10.1038/srep33029 Scientific Reports Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/ application/pdf Nature Publishing Group Nature |
| spellingShingle | Haward, Simon J. Shen, Amy Q. McKinley, Gareth H Elastic instabilities in planar elongational flow of monodisperse polymer solutions |
| title | Elastic instabilities in planar elongational flow of monodisperse polymer solutions |
| title_full | Elastic instabilities in planar elongational flow of monodisperse polymer solutions |
| title_fullStr | Elastic instabilities in planar elongational flow of monodisperse polymer solutions |
| title_full_unstemmed | Elastic instabilities in planar elongational flow of monodisperse polymer solutions |
| title_short | Elastic instabilities in planar elongational flow of monodisperse polymer solutions |
| title_sort | elastic instabilities in planar elongational flow of monodisperse polymer solutions |
| url | http://hdl.handle.net/1721.1/108525 https://orcid.org/0000-0001-8323-2779 |
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