Optimized Cross-Slot Flow Geometry for Microfluidic Extensional Rheometry
A precision-machined cross-slot flow geometry with a shape that has been optimized by numerical simulation of the fluid kinematics is fabricated and used to measure the extensional viscosity of a dilute polymer solution. Full-field birefringence microscopy is used to monitor the evolution and growth...
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| Other Authors: | , , |
| Format: | article |
| Language: | eng |
| Published: |
2012
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10216/106718 |
| Country: | Portugal |
| Oai: | oai:repositorio-aberto.up.pt:10216/106718 |
| Summary: | A precision-machined cross-slot flow geometry with a shape that has been optimized by numerical simulation of the fluid kinematics is fabricated and used to measure the extensional viscosity of a dilute polymer solution. Full-field birefringence microscopy is used to monitor the evolution and growth of macromolecular anisotropy along the stagnation point streamline, and we observe the formation of a strong and uniform birefringent strand when the dimensionless flow strength exceeds a critical Weissenberg number Wi(crit) approximate to 0.5. Birefringence and bulk pressure drop measurements provide self-consistent estimates of the planar extensional viscosity of the fluid over a wide range of deformation rates (26 s(-1) <= (epsilon) over dot <= 435 s(-1)) and are also in close agreement with numerical simulations performed by using a finitely extensible nonlinear elastic dumbbell model. |
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