| 研究開始時の研究の概要 |
Extensional viscosity of viscoelastic fluids is of fundamental importance in fluid handling and processing operations. Extensional viscosity depends on the fluid strain and strain-rate, and likely on the mode of deformation: uniaxial, planar or biaxial. The 3D microfabrication of geometries designed to measure the extensional viscosity in different deformation regimes will advance the measurement of the extensional properties of viscoelastic fluids. The results will aid the understanding and optimization of processes such as fiber spinning, ink-jet printing, blow-moulding, etc.
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| 研究実績の概要 |
The purpose of the research project was to develop a device to generate uniaxial and biaxial extensional flows and to quantify differences between the uniaxial, planar and biaxial extensional rheology of polymer solutions. In FY2023, the research plan has been fully completed and all objectives achieved.
Two journal papers were published in the AIP publication Journal of Rheology detailing the core results of the project. The first paper details the design, fabrication and experimental validation of a 3D microfluidic device named the optimized uniaxial and biaxial extensional rheometer (OUBER). The second paper details experiments measuring the pressure drop and velocity field for viscoelastic polyacrylamide solutions (at dilute concentrations of 0.005 to 0.04 wt%) in the OUBER, and in a planar extensional flow device, and the resulting determination of the uniaxial, planar and biaxial extensional viscosity.
Furthermore, a third paper has been published on the characterization of a novel instability that occurs for highly elastic uniaxial extensional flows. We have found that the phenomena is described as a ‘regular bifurcation’, similar to a pitchfork bifurcation rotated around the control parameter axis. This exciting work has recently been published in a special issue of the Journal of Non-Newtonian Fluid Mechanics.
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