Folding of highly viscous non-Newtonian fluids in diverging microchannels

• Main Author: Tee, Kai Ren
• Other Authors: Wong Teck Neng
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/72079
• Institution: Nanyang Technological University

Microfluidic devices were used widely to study the behavior of fluid flow in a controlled manner. An interesting topic in the field of mixing two viscous fluids is utilizing the phenomenon of folding of a viscous thread in a diverging channel. This report mainly focuses on the flow instability of a highly viscous miscible non-Newtonian fluid thread ensheathed by the less viscous Newtonian fluid when it enters a diverging channel which serves as a potential method for mixing two fluids. A comprehensive review of literature papers will be shared in Chapter Two. The conduct of the experiment and the definitions of observed parameters will be briefed in Chapter Three and Chapter Four respectively. Poly(ethylene) oxide (PEO), a type of shear thinning Non-Newtonian fluid of mass concentration 1%,2% and 3% in deionized water is injected into the channel through the central inlet using neMESYS syringe pump. The Newtonian fluid, 73.5% w.t Ethylene Glycol in 26.5%w.t Ethanol is pumped through the side channels simultaneously. A high-speed camera is used to observe the flow morphology that occurs at the diverging channel. This recording is captured on the software Phantom Camera Control (PCC). The file is extracted into ImageJ to improve image quality and measurements on the observed parameters. A detailed discussion of the results and findings were elaborated in Chapter 5. These results include the comparison between a Newtonian viscous thread and a non-Newtonian viscous thread on the effects of viscosity ratio, flow rate ratio and flow rate on its morphology, frequency, thread diameter, envelope width and the onset of folding. Subsequently, the influence of the diverging channel width and angle on its morphology and observed parameters were presented. Following, a simple operation map will be presented to identify regions of interest where the observed threading or folding morphology would occur. The report concludes with a brief summary of the overall Final Year Project with insights and recommendations for further improvement. It serves as a helpful guide and understanding for subsequent works on this topic.