Paper Number
NF13
Session
Non-Newtonian Fluid Mechanics & Flow Instabilities
Title
Plant sourced biopolymers for turbulent drag reduction
Presentation Date and Time
October 16, 2018 (Tuesday) 5:00
Track / Room
Track 7 / Plaza II
Authors
- Rajappan, Anoop (Massachusetts Institute of Technology)
- McKinley, Gareth H. (Massachusetts Institute of Technology)
Author and Affiliation Lines
Anoop Rajappan and Gareth H. McKinley
Massachusetts Institute of Technology, Cambridge, MA 02139
Speaker / Presenter
Rajappan, Anoop
Text of Abstract
The cost of polymer additives has been a key impediment in the adoption of polymer drag reduction techniques in large-scale marine applications. In this study, we investigate the mucilage extracted from the bran of plant seeds such as flax, chia and psyllium, as potential sources of inexpensive, water-soluble, high molecular weight polymers for drag reduction in turbulent boundary layer flows. To this end, skin friction measurements in dilute solutions of both synthetic as well as plant-based high polymers are performed using a custom-built Taylor-Couette apparatus, operating in the fully turbulent flow regime, at Reynolds numbers between 11000 and 86000. As a specific example, we characterize the drag reducing properties of the aqueous mucilage extracted from flax seeds (Linum usitatissimum), and compare its performance to that of a commonly used synthetic polymer, namely, polyethylene oxide (PEO). The molecular and viscoelastic properties of the principal polysaccharide constituent in flax mucilage is also studied using size exclusion chromatography and extensional rheology techniques (CaBER). Finally, we compare the shear-induced degradation of both polymers under prolonged turbulent flow conditions, and explore the possibility of mitigating chain-scission processes by the use of surfactant additives. The dilute mucilage solutions are seen to exhibit comparable drag reduction and degradation behavior as aqueous PEO, and can possibly serve as an effective, eco-friendly, and economical alternative to synthetic polymers in real-life drag reduction applications.