Effects of extensional viscosity of polymers on turbulent drag reduction analyzed by Film Interference Flow Imaging

2014 Fiscal Year Final Research Report

• Project/Area Number: 24760129
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Fluid engineering
• Research Institution: Kobe University
• Principal Investigator: HIDEMA Ruri 神戸大学, 学内共同利用施設等, 助教 (20598172)
• Research Collaborator: HIROSHI Suzuki 神戸大学, 大学院工学研究科, 教授 (90206524)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 乱流抑制 / 複雑流体 / レオロジー / 高分子

Outline of Final Research Achievements

An experimental study has been performed in order to investigate the relationship between the extensional viscosity of polymers and turbulent drag reduction (DR). Self-standing flowing soap film was used to obtain Two-dimensional grid turbulence which is mostly dominated by extensional flow. Polyethyleneoxide, as a flexible polymer, and hydroxypropyl cellulose, as a rigid rod-like polymer were added to the flow. The effects of these polymers were visualized by the interference pattern of flowing soap films. The vortex deformation by adding polymers was analyzed by Fourier transformation and wavelet transformation. The scaling exponents of the power spectrum of interference patterns indicate that the mechanism of DR due to the extensional viscosity is anisotropic. A wavelet analysis reveals the high and low fluctuations of the polymer added flow. Results from wavelet analysis indicate disappearing of original vortices, and appearing of new structures in low frequency in 2D flow.

Free Research Field

複雑流体のレオロジー