The research team from the Tokyo University of Agriculture and Technology (TUAT) clearly demonstrates for the first time that the effect on flux reverses depending on the degree of change in properties due to the reaction in a reactive flow with production of viscoelastic material, through experiments involving high precision rheological measurements and a newly proposed theory. This is achieved by the fact that the viscoelastic properties affect the flow dynamics differently depending on the elasticity of the viscoelastic material.

These researchers published their results in Physical examination fluids February 16^and2022.

Reaction flows in which chemical reactions occur in a flowing fluid can be observed in a wide variety of fields, such as industrial, environmental, and biological applications. In reactive flows, changes in the physical properties of the fluid induced by chemical reactions can alter the dynamics of the flow. “Generally, flows change more significantly with larger changes in properties. However, this study demonstrates reactive liquid flow where the flow reverses in response to changes in physical properties,” said Dr. Nagatsu, one of the authors of the article, a professor in the Department of Chemical Engineering at TUAT.

The research team experimentally studies viscous fingering (VF) with the production of gel (a viscoelastic material) by a chemical reaction in the form of reactive flow. In VF, the interface forms a finger-like pattern when a more viscous fluid is displaced by a less viscous fluid in a porous medium or Hele-Shaw cells. “Our team demonstrates that gel production affects VF dynamics in opposite ways as a function of gel elasticity by combining with rheological measurements of the gel produced at the liquid-liquid interface. The VF pattern is approximately the same as the unresponsive one when gel elasticity is low, narrower when elasticity is medium, and wider when elasticity is high (see figure),” Nagatsu explained. “In addition, our team proposes a model that explains the opposite effects given the viscoelastic properties of the gel,” said Dr. Suzuki, the corresponding author of the paper, an assistant professor in the Department of Chemical Engineering at TUAT. “In this model, VF becomes thinner when the shear thinning viscosity of the gel is effective (blue region in Fig. (d)) and wider when the gel behaves like a solid material, thus reducing the permeability of the medium porous, which corresponds to the shear thickening viscosity of the gel being effective (red region in figure (d)).These viscoelastic properties are based on actual viscosity measurements of the gel mass itself (see figure Experimental results and theoretical considerations indicate that the opposite effects are driven by the multiple rheological properties, which are mainly responsible for the flow dynamics, depending on the gel elasticity.

“This result overturns the common understanding in reactive flow research that flow changes monotonically more significantly as the change in fluid properties due to reaction is greater, and drives reactive flow research to a new stage,” Nagatsu said. “The control of flow dynamics using the change in fluid properties induced by chemical reaction is called chemical flow control. Chemical flow control is based on such a common understanding. However, this study shows that such a common understanding is not always correct in chemical flow control with production of viscoelastic material, therefore this study will open new avenues for flow control using chemical reactions.

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Thanks. This study is supported by JSPS KAKENHI Grant No. 22686020, 25630049, 16K06068.

For more information about Nagatsu’s lab, please visit http://web.tuat.ac.jp/~nagatsu/en/index.html

Original publication

Reversal of the effects of gel production in a gel strength-dependent reaction flow

Sae Hirano, Yuichiro Nagatsu and Ryuta X. Suzuki

Phys. Rev. Fluids 7, 023201 (2022)

https://doi.org/10.1103/PhysRevFluids.7.023201

About Tokyo University of Agriculture and Technology (TUAT)

TUAT is a distinguished university in Japan dedicated to science and technology. TUAT focuses on agriculture and engineering which form the foundation of the industry and promotes fields of education and research which integrate them. Boasting a history of over 140 years since its founding in 1874, TUAT continues to boldly take on new challenges and steadily promote areas. With high ethics, TUAT assumes social responsibility in the ability to transmit scientific and technological information towards building a sustainable society where human beings and nature can thrive in a symbiotic relationship. For more information, please visit http://www.tuat.ac.jp/en/.

Contact

Yuichiro Nagatsu, Ph.D.

Professor, Department of Chemical Engineering, TUAT, Japan

nagatsu@cc.tuat.ac.jp

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