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The addition of a small amount of a polymer or surfactant to a Newtonian fluid drastically changes the dynamics of the fluids. This is because the inherent time and length scales of the flows are influenced by the deformation and relaxation process of polymers or surfactants. In the first part of this talk, I will highlight characteristic vortex deformation and energy transfer caused by polymers and wormlike micelles in a two-dimensional turbulent flow. The effects of the extensional rheological properties of these solutions were focused to understand the vortex deformation in turbulent flow and turbulent statistics [1-3]. In the second part, I will introduce a method to detect non-uniform local viscosity of polymer and worm-like micellar solutions using optical tweezers at micrometer length scale. Power spectrum density of a particle displacement trapped by optical tweezers was analyzed to calculate the local viscosity distribution [4].
1. R. Hidema, “Interactions between polymers and flows in macro and micro length scales”, Science Talks, 3, 100040 (2022)
2. K. Fukushima, H. Kishi, H. Suzuki, R. Hidema, “Modification of turbulence caused by cationic surfactant wormlike micellar structures in two-dimensional turbulent flow”, Journal of Fluid Mechanics, 933, A9 (2022)
3. R. Hidema, K. Fukuashima, R. Yoshida, H. Suzuki, “Vortex deformation and turbulent energy of polymer solution in a two-dimensional turbulent flow”, Journal of Non-Newtonian Fluid Mechanics, 285, 104385 (2020)
4. R. Hidema, Zenji Yatabe, Hikari Takahashi, Ryusei Higashikawa, Hiroshi Suzuki, “Inverse integral transformation method to derive local viscosity distribution measured by optical tweezers”, Soft Matter, 16, 6826-6833 (2020)