Newsletter  2016.11  Index

Theme : "Mechanical Engineering Congress, 2016 Japan (MECJ-16)" Preface (H.FUJII, H.YOKOYAMA, D. WATANABE) Counter-Rotating Type Turbo-Unit Leaving to Markets Toshiaki KANEMOTO (Saga University) Characteristics of Non-equilibrium Grid Turbulence and Scalar Transfer Mechanism Yasuhiko SAKAI, Koji Nagata, Yasumasa Ito, Tomoaki Watanabe, Koji Iwano (Nagoya University) New developments in study of complex fluids Takehiro YAMAMOTO (Osaka Electro-Communication University), Takatsune NARUMI (Niigata University), Shigeomi CHONO (Kochi University of Technology) Bio-related-particle suspensions as complex fluids Takehiro YAMAMOTO (Osaka Electro-Communication University) Energy transfer and drag reduction in the fluid diluted with non-affine polymers Kiyosi HORIUTI (Tokyo Institute of Technology） EFD workshop: optical measurement technique in fluid dynamics Masaki FUCHIWAKI (Kyushu Institute of Technology）, Shouichiro IIO (Shinshu University), Ayumu  INASAWA (Tokyo Metropolitan University), Satoshi KIKUCHI (Gifu University) Instantaneous 3D-CT(Computer Tomography) measurements with instantaneous multi-directional photography for unsteady flame/flow phenomena; and 3D printing of 3D reconstructed distributions Yojiro ISHINO (Nagoya Institute of Technology） Simultaneous Measurement of Velocity and Heat Transfer in Unsteady Flow and Thermal Fields near the Wall Region Shunsuke YAMADA, Hajime NAKAMURA (National Defense Academy）

 

Energy transfer and drag reduction in the fluid diluted with non-affine polymers

Kiyosi HORIUTI Tokyo Institute of Technology

Abstract

We conduct multi-scale study on energy transfer due to polymers dispersed in homogeneous isotropic turbulence in elasto-inertial regime (EIT). Effect of introduction of non-affinity with macroscopically-imposed deformation in the motion of polymers is examined by connecting mesoscopic Brownian dynamics of elastic dumbbells to macroscopic DNS for solvent. The dumbbells are allowed to be advected either affinely (contravariant) or completely non-affinely (covariant). The relaxation time of polymer is in the order of eddy turnover time. Contravariant polymers drain more energy from the large scales than they can dissipate and transfer the excess energy back into the solvent when they are highly-stretched. It is shown that the skewness of strain-rate tensor in the production term for elastic energy and dissipation rate transfer elastic energy back into the smallest scale of the solvent and increase the dissipation. In the covariant polymers, this backward transfer is eliminated and elastic energy is retained when highly stretched.

 

Key words

Drag reduction, Polymer, Toms effect, Non-affinity, Dumbbell model, Contravariance, Covariance.

 

Figures

Joint p.d.f. between the dumbbell length |R|² and the production term for polymer elastic energy, P_e .
Left: obtained from the case using the contravariant dumbbells;
Right: from the case using the covariant dumbbells_-