Passive scalar transport in polymer drag-reduced turbulent channel flow

• Published in: AIChE journal Vol. 51; no. 7; pp. 1938 - 1950
• Main Authors: Gupta, V. K., Sureshkumar, R., Khomami, B.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-07-2005; Wiley Subscription Services; American Institute of Chemical Engineers
• Subjects: Applied sciences; Chemical engineering; Exact sciences and technology; FENE-P; Heat and mass transfer. Packings, plates; Heat transfer; heat transfer reduction; Organic polymers; passive scalar; Physicochemistry of polymers; Polymer processing; Properties and characterization; Simulation; Solution and gel properties; Turbulence; turbulent drag reduction; viscoelastic; heat transfer reduction; Pipe flow; Heat pump; Stabilization; Heat flow; Momentum; Reynolds stress; Transport process; Prandtl number; Polymer solutions; Drag reduction; Drag; turbulent drag reduction; Numerical simulation; passive scalar; Diffusion coefficient; Channel flow; FENE-P; viscoelastic; Heat transfer
• ISSN: 0001-1541; 1547-5905
• DOI: 10.1002/aic.10465

Passive scalar transport in turbulent channel flow of viscoelastic dilute polymer solutions exhibiting drag reduction (DR) is studied using direct numerical simulations for DR values up to 74.0%. DR is accompanied by the stabilization of low‐speed streaks in the buffer layer that are primarily responsible for the streamwise heat transport. Moreover, as DR increases, the Reynolds stress and the root mean square fluctuations in the wall‐normal and spanwise velocity components decrease. Thus, as DR is increased, streamwise heat flux increases, whereas both wall‐normal and spanwise heat fluxes decrease. Consequently, for large DR values, the flow acts as a highly efficient heat pump. The turbulent Prandtl number, defined as the ratio of the eddy diffusivities of momentum to heat, increases from its Newtonian limit of unity to a value that exceeds the molecular Prandtl number for DR = 74.0%. This experimentally well documented phenomenon is predicted using first‐principle simulations for the first time in this work. © 2005 American Institute of Chemical Engineers AIChE J, 2005