Title: DNS on turbulent heat transfer of viscoelastic fluid flow in a plane channel with transverse rectangular orifices
Authors: Takahiro Tsukahara; Tomohiro Kawase; Yasuo Kawaguchi
Addresses: Department of Mechanical Engineering, Tokyo University of Science, Yamazaki 2641, Noda-shi, Chiba, 278-8510, Japan ' Department of Mechanical Engineering, Tokyo University of Science, Yamazaki 2641, Noda-shi, Chiba, 278-8510, Japan ' Department of Mechanical Engineering, Tokyo University of Science, Yamazaki 2641, Noda-shi, Chiba, 278-8510, Japan
Abstract: Heat-transfer characteristics of a viscoelastic turbulence past rectangular orifices were investigated in the context of the reduction effects of fluid elasticity on drag and heat transfer. To simulate the fully-developed channel flow through transverse orifices located periodically at intervals of 6.4 times channel height, we imposed periodic conditions at the upstream and downstream boundaries. To discuss the dissimilarity between the velocity and thermal fields, the molecular Prandtl number was set to be 1.0 and any temperature dependence of the fluid and rheological properties was not considered. In the present condition, the ratio of the reduction rates in drag and heat transfer was found to be 2.8:1.0, revealing that the present flow configuration is better than a smooth channel for avoiding the heat-transfer reduction. This phenomenon was attributed to the sustainment of the quasi-streamwise vortex downstream of the reattachment point despite the absence of strong spanwise vortices emanating from the orifice edge in the viscoelastic fluid. The longitudinal vortices behind the reattachment point caused a high turbulent heat flux and increased the local Nusselt number.
Keywords: channel flow; direct numerical simulation; DNS; drag reduction; Giesekus model; immersed boundary method; Kelvin-Helmholtz instability; non-Newtonian fluids; viscoelastic fluid flow; plane channels; transverse orifices; rheology; heat-momentum dissimilarity; Toms effect; turbulence control; turbulent heat flux; heat transfer reduction; fluid elasticity; reattachment point; vortices.
Progress in Computational Fluid Dynamics, An International Journal, 2013 Vol.13 No.3/4, pp.212 - 223
Received: 08 May 2021
Accepted: 12 May 2021
Published online: 22 Apr 2013 *