Computational Studies of Heat Transfer in Turbulent Wavy-Channel Flows

Abstract

Heat transfer is studied in fully-developed turbulent flows through channels with various geometries using Direct Numerical Simulations (DNS). Channels where a sinusoidal wave is mapped on either the streamwise direction or spanwise direction are studied, and comparisons to a simple rectangular channel are provided. The velocity-components fields of the fluid flow, and pressure fields are analyzed, along with the vorticity generated in the flow, and are utilized in tandem with the Nusselt number calculated along the heat transfer boundaries, to derive a clearer description of the heat transfer performance of the various geometries. The geometries that have a sinusoidal wave mapped along the spanwise direction and not along the streamwise direction showed the poorest heat transfer performance, as exhibited by the lowest average Nusselt number. The performance of two channels, with an in-phase and out-of-phase sinusoidal wave mapped along the streamwise direction exhibited heat transfer performance significantly higher than that shown by the rectangular channel, which served as baseline. The heat transfer differences can be largely attributed to the vorticity generation and superior fluid mixing that is generated by the periodic streamwise mapped sinusoid. Streamwise sinusoidal channels exhibit Nusselt numbers that are more than three times greater than the spanwise mapped sinusoid, and almost three times greater than that of the rectangular channel. It is shown that the difference among an in-phase and out of phase wave mapping exists, but is shown to be minimal. Further exploration regarding potential geometries with various phase shifts, non-rounded corners, and longer simulation times would be beneficial.