Transient Response Characteristics of Separated Flow and Heat Transfer in Enlarged Rectangular Channel

Hiroyuki Yoshikawa, Shota Shirakura, Mizue Munekata

Department of Mechanical System Engineering, Kumamoto University, Kumamoto, Japan.
Graduate School of Science and Technology, Kumamoto University, Kumamoto, Japan.

DOI: 10.4236/ojfd.2012.24A033                

Abstract

Numerical results of three-dimensional separated flow and heat transfer in an enlarged rectangular channel are presented in this paper. The expansion ratio and aspect ratio of the channel are 2.0 and 8.0, respectively. Reynolds number of the flow is 200 and it is over the critical Reynolds number. Over the value, the flow in the symmetric channel becomes to deflect to one side of the walls. Transient response characteristics of the flow and heat transfer in the channel with the fully developed flow imposed one cycle of a pulsating fluctuation at the inlet are investigated. Vortex structure generated in the channel is visualized with a helicity isosurface. In the case of the fluctuation of Strouhal number 0.05, small streamwise vortices appear near the side walls and slightly upstream of the reattachment region of the short separation bubble. The vortices elongate and shed some vortices. These vortices attract some pairs of the streamwise vortices near the reattachment region quickly and they drift downstream along the side walls. They are inclined from the walls and are decaying gradually. It is clarified that high Nusselt number area appears and shifts downstream in accordance with the root of the vortices.

Keywords

Transient Response; Pulsating Fluctuation; Symmetric Enlarged Channel; Asymmetric Separated Flow; Heat Transfer

Conflicts of Interest

The authors declare no conflicts of interest.

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