Forced convection heat transfer from the helically twisted elliptic cylinder inspired by a daffodil stem

The present study is an original research for the forced convection heat transfer around a helically twisted elliptic (HTE) cylinder inspired by a daffodil stem. Also, this study is an initial investigation to find the effect of the Reynolds number (Re) in the laminar flow regime. We carried out numerical simulations to investigate the flow and heat transfer around the HTE cylinder in 60 <= Re <= 150 and Prandtl number (Pr) of 0.7. The circular cylinder is considered for the purpose of the comparison. The drag and lift fluctuation for the HTE cylinder are much smaller than those of the smooth cylinder. The decreasing rate of Strouhal number (St) for the HTE cylinder to that for the smooth cylinder is about 4-7% in the present Reynolds number range. The smaller St of the HTE cylinder than the smooth cylinder associate a longer vortex formation length of the HTE cylinder. The three-dimensional (3D) geometry of the HTE cylinder formed the spanwise variation of the Nusselt number (Nu), resulting in the sinusoidal profiles. This span wise variation of the Nusselt number is identified by the flow structures and the isotherms distribution. The time- and total surface-averaged Nusselt number of the HTE cylinder decreases from about 1.2% to 2.8% in the present HTE configuration and Re range, compared to the smooth cylinder. (C) 2017 Elsevier Ltd. All rights reserved.