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

摘要

Highlights•A helically twisted elliptic (HTE) cylinder based on biomimetic is considered.•The forced convection around theHTEcylinder is originally investigated.•The effect ofReon the flow around theHTEcylinder is initially researched.•The local Nu identifies the effect of theHTEgeometry on the heat transfer.AbstractThe 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 theHTEcylinder in60⩽Re⩽150and 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 theHTEcylinder to that for the smooth cylinder is about 4–7% in the present Reynolds number range. The smallerStof theHTEcylinder than the smooth cylinder associate a longer vortex formation length of theHTEcylinder. The three-dimensional (3D) geometry of the HTE cylinder formed the spanwise variation of the Nusselt number (Nu), resulting in the sinusoidal profiles. This spanwise variation of the Nusselt number is identified by the flow structures and the isotherms distribution. The time- and total surface-averaged Nusselt number of theHTEcylinder decreases from about 1.2% to 2.8% in the presentHTEconfiguration andRerange, compared to the smooth cylinder.