Effect of variable pitch on forced convection heat transfer around a helically twisted elliptic cylinder

The present study numerically evaluated the performance of the variable pitch helically twisted elliptical (VPHTE) cylinder on the forced convection heat transfer at the Reynolds number of 30 00 by employing a large eddy simulation (LES). A parametric study on the variable pitch ratio (VP) and the simulations of the smooth and the helically twisted elliptical (HTE) cylinders for the purpose of the comparison were performed. The present results validated the VPHTE disturbance as the passive flow control to achieve the drag reduction and the suppression of the lift fluctuation, which is consistent with the findings of previous research. The VPHTE cylinders provided smaller values of total surface-averaged Nusselt number over the time than the smooth and HTE cylinders. In addition, the VPHTE cylinders considerably stabilized the time series of total surface-averaged Nusselt number. The VPHTE and HTE cylinders formed the regions containing the local peaks of time -averaged Nusselt number build the inclined elliptic formation with the center at the front stagnation point of the node. The distribution of the temperature contours clearly reflects the stably elongated shear layers and the delay of the vortex shedding due to the geometric disturbances of the HTE and VPHTE cylinders. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study numerically evaluated the performance of a variable pitch helically twisted elliptical cylinder through large eddy simulation for forced convection heat transfer. The results showed that the VPHTE cylinder can reduce drag, suppress lift fluctuation, and provide smaller total surface-averaged Nusselt numbers over time compared to smooth and HTE cylinders. The VPHTE and HTE cylinders formed inclined elliptical shapes with local peaks of time-averaged Nusselt numbers, and the temperature contour distribution reflected stably elongated shear layers and delayed vortex shedding.