A numerical investigation of the convective heat transfer in confined channel flow past cylinders of square cross-section

Abstract

A numerical investigation was conducted to analyze the unsteady flow and heat transfer characteristics for cylinders of square cross-section in a laminar channel flow The study focuses on differences in the drag, lift, and heat transfer coefficients for a single and tandem pair of cylinders due to the proximity to a channel wall. Both uniform and parabolic inlet velocity profiles are considered. The cases are calculated for a fixed cylinder Reynolds number of 500 and a Prandtl number of 0.7. The heated cylinder is held at a constant temperature and is initially centered in the channel. The eddy promoter has side dimensions one-half of the downstream cylinder and is placed at a fixed distance upstream. The upstream cylinder is either located midway between the top and bottom cylinder surfaces (inline) or it is centered on the top or bottom edges (offset) of the primary cylinder. The results show that the cylinder Nusselt number decreases for both single and inline tandem cylinders as they approach the wall in a parabolic flow but remain almost constant in a uniform flow. This is primarily due to the reduced mean velocity near the wall. The time-averaged drag coefficient decreases for both single and inline tandem cylinders as they approach the wall in a parabolic flow. The presence of the upstream cylinder significantly reduces the drag on the downstream cylinder when compared to that of a single cylinder but has little affect on the cylinder lift. Additionally, the overall cylinder Nusselt number increases slightly in both uniform and parabolic flows. The Strouhal number is much larger for an inline tandem pair than for a single cylinder for all cylinder positions. The amplitude of eddy-shedding induced oscillations is significantly dampened as the cylinder(s) approach the channel wall. Offsetting the eddy promoter causes a significant reduction in the heat transfer and a large increase in the drag coefficient for the channel-centered cylinder when compared to the inline tandem case. The offset cylinder is found to slightly reduce the overall heat transfer and increase the drag from the downstream heated cylinder for the other two cross-stream locations. The study also indicates that placing the eddy promoter in higher velocity fluid increases the Strouhal number of the downstream cylinder.