Numerical investigation of the heat transfer and flow pattern on tandem triangle-grooved cylinders

Abstract

Modifying surface characteristics and geometric structure to regulate heat transfer and flow fields is a classical issue. The study of wake dynamics and heat transfer efficiency in tandem grooved cylinders hold fundamental importance. This research proposes a configuration of tandem cylinders with triangle-grooved surfaces and numerical simulates the vorticity, fluid forces, Strouhal numbers, and convective heat transfer in tandem grooved cylinders. The parameters investigated include orientation angles θ = 0°, 30°, 45°, 60°, 90° and Reynolds numbers Re = 75, 100, 125, 150, 175, 200. This study focuses on how the triangle-grooved angle (θ) and Re affect wake dynamics and thermal performance. Numerical results are validated against available data in the literature for tandem smooth and tandem grooved cylinders. The results indicate that, compared to tandem smooth cylinders, the positive vorticity intensity of tandem grooved cylinders is 35.7 % higher, while the negative vorticity intensity is 23.5 % lower. Further observations show that at θ = 45°, the pressure variation on the upstream cylinder is most significant, approximately twice that at θ = 0° and θ = 90°. Notably, the variation values of the downstream cylinder (β = 0°) at θ = 0° and θ = 45° are triple and double that of the upstream cylinder in TF mode, respectively. Additionally, at θ = 0°, the root mean square lift coefficient of the downstream cylinder reaches the maximum value (Re = 75–100), approximately 1.34. When Re = 125, CL(rms),1 decreases by 15.7 % to 1.13. Particularly, when Re = 100–150, the time-averaged drag coefficient of the downstream cylinder shows a peak value of approximately 1.02. Interestingly, at Re = 200, a tadpole-shaped thermal distribution forms in the wake region of the upstream cylinder. Furthermore, the time-averaged Nusselt number ratio (θ = 0°) exhibits a trend opposite to other cases over a broader range (125 ≤ Re ≤ 200) and peaks at Re = 200, approximately 1.24.

Keywords

• Tandem grooved cylinders
• Heat transfer
• Wake
• Flow control
• Force coefficients and nusselt number