Numerical investigation of vortex induced vibration effects on the heat transfer for various aspect ratios ellipse cylinder.

The vortex-induced vibration of various aspect ratio (AR = 0.75 , 1.0 , 1.25 and 1.5) ellipse cylinders with convective heat transfer is investigated at Re = 150 and m ∗ = 10 for 3 ≤ U r ≤ 12 , where U r = U / (f n D) and f n is the natural frequency of cylinder in still air. The amplitude and frequency response of displacement, force and the Nusselt number are presented and discussed, the vorticity, temperature contours and wake patterns are studied to understand the effect of AR and U r on the 1DOF vibration characteristics and the heat transfer of the isothermal cylinder. The results show that the classical Karman shedding (2S) is observed at relative low displacement and the C(2S) occurs when the cylinder undergoes high-amplitude oscillations for the AR considered, and the P+S wake mode which is composed with a single vortex and one pair of counter-rotating vortices during the transition from the initial branch to the VIV lock-in regime. There are multiple frequencies related to the response of Nusselt number, with the 2 S t N u dominating. And the maximum value of N u A is 11.07, 11.7, 12.1 and 12.35 for AR = 0.75 , 1.0 , 1.25 and 1.5 respectively, which are increased by 7%, 8.7%, 11% and 13.5%, respectively, compared with the corresponding stationary cylinders, indicting an enhanced heat transfer of VIV cylinder. As increasing of the AR to 1.5, an early exit of the VIV lock-in regime and into the desynchronized regime happens due to the strong 2 S t n in the lift frequency response when. [ABSTRACT FROM AUTHOR]