DOI: 10.1615/THMT-18
ISBN Print: 978-1-56700-468-7
ISBN Online: 978-1-56700-467-0
ISSN Print: 2377-2816
Computational study of heat and fluid flow around a rotary oscillating cylinder at a high Re number
SINOPSIS
The paper deals with flow over a rotationally oscillating cylinder at a subcritical Reynolds number (Re = 1.4×105) that is an order of magnitude higher than previously reported in the literature. The focus is on the control of drag force and heat transfer. Five forcing frequencies ƒ = ƒe/ƒ0 = 1, 2.5, 3, 4, 5 and three forcing amplitudes Ω=ΩeD/2U∞ = 1, 2, 3 are considered, where ƒo is the natural vortex-shedding frequency, U∞ the free-stream velocity and D the cylinder diameter. We employed 3D URANS based on a second-moment closure, which was earlier verified by LES and experiments on flows over a stagnant, as well as two cases of rotary oscillating cylinders at the same Re number. The dramatic drag reduction occurs at frequencies equal and larger than ƒ = 2.5, while no reduction appears for the cylinder that oscillates with the natural frequency. The drag reduction is the result of a modified vortex shedding topology and related pressure field characterized by shrinking of the low pressure region behind the cylinder, all imposed by the rotary oscillation. The heat transfer from a cylinder wall is enhanced by the rotary oscillation resulting in the local Nusselt number which distribution along the cylinder wall strongly depends on the forcing amplitude and frequency.