Impact of a Cold Control Plate on Fluid Flow and Heat Transfer across an Isothermally Heated Rotary Oscillating Circular Cylinder

Abstract

The main objective of this paper is to study the effect of a cold, vertical, arc-shaped control plate on the flow characteristics and forced convective heat transfer mechanism across a rotary oscillating, isothermally heated circular cylinder. Two-dimensional, unsteady, incompressible, laminar, and viscous flow of a Newtonian, constant property fluid is considered across the cylinder. The simulations are performed with an in-house code for various gap ratios between the control plate and the cylinder ($0\leq d/R_0 \leq 3$), maximum angular velocity ($0.5\leq \alpha_m \leq 4$) and frequency ratio of oscillation ($f/f_0=0.5,\ 3$) at Prandtl number $0.7$ and Reynolds number $150$. Here, $d$ denotes the gap between the surface of the cylinder and the leading surface of the control plate, $R_0$ denotes the radius of the cylinder, $f$ is the frequency of oscillation and $f_0$ is the frequency of natural vortex shedding. $d/R_0=0$ corresponds to the no plate case. Heat transfer and vortex shedding phenomena are discussed in relation to one another. A significant increase in heat transmission is observed for all $\alpha_m$ with the gap ratio of $d/R_0=0.5$ and $f/f_0=0.5$. The heat absorption on the surface of the control plate decreases to zero with increasing gap ratio when $\alpha_m=0.5$ and $f/f_0=0.5$ but never becomes zero when $\alpha_m=4$ and $f/f_0=3$. Additionally, when compared to the no plate case with $(\alpha_m,\ f/f_0)=(0.5,\ 0.5)$, the maximum peak of the drag coefficient is decreased by $9.877\%$ for the gap ratio of $d/R_0=3$. For $\alpha_m=4$ and $f/f_0=3$, the smallest gap ratio of $d/R_0=0.5$ is found to significantly increase the lift coefficient relative to other cases.