Numerical study of convective heat transfer of nanofluid flow over an angular oscillating circular cylinder

Fluid flow over a cylinder is appeared in differenet engineering fields. In this article, laminar, two-dimensional, incompressible and viscous CuO-water nanofluid flow around a circular cylinder with angular oscillation in unsteady regime at Reynolds numbers of 100, 150 and 200 in amplitudes of θ_A=π⁄4,π⁄2 and different oscillation frequency ratios of F=0.5, 1, 2 and volume fractions of nanoparticles in the range of 0≤φ≤0.03 is simulated numerically. Governing equations include continuity, momentum and energy equations have been solved numerically for a combined grid via finite volume method. Effective thermal conductivity and dynamic viscosity of nanofluid were estimated by Corcione empirical model. The effects of volume fraction of nanoparticles and oscillation parameters on the average heat transfer coefficient were investigated and concluded that at vortex Lock-on region, the amount of heat transfer coefficient increased significantly. The main target of this article is to determine the preference of two mechanisms of heat transfer enhancement include adding nanoparticles to the base fluid and applying oscillation to the cylinder surface. Evaluation of this two mechanisms indicates that using nanofluid in compared with applying rotational oscillation to the cylinder, leads to more heat transfer enhancement rate. Results show that heat transfer coefficient enhancement due to rotational oscillation of the cylinder at θ_A=π⁄4 and F=1 compared with the stationary cylinder in water flow is between 4.25 and 15.83%. Moreover, the amount of heat transfer enhancement of nanofluid at φ=0.03 compared with the base fluid in stationary cylinder is between 20.49 and 31.26%.