Numerical simulation of an unsteady flow over a circular cylinder at high Reynolds numbers

Flow around bluff bodies such as a circular and elliptical cylinder is a challenging problem in fluid mechanics. Many engineering applications such as offshore structures, bridge piers, and pipelines can be modeled as a circular cylinder. In the present study, unsteady flow around a circular cylinder is simulated by ANSYS-Fluent 14.0 in laminar and turbulent flow regimes. The Finite Volume Method with second-order equations were applied. The coupling of pressure and velocity equations solved by the PISO algorithm. The PISO algorithm is more accurate in transient flows, also it shows vortices behind of cylinder clearer than other methods. Owing to the capability of the k-ε turbulent model, it is used in this study. In the simulation, the effects of Reynolds number’s changes on the formation and destruction period time of vortices and drag and lift coefficient have investigated. The results showed that by increasing the Reynolds number, the time of formation and destruction of vortices, as well as lift coefficient has experienced a decrease. The drag coefficient fluctuated and the overall trend was decreasing. It is crystal clear that the simulation results are in good agreement with previous results which the numerical error of the lift and drag coefficients were less than 10%.