CONICET | Buscador de Institutos y Recursos Humanos

Direct numerical simulations (DNS) of incompressible flows past a rotating cylinder placedin a uniform stream are performed using the virtual boundary technique to model the presenceof the obstacle. The numerical code that allows us to perform these simulations uses sixthordercompact centred difference schemes to evaluate spatial derivatives, while time integrationis performed with a third-order low-storage Runge Kutta method. The Reynolds number basedon the cylinder diameter and free-stream speed of the flow is 200 (corresponding to the wake transition regime). The non-dimensional rotation rate, (ratio of the surface speed and freestream speed), is varied between 0 and 3. Performed simulations allow to make the comparison with published experimental and numerical results about the influence of the rotation rate on the process of vortex shedding behind the cylinder. Extension of the computations to dimensionless times larger than achieved in previous studies allows for a more complete description of the temporal development of the wake, and a better estimation of drag and lift coefficients that characterizes the Magnus effect. The present results seem to indicate the existence of a critical value between 1.95 and 2 beyond which the vortex shedding ceases. For higher rotation ratesthe flow achieves a steady state. The incompressibility condition is ensured with a fractional stepmethod via the resolution of a Poisson equation for the pressure. This task generally consumesmost of the time of integration in a DNS. In order to reduce the excessive computational costassociated to the analysis of long transients on a single PC, a parallel version of the simulationcode was developed using the domain decomposition technique applied to the resolution ofPoisson equation in conjunction with the message passing interface (MPI).

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