Active control and drag optimization for flow past a circular cylinder I. Oscillatory cylinder rotation

The main objective of this article is to investigate computational methods fur the active control and drag optimization of incompressible viscous flow past cylinders, using the two-dimensional Navier-Stokes equations as the Row model. The computational methodology relies on the following ingredients: space discretization of the Navier-Stokes equations by finite element approximations, time discretization by a second-order-accurate two-step implicit/explicit finite difference scheme, calculation of the cost function gradient by the adjoint equation approach, and minimization of the cost function by a quasi-Newton method a la BFGS. The above methods have been applied to boundary control by rotation of the flow around a circular cylinder and show 30 to 60% drag reduction, compared to the fixed cylinder configuration, fur Reynolds numbers in the range from 200 to 1000. (C) 2000 Academic Press.