Based on the immersed boundary method

the suppression of vortex shedding around a main circular cylinder by another small control cylinder was numerically studied. The flow was computed on non-body conformal Cartesian grid

which was suitable for problems with complex boundaries. The discrete forcing direct boundary condition imposition could impose boundary condition on immersed boundary accurately. An implicit fractional step method on collocated grid was used to solve the two-dimensional unsteady incompressible Navier-Stokes equations

and improve its computational efficiency by decoupling of velocity and pressure. The numerical simulations included the flow over a cylinder and the flow interference between a main circular cylinder and another small control cylinder located at two different positions. From analysis on the vortex structure of flow fields and the lift and drag coefficients

the delay and complete suppression of vortex shedding behind the main circular cylinder was found. All the calculated results agreed well with the previous experiment and numerical results

with the error not exceeding 5%. This indicates the immersed boundary method could be simply and efficiently used for numerical simulation on suppression of vortex shedding.