When fluid flows past a bluff body, alternating vortex shedding (the Kármán vortex street) occurs once the Reynolds number exceeds a certain range (Re  50-100). This vortex shedding leads to significant engineering issues such as vibration, noise, increased drag, and structural fatigue [1-2]. Therefore, “vortex suppression” is critically important across many engineering applications [3]. In this paper, we employed CFD to study the vortex suppression by blowing and suction on the surface of a circular cylinder surface over which a uniform flow is past, shown in Fig. 1. The Reynolds number based on the diameter, D = 2R, and uniform incoming flow velocity, U, is 100. The ratio of blowing/suction velocity to the incoming flow velocity (V/U) is 5. We specified three different values of b and s, respectively. They result in a total of nine possible combinations for flow investigations in the present study. The computational results show many interesting features. In some cases, the vortex is effectively suppressed and the flow becomes steady. These cases can be further divided into two sub-categories, one with a recirculation region and the other without a recirculating region. For the cases involving vortex shedding, some exhibit single-sided shedding, while others exhibit double-sided shedding. Further, the Strouhal number varies for each case. For some cases, it is bigger than the one without blowing/suction while for others, it is smaller. As for the drag, only one case resulted in a reduction of drag among the nine combinations; for all other cases, drag increased. This could be attributed to excessively high blowing or suction velocities. REFERENCES [1] B.M. Sumer, Hydrodynamics around cylindrical structures, World Scientific, 2006. [2] C.H.K. Williamson, Vortex dynamics in the cylinder wake. Annual Review of Fluid Mechanics, Vol. 28, pp. 477-539, 1996. [3] X. Mao, H.M. Blackburn, and S.J. Sherwin, Nonlinear optimal suppression of vortex shedding from a circular cylinder. Journal of Fluid Mechanics, Vol. 775, pp. 241-265, 2015.