Analyzing the features of self-excited oscillations generated by the flow past a circular cylinder with a splitter plate

One method to control the flow past a solid body is the placement of a flat splitter plate behind the body. The splitter destroys the hydrodynamic feedback that initiates self-excited oscillations of the flow past the body. In such a manner, the splitter performs a stabilizing role, diminishing both the average drag force applied to the body and the oscillations in the trail behind the body. In the present paper, we numerically solve the problem of the generation of self-excited oscillations in the flow past a circular cylinder with a flat splitter plate connected at the rear. Both the transient process of vortex formation and separation from the cylinder's surface and the steady self-excited flow oscillations caused by the periodic vortex shedding behind the cylinder are investigated. The evolution of the vorticity field and the streamline pattern during both the transient and steady processes is described. It is shown that the hydrodynamic feedback channel is formed through the difference in pressure on the upper and lower surfaces of the solid body. The periodic change of its sign causes a periodic process of vortex formation and shedding. It is shown that the splitter oriented along the flow direction substantially reduces both the mean drag force and the amplitude of oscillation of the forces applied to the cylinder. With increasing splitter length, the average value of the drag force decreases monotonically, but the amplitudes of oscillation of the forces applied to the body change non-monotonically. In this paper, we give our explanation of this phenomenon. The calculated data for the main flow characteristics at various splitter lengths are represented. It is also demonstrated that when turning the splitter at a comparatively small angle, the process of vortex shedding from the body surface persists, but the process is no longer strictly regular and periodic.