Modeling Simulation and Characterization of Flow Control of Vortex Shedding using Synthetic Jet Actuator

Abstract

A swirling pattern of vortices is experienced in the wake of a fixed body which is creditworthy for the generation of oscillating hydrodynamic forces and the variations on the structure. These variations usually cause grievous structural vibrations, which may result in a structural failure. Anti shedding or shedding control devices are required to protect the structure and to minimize the shedding intensity. A parallel 3D CFD solver is used to simulate the flow past a cylinder via Synthetic jet actuator. The primary objective of this manuscript and research is to form a technique of active flow control of vortex shedding of a circular cylinder at low Re and hence to reduce the lift and drag forces associated with it. To suppress the vortex shedding, the control strategy is implemented using Synthetic Jet Actuator at rear stagnation point developed by projecting the Navier-Stokes equations. The synthetic jet vortex pair is induced at the downstream by continuous blowing and suction. The flow control is realized by oscillating the diaphragm about its axis with dimensionless actuation frequency. This numerical study will lead to an interesting phenomenon that is each synthetic jet vortex pair could induce a new wake vortex pair with a symmetric shedding mode by suppressing its lift coefficient. The analysis which we have done for the inline oscillating cylinder is compared with the analysis of the flow past a cylinder via synthetic jet actuator. In this work we have discussed the nonlinear behavior and periodicity responses of fluid forces for the pre and post synchronization region as well as in the synchronization region. Moreover, we conclude how iii the drag and lift coefficients are varied in a way in which the actuation frequency of the oscillating diaphragm is variegated: n-periodic, quasi-periodic and chaotic. We have found that in this frequency band on some particular values the lift vanishes its magnitude to a very small scale. The simulations were performed using three types of profiles: Top hat, Sine and Sine Square. By selecting the oscillating diaphragm as top hat profile, lift amplitude decreases abruptly resulting in a complete suppression of lift coefficient, whereas the mean drag drops and remains constant at a value that is independent of the actuation frequency. The lift and mean drag is reduced by 87.5% and 39% respectively. We perform spectral analysis to analyze the coupling between the lift and drag below and above that frequency and compare several features of the synchronization.