Wake control using spanwise-varying vortex generators on bridge decks: A computational study

Abstract

A passive control device called spanwise-varying vortex generator (VG) is proposed to mitigate vortex shedding of a bridge model, since the 3D spanwise-varying control method shows high efficiency in suppressing vortex shedding behind bluff bodies. Pairs of VGs were arranged on the lower surface of the bridge in the spanwise direction to generate streamwise vortices and perturb two-dimensional spanwise vortex shedding. Delayed detached-eddy simulation and dynamic mode decomposition were carried out to examine their effects on wake control. The results demonstrate that with VG control, the regular spanwise vortices are highly distorted and are accompanied by a spanwise mismatch in the vortex shedding process. Consequently, the regular spanwise vortex shedding is substantially suppressed, resulting in a considerable reduction in vortical strength in the wake and significant increases in the vortex formation length. In addition, the dynamic mode decomposition reveals that VGs can redistribute the energy spectrum and transport the energy from the mode associated with the regular vortex shedding to other low-frequency modes. Therefore, forces induced by vortex shedding are considerably reduced.