Abstract: This paper computationally studied the turbulence characteristics of the wake behind a free-oscillating flexible vortex generator (FVG) by investigating the shear rate around the FVG using Fluid-Structural Interaction (FSI) simulation of RANS (SST) k-w model. Two vortex generators are considered in this study; a circular and a flat plate cantilever. Each vortex generator was submerged individually in a sub-critical flow (102<Re<105). Firstly, the wall shear stress generated by the FVG was found to be greater than the rigid vortex generator (RVG), which denotes that the turbulence source has become stronger when a FVG is implemented. The time-series of the wall shear stress was investigated and it was observed that the maximum wall shear stress occurred when the FVG was in motion whilst the minimum wall shear stress occurred when the FVG stopped moving. The proposed flow model suggests that the increasing wall shear stress is scaled with the structural velocity. Secondly, the vortex strength was analyzed. It was found that the FVG is capable of generating stronger vortices compared to the RVG; which in other words, the FVG has a better turbulence generation ability due to the stronger turbulence production at the boundary layer, hence better energy mixing for heat transfer enhancement.

Keywords: downwash, mixing, production term, shear stress, turbulence, URANS, vortex generator

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