The effects of flexible vortex generator on the wake structures for improving turbulence

Abstract

Abstract Turbulence is a very useful flow characteristic that is used in many engineering devices to facilitate mixing, heat transfer in heat exchanger and improving aerodynamics in propeller. This paper has numerically studied the spatial characteristics of the wake behind a free-oscillating flexible vortex generator (FVG) in order to evaluate its turbulence generation ability. As the wake is playing as the effective turbulence region, the spatial characteristics can reflect the ability of the FVG in turbulence generation when a larger wake size indicates a greater turbulence region. Two VGs are considered in this study; circular and flat plate cantilever. Each VG was submerged individually in a subcritical flow (102 <ReD < 105) and the generated wake was studied. The wake behind the FVG was visualized via the lambda2 vortex identification criterion and it was compared with its respective rigid counterpart. From the comparison, it is found that the FVG has a larger wake compared to its rigid counterpart. The result demonstrates that the FVG can generate a larger turbulence region. The cause of the increasing wake size was found to be the weakening of downwash behind the FVG when it bends. The downwash becomes weaker as the deflection of the FVG increases.