Geometry modification effects on a junction vortex flow

Abstract

The effects of geometry modifications on some properties of time-resolved flow measurements on the upstream symmetry plane of a junction vortex region were studied. A single linearized hot-wire was used to characterize the spatial distribution of the fluctuating flow turbulent kinetic energy. The distribution was integrated to give a measure of the turbulent kinetic energy content of the flow region where the largest fluctuations were seen in real-time smoke visualizations. The wire signal was also used for spectral estimations throughout the flow field.

Six different cases were considered including a reference case with no geometry changes. The geometry modifications consisted of a large circular wraparound fillet, a small elliptic wraparound fillet, a small circular wraparound fillet, an upstream flow fence and, a large leading-edge triangular fillet. In the smoke visualizations, none of the modifications had any significant effect except the large triangular fillet which resulted in a reduced vortex structure. The large triangular fillet also appeared to be the most effective in significantly reducing the integrated turbulent kinetic energy. With regard to the turbulent kinetic energy, the elliptic wraparound fillet had an insignificant effect while the large and small wraparound fillets and the vortex generator fence had adverse effects.

The spectra obtained over the flow field suggest that the upstream turbulent boundary layer was the driving force behind the junction vortex time-variant behavior. An examination of the low frequency end of the spectra suggests a weak local peak at about 11 Hz for the flow between the upstream separation point and the average vortex center.