Effective methods of controlling a junction vortex system in an incompressible, three-dimensional, turbulent flow

An experimental investigation was conducted to find effective methods of controlling a junction vortex system around and in the wake of a NACA 0020 body with a 1.5:1 elliptical nose mounted normal to the flat surface. Control of the junction vortex system was investigated using more slender noses and leading edge fillets. The study includes surface flow visualizations, and extensive mean flow measurements. The mean flow measurements consist of velocity, total pressure, and static pressure distributions.

The results of the mean flow measurements around and in the wake of a NACA 0020 body with a 1.5:1 elliptical nose show the presence of a large, dominant vortex, or a primary horseshoe vortex, in the junction between the body and the flat surface. A smaller, co-rotating vortex relative to the primary horseshoe vortex was observed at the 100 percent chord position, which is believed to be identified with the corner separation at the junction near the trailing edge.

Mean flow measurements of the flow field around and in the wake of a NACA 0020 body with more slender noses were acquired. The results indicate that the more slender nose generated a weaker primary horseshoe vortex. The results also suggest that the weak primary horseshoe vortex developed by the more slender nose was dissipated alongside the body to the point where it had a very small effect on the flow field at the 100 percent chord position.

The results of the mean flow measurements around and in the wake of a NACA 0020 body with a 1.5:1 elliptical nose with leading edge fillets indicate that the leading edge fillets were very effective in reducing the strength and size of the primary horseshoe vortex. The results suggest that an effective fillet should be about one boundary layer thickness high and two body thicknesses long.

The vorticity identified with the corner separation vortex was observed in the wake for both leading edge shape changes and fillets. The results show that the corner separation vortex dominates the flow in the wake due to the weak effects of the primary horseshoe vortex. A trailing edge fillet was used to investigate its effects on the corner separation vortex in the wake of the NACA 0020 body with the 1.5:1 elliptical nose with a leading edge fillet. The results indicate a small decrease in the strength of the comer separation vortex at the 150 percent chord position, but the effects on the wake pattern were small.