Experimental Investigation of Tip Vortex Control Using a Half Delta Shaped Tip Strake

The effectiveness of using a half delta wing tip strake for static wing tip vortex control and performance enhancement was investigated. The flowfield over the wingtip and in the near-field was studied over a low aspect ratio NACA 0012 wing fitted with a half delta wing with a leading-edge sweep of 64° at a chord Reynolds number of 3 × 105. The incidence of the strake relative to the main wing was movable allowing for strake settings from δ = -10° to +10°. Force balance data supplemented with flowfield measurements were used to investigate the performance improvements with the addition of the strake and to understand the interaction between main wing and strake. Velocity and vorticity fields were compared to the clean rectangular planform wing (baseline wing), a sharp 64° sweep half delta wing and full delta wing for direct comparison and to better understand the flow physics involved. The effect of streamwise location, angle of attack and strake setting were examined. Particular attention was paid to the strength, size and development of the strake vortex and ensuing trailing vortex. It was found that the strake behaves much like a delta wing albeit with a strengthened LEV that prematurely breaks down. The broken down LEV then results in a tip vortex which is much more diffused than its baseline counterpart. In order to quantify this effect, the Maskell model was used to calculate the induced drag of both the baseline wing and the strake equipped wing at various angles of attack and strake settings. The results indicated that the addition of the strake reduces the induced drag particularly at high lift coefficient.