Introduction of a biomimetic device designed to improve the flow over a slender delta wing: visualization study

One of the factors significantly influencing the flow structures and vortices formed on delta wings is the shape of the leading edge. This study examined the impact of needle vortex generators, inspired by owl wings, on the flow characteristics over a slender delta wing with a sweep angle of 65° to improve its aerodynamic performance. These nature-inspired vortex generators were designed to apply no additional flow blockage or drag force. Flow visualization tests were conducted in a smoke tunnel to gain deeper insights into the effects of the vortex generators on the flow physics over the delta wing. The experiments were performed at three angles of attack of 10°, 15°, and 20° and a flow velocity of 2.6 m/s on two delta wings, with and without needle vortex generators at the leading edge and a Reynolds number of Re = 2.6 ×  \({10}^{4}\) ${10}^4$ . Flow visualization was conducted on six longitudinal sections, six transverse sections, one-floor surface section, and one leading edge section at three different angles of attack. In addition, the investigation involved assessing the vortex breakdown location and wake region. The formation of the vortices and the effects of the needle vortex generators on the temporal and instantaneous flow structures and vortices were also investigated. The results suggested that the use of the needle vortex generators along the leading edge of the delta wing made the vortices smaller and closer to the wing surface and wing axis, postponed the vortex breakdown by approximately 13% of the chord length, and decreased the fluctuations of vortex breakdown location. In addition, the use of needle vortex generators eliminated the secondary vortices.