03.4 - Applied Aerodynamics
VORTEX TOPOLOGY AND CORE-UNWINDING MECHANISM IN SPIROID WINGTIP DEVICES USING LAGRANGIAN PARTICLE TRACKING
M.A. Mwasandube¹, M. Marino¹, J.L. Palmer¹; ¹RMIT University, Australia
Spiroid wingtip devices feature a closed-loop geometry that intercepts the tip vortex co-rotating structure at its formation point, redistributing rotational energy into the diffuse outer wake rather than extending effective span. This paper presents the first comprehensive quantitative characterisation of the spiroid mechanism using three-dimensional Lagrangian particle tracking (3D-LPT) with Shake-the-Box reconstruction, cross-validated against three independent Trefftz-plane wake-integral methods and data from a six-component force balance. Experiments were conducted on a tapered NACA 4416 half-span wing (root chord 360 mm, tip chord 265 mm, mean chord 313 mm, half-span 960 mm, taper ratio λ = 0.736, aspect ratio AR = 6.14, Sref = 0.300 m², Re = 3.6×10⁵ based on root chord) at angles of attack, α, of 4°, 8°, and 12° in the RMIT Industrial Wind Tunnel. Three modified configurations are compared against the flat-tip baseline. The spiroid reduces compact-core circulation by 60–73% relative to the baseline, while generating a large positive Jones–Kusunose wake-integral gap (+0.00615 at α = 4°, Jones/Kusunose ratio 6.1×) — the LPT signature of vorticity redistribution from the compact rotating core into the diffuse outer wake. Lamb–Oséen R² improves with angle of attack (0.777 → 0.980), opposite to all other configurations, confirming increasingly complete core unwinding at higher loading. The spiroid is the only device to reduce absolute drag at α = 12° (by 0.7%). A novel Jones–Kusunose diagnostic gap is introduced as a single-number mechanism discriminant applicable to any Trefftz-plane LPT dataset.
DOI: 10.71945/icas2026_0162