An experimental investigation of flow and stall characteristics of bio-inspired leading edge wing protuberances
Jensen, Adrian (2026)
Kandidaatintyö
2026
School of Energy Systems, Konetekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe20260618100409
https://urn.fi/URN:NBN:fi-fe20260618100409
Tiivistelmä
Leading-edge tubercles, inspired by the humpback whale flipper, have been proposed as a passive means of improving wing stall behaviour. Existing studies consist largely of numerical studies or based on force measurements, where experimental data on chordwise surface pressure distribution of a tubercled wings at low Reynolds number remain scarce. This thesis measures that distribution and compares it directly with an equivalent smooth wing.
Two NACA 4424 wings were tested, one with a standard baseline profile, and one with a sinusoidal leading edge, were tested in a low-speed wind tunnel at a chord Reynolds number of 2.5∙10^5. The surface pressures were measured through embedded pressure taps using an inclined multi-tube manometer across angles from 0° to 30°, with the bio-inspired wing measured at both crest and trough locations to resolve spanwise variation.
The baseline wing showed the pressure distributions expected of a cambered airfoil, with peak loading agreeing in magnitude with published data for the same section. The principal result is a strong spanwise variation in leading-edge pressure distribution, where the trough taps exhibited strong suction while the crest showed very little, the difference being more pronounced toward the leading edge at moderate angles. In comparison, the baseline wings pressure coefficient values fell between that of the crest and trough, indicating that the tubercles redistribute the leading-edge loading spanwise rather than altering it uniformly.
The measurements were limited by wind tunnel blockage effects, and by unsteady high-angle pressures, which causes the baseline to appear to stall above its true angle, and by a forward-chord bias of the tubercled wing. The results provide experimental evidence of the spanwise pressure redistribution produced by leading edge protuberances at low Reynolds numbers.
Two NACA 4424 wings were tested, one with a standard baseline profile, and one with a sinusoidal leading edge, were tested in a low-speed wind tunnel at a chord Reynolds number of 2.5∙10^5. The surface pressures were measured through embedded pressure taps using an inclined multi-tube manometer across angles from 0° to 30°, with the bio-inspired wing measured at both crest and trough locations to resolve spanwise variation.
The baseline wing showed the pressure distributions expected of a cambered airfoil, with peak loading agreeing in magnitude with published data for the same section. The principal result is a strong spanwise variation in leading-edge pressure distribution, where the trough taps exhibited strong suction while the crest showed very little, the difference being more pronounced toward the leading edge at moderate angles. In comparison, the baseline wings pressure coefficient values fell between that of the crest and trough, indicating that the tubercles redistribute the leading-edge loading spanwise rather than altering it uniformly.
The measurements were limited by wind tunnel blockage effects, and by unsteady high-angle pressures, which causes the baseline to appear to stall above its true angle, and by a forward-chord bias of the tubercled wing. The results provide experimental evidence of the spanwise pressure redistribution produced by leading edge protuberances at low Reynolds numbers.