Extended Data Fig. 10: Noise abatement by surface treatments.
From: Adaptations for stealth in the wing-like flippers of a large ichthyosaur
a, b, Vortex structures visualized using the Lambda2 method for serrated flipper geometries covered with either (a) ridges or (b) troughs at 0° α. c–h, Average velocity fluctuations for serrated hydrofoils exhibiting either (d, g) ridges or (e, h) troughs, compared against (c, f) a smooth (but serrated) model at (c–e) 0 and (f–h) 5° α, respectively. i, Comparison of SPL 5 (solid lines) and 250 m (dashed lines) upstream of a serrated flipper section covered with either chordwise ridges (blue lines) or troughs (green lines), compared against a smooth (but serrated) geometry (black lines) at 0° α. j, Comparison of SPL 5 (solid lines) and 250 m (dashed lines) upstream of a serrated flipper section covered with either chordwise ridges (blue lines) or troughs (green lines), compared against a smooth (but serrated) geometry (black lines) at 5° α. Data were collected for 67.5 convection times. Spectra in i and j are based on 65,536 wide Hanning windows, 50% overlap and 33 samples.
