Fish scale inspired materials could reduce aircraft drag

Through a study, which is published in the journal Nature: Scientific Reports, a team led by the University’s Professor Christoph Bruecker discovered that the fish-scale array produces a zig-zag motion of fluid in overlapping regions of the surface of the fish. This causes periodic velocity modulation and a streaky flow that can eliminate Tollmien-Schlichting wave induced transition to reduce skin friction drag by more than 25 per cent.

An examination of oil flow visualisation using computational fluid dynamics (CFD) on sea bass and common carp enabled the authors to come up with a working hypothesis.

"Computation Fluid Dynamics was used to study the flow pattern over the surface and revealed a hitherto unknown effect of the scales as a mechanism to generate a regular pattern of parallel streamwise velocity streaks in the boundary layer,” write the authors. “To prove their existence also on the real fish skin, oil flow visualisation was done on sea bass and common carp, which indeed confirmed their presence in a regular manner along their real body, with the same arrangement relative to the scale array as observed along the biomimetic surface. These results let the authors hypothesise about a possible mechanism for transition delay, inspired by various previous fundamental transition studies, where streaky structures generated by cylindrical roughness elements or vortex generator arrays have shown a delay of transition".