Black Powa: performance and efficiency underwater

Our fins uses fluke-inspired tail ending designed to improve thrust efficiency. Our twin-lobed fin tip is designed to shed coherent vortex rings and a focused momentum jet. Behaviors observed in live dolphins with flow visualisation. That wake pattern converts more kick energy into forward thrust with less wasted swirl. By pairing the planform with tuned flex and pitch, the shape aims to maximise thrust per unit effort under water (Fish et al., 2014; Fish et al., 2018; Ayancik et al., 2020).

Representation of a dolphin fluke tail

Why the fluke-inspired tail ending hits harder with less effort ?

Dolphins move by sweeping twin-lobed flukes that shed powerful vortex rings and a focused momentum jet. Laboratory measurements on dolphins show this wake pattern delivers very high thrust for the effort, with strokes supporting body weight in “tail-stand” manoeuvres and producing kilonewton-scale forces in sprints. Our tail ending borrows and exploits those principles: a tapered, fluke-like profile that concentrates circulation at the tip, manages vortex shedding, and channels more of each kick straight into forward motion. Paired with tuned flex and pitch, this geometry is engineered to maximise thrust per unit effort in real water, not just on paper. It’s biomimicry with a purpose: turn your energy into pure acceleration.

Published literature consisting of experimental results and computational fluid dynamic numerical simulations on fluke tails are reviewed and summarised below:

·      Fish, Legac, Williams & Wei (2014, JEB) — First direct, in-water measurements of dolphin thrust using bubble digital particle image velocimetry (DPIV). The flukes shed strong vortices and a momentum jet; computed from vortex circulation via Kutta–Joukowski, thrust reached ~700 N during routine swimming and up to ~1468 N in powerful starts. Confirms dolphins generate very high forces without invoking exotic drag-reduction tricks. PubMed

Linked vortices are produced within a microbubble curtain by the oscillating motion of a dolphin’s flukes. Courtesy of Fish et al. (2014).

·      Fish et al. (2018, Fluids) — “Tail-stand” validation case: two dolphins elevate their bodies vertically; bubble-DPIV shows fluke strokes create a coherent vortex ring train and downward jet. Measured forces up to ~997 N, matching the body weight supported above the surface, validating the DPIV method for live animals. MDPI

·      Legac et al. (2008, Physics of Fluids) — Methods paper demonstrating DPIV applied to mammals (humans and dolphins). Visualizes vortex shedding and wake topology around swimming mammals, establishing practical protocols for non-laser/bubble DPIV when lasers aren’t feasible for live animals. AIP Publishing

·      Fish (1993, JEB) — Hydromechanical modeling of bottlenose dolphin propulsion to estimate power output and propulsive efficiency across speeds; foundational frame for relating fluke kinematics, body drag and delivered thrust/power. Frequently cited baseline for cetacean swimming energetics. The Journal of Experimental Biology+1

·      Fish (2006, Bioinspiration & Biomimetics) — Review addressing “Gray’s paradox.” Concludes dolphins’ performance can be explained by high muscle power, streamlined bodies, and effective kinematics; no evidence for sustained, fully laminar boundary layers on live dolphins. Useful context on what doesn’t explain their speed. PubMed

·      Fish & Rohr (1999, SPAWAR Tech. Rep. 1801) — Broad, technical survey of dolphin hydrodynamics: morphology, kinematics, performance, and wake physics, consolidating prior data that later studies (including DPIV work) build upon. Semantic Scholar

·      Ayancik, Fish & Moored (2020, J. R. Soc. Interface) — 3-D scaling laws linking fluke shape (e.g., aspect ratio/planform) and kinematics (heave–pitch mix) to thrust, power, and efficiency. Shows there’s an optimal heave-to-pitch ratio that maximizes efficiency and that optimal settings depend on aspect ratio and amplitude—i.e., geometry and motion must be co-tuned for best performance. PubMed

Note: None of these papers claims a specific “dolphin-tail shaped blade tip” is categorically the best possible engineered ending; they show why dolphin fluke physics (coherent vortex rings and momentum jet) yields high thrust and good efficiency, which inspires fluke-like tip design in our fins.

References:

• Fish, F.E., Legac, P., Williams, T.M. & Wei, T. (2014) ‘Measurement of hydrodynamic force generation by swimming dolphins using bubble DPIV’, Journal of Experimental Biology, 217(2), pp. 252–260. https://doi.org/10.1242/jeb.087924.

• Fish, F.E., Williams, T.M., Moon, Y.E., Sherman, E., Wu, V. & Wei, T. (2018) ‘Experimental measurement of dolphin thrust generated during a tail stand using DPIV’, Fluids, 3(2), 33. https://doi.org/10.3390/fluids3020033.

• Legac, P., Wei, T., Fish, F.E., Williams, T., Mark, R. & Hutchison, S. (2008) ‘Digital particle image velocimetry of mammalian swimming’, Physics of Fluids, 20(9), 091105. https://doi.org/10.1063/1.2973663.

• Moon, Y.E., Sherman, E., Fish, F.E., Williams, T.M. & Wei, T. (2008) ‘DPIV measurements of dolphins performing tailstands’, 61st Annual Meeting of the APS Division of Fluid Dynamics (DFD08), San Antonio, TX, 23–25 Nov 2008. (Abstract ID: BAPS.2008.DFD.GJ.2).

• Fish, F.E. (1993) ‘Power output and propulsive efficiency of swimming bottlenose dolphins (Tursiops truncatus)’, Journal of Experimental Biology, 185, pp. 179–193.

• Fish, F.E. (2006) ‘The myth and reality of Gray’s paradox: implications of dolphin drag reduction for technology’, Bioinspiration & Biomimetics, 1(2), R17–R25. https://doi.org/10.1088/1748-3182/1/2/R01.

• Fish, F.E. & Rohr, J.J. (1999) Review of Dolphin Hydrodynamics and Swimming Performance. SPAWAR Systems Center Technical Report 1801, San Diego, CA. https://doi.org/10.21236/ADA369158.

• Ayancik, F., Fish, F.E. & Moored, K.W. (2020) ‘Three-dimensional scaling laws of cetacean propulsion characterize the hydrodynamic interplay of flukes’ shape and kinematics’, Journal of the Royal Society Interface, 17(163), 20190655. https://doi.org/10.1098/rsif.2019.0655