Propulsion Strategy Analysis of High-Speed Swordfish

Abstract

Fish have appeared since Precambrian more than 500 million years ago. Yet, there are still much untamed areas for fish propulsion research. The swordfish has evolved a light thin/high crescent tail fin for pushing a large amount of water backward with a small velocity difference. Together with a streamlined forward-enlarged thin/high body and forwardbiased dorsal fin enclosing sizable muscles as the power source, the swordfish can thus achieve unimaginably high propulsion efficiency and an awesome maximum speed of 130 km/h as the speed champion at sea. This paper presents the innovative concepts of ''kidnapped airfoils'' and ''circulating horsepower'' using a vivid neat-digit model to illustrate the swordfish's superior swimming strategy. The body and tail work like two nimble deformable airfoils tightly linked to use their lift forces in a mutually beneficial manner. Moreover, they use sensitive rostrum/lateral-line sensors to detect upcoming/ambient water pressure and attain the best attack angle to capture the body lift power aided by the forwardbiased dorsal fin to compensate for most of the water resistance power. This strategy can thus enhance the propulsion efficiency greatly to easily exceed an astonishing 500%. Meanwhile, this amazing synergy of force/beauty also solves the perplexity of dolphin's Gray paradox lasting for more than 70 years and gives revelations for panoramic fascinating future studies.

How Non-Uniform Stiffness Affects the Propulsion Performance of a Biomimetic Robotic Fish

“…It is known that the eel has a soft body, as shown in Figure 1 a, which makes it feature a certain degree of motor flexibility, but relatively poor maneuverability. Compared with the eel, the body of the swordfish tends to be rigid, as shown in Figure 1 b, with a swimming speed of 130 km/h [ 29 ], but its locomotor flexibility is much less than that of the eel [ 30 , 31 , 32 ]. In addition, according to the distribution characteristics of the stiffness of the real fish, and inspired by the above biological constitution of eels and swordfishes, we designed a mechanism model with a rigid anterior border and flexible rear border, namely a non-uniform stiffness model.…”

Recent records of swordfish attacks on harpoon vessels in the Sicilian waters (Mediterranean Sea)

“…The swordfish, Xiphias gladius (Linnaeus, 1758) is the only species belonging to the Xiphiidae family that inhabits tropical and temperate seas of the world. It is an apex opportunistic predator and a fast swimmer (CANESE et al, 2008;LEE et al, 2009). It can perform rapid depth excursions from 400-500 m to the surface in few minutes (CAREY, 1981;CANESE et al, 2004CANESE et al, , 2008.…”