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Center-of-mass and minimal speed limits of the great hammerhead

Citation

Iosilevskii, Gil (2020), Center-of-mass and minimal speed limits of the great hammerhead, Dryad, Dataset, https://doi.org/10.5061/dryad.xwdbrv1b8

Abstract

The great hammerhead is denser than water, and hence relies on hydrodynamic lift to compensate for its lack of buoyancy, and on hydrodynamic moment to compensate for a possible misalignment between centers of mass and buoyancy. Because hydrodynamic forces scale with the swimming speed squared, whereas buoyancy and gravity are independent of it, there is a critical speed below which the shark cannot generate enough lift to counteract gravity, and there are anterior and posterior center-of-mass limits beyond which the shark cannot generate enough pitching moment to counteract the buoyancy-gravity couple. The speed and center-of-mass limits were found from numerous wind-tunnel experiments on a scaled model of the shark. In particular, it was shown that the margin between the anterior and posterior center-of-mass limits is a few tenths of the product between the length of the shark and the ratio between its weight in and out of water; a diminutive 1% body length. The paper presents the wind tunnel experiments, and discusses the roles that the cephalofoil and the pectoral- and caudal- fins play in longitudinal balance of a shark.

Methods

The model of the great hammerahead was designed using SolidWorks®2014. Each '*stl' file is associated with a single part of the model.

Forces on the model were measured in a 1m by 1m by 3m subsonic wind tunnel at 50 m/s. Each file contains forces amd moments measured on a particular configuration at angles of attack ranging between -15 to +17 degrees.  

 

Usage Notes

All data files - these are files that end with '*cfc' - are ASCII. 

'List of experiments' associates a data file with the particular configuration.

'List of parameters' explains each column in a data file.

All model files end with '*stl'.

' LongitudinalBalanceOfTheGreatHammerhead252Drawings.pdf' gives an overview of the model