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


Iosilevskii, Gil (2020), Center-of-mass and minimal speed limits of the great hammerhead, Dryad, Dataset,


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.


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