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Water Entry Impact Dynamics of Diving BirdsSharker, Saberul Islam 01 May 2017 (has links)
Some seabirds (such as Northern Gannets and Brown Boobies) can dive from heights as high as 30 m reaching speeds of up to 24 m/s as they impact the water surface. It is perceived that physical geometry, particularly of the beak, allows them to endure relatively high impact forces that could otherwise kill non-diving birds. Acceleration data from simplified models of diving birds agree with simulated data for one species (Northern Gannet), however, no reliable experimental data with real bird geometries exist for comparison purposes. This study utilizes eleven 3D printed diving birds (five plunge-diving, five surface-diving and one dipper) with embedded accelerometers to measure water-entry impact accelerations for impact velocities ranging between 4.4 - 23.2 m/s. Impact forces for all bird types are found to be comparable under similar impact conditions and well within the safe zone characterized by neck strength as found in recent studies. However, the time each bird requires to reach maximum impact acceleration and its effect represented here by the derivative of acceleration (i.e., jerk), is different based on its beak and head shape. We show that surface diving birds cannot dive at high speeds as the non-dimensional jerk experienced exceeds a safe limit estimated from human impact analysis, whereas those by plunge divers do not.
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