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SUMMARY:Drinking and Diving - Sunghwan (Sunny) Jung (Virginia Polytechnic 
 Institute and State University)
DTSTART:20170921T123000Z
DTEND:20170921T131000Z
UID:TALK80451@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:I will discuss two fluid-mechanics problems exploited by biolo
 gical systems.  <br><br>First\, animals that drink must transport water in
 to the mouth using either a pressure-driven (suction) or inertia-driven (l
 apping) mechanism. Previous work on cats shows that these mammals lap usin
 g a fast motion of the tongue with relatively small acceleration (~1g)\, i
 n which gravity is balanced with steady inertia in the liquid. Do dogs emp
 loy the same physical mechanism to lap? To answer this question\, we recor
 ded 19 dogs while lapping and conducted physical modeling of the tongue&#3
 9\;s ejection mechanism. In contrast to cats\, dogs accelerate the tongue 
 upward quickly (~1-4g) to pinch off the liquid column. The amount of liqui
 d extracted from the column depends on whether the dog closes the jaw befo
 re or after the pinch-off. Our recordings show that dogs close the jaw at 
 the moment of pinch-off time\, enabling them to maximize volume per lap.  
 <br><span><br>Second\, several seabirds (e.g. Gannets and Boobies) dive in
 to water at up to 24 m/s as a hunting mechanism. We studied how diving bir
 ds survive water impacts because of their beak shape\, neck muscles even w
 ith a long slender neck. The birds&rsquo\; slender necks appear fragile bu
 t do not crumble under the compression due to high-speed impact. First of 
 all\, we use a salvaged bird to resolve plunge-diving phases and the skull
  and neck anatomical features to generate a 3D-printed skull and to quanti
 fy the effect of the neck&rsquo\;s musculature to provide the necessary st
 ability. Then\, physical experiments of an elastic beam as a model for the
  neck attached to a skull-like cone revealed the limits for the stability 
 of the neck during the bird&rsquo\;s dive as a function of impact velocity
  and geometric factors. We find that the small angle of the bird&#39\;s be
 ak and the muscles in the neck predominantly reduce the likelihood of inju
 ry during a high-speed plunge-dive. Finally\, we di scuss maximum diving s
 peeds for humans using our results to elucidate injury avoidance.&nbsp\;</
 span>
LOCATION:Seminar Room 1\, Newton Institute
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