Department of Physics, NCU
How does fluid dynamics change with animal size
Patricia Yang 楊佩良
Dept. of Mechanical Engineering, Georgia Institute of Technology
Date 2014.7.8 (Tue)
Animals manipulate fluids based on their body size. While larger animals might gain benefit from fluids, smaller animals are challenged by surface tension. We present scaling analysis and high-speed videography to elucidate the mechanics on two biological systems. In the first part, we investigate how flying fish penetrate air-water surface. Flying fish can both swim underwater and glide in air. The transition from swimming to gliding requires breaking “surface tension barrier,” a formidable task for juvenile flying fish. As they leap from water, flying fish achieve gliding speed which is ten times faster than their swimming speed. In the second part, we investigate the hydrodynamics of urination across five orders of magnitude in body mass. For larger mammals above 3 kg in weight, they empty their bladders over constant duration. Smaller mammals are challenged during urination by high viscous and capillary forces that limit their urine to single drops.