Hydrodynamic significance of sea lion skin texture

An investigation of the influence of sea lion skin texture on skin friction was conducted by Laser Doppler Velocimetry measurements over small patches of extracted sea lion foreflipper skin. Sea lions are agile swimmers who propel and maneuver themselves using mainly their large foreflippers. The agility and amphibious capabilities of sea lions have inspired attempts to understand and model their methods of swimming. These studies have simplified flipper models by overlooking the skin and fur texture. Related studies on shark and dolphin skin have shown that small-scale skin texture can affect large-scale hydrodynamics. In the current work, 7 cm by 7 cm samples of sea lion foreflipper skin were extracted and mounted as a level insert in a flat plate for boundary layer testing at the United States Naval Academy. The measured boundary layer and its characteristics were compared between various skin samples, between forward and reverse flow over the samples, and between sea lion skin and sandpaper control samples. Preliminary results suggest minor hydrodynamic improvements are possible due to the sea lion’s skin and fur.