Meeting Abstract
P1.118 Tuesday, Jan. 4 Three-dimensional geometry of the narwhal (Monodon monoceros) flukes in relation to hydrodynamics FONTANELLA, J.E.*; FISH, F.E.; RYBCZYNSKI, N.; NWEEIA, M.; KETTEN, D.R.; West Chester Univ., Pennsylvania; West Chester Univ., Pennsylvania; Canadian Museum of Nature, Ottawa, Canada; Harvard Univ., Boston, Massachusetts; Woods Hole Oceanographic Institution, Massachusetts jf650930@wcupa.edu
Caudal flukes are the sole propulsive structure of cetaceans. Sexual variation in fluke shape is observed for the narwhal, Monodon monoceros, where the female has a shape similar to other cetaceans with sweepback, but the male has flukes without sweepback. Fluke geometry was collected for male and female narwhals, comparing the differences in planform morphology. Aspect ratio was not different between the sexes. Sweepback angle for female and male flukes were 31.4o and 20.5o, respectively. Fluke cross-sections from CT scans showed highly streamlined flukes, having a rounded leading edge and a tapering, trailing edge. Shoulder position (SP) for male and female narwhals was 0.28 and 0.30, respectively. Over the range of 20-65% of fluke span, females averaged a 10% greater SP than males. Thickness ratio (TR) of males and females were 0.23 and 0.24, respectively. Within the range of 20-90% of span, TR for females was 5% greater than for the males. Values of TR and SP indicate that male narwhals have a hydrodynamic advantage in reducing drag; whereas, the cross-sectional design of the flukes of female narwhals would tend to increase lift and delay stall. The sweep angles indicate females would have increased lift at low swimming speeds, whereas males would have high efficiency at high swimming speeds.
