Three-Dimensional Geometry of the Narwhal (Monodon monoceros) Flukes in Relation to Hydrodynamics
Flukes are distally located extensions of the tail, and from a biomechanical standpoint, function as a pair of wings (Vogel 1994). Flukes function to produce thrust generated as an anteriorly directed lift force as flukes oscillate vertically (Fish 1998a, b). Their cross-sections resemble hydrofoils...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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2011
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| Online Access: | http://www.dtic.mil/docs/citations/ADA569714 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA569714 |
| Summary: | Flukes are distally located extensions of the tail, and from a biomechanical standpoint, function as a pair of wings (Vogel 1994). Flukes function to produce thrust generated as an anteriorly directed lift force as flukes oscillate vertically (Fish 1998a, b). Their cross-sections resemble hydrofoils. For a hydrofoil to be effective, a large lift must be produced while drag is minimized; this, in turn, increases the thrust generated (Weihs 1989, Vogel 1994). The hydrodynamic implications of fluke design can be studied by examining the cross-sections (i.e., parasagittal) of the flukes. Cross-section profiles taken along the horizontal axis exhibit what is a typical streamlined hydrofoil profile with a rounded leading edge and a long, tapered trailing edge. This shape is critical for the generation of lift for thrust, while minimizing induced drag (i.e., drag due to lift production; Lighthill 1970, Vogel 1994). The flukes are symmetrical about the chord (Lang 1966, Bose et al. 1990). The cross-sectional profile of the flukes is similar to symmetrical engineered foils (Fish 1998b). The similarity to engineered foils would imply that cetacean flukes would be capable of effectively generating large lift with low drag at higher angles of attack. Published in Marine Mammal Science, v27 n4 p889-898, Oct 2011. |
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