Meeting Abstract

41.4  Saturday, Jan. 5  Rorqual whale hydrodynamics and body drag during non-feeding transport, as revealed by Computational Fluid Dynamics (CFD) POTVIN, J*; REYES, P; MCQUILLING, M; GOLDBOGEN, J A; SHADWICK, R E; Saint Louis University; Saint Louis University; Saint Louis University; Cascadia Research Collective; Univ. of British Columbia potvinj@slu.edu

Rorqual whales (Balaenopteridae) represent a group of marine mammals that include the largest vertebrates to have ever lived and thus to have necessitated the highest absolute energy requirements. Recent hydrodynamic modeling (Goldbogen et al 2012 Func. Ecol.; Potvin et al. 2012 PLoS One; Weidenmann et al 2011 Ecol. Model.) has shown how these are met, thanks to high body streamlining and efficient hunting (lunge feeding). The obvious impossibility of studying the energetics of large whales in laboratory settings makes computer modeling the only tool available for assessing the factors driving the costs of both feeding and non-feeding transport. A crucial input for non-feeding travel, diving and prey-approach simulation is the drag coefficient of the body, which for rorquals can be meaningfully defined (i.e. as decoupled from thrust), with their propulsion originating from the oscillatory motion of short chord-length appendages located aft of the body (the flukes). So far rorqual drag has been estimated from a flat plate-based approach dating from the 1930’s (Gray 1936 J. Exp. Biol.). This is revisited here in terms of the more modern approach of CFD, with a presentation of preliminary drag calculations obtained from simulations performed about realistic body shapes representative of the genus balaenoptera, and over the body length and morphology spectrum characteristic of fin whales (B. physalus). Other issues to be discussed include (digital) model construction and manipulation, boundary layer modeling and sensitivity on body shape details (including tail flexion).