Meeting Abstract
The streamlined body shapes of cetaceans delay the separation of flow, create lower drag when they swim, and therefore decrease their locomotor cost in terms of energetics. However, previous studies show that body shape of the North Atlantic right whale (Eubalaena glacialis; hereafter right whale) changes with life stages, reproduction status, nutritive conditions, and the effects of entanglement. Accordingly, we aimed to investigate the changes in drag on right whales with variances in body shapes and estimate any associated kinematic costs. We hypothesized that emaciated right whales, which have a less-streamlined body configuration, suffer higher drag when swimming and consequently need longer time to replenish their energy reserves. This fact is likewise crucial for pregnant females because their energy budget for migrating to breeding grounds may increase due to having an enlarged girth for their abdomen. To obtain measurements of drag over right whales under various body conditions, we undertook computational fluid dynamics (CFD) simulations on several static right whale models reflecting different body fitness (e.g., normal condition, emaciation, and pregnancy, etc.) and measured multiple fluid dynamics parameters such as characteristics of boundary layer and hydrodynamic forces on the animals. Our results reveal that drag on right whales fluctuates across its body and varies between models of different body fitness, suggesting that the kinematic energy expenditure of right whales is indeed affected by its body shape.
