Minimum drag on a three-dimensional North Atlantic right whale model via neutral trim pose


SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
2021 VIRTUAL ANNUAL MEETING (VAM)
January 3 – Febuary 28, 2021

Meeting Abstract


70-7  Sat Jan 2  Minimum drag on a three-dimensional North Atlantic right whale model via neutral trim pose Wu, C*; Howle, LE; Nowacek, DP; Marine Science and Conservation, Duke University; Mechanical Engineering and Materials Science, Duke University; Marine Science and Conservation and Electrical and Computer Engineering, Duke University chen.yi.wu@duke.edu

Animals experience hydrodynamic forces (lift, drag, side) and moments (yaw, pitch, roll) as a result of motion in an aqueous medium. Extra momentum imparted into the fluid from lift and side forces as well as yaw, pitch, and roll moments (here, the parasitic loads) results in extra drag on the animal. Animals minimize energy expenditure by streamlining, delaying flow separation, and minimizing excess fluid momentum from parasitic loads. Numerous studies have attempted to evaluate the energetics and swimming performance of aquatic animals. Here, we considered drag to be not only a function of body shape and flow regime but also a function of parasitic loads. We used computation fluid dynamics on a 3-D North Atlantic right whale model to minimize drag by eliminating parasitic loads; thereby eliminating momentum from the wake not caused by drag alone. We found that minimum drag, which corresponds to the elimination of the parasitic loads, can be obtained by adjusting the pose of the animal. Thus, minimum drag occurs at the neutral trim pose. For our specific model, simulations revealed that by changing the angle of attack of the flippers by 4.0315° (relative to the free-stream flow) and pitching the spine downward by 5° while maintaining fluke angle, the drag was lowered by approximately 11% across the speeds tested. This drag reduction was relative to our previous drag study on the same animal model but without body pose adjustments. This finding underscores the need to find the model’s neutral trim pose for drag simulations.

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