Animal design advantage from the analogy between friction and body heat loss

When a fluid accelerates as it sweeps a solid surface there are two consequences: the friction and the heat transfer (thermal contact) between fluid and solid increase simultaneously. This is known as the universal analogy between fluid friction and heat transfer. In thermal engineering these two ef...

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Bibliographic Details
Published in:BioSystems 2024-01, Vol.235, p.105096-105096, Article 105096
Main Authors: Bejan, Adrian, Charles, Jordan D.
Format: Article
Language:English
Subjects:
Animal design
Animals
Body Temperature Regulation
Constructal
Design
Drag
Fishes
Friction
Heat loss
Hot Temperature
Mammals
Swimming
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Summary:When a fluid accelerates as it sweeps a solid surface there are two consequences: the friction and the heat transfer (thermal contact) between fluid and solid increase simultaneously. This is known as the universal analogy between fluid friction and heat transfer. In thermal engineering these two effects are problematic because improved thermal contact is beneficial, and increased friction (i.e., pumping power) is detrimental to overall performance. In the present article we question whether the ‘analogy’ between these conflicting effects hampers the performance of animal movement. The theory focuses on warm-blooded swimmers and the effects (friction, heat transfer) that result from one change in the configuration of the body. Selected for analysis is a breaststroke swimmer. During gliding while reaching forward the ‘one change’ is from (a) legs spread apart, to (b) legs held tight together. The theory shows that the change from (a) to (b) has two consequences: greater swimming speed, and reduced body heat loss. In animal design both effects are beneficial, unlike in engineered flow systems. The analogy between fluid friction and heat transfer accelerated the evolution of animal design, and accounts for the 'divergent evolution' of fish and mammals.
ISSN:0303-2647
1872-8324
DOI:10.1016/j.biosystems.2023.105096