Simulation of humpback whale bubble-net feeding models.

Area of Science:

• Marine biology
• Acoustics
• Fluid dynamics

Background:

• Humpback whales (Megaptera novaeangliae) utilize complex bubble nets for feeding.
• Vocalizations are hypothesized to play a role in the bubble net feeding strategy.

Purpose of the Study:

• To model the acoustic properties of humpback whale bubble nets.
• To investigate the waveguiding and sound attenuation mechanisms within bubble nets.
• To assess the effectiveness of different bubble net configurations (annular and spiral) for acoustic manipulation.

Main Methods:

• A fully-coupled phase-averaging approach was employed to model fluid flow, bubble dynamics, and acoustics.
• Acoustic wave propagation was analyzed for varying frequencies and bubble net void fractions.
• Simulations were performed for single-whale (spiral) and multi-whale (annular) configurations.

Main Results:

• Waveguiding effects were observed within a limited range of flow parameters.
• Annular bubble nets created quieter interiors, but required multiple whales.
• Spiral bubble nets demonstrated effective sound guiding and attenuation, with higher void fractions being more efficient.
• Low void fractions allowed low-frequency sound escape, while higher void fractions guided sound and maintained interior quietness.

Conclusions:

• Bubble nets significantly influence acoustic wave propagation, offering potential for acoustic manipulation in feeding strategies.
• Spiral bubble nets are a viable configuration for acoustic manipulation, requiring only a single whale.
• Higher bubble net void fractions enhance the guiding of whale vocalizations and the maintenance of a quiet net interior.