Simulation of humpback whale bubble-net feeding models

• Published in: The Journal of the Acoustical Society of America
• Main Authors: Bryngelson, Spencer H., Colonius, Tim
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Acoustical Society of America 2020
• Subjects: Humpback Whale
• Online Access: https://doi.org/10.1121/10.0000746

Humpback whales can generate intricate bubbly regions, called bubble nets, via blowholes. Humpback whales appear to exploit these bubble nets for feeding via loud vocalizations. A fully-coupled phase-averaging approach is used to model the flow, bubble dynamics, and corresponding acoustics. A previously hypothesized waveguiding mechanism is assessed for varying acoustic frequencies and net void fractions. Reflections within the bubbly region result in observable waveguiding for only a small range of flow parameters. A configuration of multiple whales surrounding and vocalizing towards an annular bubble net is also analyzed. For a range of flow parameters, the bubble net keeps its core region substantially quieter than the exterior. This approach appears more viable, though it relies upon the cooperation of multiple whales. A spiral bubble net configuration that circumvents this requirement is also investigated. The acoustic wave behaviors in the spiral interior vary qualitatively with the vocalization frequency and net void fraction. The competing effects of vocalization guiding and acoustic attenuation are quantified. Low void fraction cases allow low-frequency waves to partially escape the spiral region, with the remaining vocalizations still exciting the net interior. Higher void fraction nets appear preferable, guiding even low-frequency vocalizations while still maintaining a quiet net interior. © 2020 Acoustical Society of America. Received 27 September 2019; revised 16 December 2019; accepted 30 January 2020; published online 14 February 2020. We thank Dr. Kevin Schmidmayer for numerous fruitful discussions. This work was supported by the Office of Naval Research under grant number N0014-17-1-2676. Associated computations utilized the Extreme Science and Engineering Discovery Environment, which were supported by the U.S. National Science Foundation under grant number TG-CTS120005. Published - 10.0000746.pdf Submitted - 1909.11768.pdf