Preprints
https://doi.org/10.5194/os-2021-39
https://doi.org/10.5194/os-2021-39

  17 May 2021

17 May 2021

Review status: this preprint is currently under review for the journal OS.

Drifting Dynamics of the Bluebottle

Daniel Lee1,2, Amandine Schaeffer1,2, and Sjoerd Groeskamp3 Daniel Lee et al.
  • 1Coastal and Regional Oceanography Lab, School of Mathematics and Statistics, UNSW Australia, Sydney, New South Wales, Australia
  • 2Centre for Marine Science and Innovation, UNSW Australia, Sydney, New South Wales, Australia
  • 3NIOZ Royal Netherlands Institute for Sea Research, Texel, Netherlands

Abstract. Physalia physalis, also called the Bluebottle in Australia, is a colonial animal resembling a jellyfish that is well known to beachgoers for the painful stings delivered by their tentacles. Despite being a common occurrence, the origin of the Bluebottle before reaching the coastline is not well understood, and neither is the way it drifts at the surface of the ocean. Previous studies used numerical models in combination with simple assumptions to calculate the drift of this species, excluding complex drifting dynamics. In this study, we provide a new parametrization for Lagrangian modelling of the Bluebottle by considering the similarities between the Bluebottle and a sailboat. This allows us to compute the hydrodynamic and aerodynamic forces acting on the Bluebottle and use an equilibrium condition to create a generalised model for calculating the drifting speed and course of the Bluebottle under any wind and ocean current conditions. The generalised model shows that the velocity of the Bluebottle is a linear combination of the ocean current velocity and the wind velocity scaled by a coefficient ('shape parameter') and multiplied by a rotation matrix. Adding assumptions to this generalised model allows us to retrieve models used in previous literature. We discuss the sensitivity of the model to different parameters (shape, angle of attack and sail camber) and explore different cases of wind and current conditions to provide new insights into the drifting dynamics of the Bluebottle.

Daniel Lee et al.

Status: open (until 12 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2021-39', Laura Prieto, 22 Jun 2021 reply
  • RC2: 'Comment on os-2021-39', Luis Ferrer, 23 Jun 2021 reply

Daniel Lee et al.

Daniel Lee et al.

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Short summary
The Bluebottle (Physalis Physalis), called the Portuguese Man of War in the Atlantic, is well known for the painful stings caused by their tentacles. The drifting dynamics of this species has not been widely explored, with previous studies using simple assumptions to calculate the Bluebottle's drift. This study presents a new theoretical model for the drifting speed and course of the Bluebottle in different wind and ocean conditions.