CAM Colloquium - October 30, 2026, Olivia Pomerenk - "Flocking and floating: collective behavior in fluid systems"

Title: Flocking and floating: collective behavior in fluid systems

Abstract: Collective behavior emerges across biological scales, from the self-assembly of particles and cells to the coordinated motion of insects, fish, and birds. This talk explores mathematical approaches to two very different examples of such collective behavior in fluid environments. In the first half, we develop a generalized boundary-element framework for capillary interactions among arbitrary three-dimensional particle assemblies at a fluid interface. This provides a general framework for characterizing how particle geometry and assembly configurations produce attraction, repulsion, and collective organization, with applications ranging from cellular and sub-cellular self-assembly to small insects at the air-water interface. In the second half of the talk, we shift from passive particles to active agents, and from the capillary to the inertial scale. We develop a reduced-order model of the wake-vortex interactions between two flapping birds flying in tandem. Applying the model to northern bald ibises, we identify an optimal configuration that minimizes the follower bird's aerodynamic power expenditure, and use these results to investigate the aerodynamic mechanisms underlying V-formations. While the two systems explored in this talk differ substantially in scale and physical mechanism, both illustrate how reduced-order models of interactions among agents can reveal the principles underlying collective organization.

Short bio: Olivia Pomerenk is a Hope Street Postdoctoral Research Fellow in the Center for Fluid Mechanics at Brown University. Her research seeks to characterize the principles governing propulsion and coordinated motion, from how individual organisms and engineered systems generate and control locomotion in fluid environments to how physical interactions give rise to emergent collective dynamics. She obtained a Ph.D. in Mathematics from the Courant Institute of Mathematical Sciences at NYU in 2025, and a B.S. in Applied and Computational Mathematics from Caltech in 2020.