Dresden 2026 – scientific programme

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BP: Fachverband Biologische Physik

BP 2: Computational Biophysics I

BP 2.12: Talk

Monday, March 9, 2026, 12:30–12:45, BAR/0106

Human breathing pattern dominates the effective diffusivity of droplets emitted while speaking — •Lars Natusch and Roland Netz — Fachbereich Physik, Forschungsgruppe Roland Netz, Freie Universität Berlin, Berlin, Germany

For understanding airborne viral infection pathways, the prediction of the effective diffusivity of saliva droplets emitted from a person while speaking and breathing is crucial.

In enclosed non-ventilated indoor spaces the diffusivity of tracer particles or molecules emitted by a person is governed by the complex interplay of various physical transport mechanisms. By comparison of lattice-based simulations of the three-dimensional compressible Navier-Stokes equation with experiments measuring the spreading of carbon-dioxide emitted from a person, we demonstrate that molecular diffusion and convection due to body heat and temperature gradients at walls and windows are present, but that the main spreading mechanism is related to the periodic breathing pattern of a person, which induces long-range advection.

Our results identify breathing as the dominant mechanism for particle transport in stagnant indoor air.

Keywords: Airborne transmission; Droplet diffusivity; Breathing-induced advection; Indoor air transport; Lattice-based Navier–Stokes simulations