A Universal Scaling Law for Gas Transfer Velocities across Complex Interfaces
Gabriel Katul
Civil and Environmental Engineering, Duke University
ABSTRACT: Large-scale climate models commonly leave out an important ingredient. Katul describes the importance of turbulent eddies and how transfer velocities scale when considering the transfer of water vapor from rough surfaces into a turbulent atmosphere and other conditions. A large corpus of field and laboratory experiments support the finding that transfer velocities at interfaces subject to turbulent eddies scale as where 𝜈 is the kinematic viscosity and 𝜖 is the mean turbulent kinetic energy dissipation rate of eddies. This scaling appears to hold for marine and coastal systems, and across many other conditions. Katul explores the working hypothesis that this universal scaling is a direct outcome of the Kolmogorov inertial subrange energy content in eddies modified to include viscous-cutoff thereby by-passing the need for a surface renewal assumption. The connection between energy content in eddies (i.e., a microscopic state) and gas transfer velocities (i.e., macroscopic outcome) might be viewed as analogous to a fluctuation-dissipation relation but for turbulent flows.
