Measurements of spray at an air-water interface

Abstract

The spray content in the surface boundary layer above an air—water interface was determined by a series of measurements at various feteches and wind speeds in a laboratory facility. The droplet flux density N( z) can be described in terms of the scaling flux density N ∗ and von Karman constant K throguh the equation, N(z)/N ∗ = −(1/K) ln(z/z 0d ) where z is height above the mean water level and z 0d is the droplet boundary layer thickness. N ∗ is given by a unique relationship in terms of the roughness Reynolds number u ∗σ/ν where σ is the root-mean-square surface displacement. Spray inception occurred for u ∗ ⪸ 0.3 . The dominant mode of spray generation in the present and most other laboratory tests, as well as in available field data, appears to be bubble bursting.