Decay of stationary capillary waves on impinging liquid jets

This study is concerned with the capillary-wave field generated at the base of a liquid jet impinging on a liquid reservoir. Capillary waves on laminar liquid jets are investigated in terms of the spatial damping coefficient. We find an exponential decrease of the wave crests, with the decay rate given by theory. We show that a small increase in viscosity leads to rapid suppression of the wave-like behavior. This study also emphasizes the effect of viscoelasticity, which decreases the damping coefficient. A simple dependence on the combined Weber-Deborah number is proposed for the dimensionless damping coefficient. At the impact zone, similarities are found for the decay of the free surface compared to the classic model of a meniscus climbing on a cylindrical fiber, the radial jet profile taking the shape of a catenary curve. Theoretical predictions are found to be in good qualitative agreement with the experimental data.