Abstract
The effects of rainfall on mass transfer across the air-water interface were investigated through laboratory experiments in a turbulent open-channel flow. The CO_2 absorption rate due to raindrops impinging on the free surface was measured by a soap-film flow meter. The mass transfer coefficient on the liquid side, k_L, is well correlated with the mean vertical momentum flux of rainfall, MF, but it is not well correlated with the mean kinetic energy flux of rainfall, KEF, which has been proposed as the best parameter for correlating k_L in the previous studies. The CO_2 absorption mechanism is clarified by the visualization of velocity and CO_2 concentration fields by means of PIV and LIF.
