Quantitative measurement and application of droplets on physical surfaces based on LIF technology

Contaminated surfaces play a significant role in the transmission of respiratory infectious diseases. To address this issue, we presented a novel quantitative detection method for droplets on physical surfaces, based on Laser-Induced Fluorescence (LIF) technique. The proposed detection method was demonstrated in a realistic high-speed train compartment scenario by simulating the process of droplet release during passengers' breathing and coughing. The experimental results showed that this method could offer high precision (10−1 mg/m2) for detecting minute substance concentrations, and its ease of operation makes it suitable for complex engineering environments. The results also revealed that under the combined effects of the indoor airflow and breathing airflow, the range of droplets released by breathing activity exceeded two rows in front and behind the release position. Simultaneously, we observed that a large number of droplets settled on the seat surfaces on both sides of the same row as the releaser, with over 36% of these droplets concentrated on the backrest area of the seats. As the respiratory jet velocity increased, the location with the most sediment droplets (accounting for 8% of the total sedimentation) occurred on the seat directly in front of the releaser, and approximately 48% of the droplets were found on the back of this seat. Our proposed method overcomes the shortcomings of existing experimental methods in quantitatively capturing the motion characteristics of droplets in complex flow fields.