Measurement of seawater surface tension coefficient based on bubble rising behavior

The surface tension of seawater becomes increasingly important on the construction of ocean environment and the analysis of ocean characteristics. A non-invasive measurement method of seawater surface tension coefficient across a salinity range of 10 g/kg <= S <= 30 g/kg and a temperature range of 25.83 degrees C <= t <= 37.79 degrees C was carried out through the visual measurement system in this paper. The implicit representation of the surface tension coefficient and bubble terminal rising velocity was established on the basis of the bubble force balance theory. The motion characteristics of the bubble were calculated by high-speed photography. Additionally, the intrinsic and extrinsic parameters of the camera, as well as the coefficients of lens distortion were estimated. A new correlation of the surface tension coefficient was developed as a function of the salinity and temperature. The quantitative correlations analysis shows that the experimental results are in good agreement with the predicted values by the typical correlations, and the maximum deviation is less than 0.28%, which indicates that the method is valid and has high precision. (C) 2019 Elsevier Ltd. All rights reserved.