Ultrasonic in-situ measurement of the marine microlayer

In-situ measurement techniques for the characterization of the marine microlayer have been developed. The approach is based on integrating ultrasonic measurements with a well-accepted microlayer sampler. The sampler is a rotating glass drum that collects the thin water film covering its surface. The film thickness varies in the range of 50-200 mu m for a drum rotation speed of 20 RPM. By attaching ultrasonic transducers on the inner surface of the drum, the thickness and viscosity of the film are measured. The viscosity of the liquid film over the drum is deduced from a measurement of the damping coefficient of the multiple echoes in the wall of the drum. The thickness of the film is related to the surface tension and viscosity of the liquid and to the rotation speed of the drum. Thus, the surface tension of the film is calculated. >