Influence of a perpendicular liquid flow on a cleaning process using 20 kHz ultrasound: Characterization of the agitation at vicinity of the surface opposite to the transducer

Abstract

AbstractThis work is part of a project consisting of the development of an automatic cleaning station for the immersed part of boats. This self‐service station combines ultrasound for washing with a specific water treatment. Since, in this case, displacement of the transducers plus suction of the dirt removed induce circulation, we need to measure the ultrasound activity which reaches the surface despite the disruptions. The goal of this work is to quantify this ultrasound activity. For this purpose, a specific lab‐scale equipment was designed and built. Two methods were implemented for quantification of the ultrasound activity: Particle Image Velocimetry and electrochemical mass transfer measurements. From electrochemical measurements, a parietal velocity was calculated and found to be consistent with velocities obtained from both flow rate and PIV measurements in silent conditions. Moreover, it was found that, even in the presence of a liquid flow perpendicular to the main direction of propagation of ultrasound, contribution of ultrasound to the agitation on the opposite wall remained noticeable. Nevertheless, results showed that the main activity was concentrated in the area close to the transducer. Thus, to maximize the cleaning process, small distances must be maintained between the cleaning tool and the boat hull.