The present study is part of a global project which consists in the development of an automatic cleaning station for immersed boats (cockle, ninepin, etc.) in a self-service mode, associating an innovative ultrasonic device for cleaning with a specific water treatment. The originality of the process is that cleaning is performed by three transducers operating simultaneously at low frequency and moving along the surface, thanks to programmable logic controllers, and that it includes a suction to collect the dirt removed. Therefore, the time required for boat maintenance is shortened, ensuring high quality cleaning without the need for dry docks and avoiding additional pollution in the harbor areas. One of the key points was the evaluation of washing efficiency, as it is really hard to give a quantitative estimation of the dirt removed. To obtain the first design laws, feasibility tests have been carried out on dirty cockle samples and on real boat hulls with a laboratory ultrasonic device. The influence of a large number of parameters was tested such as transducer-probe distance, displacement speed and transmitted power. The obtained data allowed us to design an optimized cleaning device combining high efficiency and speed.

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This 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.