Bove A., De Luca F., Marsilia P.
The Ship Model Basin of Naples University Federico II: Facilities, Experimental Tests, Measurement Systems

This work presents the main facilities of the Naples Towing Tank, LEIN: the instruments and the potential of the laboratory are presented, highlighting some strategies to resolve critical points typical of the towing tank tests. As example we point the attention on three aspects, typically critical: towing point of planing vessels, the accuracy of wave spectra generation and the settings of the radii of gyration for the seakeeping models.

Laura Poggi, Tomaso Gaggero, Marco Gaiotti, Enrico Ravina, Cesare Mario Rizzo
Robotic inspection of ship structures: how to fill the gap between available technologies and current survey practices?

Adoption of Robotics and Autonomous Systems (RAS) in activities related to ship inspections has obvious potential advantages, but also shows some problems, ranging from ship-RAS interface to regulatory and legal viewpoints. The ROBINS project (ROBotics technology for INspection of Ships) is a collaborative project cofunded within the H2020 EU Research and Innovation programme call, aimed at filling the gap between current ship inspection requirements and available robotic technology. The present work aims at highlighting how human-made ship inspections can be improved using RAS, with equivalent results of the current practice, which indeed is rather satisfactory. In such a framework, a Testing Facility (TF) has been built up and it is still under development. Hence, the features of the TF where RAS will be tested and the testing protocols during trials are presented, showing how technological and regulatory gaps can be filled. Basically, RAS target will be to carry out inspections at the same quality level of humans ones.

Giorgio Tani, Michele Viviani, Marco Ferrando
Cavitation tunnel in Naval Architecture: from cavitation prediction to radiated noise

Cavitation tunnels represent one of the most important typologies of model testing facilities used in Naval Architecture. These facilities are employed to study the hydrodynamics of marine propellers, with special attention on cavitation and its side effects. These effects include: loss of propeller thrust and efficiency, erosion, inboard noise and vibration, underwater radiated noise. The latter aspect is one of the hot topics in the field of ship hydrodynamics because of the concerns related to its impact on marine life. This paper presents the general setup and test procedures used to predict the propeller radiated noise based on model tests. In addition, some of the main experimental issues related to these activities are described.

Salvador Barrera-Figueroa, Alper Biber, Ata Can Corakci, Alexander Golick, Stephen Robinson, Gary Hayman, Justin Ablitt, Silvano Buogo, Salvatore Mauro, Fabrizio Borsani, Salvatore Curcuruto, Markus Linné, Peter Sigray, Per Davidsson
Designing a comparison coupler for low-frequency calibration of hydrophones in air

Requirements of traceability for measurements of sound pressure in the maritime environment demand that hydrophones are calibrated to frequencies down to 20 Hz. A recently completed European project entitled Underwater Acoustic Calibration Standards for Frequencies Below 1 kHz (UNACLOW), within the European Metrology Programme for Innovation and Research (EMPIR) presented a proposal for some methods of providing traceability at that frequency range. One of these methods was based on direct comparison to reference microphones in an airfilled coupler. A design of the coupler was proposed by TUBITAK, and used by some participants in the project, including DFM. Preliminary results of the sensitivity of the hydrophone determined from measurements in the coupler showed that there was a growing deviation from the sound pressure uniformity assumption as the frequency increased. This limitation was solved using an ad-hoc correction based on known sensitivity values of a hydrophone at 1 kHz. Due to the hydrophone-specific nature of the correction, the design of the coupler was revisited so such a correction was not needed. This paper presents the new design of the coupler, and results of its application.

A. Bordone, F. Pennecchi, G. Raiteri, F. Reseghetti
ARGO floats vs. ship-based CTDs: an overall metrological comparison in the whole Mediterranean Sea

The widespread network of temperature/salinity profiling floats, known as Argo, has nowadays become a fundamental component of the ocean observing system. Since Argo floats usually are not recovered and should last up to five years without any re-calibration, their onboard sensors can reasonably suffer some drift and/or offset. During the years, very refined methods have been developed and implemented to post-process the Argo data, in order to correct the response of their profiling CTD (Conductivity – Temperature – Depth) sensors, in particular adjusting the salinity drift. The core of this delayed-mode quality control is the comparison of Argo data with reference climatology. At the same time, it’s still considered metrologically fundamental the experimental comparison of Argo profiles with quasi-collocated in space and quasi-simultaneous in time ship-based CTD profiles. In this paper an overall comparison of Argo floats vs. shipboard CTDs was made, in terms of temperature and salinity profiles in the whole Mediterranean Sea and under strict spacetime matching conditions.