Simultaneous, non-intrusive stereo-refraction and stereo-PIV measurements around a boat in a towing tank

Abstract

This study focuses on the hydrodynamic effects generated by a displacement of ship model in a confined channel, based on the simultaneous measurement of the flow field velocity and free surface deformation. To this end, an experimental set-up combining stereoscopic particle image velocimetry (stereo-PIV) and stereo-refraction measurements has been developed. The simultaneous application of these two optical methods presents significant experimental challenges, particularly in terms of optical alignment, calibration, and synchronization of multi-camera systems. The paper provides a detailed analysis of the measurement uncertainties of each method, extending this analysis to the global wake reconstruction. The influence of lateral confinement was studied by carrying out experiments at six sailing speeds. These speeds corresponded to Froude numbers ranging from 0.20 (subcritical) to 0.80 (transcritical). The experiments were repeated for three channel widths (0.5 m, 1.0 m and 1.5 m). The results highlight key hydrodynamic phenomena, such as rip currents and jet-like wake structures, as well as changes in vertical fluid velocities. These phenomena are all modulated by sailing speed and confinement.