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Particle image velocimetry (PIV) is a widely used experimental technique in ocean engineering, for instance, to study the vortex fields near marine risers and the wake fields behind wind turbines or ship propellers. However, the flow fields measured using PIV in water tanks or wind tunnels always have low resolution; hence, it is difficult to accurately reveal the mechanics behind the complex phenomena sometimes observed. In this paper, physics-informed neural networks (PINNs), which introduce the Navier–Stokes equations or the continuity equation into the loss function during training to reconstruct a flow field with high resolution, are investigated. The accuracy is compared with the cubic spline interpolation method and a classic neural network in a case study of reconstructing a two-dimensional flow field around a cylinder, which is obtained through direct numerical simulation. Finally, the validated PINN method is applied to reconstruct a flow field measured using PIV and shows good performance. [ABSTRACT FROM AUTHOR]

An experimental investigation on the vortex/wake-induced force of double unequal-diameter cylinders in tandem was performed. In the experiment, the upstream-to-downstream cylinder diameter ratio was 1.569, and the gap spacing ratio between the cylinder models ranged from 3 to 8. Under uniform flow with Reynolds number up to 11 328, the strains caused by the vortex/wake-induced vibrations were measured for the double flexible cylinders. Based on the measured strains, the displacements were reconstructed with the mode superposition method. Then, the vortex/wake-induced forces were obtained inversely. Subsequently, the time-varying excitation and added mass coefficients were identified by the forgetting factor least squares method. The results show that the wake-induced force coefficient and excitation coefficient of the downstream cylinder are smaller than those of the single cylinder, while the added mass coefficient becomes larger. In addition, the downstream cylinder under frequency capture can absorb a higher proportion of energy from the wake to excite larger vibration amplitudes, especially in the in-line direction. [ABSTRACT FROM AUTHOR]