Abstract
A new system for estimating the synthetic parameters of sea states during physical investigations has been implemented. The technique proposed herein is based on stereographic analysis of digital images acquired with optical sensors. A series of ad hoc floating markers has been made and properly moored to the bottom of a large wave tank to estimate the synthetic parameters of generated waves. The implemented acquisition system and the proposed algorithm provide automatic recognition of all markers by a pair of optical sensors that synchronously captures their instantaneous location and tracks their movements over time. After transformation from the image to the real-world coordinates, water surface elevation time series have been obtained. Several experimental tests have been carried out to assess the feasibility and reliability of the proposed approach. The estimated wave synthetic parameters have been then compared with those obtained by employing standard resistive probes. The deviation were found to be equal to ~6% for the significant wave height and 1% for peak, mean, and significant wave periods.
Highlights
In coastal physical modeling, the estimation of synthetic parameters of sea states, such as significant height, either peak or significant wave period, and propagation direction, is one of the main tasks
This paper aims to assess the feasibility of a noninvasive approach to get a reliable estimation of synthetic wave parameters when large wave tanks deployed in indoor laboratories are used
Nine floating markers have been deployed at the nodes of a grid in the wave tank; two cameras, whose technical features are reported in Table 1, have been placed on a steel bar at a mutual distance of ~70 cm so that both of them can frame the whole markers grid
Summary
The estimation of synthetic parameters of sea states, such as significant height, either peak or significant wave period, and propagation direction, is one of the main tasks (see, e.g., in [1,2,3]) Their estimation is a preliminary action for all activities typically carried out within the frame of experimental investigations. Wave parameters are usually inferred from data collected employing either capacitive or resistive Eulerian probes (see, e.g., in [7]) characterized by simple operating principles and easy-to-build supporting frames They are mainly used because they allow a reliable measure of the free surface elevation in a Eulerian reference frame and for their relative simplicity. Their intrusiveness is not negligible as they could perturb the investigated wave field, especially in large wave tanks due to the supporting frames for instruments positioning and sensors themselves
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