Water elevation measurements using binary image analysis for 2D hydrodynamic experiments

This paper presents an alternative and open-source methodology based on binary image analysis to measure water elevations in two-dimensional hydrodynamic experiments. The proposed methodology considers the three main stages of an artificial vision system: image digitalization, processing and analysis. In the image processing stage, binary images were obtained by intensity modulation and pseudo-color-based segmentation. The image analysis stage employs simplified morphological operations to measure water elevations at specified regions of interest in the binary images. The image processing and analysis stages were developed in scripts for the ImageJ open-source software. The applicability of the proposed methodology was verified by comparing measurements of water elevations obtained using the proposed approach and conventional wave probes during experiments of shipping water on a fixed structure. The experiments included cases where single-valued and double-valued water surfaces were observed. For all the test cases, the water elevation time series obtained using the proposed approach were in good agreement with the experiments before three-dimensional effects on flow were significant. For the case in which a double-valued water surface was observed, it was confirmed that the proposed procedure possesses the capability to measure the effective water height at specified regions of interest.