Wave Flume Measurement Using Image Analysis

Abstract

Wave observation represented water surface elevation at a reference point is basic and essential data for ocean and coastal engineering that is mostly measured with traditional wave gauges, for instance capacitance, resistance and conductivity types. Therefore, accuracy and exactness are the most important aspects of data acquisition systems. In this study, we focus on the development of image processing techniques for wave measurement in a wave flume as a tool to replace traditional wave gauges, which are complicated to use, costly and intrusive. Recently, image processing techniques have been developed for utilization in various tasks. The main factors that influence the accuracy of these techniques are image quality, algorithm performance and exact calibration. Image processing techniques based on edge detection algorithms were used to measure waves in the laboratory with a camera. The experimental results showed the agreement of water surface elevation from both measurement methods. The average wave height and average wave period of regular wave obtained from the zero up-crossing analysis were different by less than 10% and 1% respectively compared with traditional wave gauges. Moreover, this algorithm can also measure irregular waves in hydraulic laboratories as well. Hence, this approach is a new, alternative tool for use in wave flume measurement, with good results.

A simplified and open-source approach for multiple-valued water surface measurements in 2D hydrodynamic experiments

“…This procedure allows the continuous contours (i.e., contours with the same thickness) in the flow surfaces to be obtained. One difference between the proposed approach to recover the contours of fluids of interest and techniques commonly used for edge detection, such as Prewit, Canny or Sobel filters (e.g., [23]), can be the ability to perform a global operation through a Boolean difference instead of an iterative differentiation. This may ensure the continuity of the contour thickness throughout the image in a single iteration, reducing computational effort and avoiding the influence of noise on the contours detected.…”

“…It has been demonstrated by several authors, including [7,[22][23][24], that the use of image-based methodologies to extract 2D hydrodynamic measurements is a powerful alternative due to the ease of setting a non-obstructive experimental setup and to the availability of methods to acquire, process and analyze the image data. Some of these works have been concerned with single-valued water surface measurements, such as [25], who applied the wavelet transform approach in simplified wave flume experiments to analyze the wave profile of regular and irregular waves.…”

“…Some of these works have been concerned with single-valued water surface measurements, such as [25], who applied the wavelet transform approach in simplified wave flume experiments to analyze the wave profile of regular and irregular waves. Later, an image processing technique based on Canny edge detection was proposed by [23] to obtain wave profiles over an entire stack of images.…”

Measuring the Wave Height Based on Binocular Cameras

“…Fedele [16] introduced an epipolar constraint to decrease the search range and matching time by investigating the stereo matching component of the photogrammetric measurement technique. Viriyakija [17] proved that binocular stereo measurements work well at acquiring wave height measurements; the stereo photogrammetric measurement method agreed well with the traditional wave height metre in a tank. Chatellier [18] used image processing for the first time by using an edge detection algorithm to reconstruct the free surface shape and an image correlation algorithm to calculate the wave velocity; however, this method was highly dependent on the definitions of the camera parameters.…”

Experimental Investigation of a Concept Wave Energy Converter for Harnessing Low Amplitude Sea Waves

“…Each experimental run lasted sixty seconds. This approach of wave height measurement was referred to in the literature as the visualization method and was similar to methods employed by [23] and described by [24].…”