Application of optical remote sensing to the measurment of wave surface kinematics

Abstract

This research study focused on the development and application of a laboratory instrument utilizing real-time video in conjunction with image processing techniques to accurately measure 3-dimensional wave surface kinematics. This thesis presents the design and results of the instrument in its initial, 2-dimensional measurement, stage of development. The objective was to design a functioning laboratory instrument and use it to measure horizontal surface velocities on a series of waves. These results are compared to those of existing theoretical methods to determine both the accuracy and feasibility of the instrument. Measurement of horizontal surface velocities are conducted on a series of regular and irregular waves. Results of the regular wave measurements are compared to well established higher order wave theory to quantify the accuracy of the laboratory instrument. The results of the irregular wave measurements are compared to predicted velocity time series acquired from the Hybrid Wave Model, Wheeler Stretching and Linear Extrapolation. Adjustments are then made to the measured velocity time series to represent any drift currents that might be present in the flume that theory can not predict. Comparison of the adjusted time series are then made to those predicted by the three theoretical methods. Maximum and Minimum measured velocities for each wave set are also compared to predicted values. Comparisons between measured and theoretical values show that the instrument and the theoretical models are in agreement and thus the laboratory instrument is a capable means of accurately measuring wave surface kinematics. Results also show that considering the agreement between theory and measured values, when taking into account the excessive amount time required to produce velocities from the video images, the instrument, in its current form, is not a practical method for surface kinematic measurements. There is, however, enough evidence to show that expanding the instrument to include 3-dimensional measurement capabilities would produce a valuable laboratory tool.