Kinematics of Experimentally Generated Severe Wave Conditions and Implications for Numerical Models

Abstract

An experiment was performed to measure and characterize wave kinematics in a large-scale experimental basin. The primary objective was to measure and characterize the wave kinematics of both regular waves of varying steepness and scaled irregular seas with embedded large-amplitude wave groups. The secondary objective was to provide a validation data set for wave theory and numerical simulation tool development. Measurements included free surface elevations and velocity field measurements under the free surface using particle image velocimetry (PIV). A discussion of free surface elevation data, the effect of wave steepness on the velocity profile of regular waves and an introduction to the analysis of the wave kinematics of the embedded wave groups was presented in a previous paper by the authors (OMAE2010-20240). The current paper expands on the analysis presented in the previous paper, providing a discussion of the effect of wave group composition, wave group location within irregular seas, and seaway scaling on the kinematics. This experiment is part of an ongoing effort at the Naval Surface Warfare Center Carderock Division (NSWCCD) to improve predictions and measurement of ship motions in waves and assess the dynamic stability and seakeeping performance of naval ships. NSWCCD has developed a deterministic wave generation method to be used in its seakeeping basin facility. The exploration of the above factors provides a better understanding of the employed method and its effectiveness for creating wave groups. Specifically, to model realistic severe conditions that a ship may encounter. These findings, in turn, lead to the possibility of improvements to current model testing methods at NSWCCD. In addition to assessing the experimental methods employed, the experimental data set can also be used to validate and improve current numerical wave models for ship motions prediction. A comparison of the measured wave elevations and kinematics with a pseudo-spectral numerical wave model is also presented and discussed.