Oblique Reflection Characteristics of Rubble-Mound Structures

Abstract

An experimental investigation of the reflection of obliquely incident waves from a model rubble-mound breakwater is described. In regular wave tests, the wave height, wave period, and angle of incidence were varied in order to determine relationships between the reflection characteristics and parameters describing the incident waves. For these tests, a least-squares fit to measurements from three wave probes was used to estimate the reflection coefficient and the phase angle of the reflected wave train. Results show that both the reflection coefficient and the reflected phase lag are noticeably dependent on the angle of incidence and that the variation with angle of incidence further depends on the depth to wavelength ratio. Reflection coefficients estimated from the analysis of irregular wave tests are also presented and are compared to reflection coefficients measured in regular wave tests, showing good agreement. For one test with multi-directional waves, directional spectra of the incident and reflected wave fields were obtained using a maximum likelihood fit to measurements from five wave probes, and these indicate increased directional spreading of the reflected wave field relative of that of the incident wave field.