REFLECTION ANALYSIS WITH SEPARATION OF CROSS MODES

Abstract

During physical model tests in a wave flume an accurate determination of the incident waves is crucial. Normally, the determination of the incident waves is conducted by a traditional reflection analysis and in this case the influence of any cross modes is ignored. The present paper concerns the advantage of including the possible presence of cross modal activity in the reflection analysis when determining the incident waves. It is shown both analytically and numerically how the cross modes affect the results of a traditional reflection analysis, and that ignoring cross modal activity can lead to an inaccurate determination of the incident waves. A new method is introduced where the cross modes are separated in the reflection analysis. This method requires at least three wave probes while a traditional reflection analyses only requires two wave probes. The applicability of the method is verified both numerically and by physical flume tests at the Hydraulic Laboratory of Aalborg University, Denmark. In both cases the new method seems to give very good results.