Seiching in a Large Wave Flume

INTRODUCTION The Cross-shore Transport Experiment (CROSSTEX) is a multi-investigator, multi-university, scientific research project centered around a coordinated series of near-prototype scale experiments that were conducted at Oregon State University's O.H. Hinsdale Wave Research Laboratory (HWRL) during the summer of 2005 (Maddux et al, 2006). The experiments took place in the 104m long, 3.7m wide and 4.6m deep Large Wave Flume (LWF) on a movable bed consisting of medium sand (^50=0.22 mm). The objective of our portion of the experiments was to obtain high-resolution observations related to onshore and offshore sandbar migration. The analysis of seiching in the LWF was not a primary objective of our experiments; however, our early analysis of the data suggested they contained some unexpected behavior in regards to basin seiching. Herein, we have pursued a detailed analysis of the observed low-frequency motions as an "experiment of opportunity". The experimental conditions consisted of irregular waves generated by the paddle-type wavemaker with a range of peak periods (3-8 sec) and rms wave heights (0.3m to 0.6m) depending on whether erosive or accretionary conditions were desired. Observations of the hydrodynamics were carried out using instruments mounted onto the walls of the flume, suspended from a movable carriage, and remotely observed by video cameras as shown in Figure 1. The present analysis will utilize a limited number of Nortek Vectrino