Experimental validation of the plunger-type flow model for irregular waves

Abstract

In this paper, a study of irregular waves generated with a plunger-type wavemaker with the inclusion of mean flow is conducted along with an analysis of the standard plunger-type flow (PTF) model. It was determined that for high frequencies, the standard PTF model exhibits amplification which when compared to theoretical models for piston- and flap-type wavemakers is implausible. Therefore, a correction to the PTF model has been proposed for use with irregular waves that limits the value of the wave amplitude a to stroke amplitude s ratio a/s to one or less. Experimental validation of the correction is also given along with a study on the performance of the plunger system for generating the desired irregular Bretschneider wave spectrum. In this paper, multiple significant wave heights and peak frequencies are considered for no-flow and three mean flow cases. The experimental results showed that not only is the proposed correction valid for decreasing the percent error in the significant wave height but, plunger-type wavemakers are capable of accurately producing irregular spectra regardless of the inclusion of mean flow.