A METHODOLOGY FOR MEASURING THE VELOCITY AND THICKNESS OF WAVE-INDUCED UP-RUSHING JETS ON VERTICAL SEAWALLS AND SUPERSTRUCTURE

Abstract

Waves breaking on vertical seawalls result in up-rushing water jets with high velocities, which in turn lead to large overtopping rates and pose a serious threat to pedestrians, vehicles or any infrastructure in the vicinity of the seawall. Nevertheless, knowledge on the characteristics, namely the velocity and thickness, of such jets is scarce. Based upon recent experiments in the Large Wave Flume (Großer Wellenkanal, GWK) of Forschungszentrum Küste (FZK) the current paper proposes a semi-automated methodology for measuring velocity and thickness of up-rushing jets. The methodology was applied on cases considering waves ranging from nonbreaking to nearly and strongly breaking and yielded encouraging results. With regards to the velocities a good repeatability is reported for non-breaking waves, while for breaking waves velocities are, as anticipated, observed to depend on the intensity of breaking. When the thickness is concerned, user based decisions are required as the selection process is drastically affected by the increased air content of the up-rushing jet.