Experimental study of blockage of random waves by counter currents

Abstract

From February to April 1999, wave-blocking experiments have been conducted at the Laboratory of Fluid Mechanics of the Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands as a part of the Ph.D. research of I.K. Suastika. Wave blocking is a special case of wave-current interaction. It can occur when waves are propagating against a counter of which the velocity is increasing in the wave propagation direction. Blocking occurs where the intrinsic wave group velocity (cg) is equal, but opposite in sign, to the mean velocity. The counter current velocity at the blocking point is called the blocking velocity. In this thesis the experiments are described and a part of the measurement data is analysed, especially the data concerning the blocking of irregular waves. The first objective of this research is to acquire quantitative data on partial and complete blocking. The second objective is to develop a model for wave blocking. The model should describe the wave field in a situation where blocking occurs. 80, for a given incoming (generated) wave field and counter current, the model should describe the wave field up to and at the blocking point. (And beyond, in cases of partial blocking.)