Experimental Variation of Focusing Wave Groups for the Investigation of Their Predictability

In deterministic model testing, focusing wave groups are used for the simulation of dedicated wave environments. They are characterized by the transient appearance of one relatively steep wave crest. The phasing of the wave components which leads to an exact focusing in one point in time and space is strongly dependent on the correct modeling of the wave phase velocity while the position of the focusing point depends on the wave group celerity. For wave generation purposes, the calculation of a wave maker control signal based on a target wave train at a desired position in the tank (inverse or backward modeling) is of crucial importance. Numerical wave tanks and empirical approaches are often calibrated based on wave characteristics measured in a particular tank. This paper presents model test results for the variation of frequency range, steepness and focal point of focusing wave groups at intermediate water depth. The measured characteristics are compared to predicted parameters.