Wave Measuring Instrumentation For Field Investigations On Breakers

As water-air-interaction cannot be simulated completely in a model, laboratory investigations on breakers can only be reliable to a certain extent. This is why comprehensive field investigations are necessary; a program of such field measurements was started on the isle of SYLT/NORTH SEA in 1971. The measurements analyzed were carried out in the surf zone during a severe storm surge. The measuring devices consisted of a two component electromagnetic current meter and a wave meter placed on the beach at a distance of 85 m from the coast line and another wave meter located 15 m offshore. In order to be able to use different analyzing methods the outputs of the measuring devices were fed simultaneously to a magnetic tape recorder. For the purpose of data processing on a PULSE HEIGHT ANALYZER the signals had been chopped by a frequency of 20 kilocycles. Thus the stochastic process could be displayed on a scope as histograms representing 10 minutes real time measuring periods. From the histograms statistical parameters are obtained to a high degree of accuracy. For the correlation of water levels and orbital velocities POWER SPECTRA, CROSS POWER SPECTRA, TRANSFER FUNCTIONS and COHERENCE FUNCTIONS are calculated by the use of a FOURIER ANALYZER.