A NEW METHOD FOR THE GENERATION OF 2ND-ORDER RANDOM WAVES

In order to prevent the generation of spurious free sub- and superharm onics of random waves in a laboratory channel, the control signal for the wave board has to be derived according to a higher-order wave theo ry. An expression for this control signal has been derived with the pe rturbation method of multiple scales. It is much less complex and requ ires less computation time than the expressions obtained from the full second-order theory. The new method for second-order subharmonics was verified experimentally for waves with bichromatic and continuous fir st-order spectra. The data were analysed with the complex-harmonic pri ncipal-component analysis to reduce the influence of noise.