Shoaling and Decay of Two Wave Trains on Beach

Abstract

Shoaling and decay of irregular wave trains with two distinct frequency peaks are simulated in a wave flume. The relative energy in each wave train, the closeness of the frequency peaks, and the total wave energy were varied over 12 cases. Wave‐gauge measurements across the 1:30 plane slope in the flume show that linear superposition of single‐peaked wave trains or lumping all energy into the dominant wave train are not satisfactory representations of multiple wave trains. The measurements also show that the wave train with the low‐frequency peak dominates in the surf zone. Waves with the low‐frequency peak appear unaffected by the second wave train, but the high‐frequency wave train decays faster in the presence of the low‐frequency waves. The variation of wave height through shoaling and breaking depends on the relative amount of energy in each of the wave trains and the closeness of the peak frequencies.