Eulerian measurements of horizontal accelerations in shoaling gravity waves

Abstract

Laboratory and field measurements of suspended sediment in the nearshore suggest that fluid accelerations are an important factor in sediment transport by oscillatory waves. Here, Eulerian accelerations of the cross‐shore velocity are calculated from measurements of velocity obtained by an array of bottom‐mounted electromagnetic flow meters spanning a natural surf zone. Large shoreward accelerations of brief duration are associated with the steep front faces of both near‐breaking and breaking waves. Weaker offshore accelerations of longer duration occur during passage of the more gently sloped rear faces. The acceleration field is thus strongly skewed in the shoreward direction. Power spectra and bispectra indicate, as expected, that statistics of the acceleration field are significantly influenced by high‐frequency motions but are rather insensitive to surf beat.