Vertical and horizontal structure in cross-shore flows: An example of undertow and wave set-up on a barred beach

摘要: Greenwood, B. and Osborne, P.D., 1990. Vertical horizontal structure in cross-shore flows: An example of undertow wave set-up on a barred beach. Coastal Eng., 14: 543-580. Eulerian measurements the horizontal, velocity field lowermost meter water column, association with waves mean elevation surface, across nontidal, low relief, surf-zone reveal: (a) spatially coherent patterns timeaveraged first, second third moments field, which vary temporally direct response to incident waves; (b) large asymmetries flow offshore-directed flows upto ~ 0.20 m s-a onshore-directed skewness (the moment normalized by standard deviation) + 0.60; (c) decrease oscillatory (measured deviation field) increase towards surface; (d) fourth-order polynomial provides best fit set-up, reflecting influence variable energy dissipation due topographic controls breaking; (e) significant linear correlations exist between velocities maximum still-water surface near shoreline (upto 82% observed variability former can be accounted for regressions ); (f) is highly correlated height (86% regression); (g) gradients are significantly less than those predicted function beach slope as originally proposed Bowen et al. even using an appropriate breaking criterion (0.4-0.6) spilling breakers recorded. Cross-shore circulation over nearshore predominantly two-dimensional outer bar this case study. The near-bed responding balance wave-generated, depth-dependent momentum flux directed onshore, stress induced onshore mass transport under wind, hydraulic pressure gradient water.level.