Wave Runup on Vertical Cylinders

Wave height at a point on vertical cylinders is measured as a function of the orientation angle, α, between the normal from the point on the cylinder and the direction of travel of a single periodic train of waves. The wave height distribution, H(α), has a broad maximum around α = 0° (facing into the waves) and a more restricted maximum at α = 180° . The maximum at α = 0° increases with wave height in all cases, and the superelevation has about the magnitude of the velocity head in the wave crest. In 21 different H(α) for which it is possible to determine the axis of symmetry by a simple objective test, 14 H(α) have axes of symmetry within ± 3° of the direction of wave travel. Most of the variation in H(α) is due to variation in crest elevation; trough elevation remains relatively constant for the 360° range of a. The shape of H(α) depends more on height and cylinder cross section than on period, although the variation in H(α) as a function of cross section is significantly less than the extreme variations in tested cross sections. Applications of these results to wave direction measurement and to interpretation of wave records from surface-piercing wave gages are discussed.