Influence of wave steepness on force coefficient for square and rectangular caissons

The influence of wave steepness on force coefficient for large square and rectangular section caissons has been studied experimentally and compared with the results obtained using the modified linear diffraction theory proposed by Mogridge and Jamieson. The square caisson was tested for orientations of 0°, 15°, 30° and 45° of its side with the wave front and the rectangular caisson was tested for two aspect ratios of 3/4 and 4/3 for normal incidence of waves on its side. The force coefficient was found to increase in wave steepness, H/L. The agreement between the theory and experiment was found to be good for large values of relative caisson size, b/L (greater than 0.1) and for values of H/L up to 0.08. However, greater deviations occurred for small values of b/L and increasing values of H/L due to flow separation and non-linearity of the actual process. The results for normal incidence of waves on rectangular caissons are in line with those of square caissons. The effect of varying orientation of the square caisson relative to α = 0° on force coefficient was more pronounced at higher values of H/L. © 1981 Taylor & Francis Group, LLC.