Experimental study of wave action on a horizontal cylinder close to the seabed is presented. Tests were carried out in a laboratory wave flume, using a constant slope of 1/20 to simulate wave shoaling. The hydrodynamic forces have been measured for different positions of the cylinder above the bed and two different water depths. The results are analysed as extreme coefficients using a simple model to evaluate the horizontal velocity. The classical model of Morison et al. (1950) for the in-line force is also evaluated and we show that a simple wave theory taking into account more precisely the real nature of the flow field is able to represent the in-line force with good accuracy for low KC numbers.
The study of a horizontal cylinder with or without wall proximity effects is of great interest for ocean engineering. This subject has generated a lot of studies of different natures (theoretical, experimental or numerical). Most of these studies concern offshore conditions because of its importance for the petroleum and gas industry and only a few have focused on coastal conditions. In the framework of a research program which subject is the stabilisation of a marine pipeline in the coastal zone (Chevalier, 2000), we have carried out some experimental measurements of wave induced forces on a horizontal cylinder near a sloping bottom in a laboratory wave flume. After a short review of some papers of interest for our study, we present the experimental set-up and our data analysis method. This treatment requires the knowledge of the fluid velocity in the coastal zone to evaluate non-dimensional force coefficients. To do so, results of a comparison between the linear theory and an empirical theory (developed by Koyama and Iwata, 1986) are first presented.
