ABSTRACT

The present study compares the CFD analysis on breaking wave impact loads on a circular cylinder. The wave impact load due to breaking waves is critical on offshore structures, however it is difficult to obtain the magnitude of impact load accurately both in experiments and calculations. Recently, a model test on the impact load under breaking waves on a circular cylinder was conducted in KRISO, Korea. CFD is widely adopted thanks to noticeable increase of computing power. In the present study, various CFD research groups have participated. The feasibility of CFD analysis on impact loads by breaking waves is discussed based on numerical results of wave elevation and wave impact load with comparison of model test result. The peak value and impulse of impact loads are compared as well as the rise and decay time.

INTRODUCTION

It is well known that the impact loads by breaking wave is significantly higher than peak loads by non-breaking wave with the same wave height(Basco and Niedzweeki, 1989; Kjeldsen et al., 1986). If the breaking waves attack offshore structures or ships, the damage will be critical. Therefore, it is necessary to accurately estimate the impact load due to breaking waves. Since the breaking wave is strongly nonlinear phenomena in nature, only limited model tests or analytic methods were possible to analyze the breaking wave phenomena. Analytic methods for the impact problem were proposed by von Karman (1929), Wagner (1932), Cointe (1989), and an empirical formula by Goda et al. (1966). Various model tests were performed because of limited application of analytic methods. Irschik (2004) studied wave impact forces on the circular cylinder and the results of the model tests were compared with curling factors by Von Karman (1929), Wagner (1932), Cointe (1989) and Goda et al. (1966). Wienke and Oumeraci (2005) performed an experiment in a large wave channel and they summarized characteristics of impact force according to the shapes of incoming waves. Navaratnam et al. (2013) and Aashamar (2012) measured slamming forces on a jacket platform and compared them with analytic solutions of Wienke and Oumeraci (2005). Navaratnam et al. (2013) and Aashamar (2012), Sawaragi and Nochino (1984) and Ros (2011) presented the scale effect of the slamming forces by model tests. Recently CFD analysis has been applied to the analysis of impact load of breaking waves. However, there are not sufficient standards or guidelines to analyze the wave impact problem of breaking waves based on CFD analysis. In this study, the accuracy of CFD analysis is evaluated by comparing various CFD analysis results with the results of model test. Based on these, the feasibility of CFD analysis on impact loads of breaking waves is discussed.

This content is only available via PDF.
You can access this article if you purchase or spend a download.