Comparative Study of Water-Impact Problem for Ship Section and Wedge Drops
- Sa Young Hong (Korea Research Institute of Ships and Ocean Engineering) | Kwong-Hwan Kim (Korea Research Institute of Ships and Ocean Engineering) | Sung Chul Hwang (Korea Research Institute of Ships and Ocean Engineering)
- Document ID
- International Society of Offshore and Polar Engineers
- International Journal of Offshore and Polar Engineering
- Publication Date
- June 2017
- Document Type
- Journal Paper
- 123 - 134
- 2017. The International Society of Offshore and Polar Engineers
- CFD, ship-section drop, wedge drop, Water impact, comparative study
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- 53 since 2007
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A comparative study of a water-entry problem was conducted as a focused session of ISOPE-2016, Rhodes by the International Hydrodynamic Committee (IHC) of ISOPE. Thirteen institutions participated, and twenty different numerical results were investigated and compared with one another and with model test data. Some promising results were obtained even though there is still a long way to go to draw general conclusions. Four numerical cases were investigated, and several measures of comparison have been discussed.
Nowadays, computational fluid dynamics (CFD) approaches based on the viscous flow model have been emerging as an alternative tool to traditional potential flow analysis methods and model tests in offshore hydrodynamics. Recent findings on vortex-induced motion (VIM) model tests and sea trials imply that the model test approach cannot predict full-scale VIM due to significant scale effects (KS Kim et al., 2016; Kyoung et al., 2015). Aside from VIM, several effects need CFD power due to their capability for inherent strong nonlinearity and viscous flow dominant physical phenomena, for example, sloshing, slamming and green water impacts, roll damping, and low-frequency motion damping. KS Kim et al. (2016) focused on CFD capability for the design and analysis of offshore platforms by virtue of the rapid increase in the computational power of parallel processing and the matured experience with computational methods in CFD.
Unlike VIM and roll damping that are solely governed by fluid viscosity, impact loads due to slamming are much more complicated because of strong nonlinearity such as wave breaking and splash, which are not strongly dependent on viscosity. Therefore, a more systematic validation study is needed for the application of CFD to impact load analysis. The water entry of a wedge problem is a basic and classical impact load problem, which has been studied by means of numerical and experimental approaches. Numerical study models are categorized by potential flow model and viscous flow model.
Von Karman (1929) and Wagner (1932) first derived analytic solutions. Dobrovol’skaya (1969) then gave a similarity analytic solution. Zhao et al. (1997), Mei et al. (1999), and Malleron and Scolan (2008) conducted a study based on a generalized Wagner model. Korobkin (2004) and Tassin et al. (2014) made improvements on a numerical scheme based on a modified Logvinovich model. Recently, Semenov and Iafrati (2006) and Xu et al. (2008) derived analytic solutions to asymmetric wedge problems. Numerical results based on analytic solutions are very useful for the validation and accuracy of model test results, while the application is very limited to simple wedge-shaped sections.
|File Size||7 MB||Number of Pages||12|