PhD defence Sung-Jin Choi accomplished

Sung-Jin Choi defended his PhD thesis: “Breaking Wave Impact Forces on an Offshore Structure The effect on dynamic amplification due to the structure’s vibration on breaking wave impact”. 

The defence was held on Thursday 21st August at University of Stavanger. The evaluation committee was comprised of Professor Carlos Brebbia, Wessex Institute of Technology, UK, Dr. Jørgen Ranum Krokstad, Statkraft, and Professor Jasna Bogunovic Jakobsen, UiS (administrator). Choi's supervisor has been Professor Ove Tobias Gudmestad, UiS. leading the disputas was Professor Chandima Ratnayake, UiS.


Access to Choi's PhD thesis can be found here.


The effect of the dynamic amplification due to the structure’s vibration on the breaking wave impact is studied. A 3D numerical model, based on solving the viscous and incompressible Navier-Stokes equations and the volume of fluid method (VOF), is employed to estimate the breaking wave impact forces on vertical and inclined piles. The computed forces are compared with the results of hydraulic model tests. However, because the piles installed in the numerical model are modeled as rigid objects, it is not possible to make a direct comparison between the CFD (Computational Fluid Dynamic) results and the experimental data. A force separation procedure is used for the experimental data. A low pass filter and EMD (Empirical Mode Decomposition) are employed for removing the effect of dynamic amplification in the experimental data, and the filtered results are compared with the numerical results. Based on the results, dynamic amplification factors (DAF) are estimated for these particular structures. Moreover, Duhamel integral are used to reproduce dynamic breaking wave forces (i.e., net breaking wave force + the force which is the amplified component due to the structure’s vibration) based on the breaking wave forces calculated by the CFD model. The reproduced results are compared with the unfiltered experimental data for the verification of the method stated above.





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