A numerical investigation of interactions between extreme waves and a vertical cylinder
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A numerical investigation of interactions between extreme waves and a vertical cylinder * Qun-bin Chen, Yu-xiang Ma, Guo-hai Dong, Xiao-zhou Ma, Bing Tai, Xu-yang Niu State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China (Received February 10, 2019, Revised October 15, 2019, Accepted October 21, 2019, Published online September 15, 2020) ©China Ship Scientific Research Center 2020 Abstract: In this paper, the interactions between extreme waves and a vertical cylinder are investigated through a 3-D two-phase flow model. The numerical model is verified and validated by experimental data. Then, two factors are considered, the global wave steepness and the frequency bandwidth of the wave groups, in the studies of the in-line wave forces and the wave run-up around a cylinder. It is found that both the in-line wave forces and the wave run-up are remarkably increased with the increase of the global wave steepness, whereas the effect of the frequency bandwidth on the in-line wave forces is relatively weak in comparison with its effect on the wave run-up. The minimum and maximum wave run-ups are located in the directions of 22.5 and 180 with respect to the direction of the incident waves, respectively. Additionally, a new empirical formula is proposed for predicting the in-line wave forces by using only the free surface elevations around the cylinder. The results of the formula agree well with the simulation results. Key words: Extreme waves, vertical cylinder, in-line wave force, wave run-up
Introduction With the growing demand for energy, many countries pay a special attention to renewable energy in recent years. Among the kinds of renewable energy, the wind energy is clean, free and available in any place where there are relatively strong winds. Compared with the inland areas, the offshore regions have more strong and stable wind resources. Therefore, offshore wind turbines are widely applied in converting kinetic energy in wind into mechanical power and then further into electric energy. However, these structures are always exposed to ocean waves in offshore regions and are typically supported by vertical cylinders. As a result, a clear understanding of wave loads and run-up on vertical cylinders is an important issue[1]. Extreme waves are large waves with extraordinary large crests, significantly higher than the * Project supported by the National Key Research and Development Program of China (Grant No. 2017YFC1404200), the National Nature Science Foundation of China (Grant Nos. 51679031, 51720105010 and 51979029) and the Liaoning Revitalization Talents Program (Grant No. XLYC1807010). Biography: Qun-bin Chen (1988-), Male, Ph. D. Candidate, E-mail: [email protected] Corresponding author: Xiao-zhou Ma, E-mail: [email protected]
background waves. They can damage structures with the loss of their structural functionality. Due to the potential hazard caused by extreme waves, their impact is an active research subject in ocean and coastal engineering[2]. Genera
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