Wave absorbers installed in front of revetments are effective in reducing wave overtopping and inundation caused by periodic waves. The wave absorbers’ mechanism of reducing wave overtopping and inundation caused by long-period waves such as tsunamis and storm surges is not clearly understood. This study conducted a physical modeling test and numerical analysis based on a large eddy simulation model using in-house code to examine the characteristics of wave overtopping and inundation according to the revetment type for solitary waves. In a vertical revetment (VR), the dominant vertical velocity of the solitary wave cannot bend at a right angle during overtopping, causing flow separation to occur at the crest, which leads to increased drag and vorticity. In a wave absorbing revetment (WAR), the flow cross-sectional area decreases along the slope of the wave absorber, causing the flow velocity of the solitary wave to increase and the horizontal velocity to be dominant during the overtopping and inundation process. In contrast with the general wave overtopping characteristics of periodic waves, the maximum overtopping water surface elevation in front of the vertical wall is higher in a VR than in a WAR. However, the order of maximum inundation heights reverses as the wave propagates inland.
This paper employs the third-generation simulating waves nearshore (SWAN) ocean wave model to estimate and analyze storm waves induced by Typhoon Bolaven, focusing on its impact along the west coast and Jeju Island of Korea. Utilizing reanalyzed meteorological data from the Japan Meteorological Agency meso scale model (JMA-MSM), the study simulated storm waves from Typhoon Bolaven, which maintained its intensity up to high latitudes as it approached the Korean Peninsula in 2012. Validation of the SWAN model against observed wave data demonstrated a strong correlation, particularly in regions where wind speeds exceeded 20 m/s and wave heights surpassed 5 m. Results indicate significant storm wave heights across Jeju Island and Korea's west and southwest seas, with coastal grid points near islands recording storm wave heights exceeding 90% of the 50-year return period design wave heights. Notably, specific grid points near islands in the northern West Sea and southwest Jeju Island estimated storm wave heights at 90.22% and 91.48% of the design values, respectively. The paper highlights the increased uncertainty and vulnerability in coastal disaster predictions due to event-driven typhoons and emphasizes the need for enhanced accuracy and speed in typhoon wave predictions amid the escalating climate crisis.
31 October 2024 in Journal of Ocean Engineering and Technology
This study examined the collision dynamics between tsunami-driven drifting containers and port cranes, prompted by risks from the recent 7.6 magnitude earthquake and tsunami off Noto Peninsula, Japan. Hydraulic experiments were conducted to analyze container drift and collision forces using motion analysis software (DIPP-Motion) and a load cell installed on a crane leg model. The key parameters included the tsunami wave height, container weight (empty and loaded), initial position, and revetment type. The results suggested that higher tsunami wave heights led to more extraordinary inundation, allowing containers to float more efficiently, reducing bottom friction, and increasing drift speed and collision forces. The collision speeds ranged from 1.59 to 2.48 m/s, with collision forces of 45.18 to 77.68 N, representing increases of 6.45 to 15.58 times than no object. Heavier containers required deeper water to float, resulting in lower drift and collision speeds (0.88–0.89 times that of lighter containers). The wave-absorbing revetment caused higher flow velocities, producing collision speeds and forces 1.32–1.48 times greater than the vertical revetment. These findings highlight the importance of considering the tsunami magnitude, container weight, initial position, and revetment type in design, with face-to-face contact conditions crucial for estimating the maximum collision forces and preventing future tsunami damage.
31 December 2021 in Journal of Ocean Engineering and Technology
As the size of ships increases, the size and output power of their thrusters also increase. When a large ship berths or unberths, the jet flow produced from its thruster has an adverse effect on the stability of quay walls. In this study, we conducted a numerical analysis to examine the impact of the thruster jet flow of a 30,000 TEU container ship, which is expected to be built in the near future, on the stability of a quay wall. In the numerical simulation, we used the fluid–structure interaction analysis technique of LS-DYNA, which is calculated by the overlapping capability using an arbitrary Lagrangian Eulerian formulation and Euler–Lagrange coupling algorithm with an explicit finite element method. As the ship approached the quay wall and the vertical position of the thruster approached the mound of the quay wall, the jet flow directly affected the foot-protection blocks and armor stones. The movement and separation of the foot-protection blocks and armor stones were confirmed in the area affected directly by the thruster jet flow of the container ship. Therefore, the thruster jet flows of ultra-large ships must be considered when planning and designing ports. In addition, the stability of existing port structures must be evaluated.
24 April 2024 in Journal of Earthquake and Tsunami