Hydrodynamic Research of Marine Structures

Hydrodynamics plays a crucial role in the design and analysis of marine structures, as it involves the study of the motion of fluid and its interaction with various types of structures in a marine environment. Understanding these interactions is essential for ensuring the safety, effectiveness, and longevity of structures such as ships, offshore platforms, and underwater installations. The behavior of marine structures is significantly influenced by environmental factors such as waves, currents, and wind forces, which impose dynamic loads that can lead to structural fatigue or failure if not adequately accounted for. This Special Issue aims to bring together the latest advancements and insights in the field of hydrodynamics focused on marine structures, providing a platform for researchers to share their findings, methodologies, and applications.

Specific topics of interest for submission include the hydrodynamic characterization of marine structures, addressing the assessment and modeling of hydrodynamic loads. Understanding these loads is vital for engineers to design structures that can effectively withstand these forces under varying environmental conditions [1,2,3,4,5,6,7,8]. Another key area of interest is the design optimization and performance enhancement of marine structures focusing on the application of hydrodynamic research to optimize design and enhance the performance of these structures in terms of stability, safety, efficiency, and sustainability [9,10,11,12,13,14]. Furthermore, research investigating fluid–structure interactions—examining how marine structures respond to dynamic loads and the resulting vibrations or resonance—is essential for understanding and mitigating potential failure modes [15,16,17,18,19,20].

The high-quality papers published in this Special Issue are closely associated with many of the aforementioned aspects of hydrodynamic research concerning marine structures. These include novel techniques in the hydrodynamics of cylindrical and spheroid floaters, the analysis and design of offshore wind turbines, the consequences of mooring system failures, effective damage control strategies, the enhancement of vessel resilience, and the significance of seafloor characteristics in wave modulation. More specifically, the following contributions are included in this Special Issue.

The complex dynamics involved when a ship suffers damage is examined in [21], particularly focusing on the interactions between air and fluid in such critical scenarios. The authors conducted both experimental tests and numerical simulations to analyze how these interactions influence the ship’s stability and behavior in water. Their investigation highlights the significant role that air entrainment and fluid dynamics play in the response of damaged vessels, providing insights into the mechanisms that could lead to capsizing or sinking. The study concluded that air compressibility at various ventilation levels is important and should not be disregarded in damage assessments. Moreover, the interactions between air and fluid, which stem from different ventilation placements, must be taken into account. An analysis of the microscopic velocity field in fully ventilated scenarios shows that varying ventilation positions create different outflow paths for compressed air, leading to distinct forces acting on the hull. The findings of this research have important implications for maritime safety and ship design. By enhancing the understanding of air–fluid interactions, the study provides valuable information for developing more effective damage control strategies and improving vessel resilience. This research not only contributes to the field of naval architecture, but also aids in the formulation of guidelines for emergency procedures in the event of ship damage, ultimately enhancing the safety of maritime operations and navigation.

In [22], the effects of proximity to the sea surface on the hydrodynamic performance of submerged spheroidal bodies were investigated. The authors employ theoretical methods and numerical simulations to analyze the flow characteristics around the spheroid, focusing on parameters such as exciting forces and hydrodynamic coefficients. Their study reveals how surface proximity alters pressure distributions and flow patterns, leading to variations in hydrodynamic behavior that are critical for applications in marine engineering and underwater vehicle design. The current analysis confirms the occurrence of negative added mass and rapid fluctuations in the added mass and damping coefficients, which can be attributed to the free surface effect explained by the presence of near-resonant standing waves above the submerged body. The results of this investigation possess significant implications for various fields, including naval architecture, marine robotics, and environmental studies. By understanding the hydrodynamic responses of submerged objects near the sea surface, the research offers insights that can inform the design of submarines, underwater drones, and other marine structures to enhance their efficiency and maneuverability.

The work by Chang et al. [23] delves into the flow dynamics involving two cylindrical structures situated close to a wall. The authors utilize numerical simulations to investigate the wake patterns produced by these arrangements, as well as their influence on the surrounding fluid’s hydrodynamic characteristics. By analyzing the tandem and parallel configurations, the study reveals critical insights into how the proximity of the cylinders to each other and the wall alters the wake structures. For two tandem cylinders, three wake states are identified, with the downstream cylinder’s force coefficient primarily being affected by the upstream cylinder. In the case of two parallel cylinders, the wake exhibits four distinct modes based on spacing, revealing how wall effects impact the force coefficients under varying conditions. The findings of this research have practical implications for engineering applications involving cylindrical structures, such as offshore platforms, pipelines, and marine vessels.

Boo et al. [24] focus on the design considerations and technical specifications necessary for developing a tension leg platform (TLP) for floating wind turbines in Korea’s offshore environments. The authors present a conceptual framework for a 15 MW floating wind platform, which emphasizes stability and suitability for the specific environmental conditions prevalent in Korean waters. Through detailed numerical analysis, the study aims to address challenges such as wave forces, wind loads, and mooring dynamics to optimize platform performance, revealing several key findings regarding the maximum platform offset of both intact and damaged tendon cases; the dynamic amplification factor of tendon tension; and the mooring system’s stiffness with a damage tendon. Overall, all design criteria for the TLP have been met, confirming its viability for deployment in the typhoon-prone eastern offshore area of South Korea. Additionally, the proposed TLP design can serve as a valuable reference for future developments in floating wind energy systems globally, promoting sustainable energy solutions and facilitating the transition towards cleaner energy sources as countries increasingly prioritize renewable initiatives.

In their research article, Chen et al. [25] examine the consequences of potential mooring system failures in barge-type floating wind turbines. The study utilizes advanced dynamic modeling techniques to simulate the behavior of the floating turbine under various failure scenarios of a single- and double-mooring-line, exploring how such incidents can affect the platform’s stability and operational integrity. By assessing the dynamic response of the turbine to significant environmental forces, the authors highlight the criticality of robust mooring designs and the need for contingency planning in floating wind farm operations. The findings of this analysis highlight the impact of varying damping factors on wave elevation and impulse response function, finding that using the damping lid method effectively corrects overestimations of wave elevation and reduces oscillation amplitude. Furthermore, the insights gained from this research concerning the simultaneous failures of specific mooring lines greatly amplify the remaining lines’ tensions and may result in cascading failures, allowing engineers to devise more resilient mooring strategies and safety measures, ensuring the operational reliability of floating wind turbines in challenging marine environments.

Finally, Wong and Chow’s work [26] delves into the complex interactions between ocean waves and diverse underwater topographies including straight-line and concave/convex seafloors with differing inclinations. The study emphasizes the significance of seafloor characteristics in wave modulation, focusing on how different formations can affect wave height and energy as they approach the shore. By utilizing advanced modeling techniques, the authors provide insights into wave behavior, including swell propagation and overtopping, contributing to a better understanding of coastal hydrodynamics. Moreover, the research underscores the practical implications of these findings for coastal management and engineering. The results indicate a non-monotonic relationship between slope and wave dynamics; for mild slopes, run-up increases with slope, but decreases with more abrupt slopes. A monochromatic wave train test, resembling ocean swells from tropical cyclones, shows that convex profiles facilitate wave breaking further offshore, which enhances coastal protection by reducing the volume of water reaching the shore, while concave profiles lead to higher run-up and increased inundation risks. Their work serves as a valuable resource for predicting wave impacts in coastal areas and developing strategies for mitigating adverse effects, thereby enhancing the resilience of coastal environments against climate change and extreme weather events.

Enjoy reading this Special Issue on “Hydrodynamic Research of Marine Structures”.