This study aims to investigate how quasi-3D spiral acoustic black holes (Q-3D SABHs) reduce vibrations in flat plate structures. It seeks to provide a new technical approach for designing ship plate structures with improved vibration damping. With the increasingly stringent requirements for noise and vibration control in marine engineering, this study addresses the need for efficient and broadband vibration reduction methods.

To achieve this objective, a new configuration of the Q-3D SABH is proposed to achieve effective broadband vibration reduction. A detailed finite element computational model of a flat plate with attached Q-3D SABH structures is developed. The vibration response characteristics of the plate are systematically analyzed through numerical simulations. Furthermore, the structural intensity distribution and modal loss factors are calculated to investigate the underlying damping mechanisms and the effectiveness of energy convergence and dissipation induced by the Q-3D SABH. Comparative analyses are also conducted to evaluate the performance of the Q-3D SABH against conventional vibration damping methods, such as mass blocks, traditional damping materials, and one-dimensional spiral acoustic black holes (1D SABH) with equal mass.

The results demonstrate that the Q-3D SABH exhibits significantly better vibration damping performance than conventional treatments, such as adding mass blocks or using traditional damping layers, and also outperforms 1D SABH of the same mass. Specifically, in the low-frequency band, the Q-3D SABH configuration effectively reduces the mean-square vibration velocity level of the flat plate by more than 10 dB. In the mid- and high-frequency bands, the vibration damping performance is even more significant, achieving reductions of over 15 dB. Across the entire frequency range analyzed, the total vibration level is reduced by 15.05 dB. Moreover, compared to 1D SABH structures of equivalent mass, the Q-3D SABH demonstrates superior damping performance, particularly in the mid- and high-frequency ranges.

The study concludes that the Q-3D SABH structure has an excellent ability to converge and dissipate bending wave energy. The Q-3D SABH structure achieves outstanding broadband vibration reduction, especially at low frequencies, which are often challenging for traditional damping methods. These findings provide theoretical and technical support for the innovative design of vibration and noise control solutions in ship plate structures and other engineering applications where lightweight and efficient damping is critical. This research highlights the promising application potential of Q-3D SABH in advancing vibration damping technologies for large flexible structures.

In modern naval warfare, advancements in weaponry have significantly increased the vulnerability of ships to explosion impacts. Precision-guided weapons, in particular, pose a significant threat, as internal explosions within ship cabins can cause extensive damage to thin-walled structures. This damage not only compromises the ship's structural integrity but also affects its overall functionality and safety. To accurately assess a ship's ability to withstand such damage and make informed battlefield decisions, it is crucial to evaluate the residual load-bearing capacity of damaged structures under complex sea conditions. This analysis is essential for evaluating the ship's damage tolerance and determining its ability to safely return to port.

This study focuses on the behavior of hull plates damaged by in-cabin explosions. A series of meticulously designed model tests were conducted, aiming to analyze the residual load-bearing capacity of thin plates exhibiting dent damage under biaxial compression. The use of biaxial compression is highly relevant, as it replicates the complex stress states experienced by ship hulls in actual sea conditions. To measure the detailed mechanical behavior of the damaged plates, the digital image correlation (DIC) method was employed. This advanced technique enabled the creation of a three-dimensional full-field strain measurement system, which recorded the out-of-plane deformation of the plates with high precision. By analyzing this data, the study explored the failure modes of dent-damaged thin plates under biaxial compression, illuminating the mechanisms through which such damage progresses and ultimately leads to structural failure.

The experimental results provided significant insights into the behavior of damaged thin plates under biaxial compression. A key finding was that, regardless of the applied loading ratio, the presence of dent damage led to a substantial reduction in the residual load-bearing capacity of the thin plates. In some cases, this reduction reached up to 19.96%, demonstrating the severe impact of even minor damage on the structural performance of the plates. Furthermore, all tested plates ultimately failed due to significant plastic deformation at the intersection of the loading edges, which underscores the localized nature of the damage and its catastrophic consequences for structural integrity. Another key finding was that an increase in the load at one end of the biaxial compression resulted in a notable decline in the ultimate bearing capacity at the other end.

This study provides valuable insights into assessing the damage survivability of ships under complex stress conditions. The findings help naval personnel better understand the structural state of damaged ships, enabling them to make informed decisions regarding mission continuation or safe return to port. Additionally, the research provides a basis for future research focused on optimizing ship structural design and enhancing damage-tolerance capabilities. Overall, this study plays a vital role in ensuring the safety and operational effectiveness of ships in combat and their safe return to port.

This study analyzes the influencing factors of the aeroacoustic noise of cruise ship chimney exhaust pipelines, and predicts the noise level in the open area of a domestic cruise ship.

A hybrid approach combining Large Eddy Simulation and Lighthill Analogy is used to conduct a numerical simulation of the pipeline’s aeroacoustic noise under the actual working conditions of a cruise ship. The impacts of the inlet flow rate, outlet pressure, cross-section shape and bending angle on the aerodynamic noise are studied. A real-size cruise ship chimney exhaust pipeline model is then established to analyze the main noise sources and predict the noise level in the open areaa.

The results show that the larger the inlet velocity and bending angle, the greater the aeroacoustic noise. Furthermore, the aeroacoustic noise of a pipeline with a zero pressure-outlet is greater than that with a non-zero pressure-outlet. It is also found that the aeroacoustic noise of a rectangular cross-sectional pipeline is marginally smaller than that of a circular one. In addition, the narrowband peak frequency decreases as the bending angle increases. Except for the chimney outlet, the noise level in the open area is low.

This study has significant reference value for controlling the aeroacoustic noise of cruise ship chimney exhaust pipelines and improving passenger comfort in open areas.

The open area of the superstructure of a luxury cruise ship has a complex spatial layout and appearance modeling. In this study, the wind load and flow field characteristics in this area are accurately simulated to guide cruise ship design.

The realizable k−ε turbulence model and substructure method in the Reynolds time-average method are used to numerically simulate the flow field characteristics of the whole cruise ship and the open area of the superstructure, and wind tunnel experiments are carried out for verification.

The appearance and spatial layout of the open area of the superstructure have an important impact on the flow field characteristics of the cruise ship, and the substructure simulation method can accurately simulate the flow field characteristics of the local area.

When designing cruise ships, the overall shape of the superstructure should be streamlined and the height difference and spacing between adjacent structures in the open area should not be too large. The results of this study can provide guiding references for cruise ship design.

This paper aims to study the wind-induced noise of typical rods in the open areas of cruise ships.

The numerical simulation of aerodynamic noise and wind-induced vibration noise is carried out using computational fluid dynamics (CFD) combined with the acoustic analogy method and vibro-acoustic coupling method in order to explore the generation mechanisms and characteristics of the two kinds of noise.

Under different wind speeds, the maximum frequency of aerodynamic noise is dominated by the vortex shedding frequency, while the maximum frequency of wind-induced vibration noise is dominated by the natural frequency of the structure. The aerodynamic noise of three different cross-section rods is generally greater than that of wind-induced vibration noise, and the aerodynamic noise of square rods is the greatest. Under large flexibility, when the fluctuating pressure frequency of the rod is close to the natural frequency, the wind-induced vibration noise will be close to or even exceed the aerodynamic noise.

In the design of typical rods to be applied in the open areas of cruise ships, in order to reduce wind-induced noise, circular rods should be selected, square rods should be avoided, reasonable rod sizes should be selected and the vortex shedding frequency of the rods should not be close to the natural frequency.

A large opening on the swimming pool structure of a large cruise ship reduces the carrying capacity of the deck structure. The opening reinforcement is an effective approach to improve the structural strength. However, various forms of reinforcements pose a challenge to the optimal design of opening structures.

A variable density topology optimization method is used to optimize the opening reinforcement of a swimming pool, and a new form of opening reinforcement is obtained. Next, a size optimization method is used to obtain a more reasonable distribution of plate thicknesses, thereby achieving better weight reduction.

As the results show, compared with the prototype structure, the optimized structure has an increased ultimate bearing capacity of 1.1%, maximum stress reduction of 3.3% and weight reduction of 7.0%.

The proposed optimization design method can provide a reinforcement approach for designing the deck opening structures of cruise ships.

The atrium structure is an important functional cabin in the superstructure of a large cruise ship. Atriums have a large spatial span and are always subjected to complex loads. A fast and reliable safety assessment simulation method for atrium structures is required to assist in their structural design.

Based on the Guidance for Direct Calculation of Local Structures of Cruise Ships 2021 by the China Classification Society (CCS) and the loading characteristics of atriums, a direct calculation design method is proposed in which loads on structures are equivalent to combined simplified loads in three groups, namely longitudinal bending, vertical shear and local cargo pressure.

The results of the proposed direct calculation design method of a specific atrium structure are in good agreement with the whole-ship finite element analytical results, verifying its effectiveness.

This study can provide guidance for the design process of atrium structures in large cruise ships.

As composite materials have varied internal structures, an in-depth analysis of the damage mechanisms of their component materials can provide a research foundation for the ultimate strength analysis of composite stiffened panels.

The microscopic, mesoscopic and macroscopic mechanical analyses of marine glass fiber reinforced plastic (GFRP) composite stiffened panels are carried out using a multi-scale approach. Microscopic and mesoscopic representative volume element (RVE) models of chopped strand mat (CSM) and woven roving (WR) materials are established, and the macroscopic equivalent stiffness is obtained by homogenizing the RVE models. The ABAQUS VUMAT subroutine is used to code the progressive damage evolution model of the composite materials to derive the damage evolution mechanism of the microscopic and mesoscopic models respectively. The equivalent strength of macroscopic laminates is also obtained.

The multi-scale approach can be used to accurately evaluate the macroscopic mechanical properties of composite materials, and the ultimate strength of composite stiffened panels is mainly determined by fiber bundle failure.

The obtained macroscopic material parameters can be used to calculate the ultimate strength of composite stiffened panels, while the parametric study of the mesomechanics of composite materials can provide an analysis tool for investigating the influence of material processing technology.