Numerical study on hydrodynamics of high-speed water entry in random wave environments for full-scale supercavitating vehicles

ABSTRACT Numerous studies have been conducted to enhance the performance of offshore jacket platform (OJP) using tuned mass damper (TMD) by primarily increasing only its mass ratio. Due to its substantial mass and significant space requirement, it becomes not only uneconomical but also poses challenges for practical implementation. This can be overcome by using tuned mass inerter (TMDI) device, which enhances the efficiency of the device with reduced mass due to its mass amplification effect. This study performs optimization of OJP subjected to random wave loads using TMDI utilizing genetic algorithm. Moreover, uncertainties in the system parameters may significantly alterthe structural responses and reducesafety. Thus, deterministic optimization alone is insuffiient. Hence, this study further investigates the reliability-based optimization of the same using support vector regression-assisted Monte Carlo simulation technique. Significant improvement in response and reliability of the OJP is noticed using TMDI compared to only TMD system.

Coastal salt marsh plants protect shorelines from erosion and damage by dampening incoming waves. Scholars at home and abroad have studied the wave attenuation characteristics of ideal vegetation by using a series of mathematical models and physical model experiments with comparative research methods, taking into account relevant wave conditions, plant parameters, and other factors, which has important ecological and environmental value. Furthermore, the introduction of dimensionless parameters such as Ursell number, Reynolds number, and KC number in standard fluid conditions is significant for evaluating wave dissipation by different vegetation and explaining the hydrodynamic characteristics of plant-induced wave attenuation. However, the hydrodynamic conditions and vegetation considered in existing model studies still have certain limitations. Taking into account wave breaking, random wave conditions, and more refined flexible vegetation simulations will be the main focus of future research.

Convergence zone (CZ) propagation is characterized by a small number of eigenrays, each with one deep ocean turning point and no more than two upper ocean turning points. Because of this geometry, these rays undergo a small amount of random internal wave scattering relative to the CZ range of ∼ 60 km. It is hypothesized that CZ multipath will therefore be correlated over limited observation intervals. The theory of wave propagation in random media is applied to CZ propagation through a Garrett-Munk internal wave field to predict the correlation between CZ eigenrays at mid-frequency over a finite observation interval. The theoretical results predict correlated multipath over intervals between 100 and 200 s. This prediction is then compared to data collected during an experiment in the Philippine Sea. The complex amplitudes of multipath arrivals in the CZ from 5.5 kHz sinusoidal transmissions are estimated using beamforming with a vertical line array and seen to be significantly correlated over approximately 27 s.

To investigate the dynamic response patterns of basalt-fiber-reinforced concrete slabs under random wave loads, this study characterized wave characteristics based on the random wave theory. Numerical simulations of wave loads were conducted using the Morrison equation, and an analytical model for basalt-fiber-reinforced concrete slabs was established. The research systematically examined the influence mechanisms of two key factors-effective wave period and incident angle-on the dynamic properties of such components. The results indicate that when the effective wave period increases from 7 s to 11 s, the peak displacement, peak stress, peak strain, and stress in the basalt-fiber reinforcement of the slab decrease by 12.79 mm, 0.93 MPa, 130 με, and 229.25 MPa, respectively. The growth rate of the component's dynamic response first increases and then decreases as the effective wave period shortens. When the wave incidence angle increased from 18° to 90°, the peak displacement, peak stress, peak strain, and stress in the basalt-fiber reinforcement of the concrete slab increased by 17.87 mm, 1.32 MPa, 155 με, and 297.97 MPa, respectively. The growth rate of the component's dynamic response exhibited a continuous increase with the increasing wave incidence angle. At an incidence angle of 18°, the values of the aforementioned four indicators were 576%, 213%, 52.5%, and 46% higher than those under the 90° condition, respectively. The findings of this study provide theoretical support and data references for elucidating the dynamic response patterns of basalt-fiber-reinforced concrete-slab structures under varying wave-loading conditions and for conducting fatigue performance research.

Abstract Myriad random phenomena in nature possess fractal and Hurst characteristics. Random processes/fields, such as those with Cauchy or Dagum correlations, enable modeling such stochastic structures in time and space. In the first place, this paper provides a compact review of these models, including their spectral properties, for wide ranges of the fractal dimension and Hurst parameter. The Cauchy and Dagum models can be used to determine stochastic responses of dynamical systems and/or spatial problems in 1d, 2d, or 3d in the presence of fractal and Hurst characteristics. The paper surveys various examples ranging from vibration problems, rods and beams with random properties under random loadings, waves and wavefronts, fracture, homogenization of random media, and statistical turbulence, to stochastically evolving spontaneous violations of the entropy inequality in granular flows. The latter case shows the route to examine whether a mechanical system gives rise to stochastics with such intriguing features. Common features brought out in this survey show what can and how can be achieved with Cauchy and Dagum-type models and related constructs in mechanics.

Abstract We report the experimental measurement of the density of states (DOS) associated with the soliton gas emerging during the development of the noise-induced modulation instability (MI) in optical fibres. By employing a time-lens-based heterodyne detection technique (SEAHORSE), we reconstruct the complex optical field and compute its nonlinear discrete spectrum within the framework of the inverse scattering transform. Our results show that, at early stages of the MI, the DOS matches the Weyl distribution predicted for an ‘ideal’ critically dense soliton gas, thereby confirming the relevance of the SG description for this nonlinear random wave regime. At larger effective propagation distances, we observe a progressive deformation of the DOS in the complex plane. We compare these observations with numerical simulations of a generalised nonlinear Schrödinger equation that includes losses, third-order dispersion and stimulated Raman scattering (SRS). Our simulations reproduce the main experimental trends and demonstrate that SRS is the dominant mechanism responsible for the spectral deformation. These findings highlight the need to extend the kinetic theory of soliton gas beyond purely integrable evolutions. In particular, our results call for a generalised kinetic equation (or generalised hydrodynamics description) that accounts for weak non-integrable perturbations such as SRS.

We present a novel approach to handle open boundary conditions for a Boussinesq-type wave model coupled with the nonlinear shallow water equations. Traditional methods for managing open boundaries — such as sponge layers and source functions — are computationally intensive and require ad hoc calibration. To address this, we reformulate the Boussinesq equations as a system of conservation laws with nonlocal flux and a rapidly decaying source term. This reformulation is adapted to generate waves at the boundary of the numerical domain, from surface elevation data in situations where both incoming and outgoing waves are present. The proposed numerical scheme employs a MacCormack prediction–correction strategy combined with finite volume and finite difference methods, preserving key physical properties and ensuring stability. Comparison with laboratory experiments demonstrates that our approach avoids boundary reflection issues. In particular, it is able to accurately reproduce infragravity waves associated with a random wave field propagating over a sloping beach. This work opens important perspectives for improving phase-resolving coastal wave models, with the aim of forecasting complex random wave conditions in natural environments. • Wave generation and absorption is hard to manage in Boussinesq-type models. • Sponge layers and source function methods are computationally costly and need tuning. • We propose a rigorous, efficient boundary treatment with no calibration required. • Comparisons with experiments show accurate handling of incoming and outgoing waves.

• The seabed proximity effects on the tunnel installation in random waves is experimentally investigated. • The noteworthy disparity in the dynamics of tunnel-barge system between the regular and irregular waves is highlighted. • The off-seabed clearance of the TE is governed by the coupled roll resonance superposed with the near-seabed effect. • The near-seabed effect contributes to an impressive growth in the total suspension tension and the barge mooring tension. During the near-seabed installation, the hydrodynamic responses of the submerged tunnel element and its installation system sustain prominent wall effect, which would introduce detrimental risks of grounding accidents and alignment errors. To provide a complementary insight of the wall effect and entitle for the practical engineering demands, the 1:60 scale 3D wave basin experiment is implemented to capture the full 18-DOF coupled dynamics of the tunnel-barge system under random waves, which lacks of thorough investigation in previous studies. Spatial effects like asymmetric wave loading and multi-body movements in beam waves are highlighted in both time domain and frequency domain. To the authors’ knowledge, this study is the first to systematically investigate near-seabed effects of three-dimensional multi-body system under random waves, capturing low-frequency resonance and multi-peak responses that are absent in regular wave tests. It is found that the off-seabed clearance of the TE is predominantly affected by the superposition of the coupled roll resonance and the near-seabed effect. Furthermore, the near-seabed effect contributes to a favorable diminish in the maximum single suspension tension but an impressive growth in the total suspension tension and the barge’s mooring tension.

Under random wave loading, the crack growth rate exhibits jump-like cycle-to-cycle variations, which limit the direct use of efficient integration schemes such as the Euler method. In addition, the crack growth life is highly sensitive to the initial crack size and aspect ratio, while the initial defects are often difficult to determine accurately in practice, leading to increased uncertainty in life assessment. To address these issues, a cycle-scaling-based crack size accumulation method for random loading is proposed. A predictor–corrector improved Euler method is then established, and a fourth-order Runge–Kutta scheme incorporating the cycle-scaling transformation is derived. Furthermore, based on spectral analysis theory, a mapping between the wave spectrum and the crack-tip stress intensity factor response spectrum is developed. A stress intensity factor range sequence is generated by concatenating short-term sea states, thereby providing a random loading input that preserves the required statistical characteristics. Finally, a 21,000-TEU container ship is analyzed as a case study to investigate crack growth evolution for different initial aspect ratios. The results show that the crack aspect ratio gradually converges to a particular trend during propagation. A convergent aspect ratio curve is fitted. And a unified life assessment curve is constructed. An equivalent transformation is used to map an arbitrary initial crack shape and size to an equivalent convergent aspect ratio crack. As a result, fatigue life can be rapidly estimated using a single “initial crack size–fatigue life” curve, providing support for crack growth life assessment and the definition of defect acceptance limits for ship hull structures.

Instantaneous Noise-Based Logic (INBL) presents a classical noise-based computing framework as an alternative to quantum computation, though some logic gates remain unimplemented for achieving universality over superpositions. INBL encodes M noise-bits using 2M orthogonal stochastic reference noises to construct a 2 M -dimensional product-based Hilbert space (hyperspace). Vectors in this hyperspace correspond to products of reference noises representing bit values in M-bit binary strings. This work introduces INBL implementations of XOR and XNOR operations targeting specific bits, facilitating pairwise operations directly between strings of equal length or hyperspace vectors, which are the longest strings. These operations naturally extend to superpositions, potentially delivering significant improvements in computational speed and hardware complexity. Diverging from previous methods by Khreishah et al., our approach avoids direct manipulation of the reference noise system, enabling more flexible and general-purpose implementations. We validate INBL operations—including NOT, XOR, and XNOR—through simulation using random telegraph waves, demonstrating practical feasibility without explicit reference noise manipulation.

In actual marine environments, significant nonlinear changes occur during wave propagation toward the nearshore, resulting in noticeable wave asymmetry. This leads to substantial differences in seabed response and liquefaction compared to conditions under linear waves. This study employs numerical simulations to investigate the liquefaction depth of the seabed under nonlinear wave loading. Building upon existing liquefaction prediction formulas, a more widely applicable seabed liquefaction prediction formula is derived through dimensional analysis and the least squares method. The proposed formula provides a better fit to the numerically simulated values and significantly reduces prediction errors. Based on waveform analysis, a parametric method is established. By integrating the liquefaction prediction formula, this method allows rapid estimation of the maximum seabed liquefaction depth on a sloped beach under random wave action. The calculated results show that the prediction formula closely matches the numerical simulation results.

Dynamic response of a three-span continuous RC bridge under random waves using an experiment-based method to calculate the slamming force from wave-breaking effect

Model-free forecasting of rogue waves using Reservoir Computing

• Dynamic intermittency in the wave-induced motion of planing hulls is introduced and observed in numerical simulation. • Dynamic intermittency emerges in random wave fields formed by the superposition of multiple modes, highlighting the role of nonlinear body hydrodynamic mechanisms in generating extreme responses. • Heave and pitch intermittency are observed to increase monotonically with vessel speed and wave steepness. • Pitch intermittency, while influenced by speed and wave steepness, appears to be less significant compared to heave intermittency. • A planing hull with a lower deadrise angle experiences a greater level of intermittency in both heave and pitch responses. This paper introduces the concept of dynamic intermittency into engineering-based naval architectural analysis of wave-induced motion of high-speed marine vehicles. The intermittency of wave-induced motions is used to quantify the influence of nonlinearity on deviations in the dynamic response statistics caused by the random wave field from Gaussian behaviour. Planing hulls, known for their highly nonlinear motion and broad application in coastal operations, are selected as the test case. It is hypothesised that their dynamic responses may exhibit dynamic intermittency. To test this, a high-order structure-function is introduced to quantify intermittency numerically. Three distinct planing hulls are simulated in unidirectional random wave fields, and both heave and pitch intermittency are observed. It is demonstrated that resolving timescales shorter than 10 % of the encounter period permits capturing the non-Gaussian behavior of the heave and pitch responses. The intermittency results show that intermittency in heave motion increases with vessel speed and wave steepness. This observed trend is attributed to the greater level of nonlinearity of body hydrodynamics, which becomes more pronounced as these parameters change. Pitch intermittency is also observed and is found to increase with both speed and wave steepness, although it is observed to be less significant than heave intermittency. A comparison of heave and pitch intermittency across different hull forms reveals that a planing surface with a lower deadrise angle exhibits greater intermittency in both heave and pitch responses. The observations presented in this paper demonstrate the importance of considering intermittency when analysing the dynamic responses of high-speed marine vehicles. Hence, it can be concluded that dynamic intermittency has potential applications in the design of safer vessels and ride control systems, and may also contribute to ensuring structural integrity.

Amphibious aircraft are seaplanes fitted with dual floats attached to the fuselage, allowing for landing and take-offs on aquatic surfaces. This research presents a method for evaluating the structural integrity of amphibious aircraft subjected to stochastic wave load stimulation through a probabilistic framework. The wave loads on the aircraft are assessed using the panel approach in a time domain simulation with ANSYS AQWA. Aircraft operations are simulated under three wave height: 0.5 m, 1.0 m, and 1.5 m, with three variations in relative wave direction: 90̊, 180̊, and 0̊, within a wave frequency range of up to 2 rad/s. The simulation of the floater model attempts to predict the vertical bending moment experienced by the structure; this value is subsequently utilized as input in static load modelling through the finite element method to determine the maximum stress value. A probabilistic approach was employed to account for the stochastic characteristics of wave loads, with all potential loads represented as a probability density function (PDF). Moreover, the structural reliability evaluation, which ascertains the likelihood of structural failure, was estimated by combining the load PDF with the strength PDF, derived from CEVL material testing. The evaluation results indicate that the probability of structural failure is -0.34, -0.23 and -0.029 for wave heights of 0.5 m, 1.0 m, and 1,5 m, respectively. The reliability of the floater structure might be enhanced by diminishing the stress induced by wave loads by reinforcement of floater’s longitudinal structure and/or the fortification of the CEVL material.

This paper presents a methodology for determining the wave surface profile and the velocity components of water particles from the wave spectrum of a random sea state to calculate the loads acting on the buoy. For the calculation of mooring lines with attached weights under random loads, the finite element method (FEM) is applied. The parameters of the governing dynamic equations are identified, the Newmark method is used for time integration, and a computational program is developed. The program is verified by comparing the results of the static problem with the dynamic problem under constant loading, demonstrating the correctness of the algorithm and computation. The program is then applied to calculate mooring lines with attached weights for an actual navigational buoy subjected to wind, current, and random wave loads, demonstrating the practical applicability of the proposed approach.

This paper presents a methodology for determining the wave surface profile and the velocity components of water particles from the wave spectrum of a random sea state to calculate the loads acting on the buoy. For the calculation of mooring lines with attached weights under random loads, the finite element method (FEM) is applied. The parameters of the governing dynamic equations are identified, the Newmark method is used for time integration, and a computational program is developed. The program is verified by comparing the results of the static problem with the dynamic problem under constant loading, demonstrating the correctness of the algorithm and computation. The program is then applied to calculate mooring lines with attached weights for an actual navigational buoy subjected to wind, current, and random wave loads, demonstrating the practical applicability of the proposed approach.

Reverberation chamber (RC) is a new testing environment in the field of electromagnetic compatibility measurement. Compared with the traditional testing environments, the RC has obvious advantages in improving testing efficiency and generating high E-field strength with relatively low input power. However, there are inconsistent problems in the test results of the radiation sensitivity threshold of the equipment in the reverberation chamber and the uniform field environment obtained by using the test methods in the current standards. Therefore, studying the equivalence of radiation sensitivity thresholds between the two has become a hot issue at present. Since most frequency-using devices in the electromagnetic environment can be equivalent to an antenna, in this paper, the dipole antenna under the compound field of the boundary deformation reverberation chamber and the uniform field of the anechoic chamber (AC) is taken as the research object to study the equivalence of antenna coupling power under these two conditions. Firstly, the coupling models in the anechoic chamber and reverberation chamber environments were established. The formulas for the antenna coupling power and the spatial radiation field strength under different radiation conditions were derived, and the power correlation coefficients of the two under the same sensitivity threshold were obtained. Subsequently, the electromagnetic environment of the reverberation chamber was constructed by using the Monte Carlo method, and the influence law of random plane waves with different column numbers on the coupling power of the antenna was simulated and analyzed. Finally, the equivalence factor of the coupling power of the two when the threshold of the radiation sensitivity test is the same in the reverberation chamber and the anechoic chamber is obtained.

Hydrodynamic interactions between multi-body aquaculture platforms and nearshore random wave dynamics: A physical experiment