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Purpose This study aims to evaluate blast loads on and the response of submerged structures. Design/methodology/approach An arbitrary Lagrangian–Eulerian method is developed to model fluid–structure interaction (FSI) problems of close-in underwater explosions (UNDEX). The “fluid” part provides the loads for the structure considers air, water and high explosive materials. The spatial discretization for the fluid domain is performed with a second-order vertex-based finite volume scheme with a tangent of hyperbola interface capturing technique. The temporal discretization is based on explicit Runge–Kutta methods. The structure is described by a large-deformation Lagrangian formulation and discretized via finite elements. First, one-dimensional test cases are given to show that the numerical method is free of mesh movement effects. Thereafter, three-dimensional FSI problems of close-in UNDEX are studied. Finally, the computation of UNDEX near a ship compartment is performed. Findings The difference in the flow mechanisms between rigid targets and deforming targets is quantified and evaluated. Research limitations/implications Cavitation is modeled only approximately and may require further refinement/modeling. Practical implications The results demonstrate that the proposed numerical method is accurate, robust and versatile for practical use. Social implications Better design of naval infrastructure [such as bridges, ports, etc.]. Originality/value To the best of the authors’ knowledge, this study has been conducted for the first time.

The flexible ribbon can be used as a projectile stabilizing device to provide a stable moment for the projectile, and the research on its drag characteristics is of great significance. This paper uses the arbitrary Lagrange-Euler (ALE) method to simulate the fluid-structure interaction process of the ribbon swinging in the airflow. The numerical method is validated by comparing it with wind tunnel experimental results from previous literature. This study utilized numerical simulation to investigate the impact of inflow velocity, ribbon material properties, and ribbon shape on drag characteristics. The research concluded that for a single ribbon, the drag value increases as the incoming flow velocity, ribbon material density, elastic modulus, and length-width ratio increase. In addition, the drag value of the annular ribbon is greater than that of the double ribbon. The drag values of the double ribbon and the annular ribbon are averaged to one side, the unilateral drag of the annular ribbon is greater than that of the single ribbon, and the unilateral drag of the double ribbon is smaller than that of the single ribbon. The conclusions can provide a reference for studying flexible ribbon stabilized projectiles.

Given the documented wave-induced damage of elevated coastal decks during extreme natural hazards (e.g., hurricanes) in the last two decades, it is of utmost significance to decipher the wave-structure-interaction of complex deck geometries and quantify the associated loads. Therefore, this study focuses on the assessment of solitary wave impact on open-girder decks that allow the air to escape from the sides. To this end, an arbitrary Lagrangian-Eulerian (ALE) numerical method with a multi-phase compressible formulation is used for the development of three-dimensional hydrodynamic models, which are validated against a large-scale experimental dataset of a coastal deck. Using the validated model as a baseline, a parametric investigation of different deck geometries with a varying number of girders Ng and three different widths, was conducted. The results reveal that the Ng of a superstructure has a complex role and that for small wave heights the horizontal and uplift forces increase with the Ng, while for large waves the opposite happens. If the Ng is small the wave particles accelerate after the initial impact on the offshore girder leading to a more violent slamming on the onshore part of the deck and larger pressures and forces, however, if Ng is large then unsynchronized eddies are formed in each chamber, which dissipate energy and apply out-of-phase pressures that result in multiple but weaker impacts on the deck. The decomposition of the total loads into slamming and quasi-static components, reveals surprisingly consistent trends for all the simulated waves, which facilitates the development of predictive load equations. These new equations, which are a function of Ng and are limited by the ratio of the wavelength to the deck width, provide more accurate predictions than existing empirical methods, and are expected to be useful to both engineers and researchers working towards the development of resilient coastal infrastructure.

This paper presents a study of a 63-m-high (206 feet) RC building’s failure under blast loading and subsequent column removals. The analysis covers the entire process, starting with explosive charge detonation and ending in demolition. LS-DYNA software was used for blast wave propagation and structural interaction, while SAP2000 modeled successive column removal, both focused on columns experiencing the highest loads at the bottom, using nonlinear dynamic analysis (NDA). Three explicit methods—Load blast enhanced (LBE), Arbitrary lagrangian eulerian (ALE), and Coupling—were discussed for their suitability. The LBE method, though time-efficient, faces challenges in limiting affected surface or volume. ALE confines explosive energy to designated columns and the Coupling method emerges as the most appropriate, combining ALE for initial detonation and LBE for subsequent implosion. The research distinguishes itself by exploring a novel method for safely monitoring building demolition. By employing stationary cameras positioned outside the critical collapse area and utilizing Tracker software, it segments footage into frames, tracks point displacement in each frame, and compares the results with real values, providing a comprehensive analysis. Moreover, the study’s examination aligns with the actual demolition, offering insights by comparing simulation results with photographs of real damage, thereby validating the procedure. The findings show explicit analysis aligns closely with real data, while SAP2000 NDA exhibits relatively distant results, although being more time-efficient. The article also explores alternative demolition scenarios, sequentially removing three column groups from the same structure. To deepen the analysis, scenarios were created by varying the time intervals between column removals. Decreasing time intervals resulted in improved alignment between the outcomes of both programs. The global issue of buildings reaching the end of their service life and the 2023 seismic events in Turkiye have highlighted the urgent need to analyze numerical methods for the demolition of hundreds of thousands of structures with specific focus.

With the growing requirements for multi-particle process simulation, improving computational accuracy, efficiency, and scalability has become a critical challenge. This study generally focused on comprehensive analyses of existing numerical methods for simulating particle–substrate interactions in gas–thermal spraying (including gas–dynamic spraying processes), covering both single-particle and multi-particle models to develop practical recommendations for the optimization of modern coating spraying processes. First of all, this paper systematically analyzes the key limitations of current approaches, including their inability to handle high deformations effectively or high computational complexity and their insufficient accuracy in dynamic scenarios. A comparative evaluation of four numerical methods (Lagrangian, Arbitrary Lagrangian–Eulerian (ALE), Coupled Eulerian–Lagrangian (CEL), and Smoothed Particle Hydrodynamics (SPH)) revealed their strengths and weaknesses in modeling of real gas–thermal spraying processes. Furthermore, this study identifies the limitations of the widely used Johnson–Cook (JC) constitutive model under extreme conditions. The authors considered the Zerilli–Armstrong (ZA), Mechanical Threshold Stress (MTS), and Preston–Tonks–Wallace (PTW) models as more realistic alternatives to the Jonson–Cook model. Finally, comparative analyses of theoretical and realistic deformation and defect-generation processes in gas–thermal coatings emphasize the critical need for fundamental changes in the simulation strategy for modern gas–thermal spraying processes.

A numerical model incorporating the phase field method, the arbitrary Lagrangian-Eulerian (ALE) method, the effective heat capacity model and the Navier-Stokes equations is established to solve the complex force-mass-heat coupling transport during the process of a particle impacting a high-temperature melt pool. Then, a study of the particle-melt pool interaction mechanism is carried out, the dominant factors that influence the particle capture behaviour explored, and the effects of contact angle and particle velocity on particle melting further analysed. Results show that a decaying particle oscillation phenomenon and a periodical surface meniscus structure appear during the process of a particle impacting a melt pool. As for particle melting, it is far delayed behind particle oscillation and mainly takes place at the static heat transfer stage; its heat accumulation is dominated by the particle's mushy degree, and becomes gentle after the particle becomes totally mushy. However, the particle's melting speed is determined by surface heating; the dominant melting factor converts to laser irradiation with increasing laser energy density; it changes to melt pool heating as the particle velocity increases and the contact angle decreases. Furthermore, when the contact angle decreases, the optimized initial velocity region broadens, and the best initial velocity gradually reduces. Highlights of the article are as follows: a single particle impacting a high-temperature melt pool model incorporating the coupling of the phase field and ALE methods is developed. Further, a dominant particle melting comparison map under various laser parameters is made. Dominant particle melting converts to melt pool heating as the initial velocity increases and the equilibrium contact angle decreases. The optimization of the initial particle velocity region broadens and the best initial velocity reduces to zero as the equilibrium contact angle decreases.

In this work, we present a study of fluid–structure interaction using a numerical tool based on the spectral method (SM) coupled with the asymptotic numerical method (ANM). The studied structure is a non-deformed cylindrical tube of boundaries Γ c . This tube can move along the x -axis. It is maintained along the y -axis by a linearly elastic spring. The fluid occupies a volume Ω f of boundary Γ f . A velocity u imp is imposed on this boundary. The difficulty with this example is that the cylinder is in motion and is constantly changing the Ω f fluid domain. To overcome this difficulty, we use an arbitrary Lagrange–Euler formulation in which the displacement velocity of mesh is equal to that of the cylinder on Γ c and zero on Γ f .

Recent decades have witnessed the increasing usage of deep cement mixing (DCM) mixers in the field of marine infrastructure construction. The mixing performance, including the torque history, can be helpful for structural safety evaluation, design, and the optimization of agitators, which is of engineering significance. However, to the best of the authors’ knowledge, there are no related publications that have reported the mixing behaviors of deep cement mixing agitators. In light of this, the present work conducts experimental and numerical investigations of the mixing behaviors of a DCM ship mixing agitator. To achieve this end, a model test device is established, and mixing experiments using two- and three-blade mixers are respectively conducted. Silt and clay soils are considered in the experiments with a three-blade mixer, while clay soils are used for those with a two-blade mixer. In addition, this work designs a torque transducer placed inside the rotating rod to accurately measure the torque history of the agitator during model test experiments. The experimental results show that, when mixing clay using agitators with different blades, the average torque value required for a two-blade agitator is slightly larger than that for a three-blade one. This study also presents a computational framework based on the arbitrary Lagrangian–Eulerian (ALE) method for an efficient and accurate modeling of the soil-mixing behaviors of the agitator. The numerical results are found to be in good agreement with the experimental data from model tests in terms of torque history, which demonstrates the effectiveness and capacity of our presented computational framework. The numerical results show that the average torque value is smaller at a higher rotational speed during the mixing of clay using a two-bladed agitator, but the effect of rotational speed on the torque history is small. The experimental and numerical methods introduced in the present work can act as a useful tool for investigations of mixing behaviors of DCM agitators.

An asteroid impact can potentially destroy life on this planet. Therefore, asteroids should be prevented from impacting the Earth to impede severe disasters. Nuclear explosions are currently the only option to prevent an incoming asteroid impact when the asteroid is large or the warning time is short. However, asteroids exist in an absolute vacuum, where the explosion energy propagation mechanism differs from that in an air environment. It is difficult to describe this process using standard numerical simulation methods. In this study, we used the single-material arbitrary Lagrangian–Eulerian (ALE) method and the finite element-smoothed particle hydrodynamics (FE-SPH) adaptive method to simulate the process of deflecting hazardous asteroids using penetrating explosions. The single-material ALE method can demonstrate the expansion process of explosion products and energy coupling in absolute vacuum. The FE-SPH adaptive method can transform failed elements into SPH particles during the simulation, avoiding system mass loss, energy loss, and element distortion. We analyzed the shock initiation and explosion damage process and obtained an effective simulation of the damage evolution, stress propagation, and fragment distribution of the asteroid. In addition, we decoupled the penetrating explosion into two processes: kinetic impact and static explosion at the impact crater. The corresponding asteroid damage modes, velocity changes, and fragmentation degrees were simulated and compared. Finally, the high efficiency of the nuclear explosion was confirmed by comparing the contribution rates of the kinetic impact and nuclear explosion in the penetrating explosion scheme.

Purpose During thermal laser processes, heat transfer and fluid flow in the melt pool are primary driven by complex physical phenomena that take place at liquid/vapor interface. Hence, the choice and setting of front description methods must be done carefully. Therefore, the purpose of this paper is to investigate to what extent front description methods may bias physical representativeness of numerical models of laser powder bed fusion (LPBF) process at melt pool scale. Design/methodology/approach Two multiphysical LPBF models are confronted: a Level-Set (LS) front capturing model based on a C++ code and a front tracking model, developed with COMSOL Multiphysics® and based on Arbitrary Lagrangian–Eulerian (ALE) method. To do so, two minimal test cases of increasing complexity are defined. They are simplified to the largest degree, but they integrate multiphysics phenomena that are still relevant to LPBF process. Findings LS and ALE methods provide very similar descriptions of thermo-hydrodynamic phenomena that occur during LPBF, providing LS interface thickness is correctly calibrated and laser heat source is implemented with a modified continuum surface force formulation. With these calibrations, thermal predictions are identical. However, the velocity field in the LS model is systematically underestimated compared to the ALE approach, but the consequences on the predicted melt pool dimensions are minor. Originality/value This study fulfils the need for comprehensive methodology bases for modeling and calibrating multiphysical models of LPBF at melt pool scale. This paper also provides with reference data that may be used by any researcher willing to verify their own numerical method.