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Combining the strengths of Lagrangian and Eulerian descriptions, the coupled Lagrangian–Eulerian methods play an increasingly important role in various subjects. This work reviews their development and application in ocean engineering. Initially, we briefly outline the advantages and disadvantages of the Lagrangian and Eulerian descriptions and the main characteristics of the coupled Lagrangian–Eulerian approach. Then, following the developmental trajectory of these methods, the fundamental formulations and the frameworks of various approaches, including the arbitrary Lagrangian–Eulerian finite element method, the particle-in-cell method, the material point method, and the recently developed Lagrangian–Eulerian stabilized collocation method, are detailedly reviewed. In addition, the article reviews the research progress of these methods with applications in ocean hydrodynamics, focusing on free surface flows, numerical wave generation, wave overturning and breaking, interactions between waves and coastal structures, fluid-rigid body interactions, fluid–elastic body interactions, multiphase flow problems and visualization of ocean flows, etc. Furthermore, the latest research advancements in the numerical stability, accuracy, efficiency, and consistency of the coupled Lagrangian–Eulerian particle methods are reviewed; these advancements enable efficient and highly accurate simulation of complicated multiphysics problems in ocean and coastal engineering. By building on these works, the current challenges and future directions of the hybrid Lagrangian–Eulerian particle methods are summarized. [ABSTRACT FROM AUTHOR]

Hypervelocity impact (HVI) on carbon fiber reinforced plastics (CFRPs) is associated with extreme impulse response of material as well as complex characteristics of the composites. It is a challenging task to predict the physical process of CFRP-HVI problems accurately. We apply a GPU-accelerated smoothed particle hydrodynamics (SPH) method which incorporates the composite material model and the decoupled finite particle method to simulate the CFRP-HVI processes. The presented SPH model is validated by simulating the processes of aluminum spheres impacting metallic plates. The simulation results agree well with available experimental and numerical results, and the GPU parallelization technique significantly improves the simulation efficiency (350 times faster than an equivalent serial SPH model). With such computational accuracy and efficiency, the model is extended to simulate CFRP laminate impact problems, and a particle convergence analysis is performed. It is shown that the model can obtain convergent results when modeling each CFRP layer with three SPH particles in the thickness direction and correspondingly using about twenty million particles in total. The simulation can be completed within several hours, and the dominant mechanisms of the CFRP-HVI can be captured quantitatively. To further investigate the protective performance of CFRP structures, HVI on a well-known shielding structure Whipple bumper is investigated numerically. The dynamic response of the structure is well reproduced, and the results show that the CFRP pressure wall is more effective than the metallic one. These simulation results demonstrate that the presented SPH model can model the CFRP-HVI problems accurately and efficiently. [ABSTRACT FROM AUTHOR]

Vehicle wading is a complex fluid-structure interaction (FSI) problem and has attracted great attention recently from the automotive industry, especially for electric vehicles. As a meshless Lagrangian particle method, smoothed particle hydrodynamics (SPH) is one of the most suitable candidates for simulations of vehicle wading due to its inherent advantages in modeling free surface flows, splash, and moving interfaces. Nevertheless, the inevitable neighbor query for the nearest adjacent particles among the support domain leads to considerable computational cost and thus limits its application in 3D large-scale simulations. In this work, a GPU-based SPH method is developed with an adaptive spatial sort technology for simulations of vehicle wading. In addition, a fast, easy-to-implement particle generator is presented for isotropic initialization of the complex vehicle geometry with optimal interpolation properties. A comparative study of vehicle wading on a puddle between the GPU-based SPH with two pieces of commercial software is used to verify the capability of the GPU-based SPH method in terms of convergence analysis, kinematic characteristics, and computing performance. Finally, different conditions of vehicle speeds, water depths, and puddle widths are tested to investigate the vehicle wading numerically. The results demonstrate that the adaptive spatial sort technology can significantly improve the computing performance of the GPU-based SPH method and meanwhile promotes the GPU-based SPH method to be a competitive tool for the study of 3D large-scale FSI problems including vehicle wading. Some helpful findings of the critical vehicle speed, water depth as well as boundary wall effect are also reported in this work. [ABSTRACT FROM AUTHOR]

This paper presents a profound study on the formation of three typical types of defects (i.e., lack of fusion, keyholes, and gas pores) observed in selective laser melting (SLM) printed Inconel 718 samples, along with their correlations with mechanical properties of the samples. Computed tomography, scanning electron microscopy, and mechanical property tests revealed that the three types of defects fall into three stages of porosity evolution classified by recently-proposed dimensionless numbers ηm (melting efficiency) and ηv (vaporization efficiency). Meanwhile, experimental tests verified that the mechanical properties of products, such as strength and elongation, are remarkably sensitive to lack of fusion. However, these properties are slightly affected by the keyholes and gas pores. An optimal process window characterized by dimensionless numbers is realized by adjusting the processing parameters and employing different powders. This process window allows products to have relatively low defects and high mechanical performances. A quantitative relation between processing parameters, dimensionless numbers, defects, and mechanical properties is established based on these observations. This relation, along with the optimal process window, is believed to enhance the quality of SLM products of Inconel 718 alloy and can be further extended to SLM with other metal materials. [ABSTRACT FROM AUTHOR]

Free-surface flows, especially those associated with fluid-structure interactions (FSIs), pose challenging problems in numerical simulations. The authors of this work recently developed a smoothed particle element method (SPEM) to simulate FSIs. In this method, both the fluid and solid regions are initially modeled using a smoothed finite element method (S-FEM) in a Lagrangian frame, whereas the fluid regions undergoing large deformations are adaptively converted into particles and modeled with an improved smoothed particle hydrodynamics (SPH) method. This approach greatly improves computational accuracy and efficiency because of the advantages of the S-FEM in efficiently treating solid/fluid regions showing small deformations and the SPH method in effectively modeling moving interfaces. In this work, we further enhance the efficiency of the SPEM while effectively capturing local fluid information by introducing a multi-resolution technique to the SPEM and developing an effective approach to treat multi-resolution element-particle interfaces. Various numerical examples demonstrate that the multiresolution SPEM can significantly reduce the computational cost relative to the original version with a constant resolution. Moreover, the novel approach is effective in modeling various incompressible flow problems involving FSIs. [ABSTRACT FROM AUTHOR]

In this work, we propose an efficient smoothed particle hydrodynamics (SPH) method for simulating laser powder bed fusion (LPBF). The multi-physics process of LPBF, including the heat transfer and phase change with complex boundaries, is accurately resolved by a novel heat source model and a modified continuous surface force based on a corrected surface delta function. Moreover, we also develop an efficient tensile instability control algorithm for preventing the pressure oscillations. The present method is implemented in a GPU-accelerated framework, and its performance is well demonstrated by simulating the LPBF processes with both single-layer and multi-layer powder beds (with the help of surface reconstruction). The numerical results are compared well with the experimental ones which clearly verify the ability of the present method in capturing the complex physical phenomenon of LPBF. [ABSTRACT FROM AUTHOR]