The Euler equation is one of the fundamental equations describing fluid motion in Computational Fluid Dynamics, and the existence of discontinuous solutions poses challenges in constructing numerical algorithms for solving this type of equation. To achieve high-resolution numerical results for the Riemann problem of the two-dimensional Euler equation, this paper constructs a pressure-difference adaptive rotating entropy stable scheme. Utilizing the rotating invariance of the equations, the normal vector outside the boundary is decomposed into two orthogonal components, and an entropy stable scheme is implemented in each directions. The determination of the components of the two components relies on the rotation angle. In this paper, a pressure function is introduced to adaptively adjust the rotation angle of the scheme based on local pressure variations. The resolution of the entropy stable scheme is enhanced by introducing the adaptive rotation angle. Numerical examples show that the numerical results obtained by this scheme exhibit good symmetry and high resolution.

Accurately simulating the impact characteristics of a dam break is of paramount significance for the prediction and mitigation of dam-break flow disasters. The B-spline material point method (BSMPM), as an improved algorithm of the material point method (MPM), effectively enhances computational accuracy and improves convergence. However, the BSMPM solves the governing equations based on a tensor grid rather than an Eulerian background grid. Moreover, its interpolation shape functions have a larger influence domain. Consequently, when solving problems involving fluid-structure coupling and contact, issues such as premature contact, difficulty in capturing contact interfaces, and challenges in calculating contact forces arise. Within the same tensor grid space of the BSMPM, accurate capture of contact interfaces is achieved based on the relative velocities and unit outward normals of the same nodes; employing the Greville Abscissa enables precise contact of contacting objects, thereby avoiding premature or spurious contact; through the Lagrange multiplier method, interface contact forces are accurately determined, thus constructing a high-precision contact algorithm for fluid-structure strongly coupled problems, facilitating research on the simulation of dam-break fluid impact with rigid and elastic obstacles, and enabling a comparison with existing experimental or simulated results. The results demonstrate that the simulated impact loads and structural deformation evolution patterns correspond well with existing experimental/simulated results. For rigid obstacles, the peak impact pressure exhibits concave parabolic growth and positive correlation exponential function growth with increasing water level and dam-break slope, respectively. For elastic obstacles, the peak impact pressure decreases exponentially with the increase in the height of the probing point. The feasibility and effectiveness of simulating dam-break flow impact problems using the BSMPM contact algorithm are validated, providing a new perspective for simulating dam-break flow impact problems.

Structural condition assessment is crucial for ensuring the safe services of structures, with structural damage detection (SDD) being a core component. In this paper, a novel SDD method is proposed based on the adaptive grasshopper algorithm and sparse regularization. It aims to tackle accuracy decline of SDD results and instability involving uncertainties and incomplete measurement, thereby achieving sparse-regularization-based structural condition assessment. Firstly, adaptive Lévy flight and elite opposition-based learning strategies are incorporated into the adaptive grasshopper algorithm to prevent the SDD process from falling into local optima and to enhance the stability of SDD results. Secondly, a modal parameter-based objective function with sparse regularization is formulated to increase the sparsity of SDD results, thereby improving SDD accuracy and robustness. The optimization results of competition-based evolutionary computation benchmark functions show that the adaptive grasshopper algorithm exhibits better global convergence and identification stability compared with its standard version. Numerical and experimental results for simply-supported beams indicate that the proposed method can ensure reliable SDD accuracy even in the case of incomplete measurements, and it possesses good noise robustness as well.

Research on acoustic propagation in multiple fluids has important application values in naval architecture and ocean engineering, such as sound propagation in pipelines filled with water and air, and the detection of buried objects. There are two difficulties in solving such problems with the use of the classical finite element method: one is the serious numerical dispersion error in the finite element solutions under medium and high wave numbers; the other is the need to use refined mesh grids to discretize the fluids near the coupling interface. These difficulties lead to a large computational cost for the finite element method, and the manual intervention to generate refined grids. Compared with the finite element method, the weak-form meshfree method does not require traditional grids, and the dispersion error effect in its solution is much weaker, ensuring good computational accuracy and efficiency. However, the meshfree shape functions are usually discontinuous in the problem domain, resulting in the inability of the continuity condition of the acoustic particle velocity to be naturally satisfied on the interface. Therefore, this paper uses the penalty function method to reconstruct the continuity condition of the acoustic particle velocity on the interface, and proposes a Galerkin weak form suitable for meshfree methods for sound propagation in multiple fluids. Numerical analysis shows that the meshfree solutions is consistent with the reference solutions, and the computational accuracy and efficiency of the meshfree method can be higher than the finite element solutions.

The discontinuous Galerkin (DG) method has been widely adopted due to its excellent properties such as high accuracy and ease of parallelization. The adaptive mesh refinement (AMR) technique has been widely adopted to improve computational efficiency with much less computational cost compared with uniform global refinement to the same level with AMR. This paper combines the advantages of DG and AMR, and a new hybrid limiter is applied to the DG method on adaptive Cartesian grid based on p4est, an open-source library. The limiter exhibits advantages of high precision, compactness, robustness, and ease of implementation. The shock wave is captured with a shock indictor and the performance of the new hybrid limiter is compared with that of the total variational bounded (TVB) limiter in this paper. The result shows that the performance of the former is significantly better than that of the latter. A series of numerical examples for Euler equations and Navier-Stokes equations are used to verify the feasibility and efficiency of the proposed method. The results show that the new hybrid limiter performs very well in the AMRDG method, it has lower dissipation and great shock capture ability, and the computational efficiency is greatly improved while the accuracy is guaranteed.

Damage and fracture are the main causes of structural failure, which have a significant impact on engineering safety. Crack propagation problem is also a fundamental scientific challenge that needs to be solved urgently. In this paper, the relevant theoretical basis for simulating damage and fracture, such as a fracture mechanics model, damage evolution model and numerical calculation methods, such as the finite element method, boundary element method and peridynamics theory, are introduced in the form of literature review. This paper also reviews the commonly used CAE software for structural damage and fracture analysis, including general-purpose finite element programs such as the damage and fracture analysis module that comes with ABAQUS, as well as specialized fracture analysis software, damage tolerance tools, fatigue life analysis tools, etc. The development status of some autonomous CAE software is also discussed. Finally, this paper analyzes some challenges faced by CAE software for damage and fracture simulation, and looks forward to the future development direction of domestic CAE software.

The formation of porous media is influenced by a number of factors, including the deposition and fragmentation of particles, which result in the formation of interlayers with varying structures. These interlayers exert a significant influence on the mechanical behavior of porous media. This paper presents a systematic investigation into the influence of the inclination angle and thickness of the interlayer on the mechanical behavior of porous media, employing the discrete element method. The results demonstrate that the stress intensity of porous media containing interlayers is between those of the two homogeneous porous media and varies with changes in the inclination angle and thickness of the interlayers. The average coordination number between grains is found to be significantly affected by the thickness of the interlayer at the beginning of loading, but stabilized at the end of loading. The variation of the coordination number affects the distribution of strong and weak force chains, while the inclination angle and thickness of the interlayer determine the magnitude and direction of stress transfer in the force chains. Furthermore, the contact unit normal force and normal contact force are deflected with the increase of the inclination angle of the interlayer, demonstrating significant anisotropy. This study advances our understanding of the intricate mechanical behavior of porous media containing interlayers in strata, offering invaluable insights for optimization and practical application in geological engineering.

Accurately constructing the nonlinear hysteresis loop model at the bolt connection is crucial for the vibration reduction and safety performance evaluation of a satellite load-carrying structure. Traditional time-domain analysis methods of computational models require substantial time costs, and typical data-driven models struggle to construct high-precision hysteresis models. To address these challenges, a novel Residual Improvement Deep Learning Algorithm (RIDLA) is proposed for constructing the hysteresis loop model of displacement and force at the bolt connection. The algorithm fully leverages the capacity of Long Short-Term Memory (LSTM) neural networks to fit nonlinear relationships in time series. It adopts an innovative approach by creating a multi-level residual improvement deep learning model that iteratively refines predictions based on measured responses, resulting in highly accurate modeling of hysteresis at bolt connections. The performance of the RIDLA method is validated using experimental data from cyclic loading of a subcomponent of a satellite load carrying structure. The findings demonstrate that RIDLA achieves highly accurate predictions of the displacement and force hysteresis loop at the bolt connection. Additionally, the RIDLA method could be applied to predict the dynamic responses of other complex non-linear systems.

This paper presents a Bezier triangle meshing method that considers both clipped and non-clipped forms for a single NURBS surface. The proposed method is applied to analyze isogeometric Kirchhoff-Love shell structures. The process begins by interpolating NURBS surfaces into Bezier surfaces. Subsequently, the topological relationship between the clipping curve and each parameter node is calculated within the parameter domain. A Bezier contour curve set is then generated in the parameter domain by selecting points along the clipping curve. Utilizing this contour curve set, a triangular mesh is generated in the parameter domain. Finally, the Bezier triangle mesh in the physical domain is created through a mapping method. The adaptability and robustness of the algorithm are verified through three models, and the mesh quality is assessed. The results demonstrate favorable overall mesh quality. Building upon this foundation, the paper illustrates the application of a rotation constraint between Kirchhoff-Love shell elements, using the penalty function method with Scordelis-Lo's Roof shell model as an example. The accuracy of Kirchhoff-Love shell elements based on Bezier triangles is subsequently validated.

Proppant transport in fractures is essentially a dense granular flow in a slot-shaped space. Applying the two-fluid method in numerical simulations of a field-scale particle flow is promising, but existing solid stress models cannot accurately describe the process of proppant accumulation. In this paper, the morphological change of a proppant pack under flow erosion was analyzed experimentally, and the important influence of cohesion on the change of the pack state was pointed out. Then, combined with the simulated results of a proppant transport and the results of a suspension apparent viscosity test, the influence of the particle radial distribution function on the solid kinetic pressure and the change trend of total solid pressure were analyzed, and the change rate of the solid friction pressure with the particle volume fraction was determined. Based on the granular matter theory and results of a direct shear test, the cohesion of the proppant pack was considered in the frictional viscosity model. The results show that the improved solid friction stress model can capture larger angles of the accumulation and settlement profiles, and correctly simulate the process of proppant accumulation.