To investigate the evolution of dimpling and the mechanism of interface separation in bimetal clad pipes under external mechanical loading, a stress model was established. The study analyzed the effects of the ratio of diameter to thickness for the inner and outer pipes, forming pressure, initial forming clearance, and operational internal pressure on dent formation and interface separation. Results indicate that interface separation distance and rebound rate correlate positively with the ratio of diameter to thickness for the inner pipes, forming pressure, and initial forming clearance, and negatively with the ratio of diameter to thickness for the outer pipes. Higher operational internal pressure reduces interface separation but increases rebound rate. Internal pressurization of dented pipes decreases interface separation; for instance, under 2-MPa operating pressure, interface separation is 5% less compared with conditions under 2-MPa pressurization. Additionally, the difference in separation between these conditions decreases with increasing pressure. Adjacent dimpling results in increased interface separation in intermediate pipe segments, causing a broader interface separation area compared with isolated dimpling.

The non-isothermal complex flow caused by fluid impacting obstacles is very important to the industrial processes such as nuclear energy utilization. Through coupling various numerical techniques such as the density diffusive term, artificial viscous term, particle shifting technique, a stable and accurate non-isothermal smoothed particle hydrodynamics (SPH) scheme is established, and accurate simulation of non-isothermal complex flow caused by fluid impacting obstacles is realized. Based on the simulation for the non-isothermal flow past a heated cylinder, the non-isothermal dam break past single/multiple obstacles, it is demonstrated that: (1) the developed non-isothermal SPH scheme can not only compute a smooth pressure field and avoid the spurious oscillation of numerical solutions, but also predict accurately the temperature field and the key physical quantities; (2) this SPH scheme can also accurately show the interaction between the heat conduction process and the complex free-surface evolution, and has the capability to simulate non-isothermal complex flows past multiple obstacles.

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.

In computational fluid dynamics, mesh quality greatly affects the accuracy and computational efficiency of numerical simulation results. The Bubble does not require the consideration of intersection judgments and has a relatively simple data structure, which has significant advantages in mesh generation efficiency and quality. The process of improving the mesh quality by moving nodes based on the traditional Bubble is optimized in this article, and we define it as the Bubble-Opt method. In this method, a bubble radius selection method combined with neural networks is used to generate the initial bubbles, and an improved bubble dynamic movement technique is used to adjust the bubbles to the appropriate position. The Delaunay method is used to connect the center of bubbles to form the final optimized mesh. Then, the optimization effects of different bubble radius selection methods and Bubble-Opt methods are compared under different process parameters. Taking the flow around a 2D cylinder as an example, the geometric quality and transition ratio of the mesh before and after optimization are tested. For this example, there is a set of optimal parameters and a radius selection method that achieve the best mesh quality optimization effect. The average transition ratio can be improved by about 17.37%, the average mesh quality can be improved by about 13.60%, and the minimum transition ratio and minimum mesh quality can be significantly improved. Finally, under the radius selection method and process parameters, taking two-dimensional cylindrical flow and NACA0012 airfoil flow as examples, the numerical simulation results are compared with experimental data from both qualitative and quantitative perspectives, indicating a significant improvement in the overall grid quality.

The computation mechanism of the calculation method for the completed state of existing suspension bridges is unclear, and the target state is unreasonable. A reasonable numerical analysis algorithm is proposed for bridge formation state. The cable theory consisting of the initial end angle and horizontal cable force is validated based on the relationship between the initial end angle and cable force in the theory of catenary equations. A system of bridge state analytical equations are constructed based on the optimization principle of the target parameters of each component of the suspension bridge. The calculation equation for the main cable configuration based on the geometric closure conditions of the suspension bridge's main cable. The mechanical equilibrium equations are constructed for each component based on the mechanical equilibrium conditions of the suspension cables and stiffening beams. Based on the principle of minimizing the bending moment of the stiffening beam components and the principle of uniform cable force of the suspension cable components in the completed state of the suspension bridge, a calculation equation system for the stiffening beam and suspension cable is established. The intelligent algorithm GRG is used to optimize the numerical solution of the objective function of the completed state of a suspension bridge. A case study of a kilometer-long level suspension bridge project. The derived analytical algorithm is compared with the calculation results of the finite element model and rigid supported continuous beam algorithm. The results show that the difference between the analytical algorithm and the finite element model calculation is relatively small in terms of force of main cable, shape-finding of main cable, and the bending moment of the stiffening beam. Compared with the rigid support continuous beam algorithm, the analytical algorithm has computational advantages in ensuring the uniformity of cable forces in bridge suspension cables and the extreme bending moment of stiffening beams.

Using fractional derivatives to modify the Zener standard rheological solid model and considering the instantaneous rheological effect of the soil around the pile, a vertical coupled vibration model of the pile-soil system is constructed. The frequency-domain analytical solution of the system dynamic control equation is derived using Laplace transform and potential function decomposition methods. The time domain response under instantaneous excitation at the pile top is obtained through numerical Laplace inversion. Then, numerical examples are used to analyze the frequency domain characteristics of displacement and dynamic stiffness, and dynamic damping of end-bearing pile vertical vibration in a rheological clay layer, as well as the wave response under instantaneous excitation at the pile top. Research has found that the rheological effect of soil reduces the amplitude of pile top displacement and dynamic stiffness and the rheological effect of soil causes a decrease in the amplitude of the pile top response and a weakening of the reflected wave signal under instantaneous excitation.