A small collapsible common-axis dual-rotor drone has been designed independently by performance indicators. The model was computed through three-dimensional modeling and meshing. Using Fluent software, the wind tunnel test simulation of the blades was obtained, and the results of the blade model test were compared with the results of the blade model. The lift data of CFD at different speeds were consistent with the results of the paddle model test, with a maximum error of only 12.46%. Using the mesh Boltzmann method (LBM) based on smooth particle theory, the non-normal aerodynamic strain of the most severe conditions in the flat flight is selected for modeling analysis. The aerodynamic layout design of a type of coaxial twin-rotor aircraft and its nonlinear six-degree-of-freedom flight simulation modeling and control system were verified. The results show that the design of the common-axis twin-rotor aircraft can meet the higher aerodynamic index requirements. The control performance and wind disturbance resistance of the designed aircraft are tested and verified by the flight simulation of Matlab/Simulink, and the simulation results show that the system can achieve the desired control goal by adding the closed-loop altitude controller and speed controller. It also provide a basis for further study of its aerodynamic properties.

According to the randomness of the spatial distribution and shape of the internal cells of closed-cell foam aluminum and based on the Voronoi algorithm, we use ABAQUS to model the random polyhedrons of pore cells firstly. Then, the algorithm of generating aluminum foam with random pore size and random wall thickness is written by Python and Fortran, and the mesh model of random polyhedral particles and random wall thickness was established by the algorithm read in by TrueGrid software. Finally, the mesh model is impo rted into the LS-DYNA software to remove the random polyhedron part of the pore cell. Compared with the results of scanning electron microscopy and antiknock test, the morphology and properties of the model are close to those of the real aluminum foam material, and the coincidence degree is more than 91.4%. By means of numerical simulation, the mechanism of the wall deformation, destruction of closed-cell aluminum foams, and the rapid attenuation of explosion stress wave after the interference of reflection and transmission of bubbles were studied and revealed. It is found that aluminum foam deformation can be divided into four areas: collapse area, fracture area, plastic deformation area, and elastic deformation region. Therefore, the explosion resistance is directly related to the cell wall thickness and bubble size, and there is an optimal porosity rule for aluminum foam antiknock performance.

Foam aluminum is an energy-absorbing material with excellent performance. The interlayer composed of multiple layers of foam aluminum and steel plate has good antiexplosion ability. In order to explore the antiexplosion performance of double-layer foam aluminum under different porosity rankings and to reveal its microscopic deformation law and failure mechanism, three kinds of aluminum foams with a porosity of 80%, 85%, and 90% were selected to form six different structures. Based on the Voronoi algorithm, a three-dimensional foam aluminum generation algorithm with random pore size and random wall thickness was written by using the Python language and Fortran language. The three-dimensional mesoscopic model of double-layer closed-cell aluminum foam sandwich panel is established by using LS-DYNA and ABAQUS software. The explosion process was simulated, and the flow field movement of explosion shock wave of aluminum foam under different porosity rankings was analyzed. Two groups of aluminum foam were randomly selected for the explosion test and compared for the strain and compression. The test results are consistent with the simulation results, which verifies the correctness of the three-dimensional meso-model. The results show that when the porosity of the upper layer of aluminum foam is greater than that of the lower layer of aluminum foam, the sandwich structure of double-layer aluminum foam has a large compression and the bottom plate has a small displacement; it is not that the greater the compression amount of aluminum foam is, the better the antiexplosion and wave absorption ability is. When the aluminum foam reaches the ultimate load-bearing capacity, the aluminum foam transfers the load due to compaction, resulting in stress enhancement phenomena. Through the analysis of the compression amount, floor deformation, wave dissipation capacity, and energy ratio of aluminum foam, it is concluded that the antiexplosion wave absorption effect of the sandwich structure of aluminum foam with 80%/85% group is the best; the changes of porosity and cell wall are important factors affecting the energy absorption capacity of aluminum foam.

In this article, based on the real shape of gravel particles, a random polyhedron model is established, and a three-dimensional (3D) finite element (FE) analysis method is proposed to study the wave dissipation of broken gravel. In this article, the generation algorithm of 3D gravel with random size and shape is proposed, and the 3D meso-model of gravel particles is established. The numerical simulation of air explosion of explosive in free field is carried out by using LS-DYNA software, and the sensitivity of grid size was verified. Finally, it is concluded that the meshing calculation result of 0.01m element is more reliable. In order to verify the effectiveness of the analysis method, the numerical results are compared with the limited experimental data, and a good agreement is obtained, which shows that the 3D mesoscopic model and the numerical analysis method of gravel particle system can reliably predict the propagation of shock wave in gravel. Then, the wave dissipation performance of gravel layer under three working conditions of no water, partial water and all water is explored, and the dynamic response, energy analysis and meso-deformation of gravel particles are studied by numerical simulation. It is concluded that the gravel particle system significantly weakens the shock wave, and the peak pressure attenuates exponentially in the velocity direction, and the existence of water will affect the attenuation ability of the explosion wave.

In the article titled “Explosion Resistance of Three-Dimensional Mesoscopic Model of Complex Closed-Cell Aluminum Foam Sandwich Structure Based on Random Generation Algorithm” [1], there was an error in Figures 1(c) and 2 due to the incorrect version of the code being used. The authors confirm that this does not affect the results and conclusions of the article, and the corrected Figures 1(c) and 2 are as follows: