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The structure of a muzzle brake has a significant effect on the overall technical performance of an automatic weapon. This paper presents a multi-objective optimization of a muzzle brake that enhances the overall performance, that is, it increases the muzzle brake efficiency and simultaneously decreases the noise emanating from the rifle upon discharge. A standard impact-reaction muzzle brake was selected as the research object. The optimal values of four structural parameters were established through multi-objective optimization. The process consists of design of experiments, coupled computational fluid dynamics and computational acoustics calculations, an approximation model, and a multi-objective genetic algorithm. Based on the results, the correlation and sensitivity between the structural parameters and the objectives were investigated. Moreover, the reaction force and noise directivity of the optimized muzzle brake were compared with those of the original design. The results show that the disk angle of the side holes was the most sensitive design variable for both efficiency and noise. The optimized muzzle brake had a remarkable improvement in brake efficiency accompanied by only a small increase in the sound pressure level, so it showed better overall performance. The optimization method proposed in this paper is practical and effective for engineering design. [ABSTRACT FROM AUTHOR]

The installation of muzzle brake changes the flow direction of propellant gas, which leads to a decline in the recoil force but an increase in the muzzle flow noise of the side rear. Therefore, the coordination between high efficiency and low harm of muzzle brake is one of the factors limiting its optimization. To address this problem, a numerical method for evaluating the comprehensive performance of muzzle brake targeting muzzle brake efficiency and impulse noise is proposed in the present study. The two performance indexes are calculated using a computational fluid dynamics (CFD)-computational aeroacoustics (CAA) coupled method. Afterwards, a corresponding experiment is conducted to verify its feasibility. Furthermore, the comprehensive performance of muzzle brakes with three different structures are analysed based on the two indexes obtained by the proposed numerical method. The results reveal that both indexes can be influenced by the structure of muzzle brakes. The increased braking efficiency is almost accompanied by increased impulse noise, but the functional relation is not linear dependence. Thus, the comprehensive performance can be improved by optimization of the structure. The evaluation method proposed in this paper has theoretical significance for optimizing muzzle brakes, which is of great engineering value. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) simulation is a core component of wind engineering assessment for urban planning and architecture. CFD simulations require clean and low-complexity models. Existing modeling methods rely on static data from geographic information systems along with manual efforts. They are extraordinarily time-consuming and have difficulties accurately incorporating the up-to-date information of a target area into the flow model. This paper proposes an automated simulation framework with superior modeling efficiency and accuracy. The framework adopts aerial point clouds and an integrated two-dimensional and three-dimensional (3D) deep learning technique, with four operational modules: data acquisition and preprocessing, point cloud segmentation based on deep learning, geometric 3D reconstruction, and CFD simulation. The advantages of the framework are demonstrated through a case study of a local area in Shenzhen, China. [ABSTRACT FROM AUTHOR]

Highlights • Multi-physical CFD model is developed by considering Seebeck effect. • Thermoelectric currents and thermoelectric-magnetic effects during MSLBW are calculated. • The influence of TECs on weld pool dynamics is characterized. • Simulation data is validated by experimentally determined seam morphologies. Abstract Thermoelectric currents (TECs) caused by Seebeck effect were usually neglected in welding simulation. This paper characterizes the TECs and thermoelectric-magnetic phenomena during the magnetically supported laser beam welding (MSLBW) of thick aluminum (Al) alloy. The simulation is based on a computational fluid dynamic (CFD) model developed in three dimensions. The model considers multi-physical mechanisms including thermal transfer, solid–liquid (S/L) transition, molten metal convection, magnetohydrodynamics (MHD) and Seebeck effect. The computed TEC distribution in laser welding pool highly depends on welding time and temperature gradient. The large current densities occur near the weld pool edge and the vectors are opposite at both side of S/L interface. The maximum TEC density obtained in the stabilized weld pool is 2.14 × 106 A/m2, leading to a self-induced magnetic field of 2.27 × 10−3 T and a Lorentz force of 2.62 × 103 N/m3. The influences of TECs on weld pool dynamics are quite limited in LBW but notable in MSLBW. The inversion of MF direction leads to different Lorentz force distributions, weld pool dimensions and seam profiles. The simulation data agrees well with the experimental results. [ABSTRACT FROM AUTHOR]