Numerical simulation of welding aerosol motion characteristics based on turbulence-Brownian effect

In order to explore the motion trajectory and diffusion distribution of aerosol particles in manual welding arc, a mathematical model of welding aerosol particle diffusion coupled with momentum and energy of plasma, hot air and particles is established according to aerosol dynamics, plasma flow mechanics and computational fluid dynamics, combined with turbulent flow and particle Brownian effect. The influences of electrode inclination angle and particle size on the movement characteristics, horizontal and vertical distribution of welding aerosol are investigated by numerical simulation. The results show that the electrode inclination angle has a great impact on the initial position distribution and motion trajectory of welding particles. The area where the particles are generated will be offset away from the electrode tilt, and this offset increases as the decrease of angle between the electrode and the plane. In the free diffusion process of welding submicron aerosol particles, the diffusion distribution of particles is closely related to the particle size. For small particles, especially for ultra-fine particles of 0.1 μm, under the action of Brownian force, the horizontal distance origin moment of particles is more than 75 mm, while for larger particles with a particle size of more than 0.5 μm, the horizontal distance origin moment is less than 15 mm. It indicates that the particles with smaller size have stronger dispersion and wider distribution. Due to the effect of molecular slip, the drag effect of airflow on ultra-fine particles decreases, and the movement trajectory of particles with smaller size is more likely to deviate from the direction of airflow.