Numerical Modeling of an Impinging Jet Flow inside a Thermal Cut Kerf Using CFD and Schlieren Method

Abstract

The dynamics of high-pressure gas flow injected through a nozzle during a thermal cutting process has an important effect on cutting performance. In this study, an actual gas flow condition inside a cut kerf of a plasma cut sample was simulated by considering various geometric features of the cut kerf, such as kerf width difference and cutting length difference between the top and bottom surfaces. A prototype cut kerf shape was fabricated using a transparent material. A gas flow shadowgraph from inside the fabricated cut kerf was observed using the Schlieren method. In addition, image processing was performed on images obtained with the Schlieren method before and after gas injection, which were used to validate the numerical simulation models. The effect of turbulent viscosity in various turbulent models was studied using computational fluid dynamics analyses. The results confirmed that the k–ω turbulent model was the most suitable turbulent model for the geometry used in this study. The simulation results for this model were qualitatively consistent with the reported experimental measurements.

Keywords

• plasma arc cutting
• laser cutting
• Schlieren method
• CFD
• turbulence model
• image processing