Development and numerical investigation of Mach probe model in a hypersonic, low-temperature flowing plasma

Abstract

This study conducted a numerical simulation around a Mach probe under hypersonic low-temperature plasma. The Mach probe has three ion collection planes: front, side, and back. Under a hypersonic flowing plasma, the front and side planes are practical ion collection areas, and the backplane collects no ion flux. The collected ion current density on the front plane is almost identical to that of the mainstream ion flux. By contrast, the ion current collected on the side plane is affected by the concentration of the electric field at the probe edge. As this edge effect has a different influence on the front and side planes, the ion current density ratio of the side to the front planes is dominated by a non-dimensional parameter—the ratio of electrostatic to kinetic flow energy. Based on this non-dimensional parameter, the calculated ion current density ratio can be fitted using a simple mathematical formula. Therefore, the proposed Mach probe model with non-dimensional parameters extends the conventional Mach probe model validated in sub-to-supersonic high-temperature plasma to hypersonic low-temperature flowing plasma, which is commonly observed in electric propulsions.