Electrostatic Probe Measurements in Argon Plasma Boundary Layer

Abstract

A combined experimental and numerical investigation was conducted in a partially ionized boundary layer flow on a flat plate. The experiments were carried out in a low-density plasma wind tunnel, with argon as the test gas at the local freestream Mach number of 4.4. A cylindrical Langmuir probe was used to measure the ion number density and the electron temperature in the boundary layer. The effect of flush probe size, bias and flow properties were examined. Numerical calculations were made by using the charged species conservation and electron energy equations in the quasineutral region of the boundary layer, except for a thin plasma sheath. Numerical profiles of the ion number density and the electron temperature agreed fairly well with the experimental results. Also, ambipolar diffusion fluxes theoretically predicted agreed very well with the flush probe ion saturation current measured by a flush probe.