Corona Discharge Velocimeter

An acoustic velocity sensor is described. It uses a small volume of ionized gas as sensing element to estimate the velocity of air particles, especially their oscillations caused by an acoustic perturbation. The generation of charged particles is performed by a negative point-to-plane discharge, the plane anode being split into two electrically insulated parts. The principle of this velocity sensor is based on the measurement of the radial deflection of the charged particles which flow between the point and the two half-planes, this deflection being caused by the motion of the air particles resulting from the acoustic field. An electroacoustic model of this velocity sensor is proposed, based on the fluctuations of the current density distribution over the plane electrodes. An experimental set-up is developed using a waveguide. It allows to compare simultaneously the acoustic velocity deduced from the corona discharge sensor on one side, and that resulting from the two-microphone method on the other side. This paper also proposes a parametric study to quantify the influence of the electrical and geometrical parameters of the discharge on this acoustic sensor.