Temporal variation of the spatial density distribution above a nanosecond pulsed dielectric barrier discharge plasma actuator in quiescent air

Abstract

The thermal perturbation caused by a nanosecond pulsed dielectric barrier discharge (ns-DBD) plasma actuator may lead to boundary layer transition. Hence, understanding of the thermal flow induced by the ns-DBD plasma actuator will contribute to the development of an efficient flow control device for various engineering applications. In this study, the spatial density distribution related to the thermal flow was experimentally investigated using both qualitative and quantitative schlieren techniques. The focus of this study is to understand the initial temporal variation of the spatial density distribution above the ns-DBD plasma actuator in quiescent air. The quantitative visualisation showed that a hot plume is generated from the edge of the exposed electrode and moves slightly towards the ground electrode. A possible explanation is that an ionic wind and/or an induced jet leads to the movement of the hot plume. However, the plasma-induced flow (the ionic wind and the induced jet) is generated after the primary plasma discharges; namely, the hot plume does not move immediately after the first plasma discharge. At almost the same time as the movement of the hot plume, consecutive plasma discharges enhance the density of the hot plume; thereafter, the density reaches almost a steady state.

Thermal Fluctuation Characteristics around a Nanosecond Pulsed Dielectric Barrier Discharge Plasma Actuator using a Frequency Analysis based on Schlieren Images

“…The high temperature induces a hot plume, but the hot plume is not clearly visualised after the first plasma discharge even though Schlieren sensitivity is high. After 1 ms time elapsed (Figure 5c), the hot plume grows and is visible because the hot plume moves due to natural convection as well as a very weak ionic wind [21]. The grown hot plume is diffused to a surrounding air, and then a thermal perturbation gradually disappears when the longer interval time between the first and second plasma discharges (Figure 5d,e).…”

“…In Case 4 (Figure 8c, BR = 0.45), a wave thermal pattern appears above the ground electrode. According to an experimental investigation by Ukai et al [21], the hot plume moves towards the ground electrode due to a very weak ionic wind. Similarly, in the present results, the hot plume grows towards the ground electrode at the elapsed time of Δt = 50 ms (Figure 5g, Figure 8).…”

“…The ns-DBD plasma actuator generates very low-speed ionic wind [12]; however, an instant heated gas is generated due to the rapid temperature increase. Ukai et al [21] experimentally investigated the quantitative density field around the ns-DBD plasma actuator excited by 12 kV at 1 kHz, using a calibrated Schlieren technique and showed that the gas density ratio divided by a room density ρ ∞ is approximately ρ/ρ ∞ = 0.95 after the induced-thermal flow became stable. On the other hand, the ac-DBD plasma actuator produced relatively weak gas density ratio of approximately ρ/ρ ∞ = 0.978 [22].…”

“…The actuator was made using the process of double-sided photolithography. The detailed manufacturing procedure is presented in a reference [21]. The plasma actuator was put in a quadrilateral stainless steel chamber with a volume of 0.138 m 3 .…”

Наносекундная Ионизация Области Обтекания Прямоугольного Уступа Высокоскоростным Потоком

“…Ее конфигурация и интенсивность зависят от локализации разряда, структуры газового потока и распределения плотности в зоне локализации разряда. Поверхностные разряды могут быть использованы для управления пограничным слоем [4,5], включая зоны отрыва пограничного слоя на обтекаемой поверхности. Особое внимание уделяется управлению отрывом при обтекании уступов [6,7].…”