大气压空气纳秒脉冲等离子体气动激励特性数值模拟与实验验证

Numerical Simulation and Experimental Validation of Pulsed Nanosecond Plasma Aerodynamic Actuation in Air Under Atmospheric Pressure

从机理出发,建立了考虑15种粒子和42个反应的二维等离子物理-化学模型,采用3段变步长方法,计算了纳秒时间尺度上等离子体放电特性与微秒、毫秒和秒时间尺度上流场的温度、压力与速度响应,并利用伏安特性、综合成像高速摄像机(ICCD)与粒子成像测速(PIV)实验对模型进行验证。结果表明:纳秒脉冲等离子体放电可以形成速率高达1.8×1010 K/s的局部快速温升,热源最强位置在上极板后端点;局部能量快速注入可引发压力场强扰动,形成以上极板后端点位置为中心且呈不均匀分布的压缩波和紧随其后的膨胀波,强压力扰动波形成初始阶段以当地声速快速传播,但很快即衰减为弱扰动波;压力扰动后的局部高温诱导局部流场形成涡结构,涡内流体平均速度为0.3m/s。仿真和实验结果均显示,施加重频纳秒脉冲激励时,局部诱导涡与宏观热对流效果相叠加,使流体响应呈先垂直向上、再稳定斜向右上射流的规律。

This paper presents a plasma kinetic model considering 15 species and 42 reactions. Discharge characteristics in timescale of ns and fluid response in μs, ms and s are investigated using a timestep adjusting technique. The results agree with voltage-current characteristics, intensified charge-coupled device （IOOD） and particle image velocimetry （PIV） experi- ments. Simulation results show that nanosecond discharge will lead to a rise of temperature at the rate of 1.8 × 10-10 K/s, with the hottest heating spot located at the back end of the upper electrode. The fast heating effect will result in a strong pressure perturbation and form an asymmetric perturbation wave spreading at the speed of sound. The strong wave will soon decay into a weak perturbation. The high temperature resulting from the pressure perturbation wave will induce vortexes in the local flow field with the highest velocity of 0.3 m/s in the vortexes. With repetitive nanosecond actuation being applied, the fluid will flow vertically first and then form a stable jet pointing to the top right direction due to the coupling effect of heat- ing convection and induced vortexes, which is validated by experiments.