摘要
本文对声激发控制边界层转捩问题在低湍流风洞中进行了实验研究。展向一排九只小发声器装在表面带小孔的平板模型内。用液晶膜技术显示边界层状态,根据表面热膜信号确定强迫边界层转捩所需输入发声器的最小功率(转捩阈值)。实验结果表明:边界层转捩位置可以用内声激发扰动控制。能迫使层流边界层转捩的声扰动频率范围远比模型试验的Tollmien-Schlichting波频率范围宽。转捩阈值出现最小值的有利输入频率与发声器本身的频率特性有关。应用低脉冲比的声扰动对控制边界层转捩更为有效。多发声器之间的相互干扰对转捩阈值的影响大多数情况下是有利的,然而实验中也发现有声扰动相互抵消的不利情况。
An experimental investigation of a controllable artificial transition by means of internal acoustic excitation was carried out in flat-plate boundary layers. An array of nine small acoustic generators was flush mounted with the model surface.The functional application of acoustic generators was demonstrated qualitatively by flow visualization applying the liquid-crystal-foil technique. The dependence of input frequency and pulse ratio of the acoustic generators on the transition threshold values were determined with surface hot films.The experiments successfully indicated that the transition location of laminar boundary layer can be controlled by internal acoustic excitation with an appropriate input power in a frequency range which is far beyond the Tollmien-Schlichting wave range.It was found that the optimum input frequencies at which the transition threshold values are minimal and closely associated with the frequency characteristic of the acoustic generator itself.The acoustic disturbances with lower input pulse ratio are optimal for artificial transition.The transition threshold value is decreased with the decrease of pulse ratio for a constant input frequency .The effect of multi-acoustic generator interaction on the transition threshold values are positive in most of the cases. However, a negative effect was also observed in the interaction process because a partial cancellation of the forcing disturbances produced by different acoustic generators might occur.
出处
《空气动力学学报》
CSCD
北大核心
1992年第3期305-311,共7页
Acta Aerodynamica Sinica
关键词
边界层转捩
声激励
转捩阈值
boundary layer transition, acoustic excitation, TS wave. threshold value.
