基于狭缝合成射流的湍流边界层流动控制实验研究

湍流边界层主动流动控制减阻是当下一个热门的研究领域。为了探究狭缝合成射流对平板湍流边界 层流动控制的减阻效果,分别在有无合成射流干扰的条件下利用恒温式热线风速仪测量湍流边界层的流向速 度,根据测量结果得到时均速度型、脉动速度型、偏斜因子、平坦因子,并进行对比分析;选取不同频率和强度组 合的典型合成射流激励条件,研究激励条件带来的减阻效果沿流向的变化。结果表明:受控湍流边界层减阻效 果、施加的合成射流特性和当地站位到狭缝的距离均有关;合成射流在靠近狭缝位置引起湍流边界层表面摩擦 阻力增加;远离狭缝,合成射流产生减阻效果,随流向距离增加,减阻效果先增强后减弱;高频合成射流比低频 合成射流减阻效果更强;脉动速度的功率谱密度和自相关性分析表明合成射流的作用效果沿流向逐渐减弱。

An Experimental Study of Turbulent Boundary Layer Flow Control by Synthetic Jet through Spanwise Slot

In order to explore the effect of the synthetic jet through a spanwise slot on the friction drag reduction of the turbulent boundary layer of a flat plate, the streamwise velocity were measured by a constant temperature hot-wire anemometer with and without synthetic jet. According to the measured experiment data, the mean velocity profiles, fluctuating velocity profiles, skewness and flatness were obtained respectively. Typical combinations of different frequencies and intensities of synthetic jet were selected to study the variation of the forcing effect in the streamwise direction. The experimental results showed that the skin friction drag reduction in the turbulent boundary layer was related to the characteristics of the imposed synthetic jet and the distance between the local station and the slot. The synthetic jet led to an increase of the skin friction drag in the station close to the slot, and as the flow moved downstream away from the slot, a reduction in the skin friction occurred with the tendency of firstly increasing and then decreasing. The reduction of skin friction caused by the synthetic jet of a higher frequency was more than that of a lower frequency. The power spectral density and autocorrelation of the fluctuating velocities indicated that the effect of the synthetic jet on the turbulent boundary layer decayed in the streamwise direction.